Role of AMPK and PPARγ1 in exercise-induced lipoprotein lipase in skeletal muscle

Dietary fatty acids and flight-training influence the expression of the eicosanoid hormone prostacyclin in songbirds

Diet shifts can alter tissue fatty acid composition in birds, which is subsequently related to metabolic patterns. Eicosanoids, short-lived fatty acid-derived hormones, have been proposed to mediate these relationships but neither baseline concentrations nor the responses to diet and exercise have been measured in songbirds. We quantified a stable derivative of the vasodilatory eicosanoid prostacyclin in the plasma of male European Starlings (Sturnus vulgaris, N = 25) fed semisynthetic diets with either high (PUFA) or low (MUFA) amounts of n6 fatty acid precursors to prostacyclin. Plasma samples were taken from each bird before, immediately after, and two days following a 15-day flight-training regimen that a subset of birds (N = 17) underwent. We found elevated prostacyclin levels in flight-trained birds fed the PUFA diet compared to those fed the MUFA diet and a positive relationship between prostacyclin and body condition, indexed by fat score. Prostacyclin concentrations also significantly decreased at the final time point. These results are consistent with the proposed influences of precursor availability (i.e., dietary fatty acids) and regulatory feedback associated with exercise (i.e., fuel supply and inflammation), and suggest that prostacyclin may be an important mediator of dietary influence on songbird physiology.

Aerobic exercise-induced decrease of chemerin improved glucose and lipid metabolism and fatty liver of diabetes mice through key metabolism enzymes and proteins

Our previous studies have implicated an important role of adipokine chemerin in exercise-induced improvements of glycolipid metabolism and fatty liver in diabetes rat, but the underlying mechanisms remain unknown. This study first used an exogenous chemerin supplement to clarify the roles of decreased chemerin in exercised diabetes mice and possible mechanisms of glucose and lipid metabolism key enzymes and proteins [such as adipose triglyceride lipase (ATGL), lipoprotein lipase (LPL), phosphoenolpyruvate carboxykinase (PEPCK), and glucose transporter 4 (GLUT4)]. In addition, two kinds of adipose-specific chemerin knockout mice were generated to demonstrate the regulation of chemerin on glucose and lipid metabolism enzymes and proteins. We found that in diabetes mice, exercise-induced improvements of glucose and lipid metabolism and fatty liver, and exercise-induced increases of ATGL, LPL, and GLUT4 in liver, gastrocnemius and fat were reversed by exogenous chemerin. Furthermore, in chemerin knockdown mice, chemerin(-/-)∙adiponectin mice had lower body fat mass, improved blood glucose and lipid, and no fatty liver; while chemerin(-/-)∙fabp4 mice had hyperlipemia and unchanged body fat mass. Peroxisome proliferator-activated receptor γ (PPARγ), ATGL, LPL, GLUT4 and PEPCK in the liver and gastrocnemius had improve changes in chemerin(-/-)·adiponectin mice while deteriorated alterations in chemerin(-/-)·fabp4 mice, although PPARγ, ATGL, LPL, and GLUT4 increased in the fat of two kinds of chemerin(-/-) mice. CONCLUSIONS: Decreased chemerin exerts an important role in exercise-induced improvements of glucose and lipid metabolism and fatty liver in diabetes mice, which was likely to be through PPARγ mediating elevations of ATGL, LPL and GLUT4 in peripheral metabolic organs.

An AMP Kinase-pathway dependent integrated stress response regulates ageing and longevity

The purpose of this article is to investigate the role of the AMP-kinase pathway (AMPK pathway) in the induction of a concomitant set of health benefits by exercise, numerous drugs, and health ingredients, all of which are adversely affected by ageing. Despite the AMPK pathway being frequently mentioned in relation to both these health effects and ageing, it appears challenging to understand how the activation of a single biochemical pathway by various treatments can produce such a diverse range of concurrent health benefits, involving so many organs. We discovered that the AMPK pathway functions as an integrated stress response system because of the presence of a feedback loop in it. This evolutionary conserved stress response system detects changes in AMP/ATP and NAD/NADH ratios, as well as the presence of potential toxins, and responds by activating a common protective transcriptional response that protects against aging and promotes longevity. The inactivation of the AMPK pathway with age most likely explains why ageing has a negative impact on the above-mentioned set of health benefits. We conclude that the presence of a feedback loop in the AMP-kinase pathway positions this pathway as an AMPK-ISR (AMP Kinase-dependent integrated stress response) system that responds to almost any type of (moderate) environmental stress by inducing various age-related health benefits and longevity.

Improvement of low-intensity long-time running performance in rats by intake of glucosyl hesperidin

Recently, the use of ergogenic aids in sports by both athletes and fans has increased. Moreover, the overall demand for new ergogenic aids has increased. Hesperidin is a polyphenol that is useful for improving exercise performance by activating energy generation through β-oxidation and oxidative phosphorylation in skeletal muscles. However, it is difficult to use this compound as an ergogenic aid because of its poor water solubility and low bioavailability. Glucosyl hesperidin is formed when one molecule of glucose is transferred to hesperidin via glycosyl-transferase. It is 10,000× more soluble and has 3.7× higher bioavailability than hesperidin. In this study, we assessed whether continuous (14 days) intake of glucosyl hesperidin improves the aerobic exercise capacity of rats during long-term acute exercise. Although glucosyl hesperidin intake did not improve the performance of high-intensity running (30 m/min), we did observe improvement in low-intensity running (15 m/min) (p < 0.05). We demonstrate that in sedentary rats, glucosyl hesperidin intake increased β-oxidation and oxidative phosphorylation in the skeletal muscle (p < 0.05 and p < 0.01, respectively). Glucosyl hesperidin intake may have created a metabolic state useful for long-term exercise. In conclusion, the continuous intake of glucosyl hesperidin improved the aerobic exercise capacity of rats during long-term acute exercise.

Exercise-induced increase in M2 macrophages accelerates wound healing in young mice

Moderate-intensity exercise performed during wound healing has been reported to decrease inflammatory cytokines and chemokines and accelerate wound healing. However, its effect on macrophage phenotype and the mechanism by which exercise accelerates wound healing remain unclear. The purpose of this study was to investigate the effect of exercise on macrophage phenotype during wound healing and to clarify the relationship between angiogenesis and wound healing. 12-week-old male C57BL/6J mice were divided into sedentary (n = 6) and exercise groups (n = 6). The exercise group performed moderate-intensity treadmill running exercise (9.0 m/min, 60 min) for 10 days. Double immunofluorescence analysis was performed using F4/80+ inducible nitric oxide synthase (iNOS)+ for M1 macrophages, F4/80+ transforming growth factor-beta (TGF-β)1+ for M2 macrophages, and CD31+ alpha smooth muscle actin (α-SMA)+ for angiogenesis. The exercise group showed significantly accelerated wound healing compared with the sedentary group. From early wound healing onward, exercise significantly inhibited M1 macrophage infiltration and increased M2 macrophage count. Exercise also significantly increased angiogenesis. Furthermore, the M2 macrophage phenotype was significantly correlated with angiogenesis in the exercise group, indicating that M2 macrophages and angiogenesis are related to accelerated wound healing. These findings suggest that moderate-intensity exercise increases TGF-β1 derived from M2 macrophages, which may be associated with enhanced angiogenesis and wound healing in young mice.

Pharmaceutical Agents for Contractile-Metabolic Dysfunction After Volumetric Muscle Loss

Volumetric muscle loss (VML) injuries represent a majority of military service member casualties and are common in civilian populations following blunt and/or penetrating traumas. Characterized as a skeletal muscle injury with permanent functional impairments, there is currently no standard for rehabilitation, leading to lifelong disability. Toward developing rehabilitative strategies, previous research demonstrates that the remaining muscle after a VML injury lacks similar levels of plasticity or adaptability as healthy, uninjured skeletal muscle. This may be due, in part, to impaired innervation and vascularization of the remaining muscle, as well as disrupted molecular signaling cascades commonly associated with muscle adaptation. The primary objective of this study was to assess the ability of four pharmacological agents with a strong record of modulating muscle contractile and metabolic function to improve functional deficits in a murine model of VML injury. Male C57BL/6 mice underwent a 15% multimuscle VML injury of the posterior hindlimb and were randomized into drug treatment groups (formoterol [FOR], 5-aminoimidazole-4-carboxamide riboside [AICAR], pioglitazone [PIO], or sildenafil [SIL]) or untreated VML group. At the end of 60 days, the injury model was first validated by comparison to age-matched injury-naive mice. Untreated VML mice had 22% less gastrocnemius muscle mass, 36% less peak-isometric torque, and 27% less maximal mitochondrial oxygen consumption rate compared to uninjured mice (p < 0.01). Experimental drug groups were, then, compared to VML untreated, and there was minimal evidence of efficacy for AICAR, PIO, or SIL in improving contractile and metabolic functional outcomes. However, FOR-treated VML mice had 18% greater peak isometric torque (p < 0.01) and permeabilized muscle fibers had 36% greater State III mitochondrial oxygen consumption rate (p < 0.01) compared to VML untreated mice, suggesting an overall improvement in muscle condition. There was minimal evidence that these benefits came from greater mitochondrial biogenesis and/or mitochondrial complex protein content, but could be due to greater enzyme activity levels for complex I and complex II. These findings suggest that FOR treatment is candidate to pair with a rehabilitative approach to maximize functional improvements in VML-injured muscle. Impact statement Volumetric muscle loss (VML) injuries result in deficiencies in strength and mobility, which have a severe impact on patient quality of life. Despite breakthroughs in tissue engineering, there are currently no treatments available that can restore function to the affected limb. Our data show that treatment of VML injuries with clinically available and FDA-approved formoterol (FOR), a beta-agonist, significantly improves strength and metabolism of VML-injured muscle. FOR is therefore a promising candidate for combined therapeutic approaches (i.e., regenerative rehabilitation) such as pairing FOR with structured rehabilitation or cell-seeded biomaterials as it may provide greater functional improvements than either strategy alone.

Long non-coding RNA Tug1 modulates mitochondrial and myogenic responses to exercise in skeletal muscle

Background

Mitochondria have an essential role in regulating metabolism and integrate environmental and physiological signals to affect processes such as cellular bioenergetics and response to stress. In the metabolically active skeletal muscle, mitochondrial biogenesis is one important component contributing to a broad set of mitochondrial adaptations occurring in response to signals, which converge on the biogenesis transcriptional regulator peroxisome proliferator-activated receptor coactivator 1-alpha (PGC-1α), and is central to the beneficial effects of exercise in skeletal muscle. We investigated the role of long non-coding RNA (lncRNA) taurine-upregulated gene 1 (TUG1), which interacts with PGC-1α in regulating transcriptional responses to exercise in skeletal muscle.

Results

In human skeletal muscle, TUG1 gene expression was upregulated post-exercise and was also positively correlated with the increase in PGC-1α gene expression (PPARGC1A). Tug1 knockdown (KD) in differentiating mouse myotubes led to decreased Ppargc1a gene expression, impaired mitochondrial respiration and morphology, and enhanced myosin heavy chain slow isoform protein expression. In response to a Ca²⁺-mediated stimulus, Tug1 KD prevented an increase in Ppargc1a expression. RNA sequencing revealed that Tug1 KD impacted mitochondrial Ca²⁺ transport genes and several downstream PGC-1α targets. Finally, Tug1 KD modulated the expression of ~300 genes that were upregulated in response to an in vitro model of exercise in myotubes, including genes involved in regulating myogenesis.

Conclusions

We found that TUG1 is upregulated in human skeletal muscle after a single session of exercise, and mechanistically, Tug1 regulates transcriptional networks associated with mitochondrial calcium handling, muscle differentiation and myogenesis. These data demonstrate that lncRNA Tug1 exerts regulation over fundamental aspects of skeletal muscle biology and response to exercise stimuli.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01366-4.

Exploratory Systematic Review and Meta-Analysis of Panax Genus Plant Ingestion Evaluation in Exercise Endurance

Background: Many studies that use food containing Panax genus plants (PGPs) have been conducted but most of them have not mentioned the effective compounds ginsenosides and their composition. Therefore, we conducted a systematic review and meta-analysis of time to exhaustion as an index of exercise endurance with ingestion of PGPs or ginsenosides to reveal their effects. Methods: We performed a systematic review with a comprehensive and structured literature search using seven literature databases, four clinical trial databases, and three general web search engines during 15–22 March 2021. A random-effects model was applied to calculate the standardized mean difference (SMD) and 95% confidence interval (CI) as the difference between the mean in the treatment and placebo groups. We evaluated the risk of bias of individual studies along with the risk of bias tool in the Cochrane handbook. This study was funded by Maruzen Pharmaceuticals Co., Ltd. (Hiroshima, Japan). The protocol for this study was registered with the UMIN-CTR (No. UMIN000043341). Results: Five studies met the inclusion criteria. The number of total participants was 90, with 59 in the ingestion-PGPs group and 64 in the control group, because three studies were crossover-design trials. We found that ingestion of PGPs or ginsenosides significantly improved exercise endurance (SMD [95% CI]: 0.58 [0.22–0.95], I² = 0%). It was suggested that ginsenoside Rg₁ (Rg₁) and PGPs extract containing Rg₁ were significantly effective in improving exercise endurance (SMD [95% CI]: 0.70 [0.14–1.27], I² = 30%) by additional analysis. Conclusions: This systematic review suggests that the ingestion of PGPs or ginsenosides, especially Rg₁, is effective in improving exercise endurance in healthy adults. However, further high-quality randomized controlled trials are required because imprecision and publication bias cannot be ignored in this systematic review.

AICAR stimulates mitochondrial biogenesis and BCAA catabolic enzyme expression in C2C12 myotubes

Type 2 diabetes is characterized by reduced insulin sensitivity, elevated blood metabolites, and reduced mitochondrial metabolism. Insulin resistant populations often exhibit reduced expression of genes governing mitochondrial metabolism such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Interestingly, PGC-1α regulates the expression of branched-chain amino acid (BCAA) metabolism, and thus, the consistently observed increased circulating levels of BCAA in diabetics may be partially explained by reduced PGC-1α expression. Conversely, PGC-1α upregulation appears to increase BCAA catabolism. PGC-1α activity is regulated by 5'-AMP-activated protein kinase (AMPK), however, only limited experimental data exists on the effect of AMPK activation in the regulation of BCAA catabolism. The present report examined the effects of the commonly used AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) on the metabolism and expression of several related targets (including BCAA catabolic enzymes) of cultured myotubes. C2C12 myotubes were treated with AICAR at 1 mM for up to 24 h. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Metabolic gene and protein expression were assessed via qRT-PCR and western blot, respectively. AICAR treatment significantly increased mitochondrial content and peak mitochondrial capacity. AICAR treatment also increased AMPK activation and mRNA expression of several regulators of mitochondrial biogenesis but reduced glycolytic metabolism and mRNA expression of several glycolytic enzymes. Interestingly, branched-chain alpha-keto acid dehydrogenase a (BCKDHa) protein was significantly increased following AICAR-treatment suggesting increased overall BCAA catabolic capacity in AICAR-treated cells. Together, these experiments demonstrate AICAR/AMPK activation can upregulate BCAA catabolic machinery in a model of skeletal muscle.

Maslinic acid activates mTORC1 and human TGR5 and induces skeletal muscle hypertrophy

Maslinic acid, a naturally occurring pentacyclic triterpene in more than 30 plants (including olives), reportedly increases human muscle mass and muscle strength; however, the underlying molecular mechanism remains unknown. C57BL/6J mice were fed a standard diet or supplemented with 0.27% maslinic acid for 4 weeks, and their skeletal muscle mass was measured. Mice that consumed maslinic acid displayed significant increases in gastrocnemius and soleus muscle mass. Cultured mouse-C2C12 skeletal muscle cells were treated with mammalian target of rapamycin complex 1 (mTORC1) or protein kinase b (Akt) inhibitor, and protein synthesis was quantified. Maslinic acid accelerated protein synthesis via mTORC1 activation independent of Akt. Furthermore, maslinic acid activated human Takeda G protein-coupled receptor 5 (TGR5) more strongly than mouse TGR5, augmenting the expression of several genes related to muscular hypertrophy. Maslinic acid activated mTORC1 and human TGR5, implying its contribution to human muscular hypertrophy through these effects.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Effects of Living High-Training Low and High on Body Composition and Metabolic Risk Markers in Overweight and Obese Females

This study examined the effects of 4 weeks of living high-training low and high (LHTLH) under moderate hypoxia on body weight, body composition, and metabolic risk markers of overweight and obese females. Nineteen healthy overweight or obese females participated in this study. Participants were assigned to the normoxic training group (NG) or the LHTLH group (HG). The NG participants lived and trained at sea level. The HG participants stayed for approximately 10 hours in a simulated 2300 m normobaric state of hypoxia for six days a week and trained for 2 hours 3 times a week under the same simulated hypoxia. The interventions lasted for 4 weeks. All groups underwent dietary restriction based on resting metabolic rate. The heart rate of the participants was monitored every ten minutes during exercise to ensure that the intensity was in the aerobic range. Compared with the preintervention values, body weight decreased significantly in both the NG and the HG (−8.81 ± 2.09% and −9.09 ± 1.15%, respectively). The fat mass of the arm, leg, trunk, and whole body showed significant reductions in both the NG and the HG, but no significant interaction effect was observed. The percentage of lean soft tissue mass loss in the total body weight loss tended to be lower in the HG (27.61% versus 15.94%, P=0.085). Between the NG and the HG, significant interaction effects of serum total cholesterol (−12.66 ± 9.09% versus −0.05 ± 13.36%,) and apolipoprotein A₁ (−13.66 ± 3.61% versus −5.32 ± 11.07%, P=0.042) were observed. A slight increase in serum high-density lipoprotein cholesterol (HDL-C) was observed in the HG (1.12 ± 12.34%) but a decrease was observed in the NG (−11.36 ± 18.91%). The interaction effect of HDL-C between NG and HG exhibited a significant trend (P=0.055). No added effects on serum triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), or APO-B were observed after 4 weeks of LHTLH. In conclusion, 4 weeks of LHTLH combined with dietary restriction could effectively reduce the body weight and body fat mass of overweight and obese females. Compared with training and sleeping under normoxia, no additive benefit of LHTLH on the loss of body weight and body fat mass was exhibited. However, LHTLH may help to relieve the loss of lean soft tissue mass and serum HDL-C.

A comparative study of the antidiabetic effect of two training protocols in streptozotocin-nicotinamide diabetic rats

Background Physical inactivity is the major risk factor for type 2 diabetes (T2D). The present study was conducted to investigate the effects of resistance training and endurance training on diabetic-related metabolic parameters in diabetic rats. Materials and methods Twenty-four male Wistar rats were randomly assigned to four groups of six rats each: control group (C), diabetic group (D), resistance training group (RES) and endurance training group (END). T2D was induced intraperitoneally using nicotinamide (120 mg/kg) and streptozotocin (STZ, 65 mg/kg). The training period was 70 days. The irisin, betatrophin, insulin, fasting blood glucose (FBG) and lipid profiles were measured in the serum of all rats. Results Diabetes significantly increased serum levels of FBG (p < 0.001), which were decreased significantly after the administration of training (p < 0.001). Training administration had a significant effect in normalizing serum lipid profiles (p < 0.001) and it was shown to increase the serum levels of irisin, betatrophin (p < 0.001) and insulin (END: p < 0.001 and resistance training: p < 0.05). It was also found that the endurance training was more effective in improving this parameters when compared with resistance training (p < 0.05). In addition, the irisin revealed a significant positive association with betatrophin (END: p < 0.01 and resistance training: p < 0.05) and insulin (END: p < 0.01 and RES: p < 0.05) values in diabetic groups. Conclusion This study demonstrated that endurance training was more effective in diabetic related metabolic derangement compared with resistance training. This effect is probably due to better regulation of irisin, betatrophin and insulin relative to resistance training.

High-intensity interval training improved fasting blood glucose and lipid profiles in type 2 diabetic rats more than endurance training; possible involvement of irisin and betatrophin

BACKGROUND AND AIMS

In this study, we aimed to investigate the effects of 10 weeks of high-intensity interval training (HIIT) and endurance training (END) on irisin, betatrophin, insulin, fasting blood glucose (FBG) concentrations, and lipid profiles in diabetic rats.

METHODS

Twenty-four Wistar rats (weight: 200-250 g) were randomly assigned into four groups as follows: (1) control (Cnt), (2) diabetic (Dibt), (3) diabetic HIIT (Dibt-HIIT), and (4) diabetic END (Dibt-END). For inducing diabetes, after 12 h of food starvation, nicotinamide (120 mg/kg) and streptozotocin (STZ; 65 mg/kg) were intraperitoneally injected. The diabetic training groups received 10 weeks of HIIT or END training following the induction of diabetes. Twenty-four hours following the last training session, blood serum samples were collected for evaluating the concentration of irisin, betatrophin, and insulin hormones through enzyme-linked immunosorbent assay.

RESULTS

FBG and lipid profiles were measured by biochemical kits. A significant increase in the serum concentration of irisin (p < 0.05), betatrophin (p < 0.05), and insulin (p < 0.001) and significant decrease in the FBG (P < 0.01) and lipid profiles (p < 0.01) were observed in the Dibt-HIIT group compared to the Dibt-END group. In addition, irisin revealed a significant positive association with betatrophin and insulin values in diabetic training groups (p < 0.01).

CONCLUSIONS

It seems that HIIT leads to a more extensive improvement in diabetic conditions compared to the END training. Therefore, HIIT appears to be an important time-efficient approach for the treatment of type 2 diabetes.

Omega-3 Fatty Acids-Enriched Fish Oil Activates AMPK/PGC-1α Signaling and Prevents Obesity-Related Skeletal Muscle Wasting

Obesity is known to cause skeletal muscle wasting. This study investigated the effect and the possible mechanism of fish oil on skeletal muscle wasting in an obese rat model. High-fat (HF) diets were applied to induce the defects of lipid metabolism in male Sprague-Dawley rats with or without substitution of omega-3 fatty acids-enriched fish oil (FO, 5%) for eight weeks. Diets supplemented with 5% FO showed a significant decrease in the final body weight compared to HF diet-fed rats. The decreased soleus muscle weights in HF diet-fed rats could be improved by FO substitution. The decreased myosin heavy chain (a muscle thick filament protein) and increased FOXO3A and Atrogin-1 (muscle atrophy-related proteins) protein expressions in soleus muscles of HF diet-fed rats could also be reversed by FO substitution. FO substitution could also significantly activate adenosine monophosphate (AMP)-activated protein kinase (AMPK) phosphorylation, peroxisome-proliferator-activated receptor-γ (PPARγ) coactivator 1α (PGC-1α), and PPARγ protein expression and lipoprotein lipase (LPL) mRNA expression in soleus muscles of HF diet-fed rats. These results suggest that substitution of FO exerts a beneficial improvement in the imbalance of lipid and muscle metabolisms in obesity. AMPK/PGC-1α signaling may play an important role in FO-prevented obesity-induced muscle wasting.

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.

In vitro experimental models for examining the skeletal muscle cell biology of exercise: the possibilities, challenges and future developments

Exercise provides a cornerstone in the prevention and treatment of several chronic diseases. The use of in vivo exercise models alone cannot fully establish the skeletal muscle-specific mechanisms involved in such health-promoting effects. As such, models that replicate exercise-like effects in vitro provide useful tools to allow investigations that are not otherwise possible in vivo. In this review, we provide an overview of experimental models currently used to induce exercise-like effects in skeletal muscle in vitro. In particular, the appropriateness of electrical pulse stimulation and several pharmacological compounds to resemble exercise, as well as important technical considerations, are addressed. Each model covered herein provides a useful tool to investigate different aspects of exercise with a level of abstraction not possible in vivo. That said, none of these models are perfect under all circumstances, and the choice of model (and terminology) used should be informed by the specific research question whilst accounting for the several inherent limitations of each model. Further work is required to develop and optimise the current experimental models used, such as combination with complementary techniques during treatment, and thereby improve their overall utility and impact within muscle biology research.

Relationship between Cardiorespiratory Fitness and Non-High-Density Lipoprotein Cholesterol: A Cohort Study

Aim: Recent studies have suggested that non-high-density lipoprotein cholesterol (non-HDL-C) may be a good marker of coronary heart disease and cardiovascular disease risk. Therefore, we investigated the relationship between cardiorespiratory fitness (CRF) and non-HDL-C.

Methods: We evaluated CRF and the incidence of high level of non-HDL-C in 4,067 Japanese men without dyslipidemia. The participants were given a submaximal exercise test, a medical examination, and questionnaires on their health habits in 1986. A cycle ergometer was used to measure the CRF and maximal oxygen uptake was estimated. The incidence of a high level of non-HDL -C (≥ 170 mg/dL) from 1986 to 2006 was ascertained based on the fasting blood levels. A high level of non-HDL-C was found in 1,482 participants during the follow-up. Cox proportional hazard models were used to obtain the hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of a high level of non-HDL-C.

Results: Following age adjustment, and using the lowest CRF group (quartile I) as reference, the HRs and 95% CIs for quartiles II through IV were: 1.00 (95% CI: 0.87–1.15), 0.87 (95% CI: 0.76–1.00), and 0.70 (95% CI: 0.60–0.81), respectively (P for trend < 0.001). After additional adjustment for body mass index, systolic blood pressure, smoking, alcohol intake, and family history of dyslipidemia, the HRs and 95% CIs were: 1.05 (95% CI: 0.92–1.21), 0.94 (95% CI: 0.81–1.08), and 0.79 (95% CI: 0.67–0.92), respectively (P for trend = 0.001).

Conclusions: These results suggest that there is an inverse relationship between CRF levels and the incidence of a high level of non-HDL-C in Japanese men.

The exercise-inducible bile acid receptor Tgr5 improves skeletal muscle function in mice

TGR5 (also known as G protein-coupled bile acid receptor 1, GPBAR1) is a G protein-coupled bile acid receptor that is expressed in many diverse tissues. TGR5 is involved in various metabolic processes, including glucose metabolism and energy expenditure; however, TGR5's function in skeletal muscle is not fully understood. Using both gain- and loss-of-function mouse models, we demonstrate here that Tgr5 activation promotes muscle cell differentiation and muscle hypertrophy. Both young and old transgenic mice with muscle-specific Tgr5 expression exhibited increased muscle strength. Moreover, we found that Tgr5 expression is increased by the unfolded protein response (UPR), which is an adaptive response required for maintenance of endoplasmic reticulum (ER) homeostasis. Both ER stress response element (ERSE)- and unfolded protein response element (UPRE)-like sites are present in the 5' upstream region of the Tgr5 gene promoter and are essential for Tgr5 expression by Atf6α (activating transcription factor 6α), a well known UPR-activated transcriptional regulator. We observed that in the skeletal muscle of mice, exercise-induced UPR increases Tgr5 expression, an effect that was abrogated in Atf6α KO mice, indicating that Atf6α is essential for this response. These findings indicate that the bile acid receptor Tgr5 contributes to improved muscle function and provide an additional explanation for the beneficial effects of exercise on skeletal muscle activity.

[Pharmacological Mechanisms of Boiogito and Bofutsushosan in Diabetes and Obesity Models]

　The antihyperglycemic activities of extracts of boiogito (BOT) and bofutsushosan (BTS) were investigated in streptozotocin-induced (STZ)-diabetic mice. BOT extract containing Stephania tetrandra S. MOORE root (stephania), has more potent antihyperglycemic activity than BOT extract containing sinomenium stem (sinomenium). Extracts of stephania and astragalus root (astragalus) exert combined effects in the antihyperglycemic and insulinotropic activities of BOT extract. Fangchinoline, but not tetrandrine, in stephania plays a role in its activity. Formononetin in astragalus potentiates the actions of fangchinoline. Tetrandrine has antiangiogenic effects on choroidal vessels in STZ-diabetic rats, which are associated with the inhibition of tumor necrosis factor (TNF)-α-induced nuclear factor (NF)-κB activation. BTS extract has shown antihyperglycemic and insulinotropic activities whereas gardenia fruit (gardenia) extract in BTS has antihyperglycemic, but not insulinotropic, activity in the diabetic mice. Gardenia extract decreased the HOMA-IR level and increased insulin-stimulated 2-deoxyglucose (2-DG) uptake to skeletal muscle. The effects of gardenia extract on 2-DG uptake were associated with the upregulation of glucose transporter type 4 and Akt phosphorylation. Gardenia extract was also shown to have antihyperglycemic and insulinotropic actions in high-fat diet (HFD)-fed and STZ-diabetic mice. In addition, gardenia extract decreased the production of TNF-α and leptin, and increased the production of adiponectin in the visceral adipose tissues. In the early administration period, BTS extract increased mRNA expression levels of leptin, adiponectin, and UCP1 in brown adipose tissues in HFD-fed obese mice. With a longer duration of administration, BTS extract improved insulin resistance and subsequently reduced serum leptin and triglyceride levels in parallel with visceral adipose tissue volume and size.

Insulin degrading enzyme contributes to the pathology in a mixed model of Type 2 diabetes and Alzheimer's disease: possible mechanisms of IDE in T2D and AD

Insulin degrading enzyme (IDE) is believed to act as a junction point of Type 2 diabetes (T2D) and Alzheimer's disease (AD); however, the underlying mechanism was not completely clear yet. Transgenic APPSwe/PS1 mice were used as the AD model and were treated with streptozocin/streptozotocin (STZ) to develop a mixed mice model presenting both AD and T2D. Morris Water Maze (MWM) and recognition task were performed to trace the cognitive function. The detection of fasting plasma glucose (FPG) and plasma insulin concentration, and oral glucose tolerance test (OGTT) were used to trace the metabolism evolution. Aβ40 and Aβ42 were quantified by colorimetric ELISA kits. The mRNA or protein expression levels were determined by quantitative real-time RT-PCR and Western blotting analysis respectively. T2D contributes to the AD progress by accelerating and worsening spatial learning and recognition impairments. Metabolic parameters and glucose tolerance were significantly changed in the presence of the AD and T2D. The expression levels of IDE, PPARγ, and AMPK were down-regulated in mice with AD and T2D. PPARγ activator rosiglitazone (RSZ) or AMPK activator AICAR increased the expression level of IDE and decreased Aβ levels in mice with AD and T2D. RSZ or AICAR treatment also alleviated the spatial learning and recognition impairments in AD and T2D mice. Our results found that, in the mice with T2D and AD, the activators of PPARγ/AMPK signaling pathway significantly increased the expression level of IDE, and decreased the accumulation of Aβ40 and Aβ42, as well as alleviated the spatial learning and recognition impairments.

Mechanisms for the anti-obesity actions of bofutsushosan in high-fat diet-fed obese mice

BACKGROUND

The Kampo medicine bofutsushosan (BTS; Pulvis ledebouriellae compositae; Fang Feng Tong Sheng San) has been used as an anti-obesity treatment in overweight patients. In this study, we assessed the underlying physiological changes induced by BTS in obese mice maintained on a high-fat diet.

METHODS

Male ICR mice were fed a 60% kcal fat diet for 5 weeks starting at 4 weeks of age and then fed the same diet with administration of water (control) or aqueous BTS extract (1.0-2.0 g/kg) for 25 days. Body weight, wet weight of isolated white adipose tissue, and obesity-related serum parameters (glucose, lipids, leptin, adiponectin) were measured after treatment. The mRNA expression levels of leptin, adiponectin, and UCP1 in the adipose tissues were determined by quantitative real-time polymerase chain reaction after the first 5 days of treatment.

RESULTS

Bofutsushosan (1.5-2.0 g/kg) significantly decreased total body weight and total wet weight of white adipose tissue isolated from subcutaneous (retroperitoneal) and visceral regions (epididymal, mesenteric, and perirenal). At 2.0 g/kg, BTS also decreased total fat mass, visceral fat mass, and ratio of fat mass to body weight as measured by computed tomography, and significantly decreased epididymal adipocyte size after 14 and 25 days' treatment. Twenty-five days' treatment lowered serum glucose, insulin, leptin, and triglycerides, and reduced homeostasis model assessment-insulin resistance. Alternatively, 2.0 g/kg BTS significantly increased mRNA levels of adiponectin, leptin, and UCP1 in interscapular brown adipose tissue but not epididymal white adipose tissue after 5 days' administration.

CONCLUSION

In the early administration period, BTS increased mRNA expression levels of leptin, adiponectin, and UCP1 in brown adipose tissues. With longer administration, BTS improved insulin resistance, and subsequently reduced serum levels of leptin and triglyceride in parallel with decreased visceral white adipose tissue volume and adipocyte size.

Effect of Selenium Deficiency on Phosphorylation of the AMPK Pathway in Rats

Selenium is an important trace element for human health. Previous studies have raised concern that dietary selenium intake may change energy metabolism. AMP-activated protein kinase (AMPK) is a sensor of energy status that controls cellular energy homeostasis. We aimed to determine the effect of selenium on the phosphorylation of AMPK pathway between Se-deficient and normal Sprague-Dawley rats. Twenty-four weaning rats were fed either a Se-deficient diet (0.02 mg Se/kg) or a standard diet (0.18 mg Se/kg). After 109 days, total serum levels of non-esterified fatty acid and total amino acids were significantly higher and the serum insulin concentration was significantly lower in Se-deficient rats than in healthy controls. Selenium concentration and the activity of glutathione peroxidase (GPx) in myocardial tissue were significantly lower in Se-deficient rats. Importantly, mRNA levels of acetyl-CoA carboxylase beta (ACACB), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and protein levels of p-AMPKα were increased in the Se-deficient group compared to normal controls (p < 0.05). In conclusion, our results suggest that selenium deficiency induces changes in metabolic and molecular parameters involved in energy metabolism in the AMPK pathway.

Aerobic interval exercise improves parameters of nonalcoholic fatty liver disease (NAFLD) and other alterations of metabolic syndrome in obese Zucker rats

Metabolic syndrome (MS) is a group of metabolic alterations that increase the susceptibility to cardiovascular disease and type 2 diabetes. Nonalcoholic fatty liver disease has been described as the liver manifestation of MS. We aimed to test the beneficial effects of an aerobic interval training (AIT) protocol on different biochemical, microscopic, and functional liver alterations related to the MS in the experimental model of obese Zucker rat. Two groups of lean and obese animals (6 weeks old) followed a protocol of AIT (4 min at 65%-80% of maximal oxygen uptake, followed by 3 min at 50%-65% of maximal oxygen uptake for 45-60 min, 5 days/week, 8 weeks of experimental period), whereas 2 control groups remained sedentary. Obese rats had higher food intake and body weight (P < 0.0001) and suffered significant alterations in plasma lipid profile, area under the curve after oral glucose overload (P < 0.0001), liver histology and functionality, and antioxidant status. The AIT protocol reduced the severity of alterations related to glucose and lipid metabolism and increased the liver protein expression of PPARγ, as well as the gene expression of glutathione peroxidase 4 (P < 0.001). The training protocol also showed significant effects on the activity of hepatic antioxidant enzymes, although this action was greatly influenced by rat phenotype. The present data suggest that AIT protocol is a feasible strategy to improve some of the plasma and liver alterations featured by the MS.

Metabolic and endocrine response to exercise: sympathoadrenal integration with skeletal muscle

Skeletal muscle has the capacity to increase energy turnover by ∼1000 times its resting rate when contracting at the maximum force/power output. Since ATP is not stored in any appreciable quantity, the muscle requires a coordinated metabolic response to maintain an adequate supply of ATP to sustain contractile activity. The integration of intracellular metabolic pathways is dependent upon the cross-bridge cycling rate of myosin and actin, substrate availability and the accumulation of metabolic byproducts, all of which can influence the maintenance of contractile activity or result in the onset of fatigue. In addition, the mobilisation of extracellular substrates is dependent upon the integration of both the autonomic nervous system and endocrine systems to coordinate an increase in both carbohydrate and fat availability. The current review examines the evidence for skeletal muscle to generate power over short and long durations and discusses the metabolic response to sustain these processes. The review also considers the endocrine response from the perspective of the sympathoadrenal system to integrate extracellular substrate availability with the increased energy demands made by contracting skeletal muscle. Finally, the review briefly discusses the evidence that muscle acts in an endocrine manner during exercise and what role this might play in mobilising extracellular substrates to augment the effects of the sympathoadrenal system.