Direct Molecular Action of Taurine on Hepatic Gene Expression Associated with the Amelioration of Hypercholesterolemia in Rats.

ABSTRACT

Taurine can ameliorate hypercholesterolemia by facilitating cholesterol efflux and increasing cytochrome P450 7A1 (CYP7A1) without clear underlying molecular mechanisms. This study aims to elucidate the molecular action of taurine in diet-induced hypercholesterolemia. Male Wistar rats were fed a high cholesterol diet containing 5% taurine for 14 days. Three-dimensional primary hepatocytes from rats were exposed to 10 mM taurine for 24 h. Transcriptome analyses of both the liver and hepatocytes were performed using DNA microarray. Taurine significantly decreased serum cholesterol levels and increased hepatic CYP7A1 mRNA levels and transcription rates in rats. Taurine altered the expression of seventy-seven genes in the liver, involving lipid, drug, amino acid metabolism, and gluconeogenesis pathways. The small heterodimer partner (SHP), a transcription factor regulated by taurine, was suppressed. "Network analysis" revealed a negative correlation between the SHP and induction of CYP7A1 and cytochrome P450 8B1 (CYP8B1). However, CYP7A1 and CYP8B1 levels were not altered by taurine in 3D-primary hepatocytes. Venn diagram analyses of the transcriptomes in both hepatocytes and the liver indicated a consistent upregulation of organic anion transporting polypeptide 2 (OATP2) and betaine homocysteine methyltransferase (BHMT). Taurine ameliorated hypercholesterolemia in rats fed a high cholesterol diet by directly enhancing the hepatic expression of BHMT and OATP2, which modulated the SHP and induced CYP7A1 and CYP8B1, thereby promoting cholesterol catabolism and lowering blood cholesterol levels.