Combined exercise and calorie restriction therapies restore contractile and mitochondrial functions in skeletal muscle of obese–insulin resistant rats

Combined effects of natural products and exercise on apoptosis pathways in obesity-related skeletal muscle dysfunction

Obesity and related metabolic disorders are closely linked to increased apoptosis in skeletal muscle, leading to muscle degeneration, insulin resistance, and the progression of diseases such as type 2 diabetes and sarcopenia. This review explores the combined effects of natural products, including resveratrol, curcumin, and quercetin, and physical exercise on modulating apoptosis pathways in skeletal muscle. Both natural products and regular physical activity independently reduce oxidative stress and improve mitochondrial function, thereby regulating the balance between pro-apoptotic and anti-apoptotic signals. When combined, these interventions amplify their protective effects on muscle health, promoting mitochondrial biogenesis, reducing apoptosis, and enhancing muscle regeneration. This review also discusses the molecular mechanisms by which these strategies influence apoptosis, with a focus on the Bcl-2 pathway, and explores the clinical implications for the prevention and treatment of obesity-related diseases. The synergistic benefits of combining exercise with natural product supplementation offer a promising therapeutic approach for managing metabolic disorders, preserving muscle function, and improving overall metabolic health.

Potential regulatory role of PGC-1α within the skeletal muscle during metabolic adaptations in response to high-fat diet feeding in animal models

High-fat diet (HFD) feeding in rodents has become an essential tool to critically analyze and study the pathological effects of obesity, including mitochondrial dysfunction and insulin resistance. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) regulates cellular energy metabolism to influence insulin sensitivity, beyond its active role in stimulating mitochondrial biogenesis to facilitate skeletal muscle adaptations in response to HFD feeding. Here, some of the major electronic databases like PubMed, Embase, and Web of Science were accessed to update and critically discuss information on the potential role of PGC-1α during metabolic adaptations within the skeletal muscle in response to HFD feeding in rodents. In fact, available evidence suggests that partial exposure to HFD feeding (potentially during the early stages of disease development) is associated with impaired metabolic adaptations within the skeletal muscle, including mitochondrial dysfunction and reduced insulin sensitivity. In terms of implicated molecular mechanisms, these negative effects are partially associated with reduced activity of PGC-1α, together with the phosphorylation of protein kinase B and altered expression of genes involving nuclear respiratory factor 1 and mitochondrial transcription factor A within the skeletal muscle. Notably, metabolic abnormalities observed with chronic exposure to HFD (likely during the late stages of disease development) may potentially occur independently of PGC-1α regulation within the muscle of rodents. Summarized evidence suggests the causal relationship between PGC-1α regulation and effective modulations of mitochondrial biogenesis and metabolic flexibility during the different stages of disease development. It further indicates that prominent interventions like caloric restriction and physical exercise may affect PGC-1α regulation during effective modulation of metabolic processes.

Concurrent Aerobic and Strength Training with Caloric Restriction Reduces Insulin Resistance in Obese Premenopausal Women: A Randomized Controlled Trial

Background and Objectives: Obese premenopausal women are at high risk of developing insulin resistance (IR). Concurrent aerobic and strength training (CAST) has been shown to provide remarkable advantages, yet its effects, along with caloric restriction in such a high-risk population, are not yet established. This study aimed to investigate the impact of concurrent aerobic and strength training with caloric restriction (CAST-CR) on IR in obese premenopausal women. Materials and Methods: Forty-two obese premenopausal women with reported IR, aged 40-50 years, were randomly allocated to either the (CAST-CR) intervention group, who underwent CAST with caloric restriction, or the (AT-CR) control group, who received aerobic training in addition to caloric restriction. Both groups completed 12 weeks of controlled training with equivalent training time. Aerobic training began at 60% and gradually progressed to achieve 75% of the maximum heart rate, while strength training was executed at 50% to 70% of the one-repetition maximum (1RM). Anthropometric measures, abdominal adiposity, metabolic parameters, and homeostasis model assessment-estimated insulin resistance (HOMA-IR) were evaluated prior to and following the intervention. Results: Both groups experienced a substantial enhancement in the selected parameters compared to the baseline (p < 0.001), with higher improvement within the CAST-CR group. The changes in HOMA-IR were -1.24 (95%CI, -1.37 to -1.12) in the CAST-CR group vs. -1.07 (95%CI, -1.19 to -0.94) in the AT-CR group. Conclusions: While AT-CR improved insulin sensitivity in premenopausal women who were obese and hyperinsulinemic, CAST with calorie restriction improved insulin sensitivity more significantly, suggesting it as a preferable alternative.

Diet Restriction Impact on High-Fat-Diet-Induced Obesity by Regulating Mitochondrial Cardiolipin Biosynthesis and Remodeling

Diet restriction (DR) ameliorates obesity by regulating mitochondrial function. Cardiolipin (CL), a mitochondrial phospholipid, is closely associated with mitochondrial function. This study aimed to evaluate the anti-obesity effects of graded levels of DR based on mitochondrial CL levels in the liver. Obese mice were treated with 0%, 20%, 40%, and 60% reductions in the normal diet compared to normal animals (0 DR, 20 DR, 40 DR, and 60 DR groups, respectively). Biochemical and histopathological analyses were performed to evaluate the ameliorative effects of DR on obese mice. The altered profile of mitochondrial CL in the liver was explored using a targeted metabolomics strategy by ultra-high-pressure liquid chromatography MS/MS coupled with quadrupole time-of-flight mass spectrometry. Finally, gene expression associated with CL biosynthesis and remodeling was quantified. Tissue histopathology and biochemical index evaluations revealed significant improvements in the liver after DR, except for the 60 DR group. The variation in mitochondrial CL distribution and DR levels showed an inverted U-shape, and the CL content in the 40 DR group was the most upregulated. This result is consistent with the results of the target metabolomic analysis, which showed that 40 DR presented more variation. Furthermore, DR led to increased gene expression associated with CL biosynthesis and remodeling. This study provides new insights into the mitochondrial mechanisms underlying DR intervention in obesity.

HIIT Ameliorates Inflammation and Lipid Metabolism by Regulating Macrophage Polarization and Mitochondrial Dynamics in the Liver of Type 2 Diabetes Mellitus Mice

High-intensity interval training (HIIT), a new type of exercise, can effectively prevent the progression of metabolic diseases. The aim of this study was to investigate the effects of HIIT on liver inflammation and metabolic disorders in type 2 diabetes mellitus (T2DM) mice induced by a high-fat diet (HFD) combined with streptozotocin (STZ) and to explore the possible mechanisms of macrophage polarization and mitochondrial dynamics. Our results showed that HIIT can increase fatty acid oxidation-related gene (PPARα, CPT1α, and ACOX1) mRNA levels and decrease adipogenesis-related gene (PPARγ) mRNA levels to improve liver metabolism in T2DM mice. The improvement of lipid metabolism disorder may occur through increasing liver mitochondrial biosynthesis-related genes (PGC-1α and TFAM) and restoring mitochondrial dynamics-related gene (MFN2 and DRP1) mRNA levels. HIIT can also reduce the mRNA levels of liver inflammatory factors (TNF-α, IL-6, and MCP-1) in T2DM mice. The reduction in liver inflammation may occur through reducing the expression of total macrophage marker (F4/80) and M1 macrophage marker (CD86) mRNA and protein and increasing the expression of M2 macrophage marker (CD163, CD206, and Arg1) mRNA and protein in the liver. HIIT can also increase the expression of insulin signaling pathway (IRS1, PI3K, and AKT) mRNA and protein in the liver of T2DM mice, which may be related to the improvements in liver inflammation and lipid metabolism. In conclusion, these results suggested that 8 weeks of HIIT can improve inflammation and lipid metabolism disorders in the liver of type 2 diabetes mellitus mice, macrophage M1/M2 polarization, and mitochondrial dynamics may be involved in this process.

Combined caloric restriction and exercise provides greater metabolic and neurocognitive benefits than either as a monotherapy in obesity with or without estrogen deprivation

Neurodegeneration, as indicated by brain dysfunction and cognitive decline, is one of the complications associated with obesity and estrogen deprivation. Calorie restriction and exercise regimes improved brain function in neurodegenerative diseases. However, the comparative effects of a combination of calorie restriction with exercise, calorie restriction, and an exercise regime alone on brain/cognitive function in obesity with or without estrogen deprivation have not been investigated. Sixty female rats were fed a normal diet (ND) or a high-fat diet (HFD) for 27 weeks. At week 13, the ND-fed rats underwent a sham operation with sedentary lifestyle, HFD-fed rats were divided into two groups: each having either a sham operation (HFS) or ovariectomy (HFO). At week 20, HFD-fed rats in each group were divided into four subgroups undergoing either a sedentary lifestyle, calorie restriction, exercise regime or a combination of calorie restriction and exercise for 7 weeks. Insulin resistance, cognitive decline and hippocampal pathologies were found in both HFS and HFO rats. HFO rats had higher levels of insulin resistance and hippocampal reactive oxygen species levels than HFS rats. Calorie restriction decreased metabolic disturbance and hippocampal oxidative stress but failed to attenuate cognitive decline in HFS and HFO rats. Exercise attenuated metabolic/hippocampal dysfunctions, resulting in improved cognition only in HFS rats. Combined therapies restored brain function, and cognitive function in HFS and HFO rats. Therefore, a combination of calorie restriction with exercise is probably the greatest lifestyle modification to diminish the brain pathologies and cognitive decline in obesity with or without estrogen deprivation.

Aging and short-term calorie restriction differently affect the cardiac and skeletal muscle expression of genes regulating energy substrate utilization in male rats

Aging affects the energy metabolism differently in the cardiac and skeletal muscles. The study aim was to assess the effects of short-term calorie restriction (SCR) and refeeding on the expression of genes involved in the control of cardiac and skeletal muscle energy metabolism in old vs. young male rats. Young (4 mo) and old (24 mo) rats were subjected to 60% SCR for 30 days, and refed ad libitum for 2 or 4 days. In the cardiac (CM) and skeletal muscles (SM) we compared the gene expression (qPCR) of carnitine palmitoyltransferase-I (Cpt-I), peroxisome proliferator-activated receptor beta/delta (Ppar-β/δ), glucose transporter 4 (Glut4), peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α), and sirtuin 3 (Sirt3). In CM, aging increased Cpt-I expression but did not affect the other genes. In SM, Cpt-I, Glut4, Pgc-1α, and Sirt3 mRNA levels were lower in old than young rats. In CM of only young rats SCR increased Cpt-I expression which remained elevated after refeeding. Upon SCR, the expression of Ppar-β/δ, Glut4, Pgc-1α, and Sirt3 in CM increased in young but not old rats, and refeeding re-established control levels. In SM of young rats SCR increased Ppar-β/δ and Pgc-1α, and decreased Sirt3 expression, whereas refeeding generally decreased these mRNA levels. In SM of old rats SCR decreased only Pgc-1α expression. The adaptive response to SCR and subsequent refeeding is muscle tissue-specific and differs in young and old male rats. SCR appears to increase the efficiency of glucose and fatty acid utilization in the cardiac muscle of young, but not old male rats.

COVID-19: A Mitochondrial Perspective

Coronavirus disease 2019 (COVID-19) is the worst public health crisis of the century. Although we have made tremendous progress in understanding the pathogenesis of this disease, a lot more remains to be learned. Mitochondria appear to be important in COVID-19 pathogenesis because of its role in innate antiviral immunity, as well as inflammation. This article examines pathogenesis of COVID-19 from a mitochondrial perspective and tries to answer some perplexing questions such as why the prognosis is so poor in those with obesity, metabolic syndrome, or type 2 diabetes. Although effective vaccines and antiviral drugs will be the ultimate solution to this crisis, a better understanding of disease mechanisms will open novel avenues for treatment and prevention.

Current perspectives on obesity and skeletal muscle contractile function in older adults

Obesity has become one of the most pressing public health issues of the 21st century and currently affects a substantial proportion of the older adult population. Although the cardiometabolic complications are well documented, research from the past 20 years has drawn attention to the detrimental effects of obesity on physical performance in older adults. Obesity-related declines in physical performance are due, in part, to compromised muscle strength and power. Recent evidence suggests there are a number of mechanisms potentially underlying reduced whole muscle function, including alterations in myofilament protein function and cellular contractile properties, and these may be related to morphological adaptations, such as shifts in fiber type composition and increased intramyocellular lipid content within skeletal muscle. To date, even less research has focused on how exercise and weight loss interventions for obese older adults affect these mechanisms. In light of this work, we provide an update on the current knowledge related to obesity and skeletal muscle contractile function and highlight a number of questions to address potential etiologic mechanisms as well as intervention strategies, which may help advance our understanding of how physical performance can be improved among obese older adults.

A proprotein convertase subtilisin/kexin type 9 inhibitor provides comparable efficacy with lower detriment than statins on mitochondria of oxidative muscle of obese estrogen-deprived rats

OBJECTIVES

The aim of the study was to compare the effects of atorvastatin, a proprotein convertase subtilisin/kexin type 9 inhibitor (PCSK9i), and 17β-estradiol on oxidative muscle mitochondria in a model of menopause with obesity.

METHODS

Female Wistar rats consumed either a standard diet (n = 12) or a high-fat/calorie diet (HFCD: n = 60). At week 13, standard diet-fed rats underwent a sham operation, whereas HFCD-fed rats underwent either a sham operation (n = 12) or an ovariectomy (n = 48). At week 19, all sham-operated rats received vehicle, and ovariectomized HFCD-fed rats received either vehicle, 40 mg/kg/d of atorvastatin, 4 mg/kg/d of PCSK9i (SBC-115076), or 50 μg/kg/d of 17β-estradiol for 3 weeks (n = 12/group). Metabolic parameters and soleus muscle physiology were investigated at the end of week 21.

RESULTS

Sham-operated and ovariectomized HFCD-fed rats developed obesity, hyperlipidemia, and insulin resistance, also showing increased oxidative phosphorylation (OXPHOS) proteins, ratio of p-Drp1-to-total Drp1 protein, malondialdehyde level, mitochondrial reactive oxygen species, and mitochondrial membrane depolarization in soleus muscle. All drugs equally decreased insulin resistance, OXPHOS proteins, ratio of p-Drp1-to-total Drp1 protein, and malondialdehyde level in soleus muscle. Only atorvastatin and PCSK9i attenuated hypertriglyceridemia, whereas 17β-estradiol had greater efficacy in preventing weight gain than the other two drugs. In addition, 17β-estradiol decreased mitochondrial reactive oxygen species and mitochondrial membrane depolarization. Atorvastatin increased ratio of cleaved caspase 3,8-to-procaspase 3,8, and cytochrome C.

CONCLUSIONS

17β-Estradiol exhibits the greatest efficacy on the attenuation of obesity with the least harmful effect on skeletal muscle in a model of menopause with obesity, yet its effect on the treatment of hyperlipidemia is inferior to those of standard lipid-lowering agents.

Decreased Mitochondrial Dynamics Is Associated with Insulin Resistance, Metabolic Rate, and Fitness in African Americans

CONTEXT

African American women (AAW) have a higher incidence of insulin resistance and are at a greater risk for the development of obesity and type 2 diabetes than Caucasian women (CW). Although several factors have been proposed to mediate these racial disparities, the mechanisms remain poorly defined. We previously demonstrated that sedentary lean AAW have lower peripheral insulin sensitivity, reduced maximal aerobic fitness (VO2max), and lower resting metabolic rate (RMR) than CW. We have also demonstrated that skeletal muscle mitochondrial respiration is lower in AAW and appears to play a role in these racial differences.

OBJECTIVE

The goal of this study was to assess mitochondrial pathways and dynamics to examine the potential mechanisms of lower insulin sensitivity, RMR, VO2max, and mitochondrial capacity in AAW.

DESIGN

To achieve this goal, we assessed several mitochondrial pathways in skeletal muscle using gene array technology and semiquantitative protein analysis.

RESULTS

We report alterations in mitochondrial pathways associated with inner membrane small molecule transport genes, fusion-fission, and autophagy in lean AAW. These differences were associated with lower insulin sensitivity, RMR, and VO2max.

CONCLUSIONS

Together these data suggest that the metabolic racial disparity of insulin resistance, RMR, VO2max, and mitochondrial capacity may be mediated by perturbations in mitochondrial pathways associated with membrane transport, fission-fusion, and autophagy. The mechanisms contributing to these differences remain unknown.

The comparative effects of high dose atorvastatin and proprotein convertase subtilisin/kexin type 9 inhibitor on the mitochondria of oxidative muscle fibers in obese-insulin resistant female rats

The present study aimed to compare the effects of high dose atorvastatin and a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor on the mitochondrial function in oxidative muscle fibers in obese female rats. Female Wistar rats were fed with either a normal diet (ND: n = 12) or a high-fat diet (HFD: n = 36) for a total of 15 weeks. At week 13, ND-fed rats received a vehicle, and HFD-fed rats were divided to three groups to receive either a vehicle, 40 mg/kg/day of atorvastatin, or 4 mg/kg/day of PCSK9 inhibitor (SBC-115076) for 3 weeks. Soleus muscles were investigated to assess mitochondrial ROS, membrane potential, swelling, mitochondrial-related protein expression, and level of malondialdehyde (MDA). The results showed that HFD-fed rats with vehicle developed obese-insulin resistance and dyslipidemia. Both atorvastatin and PCSK9 inhibitor reduced obesity and dyslipidemia, as well as improved insulin sensitivity in HFD-fed rats. However, the efficacy of PCSK9 inhibitor to increase weight loss and reduce dyslipidemia in HFD-fed rats was greater than those of atorvastatin. An increase in MDA level, ratio of p-Drp1^ser616/total Drp1 protein, CPT1 protein, mitochondrial ROS, and membrane depolarization in the soleus muscle were observed in HFD-fed rats with vehicle. PCSK9 inhibitor enabled the restoration of all these parameters to normal levels. However, atorvastatin facilitated restoration of some parameters, including MDA level, p-Drp1^ser616/total Drp1 ratio, and CPT1 protein expression. These findings suggest that PCSK9 inhibitor is superior to atorvastatin in instigating weight loss, cholesterol reduction, and attenuation of mitochondrial oxidative stress in oxidative muscle fibers of obese female rats.

Endurance Training Counteracts the High-Fat Diet-Induced Profiling Changes of ω-3 Polyunsaturated Fatty Acids in Skeletal Muscle of Middle-Aged Rats

Purpose

To investigate the effects of endurance training on the content of ω-3 polyunsaturated fatty acids (PUFAs) and their distribution among lipid classes in skeletal muscle in middle aged, high-fat diet fed rats.

Method

Thirty 10-month old male Sprague Dawley (SD) rats were assigned to four groups. Two groups of rats remained sedentary and were fed chow diet (C group), or high-fat diet (H group), respectively. The other two groups of rats were subjected to endurance training while maintaining their chow diet (EC group), or high-fat diet (EH group). After 16 weeks endurance training and/or diet intervention, the content of ω-3 PUFAs and ω-3 PUFA-containing lipids in rat soleus muscle were analyzed by lipidomics.

Results

Rats fed a high-fat diet exhibited decreased overall amount of ω-3 PUFAs in soleus muscle, while endurance training preserved the total amount of ω-3 PUFAs. Both the endurance training and high-fat diet alone changed the profiles of ω-3 PUFAs in different lipid classes. Specifically, the amount of triacylglycerol (TG), lysophosphatidylcholine (LPC), phosphatidylcholine (PC), and phosphatidylglycerol (PG) containing ω-3 PUFAs in soleus muscle was increased by endurance training, but the amount of lysophosphatidylenthanol (LPE), lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS), cardiolipin (CL), phosphatidic acid (PA), and phosphatidylinositol (PI) was decreased. The high-fat diet induced a decrease of ω-3 PUFAs in TG, LPE, LPS, CL, platelet activating factor (PAF), PC, phosphatidylethanolamine (PE), and phosphatidylserine (PS), and an increase in LPC, LPI, PA, and PG. In addition, the effects of the endurance training on ω-3 PUFAs in skeletal muscle was also evident in high-fat diets fed rats, which counteracts the profiling changes caused by high-fat diet feeding.

Conclusion

The beneficial effects of endurance training on skeletal muscle may be achieved to some extent through recovering the content of ω-3 PUFAs that has been decreased by high-fat diet feeding.