Gestational dietary betaine supplementation suppresses hepatic expression of lipogenic genes in neonatal piglets through epigenetic and glucocorticoid receptor-dependent mechanisms

Methyl donors play critical roles in nutritional programming through epigenetic regulation of gene expression. Here we fed gestational sows with control or betaine-supplemented diets (3 g/kg) throughout the pregnancy to explore the effects of maternal methyl-donor nutrient on neonatal expression of hepatic lipogenic genes. Betaine-exposed piglets demonstrated significantly lower liver triglyceride content associated with down-regulated hepatic expression of lipogenic genes acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD) and sterol regulatory element-binding protein-1c. Moreover, s-adenosyl methionine to s-adenosyl homocysteine ratio was elevated in the liver of betaine-exposed piglets, which was accompanied by DNA hypermethylation on FAS and SCD gene promoters and more enriched repression histone mark H3K27me3 on SCD gene promoter. Furthermore, glucocorticoid receptor (GR) binding to SCD gene promoter was diminished along with reduced serum cortisol and liver GR protein content in betaine-exposed piglets. GR-mediated SCD gene regulation was confirmed in HepG2 cells in vitro. Dexamethasone (Dex) drastically increased the luciferase activity of porcine SCD promoter, while the deletion of GR response element on SCD promoter significantly attenuated Dex-mediated SCD transactivation. In addition, miR-let-7e, miR-1285 and miR-124a, which respectively target porcine SCD, ACC and GR, were significantly up-regulated in the liver of betaine-exposed piglets, being in accordance with decreased protein content of these three genes. Taken together, our results suggest that maternal dietary betaine supplementation during gestation attenuates hepatic lipogenesis in neonatal piglets via epigenetic and GR-mediated mechanisms.