ABSTRACT
Objective:To observe the effect of shift work on the stability of the circadian clock and insulin sensitivity in non-overweight/obese individuals with normal blood glucose, and explore underlying connection.Methods:Female shift working nurses in the Department of Blood Transplantation and non-shift working nurses in the Health Management Center in the First Affiliated Hospital of Zhengzhou University were divided into shift worker group (SW group) and non-shift worker group (NSW group). Serum inflammatory factors [interleukin-6 (IL-6), tumor necrosis factor-α(TNF-α)], adipokines (adiponectin, leptin, chemerin, visfatin), and melatonin levels were measured using enzyme linked immunosorbent assay (ELISA). Realtime fluorescence quantitative PCR was performed to detect peripheral blood circadian clock genes circadian locomotor output cycles protein kaput(Clock) and brain and muscle ARNT-like protein 1(Bmal1). Cortisol and fasting insulin were measured by chemiluminescent microparticle immunoassay, and HbA 1C was measured by capillary electrophoresis. In addition, visceral fat area (VFA) was assessed with bioelectrical impedance analyzer, and mid-sleep time composite phase deviations (CPD) was calculated based on the International Physical Activity Short Questionnaire. Results:SW group had lower serum level of melatonin ( P=0.023) and higher cortisol ( P=0.001) than the NSW group, and altered mRNA expression of Clock and Bmal1 ( P=0.034, P=0.047). Fasting blood glucose and HbA 1C in the SW group, although in the normal range, had been higher than in the NSW group ( P=0.011, P=0.033). Although body mass index was normal in SW group, VFA had been higher than that of the NSW group ( P=0.010). And homeostasis model assessment for insulin resistance (HOMA-IR), IL-6, TNF-α, leptin, chemerin, and visfatin were significantly higher in the SW group than NSW group ( P=0.033, P=0.012, P=0.001, P=0.011, P=0.021, P=0.007). In addition, adjusting for body mass index and activity factors revealed a significant positive correlation between CPD and VFA ( r=0.434, P=0.049), inflammatory factors IL-6 ( r=0.514, P=0.017) and TNF-α ( r=0.700, P<0.001) and pro-inflammatory adipokines leptin ( r=0.473, P=0.030), chemerin ( r=0.439, P=0.047), visfatin ( r=0.521, P=0.015). Conclusion:Shift work can affect circadian clock, with increased visceral adiposity, pro-inflammatory adipokines, inflammatory factors and decreased insulin sensitivity in women without overweight/obese.
ABSTRACT
Objective:To observe the effects of continuous light exposure on skeletal muscle fiber type transformation and lipid metabolism, and to explore its internal relationship.Methods:Mice were randomly divided into normal light group and 24-hour continuous light group by random number table. The serum and skeletal muscle lipid content and urine 6-sulfatoxymelatonin(6-SML)level were detected by ELISA. The expression of circadian clock and lipid metabolism related genes mRNA were observed by realtime PCR. The muscle fiber type and lipid deposition were evaluated by tissue immunofluorescence as well as oil red O staining.Results:Compared with the normal light group, the level of 6-SML in urine at night decreased( P<0.05), and the expression level and rhythm of brain and muscle ARNT-like protein 1(Bmal1), circadian locomotor output cycles protein kaput(Clock), and period 2(Per2)mRNA in the skeletal muscle changed in continuous light group. In addition, the body weight, blood lipid, free fatty acid, and triglyceride contents of skeletal muscle in continuous light group increased significantly( P<0.05 or P<0.01), the expression of carnitine palmitoyltransferase 1b (Cpt1b)mRNA, the key enzyme of fatty acid oxidation, decreased significantly( P<0.05), while the expression of stearoyl-CoA desaturase(Scd1)mRNA, a lipid synthesis related gene, increased significantly( P<0.01). Further immunofluorescence analysis showed that the proportion of slow muscle fibers decreased and that of fast muscle fibers increased in continuous light group(both P<0.05). Conclusion:The process of ectopic deposition of lipid in skeletal muscle in mice induced by continuous light exposure may be related to the remodeling of skeletal muscle fibers.