Skeletal muscle adiponectin induction depends on diet, muscle type/activity, and exercise modality in C57BL/6 mice

Chronic melatonin treatment improves obesity by inducing uncoupling of skeletal muscle SERCA-SLN mediated by CaMKII/AMPK/PGC1α pathway and mitochondrial biogenesis in female and male Zücker diabetic fatty rats

Melatonin acute treatment limits obesity of young Zücker diabetic fatty (ZDF) rats by non-shivering thermogenesis (NST). We recently showed melatonin chronically increases the oxidative status of vastus lateralis (VL) in both obese and lean adult male animals. The identification of VL skeletal muscle-based NST by uncoupling of sarcoendoplasmic reticulum Ca2+-ATPase (SERCA)- sarcolipin (SLN) prompted us to investigate whether melatonin is a SERCA-SLN calcium futile cycle uncoupling and mitochondrial biogenesis enhancer. Obese ZDF rats and lean littermates (ZL) of both sexes were subdivided into two subgroups: control (C) and 12 weeks orally melatonin treated (M) (10 mg/kg/day). Compared to the control groups, melatonin decreased the body weight gain and visceral fat in ZDF rats of both sexes. Melatonin treatment in both sex obese rats restored the VL muscle skin temperature and sensitized the thermogenic effect of acute cold exposure. Moreover, melatonin not only raised SLN protein levels in the VL of obese and lean rats of both sexes; also, the SERCA activity. Melatonin treatment increased the SERCA2 expression in obese and lean rats (both sexes), with no effects on SERCA1 expression. Melatonin increased the expression of thermogenic genes and proteins (PGC1-α, PPARγ, and NRF1). Furthermore, melatonin treatment enhanced the expression ratio of P-CaMKII/CaMKII and P-AMPK/AMPK. In addition, it rose mitochondrial biogenesis. These results provided the initial evidence that chronic oral melatonin treatment triggers the CaMKII/AMPK/PGC1α axis by upregulating SERCA2-SLN-mediated NST in ZDF diabetic rats of both sexes. This may further contribute to the body weight control and metabolic benefits of melatonin.

Molecular origin and biological effects of exercise mimetics

With the rapid development of sports science and molecular biology technology, academia refers to molecules or microorganisms that mimic or enhance the beneficial effects of exercise on the body, called "exercise mimetics." This review aims to clarify the concept and development history of exercise mimetics, and to define the concept of exercise mimetics by summarizing its characteristics and functions. Candidate molecules and drug targets for exercise mimetics are summarized, and the relationship between exercise mimetics and exercise is explained, as well as the targeting system and function of exercise mimetics. The main targeting systems for exercise mimetics are the exercise system, circulatory system, endocrine system, endocrine system, and nervous system, while the immune system is potential targeting systems. Finally, future research directions for exercise mimetics are discussed.

Bushen-Yizhi formula ameliorates mitochondrial dysfunction and oxidative stress via AMPK/Sirt1 signaling pathway in D-gal-induced aging rats

BACKGROUND

As a major risk factor for neurodegenerative diseases, aging has become a heavy health care burden worldwide. Age-related decline in mitochondrial function and oxidative stress is strongly associated with neurodegeneration. The previous study demonstrated that Bushen-Yizhi formula (BSYZ), a traditional Chinese medicine formula, is effective in reducing neurodegeneration.

METHODS

This study is the first to investigate the effect of BSYZ on D-gal-induced learning memory in rats. Secondly, the potential metabolic mechanism of BSYZ was explored by ¹H-NMR metabolomics analysis. Then based on the comparison of differential metabolites implied that BSYZ ameliorated mitochondrial dysfunction through choline metabolic pathway in D-gal-treated rats. Finally, pharmacological validation was conducted to explore the effects of BSYZ on D-gal-induced oxidative stress, neuroinflammation, and neuronal apoptosis.

RESULTS

Our data showed that BSYZ increased aspartate and betaine levels, while decreasing choline levels. Furthermore, BSYZ also increased the proteins level of CHDH and BHMT to regulate choline metabolic pathway. Meanwhile, BSYZ alleviated mitochondrial damage and oxidative stress, including enhanced ATP production and the ratio of NAD⁺/NADH, reduced the level of MDA, enhanced GSH and SOD activity, upregulated the expressions of p-AMPK, SIRT1 proteins. In addition, BSYZ downregulated the levels of inflammatory cytokines, such as TNF-α, IL-1β and IL-6, as well as suppressed Bcl-2 proteins family dependent apoptosis.

CONCLUSION

BSYZ treatment effectively rescues neurobehavioral impairment by improving mitochondrial dysfunction, oxidative stress, neuroinflammation and neuroapoptosis via AMPK/SIRT1 pathway in D-gal-induced aging.

Exercise training differently improve cardiac function and regulate myocardial mitophagy in ischemic and pressure-overloaded heart failure mice

NEW FINDINGS

What is the central question of this study? The cardioprotective effects of different aerobic exercises on chronic heart failure with different etiologies and whether mitophagy is involved remain elusive. What is the main finding and its importance? Moderate-intensity continuous training may be the "optimum" modality for improving cardiac structure and function in ischemic heart failure, while both moderate-intensity continuous training and high-intensity interval training were suitable for pressure-overloaded heart failure. Various mitophagy pathways especially PRKN-dependent pathways participated in the protective effects of exercise on heart failure.

ABSTRACT

The cardioprotective effects of different aerobic exercises on chronic heart failure with different etiologies and whether mitophagy is involved remain elusive. In the current research, left anterior descending ligation and transverse aortic constriction surgeries were used to establish mice models of heart failure, followed by 8 weeks of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). The results showed that MICT significantly improved ejection fraction (P < 0.05) and fractional shortening (P < 0.05), mitigated left ventricular end-systolic dimension (P < 0.01), brain natriuretic peptide (P < 0.0001), and fibrosis (P < 0.0001), while HIIT only decreased brain natriuretic peptide (P < 0.0001) and fibrosis (P < 0.0001) for ischemic heart failure. Both MICT and HIIT significantly increased ejection fraction (P < 0.0001) and fractional shortening (MICT: P < 0.001, HIIT: P < 0.0001), reduced left ventricular end-diastolic and end-systolic dimension, brain natriuretic peptide (P < 0.0001), and fibrosis (MICT: P < 0.01, HIIT: P < 0.0001), even HIIT was better in reducing brain natriuretic peptide on pressure-overloaded heart failure. Myocardial autophagy and mitophagy were compromised in heart failure, exercises improved myocardial autophagic flux and mitophagy inconsistently in heart failure with different etiologies. Significant correlations were found between multiple mitophagy pathways and cardioprotection of exercises. Collectively, MICT may be the "optimum" modality for ischemic heart failure, both MICT and HIIT (especially HIIT) were suitable for pressure-overloaded heart failure. Exercises differently improved myocardial autophagy/mitophagy and multiple mitophagy-related pathways were closely implicated in cardioprotection of exercises for chronic heart failure. This article is protected by copyright. All rights reserved.

Exercise Training Improves Memory Performance in Older Adults: A Narrative Review of Evidence and Possible Mechanisms

Exercise, neurotransmitters, growth factors, myokines, and potential effects on the brain.

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Nordic Walking Rather Than High Intensity Interval Training Reduced Myostatin Concentration More Effectively in Elderly Subjects and the Range of This Drop Was Modified by Metabolites of Vitamin D

The COVID-19 pandemic and subsequent self-isolation exacerbated the problem of insufficient amounts of physical activity and its consequences. At the same time, this revealed the advantage of vitamin D. Thus, there was a need to verify the effects of those forms of training that can be performed independently. In this study, we examined the effects of Nordic walking (NW) and high intensity interval training (HIIT) with regard to the impact of the metabolite vitamin D. We assigned 32 overweight adults (age = 61 ± 12 years) to one of two training groups: NW = 18 and HIIT = 14. Body composition assessment and blood sample collection were conducted before starting the training programs and a day after their completion. NW training induced a significant decrease in myostatin (p = 0.05) concentration; however, the range was dependent on the baseline concentrations of vitamin D metabolites. This drop was accompanied by a significant negative correlation with the decorin concentration. Unexpectedly, NW caused a decrement in both forms of osteocalcin: undercarboxylated (Glu-OC) and carboxylated-type (Gla-OC). The scope of Glu-OC changes was dependent on a baseline concentration of 25(OH)D₂ (r = −0.60, p = 0.01). In contrast, the HIIT protocol did not induce any changes. Overall results revealed that NW diminished the myostatin concentration and that this effect is more pronounced among adults with a sufficient concentration of vitamin D metabolites.

Adiponectin overexpression in C2C12 myocytes increases lipid oxidation and myofiber transition

Metabolic syndrome and obesity have detrimental effects on the metabolic function of the skeletal muscle. Mounting evidence indicates that patients with those conditions may present an increased ratio of glycolytic to oxidative fibers associated with a decrease in oxidative capacity. In this regard, adiponectin, a hormone mainly secreted by adipocytes that regulates glucose and lipid metabolism, has emerged as a myokine that could play an important role in this process. We aimed to investigate whether adiponectin overexpression in skeletal muscle might be a local protective mechanism, favoring fatty acid utilization. To that end, we generated an in vitro model of myocytes with upregulated endogenous adiponectin using a lentiviral carrier. We demonstrated that the adiponectin-transduced myocytes were able to produce and secrete fully functional adiponectin complexes. Adiponectin overexpression remarkably upregulated the mRNA level of myogenic regulatory factors as well as genes implicated in lipolysis (HSL, ATGL) and cellular and mitochondrial fatty acid transport (LPL, CD36, CPT1B). This was accompanied by increased isoproterenol-induced lipolysis and β-oxidation and reduced lipogenesis, whereas insulin-stimulated glucose uptake was unaltered in transduced myocytes. Lastly, the relative expression of the more glycolytic myofibers (MyHC IIb) compared to the more oxidative ones (MyHC I) was notably reduced. Our results showed that the released adiponectin acted in an autocrine/paracrine manner, increasing lipid oxidation in myocytes and leading to a transition of myofibers from the glycolytic to the oxidative type. In conclusion, muscle adiponectin overexpression might be a way to relieve muscle diseases caused by oxidative muscle fiber deficiency.

Skeletal muscle adiponectin induction in obesity and exercise

Recent scientific efforts have focused on the detrimental effects that obesity has on the metabolic function of skeletal muscles and whether exercise can improve this dysfunction. In this regard, adiponectin, with important metabolic functions (e.g. insulin-sensitizer and anti-inflammatory), has been recently described as a myokine that acts in an autocrine/paracrine manner. Earlier studies reported that muscle adiponectin could be induced by pro-inflammatory mediators (e.g. lipopolysaccharide), cytokines, and high-fat diets, providing a protective mechanism of this tissue against metabolic insults. However, when metabolic insults such as high-fat diets are sustained this protective response becomes dysregulated, making the skeletal muscle susceptible to metabolic impairments. Recent studies have suggested that exercise could prevent or even reverse this process. Considering that most scientific knowledge on adiponectin dysregulation in obesity is from the study of adipose tissue, the present review summarizes and discusses the literature available to date regarding the effects of obesity on skeletal muscle adiponectin induction, along with the potential effects of different exercise prescriptions on this response in an obesity context.

Effects of Moderate- and High-Intensity Chronic Exercise on the Adiponectin Levels in Slow-Twitch and Fast-Twitch Muscles in Rats

Background and objectives: Adipose tissue and skeletal muscle secrete adiponectin, a hormone abundantly secreted by adipocytes, that through the adiponectin receptor, regulate glucose and lipid metabolism. Adiponectin appears to protect skeletal muscles from inflammatory damage induced by oxidative stress. It has been suggested that decreased adiponectin levels could be associated with pathologic conditions, including obesity and diabetes. Furthermore, some studies suggest that exercise could have a beneficial effect by increasing adiponectin levels, but this observation remains controversial. It is also unknown if physical exercise modifies adiponectin expression in skeletal muscles. The aim of this study was to investigate the effect of chronic exercise on serum adiponectin and adiponectin expression in slow-twitch (soleus) and fast-twitch (plantaris) muscles in healthy rats. Materials and methods: Two-month-old male Wistar rats were randomly divided into three groups with n = 6 in each group: control (C), moderate-intensity training (MIT), and high-intensity training (HIT). The rats were conditioned to run on a treadmill for the 8-week period. Forty-eight hours after the last session, blood samples were collected for adiponectin measurements and total RNA was isolated from plantaris and soleus muscles to measure by RT-qPCR adiponectin receptor 1 and adiponectin mRNA expression level. Results: MIT and HIT groups had reduced adiponectin protein levels in serum and the plantaris muscle, but not changes in adiponectin protein were observed in the soleus muscle. No significant differences in Adiponectin receptor 1 (AdipoR1) gene expression were observed following intense or moderate exercise in either muscle group studied. Conclusions: Our study shows that decreasing levels of circulating adiponectin is a result of physical exercise and should not be generalized as a predictive marker of disease.

Adiponectin-Consideration for its Role in Skeletal Muscle Health

Adiponectin regulates metabolism through blood glucose control and fatty acid oxidation, partly mediated by downstream effects of adiponectin signaling in skeletal muscle. More recently, skeletal muscle has been identified as a source of adiponectin expression, fueling interest in the role of adiponectin as both a circulating adipokine and a locally expressed paracrine/autocrine factor. In addition to being metabolically responsive, skeletal muscle functional capacity, calcium handling, growth and maintenance, regenerative capacity, and susceptibility to chronic inflammation are all strongly influenced by adiponectin stimulation. Furthermore, physical exercise has clear links to adiponectin expression and circulating concentrations in healthy and diseased populations. Greater physical activity is generally related to higher adiponectin expression while lower adiponectin levels are found in inactive obese, pre-diabetic, and diabetic populations. Exercise training typically restores plasma adiponectin and is associated with improved insulin sensitivity. Thus, the role of adiponectin signaling in skeletal muscle has expanded beyond that of a metabolic regulator to include several aspects of skeletal muscle function and maintenance critical to muscle health, many of which are responsive to, and mediated by, physical exercise.