Supplemental Material for "Inhibition of SREBP-1c Rescues Hepatic CYP7B1 Expression and Bile Acid Synthesis in Malnourished Mice"

Malnutrition decreases intestinal bile acids, resulting in inefficient nutrient absorption and impaired catch-up growth. Mechanisms by which bile acid depletion occurs in malnutrition are unknown. Using a mouse model of early-life malnutrition, we explored bile acid homeostasis, focusing on transcriptional repression of CYP7B1, a rate-limiting enzyme in the alternative pathway of bile acid biosynthesis, by SREBP-1c, a master regulator of lipid metabolism. Mice were maintained on a low-protein low-fat or isocaloric control chow until eight weeks of age when livers were harvested for proteome profiling, western blot, RT-qPCR, and chromatin immunoprecipitation. Cultured hepatocytes and mice were treated with the SREBP-1c inhibitors fatostatin and betulin to determine whether this therapeutic strategy rescues CYP7B1 expression and bile acid synthesis in malnutrition. Malnutrition decreased the bile acid pool size and altered the expression of multiple hepatic cytochrome P450 enzymes, with profound depletion of CYP7B1, in males but not females. Malnutrition activated SREBP-1c and led to its enrichment at a <i>Cyp7b1</i> gene regulatory region that featured loss of binding by the basal transcriptional activator SP1. Treatment of cultured hepatocytes or malnourished mice with the SREBP-1c inhibitors fatostatin or betulin increased CYP7B1 expression. Both drugs rescued the bile acid pool size in malnourished mice. These results suggest that malnutrition impairs bile acid synthesis via transcriptional repression of <i>Cyp7b1</i> by SREBP-1c. SREBP-1c inhibitors restore hepatic CYP7B1 expression and bile acid synthesis.