Adrenal Abcg1 controls cholesterol flux and steroidogenesis

Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its systemic inactivation results in neutral lipid redistribution to macrophages. However, the function of ABCG1 in steroidogenic organs is not explored. To model this question, we inactivated the ortholog Abcg1 gene in the mouse adrenal cortex. Abcg1 disruption led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis, and to an 80% increase in corticosterone production. Importantly, this phenotype was not recapitulated by inactivation of the cholesterol exporter Abca1. The absence of any change in lipid profile suggested that adrenal Abcg1 is not involved in cholesterol export to a clinically relevant extent. mRNA from adrenal glands from 4 control mice (carrying only the cre recombinase), and 4 mice in which Abca1 was conditionally inactivated, were sequenced and compared to the mRNA from 4 mice in which Abcg1 was conditionally inactivated.