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Raw meat structure and feeding behaviour of domestic cats
Thomas, David ; Schreurs, Nicola ; Hendriks, W.H. ; Bosch, G. - \ 2018
Archeologisch onderzoek in de omgeving van het prehistorische vuursteenmijnveld te Rijckholt - St.Geertruid : De resultaten van 2011, 2012 en 2013
Brinkkemper, O. ; Bruinink, A.C. ; Deeben, J. ; Guralnik, B. ; Hoebe, P. ; Huisman, H. ; Kort, J.W. de; Laarman, F. ; Meirvenne, M. van; Orbons, J. ; Os, B. van; Parys, V. van; Schreurs, J. ; Theunissen, L. ; Verhegge, J. ; Versendaal, Alice ; Wallinga, J. - \ 2018
Amersfoort : Rijksdienst voor het Cultureel Erfgoed - ISBN 9789057993022 - 371 p.
A novel scoring system for the classification of the health status of growing-finishing pig farms
Jansman, A.J.M. ; Kampman-van der Hoek, E. ; Sakkas, P. ; Beers-Schreurs, H.M.G. van; Peet-Schwering, C.M.C. van der; Borne, J.J.G.C. van den; Gerrits, W.J.J. - \ 2016
- 1 p.
Health status of pig farms can vary considerably and relates to the variation in zootechnical performance among farms. Classification of farm health can be helpful in monitoring farm health status in time and for the application of intervention strategies to improve farm health status. The aim of the current study was to develop a concept for classification of the health
status of growing-finishing pig farms. Six traits were incorporated into a health status web, related to the zootechnical performance and measurements at slaughter. Performance data from 1,074 and 783 Dutch pig farms, and abattoir data of 50,208 and 47,426 farm deliveries to slaughterhouses, acquired over 2011 and 2012 respectively, were used as a representative sample for the Dutch growing-finishing pig population to calculate the 25th and 75th percentiles of each trait per year. Per farm, a score was calculated per trait by inter- and extrapolation using the 25th and 75th percentiles from the Dutch pig population. The farm score was defined as the mean score over the six traits. A farm was classified as having a suboptimal health with a farm score between 50 and 62.5, as having a conventional health status with a farm score between 62.5 and 87.5 and as having a high health status with a farm score between 87.5 and 100. Further, two datasets were compiled: dataset 1 with farm data of 179 farms over the year 2011, and dataset 2 with farm data of 70 farms over both 2011 and 2012. In dataset 1, 13 farms were characterized as high health, 159 farms as conventional and seven farms as having a low health status. Analysis of dataset 2 revealed that farm scores are consistent across years,
indicating that the farm score is farm specific and the health status web is a valuable concept to characterize growing-finishing pig farms on their health status.
The association between portion size, nutrient intake and gestational weight gain : A secondary analysis in the WATCH study 2006/7
Blumfield, M.L. ; Schreurs, M. ; Rollo, M.E. ; Macdonald-Wicks, L.K. ; Kokavec, A. ; Collins, C.E. - \ 2016
Journal of Human Nutrition and Dietetics 29 (2016)3. - ISSN 0952-3871 - p. 271 - 280.
Gestational weight gain - Nutrient intake - Portion size - Pregnancy

Background: Excessive gestational weight gain (GWG) is associated with adverse maternal-child health outcomes. Managing energy intake and GWG versus optimising nutrient intake can be challenging. The present study aimed to examine the relationships between dietary portion size, GWG and nutrient intakes during pregnancy. It is hypothesised that, after adjustment for potential confounders, portion size would be positively associated with both GWG and nutrient intakes during pregnancy. Methods: Prospective data were obtained for 179 Australian women from the Women and Their Children's Health Study. A validated food frequency questionnaire was used at 18-24 and 36-40 weeks of gestation to quantify diet and portion size during the previous 3 months of pregnancy. Nutrient intakes were compared with Australian Nutrient Reference Values (NRVs). GWG was measured up to 36 weeks and compared with the Institute of Medicine weight gain recommendations (WtAdh). Results: In multivariate regression models, portion size factor (PSF) was positively associated with GWG in women with high socio-economic status (SES; β = 0.20, P = 0.04) and those with an overweight/obese pre-pregnancy body mass index (BMI) (β = 0.28, P = 0.04). PSF uniquely accounted for 8.2% and 3.7% of the variability in GWG for women with high SES and overweight/obese pre-pregnancy BMIs, respectively. Nutrient intakes and PSF were similar regardless of WtAdh. Women achieved NRVs for calcium and zinc in all PSF categories. Most of the women with large PSF still failed to achieve the NRVs for folate (95.7%), iron (89.6%) and fibre (85.5%). Conclusions: All women require advice on quality food choices during pregnancy to optimise health outcomes. Targeting portion size alone is insufficient to manage GWG but may prove to be a valuable tool in pregnant women of high SES and/or those who are overweight/obese pre-pregnancy.

Dietary Amino Acid Deficiency Reduces the Utilization of Amino Acids for Growth in Growing Pigs after a Period of Poor Health
Hoek, E. van de; Jansman, A.J.M. ; Borne, J.J.G.C. van den; Peet-Schwering, C.M.C. van der; Beers-Schreurs, H.M.G. van; Gerrits, W.J.J. - \ 2016
The Journal of Nutrition 146 (2016)1. - ISSN 0022-3166 - p. 51 - 58.
amino acid deficiency
Background: During immune system activation, partitioning of amino acids (AAs) changes between protein gain and use by the immune system. Objective: We determined the effects of health status and dietary AA deficiency on nitrogen retention and AA utilization in pigs. Methods: Barrows (55 d of age) were obtained from good health (GH, n = 14) or poor health (PH, n = 14) status farms and allocated to a diet either adequate in essential amino acids (Adq) or 25% deficient in Met + Cys, Thr, and Trp (Def). Nitrogen balance was measured and AA irreversible loss rates (ILRs) were measured after an intravenous bolus of U-13C–labeled L-AAs. Results: On arrival at the experimental facilities, the PH pigs had 14% lower serum albumin and 50% greater serum haptoglobin and blood leukocyte counts than the GH pigs (P < 0.01), but the PH pigs showed signs of recovery during the trial. Total tract nitrogen digestibility was 3 percentage points lower in the PH pigs (P < 0.01). The PH-Adq pigs had compensatory body weight gain after arrival, coinciding with 7% greater nitrogen retention (P < 0.01) in the PH pigs than in the GH pigs. The PH pigs had a 24% greater ILR for Lys. Health status × diet interactions for Lys (P = 0.07), Val (P = 0.03), and Leu (P = 0.10) pool sizes and a greater urea pool size in the PH pigs (P = 0.01) support the observation that the increase in the ILR of Lys in the PH pigs was related to oxidation when feeding the Def diet, but to synthesis when feeding the Adq diet. Feeding Def diets increased monocyte counts by 30% (P < 0.01). Conclusions: This study illustrates how the competition for AAs between protein synthesis associated with immune system activation and body protein deposition is greater when the dietary supply of Met + Cys, Thr, and Trp is limited in pigs during and after a period of poor health.
Postprandial oxidative losses of dietary leucine depend on the time interval between consecutive meals : A model study with rats
Myszkowska-Ryciak, J. ; Keller, J.S. ; Bujko, J. ; Stankiewicz-Ciupa, J. ; Koopmanschap, R.E. ; Schreurs, V.V.A.M. - \ 2015
Journal of Animal and Feed Sciences 24 (2015)1. - ISSN 1230-1388 - p. 71 - 79.
Breath test - Consecutive meals - Rat - Time intervals - [1-<sup>13</sup>C]-leucine oxidation

Postprandial oxidative losses of egg white-bound [1-13C]-leucine were studied as 13C recovery in the breath of rats in relation to different time intervals between two meals. Male Wistar rats (n = 48; 68.3 ±5.9 g) divided into 4 groups (n = 12) were fed two meals a day (9:00 and 16:30; interval 7 h) of a 13.2% egg white-based diet for 30 min. After 14 days, 3 out of the 4 groups received the 2nd meal at shorter time intervals of 3, 1, and 0 h. Two [13CO2] breath tests (BT) were performed on days 19 and 40. The breath samples were analyzed for 13C Atom % (At %) enrichment by IRMS, and the results were expressed as the rate of 13C At % excess and cumulative recovery (% of dose). The 7 h interval group showed higher 13C cumulative recovery after the 2nd meal during both the BT and after the 1st meal on the day 40 BT compared with the 3, 1, and 0 h intervals. In groups with the 3, 1, and 0 h intervals, the cumulative recovery of 13C after the 2nd meal was lower compared with the 1st meal due to interaction between meals, which probably caused dilution of the tracer in the larger volume of feed in the rat's stomach. On day 40, all cumulative recovery values were higher than on day 19. An important finding of this study is that despite the differences in postprandial Leu oxidation among interval groups, the weight gain of all rats was similar.

Tumor Necrosis Factor Receptor 1 Gain-of-Function Mutation Aggravates Nonalcoholic Fatty Liver Disease but Does Not Cause Insulin Resistance in a Murine Model
Aparicio-Vergara, M. ; Hommelberg, P.P.H. ; Schreurs, M. ; Gruben, N. ; Stienstra, R. ; Shiri-Sverdlov, R. ; Kloosterhuis, N.J. ; Bruin, A. de; Sluis, B. van der; Koonen, D.P.Y. ; Hofker, M.H. - \ 2013
Hepatology 57 (2013)2. - ISSN 0270-9139 - p. 566 - 576.
alpha-converting-enzyme - tnf-alpha - dietary-cholesterol - hepatic steatosis - gene-expression - mice - steatohepatitis - obesity - inflammation - activation
Ectodomain shedding of tumor necrosis factor receptor 1 (TNFR1) provides negative feedback to the inflammatory loop induced by TNF alpha. As the significance of this mechanism in obesity-associated pathologies is unclear, we aimed to unravel how much TNFR1 ectodomain shedding controls the development of nonalcoholic fatty liver disease (NAFLD), as well as its role in the development of insulin resistance. We used knockin mice expressing a mutated TNFR1 ectodomain (p55Dns), incapable of shedding and dampen the inflammatory response. Our data show that persistent TNF alpha signaling through this inability of TNFR1 ectodomain shedding contributes to chronic low-grade inflammation, which is confined to the liver. In spite of this, hepatic lipid levels were not affected by the nonshedding mutation in mice fed a chow diet, nor were they worse off following 12 weeks of high-fat diet (HFD) than controls (p55(+/+)) fed an HFD. We detected inflammatory infiltrates, hepatocellular necrosis, and apoptosis in livers of p55(Delta ns/Delta ns) mice fed an HFD, suggesting advanced progression of NAFLD toward nonalcoholic steatohepatitis (NASH). Indeed, fibrosis was present in p55(Delta ns/Delta ns) mice, but absent in wildtype mice, confirming that the p55(Delta ns/Delta ns) mice had a more severe NASH phenotype. Despite low-grade hepatic inflammation, insulin resistance was not observed in p55(Delta ns/Delta ns) mice fed a chow diet, and HFD-induced insulin resistance was no worse in p55(Delta ns/Delta ns) mice than p55(+/+) mice. Conclusion: TNFR1 ectodomain shedding is not an essential feedback mechanism in preventing the development of hepatic steatosis or insulin resistance. It is, however, pivotal in attenuating the progression from "simple steatosis" towards a more serious phenotype with many NASH features. Targeting TNFR1 could therefore be beneficial in attenuating NASH. (HEPATOLOGY 2013;57:566-576)
Stressors and resources mediate the association of socioeconomic position with health behaviours
Mulder, B.C. ; Bruin, M. de; Schreurs, H. ; Ameijden, E.J.C. van; Woerkum, C.M.J. van - \ 2011
BMC Public Health 11 (2011). - ISSN 1471-2458 - 10 p.
psychosocial factors - perceived control - risk-factors - european countries - physical-activity - chronic diseases - life events - mortality - inequalities - disparities
Background Variability in health behaviours is an important cause of socioeconomic health disparities. Socioeconomic differences in health behaviours are poorly understood. Previous studies have examined whether (single) stressors or psychosocial resources mediate the relationship between socioeconomic position and health or mortality. This study examined: 1) whether the presence of stressors and the absence of resources can be represented by a single underlying factor, and co-occur among those with lower education, 2) whether stressors and resources mediated the relation between education and health behaviours, and 3) addressed the question whether an aggregate measure of stressors and resources has an added effect over the use of individual measures. Methods Questionnaire data on sociodemographic variables, stressors, resources, and health behaviours were collected cross-sectionally among inhabitants (n = 3050) of a medium-sized Dutch city (Utrecht). Descriptive statistics and bootstrap analyses for multiple-mediator effects were used to examine the role of stressors and resources in mediating educational associations with health behaviours. Results Higher levels of stressors and lower levels of resources could be represented by a single underlying factor, and co-occurred among those with lower educational levels. Stressors and resources partially mediated the relationship between education and four health- behaviours (exercise, breakfast frequency, vegetable consumption and smoking). Financial stress and poor perceived health status were mediating stressors, and social support a strong mediating resource. An aggregate measure of the stressors and resources showed similar associations with health behaviours compared to the summed individual measures. Conclusions Lower educated groups are simultaneously affected by the presence of various stressors and absence of multiple resources, which partially explain socioeconomic differences in health behaviours. Compared to the direct associations of stressors and resources with health behaviours, the association with socioeconomic status was modest. Therefore, besides addressing structural inequalities, interventions promoting financial management, coping with chronic disease, and social skills training have the potential to benefit large parts of the population, most notably the lower educated. Further research is needed to clarify how stressors and resources impact health behaviours, why this differs between behaviours and how these disparities could be alleviated.
Lactic acid and lactates
Schreurs, V.V.A.M. - \ 2010
NUTRAfoods 9 (2010)1. - ISSN 1827-8590 - p. 7 - 16.
This review aims to integrate the present state of knowledge on lactate metabolism in human and mammalian physiology as far as it could be subject to nutritional interventions. An integrated view on the nutritional, metabolic and physiological aspects of lactic acid and lactates might open a perspective for innovative nutritional applications of lactates in health and wellness. Lactic acid was classically considered to be a dead end waste product of anaerobic glycolysis during severe exercise. Mammals, however, do not excrete lactate indicating that lactate cannot be considered as a dead metabolic end product. Despite a rapid and massive production of lactate, lactate is finally oxidized to the normal metabolic end products CO2 and H2O. Besides direct metabolic effects, nutritional applications of lactic acid and lactates are also considered in relation to dietary mineral supply. To the background that lactic acid is in fact a semi manufactured metabolic product, various nutritional applications are proposed in relation to metabolic training of athletes, modulation of metabolic rate, appetite control and excretion of faecal fat for weight management, lowering the glycemic index of bread and improved mineral supplementation in nutritional formulas for infants and people using proton inhibitors.
Intermittent suckling affects feeder visiting behaviour in litters with low feed intake
Kuller, W.I. ; Soede, N.M. ; Bolhuis, J.E. ; Beers-Schreurs, H.M.G. van; Kemp, B. ; Verheijden, J.H.M. ; Taverne, M.A.M. - \ 2010
Livestock Science 127 (2010)2-3. - ISSN 1871-1413 - p. 137 - 143.
social facilitation - weight-gain - solid food - pigs - piglets - performance - consumption - growth - birth
Intermittent suckling (IS) has proven to stimulate creep feed intake in suckling piglets. This paper describes the development of feeding behaviour in three litters with high (H) and three litters with low (L) feed intake during lactation in both control (C) and IS treatment. In order to synchronize the start of intermittent suckling within a farrowing room, treatment day 0 (T0) was designated as the start of data collection. IS litters were separated from the sow for a period of 12 h/day (0930 to 2130) from T14 to weaning (T25). Feeder visits of individual piglets and nursing behaviour were analysed from continuous video recordings at 5 treatment days: T13, T16, T24, T25 and T26. A high number of CL piglets never visited the feeder during lactation; at T24, 56% of the CL piglets did not visit the feeder. On the other hand, 91% of the ISL and CH piglets and all ISH piglets visited the feeder at least once at T24. In contrast to the other groups, no increase was seen in visiting frequency during lactation in CL piglets. At T24, visiting frequency was higher in ISL than in CL piglets. So, IS stimulated piglets from low feed intake litters to visit the feeder. Between T16 and T24, total feeder time increased in piglets from all groups (P <0.05), except in CL piglets in which no change was found (P > 0.10). Latency to first visit to the feeder after weaning did not differ between groups. It is concluded that IS stimulates piglets from litters with a low level of creep feed intake to visit the feeder during lactation, which familiarizes them with the feeder and the feed during lactation. The IS treatment does not affect feeder visiting behaviour of piglets with an anyhow high level of feed intake during lactation
Platform Technology for Developing Purification Processes
Eppink, M.H.M. ; Schreurs, R. ; Gijsen, A. ; Verhoeven, K. - \ 2009
BioPharm International 22 (2009)3. - ISSN 1542-166X - p. 32 - 42.
To shorten time to market for new therapeutic proteins, new and fast methods, such as high throughput screening, are needed to speed up downstream processing. The platform technology discussed in this article includes a structural approach that can be used as a general procedure to purify therapeutic proteins. The approach starts with ligand screening and selection-on-a-chip, with the Surface Enhanced Laser Desorption Ionization–Time of Flight (SELDI–TOF) mass spectrometer system. Next, resin screening and supplier selection are performed using robotics, followed by scouting studies under dynamic conditions to select the best resin. Finally, optimization studies of critical parameters are carried out with statistical design approaches (design of experiments). Examples are presented to explain the platform approach for purification development in more detail.
Postprandial oxidative losses of free and protein-bound amino acids in the diet: interactions and adaptation
Nolles, J.A. ; Verreijen, A.M. ; Koopmanschap, R.E. ; Verstegen, M.W.A. ; Schreurs, V.V.A.M. - \ 2009
Journal of Animal Physiology and Animal Nutrition 93 (2009)4. - ISSN 0931-2439 - p. 431 - 438.
growing-pigs - nitrogen-utilization - free lysine - breath test - humans - metabolism - assimilation - catabolism - retention - casein
Postprandial oxidation of dietary free amino acids or egg white protein was studied using the [13CO2] breath test in rats, as well as in humans. Thirty-eight male rats were assigned to four dietary test groups. Two diets only differed in their protein fraction. Diet I contained 21% egg white protein. For the breath test egg white protein, intrinsically labelled with [1-13C]-leucine, was used as a substrate. Diet II contained the same amino acids as diet I, though not as egg white protein but in free form. Free [1-13C]-leucine was used to label this diet. In addition, two 1:1 mixtures of both diets were used. During the breath test either the free amino acid or the protein fraction was labelled as in diets I or II. The animals were breath-tested following short-term (day 5) and long-term adaptation (day 20) to their experimental diet. For all diets, including the mixed diets, postprandial oxidative losses on day 5 were significantly higher for the free leucine compared with the protein-derived leucine. Differences between free and protein-derived leucine oxidation had, however, largely disappeared on day 20. The human subjects were breath-tested without any adaptation period to the diets. The oxidative losses of free leucine were also higher than those of protein-derived leucine. None of the studies showed any indication for an interaction between the oxidation of protein-derived amino acids and free amino acids. It is concluded that free and protein-derived amino acids in the diet are mainly metabolized independently
Levende boerderij, lerende kinderen : beschrijving en effecten van verschillende vormen van educatie op de boerderij
Hassink, J. ; Haubenhofer, D.K. ; Meer, I.M. van der; Kamp, N. van der; Schreurs, E. ; Schuler, Y.D. - \ 2009
Wageningen : Plant Research International (Rapport / Plant Research International 257)
onderwijs - informeel onderwijs - praktijkonderwijs - voorlichting - boerderijen - nederland - milieueducatie - multifunctionele landbouw - boerderijeducatie - natuur- en milieueducatie - education - non-formal education - practical education - extension - farm dwellings - netherlands - environmental education - multifunctional agriculture - farm education - nature and environmental education
Verschillende vormen van boerderij-educatie werden onderzocht. Te weten: excursie, boerderijweek, boerderij-atelier en boerderijschool. Van elk van deze vormen is onderzocht welk effect ze hadden op de kinderen. Voor de verschillende vormen zijn aanbevelingen opgesteld die moeten leiden tot een betere benutting ervan
Dietary amino acids fed in free form or as protein do differently affect amino acid absorption in a rat everted sac model
Nolles, J.A. ; Peeters, I.G.S. ; Bremer, B.I. ; Moorman, R. ; Koopmanschap, R.E. ; Verstegen, M.W.A. ; Schreurs, V.V.A.M. - \ 2008
Journal of Animal Physiology and Animal Nutrition 92 (2008)5. - ISSN 0931-2439 - p. 529 - 537.
brush-border membrane - whole-body nitrogen - growth-performance - mouse intestine - digestion rate - milk protein - transport - metabolism - retention - ingestion
In the present study, the effect of free amino acid (FAA) diets on the intestinal absorption rate of methionine and leucine was studied 'ex vivo' with rats adapted for different periods of time to the diets, using the everted sac method. The adaptation period to the 21% FAA diet with an amino acid content based on casein was either, 0 (no adaptation, N-ADA), 5 (short-term adaptation, ST-ADA), or 26-33 days (long-term adaptation, LT-ADA). Within the ST-ADA and the LT-ADA groups, three different levels of methionine were included: 50%, 100% and 200% of the level normally present in casein. All diets were iso-nitrogenous and iso-caloric. After the adaptation period (0, 5, or 26-33 days), intestinal everted sacs were prepared. Methionine or leucine was added to the medium as transport substrate. The methionine absorption rate of the rats of the LT-ADA groups was higher than that of the N-ADA groups. Furthermore, adaptation to 200% dietary methionine levels caused a significantly slower leucine absorption compared to the 100%, and 50% group. Methionine absorption was similar in the 100% and 200% groups, but the absorption of methionine in the 50% group was enhanced in the distal part of the intestines. We concluded that in response diets with 21% FAAs as only amino acid source, amino acid absorption is decreased to avoid toxic effects of high levels of methionine in the circulation.
Op zoek naar een leuke activiteit? Educatie op de boerderij
Haubenhofer, D.K. ; Hassink, J. ; Schreurs, E. ; Schuler, Y.D. ; Kamp, N. van der - \ 2008
Ga voor gezond: nieuwsbrief 2008 (2008)Feb..
Consequences of intermittent suckling for performance in the pig
Kuller, W.I. - \ 2008
Utrecht University. Promotor(en): J.H.M. Verheijden; M.A.M. Taverne; Bas Kemp, co-promotor(en): Nicoline Nieuwenhuizen-Soede; H.M.G. van Beers-Schreurs. - - 139 p.
Tool for evaluation initiatives aiming at reducing overweight in order to generate best practices
Schreurs, M.H.G.M. ; Raaij, J.M.A. van; Bemelmans, W. ; Schuit, J. - \ 2007
Measuring intestinal blood flow in group-housed weaner pigs using Physiogear TM I: A pilot study
Berkeveld, M. ; Hendriksen, S.W.M. ; Beers-Schreurs, H.M.G. van; Koets, A.P. ; Langendijk, P. ; Essen, G.J. van; Taverne, M.A.M. ; Verheijden, J.H.M. - \ 2007
Livestock Science 108 (2007)1-3. - ISSN 1871-1413 - p. 159 - 162.
The objective of this study was to determine whether intestinal blood flow can be measured adequately in group-housed animals using the recently developed Physiogear (TM) I wireless flowmeter. We used the weaner pig as one of many possible animal models. Four 7-kg piglets were instrumented with a 3-mm flowprobe around the superior mesenteric artery (SMA) and SMA flow was measured pre- and post-weaning. During measurements, behavior was recorded. The piglets did not show any abnormal behavior and were not restrained by the flowmeter. Severe reductions (> 75%) in SMA flow coincided with nursing (pre-weaning) and aggressive behavior (post-weaning) and were only short-lived. Our results demonstrate that the Physiogear (TM) I flowmeter can be used to measure flow in group-housed animals without any human contact, providing the opportunity to relate flow measurements to undisturbed animal behavior. (c) 2007 Elsevier B.V. All rights reserved.
Mathematical analysis of human [13CO2]-breath test results: post prandial fate of amino acids is related to their ditary form.
Schreurs, V.V.A.M. ; Nolles, J.A. ; Krawielitzki, K. ; Bujko, J. - \ 2007
In: 2nd International Symposium on Energy and Protein Metabolism and Nutrition, EAAP publication 124, Vichy, France, 9 - 13 Septenber, 2007. - Wageningen, The Netherlands : Wageningen Academic Publishers - ISBN 9789086860418 - p. 237 - 238.
Energetic and metabolic consequences of aerobic and an-aerobic ATP-production.
Schreurs, V.V.A.M. ; Aarts, M.J. ; IJssennagger, N. ; Hermans, J. ; Hendriks, W.H. - \ 2007
Agro Food Industry Hi-Tech 18 (2007)5. - ISSN 1722-6996 - p. 25 - 28.
high-altitude - exercise - protein
ATP, the currency of cellular energy metabolism, can be produced during aerobic and an-aerobic oxidation of metabolic substrates. The aerobic oxidation yields CO2 + H2O as metabolic end products while ATP is produced by oxidative phosphorylation in the mitochondria. Carbohydrate, protein and fat provide a similar amount of 12-13 ATP/MJ ME when the ME is based on their value as body constituent. The energetic efficiency is 42-43 percent. In the anaerobic mode, for glucose only, ATP is produced by substrate level phosphorylation during cytoplasmic glycolysis, the normal first step in the aerobic oxidation of glucose. However, under an-aerobic conditions cytoplasmic glycolysis produces lactate which requires one of two ways of aerobic clearance to avoid lactic acidosis. The 'ketogenic clearance' re-channels the lactate in aerobic oxidation of glucose, but elsewhere in the body. This ketogenic clearance can contribute to the normal ATP-requirement of the whole body, but causes a move to carbohydrate as energy substrate. If necessary these carbohydrates can be produced from body protein, with a decrease in the energetic efficiency to 29 percent. The "glucogenic clearance" re-cycles the lactate to glucose. This glucogenic pathway (Cori cycle) further lowers the energetic efficiency of ATP-production for peripheral use to 14.1 percent. The Cori cycle requires extra ATP and causes a move to fat as energy substrate. This desk study shows that the energetic efficiency of ATP-production for peripheral use will range between 14-43 percent depending on the need and availability of glucose. It is suggested that these results could be used to develop specific nutritional, physiological and environmental strategies to benefit physical fitness and weight management in daily practice.
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