The loss of estrogen during menopause causes changes in the female body, with wide-ranging effects on health. Estrogen-containing hormone replacement therapy (HRT) leads to a relief of typical menopausal symptoms, benefits bone and muscle health, and is associated with tissue-specific gene expression profiles. As gene expression is controlled by epigenetic factors (including DNA methylation), many of which are environmentally sensitive, it is plausible that at least part of the HRT-associated gene expression is due to changes in DNA methylation profile. We investigated genome-wide DNA methylation and gene expression patterns of white blood cells (WBCs) and their associations with body composition, including muscle and bone measures of monozygotic (MZ) female twin pairs discordant for HRT. We identified 7,855 nominally significant differentially methylated regions (DMRs) associated with 4,044 genes. Of the genes with DMRs, five (ACBA1, CCL5, FASLG, PPP2R2B, and UHRF1) were also differentially expressed. All have been previously associated with HRT or estrogenic regulation, but not with HRT-associated DNA methylation. All five genes were associated with bone mineral content (BMC), and ABCA1, FASLG, and UHRF1 were also associated with body adiposity. Our study is the first to show that HRT associates with genome-wide DNA methylation alterations in WBCs. Moreover, we show that five differentially expressed genes with DMRs associate with clinical measures, including body fat percentage, lean body mass, bone mass, and blood lipids. Our results indicate that at least part of the known beneficial HRT effects on body composition and bone mass may be regulated by DNA methylation associated alterations in gene expression in circulating WBCs.

To elucidate the effects of maternal dietary betaine supplementation on hepatic expression of cholesterol metabolic genes in newborn piglets and the involved epigenetic mechanisms, we fed gestational sows with control or betaine-supplemented diets (3 g/kg) throughout pregnancy. Neonatal piglets born to betaine-supplemented sows had higher serum methionine concentration and hepatic content of betaine, which was associated with significantly up-regulated hepatic expression of glycine N-methyltransferase. Prenatal betaine exposure increased hepatic cholesterol content and modified the hepatic expression of cholesterol metabolic genes in neonatal piglets. Sterol regulatory element-binding protein 2 was down-regulated at both mRNA and protein levels, while 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) was down-regulated at the mRNA level, but up-regulated at the protein level, in betaine-exposed piglets. The transcriptional repression of HMGCR was associated with CpG island hypermethylation and higher repressive histone mark H3K27me3 (histone H3 lysine 27 trimethylation) on the promoter, whereas increased HMGCR protein content was associated with significantly decreased expression of miR-497. Furthermore, LDL receptor was significantly down-regulated at both mRNA and protein levels in the liver of betaine-exposed piglets, which was associated with promoter CpG hypermethylation. In addition, the expression of cholesterol-27α-hydroxylase (CYP27α1) was up-regulated at both mRNA and protein levels, while the expression of cholesterol-7α-hydroxylase (CYP7α1) was increased at the mRNA level, but unchanged at the protein level associated with increased expression of miR-181. These results indicate that maternal betaine supplementation increases hepatic cholesterol content in neonatal piglets through epigenetic regulations of cholesterol metabolic genes, which involve alterations in DNA and histone methylation and in the expression of microRNA targeting these genes.

Available data from both experimental and epidemiological studies suggest that inadequate diet in early life can permanently change the structure and function of specific organs or homoeostatic pathways, thereby ‘programming’ the individual’s health status and longevity. Sufficient evidence has accumulated showing significant impact of epigenetic regulation mechanisms in nutritional programming phenomenon. The essential role of early-life diet in the development of aging-related chronic diseases is well established and described in many scientific publications. However, the programming effects on lifespan have not been extensively reviewed systematically. The aim of the review is to provide a summary of research findings and theoretical explanations that indicate that longevity can be influenced by early nutrition.

Environmental exposures throughout the life course, including nutrition, may induce phenotypic and epigenetic changes. There is limited information about how timing affects the nature of such effects induced by a specific nutritional exposure. We investigated the effect of increased exposure to folic acid before birth or during the juvenile–pubertal period in rats on the epigenetic regulation of glucose homeostasis. Rats were fed either a folic acid-adequate (AF; 1 mg/kg feed) or a folic acid-supplemented (FS; 5 mg/kg feed) diet from conception until delivery and then an AF diet during lactation. Juvenile rats were fed either the AF or the FS diet from weaning for 28 d and then an AF diet. Liver and blood were collected after a 12 h fast between postnatal days 84 and 90. Maternal FS diet increased plasma glucose concentration significantly (P < 0·05) in females, but not in males. Post-weaning FS diet decreased glucose concentration significantly in females, but increased glucose concentration in males. There were no effects of the FS diet on phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression in males, while the pattern of expression was related to plasma glucose concentration in females. The FS diet induced specific changes in the methylation of individual CpG in females, but not in males, which were related to the time of exposure. Methylation of CpG − 248 increased the binding of CCAAT-enhancer-binding protein β to the PEPCK promoter. Together, these findings show that both the period during the life course and sex influence the effect of increased exposure to folic acid on the epigenetic regulation of PEPCK and glucose homeostasis.

Autism spectrum disorders (ASDs) including classic autism is a group of complex developmental disabilities with core deficits of impaired social interactions, communication difficulties and repetitive behaviors. Although the neurobiology of ASDs has attracted much attention in the last two decades, the role of microglia has been ignored. Existing data are focused on their recognized role in neuroinflammation, which only covers a small part of the pathological repertoire of microglia. This review highlights recent findings on the broader roles of microglia, including their active surveillance of brain microenvironments and regulation of synaptic connectivity, maturation of brain circuitry and neurogenesis. Emerging evidence suggests that microglia respond to pre- and postnatal environmental stimuli through epigenetic interface to change gene expression, thus acting as effectors of experience-dependent synaptic plasticity. Impairments of these microglial functions could substantially contribute to several major etiological factors of autism, such as environmental toxins and cortical underconnectivity. Our recent study on Rett syndrome, a syndromic autistic disorder, provides an example that intrinsic microglial dysfunction due to genetic and epigenetic aberrations could detrimentally affect the developmental trajectory without evoking neuroinflammation. We propose that ASDs provide excellent opportunities to study the influence of microglia on neurodevelopment, and this knowledge could lead to novel therapies.

Associations between birth weight and CVD in adult life are supported by experiments showing that undernutrition in fetal life programmes blood pressure. In rats, the feeding of a maternal low-protein (MLP) diet during gestation programmes hypertension. The present study aimed to assess the potential for a nutritional insult to impact across several generations. Pregnant female Wistar (F0) rats were fed a control (CON; n 10) or MLP (n 10) diet throughout gestation. At delivery all animals were fed a standard laboratory chow diet. At 10 weeks of age, F1 generation offspring were mated to produce a second generation (F2) without any further dietary change. The same procedure produced an F3 generation. Blood pressure in all generations was determined at 4, 6 and 8 weeks of age and nephron number was determined at 10 weeks of age. F1 generation MLP-exposed offspring exhibited raised (P < 0·001) systolic blood pressure (male 143 (sem 4) mmHg; female 141 (sem 4) mmHg) compared with CON animals (male 132 (sem 3) mmHg; female 134 (sem 4) mmHg). Raised blood pressure and reduced nephron number was also noted in the F2 generation (P < 0·001) and this intergenerational transmission occurred via both the maternal and paternal lines, as all three possible offspring crosses (MLP × CON, CON × MLP and MLP × MLP) were hypertensive (132 (sem 3) mmHg) compared with CON animals (CON × CON; 123 (sem 2) mmHg). No effect was noted in the F3 generation. It is concluded that fetal protein restriction may play a critical role in determining blood pressure and overall disease risk in a subsequent generation.

The impact of nutrition on the epigenetic machinery has increasingly attracted interest. The aim of the present study was to demonstrate the effects of various diets on methylation and gene expression. The antioxidative enzyme mitochondrial superoxide dismutase (MnSOD) was chosen as the model system because epigenetic regulation has been previously shown in cell lines for this gene. Promoter methylation and gene expression of MnSOD in buccal swabs from three sample groups were analysed. The three groups included: (1) forty vegetarians (aged 20–30 years); (2) age-matched omnivores; (3) elderly omnivores (aged>85 years). A 3-fold increase in the expression of the MnSOD gene was associated with decreased CpG methylation of the analysed promoter region in the vegetarian group compared with the age-matched omnivores group. Expression and promoter methylation of the MnSOD gene in elderly omnivores showed no significant differences compared with younger omnivores. In accordance with previous findings in various tissues, DNA global methylation was found to be significantly higher (30 %) in buccal swabs of younger subjects (independent of the diet), than in those of elderly omnivores. In the control experiment which was designed to verify the findings of the human buccal swab studies, the Caco-2 cell line was treated with zebularine. Results of the control study showed a 6-fold increase of MnSOD expression, an approximately 40 % decreased methylation of specified CpG in the MnSOD promoter and a 50 % reduction of global DNA methylation. These results indicate that diet affects the epigenetic regulation of human MnSOD.

Induction of an altered phenotype by prenatal under-nutrition involves changes in the epigenetic regulation of specific genes. We investigated the effect of feeding pregnant rats a protein-restricted (PR) diet with different amounts of folic acid on the methylation of individual CpG dinucleotides in the hepatic PPARα promoter in juvenile offspring, and the effect of the maternal PR diet on CpG methylation in adult offspring. Pregnant rats (five per group) were fed 180 g/kg casein (control) or 90 g/kg casein with 1 mg/kg folic acid (PR), or 90 g/kg casein and 5 mg/kg folic acid (PRF). Offspring were killed on postnatal day 34 (five males and females per group) and day 80 (five males per group). Methylation of sixteen CpG dinucleotides in the PPARα promoter was measured by pyrosequencing. Mean PPARα promoter methylation in the PR offspring (4·5 %) was 26 % lower than controls (6·1 %) due to specific reduction at CpG dinucleotides 2 (40 %), 3 (43 %), 4 (33 %) and 16 (48 %) (P < 0·05). There was no significant difference in methylation at these CpG between control and PRF offspring. Methylation of CpG 5 and 8 was higher (47 and 63 %, respectively, P < 0·05) in the PRF offspring than control or PR offspring. The methylation pattern in day 80 PR offspring was comparable to day 34 PR offspring. These data show for the first time that prenatal nutrition induces differential changes to the methylation of individual CpG dinucleotides in juvenile rats which persist in adults.

There is considerable evidence for the induction of different phenotypes by variations in the early life environment, including nutrition, which in man is associated with a graded risk of metabolic disease; fetal programming. It is likely that the induction of persistent changes to tissue structure and function by differences in the early life environment involves life-long alterations to the regulation of gene transcription. This view is supported by both studies of human subjects and animal models. The mechanism which underlies such changes to gene expression is now beginning to be understood. In the present review we discuss the role of changes in the epigenetic regulation of transcription, specifically DNA methylation and covalent modification of histones, in the induction of an altered phenotype by nutritional constraint in early life. The demonstration of altered epigenetic regulation of genes in phenotype induction suggests the possibility of interventions to modify long-term disease risk associated with unbalanced nutrition in early life.