Role of exercise training on insulin resistance and TNF-α in high-fat diet rats

Objective Obesity is becoming increasingly prevalent and is an important contributor to the worldwide burden of diseases. It is widely accepted that exercise training is beneficial for the prevention and treatment of obesity. However, the underlying mechanism by which exercise training improving skeletal muscle lipid metabolism is still not fully described. Sestrins (Sestrin1-3) are highly conserved stress-inducible protein. Concomitant ablation of Sestrin2 and Sestrin3 has been reported to provoke hepatic mTORC1/S6K1 activation and insulin resistance even without nutritional overload and obesity, implicating that Sestrin2 and Sestrin3 have an important homeostatic function in the control of mammalian glucose and lipid metabolism. Our previous results demonstrated that physical exercise increased Sestrin2 expression in murine skeletal muscle, while the role of Sestrin2 in regulating lipid metabolism remains unknown. SH2 domain containing inositol 5-phosphatase (SHIP2) acts as a negative regulator of the insulin signaling both in vitro and in vivo. An increased expression of SHIP2 inhibits the insulin-induced Akt activation, glucose uptake, and glycogen synthesis in 3T3-L1 adipocytes, L6 myotubes and tissues of animal models. Alterations of SHIP2 expression and/or enzymatic function appear to have a profound impact on the development of insulin resistance. However, the regulatory function of SHIP2 in lipid metabolism after exercise remains unclear. It has been reported that SHIP2 modulated lipid metabolism through regulating the activity of c-Jun N-terminal kinase (JNK) and Sterol regulatory element-binding protein-1 (SREBP-1). JNK is a subclass of mitogen-activated protein kinase (MAPK) signaling pathway in mammalian cells and plays a crucial role in metabolic changes and inflammation associated with a high-fat diet. Inhibition of JNK reduces lipid deposition and proteins level of fatty acid de novo synthesis in liver cells. It has been reported that Sestrin2 regulated the phosphorylation of JNK, however the underlying mechanism remains unclear. SREBP-1 is important in regulating cholesterol biosynthesis and uptake and fatty acid biosynthesis, and SREBP-1 expression produces two different isoforms, SREBP-1a and SREBP-1c. SREBP-1c is responsible for regulating the genes required for de novo lipogenesis and its expression is regulated by insulin. SREBP-1a regulates genes related to lipid and cholesterol production and its activity is regulated by sterol levels in the cell. Altogether, the purpose of this study was to explore the effect and underlying mechanism of Sestrin2 on lipid accumulation after exercise training. Methods Male wild type and SESN2−/− mice were divided into normal chow (NC) and high-fat diet (HFD) groups to create insulin resistance mice model. After 8 weeks the IR model group was then divided into HFD sedentary control and HFD exercise groups (HE). Mice in HE group underwent 6-week treadmill exercise to reveal the effect of exercise training on lipid metabolism in insulin resistance model induced by HFD. We explored the mechanism through which Sestrin2 regulated lipid metabolism in vitro by supplying palmitate, overexpressing or inhibiting SESNs, SHIP2 and JNK in myotubes. Results We found that 6-week exercise training decreased body weight, BMI and fat mass in wild type and SESN2-/- mice after high-fat diet (HFD) feeding. And exercise training decreased the level of plasma glucose, serum insulin, triglycerides and free fatty acids in wild type but not in Sestrin2-/- mice. Lipid droplet in skeletal muscle was also decreased in wild type but did not in Sestrin2-/- mice. Moreover, exercise training increased the proteins expression involved in fatty acid oxidation and decreased the proteins which related to fatty acid de novo synthesis. The results of oil red staining and the change of proteins related to fatty acid de novo synthesis and beta oxidation in myotubes treated with palmitate, Ad-SESN2 and siRNA-Sestrin2 were consisted with the results in vivo, which suggested that Sestrin2 was a key regulator in lipid metabolism. Exercise training increased Sestrin2 expression and reversed up-regulation of SHIP2 and pJNK induced by HFD in wild type mice but not in Sestrin2-/- mice. In parallel, overexpression of Sestrin2 decreased the level of SHIP2 and pJNK induced by palmitate while Sestrin2 knock down by siRNA-Sestrin2 treatment did not change the expression of SHIP2 and pJNK, which suggested that Sestrin2 modulated SHIP2 and JNK in the state of abnormal lipid metabolism. Inhibition of SHIP2 reduced the activity of JNK, increased lipid accumulation and the proteins of fatty acid synthesis after palmitate treatment and over expression of Sestrin2, which suggest that Sestrin2 modulated lipid metabolism through SHIP2/JNK pathway. Conclusions Sestrin2 plays an important role in improving lipid metabolism after exercise training, and Sestrin2 regulates lipid metabolism by SHIP2-JNK pathway in skeletal muscle.

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Osteocalcin prevents insulin resistance, hepatic inflammation and autophagy associated with high-fat diet induced fatty liver hemorrhagic syndrome in aged laying hens

10.21203/rs.3.rs-18321/v1 ◽

2020 ◽

Author(s):

Xiaoling Wu ◽

Xinyu Zou ◽

Mi Zhang ◽

Haiqiang Hu ◽

Xueliang Wei ◽

...

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Inflammatory Reaction ◽

High Fat Diet ◽

Laying Hens ◽

Density Lipoprotein ◽

Inflammatory Factors ◽

Pathological Changes ◽

High Fat ◽

Tnf Α

Abstract Background: Osteocalcin (OCN), as an energy-regulating hormone, involves in preventing nonalcoholic steatohepatitis. Laying hens have been used as an animal model for investigating liver function and related metabolic disordersas that the synthesis of fat in laying hens is much faster than in mammals with limited adipose tissue. The aim of this study was to investigate the effects of OCN on fatty liver hemorrhagic syndrome (FLHS) in aged laying hens. Methods: Thirty 68-week-old White Plymouth laying hens were randomly assigned into conventional single-bird cages, and the cages were randomly allocated into one of three treatments: normal diet (ND + vehicle , ND+V), high-fat diet (HFD + vehicle, HFD+V), and HFD + OCN (3 μg/bird, 1 time/2 days, i.m.) for 40 days. At experimental day 30, oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were performed. At the end of experiment, the hens were euthanized followed blood collection. The plasma aspartate transaminase (AST), alkaline phosphatase (ALP), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were measured using an automatic biochemistry analyzer. Pathological changes in the liver were examined under both light and transmission electron microscopes. The plasma inflammatory factors including interleukin-1 (IL-1), IL-6, and tumor Necrosis Factor-alpha (TNF-α) were analyzed by ELISA, and the gene expressions of these inflammatory factors in the liver were analyzed by Real-time PCR. And oxidative stress was evaluated using Malondialdehyde (MDA) and Glutathione peroxidase (GSH-Px) assay kits. Results: The results showed HFD hens had more severe liver haemorrhage and fibrosis than ND hens. The ultra-microstructural examination showed that hepatocytes of HFD hens appeared necrotic pyknosis associated with great intracellular electron, mitochondrial swelling, shrunk nucleus and absence of autolysosomes. OCN mitigated these pathological changes by improved HFD hens’ insulin resistance via alleviating the glucose intolerence and improving insulin sensitivity; inhibited HFD-induced oxidative stress as evidenced by decreased liver concentrations of MDA but increased GSH-Px; and reduced the inflammatory reaction with reducing blood IL-6 and TNF-α concentrations and mRNA expressions. Conclusion: These results suggest a high-fat diet promotes the FLHS development in aged hens, while OCN prevents the FLHS process through inhibiting insulin resistance, inflammatory reaction, oxidative stress and fibrosis, and acting autophagy.

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Combined effect of canagliflozin and exercise training on high-fat diet-fed mice

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00401.2019 ◽

2020 ◽

Vol 318 (4) ◽

pp. E492-E503

Author(s):

Kenichi Tanaka ◽

Hirokazu Takahashi ◽

Sayaka Katagiri ◽

Kazuyo Sasaki ◽

Yujin Ohsugi ◽

...

Keyword(s):

Gene Expression ◽

Insulin Resistance ◽

Skeletal Muscle ◽

Exercise Training ◽

Fatty Liver ◽

High Fat Diet ◽

Characteristic Change ◽

High Fat ◽

Nonalcoholic Fatty Liver ◽

Sodium Glucose Cotransporter

Sodium-glucose cotransporter 2 inhibitors (SGLT2is) have been reported to improve obesity, diabetes, and nonalcoholic fatty liver disease (NAFLD) in addition to exercise training, whereas the combined effects remain to be elucidated fully. We investigated the effect of the combination of the SGLT2i canagliflozin (CAN) and exercise training in high-fat diet-induced obese mice. High-fat diet-fed mice were housed in normal cages (sedentary; Sed) or wheel cages (WCR) with or without CAN (0.03% of diet) for 4 wk. The effects on obesity, glucose metabolism, and hepatic steatosis were evaluated in four groups (Control/Sed, Control/WCR, CAN/Sed, and CAN/WCR). Numerically additive improvements were found in body weight, body fat mass, blood glucose, glucose intolerance, insulin resistance, and the fatty liver of the CAN/WCR group, whereas CAN increased food intake and reduced running distance. Exercise training alone, CAN alone, or both did not change the weight of skeletal muscle, but microarray analysis showed that each resulted in a characteristic change of gene expression in gastrocnemius muscle. In particular, in the CAN/WCR group, there was acceleration of the angiogenesis pathway and suppression of the adipogenesis pathway compared with the CAN/Sed group. In conclusion, the combination of an SGLT2i and exercise training improves obesity, insulin resistance, and NAFLD in an additive manner. Changes of gene expression in skeletal muscle may contribute, at least in part, to the improvement of obesity and insulin sensitivity.

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The antihyperglycemic effect of curcumin in high fat diet fed rats. Role of TNF-α and free fatty acids

Food and Chemical Toxicology ◽

10.1016/j.fct.2011.02.004 ◽

2011 ◽

Vol 49 (5) ◽

pp. 1129-1140 ◽

Cited By ~ 93

Author(s):

Mohamed A. El-Moselhy ◽

Ashraf Taye ◽

Sara Shaaban Sharkawi ◽

Suzan F.I. El-Sisi ◽

Ahmed Fahmy Ahmed

Keyword(s):

Fatty Acids ◽

Free Fatty Acids ◽

High Fat Diet ◽

High Fat ◽

Antihyperglycemic Effect ◽

Tnf Α

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CD44 contributes to hyaluronan-mediated insulin resistance in skeletal muscle of high-fat-fed C57BL/6 mice

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00215.2019 ◽

2019 ◽

Vol 317 (6) ◽

pp. E973-E983 ◽

Cited By ~ 3

Author(s):

Annie Hasib ◽

Chandani K. Hennayake ◽

Deanna P. Bracy ◽

Aimée R. Bugler-Lamb ◽

Louise Lantier ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

High Fat Diet ◽

Critical Role ◽

Chow Diet ◽

Wild Type ◽

High Fat ◽

Insulin Resistant ◽

Beneficial Effects

Extracellular matrix hyaluronan is increased in skeletal muscle of high-fat-fed insulin-resistant mice, and reduction of hyaluronan by PEGPH20 hyaluronidase ameliorates diet-induced insulin resistance (IR). CD44, the main hyaluronan receptor, is positively correlated with type 2 diabetes. This study determines the role of CD44 in skeletal muscle IR. Global CD44-deficient ( cd44−/−) mice and wild-type littermates ( cd44+/+) were fed a chow diet or 60% high-fat diet for 16 wk. High-fat-fed cd44−/− mice were also treated with PEGPH20 to evaluate its CD44-dependent action. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp (ICv). High-fat feeding increased muscle CD44 protein expression. In the absence of differences in body weight and composition, despite lower clamp insulin during ICv, the cd44−/− mice had sustained glucose infusion rate (GIR) regardless of diet. High-fat diet-induced muscle IR as evidenced by decreased muscle glucose uptake (Rg) was exhibited in cd44+/+ mice but absent in cd44−/− mice. Moreover, gastrocnemius Rg remained unchanged between genotypes on chow diet but was increased in high-fat-fed cd44−/− compared with cd44+/+ when normalized to clamp insulin concentrations. Ameliorated muscle IR in high-fat-fed cd44−/− mice was associated with increased vascularization. In contrast to previously observed increases in wild-type mice, PEGPH20 treatment in high-fat-fed cd44−/− mice did not change GIR or muscle Rg during ICv, suggesting a CD44-dependent action. In conclusion, genetic CD44 deletion improves muscle IR, and the beneficial effects of PEGPH20 are CD44-dependent. These results suggest a critical role of CD44 in promoting hyaluronan-mediated muscle IR, therefore representing a potential therapeutic target for diabetes.

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