Prenatal betaine exposure alleviates corticosterone-induced inhibition of CYP27A1 expression in the liver of juvenile chickens associated with its promoter DNA methylation

Abstract

Sterol 27-hydroxylase (CYP27A1) plays an important role in cholesterol homeostasis by degrading cholesterol to bile acids. Betaine can alleviate high-fat diet-induced hepatic cholesterol accumulation and maternal betaine treatment programs the hepatic expression of CYP27A1 in offspring. Excessive corticosterone (CORT) exposure causes hepatic cholesterol deposition in chickens, yet it remains unknown whether prenatal betaine modulates CORT-induced cholesterol accumulation in chicken liver later in life and whether it involves epigenetic gene regulation of CYP27A1. In this study, fertilized eggs were injected with saline or betaine at 2.5mg/egg before incubation, and the hatchlings were raised under the same condition till 56days of age followed by 7days of subcutaneous CORT injection. Plasma concentrations of total cholesterol (Tch), HDL- and LDL-cholesterol were significantly increased (P<0.05), after CORT challenge, in both control and betaine groups. However, prenatal betaine exposure prevented CORT-induced increase (P<0.05) in hepatic Tch content. Hepatic expression of cholesterol biosynthesis genes and ACAT1 protein that esterifies cholesterol for storage, were activated in both control and betaine groups upon CORT challenge. However, betaine-treated chickens were protected from CORT-induced repression (P<0.05) in LXR and CYP27A1 expression in the liver. CORT-induced down-regulation of LXR and CYP27A1 coincided with significantly increased (P<0.05) CpG methylation on their promoters, which was significantly ameliorated in betaine-treated chickens. These results suggest that in ovo betaine injection alleviates CORT-induced hepatic cholesterol deposition most probably through epigenetic regulation of CYP27A1 and LXR genes in juvenile chickens.

Keywords: Betaine; CYP27A1; Cholesterol; Corticosterone; DNA methylation.