持续光照对小鼠骨骼肌肌纤维重塑及脂代谢的影响

目的:观察持续光照对骨骼肌肌纤维类型转化及脂代谢的影响，并探讨其内在联系。方法:按随机数字表法将小鼠随机分为正常光照组及24 h持续光照组。采用酶联免疫吸附测定(ELISA)法检测血清及骨骼肌脂质含量和尿6-羟基硫酸褪黑素(6-SML)水平，实时荧光定量PCR观察骨骼肌生物钟基因及脂代谢相关基因mRNA表达，组织免疫荧...

Effects of continuous light exposure on muscle fiber remodeling and lipid metabolism in mice

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.