Role of myokines in the development of skeletal muscle insulin resistance and related metabolic defects in type 2 diabetes

Skeletal muscle cystathionine γ-lyase deficiency promotes obesity and insulin resistance and results in hyperglycemia and skeletal muscle injury upon HFD in mice

OBJECTIVES

The objective of this study was to investigate whether skeletal muscle cystathionine γ-lyase (CTH) contributes to high-fat diet (HFD)-induced metabolic disorders using skeletal muscle Cth knockout (CthΔskm) mice.

METHODS

The CthΔskm mice and littermate Cth-floxed (Cthf/f) mice were fed with either HFD or chow diet for 13 weeks. Metabolomics and transcriptome analysis were used to assess the impact of CTH deficiency in skeletal muscle.

RESULTS

Metabolomics coupled with transcriptome showed that CthΔskm mice displayed impaired energy metabolism and some signaling pathways linked to insulin resistance (IR) in skeletal muscle although the mice had normal insulin sensitivity. HFD led to reduced CTH expression and impaired energy metabolism in skeletal muscle in Cthf/f mice. CTH deficiency and HFD had some common pathways enriched in the aspects of amino acid metabolism, carbon metabolism, and fatty acid metabolism. CthΔskm+HFD mice exhibited increased body weight gain, fasting blood glucose, plasma insulin, and IR, and reduced glucose transporter 4 and CD36 expression in skeletal muscle compared to Cthf/f+HFD mice. Impaired mitochondria and irregular arrangement in myofilament occurred in CthΔskm+HFD mice. Omics analysis showed differential pathways enriched between CthΔskm mice and Cthf/f mice upon HFD. More severity in impaired energy metabolism, reduced AMPK signaling, and increased oxidative stress and ferroptosis occurred in CthΔskm+HFD mice compared to Cthf/f+HFD mice.

DISCUSSION

Our results indicate that skeletal muscle CTH expression dysregulation contributes to metabolism disorders upon HFD.

The multifactorial effect of obesity on the effectiveness and outcomes of cancer therapies

Epidemiology studies have demonstrated a clear association between obesity and the development of several distinct malignancies, with excessive visceral adiposity being an increasingly prevalent feature in patients with cancer presenting for therapeutic intervention. Clinical trials and meta-analyses have helped to inform effective and safe dosing of traditional systemically administered anticancer agents in adult patients with cancer and obesity, but there remains much debate not only regarding the effect of obesity on the more novel targeted molecular and immune-based therapies, but also about how obesity is best defined and measured clinically. Low muscle mass is associated with poor outcomes in cancer, and body composition studies using biochemical and imaging modalities are helping to fully delineate the importance of both obesity and sarcopenia in clinical outcomes; such studies might also go some way to explaining how obesity can paradoxically be associated with favourable clinical outcomes in certain cancers. As the cancer survivorship period increases and the duration of anticancer treatment lengthens, this Review highlights the challenges facing appropriate treatment selection and emphasizes how a multidisciplinary approach is warranted to manage weight and skeletal muscle loss during and after cancer treatment.

Cellular Senescence and Extracellular Vesicles in the Pathogenesis and Treatment of Obesity-A Narrative Review

This narrative review explores the pathophysiology of obesity, cellular senescence, and exosome release. When exposed to excessive nutrients, adipocytes develop mitochondrial dysfunction and generate reactive oxygen species with DNA damage. This triggers adipocyte hypertrophy and hypoxia, inhibition of adiponectin secretion and adipogenesis, increased endoplasmic reticulum stress and maladaptive unfolded protein response, metaflammation, and polarization of macrophages. Such feed-forward cycles are not resolved by antioxidant systems, heat shock response pathways, or DNA repair mechanisms, resulting in transmissible cellular senescence via autocrine, paracrine, and endocrine signaling. Senescence can thus affect preadipocytes, mature adipocytes, tissue macrophages and lymphocytes, hepatocytes, vascular endothelium, pancreatic β cells, myocytes, hypothalamic nuclei, and renal podocytes. The senescence-associated secretory phenotype is closely related to visceral adipose tissue expansion and metaflammation; inhibition of SIRT-1, adiponectin, and autophagy; and increased release of exosomes, exosomal micro-RNAs, pro-inflammatory adipokines, and saturated free fatty acids. The resulting hypernefemia, insulin resistance, and diminished fatty acid β-oxidation lead to lipotoxicity and progressive obesity, metabolic syndrome, and physical and cognitive functional decline. Weight cycling is related to continuing immunosenescence and exposure to palmitate. Cellular senescence, exosome release, and the transmissible senescence-associated secretory phenotype contribute to obesity and metabolic syndrome. Targeted therapies have interrelated and synergistic effects on cellular senescence, obesity, and premature aging.

Slow-velocity eccentric-only resistance training improves symptoms of type 2 diabetic mellitus patients by regulating plasma MMP-2 and -9

OBJECTIVE

This study investigated the intervention effect of slow-velocity eccentric-only resistance training on type 2 diabetic mellitus (T2DM) patients based on the role of matrix metalloproteinase-2 and -9 (MMP-2 and -9) in regulating extracellular matrix homeostasis.

METHODS

50 T2DM patients were randomly divided into the slow-velocity eccentric-only resistance training group (E) and control group (C). The E group performed eccentric-only resistance training 3 times a week, every other day for 10 weeks, while the C group did not. Blood samples were collected before and after training, and subjects were tested for changes in clinical parameters, insulin resistance indices [fasting insulin, homeostatic model assessment insulin resistance (HOMA-IR)], MMP-2 and -9, and hydroxyproline, and muscle strength (12-RM), respectively.

RESULTS

After 10 weeks of training, the E group showed significant decreases in fasting glucose (P < .05), insulin (P < .05), insulin resistance indices (P < .05), hemoglobin A1c (HbA1c) (P < .01), triglycerides (P = .06) and MMP-2 (P < .05), while total cholesterol (P < .05), MMP-9 (P < .05), hydroxyproline (P < .01), Creatine Kinase (CK) (P < .05), and muscle strength (P < .001) significantly increased. There were no significant changes in the count of neutrophil, lymphocyte and platelet, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c). Compared with the C group, the E group showed a trend of a significant decrease in triglyceride (P < .05), lymphocyte count (P < .05), fasting glucose (P = .07), and plasma MMP-2 (P < .05), while MMP-9 (P < .05), hydroxyproline (P < .001), and muscle strength (P < .01) significantly increased. However, no significant changes were observed in insulin and insulin resistance indices, HbA1c, total cholesterol, HDL-c, LDL-c, CK, and other inflammatory indicators.

CONCLUSIONS

Slow-velocity eccentric-only resistance training was beneficial for T2DM, but the potential role of MMP-2 and -9 in regulating extracellular matrix homeostasis is very different in T2DM patients.

Ectopic fat in muscle and poor glycemic control are negatively associated with trabecular bone score in type 2 diabetes

INTRODUCTION

Type 2 Diabetes (T2D) is associated with fractures, despite preserved Bone Mineral Density (BMD). This study aimed to evaluate the relationship between BMD and trabecular bone score (TBS) with the reallocation of fat within muscle in individuals with eutrophy, obesity, and T2D.

METHODS

The subjects were divided into three groups: eutrophic controls paired by age and sex with the T2D group (n = 23), controls diagnosed with obesity paired by age, sex, and body mass index with the T2D group (n = 27), and the T2D group (n = 29). BMD and body fat percentage were determined using dual-energy X-Ray absorptiometry. TBS was determined using TBS iNsight software. Intra and extramyocellular lipids in the soleus were measured using proton magnetic resonance spectroscopy.

RESULTS

TBS was lower in the T2D group than in the other two groups. Glycated hemoglobin (A1c) was negatively associated with TBS. Body fat percentage was negatively associated with TBS and Total Hip (TH) BMD. TH BMD was positively associated with intramuscular lipids. A trend of negative association was observed between intramuscular lipids and TBS.

CONCLUSION

This study showed for the first time that the reallocation of lipids within muscle has a negative association with TBS. Moreover, these results are consistent with previous studies showing a negative association between a parameter related to insulin resistance (intramuscular lipids) and TBS.

Myokine Secretion following an Aerobic Exercise Intervention in Individuals with Type 2 Diabetes with or without Exercise Resistance

Type 2 diabetes (T2D) is characterized by muscle metabolic dysfunction that exercise can minimize, but some patients do not respond to an exercise intervention. Myokine secretion is intrinsically altered in patients with T2D, but the role of myokines in exercise resistance in this patient population has never been studied. We sought to determine if changes in myokine secretion were linked to the response to an exercise intervention in patients with T2D. The participants followed a 10-week aerobic exercise training intervention, and patients with T2D were grouped based on muscle mitochondrial function improvement (responders versus non-responders). We measured myokines in serum and cell-culture medium of myotubes derived from participants pre- and post-intervention and in response to an in vitro model of muscle contraction. We also quantified the expression of genes related to inflammation in the myotubes pre- and post-intervention. No significant differences were detected depending on T2D status or response to exercise in the biological markers measured, with the exception of modest differences in expression patterns for certain myokines (IL-1β, IL-8, IL-10, and IL-15). Further investigation into the molecular mechanisms involving myokines may explain exercise resistance with T2D; however, the role in metabolic adaptations to exercise in T2D requires further investigation.

The effects of 12 weeks of high-intensity interval training and moderate-intensity continuous training on FGF21, irisin, and myostatin in men with type 2 diabetes mellitus

This study investigated the influence of a 12-week high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on irisin, fibroblast growth factor 21 (FGF21), and myostatin (MSTN) among men with type 2 diabetes mellitus (T2DM). Forty-five adult men with T2DM were randomly selected and assigned to receive and perform HIIT (4 × 4 min at 85-95% HRmax with three min of active rest at 50-60% HRmax in between) and MICT (walking/running continuously for 47 min at 60-70% HRmax) three sessions per week for 12 weeks, or to act as a non-exercise control (CON) group. The subjects' blood samples were collected at baseline and 48 hours after the last intervention session. Our research revealed that both interventions resulted in similar decreases in FGF21 and MSTN when compared to the CON (p < .01). However, only the HIIT group showed a significant increase in irisin (p < .01) compared to the CON. Further, improvements in insulin resistance, body composition, and VO2 peak were noted in both intervention groups compared with those of the CON group (p < .01). It seems that while either aerobic exercise strategy could be seen as a therapy for men with T2DM, HIIT had a more advantageous effect on the irisin response.

Soluble Factors Associated with Denervation-induced Skeletal Muscle Atrophy

Skeletal muscle tissue has the critical function of mechanical support protecting the body. In addition, its functions are strongly influenced by the balanced synthesis and degradation processes of structural and regulatory proteins. The inhibition of protein synthesis and/or the activation of catabolism generally determines a pathological state or condition called muscle atrophy, a reduction in muscle mass that results in partial or total loss of function. It has been established that many pathophysiological conditions can cause a decrease in muscle mass. Skeletal muscle innervation involves stable and functional neural interactions with muscles via neuromuscular junctions and is essential for maintaining normal muscle structure and function. Loss of motor innervation induces rapid skeletal muscle fiber degeneration with activation of atrophy-related signaling and subsequent disassembly of sarcomeres, altering normal muscle function. After denervation, an inflammation stage is characterized by the increased expression of pro-inflammatory cytokines that determine muscle atrophy. In this review, we highlighted the impact of some soluble factors on the development of muscle atrophy by denervation.

Sarcopenia and Diabetes: A Detrimental Liaison of Advancing Age

Sarcopenia is an age-related clinical complaint characterized by the progressive deterioration of skeletal muscle mass and strength over time. Type 2 diabetes (T2D) is associated with faster and more relevant skeletal muscle impairment. Both conditions influence each other, leading to negative consequences on glycemic control, cardiovascular risk, general health status, risk of falls, frailty, overall quality of life, and mortality. PubMed/Medline, Scopus, Web of Science, and Google Scholar were searched for research articles, scientific reports, observational studies, clinical trials, narrative and systematic reviews, and meta-analyses to review the evidence on the pathophysiology of di-abetes-induced sarcopenia, its relevance in terms of glucose control and diabetes-related outcomes, and diagnostic and therapeutic challenges. The review comprehensively addresses key elements for the clinical definition and diagnostic criteria of sarcopenia, the pathophysiological correlation be-tween T2D, sarcopenia, and related outcomes, a critical review of the role of antihyperglycemic treatment on skeletal muscle health, and perspectives on the role of specific treatment targeting myokine signaling pathways involved in glucose control and the regulation of skeletal muscle metabolism and trophism. Prompt diagnosis and adequate management, including lifestyle inter-vention, health diet programs, micronutrient supplementation, physical exercise, and pharmaco-logical treatment, are needed to prevent or delay skeletal muscle deterioration in T2D.

Exogenous Ketone Supplementation and Ketogenic Diets for Exercise: Considering the Effect on Skeletal Muscle Metabolism

In recent years, ketogenic diets and ketone supplements have increased in popularity, particularly as a mechanism to improve exercise performance by modifying energetics. Since the skeletal muscle is a major metabolic and locomotory organ, it is important to take it into consideration when considering the effect of a dietary intervention, and the impact of physical activity on the body. The goal of this review is to summarize what is currently known and what still needs to be investigated concerning the relationship between ketone body metabolism and exercise, specifically in the skeletal muscle. Overall, it is clear that increased exposure to ketone bodies in combination with exercise can modify skeletal muscle metabolism, but whether this effect is beneficial or detrimental remains unclear and needs to be further interrogated before ketogenic diets or exogenous ketone supplementation can be recommended.

Association Between Handgrip Strength and Type 2 Diabetes: A Prospective Cohort Study and Systematic Review With Meta-analysis

BACKGROUND

Both absolute (kg) and relative (kg per kg of body weight) handgrip strength (HGS) have been used as indicators of HGS. Multiple studies have explored HGS associations with type 2 diabetes (T2DM); however, prognostic values were inconsistent. We aimed to examine the associations between both absolute and relative HGS and incident T2DM.

METHODS

A total of 12,957 participants aged 40 years and older (mean age 51.0 years, 58.4% men) were followed and enrolled in the Tianjin Chronic Low-grade Systemic Inflammation and Health (TCLSIH) Cohort Study. Cox proportional hazards regression models were used to examine the association of HGS with incident T2DM. Other prospective studies on HGS and risk of T2DM were identified by searching several electronic databases up to November 31, 2021. Meta-analysis was performed by combining the results from the TCLSIH study and previous prospective cohort studies.

RESULTS

From the TCLSIH Cohort study, after adjustment, relative HGS was inversely associated with T2DM (hazard ratio per 0.1 higher relative HGS 0.667, 95% confidence interval [CI] 0.616, 0.722). However, no significant association between absolute HGS and incident T2DM was found. The meta-analyses showed that per 5 kg higher HGS was associated with a 5% (95% CI 2%, 8%) lower risk of T2DM and each 0.1 higher relative HGS was associated with a 22% (95% CI 14%, 29%) lower risk of T2DM.

CONCLUSION

The results from our cohort study and meta-analysis suggest that relative HGS was better than absolute HGS in predicting incident T2DM. Adiposity was an important factor that mediates the association between HGS and T2DM.

The role of Huidouba in regulating skeletal muscle metabolic disorders in prediabetic mice through AMPK/PGC-1α/PPARα pathway

Prediabetes is a transitional state between normal blood glucose levels and diabetes, but it is also a reversible process. At the same time, as one of the most important tissues in the human body, the metabolic disorder of skeletal muscle is closely related to prediabetes. Huidouba (HDB) is a clinically proven traditional Chinese medicine with significant effects in regulating disorders of glucose and lipid metabolism. Our study aimed to investigate the efficacy and mechanism of HDB in prediabetic model mice from the perspective of skeletal muscle. C57BL/6J mice (6 weeks old) were fed a high-fat diet (HFD) for 12 weeks to replicate the prediabetic model. Three concentrations of HDB were treated with metformin as a positive control. After administration, fasting blood glucose was measured as an indicator of glucose metabolism, as well as lipid metabolism indicators such as total triglyceride (TG), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), free fatty acid (FFA), and lactate dehydrogenase (LDH). Muscle fat accumulation and glycogen accumulation were observed. The protein expression levels of p-AMPK, AMPK, PGC-1α, PPAR-α, and GLUT-4 were detected. After HDB treatment, fasting blood glucose was significantly improved, and TG, LDL-C, FFA, and LDH in serum and lipid accumulation in muscle tissue were significantly reduced. In addition, HDB significantly upregulated the expression levels of p-AMPK/AMPK, PGC-1α, PPAR-α, and GLUT-4 in muscle tissue. In conclusion, HDB can alleviate the symptoms of prediabetic model mice by promoting the AMPK/PGC-1α/PPARα pathway and upregulating the expression of GLUT-4 protein.

The Muscle-Conditioned Medium Containing Protocatechuic Acid Improves Insulin Resistance by Modulating Muscle Communication with Liver and Adipose Tissue

Diabetes mellitus is a public health concern, affecting 10.5% of the population. Protocatechuic acid (PCA), a polyphenol, exerts beneficial effects on insulin resistance and diabetes. This study investigated the role of PCA in improving insulin resistance and the crosstalk between muscle with liver and adipose tissue. C2C12 myotubes received four treatments: Control, PCA, insulin resistance (IR), and IR-PCA. Conditioned media from C2C12 was used to incubate HepG2 and 3T3-L1 adipocytes. The impact of PCA was analyzed on glucose uptake and signaling pathways. PCA (80 µM) significantly enhanced glucose uptake in C2C12, HepG2, and 3T3-L1 adipocytes (p < 0.05). In C2C12, PCA significantly elevated GLUT-4, IRS-1, IRS-2, PPAR-γ, P-AMPK, and P-Akt vs. Control (p ≤ 0.05), and modulated pathways in IR-PCA. In HepG2, PPAR-γ and P-Akt increased significantly in Control (CM) vs. No CM, and PCA dose upregulated PPAR-γ, P-AMPK, and P-AKT (p < 0.05). In the 3T3-L1 adipocytes, PI3K and GLUT-4 expression was elevated in PCA (CM) vs. No CM. A significant elevation of IRS-1, GLUT-4, and P-AMPK was observed in IR-PCA vs. IR (p ≤ 0.001). Herein, PCA strengthens insulin signaling by activating key proteins of that pathway and regulating glucose uptake. Further, conditioned media modulated crosstalk between muscle with liver and adipose tissue, thus regulating glucose metabolism.

Skeletal muscle and intermuscular adipose tissue gene expression profiling identifies new biomarkers with prognostic significance for insulin resistance progression and intervention response

AIMS/HYPOTHESIS

Although insulin resistance often leads to type 2 diabetes mellitus, its early stages are often unrecognised, thus reducing the probability of successful prevention and intervention. Moreover, treatment efficacy is affected by the genetics of the individual. We used gene expression profiles from a cross-sectional study to identify potential candidate genes for the prediction of diabetes risk and intervention response.

METHODS

Using a multivariate regression model, we linked gene expression profiles of human skeletal muscle and intermuscular adipose tissue (IMAT) to fasting glucose levels and glucose infusion rate. Based on the expression patterns of the top predictive genes, we characterised and compared individual gene expression with clinical classifications using k-nearest neighbour clustering. The predictive potential of the candidate genes identified was validated using muscle gene expression data from a longitudinal intervention study.

RESULTS

We found that genes with a strong association with clinical measures clustered into three distinct expression patterns. Their predictive values for insulin resistance varied substantially between skeletal muscle and IMAT. Moreover, we discovered that individual gene expression-based classifications may differ from classifications based predominantly on clinical variables, indicating that participant stratification may be imprecise if only clinical variables are used for classification. Of the 15 top candidate genes, ST3GAL2, AASS, ARF1 and the transcription factor SIN3A are novel candidates for predicting a refined diabetes risk and intervention response.

CONCLUSION/INTERPRETATION

Our results confirm that disease progression and successful intervention depend on individual gene expression states. We anticipate that our findings may lead to a better understanding and prediction of individual diabetes risk and may help to develop individualised intervention strategies.

Assessment of the dual role of Lyonia ovalifolia (Wall.) Drude in inhibiting AGEs and enhancing GLUT4 translocation through LC-ESI-QTOF-MS/MS determination and in silico studies

Introduction: Diabetes mellitus (DM) is a metabolic disorder that results in glucose accumulation in the blood, accompanied by the production of advanced glycation end products (AGEs) through glycation of cellular proteins. These AGEs interfere with insulin signaling and prevent GLUT4 membrane translocation, thereby promoting the accumulation of more glucose in the blood and causing post-diabetic complications.

Methods: In this study, we examine the anti-diabetic potential of Lyonia ovalifolia (Wall.) Drude, a well-known ethnomedicinal plant of the Indian Himalayas. Considering its various medicinal properties, we analyzed its ethanolic extract and various solvent fractions for in vitro antiglycation activity and antidiabetic potential, i.e., stimulation of GLUT4 translocation.

Result and Discussions: The results showed that the extract and fractions exhibited increased antiglycation activity and an increased level of GLUT4 translocation. Analysis of a further 12 bioactive compounds of ethanolic extract, identified through LC-ESI-QTOF-MS/MS, revealed the presence of three new compounds: leucothol B, rhodoterpenoids A, and leucothol A. Moreover, we performed molecular docking of identified compounds against key proteins of diabetes mellitus: the sirtuin family of NAD (+)-dependent protein deacetylases 6 (SIRT6), aldose reductase (AR), and tyrosine kinase (TK). The results showed that flavonoid luteolin showed the best binding affinity ((−12.3 kcal/mol), followed by eriodictyol, astilbin, and syringaresinol. An ADMET study showed that luteolin, eriodictyol, astilbin, and syringaresinol may be promising drug candidates belonging to the flavonoid class of compounds, with no harmful effects and complying with all the drug-likeness guidelines. Furthermore, molecular dynamics (MD) simulations on a 50 ns timescale revealed that AR protein was most stable with luteolin throughout the simulation period. Therefore, this study reveals for the first time that L. ovalifolia plays an important role in insulin homeostasis, as shown in in vitro and in silico studies.

The Emerging Importance of Cirsimaritin in Type 2 Diabetes Treatment

Cirsimaritin is a dimethoxy flavon that has different biological activities such as antiproliferative, antimicrobial, and antioxidant activities. This study aims to investigate the anti-diabetic effects of cirsimaritin in a high-fat diet and streptozotocin-(HFD/STZ)-induced rat model of type 2 diabetes mellitus (T2D). Rats were fed HFD, followed by a single low dose of STZ (40 mg/kg). HFD/STZ diabetic rats were treated orally with cirsimaritin (50 mg/kg) or metformin (200 mg/kg) for 10 days before terminating the experiment and collecting plasma, soleus muscle, adipose tissue, and liver for further downstream analysis. Cirsimaritin reduced the elevated levels of serum glucose in diabetic rats compared to the vehicle control group (p < 0.001). Cirsimaritin abrogated the increase in serum insulin in the treated diabetic group compared to the vehicle control rats (p < 0.01). The homeostasis model assessment of insulin resistance (HOMA-IR) was decreased in the diabetic rats treated with cirsimaritin compared to the vehicle controls. The skeletal muscle and adipose tissue protein contents of GLUT4 (p < 0.01 and p < 0.05, respectively) and pAMPK-α1 (p < 0.05) were upregulated following treatment with cirsimaritin. Cirsimaritin was able to upregulate GLUT2 and AMPK protein expression in the liver (p < 0.01, <0.05, respectively). LDL, triglyceride, and cholesterol were reduced in diabetic rats treated with cirsimaritin compared to the vehicle controls (p < 0.001). Cirsimaritin reduced MDA, and IL-6 levels (p < 0.001), increased GSH levels (p < 0.001), and reduced GSSG levels (p < 0.001) in diabetic rats compared to the vehicle control. Cirsimaritin could represent a promising therapeutic agent to treat T2D.

Root-Extracted lignanamides from Limonium gmelinii (Willd.) Kuntze with a potential PTP1B inhibitory activity by regulating PI3K/AKT signaling pathway

The phytochemical study of Limonium gmelinii roots resulted in the isolation of five lignanamides (1-5). Among them, limoniumins J, K, and M (1, 2, and 4) are undescribed compounds, limoniumin L (3) is a new naturally occurring lignanamide, and limoniumin B (5) is a known compound which showed PTP1B inhibition activity with an IC₅₀ value of 5.05 ± 2.44 μM in our previous work. Spectroscopic data analysis, including 1D and 2D NMR and HRESIMS experiments, established the chemical structures of limoniumins J - M (1-4). Compounds 1-4 showed PTP1B inhibition activity, among which compound 3 showed the most potent PTP1B inhibition with an IC₅₀ value of 2.07 ± 0.05 μM. Compounds 3 and 5 could significantly increase cellular glucose consumption and glucose uptake in L6 muscle cells and could synergize with insulin to promote glucose consumption and glucose uptake in a concentration-dependent manner. The treatment of compound 3 also promoted glycogen synthesis in skeletal muscle cells. Western blot analysis demonstrated that the good hypoglycemic effect of compounds 3 and 5 was achieved by activating PI3K/AKT signaling pathway to promote glucose consumption, glucose uptake, and glycogen synthesis. Furthermore, studies on molecular docking revealed the potent interactions between these bioactive substances and the PTP1B protein.

Exercise training reduces circulating cytokines in male patients with coronary artery disease and type 2 diabetes: A pilot study

Low-grade inflammation is central to coronary artery disease (CAD) and type 2 diabetes (T2D) and is reduced by exercise training. The objective of this study was to compare the anti-inflammatory potential of moderate-to-vigorous intensity continuous training (MICT) and high-intensity interval training (HIIT) in patients with CAD with or without T2D. The design and setting of this study is based on a secondary analysis of registered randomized clinical trial NCT02765568. Male patients with CAD were randomly assigned to either MICT or HIIT, with subgroups divided according to T2D status (non-T2D-HIIT n = 14 and non-T2D-MICT n = 13; T2D-HIIT n = 6 and T2D-MICT n = 5). The intervention was a 12-week cardiovascular rehabilitation program consisting of either MICT or HIIT (twice weekly sessions) and circulating cytokines measured pre- and post-training as inflammatory markers. The co-occurrence of CAD and T2D was associated with increased plasma IL-8 (p = 0.0331). There was an interaction between T2D and the effect of the training interventions on plasma FGF21 (p = 0.0368) and IL-6 (p = 0.0385), which were further reduced in the T2D groups. An interaction between T2D, training modalities, and the effect of time (p = 0.0415) was detected for SPARC, with HIIT increasing circulating concentrations in the control group, while lowering them in the T2D group, and the inverse occurring with MICT. The interventions also reduced plasma FGF21 (p = 0.0030), IL-6 (p = 0.0101), IL-8 (p = 0.0087), IL-10 (p < 0.0001), and IL-18 (p = 0.0009) irrespective of training modality or T2D status. HIIT and MICT resulted in similar reductions in circulating cytokines known to be increased in the context of low-grade inflammation in CAD patients, an effect more pronounced in patients with T2D for FGF21 and IL-6.

Handgrip strength is inversely associated with augmentation index in patients with type 2 diabetes

Handgrip strength (HGS) is a measure of overall skeletal muscle strength and is used to identify risks for cardiovascular disease and mortality. Furthermore, HGS is an indicator of arterial stiffness that leads to atherosclerotic cardiovascular disease. This study aimed to examine the relationship between HGS and augmentation index (AIx) in patients with type 2 diabetes. A cross-sectional study was conducted to examine patients with type 2 diabetes whose HGS and AIx were measured in our hospital. AIx was measured noninvasively using an applanation tonometer, and multiple regression analyses were conducted to assess the independent relationship between HGS and AIx. This study included 404 patients. After adjusting for age, gender, body mass index, duration of diabetes, smoking and exercise habit, biochemical parameters, and physiological parameters related to arterial stiffness, HGS was found to be independently and inversely associated with AIx (β = - 0.270, p = 0.006). HGS was independently and inversely associated with AIx in patients with type 2 diabetes. Patients with diminished HGS should be subjected to intensive exercise therapy for reducing the risk of arterial stiffness and cardiovascular disease.Trial registration: UMIN000023010.

Combined effects of exercise and different levels of acute hypoxic severity: A randomized crossover study on glucose regulation in adults with overweight

Purpose: The aim of this study was to investigate the influence of manipulating hypoxic severity with low-intensity exercise on glucose regulation in healthy overweight adults. Methods: In a randomized crossover design, 14 males with overweight (age: 27 ± 5 years; body mass index (BMI) 27.1 ± 1.8 kg⋅m²) completed three exercise trials involving 60 min aerobic exercise cycling at 90% lactate threshold in normoxia (NM, FiO₂ = 20.9%), moderate hypoxia (MH, FiO₂ = 16.5%) and high hypoxia (HH, FiO₂ = 14.8%). A post-exercise oral glucose tolerance test (OGTT) was performed. Venous blood samples were analyzed for incremental area under the curve (iAUC), plasma glucose and insulin, as well as exerkine concentrations (plasma apelin and fibroblast growth factor 21 [FGF-21]) pre- and post-exercise. A 24-h continuous glucose monitoring (CGM) was used to determine interstitial glucose concentrations. Heart rate, oxygen saturation (SpO₂) and perceptual measures were recorded during exercise. Results: Post-exercise OGTT iAUC for plasma glucose and insulin concentrations were lower in MH vs. control (p = 0.02). Post-exercise interstitial glucose iAUC, plasma apelin and FGF-21 were not different between conditions. Heart rate was higher in HH vs. NM and MH, and MH vs. NM (p < 0.001), while SpO₂ was lower in HH vs. NM and MH, and MH vs. NM (p < 0.001). Overall perceived discomfort and leg discomfort were higher in HH vs. NM and MH (p < 0.05), while perceived breathing difficulty was higher in HH vs. NM only (p = 0.003). Conclusion: Compared to higher hypoxic conditions, performing acute aerobic-based exercise under moderate hypoxia provided a more effective stimulus for improving post-exercise glucose regulation while concomitantly preventing excessive physiological and perceptual stress in healthy overweight adults.

Upregulation of IL-8, osteonectin, and myonectin mRNAs by intermittent hypoxia via OCT1- and NRF2-mediated mechanisms in skeletal muscle cells

Sleep apnoea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]) and is a risk factor for insulin resistance/Type 2 diabetes. The induction of insulin resistance in skeletal muscle is a key phenomenon to develop diabetes. However, the mechanisms linking IH stress and insulin resistance remain elusive. We exposed human RD and mouse C2C12 muscle cells to normoxia or IH and measured their mRNA levels by real-time RT-PCR. We found that IH significantly increased the mRNA and protein levels of muscle-derived insulin resistance-factors (myokines) such as IL-8, osteonectin (ON), and myonectin (MN) in muscle cells. We further analysed the IH-induced expression mechanisms of IL-8, ON, and MN genes in muscle cells. Deletion analyses of the human myokine promoter(s) revealed that the regions -152 to -151 in IL-8, -105 to -99 in ON, and - 3741 to -3738 in MN promoters were responsible for the activation by IH in RD cells. The promoters contain consensus transcription factor binding sequences for OCT1 in IL-8 and MN promoters, and for NRF2 in ON promoter, respectively. The introduction of siRNA for OCT1 abolished the IH-induced expression(s) of IL-8 and MN and siRNA for NRF2 abolished the IH-induced expression of ON.

The bidirectional relationship between AMPK pathway activation and myokine secretion in skeletal muscle: How it affects energy metabolism

Myokines are peptides and proteins secreted by skeletal muscle cells, into the interstitium, or in the blood. Their regulation may be dependent or independent of muscle contraction to induce a variety of metabolic effects. Numerous myokines have been implicated in influencing energy metabolism via AMP-activated protein kinase (AMPK) signalling. As AMPK is centrally involved in glucose and lipid metabolism, it is important to understand how myokines influence its signalling, and vice versa. Such insight will better elucidate the mechanism of metabolic regulation during exercise and at rest. This review encompasses the latest research conducted on the relationship between AMPK signalling and myokines within skeletal muscles via autocrine or paracrine signalling.

Interleukin-15 are associated with insulin resistance in postmenopausal women with metabolic syndrome

OBJECTIVE

To determine if higher levels of circulating interleukin (IL)-15 are positively associated with improvement in insulin resistance in postmenopausal women (PW) with metabolic syndrome (MS).

METHODS

According to the median value of IL-15 at baseline, PW older than or equal to 45 years were divided into two groups: higher (n = 43) and lower (n = 42) IL-15. There was a 9-month follow-up period with clinical assessments at baseline and at 9 months (criteria of metabolic syndrome, body fat, and insulin resistance). Insulin resistance (IR) was calculated according to the Homeostasis Model Assessment-estimated insulin resistance (HOMA-IR). For IL-1β, IL-6, IL-10, IL-13, IL-33, IL-15, and TNF-α was determined using immunoassay Magnetic Bead Panel.

RESULTS

There was an interaction between the time and group only for insulin (p = .008) and HOMA-IR (p = .024). After adjusting for confounding variables (clinical and ILs), the HOMA-IR (p = .006) and insulin (p = .003) were lower in the higher-IL-15 group [HOMA-IR: 2.2 (95% CI: 1.9-2.5) and insulin: 9.1 µIU/mL (95% CI: 7.9-10.3)] when compared to the lower-IL-15 group [HOMA-IR: 3.1 (95% CI: 2.6-3.6) and insulin: 12.9 (95% CI: 11.1-14.9)] after 9 months of follow-up.

CONCLUSION

Higher levels of circulating IL-15 are positively associated with improvements in IR in PW with MS.

Zi Shen Wan Fang regulates kynurenine metabolism to alleviate diabetes-associated cognitive impairment via activating the skeletal muscle PGC1α-PPARα signaling

BACKGROUND

Cognitive dysfunction is commonly observed in diabetic patients, yet, the underlying mechanisms are obscure and there are no approved drugs. Skeletal muscle is a key pathological organ in diabetes. Evidence is accumulating that skeletal muscle and brain communication are important for cognitive, and kynurenine (KYN) metabolism is one of the mediators.

PURPOSE

This study aims to elucidate the mechanism of diabetes-induced cognitive impairment (DCI) from the perspective of skeletal muscle and brain communication, and to explore the therapeutic effect of Zi Shen Wan Fang (ZSWF, a optimized prescription consists of Anemarrhenae Rhizoma (Anemarrhena asphodeloides Bge.), Phellodendri Chinensis Cortex (Phellodendron chinense Schneid.) and Cistanches Herba (Cistanche deserticola Y.C.Ma)), in order to provide new strategies for the prevention and treatment of DCI and preliminarily explore valuable drugs.

METHODS

DCI was induced by intraperitoneal injection of streptozotocin (STZ) combined with a high-fat diet and treated with different dosage ZSWF extract by oral gavage for 8 weeks, once a day. Cognitive and skeletal muscle function was assessed, synaptic plasticity and L-type amino acid transporter (LAT1) was measured. KYN and its metabolites as well as metabolic enzymes in the hippocampus, peripheral blood and skeletal muscle were measured. Peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) and peroxisome proliferator-activated receptor α (PPARα) were measured in skeletal muscle.

RESULTS

Compared with healthy mice, DCI mice not only showed decreased cognitive function and abnormal skeletal muscle function, but also showed imbalance of KYN metabolism in brain, circulating blood and skeletal muscle. Fortunately, ZSWF administration for 8 weeks notably attenuated the cognitive function, synaptic plasticity and skeletal muscle function in DCI mice. Besides, ZSWF significantly attenuated KYN metabolism in brain, circulation and skeletal muscle of DCI mice. Furthermore, ZSWF activated PGC1α-PPARα in skeletal muscle of DCI mice.

CONCLUSIONS

These results indicate that abnormal PGC1α-PPARα signaling in skeletal muscle mediating KYN metabolism disorder is one of the pathological mechanisms of DCI, and ZSWF can reverse diabetes-induced cognitive impairment via activating skeletal muscle PGC1α-PPARα signaling to maintain KYN metabolism homeostasis.

Mechanisms by Which Skeletal Muscle Myokines Ameliorate Insulin Resistance

The skeletal muscle is the largest organ in the body and secretes circulating factors, including myokines, which are involved in various cellular signaling processes. Skeletal muscle is vital for metabolism and physiology and plays a crucial role in insulin-mediated glucose disposal. Myokines have autocrine, paracrine, and endocrine functions, serving as critical regulators of myogenic differentiation, fiber-type switching, and maintaining muscle mass. Myokines have profound effects on energy metabolism and inflammation, contributing to the pathophysiology of type 2 diabetes (T2D) and other metabolic diseases. Myokines have been shown to increase insulin sensitivity, thereby improving glucose disposal and regulating glucose and lipid metabolism. Many myokines have now been identified, and research on myokine signaling mechanisms and functions is rapidly emerging. This review summarizes the current state of the field regarding the role of myokines in tissue cross-talk, including their molecular mechanisms, and their potential as therapeutic targets for T2D.

MiR-208b Regulates the Conversion of Skeletal Muscle Fiber Types by Inhibiting Mettl8 Expression

Skeletal muscle, the main source of animal meat products, contains muscle fiber as a key unit. It is well known that transformation takes place between different types of muscle fibers, however, the conversion mechanism is not clear. In a previous study, our lab has demonstrated that there is a decrease in type I muscle fibers and an increase in type IIB muscle fibers in skeletal muscle of myostatin gene-edited Meishan pigs. Very interestingly, we observed the down regulation of miR-208b expression and an increase in expression the predicted target gene Mettl8 (Methyltransferase like 8) in skeletal muscle of MSTN gene-edited Meishan pigs. These results reveal that there is a potential connection between the conversion of skeletal muscle fiber types and miR-208b and Mettl8 expression. In this study, we first explored the expression patterns of miR-208b and Mettl8 in skeletal muscle in Meishan pigs; and then C2C12 cells were used to simulate the development and maturation of muscle fibers. Our results indicated that Myh4 expression level decreased and Myh7 expression level increased following overexpression of miR-208b in C2C12 cells. We therefore speculate that miR-208b can promote the conversion of fast-twitch fibers to slow-twitch fibers. The targeting relationship between Mettl8 and miR-208b was confirmed by results obtained using dual luciferase assay, RT-qPCR, and WB analysis. Following the transfection of Mettl8 siRNA into C2C12 cells, we observed that Mettl8 expression decreased significantly while Myh7 expression increased and Myh4 expression decreased, indicating that Mettl8 promotes the conversion of slow muscle fibers to fast muscle fibers. Additionally, changes in skeletal muscle fiber types are observed in those mice where miR-208b and Mettl8 genes are knocked out. The miR-208b knockout inhibits the formation of slow muscle fibers, and the Mettl8 knockout inhibits the formation of fast muscle fibers. In conclusion, our research results show that miR-208b regulates the conversion of different muscle fiber types by inhibiting Mettl8 expression.

Exercise Therapy for People With Sarcopenic Obesity: Myokines and Adipokines as Effective Actors

Sarcopenic obesity is defined as a multifactorial disease in aging with decreased body muscle, decreased muscle strength, decreased independence, increased fat mass, due to decreased physical activity, changes in adipokines and myokines, and decreased satellite cells. People with sarcopenic obesity cause harmful changes in myokines and adipokines. These changes are due to a decrease interleukin-10 (IL-10), interleukin-15 (IL-15), insulin-like growth factor hormone (IGF-1), irisin, leukemia inhibitory factor (LIF), fibroblast growth factor-21 (FGF-21), adiponectin, and apelin. While factors such as myostatin, leptin, interleukin-6 (IL-6), interleukin-8 (IL-8), and resistin increase. The consequences of these changes are an increase in inflammatory factors, increased degradation of muscle proteins, increased fat mass, and decreased muscle tissue, which exacerbates sarcopenia obesity. In contrast, exercise, especially strength training, reverses this process, which includes increasing muscle protein synthesis, increasing myogenesis, increasing mitochondrial biogenesis, increasing brown fat, reducing white fat, reducing inflammatory factors, and reducing muscle atrophy. Since some people with chronic diseases are not able to do high-intensity strength training, exercises with blood flow restriction (BFR) are newly recommended. Numerous studies have shown that low-intensity BFR training produces the same increase in hypertrophy and muscle strength such as high-intensity strength training. Therefore, it seems that exercise interventions with BFR can be an effective way to prevent the exacerbation of sarcopenia obesity. However, due to limited studies on adipokines and exercises with BFR in people with sarcopenic obesity, more research is needed.

Effects of Intermittent Hypoxia on Cytokine Expression Involved in Insulin Resistance

Sleep apnea syndrome (SAS) is a prevalent disorder characterized by recurrent apnea or hypoxia episodes leading to intermittent hypoxia (IH) and arousals during sleep. Currently, the relationship between SAS and metabolic diseases is being actively analyzed, and SAS is considered to be an independent risk factor for the development and progression of insulin resistance/type 2 diabetes (T2DM). Accumulating evidence suggests that the short cycles of decreased oxygen saturation and rapid reoxygenation, a typical feature of SAS, contribute to the development of glucose intolerance and insulin resistance. In addition to IH, several pathological conditions may also contribute to insulin resistance, including sympathetic nervous system hyperactivity, oxidative stress, vascular endothelial dysfunction, and the activation of inflammatory cytokines. However, the detailed mechanism by which IH induces insulin resistance in SAS patients has not been fully revealed. We have previously reported that IH stress may exacerbate insulin resistance/T2DM, especially in hepatocytes, adipocytes, and skeletal muscle cells, by causing abnormal cytokine expression/secretion from each cell. Adipose tissues, skeletal muscle, and the liver are the main endocrine organs producing hepatokines, adipokines, and myokines, respectively. In this review, we focus on the effect of IH on hepatokine, adipokine, and myokine expression.

Obesity phenotypes are, in part, associated with physical activity in diabetic hemodialysis patients

PURPOSE

To investigate the prevalence of obesity phenotypes and their association with physical activity levels among diabetic hemodialysis patients.

METHODS

This is a cross-sectional study with 84 diabetic hemodialysis patients (63.5 ± 9.4 years, 54.8% of men). Obesity was diagnosed as high body fat (≥ 40% for male and ≥ 30% for female). Sarcopenic obesity was considered if low skeletal muscle mass (< 20.0 kg for males and < 15.0 kg for females) and obesity were combined. Dynapenic obesity was defined in the presence of low handgrip strength (< 27 kg for males and < 16 kg for females) and obesity. Muscle failure obesity was confirmed in the concomitant presence of obesity, sarcopenia, and dynapenia. Physical activity level was assessed by the Baecke questionnaire and patients were classified as low physical activity according to the first tertile for each of and total domains.

RESULTS

Fifty-four patients (64%) presented obesity. From these, 5 (6%), 19 (23%) and 8 (10%) were classified as sarcopenic obese, dynapenic obese, and muscle failure obese, respectively, and 22 (26%) were only obese. Patients with sarcopenic obesity and muscle failure obesity had lower leisure and locomotion physical activity scores than non-obese, whereas the total domain score did not differ across the groups. Muscle failure obesity was independently associated with low leisure physical activity (OR 10.8, 95% CI 1.3-88.1). Only sarcopenic obesity was independently associated with the locomotion and total physical activity domains (OR 15.4, 95% CI 1.4-90.2 and OR 17.0, 95% CI 1.5-95.4, respectively).

CONCLUSION

Our study found a lower prevalence of sarcopenic obesity compared to dynapenic obesity and muscle failure obesity among diabetic hemodialysis patients. Moreover, sarcopenic obesity and muscle failure obesity, but not dynapenic obesity, were associated with low physical activity levels.

Rooibos Flavonoids, Aspalathin, Isoorientin, and Orientin Ameliorate Antimycin A-Induced Mitochondrial Dysfunction by Improving Mitochondrial Bioenergetics in Cultured Skeletal Muscle Cells

The current study investigated the physiological effects of flavonoids found in daily consumed rooibos tea, aspalathin, isoorientin, and orientin on improving processes involved in mitochondrial function in C2C12 myotubes. To achieve this, C2C12 myotubes were exposed to a mitochondrial channel blocker, antimycin A (6.25 µM), for 12 h to induce mitochondrial dysfunction. Thereafter, cells were treated with aspalathin, isoorientin, and orientin (10 µM) for 4 h, while metformin (1 µM) and insulin (1 µM) were used as comparators. Relevant bioassays and real-time PCR were conducted to assess the impact of treatment compounds on some markers of mitochondrial function. Our results showed that antimycin A induced alterations in the mitochondrial respiration process and mRNA levels of genes involved in energy production. In fact, aspalathin, isoorientin, and orientin reversed such effects leading to the reduced production of intracellular reactive oxygen species. These flavonoids further enhanced the expression of genes involved in mitochondrial function, such as Ucp 2, Complex 1/3, Sirt 1, Nrf 1, and Tfam. Overall, the current study showed that dietary flavonoids, aspalathin, isoorientin, and orientin, have the potential to be as effective as established pharmacological drugs such as metformin and insulin in protecting against mitochondrial dysfunction in a preclinical setting; however, such information should be confirmed in well-established in vivo disease models.

Activation of the NLRP3 Inflammasome Increases the IL-1β Level and Decreases GLUT4 Translocation in Skeletal Muscle during Insulin Resistance

Low-grade chronic inflammation plays a pivotal role in the pathogenesis of insulin resistance (IR), and skeletal muscle has a central role in this condition. NLRP3 inflammasome activation pathways promote low-grade chronic inflammation in several tissues. However, a direct link between IR and NLRP3 inflammasome activation in skeletal muscle has not been reported. Here, we evaluated the NLRP3 inflammasome components and their role in GLUT4 translocation impairment in skeletal muscle during IR. Male C57BL/6J mice were fed with a normal control diet (NCD) or high-fat diet (HFD) for 8 weeks. The protein levels of NLRP3, ASC, caspase-1, gasdermin-D (GSDMD), and interleukin (IL)-1β were measured in both homogenized and isolated fibers from the flexor digitorum brevis (FDB) or soleus muscle. GLUT4 translocation was determined through GLUT4myc-eGFP electroporation of the FBD muscle. Our results, obtained using immunofluorescence, showed that adult skeletal muscle expresses the inflammasome components. In the FDB and soleus muscles, homogenates from HFD-fed mice, we found increased protein levels of NLRP3 and ASC, higher activation of caspase-1, and elevated IL-1β in its mature form, compared to NCD-fed mice. Moreover, GSDMD, a protein that mediates IL-1β secretion, was found to be increased in HFD-fed-mice muscles. Interestingly, MCC950, a specific pharmacological NLRP3 inflammasome inhibitor, promoted GLUT4 translocation in fibers isolated from the FDB muscle of NCD- and HFD-fed mice. In conclusion, we found increased NLRP3 inflammasome components in adult skeletal muscle of obese insulin-resistant animals, which might contribute to the low-grade chronic metabolic inflammation of skeletal muscle and IR development.

What can hand grip strength tell us about type 2 diabetes?: mortality, morbidities and risk of diabetes

INTRODUCTION

Hand grip strength (HGS) has been determined as a simple and cost effective method for evaluating overall skeletal muscle strength and quality. It has been used in numerous clinical studies to examine the association between skeletal muscle and type 2 diabetes (T2D). Previous studies have shown that HGS is significantly associated with mortality and cardiovascular disease (CVD) in patients with T2D. As the prevalence of T2D has seen a steady increase globally, HGS measurement can be useful and essential in managing T2D.

AREAS COVERED

This narrative review summarizes the current evidence regarding the association between HGS and T2D. HGS has been considered a useful tool for identifying risks for T2D, CVD, and mortality and evaluating skeletal muscle strength and quality.

OPINION

HGS should be measured in all patients with T2D together with height, weight, and waist circumference. However, there is yet no standard method used in measuring for HGS. T2D patients with a low HGS can engage in resistance training more effectively with appropriate advice based on HGS. Future studies clarifying the genetic association between skeletal muscle and T2D are needed to provide individualized exercise therapy.

Exploring the Role of Skeletal Muscle in Insulin Resistance: Lessons from Cultured Cells to Animal Models

Skeletal muscle is essential to maintain vital functions such as movement, breathing, and thermogenesis, and it is now recognized as an endocrine organ. Muscles release factors named myokines, which can regulate several physiological processes. Moreover, skeletal muscle is particularly important in maintaining body homeostasis, since it is responsible for more than 75% of all insulin-mediated glucose disposal. Alterations of skeletal muscle differentiation and function, with subsequent dysfunctional expression and secretion of myokines, play a key role in the pathogenesis of obesity, type 2 diabetes, and other metabolic diseases, finally leading to cardiometabolic complications. Hence, a deeper understanding of the molecular mechanisms regulating skeletal muscle function related to energy metabolism is critical for novel strategies to treat and prevent insulin resistance and its cardiometabolic complications. This review will be focused on both cellular and animal models currently available for exploring skeletal muscle metabolism and endocrine function.

Urine creatinine concentration and clinical outcomes in older adults: The Cardiovascular Health Study

PURPOSE

Loss of muscle mass and strength are associated with long-term adverse health outcomes in older adults. Urine creatinine concentrations (Ucr; mg/dl) are a measure of muscle tissue mass and turnover. This study assessed the associations of a spot Ucr level with muscle mass and with risk of hospitalization, mortality, and diabetes mellitus in older adults.

METHODS

We examined 3424 participants from the Cardiovascular Health Study who provided spot urine samples in 1996-1997 and who were followed through June 2015. All participants underwent baseline measurement of grip strength. In a sub-cohort, 1331 participants underwent dual energy X-ray absorptiometry (DEXA) scans, from which lean muscle mass was derived. Participants were followed for a median of 10 years for hospitalizations and mortality, and 9 years for diabetes mellitus.

RESULTS

In linear regression analysis, a one standard deviation higher Ucr concentration (64.6 mg/dl) was associated with greater grip strength (kg force) β = 0.44 [0.16, 0.72]; p = 0.002) and higher lean muscle mass (kg) (β = 0.43 [0.08, 0.78]; p = 0.02). In Cox regression analyses, each standard deviation greater Ucr concentration was associated with lower rates of hospitalizations (0.94 [95% confidence interval, 0.90, 0.98]; p < 0.001) and lower mortality risk (0.92 [0.88, 0.97]; p < 0.001), while a one standard deviation increase in muscle mass derived from DEXA had no such significant association. Ucr levels were not associated with incident diabetes mellitus risk (0.97 [0.85, 1.11]; p = 0.65).

CONCLUSION

A higher spot Ucr concentration was favorably associated with muscle mass and strength and with health outcomes in older community-living adults. The ease of obtaining a spot Ucr makes it an attractive analyte to use for gauging the health of older adults.

Dual-Task Exercise to Improve Cognition and Functional Capacity of Healthy Older Adults

Background

It has been suggested that physical inactivity and lack of stimulating cognitive activity are the two most significant modifiable risk factors to impair cognitive function. Although many studies that investigated the cognitive effects of physical exercise and cognitive stimuli in dual-task conditions showed improved cognitive performance, others have not confirmed these findings. The main aim of the present work is to analyze the effects of a dual-task multimodal physical exercise training, at moderate intensity, and cognitive stimulation on cognitive and physical function in healthy older adults.

Methods

This clinical trial was registered on the Brazilian Registry of Clinical Trials (RBR-9zrx3d). Here we tested the effects of a dual-task multimodal physical exercise training, at moderate intensity, on cognitive and physical function and quality of life in community dwelling older adults. The training protocol included 24 group sessions, 2/week, per 75 min. Cognition was assessed using CANTAB automated neuropsychological tests and Functional Capacity to Exercise tests. Performance was compared from baseline to post intervention and to a non-exercise control group using Mixed Linear Model for repeated measures.

Results

Control (CG) and dual-task (DTEx) groups progressed differentially over time on performance of episodic memory, sustained visual attention, functional mobility, cardiorespiratory fitness, lower limbs strength resistance, agility, quality of life and dual-task performance with significant improved DTEx performance. Control group did not show any significant changes on these tests except for showing a reduction in dual-task performance.

Conclusion

We suggest that the dual-task combination of multisensory cognitive stimulation and multimodal moderate physical exercise training, twice a week, may be adopted as an effective program to reduce progression of age-related cognitive decline and improve physical fitness and quality of life on healthy older adults.

Clinical Trial Registration

Brazilian Registry of Clinical Trials: https://ensaiosclinicos.gov.br/rg/RBR-9zrx3d -UTN code: U1111-1233-6349.

Impaired capillary tube formation induced by elevated secretion of IL8 involves altered signaling via the CXCR1/PI3K/MMP2 pathway

Angiogenesis is a multistep process requiring endothelial cell activation, migration, proliferation and tube formation. We recently reported that elevated secretion of interlukin 8 (IL8) by myotubes (MT) from subjects with Type-2 Diabetes (T2D) reduced angiogenesis by human umbilical vein endothelial cells (HUVEC) and human skeletal muscle explants. This lower vascularization was mediated through impaired activation of the phosphatidylinositol 3-kinase (PI3K)-pathway. We sought to investigate additional signaling elements that might mediate reduced angiogenesis. HUVEC were exposed to levels of IL8 equal to those secreted by MT from non-diabetic (ND) and T2D subjects and the involvement of components in the angiogenic response pathway examined. Cellular content of reactive oxygen species and Nitrate secretion were similar after treatment with [ND-IL8] and [T2D-IL8]. CXCR1 protein was down-regulated after treatment with [T2D-IL8] (p < 0.01 vs [ND-IL8] treatment); CXCR2 expression was unaltered. Addition of neutralizing antibodies against CXCR1 and CXCR2 to HUVEC treated with IL8 confirmed that CXCR1 alone mediated the angiogenic response to IL8. A key modulator of angiogenesis is matrix metalloproteinase-2 (MMP2). MMP2 secretion was higher after treatment with [ND-IL8] vs [T2D-IL8] (p < 0.01). MMP2 inhibition reduced tube formation to greater extent with [ND-IL8] than with [T2D-IL8] (p < 0.005). The PI3K-pathway inhibitor LY294002 reduced IL8-induced MMP2 release. IL8 regulation of MMP2 release was CXCR1 dependent, as anti-CXCR1 significantly reduced MMP2 release (p < 0.05). These results suggest that high levels of IL8 secreted by T2D MT trigger reduced capillarization via lower activation of a CXCR1-PI3K pathway, followed by impaired release and activity of MMP2.

The β3 Adrenergic Receptor Agonist CL316243 Ameliorates the Metabolic Abnormalities of High-Fat Diet-Fed Rats by Activating AMPK/PGC-1α Signaling in Skeletal Muscle

PURPOSE

Skeletal muscle has a major influence on whole-body metabolic homeostasis. In the present study, we aimed to determine the metabolic effects of the β3 adrenergic receptor agonist CL316243 (CL) in the skeletal muscle of high-fat diet-fed rats.

METHODS

Sprague-Dawley rats were randomly allocated to three groups, which were fed a control diet (C) or a high-fat diet (HF), and half of the latter were administered 1 mg/kg CL by gavage once weekly (HF+CL), for 12 weeks. At the end of this period, the serum lipid profile and glucose tolerance of the rats were evaluated. In addition, the phosphorylation and protein and mRNA expression of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator (PGC)-1α, and carnitine palmitoyl transferase (CPT)-1b in skeletal muscle were measured by Western blot analysis and qPCR. The direct effects of CL on the phosphorylation (p-) and expression of AMPK, PGC-1α, and CPT-1b were also evaluated by Western blotting and immunofluorescence in L6 myotubes.

RESULTS

CL administration ameliorated the abnormal lipid profile and glucose tolerance of the high-fat diet-fed rats. In addition, the expression of p-AMPK, PGC-1α, and CPT-1b in the soleus muscle was significantly increased by CL. CL (1 µM) also increased the protein expression of p-AMPK, PGC-1α, and CPT-1b in L6 myotubes. However, the effect of CL on PGC-1α protein expression was blocked by the AMPK antagonist compound C, which suggests that CL increases PGC-1α protein expression via AMPK.

CONCLUSION

Activation of the β3 adrenergic receptor in skeletal muscle ameliorates the metabolic abnormalities of high-fat diet-fed rats, at least in part via activation of the AMPK/PGC-1α pathway.

Skeletal muscle extracellular matrix remodeling with worsening glycemic control in nonhuman primates

Type 2 diabetes (T2D) development may be mediated by skeletal muscle (SkM) function, which is responsible for >80% of circulating glucose uptake. The goals of this study were to assess changes in global- and location-level gene expression, remodeling proteins, fibrosis, and vascularity of SkM with worsening glycemic control, through RNA sequencing, immunoblotting, and immunostaining. We evaluated SkM samples from health-diverse African green monkeys (Cholorcebus aethiops sabaeus) to investigate these relationships. We assessed SkM remodeling at the molecular level by evaluating unbiased transcriptomics in age-, sex-, weight-, and waist circumference-matched metabolically healthy, prediabetic (PreT2D) and T2D monkeys (n = 13). Our analysis applied novel location-specific gene differences and shows that extracellular facing and cell membrane-associated genes and proteins are highly upregulated in metabolic disease. We verified transcript patterns using immunohistochemical staining and protein analyses of matrix metalloproteinase 16 (MMP16), tissue inhibitor of metalloproteinase 2 (TIMP2), and VEGF. Extracellular matrix (ECM) functions to support intercellular communications, including the coupling of capillaries to muscle cells, which was worsened with increasing blood glucose. Multiple regression modeling from age- and health-diverse monkeys (n = 33) revealed that capillary density was negatively predicted by only fasting blood glucose. The loss of vascularity in SkM co-occurred with reduced expression of hypoxia-sensing genes, which is indicative of a disconnect between altered ECM and reduced endothelial cells, and known perfusion deficiencies present in PreT2D and T2D. This report supports that rising blood glucose values incite ECM remodeling and reduce SkM capillarization, and that targeting ECM would be a rational approach to improve health with metabolic disease.

Impact of diets rich in olive oil, palm oil or lard on myokine expression in rats

It has recently emerged that myokines may be an important skeletal muscle adaptive response to obesogenic diets in sedentary subjects (who do not exercise). This study aimed to assess the influence of various high fat (HF) diets rich in either crude palm oil (cPO), refined palm oil (rPO), olive oil (OO) or lard on the modulation of myokine gene expression in the gastrocnemius. Five groups of 8 rats were each fed HF or control diet for 12 weeks. Systemic parameters concerning glucose, insulin, inflammation, cholesterol, triglycerides (TG) and transaminases were assessed by routine methods or ELISA. Akt and ACC phosphorylation were analyzed by WB in the soleus. Mitochondrial density, inflammation, and the gene expression of 17 myokines and the apelin receptor (Apj) were assessed by qPCR in the gastrocnemius. We found that HF diet-fed rats were insulin resistant and Akt phosphorylation decreased in the soleus muscle, but without any change in Glut4 gene expression. Systemic (IL-6) and muscle inflammation (NFκB and IκB) were not affected by the HF diets as well as TBARS, and ASAT level was enhanced with OO diet. Soleus pACC phosphorylation and gastrocnemius mitochondrial density were not significantly altered. The gene expression of some myokines was respectively increased (myostatin and Il-15) and decreased (Fndc5 and apelin) with the HF diets, whatever the type of fat used. The gene expression of two myokines with anti-inflammatory properties, Il-10 and myonectin, was dependent on the type of fat used and was most increased respectively with cPO or both rPO and OO diets. In conclusion, high-fat diets can differentially modulate the expression of some myokines, either in a dependent manner or independently of their composition.

Muscle-Organ Crosstalk: Focus on Immunometabolism

Skeletal muscle secretes several hundred myokines that facilitate communication from muscle to other organs, such as, adipose tissue, pancreas, liver, gut, and brain. The biological roles of myokines include effects on e.g., memory and learning, as well as glucose and lipid metabolism. The present minireview focuses on recent developments showing that exercise-induced myokines are involved in immunometabolism of importance for the control of e.g., tumor growth and chronic inflammation. In this review, immunometabolism is discussed as the non-immune related pathologies leading to an immune response and some degree of inflammation, which promotes metabolic abnormalities.

Antidiabetic effects of a lipophilic extract obtained from flowers of Wisteria sinensis by activating Akt/GLUT4 and Akt/GSK3β

Background

Type 2 diabetes mellitus is primarily caused by insulin resistance (IR) in insulin-sensitive tissues, including liver, white adipose tissues (WAT), and skeletal muscles. Discovering nutritious foods with antidiabetic effects is of great significance. Numerous published reports indicated that protein kinase B (Akt) and glucose transporter 4 (GLUT4) play crucial roles in ameliorating IR and diabetic symptoms.

Objective

In the present study, antidiabetic effects and the potential mechanism of action of WS-PE (a lipophilic extract from edible flowers of Wisteria sinensis) were explored with L6 cells in vitro and in high-fat diet (HFD) + Streptozocin (STZ)-induced diabetic mice in vivo.

Design

In vivo, HFD + STZ-induced diabetic mice were used as diabetic models to investigate the potential antidiabetic and antidyslipidemic activities. In vitro, a novel GLUT4 translocation assay system was established to evaluate the potential effects of WS-PE on GLUT4 translocation. Western blot analysis was adopted to investigate the molecular mechanisms of WS-PE both in vivo and in vitro.

Results

vitro, WS-PE increased glucose uptake by stimulating GLUT4 expression and translocation, which were regulated by Akt phosphorylation. In vivo, the WS-PE treatment ameliorated the hyperglycemia, IR, and dyslipidemia and reversed hepatic steatosis and pancreatic damage in diabetic mice. The WS-PE treatment increased GLUT4 expression by Akt activation in WAT and skeletal muscle. Akt activation stimulated GSK3β phosphorylation in liver and skeletal muscles, indicating that WS-PE showed regulatory effects on glycogen synthesis in liver and skeletal muscles.

Conclusion

These in vitro and in vivo results indicated that the WS-PE treatment exerted antidiabetic effects by activating Akt/GLUT4 and Akt/GSK3β.

Muscle-Organ Crosstalk: The Emerging Roles of Myokines

Physical activity decreases the risk of a network of diseases, and exercise may be prescribed as medicine for lifestyle-related disorders such as type 2 diabetes, dementia, cardiovascular diseases, and cancer. During the past couple of decades, it has been apparent that skeletal muscle works as an endocrine organ, which can produce and secrete hundreds of myokines that exert their effects in either autocrine, paracrine, or endocrine manners. Recent advances show that skeletal muscle produces myokines in response to exercise, which allow for crosstalk between the muscle and other organs, including brain, adipose tissue, bone, liver, gut, pancreas, vascular bed, and skin, as well as communication within the muscle itself. Although only few myokines have been allocated to a specific function in humans, it has been identified that the biological roles of myokines include effects on, for example, cognition, lipid and glucose metabolism, browning of white fat, bone formation, endothelial cell function, hypertrophy, skin structure, and tumor growth. This suggests that myokines may be useful biomarkers for monitoring exercise prescription for people with, for example, cancer, diabetes, or neurodegenerative diseases.

Sarcopenic obesity: Myokines as potential diagnostic biomarkers and therapeutic targets?

Sarcopenic obesity (SO) is a condition characterized by the occurrence of both sarcopenia and obesity and imposes a heavy burden on the health of the elderly. Controversies and challenges regarding the definition, diagnosis and treatment of SO still remain because of its complex pathogenesis and limitations. Over the past few decades, numerous studies have revealed that myokines secreted from skeletal muscle play significant roles in the regulation of muscle mass and function as well as metabolic homeostasis. Abnormalities in myokines may trigger and promote the pathogenesis underlying age-related and metabolic diseases, including obesity, sarcopenia, type 2 diabetes (T2D), and SO. This review mainly focuses on the role of myokines as potential biomarkers for the early diagnosis and therapeutic targets in SO.

Current understanding of the role of Adipose-derived Extracellular Vesicles in Metabolic Homeostasis and Diseases: Communication from the distance between cells/tissues

Extracellular vesicles (EVs) including exosomes, microvesicles (MVs), and apoptotic bodies, are small membrane vesicular structures that are released during cell activation, senescence, or programmed cell death, including apoptosis, necroptosis, and pyroptosis. EVs serve as novel mediators for long-distance cell-to-cell communications and can transfer various bioactive molecules, such as encapsulated cytokines and genetic information from their parental cells to distant target cells. In the context of obesity, adipocyte-derived EVs are implicated in metabolic homeostasis serving as novel adipokines. In particular, EVs released from brown adipose tissue or adipose-derived stem cells may help control the remolding of white adipose tissue towards browning and maintaining metabolic homeostasis. Interestingly, EVs may even serve as mediators for the transmission of metabolic dysfunction across generations. Also, EVs have been recognized as novel modulators in various metabolic disorders, including insulin resistance, diabetes mellitus, and non-alcoholic fatty liver disease. In this review, we summarize the latest progress from basic and translational studies regarding the novel effects of EVs on metabolic diseases. We also discuss EV-mediated cross-talk between adipose tissue and other organs/tissues that are relevant to obesity and metabolic diseases, as well as the relevant mechanisms, providing insight into the development of new therapeutic strategies in obesity and metabolic diseases.

Physical Exercise and Myokines: Relationships with Sarcopenia and Cardiovascular Complications

Skeletal muscle is capable of secreting different factors in order to communicate with other tissues. These mediators, the myokines, show potentially far-reaching effects on non-muscle tissues and can provide a molecular interaction between muscle and body physiology. Sarcopenia is a chronic degenerative neuromuscular disease closely related to cardiomyopathy and chronic heart failure, which influences the production and release of myokines. Our objective was to explore the relationship between myokines, sarcopenia, and cardiovascular diseases (CVD). The autocrine, paracrine, and endocrine actions of myokines include regulation of energy expenditure, insulin sensitivity, lipolysis, free fatty acid oxidation, adipocyte browning, glycogenolysis, glycogenesis, and general metabolism. A sedentary lifestyle accelerates the aging process and is a risk factor for developing sarcopenia, metabolic syndrome, and CVD. Increased adipose tissue resulting from the decrease in muscle mass in patients with sarcopenia may also be involved in the pathology of CVD. Myokines are protagonists in the complex condition of sarcopenia, which is associated with adverse clinical outcomes in patients with CVD. The discovery of new pathways and the link between myokines and CVD remain a cornerstone toward multifaceted interventions and perhaps the minimization of the damage resulting from muscle loss induced by factors such as atherosclerosis.

Growth and differentiation factor 15 is secreted by skeletal muscle during exercise and promotes lipolysis in humans

We hypothesized that skeletal muscle contraction produces a cellular stress signal, triggering adipose tissue lipolysis to sustain fuel availability during exercise. The present study aimed at identifying exercise-regulated myokines, also known as exerkines, able to promote lipolysis. Human primary myotubes from lean healthy volunteers were submitted to electrical pulse stimulation (EPS) to mimic either acute intense or chronic moderate exercise. Conditioned media (CM) experiments with human adipocytes were performed. CM and human plasma samples were analyzed using unbiased proteomic screening and/or ELISA. Real-time qPCR was performed in cultured myotubes and muscle biopsy samples. CM from both acute intense and chronic moderate exercise increased basal lipolysis in human adipocytes. Growth and differentiation factor 15 (GDF15) gene expression and secretion increased rapidly upon skeletal muscle contraction. GDF15 protein was upregulated in CM from both acute and chronic exercise-stimulated myotubes. We further showed that physiological concentrations of recombinant GDF15 protein increased lipolysis in human adipose tissue, while blocking GDF15 with a neutralizing antibody abrogated EPS CM-mediated lipolysis. We herein provide the first evidence to our knowledge that GDF15 is a potentially novel exerkine produced by skeletal muscle contraction and able to target human adipose tissue to promote lipolysis.

Plasma Myokine Concentrations After Acute Exercise in Non-obese and Obese Sedentary Women

Exercise and physical activity levels influence myokine release from skeletal muscle and contribute to circulating concentrations. Indeed, many myokines, including interleukin (IL)-6, IL-15, secreted protein acidic rich in cysteine (SPARC), and fibroblast growth factor (FGF) 21 are higher in the circulation after an exercise bout. Since these peptides modulate muscle metabolism and can also be targeted toward other tissues to induce adaptations to energy demand, they are of great interest regarding metabolic diseases. Therefore, we set out to compare, in six women with obesity (BMI ≥30 kg/m²) and five healthy women (BMI 22–29.9 kg/m²), the effect of an acute bout of moderate-intensity, continuous cycling exercise (60 min, 60% VO₂peak) on the release of myokines (IL-6, IL-8, IL-10, IL-13, IL-15, SPARC, and FGF21) in plasma for a 24-h time course. We found that plasma IL-8 and SPARC levels were reduced in the group of women with obesity, whereas plasma IL-13 concentrations were elevated in comparison to non-obese women both before and after the exercise bout. We also found that plasma FGF21 concentration during the 24 h following the bout of exercise was regulated differently in the non-obese in comparison to obese women. Plasma concentrations of FGF21, IL-6, IL-8, IL-15, and IL-18 were regulated by acute exercise. Our results confirm the results of others concerning exercise regulation of circulating myokines while providing insight into the time course of myokine release in circulation after an acute exercise bout and the differences in circulating myokines after exercise in women with or without obesity.