Maternal betaine administration modulates hepatic type 1 iodothyronine deiodinase (Dio1) expression in chicken offspring through epigenetic modifications

As a feed additive, betaine is widely used in livestock production for its ability to promote growth. Our previous studies had reported that maternal betaine supplementation altered hepatic metabolism in offspring. But it remains unknown whether and how maternal betaine modulates metabolism of thyroid hormones in the offspring chickens by epigenetic modification. In this study, one hundred and twenty Rugao yellow-feathered laying hens were randomly divided into two groups, and were fed basal diet with or without 0.5% betaine supplementation for 28 days. After that, all the hens were artificially inseminated and then four hundreds fertilized eggs were selected. After hatching, the newborn chicks were raised until 56 days old. Betaine fed female chicks showed significantly lower body weight and lower level of biologically active thyroid hormone in plasma compared to control group, which was associated with significantly decrease in expression of type 1 iodothyronine deiodinase (Dio1). Moreover, betaine also changed hepatic expression of betaine-homocysteine -S-methyltransferase (BHMT) and DNA methyltransferase 1 (DNMT1), which may contribute to hypermethylation of the Dio1 promoter. Interestingly, betaine treatments of hens caused none of these effects in male chicks except Dio1 expression. These results indicate that maternal betaine administration effects growth of offspring through differential modification of Dio1 gene methylation and expression in liver and this model of transgenerational effects may help elucidate the mechanisms of maternal effects arise in natural systems.