The Effects of Chronic Unpredictable Stress on Aorta Structure and Blood Lipids in Young and Old Rats

Chronic stress can induce dyslipidemia that promotes atherosclerosis. The aim of this study was to assess the effects of chronic unpredictable stress (CUS) on aorta structure and blood lipids as well as body weight in young and old rats. Young and old rats were treated with chronic unpredictable stress (for eight weeks) to evaluate plasma lipids and aorta structure. Thickness and internal diameter of aortic tissue were assessed by the ImageJ software. Stress decreased body weight gain in young rats (P < 0.05). Triglyceride, low density lipoprotein (LDL), very low density lipoprotein (VLDL) levels and low density lipoprotein/high density lipoprotein (LDL/HDL) ratio were more in old rats than young rats (P < 0.05). Stress significantly decreased serum triglyceride level in old rats (P < 0.05). Stress significantly increased VLDL level in young (10.3 ± 1.3 mg/dL versus 16.4 ± 2.1 mg/dL) and decreased VLDL level in old (10.8 ± 0.8 mg/dL versus 17.6 ± 1.6 mg/dL) rats (P < 0.05). The inner diameter of aorta was smaller in old (34.5 ± 1.7 micrometers) than young (42.3 ± 1.2 micrometers) rats (P < 0.01). Stress significantly increased inner diameter of aorta in old (42.3 ± 2.1 micrometers versus 34.5 ± 1.7 micrometers) rats (P < 0.01). Aortic wall thickness/aortic inner diameter ratio (AWT/AID) was greater in old rats than young rats. It seems that CUS has a dual effect on serum lipids and aortic diameter in young and old rats.