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Objective Constant light exposure can lead to hypercatabolism. The aim of this study was to investigate the effects of different light rhythm on skeletal muscle metabolism in endotoxemia rats, and looked for the optimal light rhythm that could reduce skeletal muscle consumption and enhance the recovery of patients with sepsis. Methods 54 adult male S-D rats were randomly divided into 3 groups on average：Control group (intraperitoneal injection of normal saline +12h/12h light-dark cycle for 7 days), LPS- regular light group (intraperitoneal injection of lipopolysaccharide(LPS) +12h/12h light-dark cycle for 7 days) and LPS-constant light group (intraperitoneal injection of LPS + constant light for 7 days). All experimental animals were sacrificed on the 8th day. The level of skeletal muscle metabolites 3-methylhistidine (3-mh) and tyrosine, atrophy genes MAFbx and murf-1 mRNA and hypothalamic clock genes BMAL1, CLOCK and neuropeptide POMC were also detected. Results The food intake, weight growth ratio and the ratio of extensor digitorum longus/weight in the LPS-constant light group were significantly lower than those in the LPS-regular light group (P <0.05), and both groups were significantly lower than those in the control group (P <0.01). The skeletal muscle metabolites 3-methylhistidine(nmol/g) and tyrosine(nmol/g) in the LPS-constant light group rats (6.200±0.273 and 461.039±13.292) were significantly higher than those in the LPS- regular light group (5.197±0.263 and 375.744±20.308) and the control group (3.244±0.275 and 290.935±19.065,all P <0.05). The expression levels of atrophic genes MAFbx and murf-1 mRNA and tnf-alpha and il-1 mRNA in hypothalamus in the LPS-constant light group were significantly higher than those in the LPS- regular light group(P <0.05), and both groups were significantly higher than those in the control group (P <0.05). The expression of the clock genes(BMAL1 and CLOCK) in the showed obvious rhythm (SE (A) /A<0.3) in the LPS-regular light group and the control group. The expression of BMAL1 was highest at the beginning of the illumination period, while the expression of CLOCK was high during the illumination period and decreased during the darkness period. In the LPS-constant light group, the expression of BMAL1 and CLOCK rhythm lost rhythm. Conclusion Normal light rhythm can maintain the normal rhythm expression of hypothalamic clock gene in rats with endotoxemia and reduce POMC-mediated skeletal muscle consumption, which may be of positive significance for the enhanced recovery of sepsis.
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Objective@#To investigate the mechanism of cell autophagy for regulating skeletal muscle wasting of rats after severe burns.@*Methods@#Seventy-two Sprague-Dawley rats were collected and divided into sham injury group, simple burn group, burn+ phosphate buffer solution (PBS) group, and burn+ 3-methyladenine (3-MA) group according to the random number table, with 18 rats in each group. Rats in simple burn group, burn+ PBS group, and burn+ 3-MA group were inflicted with 30% total body surface area full-thickness scald (hereinafter referred to as burns). Rats in sham injury group were sham injured. Immediately after burns and fluid resuscitation, rats in burn+ PBS group were intraperitoneally injected with 1 mL PBS, and rats in burn+ 3-MA group were intraperitoneally injected with 1 mL 3-MA (125 g/L). On post injury day 3 and 7, the weights of anterior tibial muscle of right hind limbs and body of rats were measured to calculate percentage of anterior tibial muscle of right hind limbs weight. Protein expressions of microtubule related protein 1 light chain 3A (LC3A) and Beclin-1 of anterior tibial muscle were observed by immunofluorescence method and detected by Western blotting, and ratio of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ was calculated. Data were processed with analysis of variance of factorial design, one-way analysis of variance, t-test and Bonferroni correction.@*Results@#On post injury day 3 and 7, percentages of anterior tibial muscle of right hind limbs weight of rats in simple burn group were (0.148±0.009)% and (0.134±0.018)%, respectively, which were significantly lower than those in sham injury group [(0.203±0.009)%, (0.181±0.015)%, t=10.585, 4.913, P<0.01]. Percentages of anterior tibial muscle of right hind limbs weight of rats in burn+ 3-MA group were (0.187±0.004)% and (0.192±0.009)%, respectively, which were obviously higher than those in burn+ PBS group [(0.162±0.005)%, (0.167±0.005)%, t=9.564, 5.948, P<0.01]. On post injury day 3 and 7, protein expressions of Beclin-1 and microtubule related protein 1 LC3A of anterior tibial muscle of rats in simple burn group were significantly higher than those in sham injury group, while protein expressions of Beclin-1 and microtubule related protein 1 LC3A of anterior tibial muscle of rats in burn+ 3-MA group were significantly lower than those in burn+ PBS group. Ratios of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ of anterior tibial muscle of rats in simple burn group were significantly higher than those in sham injury group (t=3.461, 3.353, P<0.05), while ratios of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ of anterior tibial muscle of rats in burn+ 3-MA group were significantly lower than those in burn+ PBS group (t=3.129, 3.977, P<0.05).@*Conclusions@#Cell autophagy induced by severe burns is involved in the process of skeletal muscle wasting of rats, and inhibition of cell autophagy may contribute to the remission of skeletal muscle wasting of rats induced by burns.
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Protocols that mimic resistance exercise training (RET) in rodents present several limitations, one of them being the electrical stimulus, which is beyond the physiological context observed in humans. Recently, our group developed a conditioning system device that does not use electric shock to stimulate rats, but includes fasting periods before each RET session. The current study was designed to test whether cumulative fasting periods have some influence on skeletal muscle mass and function. Three sets of male Wistar rats were used in the current study. The first set of rats was submitted to a RET protocol without food restriction. However, rats were not able to perform exercise properly. The second and third sets were then randomly assigned into three experimental groups: 1) untrained control rats, 2) untrained rats submitted to fasting periods, and 3) rats submitted to RET including fasting periods before each RET session. While the second set of rats performed a short RET protocol (i.e., an adaptation protocol for 3 weeks), the third set of rats performed a longer RET protocol including overload (i.e., 8 weeks). After the short-term protocol, cumulative fasting periods promoted loss of weight (P<0.001). After the longer RET protocol, no difference was observed for body mass, extensor digitorum longus (EDL) morphology or skeletal muscle function (P>0.05 for all). Despite no effects on EDL mass, soleus muscle displayed significant atrophy in the fasting experimental groups (P<0.01). Altogether, these data indicate that fasting is a major limitation for RET in rats.