Social stress profoundly affects lipid metabolism: Over-expression of SR-BI in liver and changes in lipids and lipases in plasma and tissues of stressed mice

Abstract 

We examined the effect of chronic social stress, similar to that endured by humans, on lipid metabolism of mice. The activity of the lipoprotein lipase (LPL) enzyme increased in adrenals, while in plasma it diminished significantly. Hepatic lipase (HL) was strongly affected in liver and adrenal glands, increasing four-fold and three-fold, respectively. At the same time, scavenger receptor class-B type-I (SR-BI), which are considered the high-density lipoprotein (HDL) receptor in the liver, increased significantly.

Although the adrenals do not synthesise HL, the increase in HL may facilitate the uptake of HDL cholesterol for the synthesis of corticoids, which increase significantly following chronic stress. The volume of adrenal glands in control animals was significantly higher than in stressed animals (1.23±0.12mm³ versus 0.29±0.06mm³, p<0.001), corresponding with the weight difference of these organs. Medulla volume was also different in the two groups (0.27±0.10mm³ versus 0.04±0.02mm³, p<0.05). Despite this, corticosterone in plasma was significantly higher in stressed animals.

Our results shows, for the first time, the effect of chronic social stress on lipid metabolism in general, and in particular on the SR-BI receptor and HL, which is directly involved in cholesterol reverse transport.

Keywords: Lipoprotein lipase (LPL), Hepatic lipase (HL), Stress, SR-BI