Adverse Maternal Environments Perturb Hepatic DNA Methylome and Transcriptome Prior to the Adult-Onset Non-Alcoholic Fatty Liver Disease in Mouse Offspring.

Exposure to adverse early-life environments (AME) increases the incidence of developing adult-onset non-alcoholic fatty liver disease (NAFLD). DNA methylation has been postulated to link AME and late-onset diseases. This study aimed to investigate whether and to what extent the hepatic DNA methylome was perturbed prior to the development of NAFLD in offspring exposed to AME in mice. AME constituted maternal Western diet and late-gestational stress. Male offspring livers at birth (d0) and weaning (d21) were used for evaluating the DNA methylome and transcriptome using the reduced representation of bisulfite sequencing and RNA-seq, respectively. We found AME caused 5879 differentially methylated regions (DMRs) and zero differentially expressed genes (DEGs) at d0 and 2970 and 123, respectively, at d21. The majority of the DMRs were distal to gene transcription start sites and did not correlate with DEGs. The DEGs at d21 were significantly enriched in GO biological processes characteristic of liver metabolic functions. In conclusion, AME drove changes in the hepatic DNA methylome, which preceded perturbations in the hepatic metabolic transcriptome, which preceded the onset of NAFLD. We speculate that subtle impacts on dynamic enhancers lead to long-range regulatory changes that manifest over time as gene network alternations and increase the incidence of NAFLD later in life.

Adverse Maternal Environment and Postweaning Western Diet Alter Hepatic CD36 Expression and Methylation Concurrently with Nonalcoholic Fatty Liver Disease in Mouse Offspring.

BACKGROUND: The role of an adverse maternal environment (AME) in conjunction with a postweaning Western diet (WD) in the development of nonalcoholic fatty liver disease (NAFLD) in adult offspring has not been explored. Likewise, the molecular mechanisms associated with AME-induced NAFLD have not been studied. The fatty acid translocase or cluster of differentiation 36 (CD36) has been implicated to play a causal role in the pathogenesis of WD-induced steatosis. However, it is unknown if CD36 plays a role in AME-induced NAFLD. OBJECTIVE: This study was designed to evaluate the isolated and additive impact of AME and postweaning WD on the expression and DNA methylation of hepatic Cd36 in association with the development of NAFLD in a novel mouse model. METHODS: AME constituted maternal WD and maternal stress, whereas the control (Con) group had neither. Female C57BL/6J mice were fed a WD [40% fat energy, 29.1% sucrose energy, and 0.15% cholesterol (wt/wt)] 5 wk prior to pregnancy and throughout lactation. Non invasive variable stressors (random frequent cage changing, limited bedding, novel object, etc.) were applied to WD dams during the last third of pregnancy to produce an AME. Con dams consumed the control diet (CD) (10% fat energy, no sucrose or cholesterol) and were not exposed to stress. Male offspring were weaned onto either CD or WD, creating 4 experimental groups: Con-CD, Con-WD, AME-CD, and AME-WD, and evaluated for metabolic and molecular parameters at 120 d of age. RESULTS: AME and postweaning WD independently and additively increased the development of hepatic steatosis in adult male offspring. AME and WD independently and additively upregulated hepatic CD36 protein and mRNA expression and hypomethylated promoters 2 and 3 of the Cd36 gene. CONCLUSIONS: Using a mouse AME model together with postweaning WD, this study demonstrates a role for CD36 in AME-induced NAFLD in offspring and reveals 2 regions of environmentally induced epigenetic heterogeneity within Cd36.

The relationship between early-life environment, the epigenome and the microbiota.

Children exposed to early-life adversity carry a greater risk of poor health and disease into adulthood. This increased disease risk is shadowed by changes in the epigenome. Epigenetics can change gene expression to modify disease risk; unfortunately, how epigenetics are changed by the environment is unclear. It is known that the environment modifies the microbiota, and recent data indicate that the microbiota and the epigenome interact and respond to each other. Specifically, the microbiome may alter the epigenome through the production of metabolites. Investigating the relationship between the microbiome and the epigenome may provide novel understanding of the impact of early-life environment on long-term health.

Intrauterine growth restriction disrupts developmental epigenetics around distal growth hormone response elements on the rat hepatic IGF-1 gene.

Intrauterine growth restriction (IUGR) decreases serum IGF-1 levels. Postnatal IGF-1 expression is transcriptionally regulated by growth hormone (GH) through growth hormone response elements (GHREs). We hypothesized that IUGR disrupts the normal developmental maturation of hepatic IGF-1 intron 2 growth hormone response element (IN2GHRE) histone methylation of key lysines and DNA methylation. We also evaluated a 5' distal weak enhancer (IGF-1 5'-upstream region growth hormone response element; 5URGHRE) as a GHRE specificity control. IUGR was induced through a well-characterized model of bilateral uterine artery ligation of the pregnant rat. Offspring livers were tested at d 0 and 21. Chromatin immunoprecipitation and bisulfite sequencing quantified epigenetic characteristics. We found that distinct age-related developmental patterns of histone and DNA methylation characterize each GHRE. Development increased H3K4 trimethylation (me3) in both GHREs. However, H3K9me3 decreased with age at IN2GHRE and increased with age at 5URGHRE. IUGR altered the developmental pattern of H3K4me3 and K9me3 around the GHREs in a sex-specific manner at d 21. Developmental and IUGR-induced DNA methylation occurred in a GHRE-, CpG site-, and sex-specific manner. We conclude that IUGR disrupts developmental epigenetics around distal GHREs on the rat hepatic IGF-1 gene.