Metabolic cross-talk between skeletal muscle and adipose tissue in high-intensity interval training vs. moderate-intensity continuous training by regulation of PGC-1α

EPA but not DHA prevents lipid metabolism disorders by regulating myogenic IL-6 in high-fat fed mice

Lipid metabolism disorder serve as a critical starting point for the development of chronic non-communicable diseases (NCDs). Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) are known for their lipid-lowering properties, but few studies have revealed their differences from the perspective of skeletal muscle endocrinology. Myogenic IL-6 has garnered significant attention for its role in energy distribution. The primary aim of this study was to investigate the effects and mechanisms of EPA and DHA on myogenic IL-6 and lipid metabolism disorders in mice, and to clarify the association between the alleviation of lipid metabolism disorders and myogenic IL-6 mediated by EPA/DHA. We found that EPA and DHA not only prevented high-fat diet-induced lipid metabolism disorders, but also up-regulated the expression of myogenic IL-6 by activating TRPV1/Ca2+ signaling in skeletal muscle. However, the lipid metabolism prevention effect mediated by EPA was weakened after knockout gene of myogenic IL-6, with its body weight and body fat increased and a large amounts of lipid deposited in the blood, liver, and adipocytes. Meanwhile, there no significantly differences of AMPK/STAT3 signaling in adipose tissue between groups after knockout gene of myogenic IL-6. Based on the results above, we concluded that EPA and DHA can stimulate the production of myogenic IL-6 through TRPV1/Ca2+ signaling in skeletal muscle. The prevention effect of lipid metabolism disorders by EPA, but not DHA, relies on myogenic IL-6, with the underlying mechanism may involving the enhancement of AMPK/STAT3 signaling mediated by myogenic IL-6 in adipose tissues.

Heterogeneity of extracellular vesicles in porcine myoblasts regulates adipocyte differentiation

The interactions between myogenic cells and adipocytes play an important role in improving carcass traits and the efficiency of energy utilization. However, there are few reports about the interaction between them mediated by small extracellular vesicles (sEV). In this study, sEV derived from porcine primary skeletal muscle stem cells (MuSCs) was found to be involved in the inhibition of porcine primary adipocyte viability, triglyceride content, Oil Red O enrichment and the expression of adipogenic genes. When the MuSCs were treated with insulin (INS) and oleic acid (OA), the effects of their secreted sEVs on adipose precursor cells were reversed, suggesting that the signaling effects of sEV are related to their own heterogeneity. Further by component heterogeneity analysis, miR-146a-5p was found to be enriched in sEVs of MuSCs and to regulate and suppress adipogenesis through its heterogeneity. This study provides an important mechanism and molecular target for small extracellular vesicles to regulate the interaction between muscle and adipose tissue and improve carcass traits at the intercellular level.

Impact of Exercise Intensity on Cerebral BDNF Levels: Role of FNDC5/Irisin

The positive effects of physical exercise (EX) are well known to be mediated by cerebral BDNF (brain-derived neurotrophic factor), a neurotrophin involved in learning and memory, the expression of which could be induced by circulating irisin, a peptide derived from Fibronectin type III domain-containing protein 5 (FNDC5) produced by skeletal muscle contraction. While the influence of EX modalities on cerebral BDNF expression was characterized, their effect on muscle FNDC5/Irisin expression and circulating irisin levels remains to be explored. The present study involved Wistar rats divided into four experimental groups: sedentary (SED), low- (40% of maximal aerobic speed, MAS), intermediate- (50% of MAS) and high- (70% of MAS) intensities of treadmill EX (30 min/day, 7 days). Soleus (SOL) versus gastrocnemius (GAS) FNDC5 and hippocampal BDNF expressions were evaluated by Western blotting. Additionally, muscular FNDC5/Irisin localization and serum/hippocampal irisin levels were studied by immunofluorescence and ELISA, respectively. Our findings revealed that (1) serum irisin and hippocampal BDNF levels vary with EX intensity, showing a threshold intensity at 50% of MAS; (2) hippocampal BDNF levels positively correlate with serum irisin but not with hippocampal FNDC5/Irisin; and (3) GAS, in response to EX intensity, overexpresses FNDC5/Irisin in type II muscle fibers. Altogether, peripheral FNDC5/Irisin levels likely explain EX-dependent hippocampal BDNF expression.

Effects of physical activity and exercise on Nucleobindin-2 gene expression and Nesfatin-1 concentration: A rapid review

The aim of this rapid review is to examine the research evidence that presents the effects of physical activity and exercise on Nucleobindin-2 (NUCB2) gene expression and Nesfatin-1 concentration. Five databases (PubMed, Science Direct, Springer, Wiley, and Google Scholar) were searched for eligible studies from the earliest available date to August 2023. In human studies, Nesfatin-1 concentration either remains unchanged or increases after exercise training. It appears that higher exercise intensity and longer duration of training accentuate the increase of blood Nesfatin-1 concentration. The few human studies that have examined the acute response of exercise on Nesfatin-1 concentration from blood draws show conflicting results. There is a severe lack of biopsy studies in humans which warrants attention. All published animal studies have used the mouse model. The majority show that regular exercise training increases tissue NUCB2/Nesfatin-1. In some animal studies, where the effects of exercise on tissue Nesfatin-1 concentration has been seen as significant, there has been no significant effect of exercise on plasma Nesfatin-1 concentration. All animal studies evaluated the effect of endurance training except one which used resistance training. No animal studies have investigated the effects of acute exercise, which warrants investigation. In conclusion, human and animal studies have shown that physical training can increase NUCB2/Nesfatin-1, but research evidence examining the effect of acute exercise is in its infancy. In addition, future comparative studies are needed to compare the effects of different training protocols on NUCB2/Nesfatin-1 in humans and animals.

Exercise Intervention for Alzheimer's Disease: Unraveling Neurobiological Mechanisms and Assessing Effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease and a major cause of age-related dementia, characterized by cognitive dysfunction and memory impairment. The underlying causes include the accumulation of beta-amyloid protein (Aβ) in the brain, abnormal phosphorylation, and aggregation of tau protein within nerve cells, as well as neuronal damage and death. Currently, there is no cure for AD with drug therapy. Non-pharmacological interventions such as exercise have been widely used to treat AD, but the specific molecular and biological mechanisms are not well understood. In this narrative review, we integrate the biology of AD and summarize the knowledge of the molecular, neural, and physiological mechanisms underlying exercise-induced improvements in AD progression. We discuss various exercise interventions used in AD and show that exercise directly or indirectly affects the brain by regulating crosstalk mechanisms between peripheral organs and the brain, including "bone-brain crosstalk", "muscle-brain crosstalk", and "gut-brain crosstalk". We also summarize the potential role of artificial intelligence and neuroimaging technologies in exercise interventions for AD. We emphasize that moderate-intensity, regular, long-term exercise may improve the progression of Alzheimer's disease through various molecular and biological pathways, with multimodal exercise providing greater benefits. Through in-depth exploration of the molecular and biological mechanisms and effects of exercise interventions in improving AD progression, this review aims to contribute to the existing knowledge base and provide insights into new therapeutic strategies for managing AD.

High intensity interval training attenuates osteoarthritis-associated hyperalgesia in rats

High-intensity interval training (HIIT) is a physical therapy that may benefit patients with osteoarthritis (OA). Cacna2d1 is a calcium channel subunit protein that plays an important role in the activity of nerve cells. However, there is currently no evidence on HIIT relieving OA-associate hyperalgesia by decreased Cacna2d1. Our study established the OA rat models with intra-articular injection of monosodium iodoacetate (MIA). This experiment was divided into two stages. The first stage comprised three groups: the control, OA, and OA-HIIT groups. The second stage comprised two groups, including the AAV-C and AAV-shRNA-Cacna2d1 groups. OA rats were positioned at the L5-L6 segments, and 20 µl of AAV virus was injected intrathecally. The pain threshold, cartilage analysis, Cacna2d1, and pain neurotransmitters were measured and compared. The pain threshold was significantly lower in OA rats than in control rats from the first to the tenth week. Starting from the sixth week, OA-HIIT rats exhibited significantly increased pain thresholds. The expression of Cacna2d1 increased in OA rats. Moreover, the knockdown of Cacna2d1 significantly down-regulated the expression of c-Fos, SP, and Vglut2 in the posterior horn of the spinal cord. In conclusion, HIIT attenuates OA-associated hyperalgesia, which may be related to the down-regulation of Cacna2d1.

The Mef2c/AdipoR1 axis is responsible for myogenic differentiation and is regulated by resistin in skeletal muscles

Previous studies have shown that accumulated lipid and insulin resistance emerges in skeletal muscle after the onset of obesity and diabetes. We have previously shown that resistin significantly increases lipid contents in C2C12 cells. However, studies evaluating the effects of resistin on skeletal muscle cells and tissues are limited; despite that, an understanding of resistin action and function on lipid alteration in skeletal muscle tissues is critical for understanding obesity-related diseases. In this study, we document that resistin increases lipid deposition both in vitro and in vivo. Further, resistin promotes fiber type transformation, decreases enzyme activities, inhibits myogenic differentiation, and decreases muscle grip and excise endurance. In addition, adiponectin signaling is activated during myocyte differentiation, but it is inhibited at elevated resistin concentrations. Mechanistic investigation revealed that mef2c is responsible for adiponectin signaling pathway inhibition by inhibiting adipoR1 expression at the transcriptional level. In conclusion, this is the first study to document that resistin increases ectopic lipid deposition in skeletal muscles via a mef2c-adipoR1 signaling pathway, which reveals for the first time the presence of crosstalk between resistin and adiponectin in skeletal muscles.

Swimming exercise and nano-l-arginine supplementation improve oxidative capacity and some autophagy-related genes in the soleus muscle of aging rats

The present research aims to evaluate the effect of swimming exercise and chitosan-coated l-arginine on mitochondrial oxidation, BCL2 Interacting Protein 3 (Bnip3), NIP-like protein × (Nix), B-cell lymphoma-extra-large (Bcl-xL) and autophagy-related protein light chain 3(LC3) expression in soleus muscle of aging rats. In this experimental research, 25 male Wistar rats were assigned into five groups randomly: young, old, old + Nano l-arginine (Nano L-a), old + exercise (Ex), and old + Nano l-arginine (Nano L-a) + exercise (Ex) (n = 5 in each). They performed a swimming exercise program five days a week for six weeks. To determine the relative strength for rats before and after performing these interventions, the 1repetition maximum (1RM) test was done as a pre and post-test. The exercise program started with 20 min and after four sessions, gradually increased to 60 min and this time was maintained until the completion of the training period. l-arginine coated with chitosan nanoparticles was given to the rats in the l-arginine-supplemented group via gavage at a dosage of 500 mg/kg/day, five days a week, for six weeks. Additionally, the rats in all groups were fed a normal diet (2.87 kcal/g and 15 % energy from fat). Upon the completion of the protocol implementation, the rats were sacrificed and the soleus muscle was fixed and frozen to determine hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), gene expression analysis, levels of reactive oxygen species (ROS), and total antioxidant capacity (TAC). The results from the present research indicated that swimming exercise and Nano l-arginine improve the strength and histology of muscle tissue in old rats (p < 0.05). Aging significantly increased the expression of Nix and Bnip3 (p < 0.05) and reduced the Bcl-xL gene expression (p < 0.05). The expression of LC3 protein also increased with aging (p < 0.05). Therapeutic interventions, such as combined treatment (old + Nano L-a + Ex) for old animals, reduced the amount of this protein in soleus muscle (p < 0.05). The ROS values also showed a significant reduction only in the old + Nano L-a + Ex group compared to the old group. Moreover, TAC values show a significant decrease in the old and old + Ex groups in comparison to the young group. The use of arginine supplement, especially in nano form, along with swimming exercise seems to reduce the oxidative damage to the elderly muscle tissue, which has a positive effect on the structure and function of the soleus muscle. Since these interventions only had a significant effect on LC3 protein, further studies with more diverse measurement methods for autophagy are suggested.

Superior cardiometabolic and cellular adaptive responses to multiple versus single daily sessions of high-intensity interval training in Wistar rats

This study aimed to compare in rats the cardiometabolic and cellular adaptative responses to 8 weeks of high-intensity interval training (HIIT) performed in a single (1xHIIT) or three shorter daily sessions (3xHIIT). Male Wistar rats were assigned to untrained (n = 10), 1xHIIT (n = 10), and 3xHIIT (n = 10) groups. Both HIIT groups performed 15 min of a treadmill run five times per week for 8 weeks. The 1xHIIT performed single daily sessions of 15 min, and the 3xHIIT performed three daily sessions of 5 min with an interval of 4 h between sessions. Resting VO₂ and VO₂max were measured using a metabolic chamber; blood pressure and heart rate were measured by plethysmography; body composition was estimated by DEXA; Glucose and insulin tolerance tests were performed; after euthanasia, hearts, gastrocnemius, and visceral fat were harvested for analysis of cardiac function, histology, and morphology. Mitochondrial densities of the gastrocnemius and left ventricle muscles were determined by electron microscopy. 3xHIIT induced similar positive adaptative responses to 1xHIIT on resting VO₂ and VO₂max, cardiac function, and mitochondria density. 3xHIIT was superior to 1xHIIT in reducing visceral fat weight and adipocyte size and improving insulin tolerance. Multiple short daily bouts of HIIT may be superior to single HIIT daily sessions in improving cardiometabolic and cellular adaptations in rats.

SPECIAL TRAINING ON LOWER LIMBS SMALL MUSCLE GROUPS STRENGTH

ABSTRACT Introduction Specific training with vibration can show short- and long-term effects on neuromuscular capacity. This training method gives muscles a frequent stimulus amplitude variation and can promote muscle strength, explosive power, neuromuscular coordination, and balance training. Objective This paper compares the effects of strength training with vibration on the strength of small muscle groups in the lower limbs of athletes. Methods 24 young people were randomly assigned to a low- and high-frequency group. Both groups used traditional strength training with the addition of 30 and 40Hz vibrational training. Training with load intensity between 30 and 70% of maximal strength lasting 60 minutes was repeated in 3 weekly sessions for eight weeks. Functional tests were recorded before and after the experiment, and their results were statistically analyzed. Results The peak torque of the hip muscles of the two groups of athletes increased significantly after training (P<0.05). In the high-frequency athletes, the peak in the hip extensor increased by 15.3% and the flexor by 18.2%; in the low-frequency group, there was an increase of 10.3%, representing a very significant difference (P<0.01). Conclusion Additional vibration stimulation for resistance strength training can effectively improve strength training. With a relatively small load, this training method can effectively improve maximal muscular strength, explosive power, and muscular endurance. Evidence level II; Therapeutic Studies - Investigating the results.

Systematic Review and Meta-Analysis of Circulating Irisin Levels Following Endurance Training: Results of Continuous and Interval Training

Background

Irisin has been suggested as a helpful hormone for adverse metabolic conditions. However, the interaction between acute endurance exercises and irisin is still unclear. The purpose of this systematic review and meta-analysis was to determine the acute effect of endurance training, either continuous or interval training, on circulating irisin in healthy adults.

Methods

Literature search was conducted in Web of Science, PubMed, Scopus and CINAHL until September 2022. Clinical trials measuring irisin levels following a single session of interval or continuous endurance training in healthy adults were eligible. Cohen’s d effect size (95% confidence level), subgroup analyses and univariate meta-regression were calculated using a random-effects model. The procedures described by PRISMA were followed and the protocol was prospectively registered with PROSPERO (CRD 42021240971).

Results

Data of the 16 included studies comprising 412 individuals showed a significant increase following one session of continuous endurance training (d = 0.33, 95% CI: 0.20 to 0.46 , p < 0.001), while interval training did not change circulating irisin (d = 0.16, 95% CI: −0.12 to 0.44 , p = 0.202). Both subgroup and univariate meta-regression analyses showed non-significant differences in the change of circulating irisin comparing blood measurement, exercise mode or previous level of physical activity of the participants and circulating irisin at baseline, duration, or intensity of the exercise, respectively.

Conclusion

Continuous method for endurance training increases circulating irisin in healthy adults, while studies measuring circulating irisin following interval training in healthy adults are still limited to be conclusive.

Irisin/FNDC5 influences myogenic markers on skeletal muscle following high and moderate-intensity exercise training in STZ-diabetic rats

In the present study, we investigated the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on irisin and expression of myogenic markers (paired box 7 (Pax7), myogenic differentiation 1 (MyoD), myogenin) in skeletal muscle of diabetic rats. Eighty-four male Wistar rats (6 weeks of age) were randomly divided into seven groups (n = 12): basic control (Co Basic), 8 weeks control (Co 8w), diabetes mellitus (DM), HIIT, DM + HIIT, MICT, and DM + MICT groups. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). TheV ˙ o 2 max protocol was characterized by running on a rodent treadmill with moderate intensity (60-70%V ˙ o 2 max ), 60 min per session, 5 days/week, for 6 weeks. HIIT consisted of six 3-min runs at a high intensity (80-90%V ˙ o 2 max ) alternated with 2-min running at low intensity (50%V ˙ o 2 max ), 30 min per session, 5 days/week, for 6 weeks. Results showed that DM decreased myoblast markers compared to Co Basic and Co 8w groups. Fibronectin type III domain-containing protein 5 (FNDC5) mRNA decrease was correlated with myoblast markers (Pax7 r = 0.632, p = 0.027; MyoD r = 0.999, p = 0.001; myogenin r = 1.000, p = 0.001) in DM group. DM + MICT significantly increased gene expression of MyoD, myogenin, and FNDC5 compared to DM and DM + HIIT. The results also showed that the intensity and duration of exercise on the treadmill were effective in stimulating irisin and myogenic markers after DM.

Irisin is an Effector Molecule in Exercise Rehabilitation Following Myocardial Infarction (Review)

Background: Regular exercise is an effective non-pharmacological therapy for treatment and prevention of cardiovascular disease (CVD). The therapeutic benefits of exercise are mediated partly through improved vascular and increase in metabolic health. Release of exercise-responsive myokines, including irisin, is associated with beneficial effects of exercise in CVD patients.

Observations: The present review provides an overview of the role of exercise in cardiac rehabilitation of patients with myocardial infarction (MI). Further, the role of irisin as a motion-responsive molecule in improving vascular and metabolic health is explored. Possible mechanism of cardioprotective effect of irisin-mediated exercise on myocardial infarction are also summarized in this review.

Conclusion and significance of the review: Irisin is associated with reduced inflammation, antioxidant properties, and anti-apoptotic effect, implying that it is a potential key mediator of the beneficial effects of exercise on vascular and metabolic health. The findings show that irisin is a promising therapeutic target for treatment of patients with cardiovascular disease, particularly post-MI. Further research should be conducted to elucidate the potential mechanisms of cardioprotective effects of irisin and explored whether irisin induced by exercise exerts rehabilitation effects post-MI.

Exercise training remodels subcutaneous adipose tissue in adults with obesity even without weight loss

Excessive adipose tissue mass underlies much of the metabolic health complications in obesity. Although exercise training is known to improve metabolic health in individuals with obesity, the effects of exercise training without weight loss on adipose tissue structure and metabolic function remain unclear. Thirty-six adults with obesity (body mass index = 33 ± 3 kg · m^-2 ) were assigned to 12 weeks (4 days week^-1 ) of either moderate-intensity continuous training (MICT; 70% maximal heart rate, 45 min; n = 17) or high-intensity interval training (HIIT; 90% maximal heart rate, 10 × 1 min; n = 19), maintaining their body weight throughout. Abdominal subcutaneous adipose tissue (aSAT) biopsy samples were collected once before and twice after training (1 day after last exercise and again 4 days later). Exercise training modified aSAT morphology (i.e. reduced fat cell size, increased collagen type 5a3, both P ≤ 0.05, increased capillary density, P = 0.05) and altered protein abundance of factors that regulate aSAT remodelling (i.e. reduced matrix metallopeptidase 9; P = 0.02; increased angiopoietin-2; P < 0.01). Exercise training also increased protein abundance of factors that regulate lipid metabolism (e.g. hormone sensitive lipase and fatty acid translocase; P ≤ 0.03) and key proteins involved in the mitogen-activated protein kinase pathway when measured the day after the last exercise session. However, most of these exercise-mediated changes were no longer significant 4 days after exercise. Importantly, MICT and HIIT induced remarkably similar adaptations in aSAT. Collectively, even in the absence of weight loss, 12 weeks of exercise training induced changes in aSAT structure, as well as factors that regulate metabolism and the inflammatory signal pathway in adults with obesity. KEY POINTS: Exercise training is well-known to improve metabolic health in obesity, although how exercise modifies the structure and metabolic function of adipose tissue, in the absence of weight loss, remains unclear. We report that both 12 weeks of moderate-intensity continuous training (MICT) and 12 weeks of high-intensity interval training (HIIT) induced modifications in adipose tissue structure and factors that regulate adipose tissue remodelling, metabolism and the inflammatory signal pathway in adults with obesity, even without weight loss (with no meaningful differences between MICT and HIIT). The modest modifications in adipose tissue structure in response to 12 weeks of MICT or HIIT did not lead to changes in the rate of fatty acid release from adipose tissue. These results expand our understanding about the effects of two commonly used exercise training prescriptions (MICT and HIIT) on adipose tissue remodelling that may lead to advanced strategies for improving metabolic health outcomes in adults with obesity.

Biological Response of Irisin Induced by Different Types of Exercise in Obese Subjects: A Non-Inferiority Controlled Randomized Study

Simple Summary

Among healthy male and female obese individuals undergoing a 12-week aerobic exercise program with either moderate intensity endurance or high-intensity interval training for losing weight, a reduction of circulating irisin was observed. Irisin is an important adipo-myokine implicated in the regulation of energy metabolism and cardiovascular health. Sex differences in the circulating levels of this biomarker have been previously reported and are likely related to the different anthropometric features between the sexes. A sex-specific modulation of circulating irisin levels should be further explored to tailor sex-specific training approaches for improving the cardiovascular health of obese subjects.

Abstract

Background: Weight loss through physical exercise is warranted among obese individuals. Recently, a greater benefit in cardiorespiratory fitness was achievable with high-intensity interval training (HIIT) as compared with moderate intensity continuous training. The beneficial effect of training on CV health might be related to a specific modulation of circulating irisin, an adypo-myokine implicated in the regulation of energy expenditure. Methods: The present study investigates the circulating plasma levels of irisin at baseline and in response to 12-week of training program either with HIIT or moderate-intensity continuous training (MICT) among young female and male obese subjects. Clinical, anthropometric, and training characteristics for each participant were available. A sex-disaggregated data for circulating plasma levels of irisin pre- and post-training are provided as well as an adjusted multivariate linear regression model to identify the determinants of post-training irisin levels. Results: Data from a total of 32 obese healthy individuals (47% female, mean age 38.7 years, mean BMI 35.6 kg/m²), randomized in a 1:1 manner to HIIT or MICT were analyzed. Circulating plasma levels of irisin similarly and significantly decreased in both MICT and HIIT interventional groups. Females had higher post-exercise irisin levels than males (6.32 [5.51–6.75] vs. 4.97 [4.57–5.72] μg/mL, p = 0.001). When stratified by an interventional group, a statistically significant difference was observed only for the MICT group (male, 4.76 [4.20–5.45] μg/mL vs. female 6.48 [4.88–6.84] μg/mL p = 0.03). The circulating post-training level of irisin was independently associated with post-training fat-free mass (β −0.34, 95% confidence interval, CI −0.062, −0.006, p = 0.019) in a model adjusted confounders. When female sex was added into the adjusted model, it was retained as the only factor independently associated with irisin levels (β 1.22, 95% CI, 0.50, 1.93, p = 0.002). Conclusions: In obese healthy subjects, circulating irisin levels were reduced in response to 12-weeks of exercise involving either HIIT or MICT. A sex-specific differences in circulating irisin levels at baseline and as biological response to chronic exercise was described. Sex-specific biological response of irisin to exercise should be further explored to tailor sex-specific training approaches for improving the cardiovascular health of obese healthy subjects.

Effects of a Low-Carbohydrate High-Fat Diet Combined with High-Intensity Interval Training on Body Composition and Maximal Oxygen Uptake: A Systematic Review and Meta-Analysis

The low-carbohydrate high-fat (LCHF) diet has recently been subject to attention on account of its reported influences on body composition and physical performance. However, the combined effect of LCHF with high-intensity interval training (HIIT) is unclear. A systematic review and meta-analysis were conducted to explore the effect of the LCHF diet combined with HIIT on human body composition (i.e., body weight (BM), body mass index (BMI), fat mass (FM), body fat percentage (BFP), fat-free mass (FFM)) and maximal oxygen uptake (VO_2max). Online libraries (PubMed, Web of Science, EMBASE, Cochrane Library, EBSCO, CNKI, Wan Fang) were used to search initial studies until July 2021, from which 10 out of 2440 studies were included. WMD served as the effect size with a confidence interval value of 95%. The results of meta-analysis showed a significant reduction in BM (WMD = −5.299; 95% CI: −7.223, −3.376, p = 0.000), BMI (WMD = −1.150; 95% CI: −2.225, −0.075, p = 0.036), BFP (WMD = −2.787; 95% CI: −4.738, −0.835, p = 0.005) and a significant increase in VO_2max (WMD = 3.311; 95% CI: 1.705, 4.918, p = 0.000), while FM (WMD = −2.221; 95% CI: −4.582, 0.139, p = 0.065) and FFM (WMD = 0.487; 95% CI: −3.512, 4.469, p = 0.814) remained unchanged. In conclusion, the LCHF diet combined with HIIT can reduce weight and fat effectively. This combination is sufficient to prevent muscle mass loss during LCHF, and further enhance VO_2max. Further research might be required to clarify the effect of other types of exercise on body composition and physical performance during LCHF.

Effect of high-intensity interval training on cardiometabolic risk factors in childhood obesity: a meta-analysis

INTRODUCTION

This systematic review with meta-analysis aimed to quantify the effectiveness of high-intensity interval training (HIIT) on the cardiometabolic health of obese children and adolescents.

EVIDENCE ACQUISITION

Relevant articles were sourced from PubMed, Embase, the Web of Science, EBSCO, the Cochrane Library and China National Knowledge Infrastructure (CNKI). Randomized controlled trials were included if they employed participants aged 7-19 years. Outcomes included fasting glucose (FG), fasting insulin (FI), homeostasis model assessment-insulin resistance (HOMA-IR), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), triacylglycerol (TG), total cholesterol (TC), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at baseline and postintervention and compared with those in the control group. Data analysis and synthesis were completed by Revman 5.3 software and Stata 12.0 software (StataCorp LLC., College Station, TX, USA).

EVIDENCE SYNTHESIS

Eight trials involving 379 participants were identified. HIIT significantly decreased the FI, HOMA-IR, TC, TG, LDL-c and SBP in participants with obesity. With regard to changes in blood glucose and lipids, participants who underwent HIIT showed great improvement in FI (mean difference: -3.09 µU/mL, 95% confidence interval [CI] -3.71 to -2.46, P<0.0001), HOMA-IR (mean difference: -0.64, 95% CI -0.82 to -0.46, P<0.0001), TG (mean difference: -0.21 mmol/L, 95% CI -0.31 to -0.10, P<0.0001) and LDL-c (mean difference: -0.35 mmol/L, 95% CI -0.48 to -0.22, P<0.001) than the control group. Similar results were found for SBP (mean difference: -3.61 mmHg, 95% CI -5.85 to -1.37, P=0.002). However, no significant differences in changes in FG, HDL-c and DBP were observed between HIIT and control groups.

CONCLUSIONS

HIIT can produce a positive effect on cardiometabolic risk factors in obese children and adolescents. HIIT may be an alternative and effective training method for managing childhood obesity.

Sex-dependent effects of forced exercise in the body composition of adolescent rats

Determining the body composition during adolescence can predict diseases such as obesity, diabetes, and metabolic syndromes later in life; and physical activity became an effective way to restore changes in body composition. However, current available literature assessing the body composition before, during and after adolescence in female and male rodents by in vivo techniques is scarce. Thus, by using computerized tomography, we aimed to define the baseline of the weight and body composition during the adolescence and young adulthood of female and male Sprague-Dawley rats (on P30, P60 and P90) under standard diet. Then, we determined the effect of 18 days of forced exercise on the body weight and composition during the early adolescence (P27-45). The highest percentual increments in weight, body volume and relative adipose contents occurred during the female and male adolescence. Forced running during the early adolescence decreased weight, body volume and relative adipose delta and increment values in males only. The adolescence of rats is a period of drastic body composition changes, where exercise interventions have sex-dependent effects. These results support a model that could open new research windows in the field of adolescent obesity.

Concentrations of Circulating Irisin and Myostatin in Race and Endurace Purebred Arabian Horses-Preliminary Study

Simple Summary

Irisin and myostatin are regulatory proteins produced by muscle cells. The aim of the study was to evaluate the effect of exercise on plasma irisin and myostatin concentrations in horses in different types of training (speed versus endurance). To find out, we tested 20 Arabian horses, submitted to the two different equestrian disciplines, and consequently different training regimes. The first group of horses realized a short-term, high-speed bout of exercise whereas the second group of horses were submitted to long-lasting, endurance effort. The obtained results showed that the single bout of exercise induced an increase in plasma myostatin concentration. Plasma irisin level decreased during the race season in racehorses. This means that irisin and myostatin may play a regulatory role in the maintenance of the energy balance processes.

Abstract

Skeletal muscle is considered to be the largest endocrine organ determining the maintenance of energy homeostasis. Adaptive changes in skeletal muscles in response to physical exercise influence the production as well as secretion of myokines, which are bioactive factors that play a crucial role in energy expenditure processes. The aim of the study was to investigate the impact of two different types of exercise on the circulating level of two of these, myostatin and irisin, in trained horses. Twenty purebred Arabian horses were involved in the study: 10 three-year-old horses trained on the racetrack and 10 endurance horses aged 7.4 ± 1.9 years. The horses from both groups were regularly trained throughout the entire season, during which they also participated in Polish National competitions. To assess the influence of the training sessions on plasma myostatin and irisin concentrations, blood samples taken at rest and 30 min after the end of exercise were analyzed. In the studied horses, the single bout of exercise did not influence plasma irisin but induced an increase in plasma myostatin concentration. In racehorses, plasma irisin concentration decreased with the length of the training season. Plasma myostatin was higher in endurance horses than in three-year-old racehorses. Lack of exercise-induced fluctuation in circulating irisin in studied horses suggests that myostatin released in response to exercise provides a negative feedback signal to irisin release.

Mild-cold water swimming does not exacerbate white adipose tissue browning and brown adipose tissue activation in mice

The present study investigated the effects of swimming physical training either thermoneutral or below thermoneutral water temperature on white (WAT) and brown (BAT) adipose tissue metabolism, morphology, and function. C57BL/6J male mice (n = 40; weight 25.3 ± 0.1 g) were divided into control (CT30), cold control (CT20), trained (TR30), and cold trained (TR20) groups. Swimming training consisted of 30-min exercise at 30°C (control) or 20°C (cold) water temperature. After 8-week training, adipose tissues were excised and inguinal (ingWAT) and BAT were processed for histology, lipolysis, and protein contents of total OXPHOS, PGC1α, and UCP1 by western blotting analysis. Swimming training reduced body weight gain independently of water temperature (P < 0.05). ingWAT mass was decreased for TR30 in comparison to other groups (P < 0.05), while for BAT, there was a significant increase in CT20 in relation to CT30, and both trained groups were significantly increased in relation to control groups (P < 0.05). ingWAT mean adipocyte area was smaller for trained groups, and seemed to present multilocular adipocytes. Lipolytic activity and protein content of UCP1, PGC1α, and mitochondrial markers were increased in trained groups for ingWAT (P < 0.05), independent of water temperature (P > 0.05), and these patterns were not observed for BAT (P > 0.05). Our findings suggest that mild-cold water exposure and swimming physical exercise seem to, independently, promote browning in ingWAT with no effects on BAT; however, the association of exercise and mild-cold water did not exacerbate these effects.

Eccentric resistance training and β-hydroxy-β-methylbutyrate free acid affects muscle PGC-1α expression and serum irisin, nesfatin-1 and resistin in rats

The hypothalamus controls metabolism and feeding behaviour via several signals with other tissues. Exercise and supplements can change hypothalamic signalling pathways, so the present study investigated the influence of eccentric resistance training and β-hydroxy-β-methylbutyrate free acid supplementation on PGC-1α expression, serum irisin, nesfatin-1 and resistin concentrations. Thirty-two male rats (8 weeks old, 200±17 g body mass) were randomly allocated to control, β-hydroxy-β-methylbutyrate free acid supplementation (HMB), eccentric resistance training (ERT), and β-hydroxy-β-methylbutyrate free acid supplementation plus eccentric resistance training (HMB+ERT) groups. Training groups undertook eccentric resistance training (6 weeks, 3 times a week) and supplement groups consumed β-hydroxy-β-methylbutyrate free acid (HMB-FA) orally (76 mg kg^-1 day^-1). Twenty-four hours after the last training session, serum and triceps brachii muscle samples were collected and sent to the laboratory for analysis. Two-way ANOVA and Pearson correlation were employed (significance level: P<0.05). The results showed that eccentric resistance training increases skeletal muscle PGC-1α gene expression, as well as serum levels of irisin and nesfatin-1 (P=0.001). Eccentric resistance training decreased the serum concentration of resistin (P=0.001). HMB-FA supplementation increased skeletal muscle PGC-1α gene expression (P=0.002), as well as the serum concentration of irisin and nesfatin-1 (P=0.001), but decreased the serum concentration of resistin (P=0.001). Significant correlations were observed between PGC-1α gene expression and serum concentrations of irisin, nesfatin-1 and resistin. HMB-FA supplementation with eccentric resistance training may induce crosstalk between peptide release from other tissues and increases maximal muscle strength. The combination of the two interventions had a more substantial effect than each in isolation.

Self-Paced Free-Running Wheel Mimics High-Intensity Interval Training Impact on Rats' Functional, Physiological, Biochemical, and Morphological Features

Free-running wheel (FRW) is an animal exercise model that relies on high-intensity interval moments interspersed with low-intensity or pauses apparently similar to those performed in high-intensity interval training (HIIT). Therefore, this study, conducted over a 12-weeks period, aimed to compare functional, thermographic, biochemical and morphological skeletal and cardiac muscle adaptations induced by FRW and HIIT. Twenty-four male Wistar rats were assigned into three groups: sedentary rats (SED), rats that voluntarily exercise in free wheels (FRW) and rats submitted to a daily HIIT. Functional tests revealed that compared to SED both FRW and HIIT increased the ability to perform maximal workload tests (MWT-cm/s) (45 ± 1 vs. 55 ± 2 and vs. 65 ± 2). Regarding thermographic assays, FRW and HIIT increased the ability to lose heat through the tail during MWT. Histochemical analyzes performed in tibialis anterior (TA) and soleus (SOL) muscles showed a general adaptation toward a more oxidative phenotype in both FRW and HIIT. Exercise increased the percentage of fast oxidative glycolytic (FOG) in medial fields of TA (29.7 ± 2.3 vs. 44.9 ± 4.4 and vs. 45.2 ± 5.3) and slow oxidative (SO) in SOL (73.4 ± 5.7 vs. 99.5 ± 0.5 and vs. 96.4 ± 1.2). HITT decreased fiber cross-sectional area (FCSA-μm²) of SO (4350 ± 286.9 vs. 4893 ± 325 and vs. 3621 ± 237.3) in SOL. Fast glycolytic fibers were bigger across all the TA muscle in FRW and HIIT groups. The FCSA decrease in FOG fibers was accompanied by a circularity decrease of SO from SOL fibers (0.840 ± 0.005 vs. 0.783 ± 0.016 and vs. 0.788 ± 0.010), and a fiber and global field capillarization increase in both FRW and HIIT protocols. Moreover, FRW and HIIT animals exhibited increased cardiac mitochondrial respiratory control ratio with complex I-driven substrates (3.89 ± 0.14 vs. 5.20 ± 0.25 and vs. 5.42 ± 0.37). Data suggest that FRW induces significant functional, physiological, and biochemical adaptations similar to those obtained under an intermittent forced exercise regimen, such as HIIT.

Effect of Exercise on Fatty Acid Metabolism and Adipokine Secretion in Adipose Tissue

Increased physical activity is an optimal way to maintain a good health. During exercise, triacylglycerols, an energy reservoir in adipose tissue, are hydrolyzed to free fatty acids (FAs) which are then released to the circulation, providing a fuel for working muscles. Thus, regular physical activity leads to a reduction of adipose tissue mass and improves metabolism. However, the reduction of lipid reservoir is also associated with many other interesting changes in adipose tissue FA metabolism. For example, a prolonged exercise contributes to a decrease in lipoprotein lipase activity and resultant reduction of FA uptake. This results in the improvement of mitochondrial function and upregulation of enzymes involved in the metabolism of polyunsaturated fatty acids. The exercise-induced changes in adipocyte metabolism are associated with modifications of FA composition. The modifications are adipose tissue depot-specific and follow different patterns in visceral and subcutaneous adipose tissue. Moreover, exercise affects adipokine release from adipose tissue, and thus, may mitigate inflammation and improve insulin sensitivity. Another consequence of exercise is the recently described phenomenon of adipose tissue “beiging,” i.e., a switch from energy-storing white adipocyte phenotype to thermogenic FA oxidizing beige adipocytes. This process is regulated by myokines released during the exercise. In this review, we summarize published evidence for the exercise-related changes in FA metabolism and adipokine release in adipose tissue, and their potential contribution to beneficial cardiovascular and metabolic effects of physical activity.

Myokine-adipokine cross-talk: potential mechanisms for the association between plasma irisin and adipokines and cardiometabolic risk factors in Mexican children with obesity and the metabolic syndrome

BACKGROUND

Adipokines and the myokine irisin, involved in mechanisms associated with obesity and metabolic syndrome (MS), are understudied in the pediatric population.

OBJECTIVE

To investigate the relationship between irisin, and leptin, resistin, adiponectin, adipsin, anthropometric and cardiovascular risk factors in Mexican children.

METHODS

A cross-sample of 126 Mexican children aged 6-12 years old were classified as normal weight (n = 46), obese (n = 40), and MS (n = 40) according to CDC's and Cook's age-modified criteria for obesity and MS. Anthropometric parameters and blood pressure were determined and percentiles calculated for age and gender. Irisin, leptin, adiponectin, adipsin, resistin, triglycerides, glucose, high-density lipoprotein cholesterol (HDL-c) levels, and physical activity were determined. Statistical tests for differences between groups, correlation, and multiple regression analyses were performed.

RESULTS

Irisin plasma levels were significantly lower in the obese (6.08 [4.68-6.65]) and MS groups (6.46 [5.74-7.02]) compared with the normal-weight group (8.05 [7.24-8.94]) (p < 0.001). Irisin levels were not influenced by age or gender, but significant dispersion was observed in obese girls (95% CI median [2.29-6.30]). Leptin, resistin, and adipsin levels were significantly increased in the obese and MS groups. Lean-fat ratio was significantly higher in the NW group. Irisin correlated negatively with leptin (- 0.310), resistin (- 0.389), adipsin (- 0.362), BMI% (-0.472), WC% (- 0.453), BMI z-score (- 0.496), fat free mass (- 0.257), fat percentage (- 0.532), fat mass (- 0.515), triglycerides (- 0.291), the number of cardiometabolic risk factors (- 0.443) (p < 0.001); positively with lean-fat ratio (0.489) and HDL-c (0.328) (p < 0.001) and none with physical activity (p < 0.001). Following stepwise multiple linear regression analysis, the lean-fat ratio was the only determinant of irisin levels (B = 1.168, p < 0.001).

CONCLUSIONS

Lean-fat ratio, more than the absolute amount of muscle or fat mass, as well as potential myokine-adipokine cross-talk mechanisms may explain the lower irisin levels in children with obesity and MS, through blunted compensatory responses interfering with tissue-dependent irisin secretion, contributing to a continuous deleterious effect cycle.

Association between Resistin Gene Polymorphisms and Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, relapsing, and inflammatory skin disorder. It is characterized by an inappropriate skin barrier function, allergen sensitization, and recurrent skin infections. Resistin is an adipokine expressed mainly in macrophages and monocytes; it has a role in the inflammatory process and is associated with multiple inflammatory human diseases; however, only few studies linked resistin to atopic dermatitis. This study tested the association between G>A (rs3745367) and C>T (rs3219177) single nucleotide polymorphisms (SNPs) of the RETN gene with atopic dermatitis. In addition, it explored the relationship between serum resistin protein and atopic dermatitis. To achieve objectives of this study, 162 atopic dermatitis patients and 161 healthy participants were recruited in the study. A significant association was detected between rs3745367 and atopic dermatitis with age and gender specificity (p < 0.05), while no significant association between rs3219177 and atopic dermatitis was found (p > 0.05). For the serum resistin levels, a significant decrease was indicated in atopic dermatitis patients compared to healthy subjects (p < 0.05). In conclusion, rs3745367 may play a gender and age-specific role in atopic dermatitis. In addition, the significant decrease in the resistin protein level confirmed this association.