Obesity is associated with changes in oxysterol metabolism and levels in mice liver, hypothalamus, adipose tissue and plasma

Oxysterols are bioactive lipids derived from cholesterol that are linked to inflammatory processes. Because obesity and metabolic syndrome are characterized by inflammation and altered cholesterol metabolism, we sought to investigate the variations of oxysterol levels and their metabolic pathways induced by obesity in the liver, hypothalamus, adipose tissue and plasma. To this end, we used diet-induced and genetic (ob/ob and db/db) models of obesity. Among the oxysterols measured, we found that 4 beta-oxysterol levels were consistently decreased in the high-fat diet study, at different time-points, and in the ob/ob model. Overall, we did not find any correlation between cytochromes mRNA expression and variations of oxysterol levels. We also measured the levels of hepatic primary bile acids, in these three models and found similar profiles between HFD and ob/ob mice. However, although they are downstream metabolites of oxysterols, the variations in bile acid levels did not reflect the variations of their precursors. Our data show that, when considering oxysterol metabolism, the high-fat diet and ob/ob models are more closely related when compared to the db/db model. However, we were able to discriminate between lean and obese phenotypes based on liver oxysterol (4 beta-hydroxycholesterol, 27-hydroxycholesterol, 7-hydroxycholestenone) levels and enzyme (CYP3A11, CYP27A1, CYP7A1) expression.