Abstract 329: HSF-1 Knockout Enhances Dietary Cholesterol Metabolism by Inducing CYP7A1 Gene Expression and Attenuates Atherosclerosis

Abstract

Objective: Coronary heart disease and diabetes are highly prevalent among obese populations due to aberrant dietary cholesterol metabolism. Here we investigated the effect of heat shock factor-1 (HSF-1) on atherosclerosis and dietary cholesterol metabolism. Methods and Results: Atherogenic western diet-induced weight gain was reduced in HSF-1 and LDLr double knock out mice (HSF-1 -/- /LDLr -/- ), compared to LDLr -/- mice. Atherosclerotic lesion growth in aortic arch and carotid regions was retarded. Also, repression of PPAR-γ2 and AMPKα expression in adipose tissue, low hepatic steatosis, and lessened plasma adiponectins and lipoproteins were observed. Furthermore, reduced heat shock proteins and their mRNA levels in atherosclerotic lesions correlated with reduction in lesion burden. In HSF-1 -/- /LDLr -/- liver, higher cholesterol 7α hydroxylase (CYP7A1, the rate limiting enzyme in the synthesis of bile acid from cholesterol) and MDR1/p-glycoprotein (bile salt transporter across the hepatocyte canalicular membrane) gene expressions were observed, consistent with higher bile acid sequestration and larger hepatic bile ducts. HSF-1 deletion, however, upregulated both CYP7A1 enzyme and MDR1/p-glycoportein expression and activities, due to removal of its repressive binding in the CYP7A1 and MDR1 gene promoters. This increased the conversion of cholesterol into 7-α-hydroxycholesterol and bile acid, and dietary cholesterol metabolism. Conclusions: HSF-1 ablation not only eliminates heat shock response to retard atherosclerosis, but it also transcriptionally upregulates CYP7A1 and MDR1/P-gp axis to increase cholesterol metabolism. Therefore, HSF-1 is a metabolic regulator of dietary cholesterol and a major contributor to heart disease among obese population.