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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    Effects of cultivation conditions on folate production by lactic acid bacteria
    Sybesma, W. ; Starrenburg, M. ; Tijsseling, L. ; Hoefnagel, M.H.N. ; Hugenholtz, J. - \ 2003
    Applied and Environmental Microbiology 69 (2003)8. - ISSN 0099-2240 - p. 4542 - 4548.
    gtp cyclohydrolase-i - neural-tube defects - folic-acid - streptococcus-lactis - lactococcus-lactis - enzymatic-synthesis - purification - homocysteine - biosynthesis - strain
    A variety of lactic acid bacteria were screened for their ability to produce folate intracellularly and/or extracellularly. Lactococcus lactis, Streptococcus thermophilus, and Leuconostoc spp. all produced folate, while most Lactobacillus spp., with the exception of Lactobacillus plantarum, were not able to produce folate. Folate production was further investigated in L. lactis as a model organism for metabolic engineering and in S. thermophilus for direct translation to (dairy) applications. For both these two lactic acid bacteria, an inverse relationship was observed between growth rate and folate production. When cultures were grown at inhibitory concentrations of antibiotics or salt or when the bacteria were subjected to low growth rates in chemostat cultures, folate levels in the cultures were increased relative to cell mass and (lactic) acid production. S. thermophilus excreted more folate than L. lactis, presumably as a result of differences in the number of glutamyl residues of the folate produced. In S. thermophilus 5,10-methenyl and 5-formyl tetrahydrofolate were detected as the major folate derivatives, both containing three glutamyl residues, while in L. lactis 5,10-methenyl and 10-formyl tetrahydrofolate were found, both with either four, five, or six glutamyl residues. Excretion of folate was stimulated at lower pH in S. thermophilus, but pH had no effect on folate excretion by L. lactis. Finally, several environmental parameters that influence folate production in these lactic acid bacteria were observed; high external pH increased folate production and the addition of p-aminobenzoic acid stimulated folate production, while high tyrosine concentrations led to decreased folate biosynthesis
    Increased production of folate by metabolic engineering of Lactococcus lactis
    Sybesma, W.F.H. ; Starrenburg, M. ; Kleerebezem, M. ; Mierau, I. ; Vos, W.M. de; Hugenholtz, J. - \ 2003
    Applied and Environmental Microbiology 69 (2003). - ISSN 0099-2240 - p. 3069 - 3076.
    controlled gene-expression - folic-acid - streptococcus-thermophilus - dihydropteroate synthase - subsp cremoris - cloning - bacteria - disease - homocysteine - inhibition
    The dairy starter bacterium Lactococcus lactis is able to synthesize folate and accumulates large amounts of folate, predominantly in the polyglutamyl form. Only small amounts of the produced folate are released in the extracellular medium. Five genes involved in folate biosynthesis were identified in a folate gene cluster in L. lactis MG1363: folA, folB, folKE, folP, and folC. The gene folKE encodes the biprotein 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine pyrophosphokinase and GTP cyclohydrolase I. The overexpression of folKE in L. lactis was found to increase the extracellular folate production almost 10-fold, while the total folate production increased almost 3-fold. The controlled combined overexpression of folKE and folC, encoding polyglutamyl folate synthetase, increased the retention of folate in the cell. The cloning and overexpression of folA, encoding dihydrofolate reductase, decreased the folate production twofold, suggesting a feedback inhibition of reduced folates on folate biosynthesis.
    Bioaccessibility of Folic Acid and (6S)-5-Methyltetrahydrofolate Decreases after the Addiction of Folate-Binding Protein to Yogurt as Studied in a Dynamic In Vitro Gastrointestinal Model
    Arkbåge, K. ; Verwei, M. ; Havenaar, R. ; Witthöft, C. - \ 2003
    The Journal of Nutrition 133 (2003)11. - ISSN 0022-3166 - p. 3678 - 3683.
    neural-tube defects - small-intestine - cows milk - bovine-milk - 5-methyltetrahydrofolate - bioavailability - absorption - homocysteine - transport - diets
    Milk products are only moderate sources of folate. Nevertheless, they are of interest due to their content of folate-binding proteins (FBP), which in some studies have been reported to increase folate bioavailability. The effect of FBP on folate bioavailability has been widely discussed. The aim of this study was to investigate the bioaccessibility of folic acid and (6S)-5- methyltetrahydrofolate (5-CH3-H(4)folate) from fortified yogurt using a dynamic in vitro gastrointestinal model (TIM). In addition, the effect of FBP on folate bioaccessibility and the stability of FBP added to yogurt during gastrointestinal passage were investigated. Folate bioaccessibility was 82% from yogurt fortified with folic acid and 5-CH3-H(4)folate. The addition of FBP to yogurt decreased (P <0.05) folate bioaccessibility. The lowering effect of FBP was more pronounced in yogurt fortified with folic acid (34% folate bioaccessibility) than from yogurt fortified with 5-CH3-H(4)folate (57% folate bioaccessibility). After gastrointestinal passage, 17% of the FBP in yogurt fortified with 5-CH3-H(4)folate and 34% of the FBP in yogurt fortified with folic acid were recovered. No difference in folate bioaccessibility was found between folate-fortified yogurt and folate-fortified pasteurized milk (P = 0.10), whereas the lowering effect of FBP was (P <0.05) greater in yogurt compared with pasteurized milk. In conclusion, based on the high bioaccessibility of folic acid and 5-CH3-H(4)folate, yogurt without active FBP can be considered to be an appropriate food matrix for folate fortification.
    Vitamin B12 status is associated to bone mineral content and bone mineral density in frail elderly women, but not in men
    Dhonukshe-Rutten, R.A.M. ; Lips, M. ; Jong, N. ; Chin A Paw, M.J.M. ; Hiddink, G.J. ; Dusseldorp, M. van; Groot, C.P.G.M. de; Staveren, W.A. van - \ 2003
    The Journal of Nutrition 133 (2003)3. - ISSN 0022-3166 - p. 801 - 807.
    physical-activity scale - methylmalonic acid - osteoporosis - determinants - nutrition - exercise - mass - absorptiometry - homocysteine - vegetarian
    Subclinical vitamin B-12 deficiency is common in the elderly. Encouraged by early indications, we investigated the plasma vitamin B-12 status in association with bone mineral content (BMC) and bone mineral density (BMD) in frail elderly people. Data of 194 free-living Dutch frail elderly (143 women and 51 men) were available. BMC and BMD were measured by dual energy X-ray analysis. Biochemical analyses were performed on plasma or serum including vitamin B-12, methylmalonic acid, homocysteine, 25-hydroxy vitamin D and parathyroid hormone. Women had higher plasma vitamin B-12 (288 and 238 pmol/L, respectively) and lower plasma homocysteine levels (15.8 and 21.3 mumol/L, respectively) than men. Of the total explained variance of BMC and BMD in women (46 and 22%, respectively), 1.3-3.1% was explained by plasma vitamin B-12, in addition to weight and height or energy intake. In men, the variance of BMC and BMD was explained by weight, smoking and/or height (total R-2 was 53 and 25%, respectively), but not by plasma vitamin B-12. Osteoporosis occurred more often among women whose vitamin B-12 status was considered marginal or deficient than in women with a normal status, i.e., the prevalence odds ratios (after adjustment for weight, age and calcium intake) (95% confidence intervals) were 4.5 (0.8;24.8) and 6.9 (1.2;39.4), respectively. These results suggest that vitamin B-12 status is associated with bone health in elderly women. Future studies on bone health should take into account a possible role of vitamin B-12 status in different populations.
    Homocysteine and coronary heart disease : the role of polymorphic genes and hemostasis
    Klerk, M. - \ 2002
    Wageningen University. Promotor(en): F.J. Kok; E.G. Schouten; P. Verhoef. - S.l. : S.n. - ISBN 9789058087737 - 145
    hartziekten - homocysteïne - genetische polymorfie - hemostase - heart diseases - homocysteine - genetic polymorphism - haemostasis

    Background Homocysteine is a sulfur-containing amino acid formed during catabolism of the essential amino acid methionine. Defects in genes encoding enzymes or sub-optimal intake of B-vitamins (e.g. folate) involved in homocysteine metabolism can lead to cellular accumulation of homocysteine resulting in elevated plasma levels. Numerous epidemiological studies have shown a positive association between elevated homocysteine levels and cardiovascular disease (CVD) risk. However, whether elevated homocysteine is a causal risk factor of CVD is still under debate. In addition, the pathogenic mechanism through which homocysteine would increase CVD risk is still unclear, but one of the proposed mechanisms is that homocysteine would impair hemostasis .

    Methods The epidemiological studies described in this thesis explored the evidence with respect to a causal role of homocysteine in the occurrence of coronary heart disease (CHD) by investigating the association of polymorphic genes with risk of CHD. Two placebo-controlled intervention studies on homocysteine lowering in humans investigated the role of hemostasis as a potential mechanism.

    Results In a meta-analysis we showed that homozygosity for the 677C>T mutation in the gene encoding methylenetetrahydrofolate reductase (MTHFR), an enzyme involved in homocysteine remethylation, was associated with a higher risk of CHD, however only when folate status was low. This might explain why the mutation was associated with increased CHD risk in Europe, but not in North America, where folate intake is higher because of widespread use of vitamin supplements and folate fortification. In a case-control study, we observed an increased risk of CHD for individuals who were homozygous for the 2756A>G mutation in the gene encoding methionine synthase (MS), another enzyme involved in homocysteine remethylation. However, this could not be confirmed by the majority of other published case-control studies. In two trials, B-vitamin or folic acid supplementation had no clear beneficial effect on markers of hemostasis, despite a marked reduction in homocysteine concentrations was observed.

    Conclusions The result of our meta-analysis on the MTHFR 677C>T polymorphism and CHD supports the hypothesis that impaired folate metabolism, leading to high homocysteine concentrations, is causally related to CHD risk. The meta-analysis could not reveal whether it is elevated homocysteine, low folate or impaired methylation that is the true cause of CHD. However, our results suggest that increasing population mean levels of folate would reduce the incidence of CHD. This could be achieved by improving the bioavailability of folate from foods and additional food fortification with folic acid. Provided the folate status is adequate, there is little additional value of screening for MTHFR 677C>T genotype. Homocysteine-lowering through B-vitamin supplementation does not seem to affect hemostasis in healthy volunteers. More research is needed to unravel the pathogenic mechanism.

    Bioavailability of flavonoids and cinnamic acids and their effect on plasma homosysteine in humans
    Olthof, M.R. - \ 2001
    Wageningen University. Promotor(en): M.B. Katan; P.C.H. Hollman. - S.l. : S.n. - ISBN 9789058084170 - 135
    flavonoïden - kaneelzuur - homocysteïne - bloedplasma - biologische beschikbaarheid - mens - quercetine - theaflavine - chlorogeenzuur - hart- en vaatziekten - flavonoids - cinnamic acid - homocysteine - blood plasma - bioavailability - man - quercetin - theaflavine - chlorogenic acid - cardiovascular diseases

    Dietary antioxidants might prevent oxidative damage to tissues and therefore protect against cardiovascular disease and cancer. Dietary phenols are strong antioxidants in vitro but their role in vivo is uncertain. Furthermore, there are only limited data on their bioavailability in humans. The aim of this thesis was to investigate whether bioavailability data on flavonoids and cinnamic acids support the hypothesis that they can affect health in humans . Because the group of phenols in foods is huge, we focussed our research on major phenols in foods; the flavonol quercetin, black tea phenols and chlorogenic acid (5-caffeoylquinic acid). We studied their bioavailability and effect on plasma homocysteine in humans, a potential risk factor for cardiovascular disease.

    The bioavailability of quercetin and chlorogenic acid depends upon their conjugated moieties. Hollman et al. found that the bioavailability of quercetin-3-rutinoside, a major flavonol in tea, was only 20% of that of quercetin-4'-glucoside. We found that transformation of quercetin-3-rutinoside into quercetin-3-glucoside will improve its bioavailability because the 3-glucoside had the same high bioavailability as the 4'-glucoside. Caffeic acid is a major phenol in coffee, but it is present as a conjugate with quinic acid, called chlorogenic acid. We found that the conjugation of caffeic acid with quinic acid hinders absorption in humans: absorption of chlorogenic acid was only 30% of that of its caffeic acid moiety.

    Furthermore, we found that chlorogenic acid, black tea solids and quercetin-3-rutinoside are extensively metabolized in the human body, mainly before they reach the circulation. Their metabolites have no, or less, antioxidant activity in vitro than their parent phenols. Therefore the role of dietary phenols as antioxidants in vivo might be less important than suggested by their in vitro antioxidant activity.

    Coffee consumption increases plasma homocysteine, a potential risk factor for cardiovascular disease. Chlorogenic acid from coffee is partly responsible for the homocysteine-raising effect of coffee, because we found that it increased plasma homocysteine. Black tea solids also raised plasma homocysteine, whereas quercetin-3-rutinoside did not. Furthermore, we found that glycination of metabolites of phenols in the body is not involved in the homocysteine-raising effect of phenols.

    In conclusion, chlorogenic acid, tea phenols and quercetin are available in the human body, but their effects on health are uncertain. Further research on bioavailability and health effects of dietary phenols is needed.

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