Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Water-Based Synthesis of Hydrophobic Ionic Liquids [N8888][oleate] and [P666,14][oleate] and their Bioprocess Compatibility
Raes, Sanne M.T. ; Jourdin, Ludovic ; Carlucci, Livio ; Bruinhorst, Adriaan van den; Strik, David P.B.T.B. ; Buisman, Cees J.N. - \ 2018
ChemistryOpen 7 (2018)11. - ISSN 2191-1363 - p. 878 - 884.
fatty acids - ionic liquids - microbial compatibility - toxicity - wastewater

The conversion of organic waste streams into carboxylic acids as renewable feedstocks results in relatively dilute aqueous streams. Carboxylic acids can be recovered from such streams by using liquid–liquid extraction. Hydrophobic ionic liquids (ILs) are novel extractants that can be used for carboxylic acid recovery. To integrate these ILs as in situ extractants in several biotechnological applications, the IL must be compatible with the bioprocesses. Herein the ILs [P666,14][oleate] and [N8888][oleate] were synthesized in water and their bioprocess compatibility was assessed by temporary exposure to an aqueous phase that contained methanogenic granular sludge. After transfer of the sludge into fresh medium, [P666,14][oleate]-exposed granules were completely inhibited. Granules exposed to [N8888][oleate] sustained anaerobic digestion activity, albeit moderately reduced. The IL contaminants, bromide (5–500 ppm) and oleate (10–4000 ppm), were shown not to inhibit the methanogenic conversion of acetate. [P666,14] was identified as a bioprocess-incompatible component. However, our results showed that [N8888][oleate] was bioprocess compatible and, therefore, has potential applications in bioprocesses.

A Diurnal Rhythm in Brown Adipose Tissue Causes Rapid Clearance and Combustion of Plasma Lipids at Wakening
Berg, Rosa van den; Kooijman, Sander ; Noordam, Raymond ; Ramkisoensing, Ashna ; Abreu-Vieira, Gustavo ; Tambyrajah, Lauren L. ; Dijk, Wieneke ; Ruppert, Philip ; Mol, Isabel M. ; Kramar, Barbara ; Caputo, Rosanna ; Puig, Laura Sardón ; Ruiter, Evelien M. de; Kroon, Jan ; Hoekstra, Menno ; Sluis, Ronald J. van der; Meijer, Onno C. ; Willems van Dijk, Ko ; Kerkhof, Linda W.M. van; Christodoulides, Constantinos ; Karpe, Fredrik ; Gerhart-Hines, Zachary ; Kersten, Sander ; Meijer, Johanna H. ; Coomans, Claudia P. ; Heemst, Diana van; Biermasz, Nienke R. ; Rensen, Patrick C.N. - \ 2018
Cell Reports 22 (2018)13. - ISSN 2211-1247 - p. 3521 - 3533.
angiopoietin-like 4 - APOE3-Leiden.CETP mice - brown adipose tissue - circadian rhythm - diurnal rhythm - fatty acids - lipoprotein lipase - postprandial lipid response - triglycerides
Many favorable metabolic effects have been attributed to thermogenic activity of brown adipose tissue (BAT). Yet, time of day has rarely been considered in this field of research. Here, we show that a diurnal rhythm in BAT activity regulates plasma lipid metabolism. We observed a high-amplitude rhythm in fatty acid uptake by BAT that synchronized with the light/dark cycle. Highest uptake was found at the onset of the active period, which coincided with high lipoprotein lipase expression and low angiopoietin-like 4 expression by BAT. Diurnal rhythmicity in BAT activity determined the rate at which lipids were cleared from the circulation, thereby imposing the daily rhythm in plasma lipid concentrations. In mice as well as humans, postprandial lipid excursions were nearly absent at waking. We anticipate that diurnal BAT activity is an important factor to consider when studying the therapeutic potential of promoting BAT activity. van den Berg et al. show a strong circadian rhythm in fatty acid uptake by brown adipose tissue that peaks at wakening regardless of the light exposure period. Consequently, postprandial lipid handling by brown adipose tissue is highest at wakening, resulting in the lowest postprandial plasma lipid excursions.
Socio-economic assessment of Algae-based PUFA production
Voort, Marcel van der; Spruijt, Joanneke ; Potters, Jorieke ; Wolf, Pieter de; Elissen, Hellen - \ 2017
Göttingen : PUFAChain - 84
bioenergy - biobased economy - biofuels - biomass - algae - fatty acids - bio-energie - biobrandstoffen - biomassa - algen - vetzuren
Predicting methane emission of dairy cows using milk composition
Gastelen, Sanne van - \ 2017
University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; Kasper Hettinga. - Wageningen : Wageningen University - ISBN 9789463437097 - 266
dairy cows - dairy cattle - methane production - emission - milk composition - fatty acids - cattle feeding - fermentation - nutrition physiology - animal nutrition - pollution - melkkoeien - melkvee - methaanproductie - emissie - melksamenstelling - vetzuren - rundveevoeding - fermentatie - voedingsfysiologie - diervoeding - verontreiniging

Enteric methane (CH4) is produced as a result of microbial fermentation of feed components in the gastrointestinal tract of ruminant livestock. Methane has no nutritional value for the animal and is predominately released into the environment through eructation and breath. Therefore, CH4 not only represents a greenhouse gas contributing to global warming, but also an energy loss, making enteric CH4 production one of the main targets of greenhouse gas mitigation practices for the dairy industry. Obviously, reduction of CH4 emission could be achieved by simply reducing livestock numbers. However, the global demand for dairy products has been growing rapidly and is expected to further grow in the future. Therefore, it is critical to minimize environmental impact to produce high-quality dairy products. The overall aim of this PhD research was, therefore, to develop a proxy for CH4 emission that can be measured in milk of dairy cows.

There are currently a number of potentially effective dietary CH4 mitigation practices available for the livestock sector. The results of Chapter 3 show that replacing fiber-rich grass silage with starch-rich corn silage in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed. Little is known whether host genetics may influence the CH4 emission response to changes in diet. Therefore, the interaction between host DGAT1 K232A polymorphism with dietary linseed oil supplementation was evaluated in Chapter 7. The results of Chapter 7 indicate that DGAT1 K232A polymorphism is associated with changes in milk composition, milk N efficiency, and diet metabolizability, but does not affect digestibility and enteric CH4 emission, whereas linseed oil reduces CH4 emission independent of the DGAT1 K232A polymorphism.

Accurate and repeatable measurements of CH4 emission from individual dairy cows are required to assess the efficacy of possible mitigation strategies. There are several techniques to estimate or measure enteric CH4 production of dairy cows, including climate respiration chambers, but none of these techniques are suitable for large scale precise and accurate measurements. Therefore, the potential of various metabolites in milk, including milk fatty acids (MFA), as a proxy (i.e., indicators or animal traits that are correlated with enteric CH4 production) for CH4 emission of dairy cows gained interest. Until recently, gas chromatography was the principal method used to determine the MFA profile, but this technique is unsuitable for routine analysis. This has led to the application of Fourier-transform infrared spectroscopy (FTIR) for determination of the MFA profile. Chapter 2 provides an overview of the recent research that relates MFA with CH4 emission, and discusses the opportunities and limitations of using FTIR to estimate, indirectly via MFA or directly, CH4 emission of dairy cattle. The recent literature on the relationship between MFA and CH4 emission gives inconsistent results. Where some studies found a clear and strong relation, other studies consider MFA to be unreliable predictors for CH4 emitted by dairy cows. Even the studies that do find a clear relation between MFA and CH4 emissions do not describe similar prediction models using the same MFA. These discrepancies can be the result of many factors, including dietary composition and lactation stage. Additionally, literature showed that the major advantages of using FTIR to predict CH4 emission include its simplicity and potential practical application on a large scale. Disadvantages include the inability to predict important MFA for the prediction of CH4 emission, and the moderate power of FTIR to directly predict CH4 emission. The latter was also demonstrated in Chapter 9, in which the CH4 prediction potential of MFA was compared with that of FTIR using data from 9 experiments (n = 218 individual cow observations) covering a broad range of roughage-based diets. The results indicate that MFA have a greater potential than FTIR spectra to estimate CH4 emissions, and that both techniques have potential to predict CH4 emission of dairy cows, but also limited current applicability in practice. Much focus has been placed on the relationship between MFA and CH4 emission, but milk also contains other metabolites, such as volatile and non-volatile metabolites. Currently, milk volatile metabolites have been used for tracing animal feeding systems and milk non-volatile metabolites were shown to be related to the health status of cows. In Chapter 4, the relationship between CH4 emission and both volatile and non-volatile metabolites was investigated, using data and milk samples obtained in the study described in Chapter 3. In general, the non-volatile metabolites were more closely related to CH4 emissions than the volatile metabolites. More specifically, the results indicate that CH4 intensity (g/kg fat- and protein-corrected milk; FPCM) may be related to lactose synthesis and energy metabolism in the mammary gland, as reflected by the milk non-volatile metabolites uridine diphosphate-hexose B and citrate. Methane yield (g/kg dry matter intake) on the other hand, may be related to glucogenic nutrient supply, as reflected by the milk non-volatile acetone. Based on the metabolic interpretations of these relationships, it was hypothesized that the addition of both volatile and non-volatile metabolites in a prediction model with only MFA would enhance its predictive power and, thus, leads to a better proxy in milk for enteric CH4 production of dairy cows. This was investigated in Chapter 5, again using data and milk samples described in Chapter 3. The results indicate that MFA alone have moderate to good potential to estimate CH4 emission. Furthermore, including volatile metabolites (CH4 intensity only) and non-volatile metabolites increases the CH4 emission prediction potential.

The work presented in Chapters 3, 4 and 5, was based upon a small range of diets (i.e., four roughage-based diets in which grass silage was replaced partly or fully by corn silage) of one experiment. Therefore, in Chapter 6, the relationship between CH4 emission and the milk metabolome in dairy cattle was further quantified. Data (n = 123 individual cow observations) were used encompassing a large of roughage-based diets, with different qualities and proportions of grass, grass silage and corn silage. The results show that changes in individual milk metabolite concentrations can be related to the ruminal CH4 production pathways. These relationships are most likely the result from changes in dietary composition that affect not only enteric CH4 production, but also the profile of volatile and non-volatile metabolites in milk. Overall, the results indicate that both volatile and non-volatile metabolites in milk might provide useful information and increase our understanding of CH4 emission of dairy cows. However, the development of CH4 prediction models revealed that both volatile and non-volatile metabolites in milk hold little potential to predict CH4 emissions despite the significant relationships found between individual non-volatile metabolites and CH4 emissions. Additionally, combining MFA with milk volatile metabolites and non-volatile metabolites does not improve the CH4 prediction potential relative to MFA alone. Hence, it is concluded that it is not worthwhile to determine the volatile and non-volatile metabolites in milk in order to estimate CH4 emission of dairy cows.

Overall, in comparison with FTIR, volatile and non-volatile metabolites, the MFA are the most accurate and precise proxy in milk for CH4 emission of dairy cows. However, most of MFA-based models to predict CH4 emission tend to be accurate only for the production system and the environmental conditions under which they were developed. In Chapter 8 it was demonstrated that previously developed MFA-based prediction equations did not predict CH4 emission satisfactory of dairy cows with different DGAT1 genotypes or fed diets with or without linseed oil. Therefore, the greatest shortcoming today of MFA-based CH4 prediction models is their lack of robustness. Additionally, MFA have restricted practical application, meaning that most MFA retained in the current CH4 prediction models cannot be determined routinely because of the use of gas chromatography. The MFA that can be determined with the use of infrared spectroscopy are however no promising predictors for CH4 emission. Furthermore, MFA have only a moderate CH4 prediction potential. This together suggests that it might not be the best option to focus in the future on MFA alone as a proxy for CH4 emission of dairy cows.

The FTIR technique has a low to moderate CH4 prediction potential. However, FTIR has a great potential for practical high throughput application, facilitating repeated measurements of the same cow potentially reducing random noise. Results of this thesis also demonstrated that FTIR spectra do not have the potential to detect differences in CH4 emission between diets which are, in terms of forage level and quality, commonly fed in practice. Moreover, the robustness of FTIR spectra is currently unknown. Hence, it remains to be investigated whether FTIR spectra can predict CH4 emissions from dairy cows housed under different conditions from those under which the FTIR-based prediction equations were developed. It is therefore concluded that the accuracy and precision to predict CH4 emission using FTIR needs to increase, and the capacity of FTIR to evaluate the differences in CH4 emission between dairy cows and different types of diets needs to improve, in order to actually be a valuable proxy for CH4 emission of dairy cows.

Spatio-temporal variability in the winter diet of larval and juvenile Antarctic krill, Euphausia superba, in ice-covered waters
Schaafsma, F.L. ; Kohlbach, D. ; David, C. ; Lange, B.A. ; Graeve, M. ; Flores, H. ; Franeker, J.A. van - \ 2017
Marine Ecology Progress Series 580 (2017). - ISSN 0171-8630 - p. 101 - 115.
euphausia-superba - winter - stomach contents - fatty acids - sea ice - Weddell Sea - Furcilia - Juveniles
Antarctic krill Euphausia superba is an ecological key species in the Southern Ocean and a major fisheries resource. The winter survival of age class 0 (AC0) krill is susceptible to changes in the sea-ice environment due to their association with sea ice and their need to feed during their first winter. However, our understanding of their overwintering diet and its variability is limited. We studied the spatio-temporal variability of the diet in 4 cohorts of AC0 krill in the
Northern Weddell Sea during late winter 2013 using stomach contents, fatty acids (FAs) and bulk stable isotope analysis (BSIA). Stomach contents were dominated by diatoms in numbers and occasionally contained large volumes of copepods. Many of the prey species found in the stomachs were sea ice-associated. Our results show that the diet of overwintering AC0 krill varies significantly in space and time. Variability in stomach content composition was related to environmental factors, including chlorophyll a concentration, copepod abundance and sea-ice cover. In contrast, FA composition mainly varied between cohorts, indicating variation in the long-term diet. The condition of the AC0 krill was reflected in FA and BSIA analysis, suggesting that the availability of sea ice-derived food sources over a long period may impact the condition of developing
AC0 krill significantly. The spatio-temporal availability of sea-ice resources is a potentially important factor for AC0 krill winter survival.
Baseline fatty acids, food groups, a diet score and 50-year all-cause mortality rates. An ecological analysis of the Seven Countries Study
Menotti, Alessandro ; Kromhout, Daan ; Puddu, Paolo Emilio ; Alberti-Fidanza, Adalberta ; Hollman, Peter ; Kafatos, Anthony ; Tolonen, Hanna ; Adachi, Hisashi ; Jacobs, David R. - \ 2017
Annals of medicine 49 (2017)8. - ISSN 0785-3890 - p. 718 - 727.
50-year follow-up - all-cause mortality - fatty acids - Seven Countries Study - socio-economic status
Objectives: This analysis deals with the ecologic relationships of dietary fatty acids, food groups and the Mediterranean Adequacy Index (MAI, derived from 15 food groups) with 50-year all-cause mortality rates in 16 cohorts of the Seven Countries Study. Material and methods: A dietary survey was conducted at baseline in cohorts subsamples including chemical analysis of food samples representing average consumptions. Ecologic correlations of dietary variables were computed across cohorts with 50-year all-cause mortality rates, where 97% of men had died. Results: There was a 12-year average age at death population difference between extreme cohorts. In the 1960s the average population intake of saturated (S) and trans (T) fatty acids and hard fats was high in the northern European cohorts while monounsaturated (M), polyunsaturated (P) fatty acids and vegetable oils were high in the Mediterranean areas and total fat was low in Japan. The 50-year all-cause mortality rates correlated (r= −0.51 to −0.64) ecologically inversely with the ratios M/S, (M + P)/(S + T) and vegetable foods and the ratio hard fats/vegetable oils. Adjustment for high socio-economic status strengthened (r= −0.62 to −0.77) these associations including MAI diet score. Conclusion: The protective fatty acids and vegetable oils are indicators of the low risk traditional Mediterranean style diets.KEY MESSAGESWe aimed at studying the ecologic relationships of dietary fatty acids, food groups and the Mediterranean Adequacy Index (MAI, derived from 15 food groups) with 50-year all-cause mortality rates in the Seven Countries Study.The 50-year all-cause mortality rates correlated (r = −0.51 to −0.64) ecologically inversely with the ratios M/S [monounsaturated (M) + polyunsaturated (P)]/[saturated (S) + trans (T)] fatty acids and vegetable foods and the ratio hard fats/vegetable oils. After adjustment for high socio-economic status, associations with the ratios strengthened (r = −0.62 to −0.77) including also the MAI diet score.The protective fatty acids and vegetable oils are indicators of the low risk traditional Mediterranean style diets.
Differences in transcriptional responses to acute and chronic dietary interventions with fatty acids
Matualatupauw, Juri C. - \ 2017
University. Promotor(en): Sander Kersten, co-promotor(en): Lydia Afman; J. Bouwman. - Wageningen : Wageningen University - ISBN 9789463432078 - 172
fatty acids - gene expression - genotyping - phenotypes - nutritional intervention - transcriptomics - fish oils - apolipoprotein e - adipose tissue - microarrays - polymerase chain reaction - vetzuren - genexpressie - fenotypen - maatregel op voedingsgebied - transcriptomica - visoliën - apolipoproteïne e - vetweefsel - polymerase-kettingreactie

Various types of dietary fatty acids have different effects on human health. The aim of this thesis was to increase our understanding of the molecular mechanisms underlying the effects of dietary fatty acids. To do this, we examined changes in whole genome gene expression profiles upon both acute as well as longer term dietary fatty acid interventions. Furthermore, from previous research, it is clear that large inter-individual differences in the response to dietary fatty acids exist. We used whole genome gene expression analyses to increase our understanding of the mechanisms underlying some of these inter-individual differences.

Many modifiable and non-modifiable factors can be the cause of these inter-individual differences. In chapter 2, we reviewed all studies that examined differences in the transcriptional response to dietary interventions based on the presence of one of these factors. These include gender, age, BMI, body composition, blood lipid levels and gut microbial composition. We conclude that transcriptome analyses are well-suited for studying the underlying mechanisms behind these differences in the response to diet. Nevertheless, the number of studies that use this approach remains limited.

Another factor that may modify the response to a dietary intervention is genetics, e.g. the apolipoprotein E4 (APOE4) variant. People who carry the APOE4 allele have an increased risk of cardiovascular disease. Fish-oil supplementation may help in the prevention of cardiovascular disease, though inter-individual differences in the response to n-3 polyunsaturated fatty acids on gene expression profiles have been observed. In chapter 3, we aimed to assess the impact of APOE4 on peripheral blood mononuclear cell (PBMC) whole genome gene expression at baseline and following a 6-month fish-oil intervention. We observed increased gene expression of IFN signaling and cholesterol biosynthesis pathways in APOE4 carriers, which might explain part of the association between APOE4 and CVD. Furthermore, fish-oil supplementation may be beneficial by decreasing interferon signalling-related gene expression in APOE4 carriers.

Another long-term dietary intervention with fatty acids was studied in chapter 4. We examined the effect of a 12-week high medium-chain saturated fatty acid diet on subcutaneous adipose tissue gene expression profiles. We observed increased expression of genes involved in oxidative energy metabolism and decreased inflammation-related gene expression due to the high medium-chain saturated fatty acid intake. Considering the role of the adipose tissue in sustaining the low-grade inflammation that is associated with obesity, these findings may be indicative of a more anti-inflammatory phenotype of the adipose tissue. We concluded that medium-chain saturated fatty acids may potentially have beneficial effects on adipose tissue functioning.

Besides studying the effects of long-term interventions with fatty acids on whole genome gene expression, we also examined the effects of acute high-fat challenges. In chapter 5, we determined the additional value of determining whole genome gene expression changes in response to a high-fat challenge compared to assessment at fasting only. In addition, we aimed to identify whether a 4 week high-fat high-calorie diet can induce a shift in gene expression profiles in healthy subjects towards a metabolic syndrome-like gene expression profile. We found that fasting whole blood whole genome gene expression profiles are highly responsive to a 4-week high-fat high-calorie diet, with changes in in the direction of a metabolic syndrome-like gene expression profile. High-fat challenge responses in healthy subjects show only minimal changes in gene expression upon the dietary intervention and a marginal shift in the direction of the metabolic syndrome. We concluded that fasting gene expression profiles are more responsive compared to high-fat challenge responses to a 4-week high-fat high-calorie diet.

Besides chapter 5, several other studies have also examined changes in whole genome gene expression in blood cells induced by high-fat challenges. In chapter 6, we combined microarray data from four high-fat challenge studies varying in study population, challenge composition and research laboratory. By performing this meta-analysis, we showed a general PBMC whole genome gene expression response to a high-fat challenge. We concluded that a meta-analysis provides added value for the discovery of consistently differentially expressed genes and pathways compared to selecting only those genes and pathways that are identified in all separate studies.

In conclusion, in this thesis we showed differences in the whole genome gene expression response to fish-oil supplementation in PBMCs of APOE4 carriers vs non-carriers. Furthermore, the effects on whole genome gene expression of the two long-term dietary interventions, i.e. the fish-oil supplementation in PBMCs of APOE4 carriers and the high medium-chain saturated fatty acid diet in adipose tissue, may be beneficial by downregulation of gene expression related to inflammation. We also showed that whole genome gene expression responses to high-fat challenges are affected by a 4-week high-fat high-calorie diet, though changes in fasting gene expression profiles are much more pronounced. Finally, we showed the value of meta-analysis of microarray data in high-fat challenge studies for identifying the general response to a high-fat challenge.

Assessing methane emission from dairy cows : modeling and experimental approaches on rumen microbial metabolism
Lingen, Henk J. - \ 2017
University. Promotor(en): Wouter Hendriks, co-promotor(en): Jan Dijkstra; Andre Bannink; Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789463431590 - 207
dairy cows - methane - emission - microbial degradation - rumen metabolism - rumen fermentation - models - fatty acids - biochemical pathways - animal nutrition - nutrition physiology - melkkoeien - methaan - emissie - microbiële afbraak - pensmetabolisme - pensfermentatie - modellen - vetzuren - biochemische omzettingen - diervoeding - voedingsfysiologie

Methane (CH4) is a greenhouse gas (GHG) with a global warming potential of 28 CO2 equivalents. The livestock sector was estimated to emit 7.1 gigatonnes of CO2 equivalents, which is approximately 14.5% of total global anthropogenic GHG emissions. Enteric CH4 production is the main source of GHG emissions from dairy cattle, representing 46% of the global GHG emissions in dairy supply chains. Dairy production has great value in view of the ability of ruminants to effectively turn human inedible biomass into human edible food and to produce food from non-arable land. Consequently, there is an urgent need to develop strategies to decrease dairy cattle enteric CH4 emission. Evaluation of these strategies requires meticulous quantification and increased understanding of anaerobic fermentation and methanogenesis in the rumen ecosystem. The overall aim of this PhD research was, therefore, to quantitatively evaluate enteric CH4 emission from dairy cows as affected by feeding and rumen microbial metabolism.

A meta-analysis was performed to quantify relationships between enteric CH4 yield (per unit of feed and unit of milk) and milk FA profile in dairy cattle and to develop equations to predict CH4 yield based on milk FA profile of cows fed a wide variety of diets. Various milk FA concentrations were significantly or tended to be positively or negatively related to CH4 yield per unit of feed or milk. Mixed model multiple regression resulted in various milk FA included in optimal equations to predict CH4 yield per unit of feed and per unit of milk. These regression equations indicated a moderate potential for using milk FA profile to predict CH4 yield.

For the development of a mechanistic model of CH4 production in the rumen, the thermodynamic control of pH2 on reaction rates of specific fermentation pathways, NADH oxidation and methanogenesis was theoretically explored. This control was determined using the thermodynamic potential factor (FT), which is a dimensionless factor that corrects a predicted kinetic reaction rate for the thermodynamic control exerted. The thermodynamic feasibility of these microbial conversions showed that the control of pH2 on individual VFA produced and associated yield of H2 and CH4 cannot be explained without considering NADH oxidation, with a considerable effect of pH.

For obtaining experimental support of the conclusions drawn from the theoretical exploration, diurnal patterns of gaseous and dissolved metabolite concentrations in the bovine rumen, H2 and CH4 emitted, and the rumen microbiota were monitored. In addition, the effect of dietary inclusion of linseed oil on these patterns was assessed. An in vivo experiment with rumen cannulated dairy cows was performed to study the anaerobic metabolism and the microbiota composition in the rumen. A 100-fold increase in pH2 in the rumen headspace was observed at 0.5 h after feeding, followed by a decline. Qualitatively similar patterns after feeding were observed for H2 and CH4 emission, ethanol and lactate concentrations, and propionate molar proportion, whereas an opposite pattern was seen for acetate molar proportion. Associated with these patterns, a temporal biphasic change in the microbial composition was observed as based on 16S ribosomal RNA with certain taxa specifically associated with each phase. Bacterial concentrations were affected by time and increased by linseed oil supplementation. Archaeal concentrations tended to be affected by time and were not affected by diet, despite linseed oil supplementation tending to decrease the partial pressure and emission of CH4 and tending to increase propionate molar proportion. The various diurnal profiles that were monitored support the key role of the NAD+ to NADH ratio in rumen fermentation and the importance of diurnal dynamics when understanding VFA, H2 and CH4 production.

A dynamic mechanistic model was developed, in which the thermodynamic control of pH2 on VFA fermentation pathways, and methanogenesis in the bovine rumen are incorporated. The model represents substrate degradation, microbial fermentation and methanogenesis in the rumen, with the type of VFA formed to be controlled by the NAD+ to NADH ratio, which in turn is controlled by pH2. Feed composition and feed intake rate representing a twice daily feeding regime were used as model input. The model predicted a marked peak in pH2 after feeding that rapidly declined in time. This peak in pH2 caused a decrease in NAD+ to NADH ratio followed by an increased propionate molar proportion at the expense of acetate molar proportion. In response to feeding, the model predicted a sudden increase and a steady decrease in CH4 production in time. The pattern of CH4 emission rate followed the patterns of pH2 and H2 emission rate, but its magnitude of increase in response to feeding was less pronounced. A global sensitivity analysis indicated the parameter that determines the NADH oxidation rate to explain the most substantial part of the variation of predicted daily CH4 emission. The modeling effort provides the integration of more detailed knowledge than accomplished in previous rumen fermentation models and enables assessment of diurnal dynamics of rumen metabolic pathways yielding VFA, H2 and CH4.

For assessing the general value of the research reported in this thesis, the potential for predicting enteric CH4 emission from dairy cattle based on milk FA profile was discussed in the light of published studies and compared with empirical modeling of enteric CH4 based on feed input. Moreover, the concept of NAD-controlled fermentation was considered in a more general perspective by comparing the rumen ecosystem with bioreactor systems. Furthermore, the feasibility of the developed models as an alternative for IPCC tiered approaches was explored. In conclusion, the research reported in this thesis contributes to an increased understanding of rumen fermentation and microbial metabolism, and has provides a basis to further improve prediction models of enteric CH4 emissions from dairy cattle.

Breaking down barriers: construction of a hybrid heterochiral membrane
Siliakus, Melvin - \ 2016
University. Promotor(en): John van der Oost, co-promotor(en): Servé Kengen. - Wageningen : Wageningen University - ISBN 9789462579293 - 237
membranes - engineering - escherichia coli - fatty acids - isoprenoids - archaea - thermococcus kodakarensis - polymerase chain reaction - gene knock-out - dna modification - membranen - vetzuren - isoprenoïden - polymerase-kettingreactie - inactivering van genen - dna-modificatie

Because of a chemical disparity between Archaeal and Bacterial membrane-lipids, these organisms thrive under distinct environmental conditions. Archaea are generally more resistant to extreme habitats like low pH, high temperature or presence of solvents. It has therefore long been hypothesized that the archaeal lipids provide archaeal cells with a higher robustness than bacterial lipids do for Bacteria. A recent study in which bacterial and archaeal lipids were mixed to form hybrid vesicles “lipid enclosed round structures”, for instance showed a higher temperature dependent stability than either the bacterial or archaeal lipid vesicles separately. In the present study, we therefore introduced the enzymatic machinery for assembly of archaeal lipids into the bacterium Escherichia coli. This engineering led to cells with a mixed membrane at a surprisingly high amount of 28% archaeal lipids. Although the intervention led to severe morphological malformations, the cells indeed showed an increased robustness to extreme cold and butanol.

Milk fat triacyglycerols : their variabiblity, relations with fatty acids, DGAT1, B polymorphs and melting fractions
Tzompa Sosa, D.A. - \ 2016
University. Promotor(en): Toon van Hooijdonk, co-promotor(en): Hein van Valenberg; G.A. van Aken. - Wageningen : Wageningen University - ISBN 9789462577503 - 122 p.
milk fat - triacylglycerols - fatty acids - composition - polymorphism - dairy cows - cows - crystallization - fat crystallization - melting - calorimetry - maldi-tof - thin layer chromatography - melkvet - triacylglycerolen - vetzuren - samenstelling - polymorfisme - melkkoeien - koeien - kristallisatie - vetkristallisatie - smelten - calorimetrie - dunnelaagchromatografie

Milk fat (MF) triacylglycerol composition varies within a population of dairy cows. The variability of MF triacylglycerols and their structure was partially explained by the fatty acid (FA) composition of the MF, and by DGAT1 K232A polymorphism. The FA C16:0 and C18:1cis-9 play a major role in understanding the changes seen in triacylglycerol profile and structure because they are the most abundant FAs in MF and are negatively correlated. MFs with low ratio C16:0/C18:1cis-9 were decreased in triacylglycerols with 34 and 36 carbons and were increased in triacylglycerols with 52 and 54 carbons. These changes in MF composition greatly affected the crystallization behavior of MF by changing the types of polymorphs formed during its crystallization. MF with low ratio C16:0/C18:1cis-9 formed stable and metastable polymorphs (β and β’, respectively), whereas MF with high ratio C16:0/C18:1cis-9 formed exclusively metastable polymorphs (β’) when the fat was crystallized at 20°C. The changes in MF composition also affected the melting behavior of MF by changing the melting point of the MF fractions.

Microalgae diets for landbased aquaculture of the cockle Cerastoderma edule: impacts of dietary fatty acids on growth
Reis Batista, I.C. dos - \ 2015
University. Promotor(en): Aad Smaal, co-promotor(en): Johan Kamermans; Rene Wijffels. - Wageningen : Wageningen University - ISBN 9789462575875 - 132
schaaldieren - schaal- en schelpdierenteelt - algen - voedering - voersamenstelling - diëten - vetzuren - groei - tanks - plassen - aquacultuur - shellfish - shellfish culture - algae - feeding - feed formulation - diets - fatty acids - growth - ponds - aquaculture

Land-based shellfish culture as a part of a multi-trophic aquaculture systems has yet to be implemented in Europe. Recently the pilot project Zeeuwse Tong (The Netherlands) evaluated the feasibility of a system of fish (Dover sole), ragworms, phytoplankton and bivalves. This thesis focused on the dietary fatty acids impact on growth, survival and fatty acid composition of juveniles (shell length >5mm) of the common cockle Cerastoderma edule, for land-based culture.

Dietary fatty acids were chosen as the main nutritional research subject given the existing literature indicating their importance for reproduction, and growth and survival of larvae, post-larvae, spat and seed of most bivalves. However, since grow-out of juvenile cockles in land-based aquaculture is not common, no information is available on the dietary fatty acid requirements of juveniles. To determine if the presence of specific fatty acids is more important for growth and survival of juvenile cockles than the total amount of dietary fatty acids supplied, least cost linear programming was used to design live microalgae diets. Monocultures of indigenous algae were grown under controlled conditions and sampled to determine their quality in terms of dry weight, organic matter, lipid and fatty acids composition. These differences in biochemical composition of the microalgae were used in a least-cost programming software, and allowed the formulation of three diets with different fatty acid contents, but similar dry weight, organic matter, lipid and total fatty acid content. The formulated diets were then used to determine the importance of dietary fatty acids for growth, survival and fatty acid composition of juvenile cockles (Cerastoderma edule). Juvenile cockles (6.24±0.04 mm) were constantly fed live microalgal diets with similar lipid, organic matter and total fatty acid contents but different individual fatty acid concentrations: high-EPA, no-DHA and low-ARA diets. Growth was positively affected by high-EPA and low-ARA diets, whereas no significant growth was observed for the no-DHA diet. However, high mortality of cockles fed no-DHA diet and the low absorption efficiency and clearance rate of this diet indicate that this diet is unsuitable for juvenile cockles. In balanced diets with EPA and DHA, lower concentrations of ARA did not limit growth. The combination of EPA and DHA in a live microalgae diet was beneficial for the growth and survival of juvenile cockles, but no conclusion on the importance of supplying only EPA could be made. To address this, an additional growth experiment was designed. Growth and fatty acid profiles of juveniles cockles were determined after 28 days of feeding diets:1) with EPA 2) with DHA; 3) with EPA and DHA from a mixture of a diatom with a green algae; 4) with EPA and DHA from a mixture of the two green algae and 5) without long-chain (>C20) fatty acids. Significantly higher growth rate was observed with the treatment rich in EPA, while the lowest growth rates were found in without EPA. These results indicate that EPA is necessary for the short-term growth of cockles. Moreover, the fatty acid profile of the polar lipids confirmed that, like most marine invertebrates, juvenile C. edule are not able to biosynthesize EPA and DHA from 18:3n-3 but are capable of biosynthesizing diene and triene NMI fatty acids. The occurrence of the NMI fatty acids was diet related, thus refuting the possibility of production of NMI as replacement for EPA and DHA.

Furthermore, in order to develop land-based culture of cockles it is crucial to have a supply of high quality live microalgal diets produced with minimum effort. Therefore, the use of simplified microalgae media, with different nitrogen sources (nitrate or ammonium) and molar N:P ratio, phosphorus, silica, iron, manganese and vitamins were also investigated. Chaetoceros muelleri, a marine diatom that was chosen given its robustness and quality as food for juvenile cockles, reacted positively to all simplified media. At the exponential phase, all cultures had reached similar cellular concentrations and dry weight productions. Cultures grown on ammonium media had a longer cultivation period, 20 days. Considering dry-weight production, culture duration, nutrient efficiency and lipid composition, the simplified media containing ammonium, phosphorus, silica, iron, manganese and vitamins proved to be a viable choice for batch culture of C. muelleri. The choice between these two media depends on the final purpose of the microalgae cultures and whether lipid contents (NH49:1), dry weight biomass (NH425:1) or nitrogen input and output (NH49:1) are more important.

In this thesis it was demonstrated that mono-algal diets with high EPA, as well as mixed live microalgae diets with high EPA and DHA contents proved to be suitable diets for C. edule juveniles. In addition, a positive relation between growth and the amount fed was found. The growth rates of the cultured cockles in this thesis are in accordance with the rates observed under natural conditions. The use of the simplified microalgae culture medium tested represents a significant decrease in the cost and preparation of the medium, as well as longer production and harvest periods, while maintaining microalgae quality. These results indicate that land-based aquaculture of cockles and microalgae is therefore a promising venture, with potential for expansion.

Of fats and foods
Kromhout, D. - \ 2015
Wageningen : Wageningen UR, Wageningen - ISBN 9789462571983 - 24
nutrition and health - heart diseases - cardiovascular diseases - fatty acids - cholesterol - disease prevention - food consumption - risk factors - public health - human nutrition research - voeding en gezondheid - hartziekten - hart- en vaatziekten - vetzuren - ziektepreventie - voedselconsumptie - risicofactoren - volksgezondheid - voedingsonderzoek bij de mens
Farewell address upon retiring as Professor of Public Health Research at Wageningen University on 16 April 2015
Unravelling mechanisms of dietary flavonoid-mediated health effects: effects on lipid metabolism and genotoxicity
Hoek-van den Hil, E.F. - \ 2015
University. Promotor(en): Ivonne Rietjens; Jaap Keijer, co-promotor(en): Peter Hollman. - Wageningen : Wageningen University - ISBN 9789462573031 - 157
flavanoïden - flavonoïden - vetzuren - quercetine - flavonolen - lichaamsgewicht - lipidenmetabolisme - hart- en vaatziekten - lever - vetweefsel - gezondheid - genotoxiciteit - voeding - muizen - flavanoids - flavonoids - fatty acids - quercetin - flavonols - body weight - lipid metabolism - cardiovascular diseases - liver - adipose tissue - health - genotoxicity - nutrition - mice

Summary

Consumption of foods containing flavonoids is associated with a reduced risk of cardiovascular diseases (CVD), possibly by lipid-lowering effects. On the other hand, for one of these flavonoids, quercetin, also genotoxicity was shown especially in in vitro bioassays. Therefore, the first aim of this thesis was to identify mechanisms underlying potential beneficial health effects of flavonoids. The focus was on hepatic lipid metabolism and circulating lipids and a molecular and physiological approach was used. Secondly, we aimed to study the potential in vivo genotoxic effects of quercetin by transcriptome analyses in liver and small intestine, since these represent the tissues of first contact exposed to relatively high levels upon oral intake of flavonoids.

Circulating lipids are important CVD-related risk markers, which are in general determined with commercially available enzyme-based assays. However, the usual enzyme in these assays, peroxidase, has previously been reported to be inhibited by flavonoids. Therefore, we have studied in chapter 2 whether these assays can adequately be used in flavonoid research. We observed that various flavonoid aglycones interfere with peroxidase used in triglycerides (TG) and free fatty acids (FFA) enzymatic assays, reporting incorrect lower TG and FFA levels than actually present. Furthermore, addition of metabolites such as isorhamnetin or quercetin-3-O-glucuronide, the major metabolite of quercetin in human and rat plasma, to murine serum also resulted in a significant reduction of the detected TG levels, while a trend was seen towards reduced FFA levels. It can be concluded that when applying these biochemical assays, vigilance is needed and alternative analytical methods assessing FFA or TG levels should preferably be applied for studying the biological effects of flavonoids on TG and FFA levels.

In chapter 3 mechanistic and physiological effects of quercetin on hepatic lipid metabolism were studied. C57BL/6JOlaHsd male adult mice received a mild high-fat (30 en%) diet without or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Gas chromatography and 1H-NMR were used to quantitatively measure serum lipid profiles. Whole genome microarray analysis of liver tissue was used to identify potential mechanisms underlying altered circulating lipid levels by quercetin supplementation. Body weight, energy intake and hepatic lipid accumulation did not differ significantly between the quercetin and the control group. In serum of quercetin-fed mice, TG levels were decreased by 14% (p<0.001) and total poly unsaturated fatty acids (PUFA) levels were increased by 13% (p<0.01). Levels of palmitic acid, oleic acid, and linoleic acid were all decreased by 9-15% (p<0.05) in quercetin-fed mice. Both palmitic acid and oleic acid can be oxidized by omega-oxidation. Gene expression profiling showed indeed that quercetin increased hepatic lipid metabolism, especially omega-oxidation. At the gene level, this was reflected by the up-regulation of cytochrome P450 (Cyp) 4a10, Cyp4a14, Cyp4a31 and Acyl-CoA thioesterase 3 (Acot3). Two relevant regulators, cytochrome P450 oxidoreductase (Por, rate limiting for cytochrome P450 activities) and the transcription factor constitutive androstane receptor (Car; official symbol Nr1i3) were also up- regulated in the quercetin-fed mice. We concluded that quercetin intake increased hepatic lipid omega-oxidation and lowered corresponding circulating lipid levels, which may contribute to potential beneficial effects of quercetin on CVD.

Subsequently, in chapter 4 effects of quercetin supplementation were studied in mice given a high-fat (40 en%) background diet. The set-up of the experiment was the same as in chapter 3, with the exception of the background diet that was used, which was different in fat content and composition. This high-fat diet-induced body weight gain, and serum and hepatic lipid accumulation, which are all known risk factors for CVD. The aim of this study was to investigate the effects and underlying molecular mechanisms of the effects of the flavonoid quercetin on hepatic lipid metabolism in mice given this high-fat diet background. C57BL/6JOlaHsd male adult mice received the high-fat diet without or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Body weight gain was 29% lower in quercetin fed mice versus control mice (p<0.01), while the energy intake was not significantly different. Quercetin supplementation lowered high-fat diet-induced hepatic lipid accumulation to 29% of the amount present in the control mice (p<0.01). 1H-NMR serum lipid profiling revealed that the supplementation also significantly lowered high-fat diet-induced increases in serum lipid levels. Global gene expression profiling of liver showed that cytochrome P450 2b (Cyp2b) genes, key target genes of the transcription factor Car, were down-regulated. However, the induction of omega-oxidation observed by quercetin supplementation to a mild high-fat (30en%) diet (chapter 3), was not observed this time with the high-fat (40en%) diet. Cumulatively, quercetin decreased high-fat diet-induced body weight gain, hepatic lipid accumulation and serum lipid levels. This was accompanied by regulation of cytochrome P450 2b genes in liver, which are considered to be under transcriptional control of CAR. The quercetin effects are likely dependent on the fat content and composition of the diet.

In chapter 5 we investigated whether flavonoids from other flavonoid subclasses can exert the same effects as we observed for quercetin. Effects of quercetin, hesperetin, epicatechin, apigenin and anthocyanins, in C57BL/6JOlaHsd male adult mice fed a high-fat diet for 12 weeks were compared, relative to a normal-fat diet. High-fat diet-induced body weight gain was significantly lowered by all flavonoids (17-29%), but most by quercetin. Quercetin significantly lowered high-fat diet-induced hepatic lipid accumulation (by 71%). High-fat diet-induced increases of mesenteric adipose tissue weight and serum leptin levels were significantly lowered by quercetin, hesperetin, and anthocyanins. Adipocyte cell size and adipose tissue inflammation were not affected.

The effects on body weight and adiposity could not be explained by individual significant differences in energy intake, energy expenditure, nor by differences in activity. Lipid metabolism was not changed as measured by indirect calorimetry or expression of known lipid metabolic genes in liver and white adipose tissue. Hepatic expression of Cyp2b9 was strongly down-regulated by all flavonoids. Overall, all five flavonoids lowered parameters of high-fat diet-induced adiposity, with quercetin being most effective.

Next to the beneficial health effects of flavonoids, the safety of flavonoids is under discussion, mainly because of potential genotoxic effects found for quercetin in vitro. Therefore, in chapter 6 the in vivo genotoxicity of this flavonoid was studied by transcriptome analyses in two tissues, small intestine and liver, where the highest exposure to quercetin is expected. This is especially of interest in view of high intake by widely available food supplements. Quercetin (0.33%) supplemented to a high-fat diet was administered to C57BL/6JOlaHsd male adult mice during 12 weeks. Serum alanine aminotransferase and aspartate aminotransferase levels revealed no indications for hepatotoxicity. General microarray pathway analysis of liver and small intestinal tissue samples showed no regulation of genotoxicity related pathways. In addition, analysis of DNA damage pathways in these tissues did also not point at genotoxicity. Furthermore, comparison with a published classifier set of transcripts for identifying genotoxic compounds did not reveal any similarities in the regulation of these classifier set by quercetin. Available microarray datasets of known genotoxic liver carcinogens, 2-acetylaminofluorene and aflatoxin B1 in mice were taken along as positive controls for comparison, and indeed showed genotoxic properties (regulation of genotoxic related genes) in the analyses. This transcriptomic analysis showed that supplementation with quercetin at ~350 mg/kg bw/day for 12 weeks did not induce genotoxicity in liver and small intestine.

In conclusion, we have shown in vivo efficacy of flavonoids reflected by effects on metabolic health parameters, including hepatic lipid metabolism. These effects on hepatic lipid metabolism seemed to be related or influenced by the transcription factor CAR. The dietary contexts appeared to modify the health effects. The five studied flavonoids in general showed the same effects, with quercetin being the most effective. No genotoxicity of quercetin was found by transcriptome analyses in liver and small intestine. Overall, we have obtained indications for beneficial health effects of flavonoids in mice, which makes it interesting to study if these effects can be extrapolated to humans to further explore their potential as functional compounds of dietary flavonoid intake.

Smediger kaas door juiste voer
Hettinga, K.A. ; Dijkstra, J. - \ 2014
De zelfkazer 66 (2014)6. - ISSN 0166-4549 - p. 10 - 11.
kazen - smaak - eiwitgehalte - vetgehalte - voersamenstelling - onverzadigde vetten - vetzuren - melk - melkvet - cheeses - taste - protein content - fat content - feed formulation - unsaturated fats - fatty acids - milk - milk fat
Veel kaasmakers willen smedige (zachte, smeuïge) kaas maken, want de gemiddelde consument vindt die kaas het lekkerst. Kasper Hettinga en Jan Dijkstra van Wageningen Universiteit vertellen hoe de smedigheid van kaas kan worden beïnvloed door de samenstelling van het veevoer.
Genetic variation of milk fatty acid composition between and within dairy cattle breeds
Maurice - Van Eijndhoven, M.H.T. - \ 2014
University. Promotor(en): Johan van Arendonk; Roel Veerkamp, co-promotor(en): Mario Calus. - Wageningen : Wageningen University - ISBN 9789462571488 - 184
dierveredeling - melkkoeien - vetzuren - melk - genetische variatie - rundveerassen - heritability - melkvet - genetische bronnen van diersoorten - melkveehouderij - animal breeding - dairy cows - fatty acids - milk - genetic variation - cattle breeds - milk fat - animal genetic resources - dairy farming

Abstract

Maurice – Van Eijndhoven, M.H.T. (2014). Genetic variation of milk fatty acid composition between and within dairy cattle breeds. PhD thesis, Wageningen University, the Netherlands

Fat is one of the main components in bovine milk and comprises a large number of individual fatty acids (FA). The composition of FA in milk varies considerably due to differences in the genetics and nutrition of cows and an increasing interest in the possibilities for modifying FA composition can be noticed nowadays. In this thesis two fields of interest were combined, namely: production of milk with specific milk fat composition and conservation of native cattle breeds. Therewith, the overall objective of this thesis was to investigate the variability of detailed milk FA composition between and within different dairy cattle breeds, including the mainstream Holstein Friesian (HF) and Jersey, and the native dual purpose breeds Meuse-Rhine-Yssel (MRY), Groningen White Headed (GWH) and Dutch Friesian (DF) in the Netherlands. For this study the accuracy of mid-infrared (MIR) spectrometry was evaluated for predicting FA composition in different breeds. Differences of milk FA composition within and between breeds were investigated using MIR and Gas Chromatography (GC) information. Finally, similarities in genomic variation associated with detailed milk fat composition between the mainstream HF breed and native dual purpose breeds were studied. Results show that MIR is an accurate method for predicting FA composition among different breeds and countries. Evaluating the FA composition in different breeds, differences were found in milk FA composition among herds using different cattle breeds in the Netherlands, based on detailed milk FA measurements using GC. Evaluating the FA composition in milk between and within breeds using a large dataset that included MIR spectra of milk from cows from a range of farms using one or more breeds, in general, only minor breed differences in FA composition were found and HF showed more genetic variation in FA composition compared to MRY. Furthermore, differences were detected between the native breeds MRY, DF and GWH in genomic variations of regions that are associated with FA composition in HF, while most variation in these main regions was clearly observed in HF. Overall, it was concluded that no large differences existed in milk FA composition among the native Dutch dual purpose breeds and the mainstream HF breed. It is suggested, however, that selecting specific FA composition differences in farms using different breeds in the Netherlands can attribute to modifying the FA composition in bovine milk production.

Unraveling the genetic background of bovine milk fat composition
Bouwman, A.C. - \ 2014
University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis; Marleen Visker. - Wageningen : Wageningen University - ISBN 9789461739063 - 176
dierveredeling - melkveehouderij - melkvee - melkproductie - vetzuren - genomica - loci voor kwantitatief kenmerk - animal breeding - dairy farming - dairy cattle - milk production - fatty acids - genomics - quantitative trait loci

Identification of genomic regions, and preferably individual genes, responsible for genetic variation in bovine milk fat composition enhances the understanding of biological pathways involved in fatty acid synthesis and is expected to increase opportunities for changing bovine milk fat composition by means of selective breeding. This thesis aimed to unravel the genetic background of bovine milk fat composition by detection, confirmation and fine-mapping of quantitative trait loci (QTL) for milk fatty acids in Dutch Holstein Friesian cattle. In addition, causal relations between fatty acids were explored. For this study roughly 2,000 dairy cows were genotyped with 50,000 DNA markers and phenotyped for individual fatty acids in both winter and summer milk samples using gas chromatography. Genome-wide association studies (GWAS) showed that milk fat composition has a complex genetic background with three major QTL that explain a relatively large fraction of the genetic variation of several milk fatty acids, and many QTL that explain a relatively small fraction of the genetic variation. Results from the GWAS for summer milk fatty acids confirmed most associations that were detected in the winter milk samples. Moving from linkage analysis toward GWAS confirmed and refined the size of previously detected QTL regions and resulted in new QTL regions. Performing GWAS based on individual fatty acids resulted in additional QTL as compared to GWAS based on fat percentage or yield. This shows that refinement of complex phenotypes into underlying components results in better links between genes and phenotypes. By increasing the marker density, the QTL on BTA19 was refined to a linkage disequilibrium block that contained 2 genes: coiled-coil domain containing 57 and fatty acid synthase. A search for causal relations between fatty acids resulted in a pathway from C4:0 to C12:0, which resembled the de novo synthesis pathway. Causal relation between the QTL on BTA19 and de novo fatty acids showed that the QTL affects C4:0, C6:0, C8:0, C10:0 and C14:0 directly, while C12:0 was indirectly affected by the QTL through its effect on C10:0. The potential of GWAS based on MIR predicted fatty acids was explored but failed to detect some QTL and resulted in additional QTL that were not detected based on GC measurements. Therefore, MIR predicted phenotypes add complexity to the genotype-phenotype relationship, and renders MIR predicted phenotypes less appropriate to identify candidate genes and to infer the biological background of traits.

Vitaal naar de eindstreep
Tieland, C.A.B. ; Rest, O. van de; Groot, C.P.G.M. de - \ 2013
WageningenWorld 2013 (2013)4. - ISSN 2210-7908 - p. 26 - 29.
voeding en gezondheid - ouderen - verouderen - vitaminetekorten - vetzuren - eiwit - gezondheidsbevordering - nutrition and health - elderly - aging - vitamin deficiencies - fatty acids - protein - health promotion
Hoe worden we gezond oud? Trainen en extra eiwitten werken, blijkt uit onderzoek van de afdeling Humane voeding. Over het effect van vitamines en omega-3 vetzuren is het laatste woord nog niet gezegd.
Nutritional Systems Biology of Fat : integration and modeling of transcriptomics datasets related to lipid homeostasis
Ohid Ullah, M. - \ 2012
University. Promotor(en): Michael Muller, co-promotor(en): Guido Hooiveld. - S.l. : s.n. - ISBN 9789461733818 - 158
vetzuren - genexpressie - lipidenmetabolisme - obesitas - transcriptomica - statistische analyse - wiskundige modellen - fatty acids - gene expression - lipid metabolism - obesity - transcriptomics - statistical analysis - mathematical models

Fatty acids, in the form of triglycerides, are the main constituent of the class of dietary lipids. They not only serve as a source of energy but can also act as potent regulators of gene transcription. It is well accepted that an energy rich diet characterized by high intakes of dietary fat is linked to the dramatic increase in the prevalence of obesity in both developed and developing countries in the last several decades. Obese individuals are at increased risk of developing the metabolic syndrome, a cluster of metabolic abnormalities that ultimately increase the risk of developing vascular diseases and type 2 diabetes. Many studies have been performed to uncover the role of fatty acids on gene expression in different organs, but integrative studies in different organs over time driven by high throughput data are lacking. Therefore, we first aimed to develop integrative approaches on the level of individual genes but also pathways using genome-wide transcriptomics datasets of mouse liver and small intestine that are related to fatty acid sensing transcription factor peroxisome proliferator activated receptor alpha (PPARα). We also aimed to uncover the behavior of PPARαtarget genes and their corresponding biological functions in a short time series experiment, and integrated and modeled the influence of different levels of dietary fat and the time dependency on transcriptomics datasets obtained from several organs by developing system level approaches.

We developed an integrative statistical approach that properly adjusted for multiple testing while integrating data from two experiments, and was driven by biological inference. By quantifying pathway activities in different mouse tissues over time and subsequent integration by partial least squares path model, we found that the induced pathways at early time points are the main drivers for the induced pathways at late time points. In addition, using a time course microarray study of rat hepatocytes, we found that most of the PPARα target genes at early stage are involved in lipid metabolism-related processes and their expression level could be modeled using a quadratic regression function. In this study, we also found that the transcription factorsNR2F, CREB, EREF and RXR might work together with PPARα in the regulation of genes involved in lipid metabolism. By integrating time and dose dependent gene expression data of mouse liver and white adipose tissue (WAT), we found a set of time-dose dependent genes in liver and WAT including potential signaling proteinssecreted from WAT that may induce metabolic changes in liver, thereby contributing to the pathogenesis of obesity.

Taken together, in this thesis integrative statistical approaches are presented that were applied to a variety of datasets related to metabolism of fatty acids. Results that were obtained provide a better understanding of the function of the fatty acid-sensor PPARa, and identified a set of secreted proteins that may be important for organ cross talk during the development of diet induced obesity.

Fatty acid digestion, synthesis and metabolism in broiler chickens and pigs
Smink, W. - \ 2012
University. Promotor(en): Martin Verstegen; Wouter Hendriks, co-promotor(en): Walter Gerrits. - S.l. : s.n. - ISBN 9789461733061 - 141
dieren - diervoeding - vetzuren - spijsvertering - metabolisme - varkens - vleeskuikens - animals - animal nutrition - fatty acids - digestion - metabolism - pigs - broilers


The impact of variation in the composition of dietary fat on digestion, metabolism and synthesis of fatty acids was studied in broiler chickens and in pigs. In young broiler chickens, digestion of unsaturated fatty acids was substantially higher compared with that of saturated fatty acids. Positional distribution appeared important. Particularly digestion of saturated fatty acids, e.g. palmitic acid (C16:0), esterified at the sn-1 and -3 position of the glycerol backbone was lower (51%) compared with that observed at the sn-2 position (90%). Based on these observations, an equation was developed predicting the digestion of dietary fat sources in broiler chickens and pigs, taking fatty acid composition, the positioning, and the proportion of free fatty acids into account. The deposition of fat, especially of monounsaturated fatty acids in body tissues, increased in broilers by feeding saturated fats in comparison with unsaturated fats caused by both a reduced ß-oxidation and an increased rate of de novo synthesis of fatty acids. In a feeding trial with pigs, starch, saturated and unsaturated fatty acid sources were compared at similar intakes of net energy. Growth performance and backfat thickness were unaffected by dietary energy source. Intramuscular fat content, however, tended to be increased in starch fed pigs when compared with pigs fed the saturated fatty acid source. To study the interactions between dietary linoleic acid (LA; C18:2 n-6) and -linolenic acid (ALA; C18:3 n-3) and their impact on the synthesis of long-chain polyunsaturated fatty acids (LC-PUFA) in both the n-3 and n-6 chains, a trial was designed in which identical increments in the intake of ALA and LA were fed to growing pigs. Generally, dietary LA inhibited the synthesis of n-3 LC-PUFA in the liver. Dietary ALA increased the content of eicosapentaenoic acid (EPA; C20:5 n-3) but decreased that of docosahexaenoic acid (DHA; C22:6 n-3) in the liver. DHA levels in brain were hardly affected by both dietary LA and ALA. It was concluded that in addition to Δ6 desaturase, elongase 2 might be a rate-limiting enzyme in the formation of DHA. The impact of these findings on the potential of contribution of feeding LA and ALA to pigs to meet human dietary requirements for LC-PUFA by meat products was investigated by analysing the fatty acid composition of muscle and fat tissues. It appeared impossible to attain substantial improvements in tissue DHA contents by feeding different combinations of LA and ALA. However, EPA of intramuscular fat can be increased by feeding ALA, particularly when restricting LA intake. In addition, docosapentaenoic acid (DPA; C22:5 n-3) was increased in both muscle and backfat by dietary ALA. DPA might have comparable biological effects as EPA. The potential of meat products to supply DPA in food is considerable and therefore of interest.

Mapping the diverse functions of dietary fatty acids via target gene regulation
Georgiadi, A. - \ 2012
University. Promotor(en): Michael Muller; Sander Kersten. - S.l. : s.n. - ISBN 9789461732804 - 200
vetzuren - dieet - genregulatie - nutrigenomica - fatty acids - diet - gene regulation - nutrigenomics

Dietary fat is a strong predictor of chronic diseases, such as cardiovascular diseases, obesity, diabetes, dyslipidemia and metabolic syndrome. A great number of epidemiological and observational studies clearly show that in addition to the amount of fat consumed in a diet, fat composition is an equally important factor in the development of chronic diseases. Evidence abounds indicating that adherence to a diet with high content of polyunsaturated (PUFAs) and monounsaturated fatty acids (MUFAs) such as the Mediterranean diet has substantial health benefits, while diets with high content of saturated fatty acids (SFAs) such as the Western type diet increase the risk for the development of several chronic diseases.

Nutritional genomics or nutrigenomics investigates the interaction between nutrients and genes at the molecular level, by using genomic tools. Within the field of nutrigenomics, dietary fatty acids and their metabolites are seen as signaling molecules that target specific cellular response systems. Dietary fatty acids have been reported to bind physically to PPARs, a family of ligand activated transcription factors, that play a major role in metabolic homeostasis. Three PPAR isotypes have been identified, PPARα, PPARβ/δ and PPARγ. Their expression and target genes vary among different tissues and cell types.

After a meal triglycerides are packed into chylomicrons in the small intestine and via the lymph system, they reach the blood and the peripheral tissues. Triglyceride chylomicrons deliver free fatty acids to the organs after being lipolylised by lipoprotein lipase (LPL), which is anchored to the capillary endothelium. Among different organs, heart and liver show the highest uptake of dietary triglycerides, postprandialy. However, opposite to the liver, heart is a constant working muscle, which covers its demands on energy mainly by fatty acids, delivered to the heart via hydrolysis of circulating triglyceride-rich lipoproteins. Unbalanced fatty acid uptake and fatty acid oxidation is common in cardiac diseases, such as cardiac failure, myocardial ischemia and diabetes. Heart is characterized by decreased lipid storage capacity, therefore chronic elevated levels of lipids uptake and intracellular storage is considered harmful and may lead to lipotoxic cardiomyopathy.

Our first aim was to explore the whole genome effects of individual dietary fatty acids in the intact heart via transcriptional profiling. By conducting these experiments in wild-type and PPARα−/− mice, we aimed to determine the specific contribution of PPARα, which has been previously described as a master regulator of lipid homeostasis in the heart. We took advantage of a unique experimental model, where mice were given a single oral bolus of synthetic triglycerides composed of a single fatty acid. We sacrificed the mice 6hours after the oral gavage and we compared the effects of different fatty acids on gene expression by microarray analysis in the total heart. Many genes were regulated by one particular treatment only and among those most of them showed large functional divergence. Although, the majority of genes responding to fatty acid treatment were regulated in a PPARα-dependent manner, emphasizing the importance of PPARα in mediating transcriptional regulation by fatty acids in the heart, we observed a substantial number of genes regulated in a PPARα- independent manner. Finally, we observed that deletion and activation of PPARα had a major effect on expression of numerous genes involved in metabolism and immunity.

We identified response to oxidative stress as the top upregulated process activated by all administered fatty acids in the heart. High rates of mitochondria oxidation, due to increased supply of substrate after the oral gavage are coupled with enzymatic and non- enzymatic mechanisms aiming to counterbalance the production of highly reactive secondary products of the respiratory chain, the reactive oxygen species (ROS) in the heart. Under conditions such as chronic high fat diet or insulin resistance, increased lipid influx in combination with uncontrolled production of ROS and lipid intermediates may result in mitochondrial malfunctioning and lipid accumulation. Myocardial lipotoxicity refers to the accumulation of intramyocardial lipids and is associated with contractile dysfunction and even myocytes death. We found Angptl4 to be the top upregulated gene, in all groups that received the fatty acids oral gavage. Angptl4 has been described as a target gene of PPARs and an endogenous inhibitor of the triglyceride hydrolyzing enzyme lipoprotein lipase (LPL), which catalyzes uptake of circulating lipids into tissues. We were able to show that the strong upregulation of Angptl4 by dietary fatty acids is mediated by PPARβ/δ and is part of a feedback mechanism aimed at protecting the heart against lipid overload and consequently fatty acid–induced oxidative stress, one of the hallmarks of lipotoxic cardiomyopathy.

Angptl4 has been shown to have a potent inhibitory effect in LPL activity and subsequent reduction in uptake of lipids by several tissues and cell types, including macrophages. Furthermore, Angptl4 was shown to prevent the formation of foam cells in mesenteric lymph nodes upon high fat feeding. Accordingly, we hypothesized that Angptl4 may affect atherosclerosis development by reducing foam cell formation. Thus, our second aim was to investigate the role of Angptl4 on atherosclerosis development. We studied Angptl4 expression in atherosclerotic lesions and macrophages and determined the effect of Angptl4 transgenic overexpression in atherosclerosis prone ApoE3Leiden (E3L) mice fed a Western diet containing 0.4% cholesterol. We observed a decrease in atherosclerosis in Angptl4 overexpressing mice on an ApoE3L background. This effect was independent of the plasma cholesterol and triglyceride levels. Importantly, Angptl4Tg.E3L exhibited a less pro- inflammatory phenotype with decreased accumulation of monocytes/macrophages in the atherosclerotic plaque, suggesting an anti-inflammatory role of Angptl4 in atherosclerosis development.

Finally, we set out to identify transcriptional targets of fatty acids in macrophages, as part of a general goal to elucidate mechanisms through which fatty acids exhibit a direct role in modulating inflammatory processes in macrophages. We identified Hig-2 to be strongly upregulated by all treatments. We found expression of Hig-2 to be the highest in peritoneal macrophages and white adipose tissue. Chronic high fat feeding increased Hig-2 expression levels in adipose tissue but not in liver. Immunohistochemistry indicated colocalization of Hig-2 with Cd68 in infiltrating macrophages as part of crown-like structures. Based on these findings we propose that Hig-2 has a specific role in macrophages and may function as an interesting target in the study of obese adipose tissue.

In conclusion, this thesis contributes new information on gene regulation by dietary PUFA in the mammalian heart and provides mechanistic insight on their previous reported beneficial effects. Furthermore, we reveal a novel protective role of Angptl4 in atherosclerosis development. We propose that this effect is mediated by a mechanism, which is independent of inhibition of LPL-mediated systemic lipid clearance and it is probably related to the effect of Angptl4 on macrophage oxLDL uptake and chemotaxis. Finally, in the present thesis we start up an effort to identify fatty acid target genes in macrophages, which open new future research paths.

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