Effects of ageing and endurance exercise training on alpha-actinin isoforms in rat plantaris muscle

Effects of preconditioning with heat stress on acute exercise-induced intracellular signaling in male rat gastrocnemius muscle

Heat stress (HS) induces Akt/mTOR phosphorylation and FoxO3a signaling; however, whether a prior increase in heat shock protein 72 (HSP72) expression affects intracellular signaling following eccentric exercise remains unclear. We analyzed the effects of HS pretreatment on intramuscular signaling in response to acute exercise in 10-week-old male Wistar rats (n = 24). One leg of each rat was exposed to HS and the other served as an internal control (CT). Post-HS, rats were either rested or subjected to downhill treadmill running. Intramuscular signaling responses in the red and white regions of the gastrocnemius muscle were analyzed before, immediately after, or 1 h after exercise (n = 8/group). HS significantly increased HSP72 levels in both deep red and superficial white regions. Although HS did not affect exercise-induced mTOR signaling (S6K1/ERK) responses in the red region, mTOR phosphorylation in the white region was significantly higher in CT legs than in HS legs after exercise. Thr308 phosphorylation of Akt showed region-specific alteration with a decrease in the red region and an increase in the white region immediately after downhill running. Overall, a prior increase in HSP72 expression elicits fiber type-specific changes in exercise-induced Akt and mTOR phosphorylation in rat gastrocnemius muscle.

Research trends and hotspots of exercise for people with sarcopenic: A bibliometric analysis

This study aimed to analyze the trends and themes in exercise and sarcopenia research using a bibliometric approach. The Web of Science citation database was used to identify papers published on exercise and sarcopenia. The retrieved data on institutions, journals, countries, authors, journal distribution, and keywords were analyzed scientometric ally using CiteSpace and VOSviewer. 2895 papers were included according to our specified inclusion criteria eventually. The data showed an upward trend in the number of published articles on exercise and sarcopenia. The countries with the highest number of publications were the United States, Japan, and England; research institutions were mainly composed of universities in Europe and the United States, and high-producing authors formed major collaborative teams, but cross-geographical and cross-institutional collaboration was not apparent; research was closely focused on 3 aspects: resistance exercise, resistance combined with other forms of exercise, and exercise combined with nutritional supplementation, of which resistance exercise was a particular focus; and recently, the research hotspots were mainly the effects of exercise on grip strength. The most cited articles were consensus guidelines published by the working group on sarcopenia in the elderly from different continents. The prevention and rehabilitation of sarcopenia in the elderly are gaining attention. Current primary exercise therapies for sarcopenia and exercise combined with nutritional supplementation have significant advantages and the potential to delay muscle decay. This suggests a promising area for future research that could benefit from further advances.

Musculoskeletal Biomarkers Response to Exercise in Older Adults

Exercise is an essential component of any good health style, being particularly important for older adults to counteract the effects of aging, including sarcopenia and osteoporosis, which can result in lower fall probability. Exercise programs for older adults are especially designed for that population. A rigorous evaluation of those programs is necessary to assure most benefit is achieved. Serum biomarkers of proteins intrinsic to musculoskeletal homeostasis could contribute objectively to the assessment of the benefits of exercise. In this work, in addition to the usual physical fitness and balance tests, ELISA assays quantified the serum levels of six proteins and one polysaccharide important for the homeostasis of muscle (troponin T and alpha-actinin), tendon/ligament (tenomodulin), cartilage (cartilage oligomeric matrix protein and hyaluronan) and bone (osteocalcin and sclerostin), before and after 8 weeks of an exercise program tailored to older adults, Stay Strong Stay Healthy, offered at a Community Center and at an Independent Senior Living facility. Statistical significance was determined by non-parametric tests (Wilcoxon Signed Ranks and Mann-Whitney U). Physical fitness and balance improved as expected along with a significant decrease in sclerostin, pointing to less inhibition of bone deposition. However, when considering each type of dwelling separately, older adults always saw a significant decrease of the isoform of troponin T associated with fast-twitch muscles, suggesting that daily levels of physical activity may also have a role in the benefit of older adults from exercise.

Aerobic exercise prevents apoptosis in skeletal muscles of high-fat-fed ovariectomized rats

[Purpose]

Aging and obesity are associated with skeletal muscle atrophy-related signaling pathways, including apoptosis. Many studies have shown that menopause is associated with an increased risk of skeletal muscle atrophy. There is an increasing need to develop strategies that will improve the risk of skeletal muscle atrophy through exercise interventions. However, the effect of exercise on estrogen deficiency-induced apoptosis in skeletal muscles is poorly understood. Therefore, we examined the effects of low-intensity exercise on ovariectomy (OVX)-induced apoptosis of the soleus and plantaris muscles.

[Methods]

The ovaries of all female Sprague-Dawley rats aged 8 weeks, were surgically removed to induce postmenopausal status. The rats were randomly divided into three treatment groups: (1) NSV (normal-diet-sedentary-OVX); (2) HSV (high-fat-diet-sedentary-OVX); and (3) HEV (high-fat-diet-exercise-OVX). The exercise groups were regularly running for 30-40 min/day at 15-18 m/minute, five times/week, for eight weeks.

[Results]

The mRNA levels of Bax significantly decreased in the exercised soleus muscle, and caspase-3 decreased in the plantaris. The skeletal muscle TUNEL-positive apoptotic cells in the high-fat-diet-sedentary OVX rats improved in the treadmill exercise group. Additionally, nuclear caspase-3 levels decreased in the treadmill exercise group compared to those in both sedentary groups. These results suggest that low-intensity treadmill exercise prevents skeletal muscle apoptosis in HFD-fed OVX rats.

[Conclusion]

Induction of HFD in estrogen-deficient mice increased apoptosis in skeletal muscle, which could also be alleviated by low-intensity aerobic exercise. These results may indicate a crucial therapeutic effect of treadmill exercise in preventing skeletal muscle apoptosis in menopausal or post-menopausal women.

Masticatory Functional Load Increases the mRNA Expression Levels of ACTN2 and ACTN3 and the Protein Expression of α-Actinin-2 in Rat Masseter Muscle

Objectives

α-actinins play structural and regulatory roles in cytoskeletal organization. They form a lattice structure that secures actin in thin filaments, which generate and transmit muscle contractile forces. The morphological and biochemical characteristics of rat masseter muscles are known to change reactions to masticatory functional loads, but their effect on α-actinins remains unknown. This study aimed to determine the response of α-actinins to masticatory functional loads.

Materials and Methods

Twenty-four male Wistar rats aged 3 weeks were divided randomly into 3 groups of liquid diet (LD), soft diet, and hard diet (HD). The rats were then sacrificed at the end of 8 weeks. The middle part of superficial masseter muscles was examined to investigate the masticatory effect of functional load on the mRNA expression levels of ACTN2 and ACTN3 and the protein expression levels of α-actinin-2 and α-actinin-3.

Results

The mRNA expression levels of ACTN2 and ACTN3 and the protein expression levels of α-actinin-2 of the HD group were significantly higher than those of the LD group, which served as the control group.

Conclusion

Masticatory functional load organizes the mRNA expression levels of ACTN2 and ACTN3 and the protein expression levels of α-actinin-2 in rat masseter muscles through stimuli during muscle physiological adaptation.

Age-related changes in histone modification in rat gastrocnemius muscle

Changes in histone acetylation and methylation status with aging affect gene expression and phenotype in several tissues; however, age-related changes in histone modification in the skeletal muscle have not been elucidated yet. This study investigated age-related global changes in histone modification in rat gastrocnemius muscle. Male Wistar rats (n = 28) were assigned to one of four age groups (n = 7 per group) corresponding to different life stages: 3 months old (3-mo; young), 6 months old (adult), 12 months old (12-mo; middle-aged), and 24 months old (24-mo; old). The gastrocnemius muscle was removed and global histone modification (acetylation and tri-methylation) at K9 and K27 was evaluated by western blotting. Relative muscle mass decreased in the 12- and 24-mo rats accompanied with reduction in type IIb myosin heavy chain isoforms and Myh4 (MHC IIB) mRNA expression. Histone H3 acetylation decreased in an age-dependent manner, with lower levels in 12- and 24-mo groups than in the 3-mo group. K9 and K27 acetylation decreased with age. Although there was no significant change in K27 tri-methylation, K9 tri-methylation showed an age-dependent decline. Histone modification status (acetylation at K9 and K27 and tri-methylation at K9) was positively associated with relative gastrocnemius muscle weight, the percentage of type IIb myosin heavy chain isoform, myosin heavy chain type IIb protein expression, and the level of Myh4 mRNA. Thus, global histone H3 methylation and acetylation decrease with age, and the latter might be associated with age-related muscle atrophy of rat gastrocnemius muscle.

Schisandra chinensis extract ameliorates age-related muscle wasting and bone loss in ovariectomized rats

Exercise and healthy diet consumption support healthy aging. Schisandra chinensis (Turcz.) also known as "Baill." has anti-inflammatory and antioxidant properties. However, the role of S. chinensis as an antiaging compound has yet to be demonstrated. This study elucidated the antiaging effect of S. chinensis ethanol-hexane extract (C1) and the effect of C1 treatment on muscle and bone following physical exercise in ovariectomized (OVX) rats. RAW 264.7, human diploid fibroblasts (HDFs), C2C12 myoblasts, bone marrow macrophages, and MC3T3-E1 cells were used for in vitro, and muscle and bone of OVX rats were used for in vivo study to demonstrate the effect of C1. The C1 significantly inhibited the expression of inflammatory molecules, β-galactosidase activity, and improved antioxidant activity via down-regulation of reactive oxygen species in RAW 264.7 and aged HDF cells. The C1 with exercise improved muscle regeneration in skeletal muscle of OVX rats by promoting mitochondrial biogenesis and autophagy. C1 induced osteoblast differentiation, and C1 + exercise modulated the bone formation and bone resorption in OVX rats. C1 exhibited anti-inflammatory, antioxidant, myogenic, and osteogenic effects. C1 with exercise improved age-related muscle wasting and bone loss. Therefore, S. chinensis may be a potential prevent agent for age-related diseases such as sarcopenia and osteoporosis.

Low-intensity aerobic exercise training: inhibition of skeletal muscle atrophy in high-fat-diet-induced ovariectomized rats

PURPOSE

Postmenopausal women are highly susceptible to diseases, such as obesity, type 2 diabetes, osteoporosis, or skeletal muscle atrophy and many people recognize the need for regular physical activity. Aerobic exercise training is known to improve the oxidative capacity and insulin sensitivity of skeletal muscles. This study aimed to investigate the role of low-intensity aerobic exercise training on skeletal muscle protein degradation or synthesis in the plantaris muscles of high-fat-fed ovariectomized rats.

METHODS

Ovariectomized female rats were divided into two groups: a high-fat diet-sedentary group (HFD), and a high-fat diet-aerobic exercise group (HFD+EX). The exercise group exercised aerobically on a treadmill 5 days/week for 8 weeks. The rats progressively ran 30 min/day at 15 m/min, up to 40 min/day at 18 m/min, 0% slope, in the last 4 weeks.

RESULTS

Although aerobic exercise led to significantly increased AMP-activated protein kinase (AMPK) phosphorylation at Thr172, phosphorylation of the mammalian target of rapamycin (mTOR) substrate Thr389 S6K1 level did not decrease. Additionally, even though Akt activity did not increase at Ser473, the atrogin-1 level significantly decreased in the exercise group compared to the non-exercise group. Immunohistochemical staining revealed that high-fat-induced TSC2 protein expression was eliminated in response to aerobic exercise.

CONCLUSION

These results suggest that aerobic exercise can inhibit skeletal muscle protein degradation, but it cannot increase protein synthesis in the plantaris muscle of high-fat-fed ovariectomized rats. Our findings have implications in understanding skeletal muscle mass maintenance with low intensity aerobic exercise in post-menopausal women.

The effects of downhill and uphill exercise training on osteogenesis-related factors in ovariectomy-induced bone loss

PURPOSE

Recent evidence suggests that regular exercise training plays a decisive role in maintaining homeostasis and promoting muscle and skeletal formation. However, the effect of downhill exercise training on osteogenesis-related factors is not well understood.

METHODS

Thus, we investigated the effect of uphill and downhill training on ovariectomy (OVX)-induced bone loss. After ovary removal, the exercise method performed included uphill (16 m/min, +15°) and downhill training (16 m/min, -15°) for 60 min/day and 5 days/week, respectively, for 8 weeks.

RESULTS

Our results showed that both uphill and downhill training significantly decreased the body weight, total cholesterol, and creatine kinase (CK) levels in the context of OVX-induced bone loss. On the contrary, levels of an osteogenesis indicator, osteocalcin and alkaline phosphatase were elevated. Consequently, the uphill and downhill training reduced OVX- induced bone loss in the distal femoral metaphysis. Likewise, the bone microstructure in OVX-induced bone loss was enhanced upon training. In particular, the inhibition of RANKL-induced osteoclast formation and osteoclast-specific gene expression improved upon downhill training compared to uphill training.

CONCLUSION

These results suggest that the uphill and downhill exercise types appeared to positively affect the expression of osteogenesis-related factors along with bone density and microstructure. Particularly, the downhill training has more beneficial effects on the maintenance of homeostasis during bone formation.

Gradual downhill running improves age-related skeletal muscle and bone weakness: implication of autophagy and bone morphogenetic proteins

NEW FINDINGS

What is the central question of this study? Exercise training by running has an effect on age-related muscle and bone wasting that improves physical activity and quality of life in the elderly. However, the effect of downhill running on age-related muscle and bone wasting, and its mechanisms, are unclear. What is the main finding and its importance? Gradual downhill running can improve skeletal muscle growth and bone formation by enhancing autophagy and bone morphogenetic protein signalling in aged rats. Therefore, downhill running exercise might be a practical intervention to improve skeletal muscle and bone protection in the elderly. Recent evidence suggests that autophagy and the bone morphogenetic protein (BMP) signalling pathway regulate skeletal muscle growth and bone formation in aged rats. However, the effect of downhill running on muscle growth and bone formation is not well understood. Thus, we investigated the effect of downhill and uphill running on age-related muscle and bone weakness. Young and late middle-aged rats were randomly assigned to control groups (young, YC; and late middle-aged, LMC) and two types of running training groups (late middle-aged downhill, LMD; and late middle-aged uphill, LMU). Training was progressively carried out on a treadmill at a speed of 21 m min^-1 with a slope of +10 deg for uphill training versus 16 m min^-1 with a slope of -16 deg for downhill training, both for 60 min day^-1 , 5 days week^-1 for 8 weeks. Downhill and uphill training increased autophagy-related protein 5, microtubule-associated protein light chain, Beclin-1 and p62 proteins in aged rats. In addition, superoxide dismutase, haem oxygenase-1 and the BMP signalling pathway were elevated. Phosphorylation of mammalian target of rapamycin and myogenic differentiation were increased significantly in the LMD and LMU groups. Consequently, in the femur, BMP-2, BMP-7 and autophagy molecules were highly expressed in the LMD and LMU groups. These results suggest that both downhill and uphill training appear to have a positive effect on expression of autophagy molecules and BMPs. In particular, these physiological adaptations from gradual downhill exercise have an effect on bone morphological changes and muscle quality similar to gradual uphill training interventions in ageing.

Immobilization induces nuclear accumulation of HDAC4 in rat skeletal muscle

The study described herein aimed to examine changes in HDAC4 and its downstream targets in immobilization-induced rat skeletal muscle atrophy. Eleven male Wistar rats were used, and one hindlimb was immobilized in the plantar flexion position using a plaster cast. The contralateral, non-immobilized leg served as an internal control. After 10 days, the gastrocnemius muscles were removed from both hindlimbs. Ten days of immobilization resulted in a significant reduction (-27.3 %) in gastrocnemius muscle weight. A significant decrease in AMPK phosphorylation was also observed in nuclear fractions from immobilized legs relative to the controls. HDAC4 expression was significantly increased in immobilized legs in both the cytoplasmic and nuclear fractions. Moreover, Myogenin and MyoD mRNA levels were upregulated in immobilized legs, resulting in increased Atrogin-1 mRNA expression. Our data suggest that nuclear HDAC4 accumulation is partly related to immobilization-induced muscle atrophy.

Mitochondria, muscle health, and exercise with advancing age

Skeletal muscle health is dependent on the optimal function of its mitochondria. With advancing age, decrements in numerous mitochondrial variables are evident in muscle. Part of this decline is due to reduced physical activity, whereas the remainder appears to be attributed to age-related alterations in mitochondrial synthesis and degradation. Exercise is an important strategy to stimulate mitochondrial adaptations in older individuals to foster improvements in muscle function and quality of life.

Intermittent bout exercise training down-regulates age-associated inflammation in skeletal muscles

Aging is characterized by the progressive decline in mass and function of the skeletal muscle along with increased susceptibility to inflammation, oxidative stress, and atrophy. In this study, we investigate the effect of intermittent bout and single bout exercise training on inflammatory molecules in young (3 months) and old (22 months) male Sprague-Dawley rats. The rats were divided into 6 groups. Young and old rats were randomly assigned for control and two exercise training groups, single bout (S type): 30 min/day, 5 days/week for 6 weeks and intermittent bout (I type): three times for 10 min/day, 5 days/week for 6 weeks respectively. The exercise training was carried out by a treadmill at a speed of 15m/min (young) or 10 m/min (old) with a slope of 5°. After 48 h of the final exercise bout, muscle samples were collected for biochemical assay. I type exercise training reduced the serum levels of inflammatory molecules such as interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and malondialdehyde (MDA) in old rats. By contrast, interleukin-4 (IL-4) and superoxide dismutase (SOD) were elevated. Consequently in skeletal muscles, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were decreased significantly in the old group of I type. However, the matrix metalloproteinase-2 (MMP-2) level had no positive effects. Also, phosphorylation of mammalian target of rapamycin (p-mTOR) and myogenic differentiation (MyoD) were increased markedly in S and I types of old rats. These results suggest that I type exercise training appears more effective to reduce age-associated inflammatory molecules, and may recommend in regulating against chronic complicated disease induced by aging.

Lactate dehydrogenase regulation in aged skeletal muscle: Regulation by anabolic steroids and functional overload

Aging alters the skeletal muscle response to overload-induced growth. The onset of functional overload is characterized by increased myoblast proliferation and an altered muscle metabolic profile. The onset of functional overload is associated with increased energy demands that are met through the interconversion of lactate and pyruvate via the activity of lactate dehydrogenase (LDH). Testosterone targets many of the processes activated at the onset of functional overload. However, the effect of aging on this metabolic plasticity at the onset of functional overload and how anabolic steroid administration modulates this response is not well understood. The purpose of this study was to determine if aging would alter overload-induced LDH activity and expression at the onset of functional overload and whether anabolic steroid administration would modulate this response. Five-month and 25-month male Fischer 344xF1 BRN were given nandrolone decanoate (ND) or sham injections for 14days and then the plantaris was functionally overloaded (OV) for 3days by synergist ablation. Aging reduced muscle LDH-A & LDH-B activity 70% (p<0.05). Aging also reduced LDH-A mRNA abundance, however there was no age effect on LDH-B mRNA abundance. In 5-month muscle, both ND and OV decreased LDH-A and LDH-B activity. However, there was no synergistic or additive effect. In 5-month muscle, ND and OV decreased LDH-A mRNA expression with no change in LDH-B expression. In 25-month muscle, ND and OV increased LDH-A and LDH-B activity. LDH-A mRNA expression was not altered by ND or OV in aged muscle. However, there was a main effect of OV to decrease LDH-B mRNA expression. There was also an age-induced LDH isoform shift. ND and OV treatment increased the "fast" LDH isoforms in aged muscle, whereas ND and OV increased the "slow" isoforms in young muscle. Our study provides evidence that aging alters aspects of skeletal muscle metabolic plasticity normally induced by overload and anabolic steroid administration.

Effect of exercise training of different intensities on anti-inflammatory reaction in streptozotocin-induced diabetic rats

The study investigated the effect of high- and low-intensity exercise training on inflammatory reaction of blood and skeletal muscle in streptozotocin (STZ)-induced diabetic male Sprague-Dawley rats (243 ± 7 g, 8 weeks). The rats completed treadmill running in either high-intensity exercise (6 weeks of exercise training, acute bouts of exercise) or low-intensity exercise (6 weeks of exercise training). Non-running, sedentary rats served as controls. To induce diabetes mellitus, rats received a peritoneal injection of STZ (50 mg · kg⁻¹). Rats were sacrificed immediately after an acute bout of exercise and 6 weeks of exercise training. Inflammatory factors were analyzed by ELISA and by immune blotting from the soleus and extensor digitorum longus muscles. In the serum, inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-4) and reactive oxygen species (ROS) (nitric oxide and malondialdehyde) increased in diabetic rats. However, all exercise training groups displayed reduced inflammatory cytokines and reactive oxygen species. In skeletal muscles, low-intensity exercise training, but not high intensity exercise, reduced the levels of COX-2, iNOS, and MMP-2, which were otherwise markedly elevated in the presence of STZ. Moreover, the levels of GLUT-4 and MyoD were effectively increased by different exercise intensity and exercise duration. Low-intensity exercise training appeared most effective to reduce diabetes-related inflammation. However, high-intensity training also reduced inflammatory factors in tissue-specific muscles. The data implicate regular exercise in protecting against chronic inflammatory diseases, such as diabetes.