![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
4 Institute of Human Nutrition, 5 Development and Cell Biology, and 6 Institute of Developmental Sciences, University of Southampton, Southampton SO16 6YD, UK
* To whom correspondence should be addressed. E-mail: g.c.burdge{at}southampton.ac.uk
 |
ABSTRACT |
|---|
 TOP ABSTRACT IntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
and glucocorticoid receptor promoter methylation increased in liver and insulin receptor promoter methylation decreased in liver and adipose tissue in FS compared with AF offspring, with reciprocal changes in mRNA expression irrespective of maternal diet. These findings show that increased folic acid intake during the JP period did not simply reverse the phenotype induced by the maternal diet. This may represent a period of plasticity when specific nutrient intakes may alter the phenotype of the offspring through epigenetic changes in specific genes.
|
Introduction |
|---|
|
TOPABSTRACTIntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
Moderate maternal dietary protein restriction in rats is a well-established model of induction of an altered phenotype in the offspring (7). The offspring are characterized by persistent hypertension (7,8), dyslipidemia, and impaired glucose metabolism (4). Supplementation of the maternal protein-restricted (PR)7 diet with folic acid or glycine prevents induction of hypertension and endothelial dysfunction in the offspring (9,10), indicating that 1-carbon metabolism is central to the mechanism underlying induction of an altered phenotype. However, increasing the folic acid content of a protein-sufficient maternal diet also induced dyslipidemia and hyperglycemia in the offspring (11). This suggests that the nature of the induced phenotype is contingent upon the nutrient balance of the maternal diet.
Persistent changes in metabolism imply stable alterations to gene transcription. Epigenetic regulation of individual genes during specific periods in the developmental program, primarily by modification of the DNA methylation status of specific cytosines in CpG dinucleotides within their 5'-regulatory regions confers such stable changes in the level of transcription (12). However, stability of the epigenome is reduced during specific periods during the life course that are associated with more intensive changes in tissue function, namely prenatal and neonatal development, puberty, and aging (13). In rodents, manipulation of maternal dietary intakes of folic acid and methyl donors (14), differences in maternal nursing behavior (15), and constricted uterine blood flow (16) induce an altered phenotype in the offspring. We have shown that induction of an altered phenotype by a maternal PR diet during pregnancy involves changes in the epigenetic regulation by DNA methylation (17–20) and by covalent modifications of histones of specific genes, including the glucocorticoid receptor (GR) and PPAR in the liver of juvenile (17) and adult offspring (18). Such epigenetic changes are associated with altered mRNA expression of these genes and of their target genes. Induction of hypomethylation of GR involves downregulation of DNA methyltransferase (Dnmt)-1 mRNA expression and reduced binding to the GR110 promoter (20). This suggests that hypomethylation of the PPAR and GR promoters may involve progressive loss of methyl groups from CpG dinucleotides following mitosis rather than active demethylation (18). These epigenetic changes and altered Dnmt-1 expression were prevented by increasing the folic acid content of the maternal PR diet (17–19).
There is some information that changes in phenotype induced by nutritional constraint during early life can be reversed by subsequent interventions. Vickers et al. (21) have shown that leptin administration to neonatal rats reversed metabolic dysregulation induced by global maternal undernutrition during pregnancy. It is not known whether phenotypes induced by nutritional constraint during pregnancy can be reversed by dietary manipulation after the neonatal period. Folic acid supplementation in pubertal (22) and aging (23) rats altered hepatic whole-genome DNA methylation, although the effect on the epigenetic regulation of individual genes was not reported. Because the stability of the epigenome is decreased during the pubertal period (13), interventions during this time may have the potential to modify phenotypes induced in early life and so change life-long risk of disease. We therefore, tested in rats the hypothesis that increasing folic acid intake of the offspring during their juvenile-pubertal (JP) period could reverse the phenotype and epigenotype induced by the maternal PR diet. Puberty occurs at about postnatal (pn) d 40 in male rats (24) and d 35 in female rats (25). Offspring of control (C) or PR dams were fed a folic acid-adequate (AF) or -supplemented (FS) diet from weaning on d 28 until d 56. Because increased fat intake after weaning exasperates the effect of the maternal PR diet on fat and glucose metabolism (11), offspring were then challenged with a high-fat diet for a further 28 d. We measured the effect of the maternal and JP diets on growth and on markers of lipid and glucose metabolism and on the epigenetic regulation of candidate genes in liver, skeletal muscle, and adipose tissue.
|
Materials and Methods |
|---|
|
TOPABSTRACTIntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
1400 h. Liver, mesenteric adipose tissue, and biceps femoris muscle from the posterior right leg were collected and frozen immediately in liquid nitrogen and stored at –80°C. Blood was collected by cardiac puncture into tubes containing lithium heparin, and plasma was separated from cells by centrifugation and stored at –20°C. Samples from 10 male or female rats in each dietary group were selected for measurements of metabolite concentrations in plasma and for molecular biology analysis. Measurement of metabolites in plasma. Plasma triglyceride (TAG), nonesterified fatty acid (NEFA), β-hydroxybutyrate (βHB), cholesterol, and glucose concentrations were measured using a Konelab 20 autoanalyzer (27).
Measurement of TAG concentration in liver. Liver TAG concentration was measured by GC (28,29) using triheptadecanoin as internal standard on a 6890 gas chromatograph (Agilent) equipped with a 30-m x 0.25-µm x 0.25-mm BPX-70 fused silica capillary column and flame ionization detection.
Measurement of mRNA expression by real-time RT-PCR. Measurement of the levels of specific mRNA transcripts was carried out using the primers listed (Supplemental Table 2). Total RNA was isolated from liver, adipose tissue, and skeletal muscle using Tri Reagent (Sigma) according to the manufacturer's instructions. cDNA was prepared and amplified using real-time RT-PCR (18,30). Samples were analyzed in duplicate and the expression of the individual transcripts were normalized to tissue-specific housekeeping genes, which did not differ in transcript level between groups of offspring (Supplemental Table 2) (18,31).
Measurement of DNA methylation of specific genes by real-time PCR.
DNA methylation was conducted using the PCR primers listed (Supplemental Table 2). Genomic DNA was isolated from liver and muscle as described (17) and from adipose tissue using the Wizard SV Genomic DNA Purification system (Promega). Purified DNA was incubated with the methylation-sensitive restriction endonucleases AciI and HpaII according to the manufacturer's instructions (New England Biolabs) (17,18). The resulting DNA was amplified in duplicate using real-time PCR. A region of the PPAR
2 promoter that does not contain AciI or HpaII cleavage sites was used as an internal control (17,18).
Statistical analysis. Data are presented as mean ± 1 SD. Because the PCR measurements of samples from male and female offspring could not be compared directly, all other outcome variables were analyzed separately for males and females. The effect of the different dietary regimens on change in body weight over time was assessed using a general linear model with time as a repeated measure and maternal diet and JP diet as fixed factors with weight at weaning as a covariate. Post hoc comparisons were by Bonferroni's method. Comparisons between groups of the effect of different dietary regimens were by a general linear model with maternal diet and JP diet as fixed factors and Bonferroni's post hoc correction for multiple comparisons.
|
Results |
|---|
|
TOPABSTRACTIntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
Liver weight and hepatic TAG concentration.
The JP diet affected liver weight and liver weight as a proportion of body weight in male offspring but not in females (Table 1). There was no effect of maternal diet or interaction between maternal and JP diet in either males or females. The livers of male C/FS and PR/FS offspring were significantly heavier (25%) and weighed more as a proportion of body weight (20%) than in C/AF and PR/AF offspring. The JP diet affected liver TAG concentration in males and females, but there was no effect of maternal diet or interaction between maternal diet and JP diet (Table 1). In males and females, liver TAG concentrations were greater in C/FS than C/AF offspring and in the PR/FS than PR/AF offspring.
|
In females, maternal diet affected plasma TAG and NEFA concentrations such that these metabolites were significantly higher in PR/AF than in C/AF offspring (Table 1). The plasma βHB concentration was significantly higher in PR/AF than in C/AF offspring. Plasma TAG and NEFA concentrations were significantly higher in C/FS and PR/FS offspring than in C/AF and PR/AF offspring, whereas the βHB concentration was lower than in C/AF and PR/AF offspring (Table 1). Maternal diet or JP diet did not affect plasma cholesterol or glucose concentrations.
mRNA expression of specific genes in liver.
It was not possible to compare the level of expression or DNA methylation between males and females in the same PCR and so results are presented relative to the C/AF group for each sex. The effects of maternal and JP diet on mRNA expression are summarized (Tables 2 and 3). Hepatic PPAR, acyl-CoA oxidase (AOX), carnitine-palmitoyl transferase (CPT-1), GR and phosphoenolpyruvate carboxykinase (PEPCK) expression were higher in male PR/AF offspring than in C/AF offspring (Table 2). The expression of these genes did not differ between the C/FS and PR/FS offspring. However, PPAR, AOX, and CPT-1 mRNA levels were lower in male C/FS and PR/FS than in C/AF and PR/AF offspring. In contrast, GR and PEPCK expression was higher in C/FS and PR/FS offspring than in C/AF offspring but were expressed at a similar level to PR/AF offspring (Table 2). Insulin receptor (IR) expression was higher in FS offspring than in AF offspring but did not differ between maternal dietary groups (Table 2).
|
|
, AOX, CPT-1, GR, and PEPCK expression was significantly higher in livers of female PR/AF offspring than in C/AF offspring (Table 3). The expression of these genes did not differ between C/FS and PR/FS offspring. PPAR, AOX, and CPT-1 mRNA levels were lower in female C/FS and PR/FS offspring than in C/AF and PR/AF offspring. GR expression was higher in C/FS and PR/FS than in C/AF offspring but at a similar level to PR/AF offspring (Table 3). PEPCK mRNA levels were higher in C/FS and PR/FS offspring than C/AF offspring but were lower than in PR/AF offspring. IR mRNA expression did not differ significantly between PR and C offspring. However, the level of IR mRNA was significantly higher in FS offspring than in C/AF offspring (Table 3).
mRNA expression of specific genes in adipose tissue.
Maternal diet did not affect PPAR2, lipoprotein lipase (LPL), or IR expression in adipose tissue in male or female offspring, although hormone-sensitive lipase (HSL) expression in PR/AF offspring tended be higher (P < 0.1) than in C/AF offspring (Tables 2 and 3). PPAR2 and IR mRNA levels were higher in C/FS and PR/FS male and female offspring than in C/AF and PR/AF offspring (Tables 2 and 3), but HSL expression was lower in C/FS and PR/FS offspring than in C/AF male and female offspring (Tables 2 and 3). LPL mRNA expression was higher in C/FS and PR/FS male offspring than in C/AF and PR/AF offspring but did not differ between C/AF female offspring and FS offspring (Tables 2 and 3).
mRNA expression of specific genes in skeletal muscle.
In skeletal muscle, PPAR, AOX, and CPT-1 expression did not differ significantly between male and female PR/AF offspring or between C/FS and PR/FS offspring (Tables 2 and 3). The mRNA levels of PPAR and AOX were significantly higher in FS offspring than in AF offspring, but CPT-1 expression did not differ between these groups (Tables 2 and 3). LPL mRNA expression did not differ between maternal dietary or JP dietary groups in male offspring but was significantly lower in female PR/FS offspring than in C/AF offspring (Tables 2 and 3).
DNA methylation status of specific genes in liver and adipose tissue.
In males and females, the maternal diet affected hepatic PPAR and GR, but not IR or methylation and the JP diet affected PPAR, IR, and GR methylation (Table 4). In male and female liver, PPAR methylation was significantly lower in PR/AF than C/AF offspring but was greater in FS than C/AF offspring (Table 4). GR promoter methylation was significantly lower in PR/AF and FS offspring than in C/AF offspring (Table 4). IR methylation was lower in FS male and female offspring than in C/AF offspring (Table 4).
|
|
Discussion |
|---|
|
TOPABSTRACTIntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
Although the maternal dietary groups did not differ in offspring weight gain after weaning, folic acid supplementation increased weight gain in both male and female offspring. Because increased growth started during the pubertal period, this suggests that the JP period is one of plasticity in the regulation of weight gain, which responds positively to increased folic acid intake. Puberty in rats and humans is preceded by a proliferation of preadipocytes (32,33). One possible mechanism by which folic acid supplementation may increase weight gain is by increasing the formation of adipocytes. This is consistent with upregulation in the FS offspring of PPAR2 expression, which induces adipogenesis (34).
The coordinated activities of metabolic pathways in liver, skeletal muscle, and adipose tissue are critical for maintaining lipid and glucose homeostasis. We therefore measured the epigenetic regulation and mRNA expression of candidate genes in each of these tissues. We did not attempt to provide a comprehensive assessment of the changes in metabolic pathways that underlie the induced phenotypes. The changes in mRNA expression and DNA methylation of hepatic PPAR and GR and in the mRNA levels of their respective targets AOX and CPT-1, and PEPCK in the PR/AF offspring are consistent with our previous findings (20,17,19,18) and, together with higher plasma βHB concentrations, suggests increased capacity for fatty acid β-oxidation. The absence of an effect of maternal diet on glucose concentration suggests that the increased GR and PEPCK expression was a relatively minor determinant of plasma glucose. PPAR2 and LPL mRNA expression in adipose tissue and PPAR, CPT-1, and AOX expression in skeletal muscle were not altered in the PR/AF offspring, indicating differential sensitivity of liver, adipose tissue, and skeletal muscle to induction of altered transcription by maternal protein restriction.
JP folic acid supplementation induced differential changes in the methylation status and/or mRNA expression of individual genes that were associated with a shift in lipid metabolism in the food-deprived state. These are summarized in the model presented in Figure 1. In adipose tissue, the changes in PPAR2, IR, LPL, and HSL mRNA expression suggest that JP folic acid supplementation increased capacity for deposition of fatty acids in adipocytes, which is consistent with greater weight gain. Downregulation of HSL and increased LPL expression may reflect increased IR mRNA levels leading to upregulation of the insulin signaling pathway. Although HSL expression was reduced, the plasma NEFA concentration tended to be higher in FS offspring. One possible explanation is that greater fat mass and inefficient entrapment of fatty acids from TAG-rich lipoproteins (35) would tend to increase NEFA flux to the liver.
|
and of the target genes AOX and CPT-1 and suggests constraint in hepatic fatty acid β-oxidation (Fig. 1). Deposition of TAG in liver and increased plasma TAG concentration is consistent with constraint in fatty acid β-oxidation and a shift in fatty acid metabolism toward TAG synthesis, which may be exacerbated by increased NEFA flux. Reduced intakes of folic acid or 1-carbon donors are associated with fatty liver due to reduced phosphatidylcholine synthesis, which is required for VLDL secretion (36,37). Our results suggest that increased folic acid intake after weaning can also induce fatty liver by altering the metabolic partitioning of fatty acids from β-oxidation toward TAG synthesis. Thus, FS supplementation appears to induce opposite changes in equivalent metabolic pathways in different tissues.
PPAR expression is directionally dependent upon the methylation status of its promoter (17,38). Thus, hypermethylation of the PPAR promoter is consistent with its lower expression. In contrast, the methylation status and expression of GR and mRNA expression of PEPCK in FS offspring was similar to PR/AF. Thus, within a single tissue, increased JP folic acid intake induces gene-specific changes in promoter methylation and expression, although the mechanism for such targeting is not known. Furthermore, in skeletal muscle from FS offspring, increased PPAR and AOX expression suggests upregulation of peroxisomal β-oxidation, which suggests the in JP animals, the effects of folic acid supplementation differ between tissues.
Overall, these findings suggest that increased folic acid intake in the JP period induced a change in the partitioning of fatty acids between different metabolic fates. It remains to be determined whether changes in metabolism induced by altered nutrition during the JP period persist throughout the life course and if these observations are influenced by the background diet. Although the effects of increased folic acid intake operate through alterations in the epigenome, the mechanism by which such changes occur cannot be deduced from the present findings. One implication of our findings is that folic acid supplementation as a strategy to reverse the adverse effects of poor nutrition during early life on future health in humans may need to be undertaken with caution, particularly with respect to the timing of the period of supplementation and the composition of the background diet. However, demonstration of plasticity during the JP period supports the possibility of resetting an inappropriate phenotype induced in early life to one better adapted to meet the challenge of the prevailing environment.
Puberty has been identified as a period of relative instability in the epigenome associated with altered epigenetic regulation of genes associated with sexual maturation (13) and variation in nutrition in the prepubertal period in grandparents has been associated with patterns of mortality in the grandchildren (39). Furthermore, exposure during this period to hormones, including estrogens, induces changes in the epigenome in a manner that affects subsequent disease risk, which differs from the effects of hormonal exposure during the neonatal period (40). This may involve changing the DNA demethylation and remethylation cycles that occur in nondividing cells (41), e.g. by altering the balance of Dnmt-1 and demethylase activities (18,41). The JP period is also a time of increased growth and cell proliferation in specific tissues (32,33) that may facilitate epigenetic changes during mitotic cycles (12). Overall, our data support the view that, during the life course, specific periods of plasticity are associated with reduced stability of the epigenome that allow the phenotype of an organism to adapt to environmental cues, such as nutrition. It has been suggested that the phenotype induced in the fetus by environmental cues can promote later reproductive fitness by predicting the future environment and that an incorrect prediction is associated with increased risk of later chronic disease (2). Our findings suggest this hypothesis could be extended to include the phenotypic changes induced during the subsequent period of plasticity in puberty, perhaps enhancing the organism's life course strategy.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
2 Author disclosures: G. C. Burdge, K. A. Lillycrop, E. S. Phillips, J. L. Slater-Jefferies, A. A. Jackson, and M. A. Hanson, no conflicts of interest.
3 Supplemental Tables 1 and 2, and Supplemental Figure 1 are available with the online posting of this paper at jn.nutrition.org.
7 Abbreviations used: AF, folic acid-adequate; AOX, acyl-CoA carboxylase; βHB, β-hydroxybutyrate; C, control group; CPT-1, carnitine palmitoyl transferase-1; C/AF, control/adequate folate; C/FS, control/folate supplemented; Dnmt, DNA methyltransferase; FS, folic acid-supplemented; GR, glucocorticoid receptor; HSL, hormone-sensitive lipase; IR, insulin receptor; JP, juvenile-pubertal; LPL, lipoprotein lipase; NEFA, nonesterified fatty acid; PEPCK, phosphoenolpyruvate carboxykinase; pn, postnatal; PR, protein-restricted, PR/AF, protein-restricted/adequate folate; PR/FS, protein-restricted/folate supplemented; TAG, triglyceride.
Manuscript received 14 January 2009. Initial review completed 24 February 2009. Revision accepted 5 March 2009.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTIntroductionMaterials and MethodsResultsDiscussionLITERATURE CITED |
|---|
1. Godfrey KM, Barker DJ. Fetal programming and adult health. Public Health Nutr. 2001;4:611–24.[Medline]
2. Gluckman PD, Hanson MA. Living with the past: evolution, development, and patterns of disease. Science. 2004;305:1733–6.
3. Armitage JA, Taylor PD, Poston L. Experimental models of developmental programming: consequences of exposure to an energy rich diet during development. J Physiol. 2005;565:3–8.
4. Bertram CE, Hanson MA. Animal models and programming of the metabolic syndrome. Br Med Bull. 2001;60:103–21.
5. Roseboom T, de Rooij SR, Painter R. The Dutch famine and its long-term consequences for adult health. Early Hum Dev. 2006;82:485–91.[CrossRef][Medline]
6. Erhuma A, Salter AM, Sculley DV, Langley-Evans SC, Bennett AJ. Prenatal exposure to a low-protein diet programs disordered regulation of lipid metabolism in the aging rat. Am J Physiol Endocrinol Metab. 2007;292:E1702–14.
7. Langley SC, Jackson AA. Increased systolic blood pressure in adult rats induced by fetal exposure to maternal low protein diets. Clin Sci (Lond). 1994;86:217–22.[Medline]
8. Torrens C, Hanson MA, Gluckman PD, Vickers MH. Maternal undernutrition leads to endothelial dysfunction in adult male rat offspring independent of postnatal diet. Br J Nutr. 2009;101:27–33.[CrossRef][Medline]
9. Jackson AA, Dunn RL, Marchand MC, Langley-Evans SC. Increased systolic blood pressure in rats induced by a maternal low-protein diet is reversed by dietary supplementation with glycine. Clin Sci (Lond). 2002;103:633–9.[Medline]
10. Torrens C, Brawley L, Anthony FW, Dance CS, Dunn R, Jackson AA, Poston L, Hanson MA. Folate supplementation during pregnancy improves offspring cardiovascular dysfunction induced by protein restriction. Hypertension. 2006;47:982–7.
11. Burdge GC, Lillycrop KA, Jackson AA, Gluckman PD, Hanson MA. The nature of the growth pattern and of the metabolic response to fasting in the rat are dependent upon the dietary protein and folic acid intakes of their pregnant dams and post-weaning fat consumption. Br J Nutr. 2008;99:540–9.[Medline]
12. Burdge GC, Hanson MA, Slater-Jefferies JL, Lillycrop KA. Epigenetic regulation of transcription: a mechanism for inducing variations in phenotype (fetal programming) by differences in nutrition during early life? Br J Nutr. 2007;97:1036–46.[CrossRef][Medline]
13. Dolinoy DC, Das R, Weidman JR, Jirtle RL. Metastable epialleles, imprinting, and the fetal origins of adult diseases. Pediatr Res. 2007;61:R30–7.[CrossRef][Medline]
14. Wolff GL, Kodell RL, Moore SR, Cooney CA. Maternal epigenetics and methyl supplements affect agouti gene expression in Avy/a mice. FASEB J. 1998;12:949–57.
15. Weaver IC, Cervoni N, Champagne FA, D'Alessio AC, Sharma S, Seckl JR, Dymov S, Szyf M, Meaney MJ. Epigenetic programming by maternal behavior. Nat Neurosci. 2004;7:847–54.[CrossRef][Medline]
16. Pham TD, MacLennan NK, Chiu CT, Laksana GS, Hsu JL, Lane RH. Uteroplacental insufficiency increases apoptosis and alters p53 gene methylation in the full-term IUGR rat kidney. Am J Physiol Regul Integr Comp Physiol. 2003;285:R962–70.
17. Lillycrop KA, Phillips ES, Jackson AA, Hanson MA, Burdge GC. Dietary protein restriction of pregnant rats induces and folic acid supplementation prevents epigenetic modification of hepatic gene expression in the offspring. J Nutr. 2005;135:1382–6.
18. Lillycrop KA, Slater-Jefferies JL, Hanson MA, Godfrey KM, Jackson AA, Burdge GC. Induction of altered epigenetic regulation of the hepatic glucocorticoid receptor in the offspring of rats fed a protein-restricted diet during pregnancy suggests that reduced DNA methyltransferase-1 expression is involved in impaired DNA methylation and changes in histone modifications. Br J Nutr. 2007;97:1064–73.[CrossRef][Medline]
19. Lillycrop KA, Phillips ES, Torrens C, Hanson MA, Jackson AA, Burdge GC. Feeding pregnant rats a protein-restricted diet persistently alters the methylation of specific cytosines in the hepatic PPARalpha promoter of the offspring. Br J Nutr. 2008;100:278–82.[Medline]
20. Burdge GC, Slater-Jefferies J, Torrens C, Phillips ES, Hanson MA, Lillycrop KA. Dietary protein restriction of pregnant rats in the F0 generation induces altered methylation of hepatic gene promoters in the adult male offspring in the F1 and F2 generations. Br J Nutr. 2007;97:435–9.[CrossRef][Medline]
21. Vickers MH, Gluckman PD, Coveny AH, Hofman PL, Cutfield WS, Gertler A, Breier BH, Harris M. Neonatal leptin treatment reverses developmental programming. Endocrinology. 2005;146:4211–6.
22. Choi SW, Friso S, Keyes MK, Mason JB. Folate supplementation increases genomic DNA methylation in the liver of elder rats. Br J Nutr. 2005;93:31–5.[Medline]
23. Kotsopoulos J, Sohn KJ, Kim YI. Postweaning dietary folate deficiency provided through childhood to puberty permanently increases genomic DNA methylation in adult rat liver. J Nutr. 2008;138:703–9.
24. Ge RS, Chen GR, Dong Q, Akingbemi B, Sottas CM, Santos M, Sealfon SC, Bernard DJ, Hardy MP. Biphasic effects of postnatal exposure to diethylhexylphthalate on the timing of puberty in male rats. J Androl. 2007;28:513–20.
25. Banu SK, Samuel JB, Arosh JA, Burghardt RC, Aruldhas MM. Lactational exposure to hexavalent chromium delays puberty by impairing ovarian development, steroidogenesis and pituitary hormone synthesis in developing Wistar rats. Toxicol Appl Pharmacol. 2008;232:180–9.[CrossRef][Medline]
26. Department of Health. Folic acid and the prevention of disease. Rep Health Soc Subj (Lond). 2000;50:i–xv, 1–101.[Medline]
27. Burdge GC, Powell J, Calder PC. Lack of effect of meal fatty acid composition on postprandial lipid, glucose and insulin responses in men and women aged 50–65 years consuming their habitual diets. Br J Nutr. 2006;96:489–500.[Medline]
28. Folch J, Lees M, Sloane-Stanley GH. A simple method for the isolation and purification of total lipides from animal tissues. J Biol Chem. 1957;226:497–509.
29. Burdge GC, Wright P, Jones AE, Wootton SA. A method for separation of phosphatidylcholine, triacylglycerol, non-esterified fatty acids and cholesterol esters from plasma by solid-phase extraction. Br J Nutr. 2000;84:781–7.[Medline]
30. Harris RG, White E, Phillips ES, Lillycrop KA. The expression of the developmentally regulated proto-oncogene Pax-3 is modulated by N-Myc. J Biol Chem. 2002;277:34815–25.
31. Vandesompele J, De PK, Pattyn F, Poppe B, Van RN, De PA, Speleman F. Accurate normalization of real-time quantitative RT-PCR data by geometric averaging of multiple internal control genes. Genome Biol. 2002;3:RESEARCH0034.[Medline]
32. Baum D, Beck RQ, Hammer LD, Brasel JA, Greenwood MR. Adipose tissue thymidine kinase activity in man. Pediatr Res. 1986;20:118–21.[CrossRef][Medline]
33. Cleary MP, Klein BE, Brasel J, Greenwood MR. Thymidine kinase and DNA polymerase activity during postnatal growth of the epididymal fat pad. J Nutr. 1979;109:48–54.
34. Kota BP, Huang TH, Roufogalis BD. An overview on biological mechanisms of PPARs. Pharmacol Res. 2005;51:85–94.[CrossRef][Medline]
35. Evans K, Burdge GC, Wootton SA, Clark ML, Frayn KN. Regulation of dietary fatty acid entrapment in subcutaneous adipose tissue and skeletal muscle. Diabetes. 2002;51:2684–90.
36. Zeisel SH, da Costa KA, Albright CD, Shin OH. Choline and hepatocarcinogenesis in the rat. Adv Exp Med Biol. 1995;375:65–74.[Medline]
37. Mato JM, Martinez-Chantar ML, Lu SC. Methionine metabolism and liver disease. Annu Rev Nutr. 2008;28:273–93.[CrossRef][Medline]
38. Gluckman PD, Lillycrop KA, Vickers MH, Pleasants AB, Phillips ES, Beedle AS, Burdge GC, Hanson MA. Metabolic plasticity during mammalian development is directionally dependent on early nutritional status. Proc Natl Acad Sci USA. 2007;104:12796–800.
39. Pembrey ME, Bygren LO, Kaati G, Edvinsson S, Northstone K, Sjostrom M, Golding J. Sex-specific, male-line transgenerational responses in humans. Eur J Hum Genet. 2006;14:159–66.[CrossRef][Medline]
40. De Assis S, Hilakivi-Clarke L. Timing of dietary estrogenic exposures and breast cancer risk. Ann N Y Acad Sci. 2006;1089:14–35.[CrossRef][Medline]
41. Szyf M. The dynamic epigenome and its implications in toxicology. Toxicol Sci. 2007;100:7–23.
This article has been cited by other articles:
|
|
 |
|
  L. A. Cox and P. W. Nathanielsz The importance of altered gene promoter methylation and transcription factor binding in developmental programming of central appetitive drive J. Physiol., October 15, 2009; 587(20): 4763 - 4764. [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
