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Aims/hypothesis Adiponectin stimulates mitochondrial biogenesis through peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), a major regulator of mitochondrial biogenesis. MOTS-c (mitochondrial open reading frame of the 12S rRNA) is a biologically active mitochondrial-derived peptide encoded by mitochondrial DNA. It influences the mechanisms of obesity and diabetes. We hypothesised that the adiponectin pathway may regulate the production and/or secretion of MOTS-c in skeletal muscle. We aimed to determine whether exercise and adiponectin affect MOTS-c to improve insulin resistance in mice. Methods To investigate this hypothesis, we used wild-type C57BL/6 mice subjected to high-fat diet, an exercise regimen, and i.p. injection of recombinant mouse adiponectin (Acrp30) or MOTS-c, and adiponectin knockout (Adipoq −/− ) mice (C57BL/6 background) subjected to i.p. injection of Acrp30. C2C12 myotubes were also treated with sirtuin 1 (SIRT1) inhibitor, PGC-1α inhibitor, SIRT1 activator, plasmid-expressed active APPL1 (adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper), pcDNA-SIRT1, or siRNA against APPL1, SIRT1 or PGC-1α. Results In Adipoq -/mice, MOTS-c levels in the plasma and skeletal muscle were downregulated. In C2C12 myotubes, adiponectin increased the mRNA expression of MOTS-c. APPL1 protein level following adiponectin treatment positively correlated with MOTS-c protein and mRNA levels in C2C12 myotubes. SIRT1 overexpression increased the adiponectininduced mRNA and protein expression of MOTS-c, SIRT1 and PGC-1α. Pharmacologic and genetic inhibition of PGC-1α suppressed the increases in MOTS-c mRNA and protein levels induced by SIRT1 overexpression. In mice, plasma and skeletal muscle MOTS-c levels were significantly downregulated following high-fat-diet. Exercise and i.p. Acrp30 or MOTS-c increased MOTS-c levels and adiponectin mRNA and protein expression in the plasma and skeletal muscle. Conclusions/interpretation Our findings showed that the APPL1-SIRT1-PGC-1α pathway regulates the production and/or secretion of skeletal muscle MOTS-c by mediating adiponectin signalling. Our study provides an insight into the cellular and molecular pathways underlying the pathogenesis of diabetes and shows that MOTS-c is a potential novel therapeutic target in the treatment of diabetes. Keywords Adiponectin . Diabetes . Exercise-mediated signalling . Mitochondrial biogenesis . MOTS-c . Skeletal muscle Abbreviations Acrp30 Recombinant mouse adiponectin AMPK AMP-activated protein kinase APPL1 Adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 HFD High-fat diet KO Knockout MOTS-c Mitochondrial open reading frame of the 12S rRNA-c mtDNA Mitochondrial DNA PGC-1α Peroxisome proliferator-activated receptor-γ coactivator 1α Electronic supplementary material The online version of this article (

Exercise can increase skeletal muscle sensitivity to insulin, improve insulin resistance and regulate glucose homeostasis in rat models of type 2 diabetes. However, the potential mechanism remains poorly understood. In this study, we established a male Sprague–Dawley rat model of type 2 diabetes, with insulin resistance and β cell dysfunction, which was induced by a high-fat diet and low-dose streptozotocin to replicate the pathogenesis and metabolic characteristics of type 2 diabetes in humans. We also investigated the possible mechanism by which chronic and acute exercise improves metabolism, and the phosphorylation and expression of components of AMP-activated protein kinase (AMPK) and downstream components of phosphatidylinositol 3-kinase (PI3K) signaling pathways in the soleus. As a result, blood glucose, triglyceride, total cholesterol, and free fatty acid were significantly increased, whereas insulin level progressively declined in diabetic rats. Interestingly, chronic and acute exercise reduced blood glucose, increased phosphorylation and expression of AMPKα1/2 and the isoforms AMPKα1 and AMPKα2, and decreased phosphorylation and expression of AMPK substrate, acetyl CoA carboxylase (ACC). Chronic exercise upregulated phosphorylation and expression of AMPK upstream kinase, LKB1. But acute exercise only increased LKB1 expression. In particular, exercise reversed the changes in protein kinase C (PKC)ζ/λ phosphorylation, and PKCζ phosphorylation and expression. Additionally, exercise also increased protein kinase B (PKB)/Akt1, Akt2 and GLUT4 expression, but AS160 protein expression was unchanged. Chronic exercise elevated Akt (Thr308) and (Ser473) and AS160 phosphorylation. Finally, we found that exercise increased peroxisome proliferator-activated receptor-γ coactivator 1 (PGC1) mRNA expression in the soleus of diabetic rats. These results indicate that both chronic and acute exercise influence the phosphorylation and expression of components of the AMPK and downstream to PIK3 (aPKC, Akt), and improve GLUT4 trafficking in skeletal muscle. These data help explain the mechanism how exercise regulates glucose homeostasis in diabetic rats.

This study is aimed at investigating the effect of different exercise loads on the reproductive function of obese male mice and the underlying mechanisms. Male mice with high-fat diet-induced obesity were divided into obesity control (OC), obesity moderate-load exercise (OME), and obesity high-load exercise (OHE) groups. The OME and OHE groups were subjected to swimming exercise 5 days per week over a duration of 8 weeks, with the exercise load progressively increased to 2 h per day in the OME group and 2 h twice per day in the OHE group. In the OC group mice without exercise regimen, we observed a decrease in mRNA expression of antioxidant enzymes, increase in free radical products, upregulation of mRNA and protein expression of nuclear factor-κB and proinflammatory cytokines, inhibition of mRNA and protein expression of testosterone synthases, decrease in the serum testosterone level and sperm quality, and increase in sperm apoptosis. Although both moderate-load exercise and high-load exercise reduced body fat, only moderate-load exercise effectively alleviated obesity-induced oxidative stress, downregulated the expression of nuclear factor-κB and proinflammatory cytokines, and reversed the decrease in mRNA and protein expression of testosterone synthases, serum testosterone level, and sperm quality. These changes were not observed in the OHE group mice. Obesity-induced testicular oxidative stress and inflammatory response decreased testosterone synthesis and sperm quality. Moderate-load exercise alleviated the negative effect of obesity on male reproductive function by decreasing testicular oxidative stress and inflammatory responses. Although high-load exercise effectively reduced body fat, its effects on alleviating oxidative stress and improving male reproductive function were limited.

Aim. To investigate the effects of acute and chronic exercise on glucose and lipid metabolism in liver of rats with type 2 diabetes caused by a high fat diet and low dose streptozotocin (STZ). Methods. Animals were classified into control (CON), diabetes (DC), diabetic chronic exercise (DCE), and diabetic acute exercise (DAE) groups. Results. Compared to CON, the leptin levels in serum and liver and ACC phosphorylation were significantly higher in DC, but the levels of liver leptin receptor, AMPKα1/2, AMPKα1, and ACC proteins expression and phosphorylation were significantly lower in DC. In addition, the levels of liver glycogen reduced significantly, and the levels of TG and FFA increased significantly in DC compared to CON. Compared to DC, the levels of liver AMPKα1/2, AMPKα2, AMPKα1, and ACC phosphorylation significantly increased in DCE and DAE. However, significant increase of the level of liver leptin receptor and glycogen as well as significant decrease of the level of TG and FFA were observed only in DEC. Conclusion. Our study demonstrated that both acute and chronic exercise indirectly activated the leptin-AMPK-ACC signaling pathway and increased insulin sensitivity in the liver of type 2 diabetic rats. However, only chronic and long-term exercise improved glucose and lipid metabolism of the liver.