In recent years the Illumina HumanMethylation450 (HM450) BeadChip has provided a user-friendly platform to profile DNA methylation in human samples. However, HM450 lacked coverage of distal regulatory elements. Illumina have now released the MethylationEPIC (EPIC) BeadChip, with new content specifically designed to target these regions. We have used HM450 and whole-genome bisulphite sequencing (WGBS) to perform a critical evaluation of the new EPIC array platform. EPIC covers over 850,000 CpG sites, including >90 % of the CpGs from the HM450 and an additional 413,743 CpGs. Even though the additional probes improve the coverage of regulatory elements, including 58 % of FANTOM5 enhancers, only 7 % distal and 27 % proximal ENCODE regulatory elements are represented. Detailed comparisons of regulatory elements from EPIC and WGBS show that a single EPIC probe is not always informative for those distal regulatory elements showing variable methylation across the region. However, overall data from the EPIC array at single loci are highly reproducible across technical and biological replicates and demonstrate high correlation with HM450 and WGBS data. We show that the HM450 and EPIC arrays distinguish differentially methylated probes, but the absolute agreement depends on the threshold set for each platform. Finally, we provide an annotated list of probes whose signal could be affected by cross-hybridisation or underlying genetic variation. The EPIC array is a significant improvement over the HM450 array, with increased genome coverage of regulatory regions and high reproducibility and reliability, providing a valuable tool for high-throughput human methylome analyses from diverse clinical samples.

Individuals exposed to high‐fat, high‐sugar diets before birth have an increased risk of obesity in later life. Recent studies have shown that these offspring exhibit increased preference for fat, leading to suggestions that perinatal exposure to high‐fat, high‐sugar foods results in permanent changes within the central reward system that increase the subsequent drive to overconsume palatable foods. The present study has determined the effect of a maternal “junk‐food” diet on the expression of key components of the mesolimbic reward pathway in the offspring of rat dams at 6 wk and 3 mo of age. We show that offspring of junk‐food‐fed (JF) dams exhibit higher fat intake from weaning until at least 3 mo of age (males: 16±0.6 vs. 11±0.8 g/kg/d; females: 19±1.3 vs. 13±0.4 g/kg/d; P <0.01). mRNA expression of μ‐opioid receptor (Mu) was 1.6‐fold higher ( P <0.01) and dopamine active transporter (DAT) was 2‐fold lower ( P <0.05) in JF offspring at 6 wk of age. By 3 mo, these differences were reversed, and Mu mRNA expression was 2.8‐fold lower ( P <0.01) and DAT mRNA expression was 1.9‐fold higher ( P <0.01) in the JF offspring. These findings suggest that perinatal exposure to high‐fat, high‐sugar diets results in altered development of the central reward system, resulting in increased fat intake and altered response of the reward system to excessive junk‐food intake in postnatal life.—Ong, Z. Y., Muhlhausler, B. S. Maternal “junk‐food” feeding of rat dams alters food choices and development of the mesolimbic reward pathway in the offspring. FASEB J. 25, 2167‐2179 (2011). www.fasebj.org

The increased prevalence of obesity and related comorbidities is a major public health problem. While genetic factors undoubtedly play a role in determining individual susceptibility to weight gain and obesity, the identified genetic variants only explain part of the variation. This has led to growing interest in understanding the potential role of epigenetics as a mediator of gene-environment interactions underlying the development of obesity and its associated comorbidities. Initial evidence in support of a role of epigenetics in obesity and type 2 diabetes mellitus (T2DM) was mainly provided by animal studies, which reported epigenetic changes in key metabolically important tissues following high-fat feeding and epigenetic differences between lean and obese animals and by human studies which showed epigenetic changes in obesity and T2DM candidate genes in obese/diabetic individuals. More recently, advances in epigenetic methodologies and the reduced cost of epigenome-wide association studies (EWAS) have led to a rapid expansion of studies in human populations. These studies have also reported epigenetic differences between obese/T2DM adults and healthy controls and epigenetic changes in association with nutritional, weight loss, and exercise interventions. There is also increasing evidence from both human and animal studies that the relationship between perinatal nutritional exposures and later risk of obesity and T2DM may be mediated by epigenetic changes in the offspring. The aim of this review is to summarize the most recent developments in this rapidly moving field, with a particular focus on human EWAS and studies investigating the impact of nutritional and lifestyle factors (both pre- and postnatal) on the epigenome and their relationship to metabolic health outcomes. The difficulties in distinguishing consequence from causality in these studies and the critical role of animal models for testing causal relationships and providing insight into underlying mechanisms are also addressed. In summary, the area of epigenetics and metabolic health has seen rapid developments in a short space of time. While the outcomes to date are promising, studies are ongoing, and the next decade promises to be a time of productive research into the complex interactions between the genome, epigenome, and environment as they relate to metabolic disease.

Individuals exposed to an increased nutrient supply before birth have a high risk of becoming obese children and adults. It has been proposed that exposure of the fetus to high maternal nutrient intake results in permanent changes within the central appetite regulatory network. No studies, however, have investigated the impact of increased maternal nutrition on the appetite regulatory network in species in which this network develops before birth, as in the human. In the present study, pregnant ewes were fed a diet which provided 100% (control, n =8) or ∼160% (well‐fed, n =8) of metabolizable energy requirements. Ewes were allowed to lamb spontaneously, and lambs were sacrificed at 30 days of postnatal age. All fat depots were dissected and weighed, and expression of the appetite‐regulating neuropeptides and the leptin receptor (OBRb) were determined by in situ hybridization. Lambs of well‐fed ewes had higher glucose (Glc) concentrations during early postnatal life ( F =5.93, P <0.01) and a higher relative subcutaneous (s.c.) fat mass at 30 days of age (34.9±4.7 g/kg vs. 22.8±3.3 g/kg; P <0.05). The hypothalamic expression of proopiomelanocortin was higher in lambs of well‐fed ewes (0.48±0.09 vs. 0.28±0.04, P <0.05). In lambs of over‐nourished mothers, but not in controls, the expression of OBRb was inversely related to total relative fat mass ( r ² =0.50, P =0.05, n =8), and the direct relationship between the expression of the central appetite inhibitor CART and fat mass was lost. The expression of neuropeptide Y and AGRP was inversely related to total relative fat mass (NPY, r ² =0.28, P <0.05;agouti‐related peptide, r ² =0.39, P <0.01). These findings suggest that exposure to increased nutrition before birth alters the responses of the central appetite regulatory system to signals of increased adiposity after birth.—Muhlhausler, B. S., Adam, C. L., Findlay, P. A., Duffield, J. A., and McMillen, I. C. Increased maternal nutrition alters development of the appetite‐regulating network in the brain. FASEB J . 20, E556–E565 (2006)