Maternal vitamin B 12 deficiency in rats alters DNA methylation in metabolically important genes in their offspring

Vitamin B 12 deficiency is a critical problem worldwide and peri-conceptional deficiency of this vitamin is associated with the risk of complex cardio-metabolic diseases. Nutritional perturbations during these stages of development may lead to changes in the fetal epigenome. Using Wistar rat model system, we have earlier shown that low maternal B 12 levels are associated with low birth weight, adiposity, insulin resistance, and increased triglyceride levels in the offspring, which might predispose them to the risk of cardio-metabolic diseases in adulthood. In this study, we have investigated the effects of maternal B 12 deficiency on genome-wide DNA methylation profile of the offspring and the effect of rehabilitation of mothers with B 12 at conception. We have performed methylated DNA immunoprecipitation sequencing of liver from pups in four groups of Wistar rats: Control (C), B 12 -restricted (B 12 R), B 12 -rehabilitated at conception (B 12 RC), and B 12 -rehabilitated at parturition (B 12 RP). We have analyzed differentially methylated signatures between the three groups as compared to controls. We have identified a total of 214 hypermethylated and 142 hypomethylated regions in the 10 kb upstream region of transcription start site in pups of B 12 -deficient mothers, which are enriched in genes involved in fatty acid metabolism and mitochondrial transport/metabolism. B 12 rehabilitation at conception and parturition is responsible for reversal of methylation status of many of these regions to control levels suggesting a causal association with metabolic phenotypes. Thus, maternal B 12 restriction alters DNA methylation of genes involved in important metabolic processes and influences the offspring phenotype, which is reversed by B 12 rehabilitation of mothers at conception.