Supranormal dietary folic acid supplementation: effects on methionine metabolism in weanling rats

There are nationwide folic acid (FA) fortification programmes of staple foods established or under consideration in order to prevent neural tube defects. Universal FA fortification still remains controversial because of the concern that additional FA in the diets of population groups (e.g. children and elderly) not initially targeted for fortification may suffer adverse effects. However, dietary surveys regarding folate generally deal with adults and little is known about the consumption and long-term effects of fortified food and supplements in growing individuals. Recent reports from our laboratory show several effects of high-dose folate supplementation in rats. In the present work, we studied the effect of FA on the methionine cycle in weanling (3-week-old) male rats after 4 weeks of supplementation with 40 mg FA/kg diet v. control (1 mg FA/kg diet). FA supplementation resulted in a reduction of homocysteine and creatinine concentrations v. control group. FA supplementation did not alter S-adenosylmethionine/S-adenosylhomocysteine ratio, DNA methylation, enzymatic activities or concentrations of vitamins involved in the nutritional regulation of the methionine cycle, except for folate. FA supplementation of 40 mg/kg did not lead to hepatic or renal damage. In conclusion, there were no apparent adverse effects on one-carbon metabolism after FA supplementation in the studied conditions.     

Effect of folic acid supplementation on aluminum accumulation in rats

OBJECTIVE: Exposure to many xenobiotics may cause depletion of folic acid (folate), which is an essential vitamin for humans. Replacement of folate can be effective in protection against some diseases and in partial or total prevention of adverse effects related to xenobiotics. Aluminum (Al) is the most widely distributed metal in the outer crust of the earth. Its toxicity in humans is well known. However, there is no evidence that folate can decrease accumulation of Al to which humans can be exposed in many ways. The aim of the present study was to quantify organ Al accumulation and to evaluate whether there is any protective (or reductive) effect of folic acid on Al accumulation. METHODS: Male Wistar rats were assigned oral Al chloride (200 mg x kg(-1) x d(-1), n = 10, group 1) alone or in combination with folic acid (20 mg x kg(-1) x d(-1), n = 10, group 2) for 8 wk. At the end of the period, bone, kidney, brain, and blood samples were collected, and Al concentrations were determined by electrothermal atomic absorption spectrophotometry. RESULTS: Mean values of Al in the tissue samples from group 1 were higher than those from group 2 (all P < 0.05). No difference was observed in serum Al levels between groups (P > 0.05). CONCLUSION: These results suggest that folate supplementation might be useful to decrease Al accumulation in its main target organs, i.e., bone, kidney, and brain.     

Folate status of adolescents: effects of folic acid supplementation

This study was designed to determine the folate status of an adolescent population and to demonstrate the effect of folic acid supplementation on subjects with low folate status. In phase one, folate status was evaluated in a biracial sample of 164 adolescents 12 to 15 years old. Socioeconomic, demographic, anthropometric, and 7-day food record data were collected, and serum and erythrocyte folate levels were determined. Thirty-five adolescents considered to have had low folate status 6 months earlier participated in phase two, a 2-month supplementation period and reevaluation. No racial differences were observed in folate status, as indicated by amount of folate in the blood and diet. Boys had significantly (p less than .05) higher folate levels in serum and erythrocytes than did girls. Thirteen percent of the boys and 40% of the girls were folate deficient as judged by amount of erythrocyte folate less than 317 nmol/L (140 ng/mL). The folate-deficient subjects had significantly (p less than .05) lower values of hemoglobin than did the normal subjects. Seventeen percent of the boys and 42% of the girls had folate intakes below the recommended dietary allowance for folate. Supplementation of 400 micrograms folic acid daily for 2 months resulted in significant (P less than .05) increases in serum folate, erythrocyte folate, and hemoglobin values and a decrease in mean corpuscular volume. Evidence of high prevalence of low folate status, positive relationship between erythrocyte folate and hemoglobin, and responses of hemoglobin and mean corpuscular volume to the supplement indicated that folate consumption may not be optimal in some groups of adolescents, especially in girls.     

Low-dose folic acid supplementation does not influence plasma methionine concentrations in young non-pregnant women

An elevated plasma total homocysteine (tHcy) concentration is a risk factor for cardiovascular disease and for having offspring with a neural-tube defect. Folate is a methyl donor in the remethylation of homocysteine into methionine. Although folic acid supplementation decreases tHcy concentrations, effects of folic acid supplementation on plasma methionine concentrations are unclear. There is also concern that folic acid supplementation negatively affects vitamin B12 status. We studied effects of low-dose folic acid supplementation on methionine and vitamin B12 concentrations in plasma. We also investigated whether baseline plasma methionine and tHcy concentrations correlated with the baseline folate and vitamin B12 status. For a period of 4 weeks, 144 young women received either 500 micrograms folic acid each day, or 500 micrograms folic acid and placebo tablets on alternate days, or a placebo tablet each day. Plasma methionine, tHcy and plasma vitamin B12 concentrations were measured at start and end of the intervention period. Folic acid supplementation had no effect on plasma methionine or plasma vitamin B12 concentrations although it significantly decreased tHcy concentrations. Plasma methionine concentrations showed no correlation with either tHcy concentrations (Spearman rs-0.01, P = 0.89), or any of the blood vitamin variables at baseline. Baseline tHcy concentrations showed a slight inverse correlation with baseline concentrations of plasma vitamin B12 (rs-0.25, P < 0.001), plasma folate (rs-0.24, P < 0.01) and erythrocyte folate (rs-0.19, P < 0.05). In conclusion, low-dose folic acid supplementation did not influence plasma methionine or plasma vitamin B12 concentrations. Furthermore, no correlation between plasma methionine concentrations and the blood folate and vitamin B12 status was shown.     

Hyperhomocysteinemia and oxidative stress in hemodialysis: effects of supplementation with folic acid

This study was undertaken to evaluate two different doses of folic acid and their effects on the control of hyperhomocysteinemia, and on pro-oxidant and antioxidant changes in a group of 32 hemodialysis (HD) patients. Blood samples were collected in a group of patients at three different times: before (basal; B), after the first (S1), and after the second (S2) three-month supplementation periods, and compared to samples from a group of healthy individuals. Analysis of vitamins (C, E, folate, and B12), oxidant parameters (lipid and protein oxidation), and homocysteine were performed. Hyperhomocysteinemia of different degrees was observed in all patients on HD (45.30 +/- 24.89 microM). Oxidative stress was also detected, with lipoperoxidation and protein oxidation being associated with lower concentrations of antioxidant substances (vitamins E and C). The first folate dose (2.5 mg after each dialysis session) reduced by half the initial concentrations of homocysteine (44.92 +/- 22.05 to 20.56 +/- 6.79 microM; p < 0.05) but did not normalize its values. The second dose (15 mg) did not show an additional effect, but it was at this time that lipoperoxidation was significantly reduced, although the protein oxidation showed no change. It was concluded that the first dose of folic acid was efficient in reducing homocysteine concentrations, without normalization of values. The participation of hyperhomocysteinemia in oxidative stress appeared to be partial, but in combination with dialysis treatment, may contribute to the induction of an oxidative environment in this group. The possible antioxidant action of folate must also be considered in this case, acting directly against lipoperoxidation or through hyperhomocysteinemia control. Routine supplementations of folic acid and other antioxidant vitamins should be considered in hemodialysis in order to reduce homocysteine levels to lower values, that although not normal, may be more beneficial in minimizing the cardiovascular risk in this group.     

Dietary folic acid intake differentially affects methionine metabolism markers and hippoccampus morphology in aged rats

Purpose

Folic acid (FA) is an emerging nutritional factor in the pathogenesis of diverse neurodegenerative disorders by still unknown mechanisms. The hippocampus is altered during the loss of cognitive abilities in humans and selectively affected when homocysteine increases. The aim was to evaluate the potential protective role of folic acid in the maintenance of biochemical markers related to the methionine cycle, as well as the integrity of the hippocampus as part of the brain in aged rats.

Methods

Male Sprague–Dawley rats (18 months old) were assigned to four different folic acid groups (0 mg FA/kg diet, deficient; 2 mg FA/kg diet, control; 8 mg FA/kg diet, moderate supplementation; 40 mg FA/kg diet, extra supplementation) for 30 days. We evaluated several parameters related to the methionine cycle. In addition, hippocampus areas were immunostained for specific neuronal markers and astrocytes.

Results

Serum folate levels increased according to FA dietary level (p < 0.01). There was a significant increase in the serum homocysteine concentrations in the folic acid-deficient diet group (p < 0.01). However, brain S-adenosylmethionine and S-adenosylhomocysteine did not differ significantly between the folic acid groups. Consequently, the methylation ratio was also unchanged. The morphometric analysis did not show any differences in the number of neurons and astrocytes between groups, except when comparing the folic acid-deficient diet versus folic acid-supplemented diet in the striatum of the hippocampus.

Conclusions

Clearly, the dietary FA deficiency negatively affects the methionine metabolism biomarkers, while excessive supplementation seems to be unnecessary for optimal maintenance of the methylation cycle and hippocampus integrity.     

Sex-related differences in effect of ethanol administration and folic acid supplementation on pancreatic amylase in rats

The present study was designed to determine whether folic acid supplement is sufficient to reverse the negative effects of ethanol consumption on amylase activity during gestation, lactation, and growth. Moreover, this study investigated the sex-related differences in amylase content in the pancreatic tissue, serum, and urine. The animals were randomized into three groups: Control group (CG) received water and a basic rat diet during pregnancy, lactation, and growth; Ethanol-rats (EG) were fed an ethanol diet during pregnancy, the suckling period, and growth until death; and Ethanol + folic acid group (E + FG) were handled the same way as those of EG, except they received a folic acid supplement from reproduction until the end of experimental period. Our results showed that ethanol consumption decreased the pancreatic amylase level in offspring rats at 2 months postpartum. Folic acid supplementation did not alter pancreatic amylase activities. In offspring males, ethanol administration decreased serum amylase activity at 2 months postpartum. Folic acid supplementation in males resulted in higher serum amylase levels than those corresponding to the ethanol-fed group. In females, no significant differences between groups in serum amylase levels were found. Ethanol consumption decreased urinary amylase excretion (at 30 days and 2 months postpartum), but the folic acid-supplemented group showed a more pronounced decrease in urine amylase activity than in the ethanol-fed group. At 30 days postpartum, no sex difference in urinary amylase was identified. However, in general, males showed higher values for urine amylase than females at 2 months postpartum. A folic acid-supplemented diet exerts an advantageous effect on amylase in serum in offspring males at 2 months postpartum of mothers fed ethanol during gestation and lactation periods, because amylase renal absorption is increased. In offspring females, amylase renal absorption is also increased, but we did not observed an advantageous effect on amylase in serum. It may be that sexual differentiation in females at 2 months postpartum exerts a definitive effect on amylase in serum. We found a sex-related difference in amylase activities; therefore, we suggest that in future all results of the exocrine pancreas function, in male and female animals, be analyzed separately.     

Differential effects of fish oil and folic acid supplementation during pregnancy in rats on cognitive performance and serum glucose in their offspring

OBJECTIVE: We studied the effect of folic acid and polyunsaturated fatty acid supplementation during pregnancy in Wistar albino rats on cognitive performance and serum glucose concentrations in their pups. METHODS: Pregnant female rats from four groups (n = 6/group) were fed casein diets with 18% protein and 2 mg of folic acid/kg of diet (group I), 12% protein and no folic acid (group II), 12% protein and 8 mg of folic acid/kg of diet (group III), or 12% protein and 70 g of cod liver oil/kg of diet (group IV). All pups were weaned on standard control diet with 18% protein. Cognitive performance, brain fatty acid profile, and serum glucose concentrations were studied in offspring at age 6 mo. RESULTS: There was no significant difference in length of gestation or litter size, but the litter weight for group IV was lower (P = 0.047) than that for group I. After weaning, males in group II had lower (P < 0.05) body weights, but those in group III had weights comparable to those in group I for both sexes. In group IV, body weights were lower beyond 15 wk (P < 0.05). Relative brain weight and cognitive performance were significantly higher (P < 0.05) in group IV males and showed higher levels of brain gamma-linolenic acid. Further, these animals had serum glucose levels comparable to those of control animals at age 6 mo, whereas serum glucose levels were higher in males from groups II (P = 0.01) and III (P = 0.01). CONCLUSION: Fish oil supplementation during pregnancy improved cognitive performance and maintained glucose levels into adulthood, unlike folic acid supplementation, which supported only fetal growth and did not maintain glucose levels.     

妇女围孕期补充叶酸与多胎妊娠关系的研究进展

随机对照临床试验和人群干预试验证实,妇女围孕期增补叶酸可以降低后代神经管畸形危险性的70%～85%.1992年,美国健康与人类服务部公共卫生事务处建议：所有可能怀孕的妇女每日常规增补0.4 mg叶酸.随后,英国、加拿大等许多国家也提出了类似的建议.中国卫生部、计划生育委员会和全国妇联等有关部门和组织也在全国育龄妇女中推广增补叶酸.妇女增补叶酸预防胎儿神经管畸形应从孕前3个月开始,直至妊娠满3个月.但是,有许多妊娠不是计划的,并且准确计划妊娠是很困难的事.因此,许多妇女知道自己怀孕后才开始服用叶酸增补剂,但此时往往已经错过了预防胎儿神经管畸形的最佳时机（神经管在妊娠28天内形成）.针对这种情况,美国食品药品管理局制定了叶酸强化食品政策,要求自1998年1月1日起,所有强化食品中必须添加叶酸（140μg叶酸/100g面粉）.     

Dietary vitamin C and folic acid supplementation ameliorates the detrimental effects of heat stress in Japanese quail

We evaluated the effects of vitamin C (L-ascorbic acid) and folic acid supplementation on performance, carcass characteristics and concentrations of the oxidative stress markers [malondialdehyde (MDA), homocysteine], adrenocorticotropic hormone (ACTH), vitamins C, E, A, B-12 and folic acid, and mineral status in broiler Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature (34 degrees C, 8 h/d, 0900-1700 h). The birds (n = 150; 10-d-old) kept at 34 degrees C were fed a basal diet (HS group) or the basal diet supplemented with 250 mg of L-ascorbic acid/kg of diet (Vit C group), 1 mg of folic acid/kg of diet (FA group) or both (Vit C + FA group), whereas birds kept at 22 degrees C were fed the basal diet (TN group). Supplementing heat-stressed quail with vitamin C and folic acid improved performance compared to the HS group. Effects generally were greatest in quail supplemented with both. Although supplementation did not consistently restore concentrations to those of the TN group, it increased serum concentrations of the vitamins under study. Furthermore, serum and tissue MDA, homocysteine and ACTH concentrations were lower in the supplemented groups than in the heat-stressed controls. Retention of N, ash, Ca, P, Zn, Fe, Cu and Cr were highest in the Vit C + FA group and lowest in the HS group (P < 0.05). The results of the study indicate that vitamin C and folic acid supplementation attenuates the decline in performance and antioxidant status caused by heat stress. Such supplementation may offer protection against heat stress-related depression in performance of Japanese quail.     

The effect of docosahexaenoic acid and folic acid supplementation on placental apoptosis and proliferation

The hypothesis was tested that the additional dietary uptake of n-3 fatty acids, in particular of DHA and 5-methyltetrahydrofolate (5-MTHF), during the second half of pregnancy would influence proliferation and apoptosis in the full-term human placenta. The diets of pregnant women from Spain (n 55) were supplemented with modified fish oil and/or 5-MTHF or placebo, and assigned in a random, double-blind manner to one of the four groups. Immunohistochemistry and immunoblotting were used to detect placental proliferation and apoptosis with monoclonal antibodies for key proteins that reflected the extent of both processes: proliferation cell nuclear antigen (PCNA), p53, cytokeratin 18 neoepitope. The PCNA level in the fish oil/5-MTHF-treated group was higher by 66 % (P < 0.05) than that of the placebo group, whereas the levels of p53 and cytokeratin 18 neoepitope were unaffected by treatment. PCNA expression was altered only in the trophoblast compartment (placebo 11.1 (se 0.5) % v. combination 21.5 (se 1.2) %; P < 0.05), whereas the proportion of nuclei stained in endothelial and other stromal cells was similar in the placebo and combined treatment groups. No correlation was found between fish oil or 5-MTHF supplementation and the levels of the proteins. The present data suggest that supplementation with fish oil and/or 5-MTHF had no effect on the parameters reflecting placental proliferation and apoptosis. A defined combination of DHA and 5-MTHF may, however, affect placental proliferation.     

Effect of folic acid supplementation on mood and serotonin response in healthy males

Evidence suggests that low folate status may be detrimental to mood and associated with depleted cerebrospinal fluid levels of the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT). A placebo-controlled trial was carried out to determine the effect of folic acid supplementation (100 microg for 6 weeks followed by 200 microg for a further 6 weeks) upon subjective mood (Positive and Negative Affect Schedule) and biochemical markers of mood (5-HT) in healthy males (n 23). Blood samples were obtained at baseline (week 0) and during the intervention at week 6 and week 12. Subjective mood assessments were obtained at week 0 and week 12. The results showed an increase in serum and erythrocyte folate concentrations (P=0.02 and P=0.003, respectively) and a corresponding decrease in plasma homocysteine (P=0.015) in response to the folic acid intervention. Neither subjective mood nor 5-HT levels, however, were significantly altered in response to the change in folate status. Folic acid given at physiological doses did not appear to improve the mood of healthy folate-replete individuals over a 12-week period. Further research is needed to address the effect of folic acid supplementation or of longer duration or increased dose, particularly in the face of sub-optimal folate status.     

Frequency of hyperhomocysteinemia in hemodialysis patients with folic acid supplementation

BACKGROUND: It is known that hyperhomocystinemia is an independent risk factor for development of atherosclerosis. In end stage renal disease the frequency of hyperhomocystinemia is much greater than in normal populations. AIM: In this study homocystein (Hcy), folic acid and vitamin B12 concentrations were determined in 125 chronic renal failure patients being on folic acid supplementation (3 mg/day). In 107 patients the frequency of C667T polymorphism of methylene tetrahyrofolate reductase (MTHFR) was also determined. The relationships between these parameters were also studied. RESULTS: It was found that in these patients who are under continuous folic acid supplementation the mean level of homocysteine was 16.8 +/- 7.2 mumol/L, a value considerably lower than the homocysteine concentration reported for non-supplemented patients. The elevation of homocysteine concentrations was independent of gender, time spent in renal replacement therapy, and the type of renal replacement therapy (hemodialysis: 17.6 +/- 12.6; hemodiafiltration: 16.6 +/- 12.9 mumol/L). Data showed an inverse relation between plasma homocysteine concentrations and the concentrations of folic acid and vitamin B12. Moderately severe hyperhomocystinemia (Hcy > 20 mumol/L) was found in about 30% of patients. In those the frequency of patients for homozygous T677 allele of MTHFR was about 25-30%. However, in all ESRD patients the frequency of the homozygotes was the same then in the normal population. Homocysteine plasma levels correlated with MTHFR polymorphism: in the wild type group Hcy was 14 +/- 7 mumol/L, in the heterozygous group was 17.2 +/- 6.2 mumol/L, and in the homozygous group was 21 +/- 19 mumol/L. CONCLUSIONS: Long-term folic acid supplementation decreased the homocysteine level in end stage renal disease patients. However, in folic acid resistant group, who were in 30% homozygotes for C667T of MTHFR (suggesting that homocysteine-methionine remethylation cycle is disturbed), instead of the administration of folic acid, methylene tetrahydrofolate supplementation might be considered.     

Effect of maternal folic acid supplementation on hepatic proteome in newborn piglets

ObjectiveThe objective of this study was to investigate the changes in the hepatic proteome of newborn piglets after maternal folic acid supplementation (FS).MethodsPregnant dams were fed a control diet (folic acid 1.3 mg/kg) or an FS diet (folic acid 30 mg/kg) during gestation. The liver samples of newborn piglets from each group were collected at birth for the analysis of the proteome using two-dimensional difference gel electrophoresis.ResultsThe results indicated that the expression levels of 11 proteins were changed dramatically in the newborn piglets after maternal FS. FS during gestation increased the content of proteins that regulate the immune response (90-kDa heat shock protein), energy metabolism (aconitase and succinate dehydrogenase), and intermediary metabolism (formiminotransferase cyclodeaminase and abhydrolase). In addition, maternal FS downregulated the expression of proteins associated with cellular signal transduction (heterogeneous nuclear ribonucleoprotein and exportin), proteolysis (ubiquitin-conjugating enzyme and porcine ε-trypsin), and cell migration regulation (actin-related protein-3).ConclusionThese findings suggest that maternal FS alters the expression abundance of several hepatic proteins that are involved in metabolic regulation, oxidative responses, and cancer-related processes.     

孕期补充叶酸及微量元素对妊娠结局的影响

目的分析甘肃省定西市安定区孕期女性补充叶酸及微量元素对妊娠结局的影响。方法选择定西市安定区孕妇3 089例,获得妊娠结局的为2 994例,根据叶酸及微量元素的情况分为未增补组、单纯孕前期增补组、孕早期增补组、规范增补组,分析各组新生儿体格发育指标、体质量分布情况、孕妇巨幼红细胞性贫血及神经管畸形发生情况。结果单纯孕前期增补组身长、头围、胸围较未增补组未见显著性差异(P0.05),孕早期增补组身长、头围较未增补组显著性升高(P0.05),规范增补组身长、头围、胸围较未增补组均有显著增加(P0.05)。单纯孕前期增补组体质量分布较未增补组未见显著性差异(χ2=5.127,P0.05),孕早期增补组及规范增补组体质量分布较未增补组显著性升高(χ2=21.139、19.076,P0.05)。单纯孕前期增补组巨幼红细胞性贫血及神经管畸形较未增补组未见显著性差异(χ2=4.086,P0.05),孕早期增补组及规范增补组巨幼红细胞性贫血、神经管畸形较未增补组显著性下降(χ2=18.095、22.143,P0.05)。结论叶酸及微量元素补充是否规范直接关系到妊娠结局,应规范化对育龄期妇女进行叶酸及微量元素补充。     

围孕期补充叶酸的益处及疑惑

目前叶酸对围孕期的重要作用已得到广泛关注,但对于围孕期补充叶酸的益处、安全性等方面仍存在一些疑惑。本文简要综述了叶酸对先天畸形和妊娠结局的影响,叶酸补充的推荐剂量,体内叶酸状态监测以及补充叶酸时肿瘤、维生素B12缺乏和双胎的影响,为围孕期妇女补充叶酸提供参考。     

妇女妊娠前后增补叶酸预防神经管畸形的成本效果分析

目的：对我国妇女妊娠前后服用叶酸预防神经管畸形干预进行成本效果评价。方法：从社会的角度，构建决策树进行成本效果分析，并进行敏感性分析。结果：全国普遍实施增补叶酸干预的方案（FA2）和北方普遍干预且南方农村干预的方案（FA4）效果较好，敏感性分析显示疾病发生率、干预成本等因素影响其成本效果。结论：该干预是一项具有成本效果的预防技术，其中以北方普遍干预而南方农村干预方案的效果和成本效果较佳。