Effects of constant light exposure on obesity in high fat diet rats / 中华内分泌代谢杂志

ABSTRACT

Objective To observe the effects of constant light exposure on the obesity in high fat diet rats. Methods Thirty-two male SD rats were randomly divided into four groupsrats on a normal chow exposed to standard light-dark cycle ( group A) , rats on a normal chow exposed to constant light ( group B) , rats on a high fat diet exposed to standard light-dark cycle ( group C) , and rats on a high fat diet exposed to constant light ( group D) . Body weights and food intakes were recorded weekly throughout the 12-week study. Body weight, fat mass, visceral adipose tissue weight, intraperitoneal glucose tolerance test ( IPGTT) results, insulin resistance parameters, serum lipids and levels of interleukin 6 (IL-6), tumor necrosis factor-α(TNF-α) were compared among groups. Epididymal adipose tissues mRNA expression of circadian clock genes, i. e. clock, bmal1, rorα, rev-erbα, cry1, per1, and per2 were analyzed by realtime PCR. Results From the 9th week, body weights of rats in group D were significantly higher than those in group C (all P<0. 05). At the 12th week, area under curve of IPGTT (AUC-IPGTT) in groups B, C, and D were significantly higher than that in group A. AUC-IPGTT in group D was significantly higher than that in group C (all P<0.05). Compared with group C,asignificant increase in fat mass,visceral adipose tissue weight,homeostasis model assessment for insulin resistance, serum cholesterol, TNF-α levels were observed in group D ( all P<0. 05). And a significant decrease in quantitative insulin sensitivity check index ( QUICKI) and high density lipoprotein-cholesterol were observed in group D in comparison with group C (both P<0. 05). Circadian clock genes (clock, rorα, rev-erbα, cry1, per1) mRNA expressions in group B and D were significantly different from those in group A (all P<0. 05) . Expression of cry1 in group D was significantly higher than that in group C. In group C, rev-erbαmRNA expression was significantly down-regulated in comparison with group A (P<0. 05). Conclusion Constant light exposure exaggerates obesity, glycolipid metabolism abnormality, inflammation, and insulin resistance in high fat diet rats.