Combination of exercise training and diet restriction normalizes limited exercise capacity and impaired skeletal muscle function in diet-induced diabetic mice

A combination of exercise and calorie restriction improves the development of obesity-related type 2 diabetes mellitus in KKAy mice

We observed that exercise and calorie restriction reduced the body weight and blood glucose levels, concurrently improving insulin resistance and glucose tolerance in obese/diabetic model KKAy mice. Analysis of gene expression in the skeletal muscle showed enhanced mRNA levels of GLUT4 (glucose uptake), ATGL (lipolytic enzyme), and slow-twitch myosin heavy chain, which may contribute to the antiobesity and antidiabetic effects.

The Effects of Exercise and Restriction of Sugar-Sweetened Beverages on Muscle Function and Autophagy Regulation in High-Fat High-Sucrose-Fed Obesity Mice

BACKGROUND

Autophagy maintains muscle mass and healthy skeletal muscles. Several recent studies have associated sugar-sweetened beverage (SSB) consumption with diseases. We investigated whether muscle dysfunction due to obesity could be restored by SSB restriction (SR) alone or in combination with exercise (EX) training.

METHODS

Obese mice were subjected to SR combined with treadmill EX. Intraperitoneal glucose tolerance test, grip strength test, hanging time test, and body composition analysis were performed. Triglyceride (TG) and total cholesterol (TC) serum concentrations and TG concentrations in quadriceps muscles were analyzed. Western blot and reverse transcription-quantitative polymerase chain reaction helped analyze autophagy-related protein and mRNA expression, respectively.

RESULTS

SR alone had no significant effect on fasting blood glucose levels, glucose tolerance, and muscle function. However, it had effect on serum TC, serum TG, and BCL2 interacting protein 3 expression. SR+EX improved glucose tolerance and muscle function and increased serum TC utilization than SR alone. SR+EX reduced P62 levels, increased glucose transporter type 4 and peroxisome proliferator-activated receptor γ coactivator-1α protein expression, and improved grip strength relative to the high-fat and high-sucrose liquid (HFHS) group, and this was not observed in the HFHS+EX group.

CONCLUSION

SR induced mitophagy-related protein expression in quadriceps, without affecting muscle function. And, the combination of SR and EX activated mitophagy-related proteins and improved muscle function.

Perivascular adipose tissue and microvascular endothelial dysfunction in obese mice: Beneficial effects of aerobic exercise in adiponectin receptor (AdipoR1) and peNOSSer1177

In the present study, we aim to investigate the effects of aerobic physical training on perivascular adipose tissue (PVAT)-induced microvascular dysfunction of the femoral artery in obese mice. Microvascular reactivity was evaluated in control sedentary (c-SD), obese sedentary (o-SD) and obese trained (o-TR) male mice (C57BL6/JUnib), in the absence (PVAT-) or the presence (PVAT+) of femoral artery PVAT. We also analyzed protein expression, vascular nitric oxide (NO) production and reactive oxygen species (ROS) generation in PVAT. The blood glucose, triglycerides and total cholesterol levels were increased in the o-SD group, when compared with the c-SD group. The maximal responses and the potency to acetylcholine (ACh) were decreased in PVAT+ compared with PVAT- rings in the o-SD group, accompanied by a decrease in vascular protein expression of peNOS_Ser1177 , Cu/Zn-SOD, leptin receptor (Ob-R) and adiponectin receptor (AdipoR1). The protein expression of leptin increased and that of adiponectin decreased in PVAT. Additionally, vascular NO production was reduced and ROS generation was enhanced in PVAT in the o-SD group. Aerobic exercise training was effective for normalizing ACh relaxation response, vascular NO production and ROS generation in the o-TR group. It partially re-established the vascular protein expression of peNOS_Ser1177 and the PVAT leptin; normalized the vascular Cu/Zn-SOD and AdipoR1 protein expressions. In obese sedentary mice, the presence of PVAT is involved in the process of microvascular dysfunction of the femoral artery in a pathway associated with increased inflammation and ROS generation. The aerobic exercise training normalized the vascular response, the NO production and/or bioavailability and oxidative stress, with improved vascular expressions of Cu/Zn-SOD, peNOS_ser1177 , and AdipoR1.

Premedication with pioglitazone prevents doxorubicin-induced left ventricular dysfunction in mice

BACKGROUND

Doxorubicin (DOX) is widely used as an effective chemotherapeutic agent for cancers; however, DOX induces cardiac toxicity, called DOX-induced cardiomyopathy. Although DOX-induced cardiomyopathy is known to be associated with a high cumulative dose of DOX, the mechanisms of its long-term effects have not been completely elucidated. Pioglitazone (Pio) is presently contraindicated in patients with symptomatic heart failure owing to the side effects. The concept of drug repositioning led us to hypothesize the potential effects of Pio as a premedication before DOX treatment, and to analyze this hypothesis in mice.

METHODS

First, for the hyperacute (day 1) and acute (day 7) DOX-induced dysfunction models, mice were fed a standard diet with or without 0.02% (wt/wt) Pio for 5 days before DOX treatment (15 mg/kg body weight [BW] via intraperitoneal [i.p.] administration). The following 3 treatment groups were analyzed: standard diet + vehicle (Vehicle), standard diet + DOX (DOX), and Pio + DOX. Next, for the chronic model (day 35), the mice were administrated DOX once a week for 5 weeks (5 mg/kg BW/week, i.p.).

RESULTS

In the acute phase after DOX treatment, the percent fractional shortening of the left ventricle (LV) was significantly decreased in DOX mice. This cardiac malfunction was improved in Pio + DOX mice. In the chronic phase, we observed that LV function was preserved in Pio + DOX mice.

CONCLUSIONS

Our findings may provide a new pathophysiological explanation by which Pio plays a role in the treatment of DOX-induced cardiomyopathy, but the molecular links between Pio and DOX-induced LV dysfunction remain largely elusive.

Brain-Derived Neurotrophic Factor Improves Impaired Fatty Acid Oxidation Via the Activation of Adenosine Monophosphate-Activated Protein Kinase-ɑ - Proliferator-Activated Receptor-r Coactivator-1ɑ Signaling in Skeletal Muscle of Mice With Heart Failure

BACKGROUND

We recently reported that treatment with rhBDNF (recombinant human brain-derived neurotrophic factor) improved the reduced exercise capacity of mice with heart failure (HF) after myocardial infarction (MI). Since BDNF is reported to enhance fatty acid oxidation, we herein conducted an in vivo investigation to determine whether the improvement in exercise capacity is due to the enhancement of the fatty acid oxidation of skeletal muscle via the AMPKα-PGC1α (adenosine monophosphate-activated protein kinase-ɑ-proliferator-activated receptor-r coactivator-1ɑ) axis.

METHODS

MI and sham operations were conducted in C57BL/6J mice. Two weeks postsurgery, we randomly divided the MI mice into groups treated with rhBDNF or vehicle for 2 weeks. AMPKα-PGC1α signaling and mitochondrial content in the skeletal muscle of the mice were evaluated by Western blotting and transmission electron microscopy. Fatty acid β-oxidation was examined by high-resolution respirometry using permeabilized muscle fiber. BDNF-knockout mice were treated with 5-aminoimidazole-4-carboxamide-1-beta-d-riboruranoside, an activator of AMPK.

RESULTS

The rhBDNF treatment significantly increased the expressions of phosphorylated AMPKα and PGC1α protein and the intermyofibrillar mitochondrial density in the MI mice. The lowered skeletal muscle mitochondrial fatty acid oxidation was significantly improved in the rhBDNF-treated MI mice. The reduced exercise capacity and mitochondrial dysfunction of the BDNF-knockout mice were improved by 5-aminoimidazole-4-carboxamide-1-beta-d-riboruranoside.

CONCLUSIONS

Beneficial effects of BDNF on the exercise capacity of mice with HF are mediated through an enhancement of fatty acid oxidation via the activation of AMPKα-PGC1α in skeletal muscle. BDNF may become a therapeutic option to improve exercise capacity as an alternative or adjunct to exercise training.

Abnormalities of Skeletal Muscle, Adipocyte Tissue, and Lipid Metabolism in Heart Failure: Practical Therapeutic Targets

Chronic diseases, including heart failure (HF), are often accompanied with skeletal muscle abnormalities in both quality and quantity, which are the major cause of impairment of the activities of daily living and quality of life. We have shown that skeletal muscle abnormalities are a hallmark of HF, in which metabolic pathways involving phosphocreatine and fatty acids are largely affected. Not only in HF, but the dysfunction of fatty acid metabolism may also occur in many chronic diseases, such as arteriosclerosis, as well as through insufficient physical exercise. Decreased fatty acid catabolism affects adenosine triphosphate (ATP) production in mitochondria, via decreased activity of the tricarboxylic acid cycle; and may cause abnormal accumulation of adipose tissue accompanied with hyperoxidation and ectopic lipid deposition. Such impairments of lipid metabolism are in turn detrimental to skeletal muscle, which is hence a chicken-and-egg problem between skeletal muscle and HF. In this review, we first discuss skeletal muscle abnormalities in HF, including sarcopenia; particularly their association with lipid metabolism and adipose tissue. On the other hand, the precise mechanisms involved in metabolic reprogramming and dysfunction are beginning to be understood, and an imbalance of daily nutritional intake of individuals has been found to be a causative factor for the development and worsening of HF. Physical exercise has long been known to be beneficial for the prevention and even treatment of HF. Again, the molecular mechanisms by which exercise promotes skeletal muscle as well as cardiac muscle functions are being clarified by recent studies. We propose that it is now the time to develop more “natural” methods to prevent and treat HF, rather than merely relying on drugs and medical interventions. Further analysis of the basic design of and molecular mechanisms involved in the human body, particularly the inextricable association between physical exercise and the integrity and functional plasticity of skeletal and cardiac muscles is required.

Enhanced liver but not muscle OXPHOS in diabetes and reduced glucose output by complex I inhibition

Mitochondrial function is critical in energy metabolism. To fully capture how the mitochondrial function changes in metabolic disorders, we investigated mitochondrial function in liver and muscle of animal models mimicking different types and stages of diabetes. Type 1 diabetic mice were induced by streptozotocin (STZ) injection. The db/db mice were used as type 2 diabetic model. High-fat diet-induced obese mice represented pre-diabetic stage of type 2 diabetes. Oxidative phosphorylation (OXPHOS) of isolated mitochondria was measured with Clark-type oxygen electrode. Both in early and late stages of type 1 diabetes, liver mitochondrial OXPHOS increased markedly with complex IV-dependent OXPHOS being the most prominent. However, ATP, ADP and AMP contents in the tissue did not change. In pre-diabetes and early stage of type 2 diabetes, liver mitochondrial complex I and II-dependent OXPHOS increased greatly then declined to almost normal at late stage of type 2 diabetes, among which alteration of complex I-dependent OXPHOS was the most significant. In contrast, muscle mitochondrial OXPHOS in HFD, early-stage type 1 and 2 diabetic mice, did not change. In vitro, among inhibitors to each complex, only complex I inhibitor rotenone decreased glucose output in primary hepatocytes without cytotoxicity both in the absence and presence of oleic acid (OA). Rotenone affected cellular energy state and had no effects on cellular and mitochondrial reactive oxygen species production. Taken together, the mitochondrial OXPHOS of liver but not muscle increased in obesity and diabetes, and only complex I inhibition may ameliorate hyperglycaemia via lowering hepatic glucose production.

Impacts of exercise interventions on different diseases and organ functions in mice

Background

In recent years, much evidence has emerged to indicate that exercise can benefit people when performed properly. This review summarizes the exercise interventions used in studies involving mice as they are related to special diseases or physiological status. To further understand the effects of exercise interventions in treating or preventing diseases, it is important to establish a template for exercise interventions that can be used in future exercise-related studies.

Methods

PubMed was used as the data resource for articles. To identify studies related to the effectiveness of exercise interventions for treating various diseases and organ functions in mice, we used the following search language: (exercise [Title] OR training [Title] OR physical activity [Title]) AND (mice [title/abstract] OR mouse [title/abstract] OR mus [title/abstract]). To limit the range of search results, we included 2 filters: one that limited publication dates to "in 10 years" and one that sorted the results as "best match". Then we grouped the commonly used exercise methods according to their similarities and differences. We then evaluated the effectiveness of the exercise interventions for their impact on diseases and organ functions in 8 different systems.

Results

A total of 331 articles were included in the analysis procedure. The articles were then segmented into 8 systems for which the exercise interventions were used in targeting and treating disorders: motor system (60 studies), metabolic system (45 studies), cardio-cerebral vascular system (58 studies), nervous system (74 studies), immune system (32 studies), respiratory system (7 studies), digestive system (1 study), and the system related to the development of cancer (54 studies). The methods of exercise interventions mainly involved the use of treadmills, voluntary wheel-running, forced wheel-running, swimming, and resistance training. It was found that regardless of the specific exercise method used, most of them demonstrated positive effects on various systemic diseases and organ functions. Most diseases were remitted with exercise regardless of the exercise method used, although some diseases showed the best remission effects when a specific method was used.

Conclusion

Our review strongly suggests that exercise intervention is a cornerstone in disease prevention and treatment in mice. Because exercise interventions in humans typically focus on chronic diseases, national fitness, and body weight loss, and typically have low intervention compliance rates, it is important to use mice models to investigate the molecular mechanisms underlying the health benefits from exercise interventions in humans.

Possible Role of NADPH Oxidase 4 in Angiotensin II-Induced Muscle Wasting in Mice

Background: Muscle wasting is a debilitating phenotype associated with chronic heart failure (CHF). We have previously demonstrated that angiotensin II (AII) directly induces muscle wasting in mice through the activation of NADPH oxidase (Nox). In this study, we tested the hypothesis that deficiency of NADPH oxidase 4 (Nox4), a major source of oxidative stress, ameliorates AII-induced muscle wasting through the regulation of redox balance. Methods and Results: Nox4 knockout (KO) and wild-type (WT) mice were used. At baseline, there were no differences in physical characteristics between the WT and KO mice. Saline (vehicle, V) or AII was infused via osmotic minipumps for 4 weeks, after which, the WT + AII mice showed significant increases in Nox activity and NOX4 protein compared with the WT + V mice, as well as decreases in body weight, gastrocnemius muscle weight, and myocyte cross-sectional area. These changes were significantly attenuated in the KO + AII mice (27 ± 1 vs. 31 ± 1 g, 385 ± 3 vs. 438 ± 13 mg, and 1,330 ± 30 vs. 2281 ± 150 μm², respectively, all P < 0.05). The expression levels of phospho-Akt decreased, whereas those of muscle RING Finger-1 (MuRF-1) and MAFbx/atrogin-1 significantly increased in the WT + AII mice compared with the WT + V mice. Furthermore, nuclear factor erythroid-derived 2-like 2 (Nrf2) and the expression levels of Nrf2-regulated genes significantly decreased in the WT + AII mice compared with the WT + V mice. These changes were significantly attenuated in the KO + AII mice (P < 0.05). Conclusion: Nox4 deficiency attenuated AII-induced muscle wasting, partially through the regulation of Nrf2. The Nox4-Nrf2 axis may play an important role in the development of AII-induced muscle wasting.

Deletion of NAD(P)H Oxidase 2 Prevents Angiotensin II-Induced Skeletal Muscle Atrophy

Skeletal muscle atrophy is induced by an imbalance between protein synthesis and degradation. Our previous studies reported that angiotensin II (AII) directly induced muscle atrophy in mice. This study investigated the role of NAD(P)H oxidase 2 (Nox2) activation by AII in the induction of skeletal muscle atrophy. For 4 weeks, either saline (vehicle: V) or AII (1000 ng kg⁻¹ min⁻¹) was infused into male wild-type (WT) and Nox2 knockout (KO) mice via osmotic minipumps. Experiments were performed in the following 4 groups: WT + V, KO + V, WT + AII, and KO + AII. Body weight, muscle weight, and myocyte cross-sectional area were significantly decreased in WT + AII compared to WT + V mice, and these changes were not observed in KO + AII mice. Akt phosphorylation of Ser473 and p70S6K of Thr389 was decreased, gene expression levels of MuRF-1 and atrogin-1 were increased in WT + AII compared to WT + V, and these changes were significantly attenuated in KO + AII mice. The deletion of Nox2 prevented AII-induced skeletal muscle atrophy via improving the balance between protein synthesis and degradation. Therefore, Nox2 may be a therapeutic target for AII-induced skeletal muscle atrophy.

The effects of exercise training and caloric restriction on the cardiac oxytocin natriuretic peptide system in the diabetic mouse

BACKGROUND

Regular exercise training (ET) and caloric restriction (CR) are the frontline strategies in the treatment of type 2 diabetes mellitus with the aim at reducing cardiometabolic risk. ET and CR improve body weight and glycemic control, and experimental studies indicate that these paradigms afford cardioprotection. In this study, the effects of combined ET and CR on the cardioprotective oxytocin (OT)-natriuretic peptide (NP) system were determined in the db/db mouse, a model of type 2 diabetes associated with insulin resistance, hyperglycemia, and obesity.

METHODS

Five-week-old male db/db mice were assigned to the following groups: sedentary, ET, and ET + CR. Nonobese heterozygote littermates served as controls. ET was performed on a treadmill at moderate intensity, and CR was induced by reducing food intake by 30% of that consumed by sedentary db/db mice for a period of 8 weeks.

RESULTS

After 8 weeks, only ET + CR, but not ET, slightly improved body weight compared to sedentary db/db mice. Regardless of the treatment, db/db mice remained hyperglycemic. Hearts from db/db mice demonstrated reduced expression of genes linked to the cardiac OT-NP system. In fact, compared to control mice, mRNA expression of GATA binding protein 4 (GATA4), OT receptor, OT, brain NP, NP receptor type C, and endothelial nitric oxide synthase (eNOS) was decreased in hearts from sedentary db/db mice. Both ET alone and ET + CR increased the mRNA expression of GATA4 compared to sedentary db/db mice. Only ET combined with CR produced increased eNOS mRNA and protein expression.

CONCLUSION

Our data indicate that enhancement of eNOS by combined ET and CR may improve coronary endothelial vasodilator dysfunction in type 2 diabetes but did not prevent the downregulation of cardiac expression in the OT-NP system, possibly resulting from the sustained hyperglycemia and obesity in diabetic mice.

Development of a high-throughput method for real-time assessment of cellular metabolism in intact long skeletal muscle fibre bundles

KEY POINTS

We developed a method that allows for real-time assessment of cellular metabolism in isolated, intact long skeletal muscle fibre bundles from adult mice. This method can be used to study changes in mitochondrial function and fuel utilisation in live skeletal muscle fibre bundles. Our method enables flexibility in experimental design and high-throughput assessment of mitochondrial parameters in isolated skeletal muscle fibre bundles. Extensor digitorum longus (EDL) fibre bundles obtained from chronic high-fat diet fed mice had lower basal oxygen consumption under FCCP-induced maximal respiration, when compared to control chow-fed mice. EDL fibre bundles obtained from chronic high-fat diet fed mice had enhanced mitochondrial oxidation capacity under FCCP-induced maximal respiration, when compared to control chow-fed mice.

ABSTRACT

Metabolic dysfunction in skeletal muscle contributes to the aetiology and development of muscle diseases and metabolic diseases. As such, assessment of skeletal muscle cellular bioenergetics provides a powerful means to understand the role of skeletal muscle metabolism in disease and to identify possible therapeutic targets. Here, we developed a method that allows for the real-time assessment of cellular respiration in intact skeletal muscle fibre bundles obtained from the extensor digitorum longus (EDL) muscle of adult mice. Using this method, we assessed the contribution of ATP turnover and proton leak to basal mitochondrial oxygen consumption rate (OCR). Our data demonstrate that the mitochondria in EDL fibres are loosely coupled. Moreover, in the presence of carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), we show that palmitate exposure induced comparable peak OCR and higher total OCR in EDL fibre bundles when compared to pyruvate exposure, suggesting that fatty acids might be a more sustainable fuel source for skeletal muscle when mitochondria are driven to maximal respiration. Application of this method to EDL fibre bundles obtained from chronic high-fat diet fed mice revealed lower basal OCR and enhanced mitochondrial oxidation capacity in the presence of FCCP when compared to the chow-diet fed control mice. By using a 96-well microplate format, our method provides a flexible and efficient platform to investigate mitochondrial parameters of intact skeletal muscle fibres obtained from adult mice.

Head to Head Comparison of Short-Term Treatment with the NAD(+) Precursor Nicotinamide Mononucleotide (NMN) and 6 Weeks of Exercise in Obese Female Mice

Obesity is well known to be a major cause of several chronic metabolic diseases, which can be partially counteracted by exercise. This is due, in part, to an upregulation of mitochondrial activity through increased nicotinamide adenine dinucleotide (NAD⁺). Recent studies have shown that NAD⁺ levels can be increased by using the NAD⁺ precursor, nicotinamide mononucleotide (NMN) leading to the suggestion that NMN could be a useful intervention in diet related metabolic disorders. In this study we compared the metabolic, and especially mitochondrial-associated, effects of exercise and NMN in ameliorating the consequences of high-fat diet (HFD) induced obesity in mice. Sixty female 5 week old C57BL6/J mice were allocated across five groups: Chow sedentary: CS; Chow exercise: CEX; HFD sedentary: HS; HFD NMN: HNMN; HFD exercise: HEX (12/group). After 6 weeks of diet, exercise groups underwent treadmill exercise (15 m/min for 45 min), 6 days per week for 6 weeks. NMN or vehicle (500 mg/kg body weight) was injected (i.p.) daily for the last 17 days. No significant alteration in body weight was observed in response to exercise or NMN. The HFD significantly altered adiposity, glucose tolerance, plasma insulin, NADH levels and citrate synthase activity in muscle and liver. HEX and HNMN groups both showed significantly improved glucose tolerance compared to the HS group. NAD⁺ levels were increased significantly both in muscle and liver by NMN whereas exercise increased NAD⁺ only in muscle. Both NMN and exercise ameliorated the HFD-induced reduction in liver citrate synthase activity. However, exercise, but not NMN, ameliorated citrate synthase activity in muscle. Overall these data suggest that while exercise and NMN-supplementation can induce similar reversal of the glucose intolerance induced by obesity, they are associated with tissue-specific effects and differential alterations to mitochondrial function in muscle and liver.

Sesamin prevents decline in exercise capacity and impairment of skeletal muscle mitochondrial function in mice with high-fat diet-induced diabetes

New Findings

What is the central question of this study?

Our aim was to examine whether sesamin can prevent a decline in exercise capacity in high‐fat diet‐induced diabetic mice. Our hypothesis was that maintenance of mitochondrial function and attenuation of oxidative stress in the skeletal muscle would contribute to this result.

What is the main finding and its importance?

The new findings are that sesamin prevents the diabetes‐induced decrease in exercise capacity and impairment of mitochondrial function through the inhibition of NAD(P)H oxidase‐dependent oxidative stress in the skeletal muscle. Sesamin may be useful as a novel agent for the treatment of diabetes mellitus.

Abstract

We previously reported that exercise capacity and skeletal muscle mitochondrial function in diabetic mice were impaired, in association with the activation of NAD(P)H oxidase. It has been reported that sesamin inhibits NAD(P)H oxidase‐induced superoxide production. Therefore, we examined whether the antioxidant sesamin could prevent a decline in exercise capacity in mice with high‐fat diet (HFD)‐induced diabetes. C57BL/6J mice were fed a normal diet (ND) or HFD, then treated or not with sesamin (0.2%) to yield the following four groups: ND, ND+Sesamin, HFD and HFD+Sesamin (n = 10 each). After 8 weeks, body weight, fat weight, blood glucose, insulin, triglyceride, total cholesterol and fatty acid were significantly increased in HFD compared with ND mice. Sesamin prevented the increases in blood insulin and lipid levels in HFD‐fed mice, but did not affect the plasma glucose. Exercise capacity determined by treadmill tests was significantly reduced in HFD mice, but almost completely recovered in HFD+Sesamin mice. Citrate synthase activity was significantly decreased in the skeletal muscle of HFD mice, and these decreases were also inhibited by sesamin. Superoxide anion and NAD(P)H oxidase activity were significantly increased in HFD mice compared with the ND mice and were ameliorated by sesamin. Sesamin prevented the decline in exercise capacity in HFD‐induced diabetic mice via maintenance of mitochondrial function, fat oxidation and attenuation of oxidative stress in the skeletal muscle. Our data suggest that sesamin may be useful as a novel agent for the treatment of diabetes mellitus.

Skeletal Muscle Abnormalities in Heart Failure

Exercise capacity is lowered in patients with heart failure, which limits their daily activities and also reduces their quality of life. Furthermore, lowered exercise capacity has been well demonstrated to be closely related to the severity and prognosis of heart failure. Skeletal muscle abnormalities including abnormal energy metabolism, transition of myofibers from type I to type II, mitochondrial dysfunction, reduction in muscular strength, and muscle atrophy have been shown to play a central role in lowered exercise capacity. The skeletal muscle abnormalities can be classified into the following main types: 1) low endurance due to mitochondrial dysfunction; and 2) low muscle mass and muscle strength due to imbalance of protein synthesis and degradation. The molecular mechanisms of these skeletal muscle abnormalities have been studied mainly using animal models. The current review including our recent study will focus upon the skeletal muscle abnormalities in heart failure.

Curcumin ameliorates skeletal muscle atrophy in type 1 diabetic mice by inhibiting protein ubiquitination

NEW FINDINGS

What is the central question of this study? We sought to examine whether curcumin could ameliorate skeletal muscle atrophy in diabetic mice by inhibiting protein ubiquitination, inflammatory cytokines and oxidative stress. What is the main finding and its importance? We found that curcumin ameliorated skeletal muscle atrophy in streptozotocin-induced diabetic mice by inhibiting protein ubiquitination without affecting protein synthesis. This favourable effect of curcumin was possibly due to the inhibition of inflammatory cytokines and oxidative stress. Curcumin may be beneficial for the treatment of muscle atrophy in type 1 diabetes mellitus. Skeletal muscle atrophy develops in patients with diabetes mellitus (DM), especially in type 1 DM, which is associated with chronic inflammation. Curcumin, the active ingredient of turmeric, has various biological actions, including anti-inflammatory and antioxidant properties. We hypothesized that curcumin could ameliorate skeletal muscle atrophy in mice with streptozotocin-induced type 1 DM. C57BL/6 J mice were injected with streptozotocin (200 mg kg(-1) i.p.; DM group) or vehicle (control group). Each group of mice was randomly subdivided into two groups of 10 mice each and fed a diet with or without curcumin (1500 mg kg(-1) day(-1)) for 2 weeks. There were significant decreases in body weight, skeletal muscle weight and cellular cross-sectional area of the skeletal muscle in DM mice compared with control mice, and these changes were significantly attenuated in DM+Curcumin mice without affecting plasma glucose and insulin concentrations. Ubiquitination of protein was increased in skeletal muscle from DM mice and decreased in DM+Curcumin mice. Gene expressions of muscle-specific ubiquitin E3 ligase atrogin-1/MAFbx and MuRF1 were increased in DM and inhibited in DM+Curcumin mice. Moreover, nuclear factor-κB activation, concentrations of the inflammatory cytokines tumour necrosis factor-α and interleukin-1β and oxidative stress were increased in the skeletal muscle from DM mice and inhibited in DM+Curcumin mice. Curcumin ameliorated skeletal muscle atrophy in DM mice by inhibiting protein ubiquitination, inflammatory cytokines and oxidative stress. Curcumin may be beneficial for the treatment of muscle atrophy in type 1 DM.

Effects of exercise on brain functions in diabetic animal models

Human life span has dramatically increased over several decades, and the quality of life has been considered to be equally important. However, diabetes mellitus (DM) characterized by problems related to insulin secretion and recognition has become a serious health problem in recent years that threatens human health by causing decline in brain functions and finally leading to neurodegenerative diseases. Exercise is recognized as an effective therapy for DM without medication administration. Exercise studies using experimental animals are a suitable option to overcome this drawback, and animal studies have improved continuously according to the needs of the experimenters. Since brain health is the most significant factor in human life, it is very important to assess brain functions according to the different exercise conditions using experimental animal models. Generally, there are two types of DM; insulin-dependent type 1 DM and an insulin-independent type 2 DM (T2DM); however, the author will mostly discuss brain functions in T2DM animal models in this review. Additionally, many physiopathologic alterations are caused in the brain by DM such as increased adiposity, inflammation, hormonal dysregulation, uncontrolled hyperphagia, insulin and leptin resistance, and dysregulation of neurotransmitters and declined neurogenesis in the hippocampus and we describe how exercise corrects these alterations in animal models. The results of changes in the brain environment differ according to voluntary, involuntary running exercises and resistance exercise, and gender in the animal studies. These factors have been mentioned in this review, and this review will be a good reference for studying how exercise can be used with therapy for treating DM.

Epigenetics: Its Understanding Is Crucial to a Sustainable Healthcare System

Understanding the molecular impact of lifestyle factors has never been so important; a period in time where there are so many adults above retirement age has been previously unknown. As a species, our life expectancy is increasing yet the period of our lives where we enjoy good health is not expanding proportionately. Over the next 50 years we will need to almost double the percentage of GDP spent on health care, largely due to the increasing incidence of obesity related chronic diseases. A greater understanding and implementation of an integrated approach to health is required. Research exploring the impact of nutritional and exercise intervention on the epigenetically flexible genome is up front in terms of addressing healthy aging. Alongside this, we need a greater understanding of the interaction with our immune and nervous systems in preserving and maintaining health and cognition.

Physical rehabilitation improves muscle function following volumetric muscle loss injury

Background

Given the clinical practice of prescribing physical rehabilitation for the treatment of VML injuries, the present study examined the functional and histomorphological adaptations in the volumetric muscle loss (VML) injured muscle to physical rehabilitation.

Methods

Tibialis anterior muscle VML injury was created in Lewis rats (n = 32), and were randomly assigned to either sedentary (SED) or physical rehabilitation (RUN) group. After 1 week, RUN rats were given unlimited access to voluntary running wheels either 1 or 7 weeks (2 or 8 weeks post-injury). At 2 weeks post-injury, TA muscles were harvested for molecular analyses. At 8 weeks post-injury, the rats underwent in vivo function testing. The explanted tissue was analyzed using histological and immunofluorescence procedures.

Results

The primary findings of the study are that physical rehabilitation in the form of voluntary wheel running promotes ~ 17% improvement in maximal isometric torque, and a ~ 13% increase in weight of the injured muscle, but it did so without significant morphological adaptations (e.g., no hypertrophy and hyperplasia). Wheel running up-regulated metabolic genes (SIRT-1, PGC-1α) only in the uninjured muscles, and a greater deposition of fibrous tissue in the defect area of the injured muscle preceded by an up-regulation of pro-fibrotic genes (Collagen I, TGF-β1). Therefore, it is plausible that the wheel running related functional improvements were due to improved force transmission and not muscle regeneration.

Conclusions

This is the first study to demonstrate improvement in functional performance of non-repaired VML injured muscle with physical rehabilitation in the form of voluntary wheel running. This study provides information for the first time on the basic changes in the VML injured muscle with physical rehabilitation, which may aid in the development of appropriate physical rehabilitation regimen(s).

Growing healthy muscles to optimise metabolic health into adult life

The importance of skeletal muscle for metabolic health and obesity prevention is gradually gaining recognition. As a result, interventions are being developed to increase or maintain muscle mass and metabolic function in adult and elderly populations. These interventions include exercise, hormonal and nutritional therapies. Nonetheless, growing evidence suggests that maternal malnutrition and obesity during pregnancy and lactation impede skeletal muscle development and growth in the offspring, with long-term functional consequences lasting into adult life. Here we review the role of skeletal muscle in health and obesity, providing an insight into how this tissue develops and discuss evidence that maternal obesity affects its development, growth and function into adult life. Such evidence warrants the need to develop early life interventions to optimise skeletal muscle development and growth in the offspring and thereby maximise metabolic health into adult life.

Pioglitazone ameliorates the lowered exercise capacity and impaired mitochondrial function of the skeletal muscle in type 2 diabetic mice

We have reported that exercise capacity is reduced in high fat diet (HFD)-induced diabetic mice, and that this reduction is associated with impaired mitochondrial function in skeletal muscle (SKM). However, it remains to be clarified whether the treatment of diabetes ameliorates the reduced exercise capacity. Therefore, we examined whether an insulin-sensitizing drug, pioglitazone, could improve exercise capacity in HFD mice. C57BL/6J mice were fed a normal diet (ND) or HFD, then treated with or without pioglitazone (3 mg/kg/day) to yield the following 4 groups: ND+vehicle, ND+pioglitazone, HFD+vehicle, and HFD+pioglitazone (n=10 each). After 8 weeks, body weight, plasma glucose, and insulin in the HFD+vehicle were significantly increased compared to the ND+vehicle group. Pioglitazone normalized the insulin levels in HFD-fed mice, but did not affect the body weight or plasma glucose. Exercise capacity determined by treadmill tests was significantly reduced in the HFD+vehicle, and this reduction was almost completely ameliorated in HFD+pioglitazone mice. ADP-dependent mitochondrial respiration, complex I and III activities, and citrate synthase activity were significantly decreased in the SKM of the HFD+vehicle animals, and these decreases were also attenuated by pioglitazone. NAD(P)H oxidase activity was significantly increased in the HFD+vehicle compared with the ND+vehicle, and this increase was ameliorated in HFD+pioglitazone mice. Pioglitazone improved the exercise capacity in diabetic mice, which was due to the improvement in mitochondrial function and attenuation of oxidative stress in the SKM. Our data suggest that pioglitazone may be useful as an agent for the treatment of diabetes mellitus.