Exercise and Muscle Lipid Content, Composition, and Localization: Influence on Muscle Insulin Sensitivity

Myostatin regulates energy homeostasis through autocrine- and paracrine-mediated microenvironment communication

Myostatin (MSTN) has long been recognized as a critical regulator of muscle mass. Recently, there has been increasing interest in its role in metabolism. In our study, we specifically knocked out MSTN in brown adipose tissue (BAT) from mice (MSTNΔUCP1) and found that the mice gained more weight than did controls when fed a high-fat diet, with progressive hepatosteatosis and impaired skeletal muscle activity. RNA-Seq analysis indicated signatures of mitochondrial dysfunction and inflammation in the MSTN-ablated BAT. Further studies demonstrated that Kruppel-like factor 4 (KLF4) was responsible for the metabolic phenotypes observed, whereas fibroblast growth factor 21 (FGF21) contributed to the microenvironment communication between adipocytes and macrophages induced by the loss of MSTN. Moreover, the MSTN/SMAD2/3-p38 signaling pathway mediated the expression of KLF4 and FGF21 in adipocytes. In summary, our findings suggest that brown adipocyte-derived MSTN regulated BAT thermogenesis via autocrine and paracrine effects on adipocytes or macrophages, ultimately regulating systemic energy homeostasis.

Unraveling the link between cardiorespiratory fitness and cancer: a state-of-the-art review

Cardiorespiratory fitness (CRF) not only reflects an individual's capacity to perform physical activities but also encapsulates broader effects on the basic biology of aging. This review aims to summarize the evidence on the influence of CRF on overall and site-specific cancer risks. It delves into the biological mechanisms through which CRF may exert its effects, explores the clinical implications of these findings, identifies gaps in the current evidence base, and suggests directions for future research. The synthesis of findings reveals that higher CRF levels (general threshold of > 7 METs) are consistently associated with a reduced risk of a range of cancers, including head and neck, lung, breast, gastrointestinal, particularly pancreatic and colorectal, bladder, overall cancer incidence and mortality, and potentially stomach and liver, bile duct, and gall bladder cancers. These inverse associations between CRF and cancer risk do not generally differ across age groups, sex, race, or adiposity, suggesting a universal protective effect of CRF. Nonetheless, evidence linking CRF with skin, mouth and pharynx, kidney, and endometrial cancers is limited and inconclusive. Conversely, higher CRF levels may be potentially linked to an increased risk of prostate cancer and hematological malignancies, such as leukemia and myeloma, although the evidence is still not conclusive. CRF appears to play a significant role in reducing the risk of several cancers through various biological mechanisms, including inflammation reduction, immune system enhancement, hormonal regulation, and metabolic improvements. Overall, enhancing CRF through regular physical activity offers a vital, accessible strategy for reducing cancer risk and extending the health span. Future research should aim to fill the existing evidence gaps regarding specific cancers and elucidate the detailed dose-response relationships between CRF levels and cancer risk. Studies are also needed to elucidate the causal relationships and mechanistic pathways linking CRF to cancer outcomes.

The Effect of High-Fat Diet on Intramyocellular Lipid Content in Healthy Adults: A Systematic Review, Meta-Analysis, and Meta-Regression

Fatty acids are stored within the muscle as intramyocellular lipids (IMCL). Some, but not all, studies indicate that following a high-fat diet (HFD), IMCL may accumulate and affect insulin sensitivity. This systematic review and meta-analysis aimed to quantify the effects of an HFD on IMCL. It also explored the potential modifying effects of HFD fat content and duration, IMCL measurement technique, physical activity status, and the associations of IMCL with insulin sensitivity. Five databases were systematically searched for studies that examined the effect of ≥3 d of HFD (>35% daily energy intake from fat) on IMCL content in healthy individuals. Meta-regressions were used to investigate associations of the HFD total fat content, duration, physical activity status, IMCL measurement technique, and insulin sensitivity with IMCL responses. Changes in IMCL content and insulin sensitivity (assessed by hyperinsulinemic-euglycemic clamp) are presented as standardized mean difference (SMD) using a random effects model with 95% confidence intervals (95% CIs). Nineteen studies were included in the systematic review and 16 in the meta-analysis. IMCL content increased following HFD (SMD = 0.63; 95% CI: 0.31, 0.94, P = 0.001). IMCL accumulation was not influenced by total fat content (P = 0.832) or duration (P = 0.844) of HFD, physical activity status (P = 0.192), or by the IMCL measurement technique (P > 0.05). Insulin sensitivity decreased following HFD (SMD = -0.34; 95% CI: -0.52, -0.16; P = 0.003), but this was not related to the increase in IMCL content following HFD (P = 0.233). Consumption of an HFD (>35% daily energy intake from fat) for ≥3 d significantly increases IMCL content in healthy individuals regardless of HFD total fat content and duration of physical activity status. All IMCL measurement techniques detected the increased IMCL content following HFD. The dissociation between changes in IMCL and insulin sensitivity suggests that other factors may drive HFD-induced impairments in insulin sensitivity in healthy individuals. This trial was registered at PROSPERO as CRD42021257984.

Glucagon-like peptide-1 and interleukin-6 interaction in response to physical exercise: An in-silico model in the framework of immunometabolism

BACKGROUND AND OBJECTIVE

Glucagon-like peptide 1 (GLP-1) is classically identified as an incretin hormone, secreted in response to nutrient ingestion and able to enhance glucose-stimulated insulin secretion. However, other stimuli, such as physical exercise, may enhance GLP-1 plasma levels, and this exercise-induced GLP-1 secretion is mediated by interleukin-6 (IL-6), a cytokine secreted by contracting skeletal muscle. The aim of the study is to propose a mathematical model of IL-6-induced GLP-1 secretion and kinetics in response to physical exercise of moderate intensity.

METHODS

The model includes the GLP-1 subsystem (with two pools: gut and plasma) and the IL-6 subsystem (again with two pools: skeletal muscle and plasma); it provides a parameter of possible clinical relevance representing the sensitivity of GLP-1 to IL-6 (k0). The model was validated on mean IL-6 and GLP-1 data derived from the scientific literature and on a total of 100 virtual subjects.

RESULTS

Model validation provided mean residuals between 0.0051 and 0.5493 pg⋅mL-1 for IL-6 (in view of concentration values ranging from 0.8405 to 3.9718 pg⋅mL-1) and between 0.0133 and 4.1540 pmol⋅L-1 for GLP-1 (in view of concentration values ranging from 0.9387 to 17.9714 pmol⋅L-1); a positive significant linear correlation (r = 0.85, p<0.001) was found between k0 and the ratio between areas under GLP-1 and IL-6 curve, over the virtual subjects.

CONCLUSIONS

The model accurately captures IL-6-induced GLP-1 kinetics in response to physical exercise.

The Effects of Resistance Exercise Training on Skeletal Muscle Metabolism and Insulin Resistance Development in Female Rodents with Type 1 Diabetes

The etiology of insulin resistance (IR) development in type 1 diabetes mellitus (T1DM) remains unclear; however, impaired skeletal muscle metabolism may play a role. While IR development has been established in male T1DM rodents, female rodents have yet to be examined in this context. Resistance exercise training (RT) has been shown to improve IR and is associated with a lower risk of hypoglycemia onset in T1DM compared to aerobic exercise. The purpose of this study was to investigate the effects of RT on IR development in female T1DM rodents. Forty Sprague Dawley eight-week-old female rats were divided into four groups: control sedentary (CS; n = 10), control trained (CT; n = 10), T1DM sedentary (DS; n = 10), and T1DM trained (DT; n = 10). Multiple low-dose streptozotocin injections were used to induce T1DM. Blood glucose levels were maintained in the 4-9 mmol/l range with intensive insulin therapy. CT and DT underwent weighted ladder climbing 5 days/week for six weeks. Intravenous glucose tolerance tests (IVGTT) were conducted on all animals following the six-week period. Results demonstrate that DS animals exhibited significantly increased weekly blood glucose measures compared to all groups including DT (p < 0.0001), despite similar insulin dosage levels. This was concomitant with a significant increase in insulin-adjusted area under the curve following IVGTT in DS (p < 0.05), indicative of a reduction in insulin sensitivity. Both DT and DS exhibited greater serum insulin concentrations compared to CT and CS (p < 0.05). DS animals also exhibited significantly greater glycogen content in white gastrocnemius muscle compared to CS and DT (p < 0.05), whereas DT and DS animals exhibited greater p-Akt: Akt ratio in the white vastus lateralis muscle and citrate synthase activity in the red vastus lateralis muscle compared to CS and CT (p < 0.05). These results indicate that female rodents with T1DM develop poor glycemic control and IR which can be attenuated with RT, possibly related to differences in intramyocellular glycogen content.

Divergent Skeletal Muscle Metabolomic Signatures of Different Exercise Training Modes Independently Predict Cardiometabolic Risk Factors

We investigated the link between enhancement of SI (by hyperinsulinemic-euglycemic clamp) and muscle metabolites after 12 weeks of aerobic (high-intensity interval training [HIIT]), resistance training (RT), or combined training (CT) exercise in 52 lean healthy individuals. Muscle RNA sequencing revealed a significant association between SI after both HIIT and RT and the branched-chain amino acid (BCAA) metabolic pathway. Concurrently with increased expression and activity of branched-chain ketoacid dehydrogenase enzyme, many muscle amino metabolites, including BCAAs, glutamate, phenylalanine, aspartate, asparagine, methionine, and γ-aminobutyric acid, increased with HIIT, supporting the substantial impact of HIIT on amino acid metabolism. Short-chain C3 and C5 acylcarnitines were reduced in muscle with all three training modes, but unlike RT, both HIIT and CT increased tricarboxylic acid metabolites and cardiolipins, supporting greater mitochondrial activity with aerobic training. Conversely, RT and CT increased more plasma membrane phospholipids than HIIT, suggesting a resistance exercise effect on cellular membrane protection against environmental damage. Sex and age contributed modestly to the exercise-induced changes in metabolites and their association with cardiometabolic parameters. Integrated transcriptomic and metabolomic analyses suggest various clusters of genes and metabolites are involved in distinct effects of HIIT, RT, and CT. These distinct metabolic signatures of different exercise modes independently link each type of exercise training to improved SI and cardiometabolic risk.

ARTICLE HIGHLIGHTS

We aimed to understand the link between skeletal muscle metabolites and cardiometabolic health after exercise training. Although aerobic, resistance, and combined exercise training each enhance muscle insulin sensitivity as well as other cardiometabolic parameters, they disparately alter amino and citric acid metabolites as well as the lipidome, linking these metabolomic changes independently to the improvement of cardiometabolic risks with each exercise training mode. These findings reveal an important layer of the unique exercise mode-dependent changes in muscle metabolism, which may eventually lead to more informed exercise prescription for improving SI.

Geroprotector drugs and exercise: friends or foes on healthy longevity?

Physical activity and several pharmacological approaches individually combat age-associated conditions and extend healthy longevity in model systems. It is tantalizing to extrapolate that combining geroprotector drugs with exercise could extend healthy longevity beyond any individual treatment. However, the current dogma suggests that taking leading geroprotector drugs on the same day as exercise may limit several health benefits. Here, we review leading candidate geroprotector drugs and their interactions with exercise and highlight salient gaps in knowledge that need to be addressed to identify if geroprotector drugs can have a harmonious relationship with exercise.

Lipidomics Characterization of the Microbiome in People with Diabetic Foot Infection Using MALDI-TOF MS

Lipidomic profiling has emerged as a powerful tool for the comprehensive characterization of bacterial species, particularly in the context of clinical diagnostics. Utilizing matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), this study aims to elucidate the lipidomic landscapes of bacterial strains isolated from diabetic foot infections (DFI). Our analysis successfully identified a diverse array of lipids in the cellular membranes of both Gram-positive and Gram-negative bacteria, revealing a total of 108 unique fatty acid combinations. Specifically, we identified 26 LPG, 33 LPE, 43 PE, 114 PG, 89 TAG, and 120 CLP in Gram-positive bacteria and 10 LPG, 14 LPE, 124 PE, 37 PG, 13 TAG, and 22 CLP in Gram-negative strains. Key fatty acids, such as palmitic acid, palmitoleic acid, stearic acid, and oleic acid, were prominently featured. Univariate analysis further highlighted distinct lipidomic signatures among the bacterial strains, revealing elevated levels of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) in Gram-negative bacteria associated with DFI. In contrast, Gram-positive strains demonstrated increased or uniquely fluctuating levels of triglyceride (TAG) and cardiolipin (CLP). These findings not only underscore the utility of MALDI-TOF MS in bacterial lipidomics but also provide valuable insights into the lipidomic adaptations of bacteria in diabetic foot infections, thereby laying the groundwork for future studies aimed at constructing microbial lipid libraries for enhanced bacterial identification.

Muscle-specific overexpression of Atg2 gene and endurance exercise delay age-related deteriorations of skeletal muscle and heart function via activating the AMPK/Sirt1/PGC-1α pathway in male Drosophila

Atg2 is a key gene in autophagy formation and plays an important role in regulating aging progress. Exercise is an important tool to resist oxidative stress in cells and delay muscle aging. However, the relationship between exercise and the muscle Atg2 gene in regulating skeletal muscle aging remains unclear. Here, overexpression or knockdown of muscle Atg2 gene was achieved by constructing the AtgUAS/MhcGal4 system in Drosophila, and these flies were also subjected to an exercise intervention for 2 weeks. The results showed that both overexpression of Atg2 and exercise significantly increased the climbing speed, climbing endurance, cardiac function, and lifespan of aging flies. They also significantly up-regulated the expression of muscle Atg2, AMPK, Sirt1, and PGC-1α genes, and they significantly reduced muscle malondialdehyde and triglyceride. These positive benefits were even more pronounced when the two were combined. However, the effects of Atg2 knockdown on skeletal muscle, heart, and lifespan were reversed compared to its overexpression. Importantly, exercise ameliorated age-related changes induced by Atg2 knockdown. Therefore, current results confirmed that both overexpression of muscle Atg2 and exercise delayed age-related deteriorations of skeletal muscle, the heart function, and lifespan, and exercise could also reverse age-related changes induced by Atg2 knockdown. The molecular mechanism is related to the overexpression of the Atg2 gene and exercise, which increase the activity of the AMPK/Sirt1/PGC-1α pathway, oxidation and antioxidant balance, and lipid metabolism in aging muscle.

The roles of DGAT1 and DGAT2 in human myotubes are dependent on donor patho-physiological background

The roles of DGAT1 and DGAT2 in lipid metabolism and insulin responsiveness of human skeletal muscle were studied using cryosections and myotubes prepared from muscle biopsies from control, athlete, and impaired glucose regulation (IGR) cohorts of men. The previously observed increases in intramuscular triacylglycerol (IMTG) in athletes and IGR were shown to be related to an increase in lipid droplet (LD) area in type I fibers in athletes but, conversely, in type II fibers in IGR subjects. Specific inhibition of both diacylglycerol acyltransferase (DGAT) 1 and 2 decreased fatty acid (FA) uptake by myotubes, whereas only DGAT2 inhibition also decreased fatty acid oxidation. Fatty acid uptake in myotubes was negatively correlated with the lactate thresholds of the respective donors. DGAT2 inhibition lowered acetate uptake and oxidation in myotubes from all cohorts whereas DGAT1 inhibition had no effect. A positive correlation between acetate oxidation in myotubes and resting metabolic rate (RMR) from fatty acid oxidation in vivo was observed. Myotubes from athletes and IGR had higher rates of de novo lipogenesis from acetate that were normalized by DGAT2 inhibition. Moreover, DGAT2 inhibition in myotubes also resulted in increased insulin-induced Akt phosphorylation. The differential effects of DGAT1 and DGAT2 inhibition suggest that the specialized role of DGAT2 in esterifying nascent diacylglycerols and de novo synthesized FA is associated with synthesis of a pool of triacylglycerol, which upon hydrolysis results in effectors that promote mitochondrial fatty acid oxidation but decrease insulin signaling in skeletal muscle cells.

Deoxysphingolipids: Atypical Skeletal Muscle Lipids Related to Insulin Resistance in Humans That Decrease Insulin Sensitivity In Vitro

Sphingolipids are thought to promote skeletal muscle insulin resistance. Deoxysphingolipids (dSLs) are atypical sphingolipids that are increased in the plasma of individuals with type 2 diabetes and cause β-cell dysfunction in vitro. However, their role in human skeletal muscle is unknown. We found that dSL species are significantly elevated in muscle of individuals with obesity and type 2 diabetes compared with athletes and lean individuals and are inversely related to insulin sensitivity. Furthermore, we observed a significant reduction in muscle dSL content in individuals with obesity who completed a combined weight loss and exercise intervention. Increased dSL content in primary human myotubes caused a decrease in insulin sensitivity associated with increased inflammation, decreased AMPK phosphorylation, and altered insulin signaling. Our findings reveal a central role for dSL in human muscle insulin resistance and suggest dSLs as therapeutic targets for the treatment and prevention of type 2 diabetes.

ARTICLE HIGHLIGHTS

Deoxysphingolipids (dSLs) are atypical sphingolipids elevated in the plasma of individuals with type 2 diabetes, and their role in muscle insulin resistance has not been investigated. We evaluated dSL in vivo in skeletal muscle from cross-sectional and longitudinal insulin-sensitizing intervention studies and in vitro in myotubes manipulated to synthesize higher dSLs. dSLs were increased in the muscle of people with insulin resistance, inversely correlated to insulin sensitivity, and significantly decreased after an insulin-sensitizing intervention; increased intracellular dSL concentrations cause myotubes to become more insulin resistant. Reduction of muscle dSL levels is a potential novel therapeutic target to prevent/treat skeletal muscle insulin resistance.

Exercise and Prediabetes After Renal Transplantation (EXPRED-I): A Prospective Study

BACKGROUND

Post-transplant diabetes mellitus (PTDM) beyond 12 months (late PTDM) is a severe complication after renal transplantation. Late PTDM develops mostly in subjects with prediabetes. Although exercise may have a potential role in preventing late PTDM, there are no previous data on the effect of exercise in patients with prediabetes.

MATERIAL AND METHODS

The design was a 12-month exploratory study to test the capacity of exercise in reverting prediabetes in order to prevent late-PTDM. The outcome was the reversibility of prediabetes, assessed every 3 months with oral glucose tolerance tests (OGTT). The protocol included an incremental plan of aerobic and/or strength training as well as an active plan for promoting adherence (telephone calls, digital technology, and visits). A priori, a sample size cannot be calculated which makes this an exploratory analysis. Based on previous studies, the spontaneous reversibility of prediabetes was 30% and the reversibility induced by exercise will account for another 30%, a total reversibility of 60% (p value < 0.05, assuming a potency of 85%). Ad interim analysis was performed during follow-up to test the certainty of this sample calculation. Patients beyond 12 months after renal transplantation with prediabetes were included.

RESULTS

The study was interrupted early due to efficacy after the evaluation of the follow-up of 27 patients. At the end of follow-up, 16 (60%) patients reverted to normal glucose levels at fasting (from 102.13 mg/dL ± 11 to 86.75 ± 6.9, p = 0.006) and at 120 min after the OGTTs (154.44 mg/dL ± 30 to 113.0 ± 13.1, p = 0.002) and 11 patients had persistent prediabetes (40%). Also, insulin sensitivity improved with the reversibility of prediabetes, compared to those with persistent prediabetes: 0.09 [0.08-0.11] versus 0.04 [0.01-0.07], p = 0.001 (Stumvoll index). Most needed at least one increment in the prescription of exercise and compliance. Finally, measures aimed at the improvement of compliance were successful in 22 (80%) patients.

CONCLUSION

Exercise training was effective to improve glucose metabolism in renal transplant patients with prediabetes. Exercise prescription must be conducted considering both the clinical characteristics of the patients and pre-defined strategy to promote adherence. The trial registration number of the study was NCT04489043.

Muscle group-specific skeletal muscle aging: a 5-yr longitudinal study in septuagenarians

There is some evidence that the age-associated change in skeletal muscle mass is muscle specific, yet the number of specific muscles that have been studied to form our understanding in this area is limited. In addition, few aging investigations have examined multiple muscles in the same individuals. This longitudinal investigation compared changes in skeletal muscle size via computed tomography of the quadriceps (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius), hamstrings (biceps femoris short and long heads, semitendinosus, and semimembranosus), psoas, rectus abdominis, lateral abdominals (obliques and transversus abdominis), and paraspinal muscles (erector spinae and multifidi) of older individuals from the Health, Aging, and Body Composition (Health ABC) study at baseline and 5.0 ± 0.1 years later (n = 469, 73 ± 3 yr and 78 ± 3 yr, 49% women, 33% black). Skeletal muscle size decreased (P < 0.05) in quadriceps (-3.3%), hamstrings (-5.9%), psoas (-0.4%), and rectus abdominis (-7.0%). The hamstrings and rectus abdominis atrophied approximately twice as much as the quadriceps (P < 0.05), whereas the quadriceps atrophied substantially more than the psoas (P < 0.05). The lateral abdominals (+5.9%) and paraspinals (+4.3%) hypertrophied (P < 0.05) to a similar degree (P > 0.05) over the 5 years. These data suggest that older individuals experience skeletal muscle atrophy and hypertrophy in a muscle group-specific fashion in the eighth decade, a critical time period in the aging process. A broader understanding of muscle group-specific skeletal muscle aging is needed to better guide exercise programs and other interventions that mitigate decrements in physical function with aging.NEW & NOTEWORTHY These longitudinal analyses of six muscle groups in septuagenarians provide novel information on the muscle group-specific aging process. Although the quadriceps, hamstrings, psoas, and rectus abdominis atrophied with different magnitudes, the lateral abdominals and paraspinals hypertrophied over the 5 years. These findings contribute to a better understanding of the skeletal muscle aging process and highlight the need to complete studies in this area with a muscle-specific focus.

The Key Role of Mitochondrial Function in Health and Disease

The role of mitochondrial function in health and disease has become increasingly recognized, particularly in the last two decades. Mitochondrial dysfunction as well as disruptions of cellular bioenergetics have been shown to be ubiquitous in some of the most prevalent diseases in our society, such as type 2 diabetes, cardiovascular disease, metabolic syndrome, cancer, and Alzheimer's disease. However, the etiology and pathogenesis of mitochondrial dysfunction in multiple diseases have yet to be elucidated, making it one of the most significant medical challenges in our history. However, the rapid advances in our knowledge of cellular metabolism coupled with the novel understanding at the molecular and genetic levels show tremendous promise to one day elucidate the mysteries of this ancient organelle in order to treat it therapeutically when needed. Mitochondrial DNA mutations, infections, aging, and a lack of physical activity have been identified to be major players in mitochondrial dysfunction in multiple diseases. This review examines the complexities of mitochondrial function, whose ancient incorporation into eukaryotic cells for energy purposes was key for the survival and creation of new species. Among these complexities, the tightly intertwined bioenergetics derived from the combustion of alimentary substrates and oxygen are necessary for cellular homeostasis, including the production of reactive oxygen species. This review discusses different etiological mechanisms by which mitochondria could become dysregulated, determining the fate of multiple tissues and organs and being a protagonist in the pathogenesis of many non-communicable diseases. Finally, physical activity is a canonical evolutionary characteristic of humans that remains embedded in our genes. The normalization of a lack of physical activity in our modern society has led to the perception that exercise is an "intervention". However, physical activity remains the modus vivendi engrained in our genes and being sedentary has been the real intervention and collateral effect of modern societies. It is well known that a lack of physical activity leads to mitochondrial dysfunction and, hence, it probably becomes a major etiological factor of many non-communicable diseases affecting modern societies. Since physical activity remains the only stimulus we know that can improve and maintain mitochondrial function, a significant emphasis on exercise promotion should be imperative in order to prevent multiple diseases. Finally, in populations with chronic diseases where mitochondrial dysfunction is involved, an individualized exercise prescription should be crucial for the "metabolic rehabilitation" of many patients. From lessons learned from elite athletes (the perfect human machines), it is possible to translate and apply multiple concepts to the betterment of populations with chronic diseases.

Different eccentric-based power training volumes improve glycemic, lipidemic profile and body composition of females in a dose-dependent manner: Associations with muscle fibres composition adaptations

The present study aimed to investigate the effect of different volumes of fast eccentric-based training on body composition and lipidemic-glycemic profiles in females, as well as to explore the relationship between the change in glycemic-lipidemic profiles and the change in muscle fibre composition. Twenty-nine young females were assigned into three groups and performed 10 weeks (2 training sessions per week) of either 3 (LV), 6 (MV) or 9 (HV) sets/session of four fast velocity eccentric-only half-squats against 70% of concentric 1RM, followed by 3 maximum countermovement jumps (CMJ) after each set. Body composition, vastus lateralis fibre-type composition, and resting blood lipidemic and glycemic indices were evaluated 1 week before and after the training intervention. Significant changes in body composition, fasting glucose, HOMA-IR and blood lipids were found after training with MV and HV (p < 0.05; η2: 0.135-0.390). Significant correlations were found between muscle fibres' percentage cross-sectional areas (%CSA) and resting glycemic-lipid values (r:-0.543to 0.730, p < 0.05). Training-induced changes of glycemic-lipid profiles were highly correlated to those of type IIa and IIx %CSAs (r: -0.895 to 0.898, p < 0.05). Partial Correlations revealed a significant impact of the imposed training volumes on these correlations. These results suggest that six but mostly nine sets per training session of the imposed training stimuli are needed for beneficial changes in resting glycemic-lipidemic profiles, changes which are related to the training-induced changes in muscle fibre composition. However, these relationships are dictated by the imposed training volumes.Highlights Power training induces beneficial changes in body composition, glycemic and lipidemic profiles.Greater training volumes are needed for the healthier changes in glycemic-lipidemic profiles.Higher Type I, IIA and lower IIX percentage cross-sectional areas are linked with healthier body composition and glycemic-lipidemic profiles.Individuals experiencing the greatest increase in Type IIa and decrease in Type IIX muscle fibres cross-sectional areas after power training are those with the greatest beneficial changes in body composition, glycemic and lipidemic profiles.

AdipoRon enhances healthspan in middle-aged obese mice: striking alleviation of myosteatosis and muscle degenerative markers

BACKGROUND

Obesity among older adults has increased tremendously. Obesity accelerates ageing and predisposes to age-related conditions and diseases, such as loss of endurance capacity, insulin resistance and features of the metabolic syndrome. Namely, ectopic lipids play a key role in the development of nonalcoholic fatty liver disease (NAFLD) and myosteatosis, two severe burdens of ageing and metabolic diseases. Adiponectin (ApN) is a hormone, mainly secreted by adipocytes, which exerts insulin-sensitizing and fat-burning properties in several tissues including the liver and the muscle. Its overexpression also increases lifespan in mice. In this study, we investigated whether an ApN receptor agonist, AdipoRon (AR), could slow muscle dysfunction, myosteatosis and degenerative muscle markers in middle-aged obese mice. The effects on myosteatosis were compared with those on NAFLD.

METHODS

Three groups of mice were studied up to 62 weeks of age: One group received normal diet (ND), another, high-fat diet (HFD); and the last, HFD combined with AR given orally for almost 1 year. An additional group of young mice under an ND was used. Treadmill tests and micro-computed tomography (CT) were carried out in vivo. Histological, biochemical and molecular analyses were performed on tissues ex vivo. Bodipy staining was used to assess intramyocellular lipid (IMCL) and lipid droplet morphology.

RESULTS

AR did not markedly alter diet-induced obesity. Yet, this treatment rescued exercise endurance in obese mice (up to 2.4-fold, P < 0.05), an event that preceded the improvement of insulin sensitivity. Dorsal muscles and liver densities, measured by CT, were reduced in obese mice (-42% and -109%, respectively, P < 0.0001), suggesting fatty infiltration. This reduction tended to be attenuated by AR. Accordingly, AR significantly mitigated steatosis and cellular ballooning at liver histology, thereby decreasing the NALFD activity score (-30%, P < 0.05). AR also strikingly reversed IMCL accumulation either due to ageing in oxidative fibres (types 1/2a, soleus) or to HFD in glycolytic ones (types 2x/2b, extensor digitorum longus) (-50% to -85%, P < 0.05 or less). Size of subsarcolemmal lipid droplets, known to be associated with adverse metabolic outcomes, was reduced as well. Alleviation of myosteatosis resulted from improved mitochondrial function and lipid oxidation. Meanwhile, AR halved aged-related accumulation of dysfunctional proteins identified as tubular aggregates and cylindrical spirals by electron microscopy (P < 0.05).

CONCLUSIONS

Long-term AdipoRon treatment promotes 'healthy ageing' in obese middle-aged mice by enhancing endurance and protecting skeletal muscle and liver against the adverse metabolic and degenerative effects of ageing and caloric excess.

Effect of aerobic exercise and low-carbohydrate high-fat diet on glucose tolerance and android/gynoid fat in overweight/obese women: A randomized controlled trial

The study was designed to compare the effects of weight loss induced by a low-carbohydrate-high-fat diet or a normal diet, with and without exercise, on glucose tolerance measured as area under the curve (AUC), and android (A) and gynoid (G) fat distribution. The study was registered at clinicaltrials.gov; NCT04100356. In total, 57 women classified as overweight or obese (age 40 ± 3.5 years, body mass index 31.1 ± 2.6 kg/m²) were randomly assigned and completed a 10-week intervention using a low-carbohydrate high-fat diet or a normal diet, with or without aerobic interval exercise. An equal deficit of 700 kcal/day was prescribed, either restricting the diet only, or moderately restricting diet and including three 50-min high-intensity bicycle sessions per week. There were thus four groups: normal diet (NORM); low-carbohydrate-high-fat diet (LCHF); normal diet with exercise (NORM-EX); and low-carbohydrate-high-fat diet with exercise (LCHF-EX). Linear mixed models was used to assess differences between groups. With all groups pooled, the intervention resulted in a weight loss of 6.7 ± 2.5% (p < 0.001). The intervention did not result in differences between groups in AUC glucose, nor in fasting glucose or indicis for insulin resistance such as Homeostatic Model Assessment, Matsuda Insulin Sensitivity Index, insulinogenic index and disposition index. Post-intervention android fat was lower in LCHF than NORM (3,223 ± 727 vs. 2,533 ± 535 g, p = 0.041). LCHF reached a lower A/G ratio than NORM (0.94 ± 0.12 vs. 1.04 ± 0.09, p = 0.011) and LCHF-EX (0.94 ± 0.12 vs. 1.09 ± 0.09, p < 0.001) after the intervention. LCHF resulted in lower android fat mass compared to NORM and the lowest A/G ratio compared to the other matched groups, but with no accompanying improvement in AUC glucose. In conclusion, although all groups achieved improvements in glucose tolerance, no superior effect was observed with the LCHF diet, neither with nor without exercise.

Altered intramuscular network of lipid droplets and mitochondria in type 2 diabetes

Excessive storage of lipid droplets (LDs) in skeletal muscles is a hallmark of type 2 diabetes. However, LD morphology displays a high degree of subcellular heterogeneity and varies between single muscle fibers, which impedes the current understanding of lipid-induced insulin resistance. Using quantitative transmission electron microscopy (TEM), we conducted a comprehensive single-fiber morphological analysis to investigate the intramuscular network of LDs and mitochondria, and the effects of 8 wk of high-intensity interval training (HIIT) targeting major muscle groups, in patients with type 2 diabetes and nondiabetic obese and lean controls. We found that excessive storage of intramuscular lipids in patients with type 2 diabetes was exclusively explained by extremely large LDs situated in distinct muscle fibers with a location-specific deficiency in subsarcolemmal mitochondria. After HIIT, this intramuscular deficiency was improved by a remodeling of LD size and subcellular distribution and mitochondrial content. Analysis of LD morphology further revealed that individual organelles were better described as ellipsoids than spheres. Moreover, physical contact between LD and mitochondrial membranes indicated a dysfunctional interplay between organelles in the diabetic state. Taken together, type 2 diabetes should be recognized as a metabolic disease with high cellular heterogeneity in intramuscular lipid storage, underlining the relevance of single-cell technologies in clinical research. Furthermore, HIIT changed intramuscular LD storage toward nondiabetic characteristics.

Metabolomic profiling reveals muscle metabolic changes following iliac arteriovenous fistula creation in mice

End-stage kidney disease, the most advanced stage of chronic kidney disease (CKD), requires renal replacement therapy or kidney transplant to sustain life. To accomplish durable dialysis access, the creation of an arteriovenous fistula (AVF) has emerged as a preferred approach. Unfortunately, a significant proportion of patients that receive an AVF experience some form of hand dysfunction; however, the mechanisms underlying these side effects are not understood. In this study, we used nuclear magnetic resonance spectroscopy to investigate the muscle metabolome following iliac AVF placement in mice with CKD. To induce CKD, C57BL6J mice were fed an adenine-supplemented diet for 3 wk and then randomized to receive AVF or sham surgery. Two weeks following surgery, the quadriceps muscles were rapidly dissected and snap frozen for metabolite extraction and subsequent nuclear magnetic resonance analysis. Principal component analysis demonstrated clear separation between groups, confirming a unique metabolome in mice that received an AVF. AVF creation resulted in reduced levels of creatine, ATP, and AMP as well as increased levels of IMP and several tricarboxylic acid cycle metabolites suggesting profound energetic stress. Pearson correlation and multiple linear regression analyses identified several metabolites that were strongly linked to measures of limb function (grip strength, gait speed, and mitochondrial respiration). In summary, AVF creation generates a unique metabolome profile in the distal skeletal muscle indicative of an energetic crisis and myosteatosis.NEW & NOTEWORTHY Creation of an arteriovenous fistula (AVF) is the preferred approach for dialysis access, but some patients experience hand dysfunction after AVF creation. In this study, we provide a detailed metabolomic analysis of the limb muscle in a murine model of AVF. AVF creation resulted in metabolite changes associated with an energetic crisis and myosteatosis that associated with limb function.

Food odor perception promotes systemic lipid utilization

Food cues during fasting elicit Pavlovian conditioning to adapt for anticipated food intake. However, whether the olfactory system is involved in metabolic adaptations remains elusive. Here we show that food-odor perception promotes lipid metabolism in male mice. During fasting, food-odor stimulation is sufficient to increase serum free fatty acids via adipose tissue lipolysis in an olfactory-memory-dependent manner, which is mediated by the central melanocortin and sympathetic nervous systems. Additionally, stimulation with a food odor prior to refeeding leads to enhanced whole-body lipid utilization, which is associated with increased sensitivity of the central agouti-related peptide system, reduced sympathetic activity and peripheral tissue-specific metabolic alterations, such as an increase in gastrointestinal lipid absorption and hepatic cholesterol turnover. Finally, we show that intermittent fasting coupled with food-odor stimulation improves glycemic control and prevents insulin resistance in diet-induced obese mice. Thus, olfactory regulation is required for maintaining metabolic homeostasis in environments with either an energy deficit or energy surplus, which could be considered as part of dietary interventions against metabolic disorders.

Application of FTIR Spectroscopy to Detect Changes in Skeletal Muscle Composition Due to Obesity with Insulin Resistance and STZ-Induced Diabetes

Age, obesity, and diabetes mellitus are pathophysiologically interconnected factors that significantly contribute to the global burden of non-communicable diseases. These metabolic conditions are associated with impaired insulin function, which disrupts the metabolism of carbohydrates, lipids, and proteins and can lead to structural and functional changes in skeletal muscle. Therefore, the alterations in the macromolecular composition of skeletal muscle may provide an indication of the underlying mechanisms of insulin-related disorders. The aim of this study was to investigate the potential of Fourier transform infrared (FTIR) spectroscopy to reveal the changes in macromolecular composition in weight-bearing and non-weight-bearing muscles of old, obese, insulin-resistant, and young streptozotocin (STZ)-induced diabetic mice. The efficiency of FTIR spectroscopy was evaluated by comparison with the results of gold-standard histochemical techniques. The differences in biomolecular phenotypes and the alterations in muscle composition in relation to their functional properties observed from FTIR spectra suggest that FTIR spectroscopy can detect most of the changes observed in muscle tissue by histochemical analyses and more. Therefore, it could be used as an effective alternative because it allows for the complete characterization of macromolecular composition in a single, relatively simple experiment, avoiding some obvious drawbacks of histochemical methods.

Galectin-1 in Obesity and Type 2 Diabetes

Galectin-1 is a carbohydrate-binding protein expressed in many tissues. In recent years, increasing evidence has emerged for the role of galectin-1 in obesity, insulin resistance and type 2 diabetes. Galectin-1 has been highly conserved through evolution and is involved in key cellular functions such as tissue maturation and homeostasis. It has been shown that galectin-1 increases in obesity, both in the circulation and in the adipose tissue of human and animal models. Several proteomic studies have independently identified an increased galectin-1 expression in the adipose tissue in obesity and in insulin resistance. Large population-based cohorts have demonstrated associations for circulating galectin-1 and markers of insulin resistance and incident type 2 diabetes. Furthermore, galectin-1 is associated with key metabolic pathways including glucose and lipid metabolism, as well as insulin signalling and inflammation. Intervention studies in animal models alter animal weight and metabolic profile. Several studies have also linked galectin-1 to the progression of complications in diabetes, including kidney disease and retinopathy. Here, we review the current knowledge on the clinical potential of galectin-1 in obesity and type 2 diabetes.

Exercise, aerobic fitness, and muscle strength in relation to glucose tolerance 6 to 10 years after gestational diabetes

AIMS

We sought to identify self-reported exercise and objectively measured fitness variables associated with glucose tolerance and metabolic health 6-10 years after gestational diabetes (GDM) METHODS: Women (n = 84) underwent oral glucose tolerance testing (OGTT), body composition measurements, and lifestyle questionnaires 6 and 10 years after GDM. In a subset (n = 45), peak oxygen uptake (VO_2peak), peak fat oxidation, and maximal isometric strength of five muscle groups were tested.

RESULTS

At 10 years, 41 women (49%) had impaired glucose metabolism or type 2 diabetes (T2D). VO_2peak and muscle strength were lowest in the T2D group. In a regression analysis, VO_2peak and all strength measurements were associated negatively with HbA1c and waist-hip ratio and positively with high-density lipoprotein cholesterol. However, only muscle strength was associated with fasting and area-under-the-curve glucose. For changes between the 6- and 10-year follow-ups, only muscle strength was associated with HbA1c change, whereas both VO_2peak and strength were associated with high-density lipoprotein level and changes in waist-hip ratio. Peak fat oxidation and self-reported physical activity showed no or weak relationships with glycemic variables.

CONCLUSION

Objectively measured fitness variables, particularly muscle strength, were strongly associated with glycemic and other metabolic outcomes in a high-risk group after GDM.

Exercise training enhances muscle mitochondrial metabolism in diet-resistant obesity

Background

Current paradigms for predicting weight loss in response to energy restriction have general validity but a subset of individuals fail to respond adequately despite documented diet adherence. Patients in the bottom 20% for rate of weight loss following a hypocaloric diet (diet-resistant) have been found to have less type I muscle fibres and lower skeletal muscle mitochondrial function, leading to the hypothesis that physical exercise may be an effective treatment when diet alone is inadequate. In this study, we aimed to assess the efficacy of exercise training on mitochondrial function in women with obesity with a documented history of minimal diet-induced weight loss.

Methods

From over 5000 patient records, 228 files were reviewed to identify baseline characteristics of weight loss response from women with obesity who were previously classified in the top or bottom 20% quintiles based on rate of weight loss in the first 6 weeks during which a 900 kcal/day meal replacement was consumed. A subset of 20 women with obesity were identified based on diet-resistance (n=10) and diet sensitivity (n=10) to undergo a 6-week supervised, progressive, combined aerobic and resistance exercise intervention.

Findings

Diet-sensitive women had lower baseline adiposity, higher fasting insulin and triglycerides, and a greater number of ATP-III criteria for metabolic syndrome. Conversely in diet-resistant women, the exercise intervention improved body composition, skeletal muscle mitochondrial content and metabolism, with minimal effects in diet-sensitive women. In-depth analyses of muscle metabolomes revealed distinct group- and intervention- differences, including lower serine-associated sphingolipid synthesis in diet-resistant women following exercise training.

Interpretation

Exercise preferentially enhances skeletal muscle metabolism and improves body composition in women with a history of minimal diet-induced weight loss. These clinical and metabolic mechanism insights move the field towards better personalised approaches for the treatment of distinct obesity phenotypes.

Funding

Canadian Institutes of Health Research (CIHR-INMD and FDN-143278; CAN-163902; CIHR PJT-148634).

Exercise ameliorates high-fat diet-induced insulin resistance accompanied by changes in protein levels of hepatic ATF3-related signaling in rats

PURPOSE

Exercise is an effective way to alleviate insulin resistance (IR). However, the underlying mechanisms remain to be elucidated. Previous studies demonstrated that cardiolipin synthase 1 (CRLS1)/interferon-regulatory factor-2 binding protein 2 (IRF2bp2)-activating transcription factor 3 (ATF3)-adiponectin receptor 2 (AdipoR2)-adaptor protein containing pH domain, PTB domain and leucine zipper motif 1 (APPL1)-protein kinase B (AKT/PKB)-related signaling was closely associated with obesity-induced IR-related diseases, but the correlation between exercise training alleviating obesity-induced IR and the protein levels of hepatic CRLS1/IRF2bp2-ATF3-AdipoR2-APPL1-AKT-related signaling in rats is unknown. Therefore, We want to investigate the effect of exercise training on IR and the protein levels of hepatic CRLS1/IRF2bp2-ATF3-AdipoR2-APPL1-AKT-related signaling in rat.

METHODS

The male healthy Sprague-Dawley rats were divided into four groups: normal control group (NCG, n = 10), diet-induced obesity-sedentary group (DIO-SG, n = 10), diet-induced obesity-chronic exercise group (DIOCEG, n = 10) received chronic swim exercise training and diet-induced obesity-acute exercise group (DIO-AEG, n = 10) received acute swim exercise training. We measured the levels of IR-related indicators and the protein levels of hepatic CRLS1/IRF2bp2-ATF3-AdipoR2-APPL1-AKT-related signaling in NCG, DIO-SG, DIOCEG and DIO-AEG.

RESULTS

We found that high-fat diet (HFD)-induced obesity decreased insulin sensitivity in rats accompanied by decreased protein levels of hepatic CRLS1, IRF2bp2, AdipoR2, APPL1, p-AKT and increased protein level of hepatic ATF3. The acute exercise and the chronic exercise both increased insulin sensitivity in rats. The chronic exercise decreased hepatic ATF3 protein level and increased CRLS1, IRF2bp2, AdipoR2, APPL1, p-AKT protein levels in HFD-fed rats. The acute exercise decreased hepatic ATF3 protein level and increased hepatic IRF2bp2, APPL1 and p-AKT protein levels in HFD-fed rats. The acute exercise had no significant effect on hepatic CRLS1 and AdipoR2 protein levels in HFD-fed rats.

CONCLUSION

Our current findings indicated that exercise alleviated obesity-induced IR accompanied by changes in protein levels of hepatic ATF3-related signaling in rats. Our results are meaningful for exploring the molecular mechanism of exercise alleviating IR symptoms.

High intramuscular triglyceride turnover rates and the link to insulin sensitivity: influence of obesity, type 2 diabetes and physical activity

Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance is caused, at least in part, by the presence of high concentrations of harmful lipid metabolites, such as diacylglycerols and ceramides in muscle. Several mechanistic differences between obese sedentary individuals and their highly trained counterparts have been identified, which determine the differential capacity for IMTG synthesis and breakdown in these populations. In this review, we first describe the most up-to-date mechanisms by which a low IMTG turnover rate (both breakdown and synthesis) leads to the accumulation of lipid metabolites and results in skeletal muscle insulin resistance. We then explore current and potential exercise and nutritional strategies that target IMTG turnover in sedentary obese individuals, to improve insulin sensitivity. Overall, improving IMTG turnover should be an important component of successful interventions that aim to prevent the development of insulin resistance in the ever-expanding sedentary, overweight and obese populations. Novelty: A description of the most up-to-date mechanisms regulating turnover of the IMTG pool. An exploration of current and potential exercise/nutritional strategies to target and enhance IMTG turnover in obese individuals. Overall, highlights the importance of improving IMTG turnover to prevent the development of insulin resistance.

Exercise regulation of hepatic lipid droplet metabolism

Lipid droplets (LD) are not just lipid stores. They are now recognized as highly dynamic organelles, having a life cycle that includes biogenesis, growth, steady-state, transport, and catabolism. Importantly, LD exhibit different features in terms of size, number, lipid composition, proteins, and interaction with other organelles, and all these features exert an impact on cellular homeostasis. The imbalance of LD function causes non-alcoholic fatty liver disease (NAFLD). Studies show that exercise attenuates NAFLD by decreasing LD content; however, reports show metabolic benefits without changes in LD amount (intrahepatic triglyceride levels) in NAFLD. Due to the multiple effects of exercise in LD features, we think that these metabolic benefits occur through changes in LD features in NAFLD, rather than only the reduction in content. Exercise increases energy mobilization and utilization from storages such as LD, and is one of the non-pharmacological treatments against NAFLD. Therefore, exercise modification of LD could be a target for NAFLD treatment. Here, we review the most up-to-date literature on this topic, and focus on recent findings showing that LD features could play an important role in the severity of NAFLD.

Glucose Uptake by Skeletal Muscle within the Contexts of Type 2 Diabetes and Exercise: An Integrated Approach

Type 2 diabetes continues to negatively impact the health of millions. The inability to respond to insulin to clear blood glucose (insulin resistance) is a key pathogenic driver of the disease. Skeletal muscle is the primary tissue for maintaining glucose homeostasis through glucose uptake via insulin-dependent and -independent mechanisms. Skeletal muscle is also responsive to exercise-meditated glucose transport, and as such, exercise is a cornerstone for glucose management in people with type 2 diabetes. Skeletal muscle glucose uptake requires a concert of events. First, the glucose-rich blood must be transported to the skeletal muscle. Next, the glucose must traverse the endothelium, extracellular matrix, and skeletal muscle membrane. Lastly, intracellular metabolic processes must be activated to maintain the diffusion gradient to facilitate glucose transport into the cell. This review aims to examine the physiology at each of these steps in healthy individuals, analyze the dysregulation affecting these pathways associated with type 2 diabetes, and describe the mechanisms by which exercise acts to increase glucose uptake.

Acute and chronic effects of high-intensity interval training (HIIT) on postexercise intramuscular lipid metabolism in rats

Recovery from exercise refers to the period between the end of a bout of exercise and the subsequent return to a resting or recovered state. It is a dynamic period in which many physiological changes occur. A large amount of research has evaluated the effect of training on intramuscular lipid metabolism. However, data are limited regarding intramuscular lipid metabolism during the recovery period. In this study, lipid metabolism-related proteins were examined after a single bout of exercise in a time-dependent way to explore the mechanism of how exercise induces intramuscular lipid metabolism adaptation. Firstly, all rats in the exercise group underwent a five-week training protocol (HIIT, five times/week), and then performed a more intense HIIT session after 72 h of the last-time five-week training. After that, rats were sampled in a time-dependent way, including 0 h, 6 h, 12 h, 24 h, 48 h, 72 h, and 96 h following the acute training session. Our results discovered that five weeks of HIIT increased the content of intramuscular triglyceride (IMTG) and enhanced the lipolytic and lipogenesis-related proteins in skeletal muscle. Furthermore, IMTG content decreased immediately post HIIT and gradually increased to baseline levels 48 h postexercise, continuing to over-recover up to 96 h postexercise. Following acute exercise, lipolytic-related proteins showed an initial increase (6-12 h) before decreasing during recovery. Conversely, lipogenesis-related proteins decreased following exercise (6-12 h), then increased in the recovery period. Based on the changes, we speculate that skeletal muscle is predominated by lipid oxidative at the first 12 h postexercise. After this period, lipid synthesis-related proteins increased, which may be the result of body recovery. Together, these results may provide insight into how the lipid metabolism-related signaling changes after chronic and acute HIIT and how protein levels lipid metabolism correlates to IMTG recovery.

NLRP3 Inflammasome: Potential Role in Obesity Related Low-Grade Inflammation and Insulin Resistance in Skeletal Muscle

Among multiple mechanisms, low-grade inflammation is critical for the development of insulin resistance as a feature of type 2 diabetes. The nucleotide-binding oligomerization domain-like receptor family (NOD-like) pyrin domain containing 3 (NLRP3) inflammasome has been linked to the development of insulin resistance in various tissues; however, its role in the development of insulin resistance in the skeletal muscle has not been explored in depth. Currently, there is limited evidence that supports the pathological role of NLRP3 inflammasome activation in glucose handling in the skeletal muscle of obese individuals. Here, we have centered our focus on insulin signaling in skeletal muscle, which is the main site of postprandial glucose disposal in humans. We discuss the current evidence showing that the NLRP3 inflammasome disturbs glucose homeostasis. We also review how NLRP3-associated interleukin and its gasdermin D-mediated efflux could affect insulin-dependent intracellular pathways. Finally, we address pharmacological NLRP3 inhibitors that may have a therapeutical use in obesity-related metabolic alterations.

Physical Exercise and Alzheimer's Disease: Effects on Pathophysiological Molecular Pathways of the Disease

Alzheimer’s disease (AD), the most common form of neurodegenerative dementia in adults worldwide, is a multifactorial and heterogeneous disorder characterized by the interaction of genetic and epigenetic factors and the dysregulation of numerous intracellular signaling and cellular/molecular pathways. The introduction of the systems biology framework is revolutionizing the study of complex diseases by allowing the identification and integration of cellular/molecular pathways and networks of interaction. Here, we reviewed the relationship between physical activity and the next pathophysiological processes involved in the risk of developing AD, based on some crucial molecular pathways and biological process dysregulated in AD: (1) Immune system and inflammation; (2) Endothelial function and cerebrovascular insufficiency; (3) Apoptosis and cell death; (4) Intercellular communication; (5) Metabolism, oxidative stress and neurotoxicity; (6) DNA damage and repair; (7) Cytoskeleton and membrane proteins; (8) Synaptic plasticity. Moreover, we highlighted the increasingly relevant role played by advanced neuroimaging technologies, including structural/functional magnetic resonance imaging, diffusion tensor imaging, and arterial spin labelling, in exploring the link between AD and physical exercise. Regular physical exercise seems to have a protective effect against AD by inhibiting different pathophysiological molecular pathways implicated in AD.

Extracellular ATP Increases Glucose Metabolism in Skeletal Muscle Cells in a P2 Receptor Dependent Manner but Does Not Contribute to Palmitate-Induced Insulin Resistance

Saturated fatty acids such as palmitate contribute to the development of Type 2 Diabetes by reducing insulin sensitivity, increasing inflammation and potentially contributing to anabolic resistance. We hypothesized that palmitate-induced ATP release from skeletal muscle cells may increase inflammatory cytokine production and contribute to insulin/anabolic resistance in an autocrine/paracrine manner. In C2C12 myotubes differentiated at physiological glucose concentrations (5.5 mM), palmitate treatment (16 h) at concentrations greater than 250 μM increased release of ATP and inflammatory cytokines IL-6 and MIF, significantly blunted insulin and amino acid-induced signaling and reduced mitochondrial function. In contrast to our hypothesis, degradation of extracellular ATP using apyrase, did not alter palmitate-induced insulin resistance nor alter release of cytokines. Moreover, treatment with ATPγS (16 h), a non-hydrolysable ATP analog, in the absence of palmitate, did not diminish insulin sensitivity. Acute treatment with ATPγS produced insulin mimetic roles; increased phosphorylation of PKB (aka AKT), S6K1 and ERK and enhanced GLUT4-mediated glucose uptake in the absence of exogenous insulin. The increases in PKB and S6K1 phosphorylation were completely prevented by pre-incubation with broad spectrum purinergic receptor (P2R) blockers PPADs and suramin but not by P2 × 4 or P2 × 7 blockers 5-BDBD or A-438079, respectively. Moreover, ATPγS increased IL-6 yet decreased MIF release, similar to the cytokine profile produced by exercise. Acute and chronic treatment with ATPγS increased glycolytic rate in a manner that was differentially inhibited by PPADs and suramin, suggesting heterogeneous P2R activation in the control of cellular metabolism. In summary, our data suggest that the palmitate-induced increase in ATP does not contribute to insulin/anabolic resistance in a cell autonomous manner.

Antidiabetic Effects of Physical Activity: How It Helps to Control Type 2 Diabetes

Despite the improvements in clinical care of the patients, research updates, and public health interventions, there is still an increase in the prevalence, incidence, and mortality because of diabetes mellitus (DM). DM is a public health problem in both developed and developing countries. It has increased alarmingly, putting this disease in the dimension of an epidemic. Diabetes is associated with several complications which increase the risk of many serious health problems on the other side. Therefore, this review was aimed to discuss the antidiabetic effects of physical activity (PA) on type 2 DM (T2DM) by summarizing the significant studies on this topic. This review found that several studies have recommended the utilization of PA for the effective management of T2DM. PA is a non-pharmacologic therapy which is a significant strategy for the management of T2DM and is an appropriate lifestyle modification approach to be practiced by these patients. The studies showed that PA has antidiabetic effects which are evidenced by its substantial role in improving the blood glucose (BG) levels of the individuals with T2DM where it helps them to control their levels of glucose in the blood. It plays a significant role in glycemic control of this disease by lowering the BG levels through possible mechanisms such as decreasing insulin resistance, increasing production of glucose transporter type 4 (GLUT-4), lowering visceral adipose tissue (VAT), increasing pancreatic β-cell functions, using glucose for energy, and so on. In turn, the controlled glycemia helps to prevent the complications associated with uncontrolled T2DM and this would further improve the overall health of the patients and the burden on the health professionals as well. Finally, this review concludes that PA is the cornerstone in the management of T2DM. It also suggests that more attention is needed to its significance in the prevention, glycemic control, and its role in the management of the morbidity and mortality associated with T2DM. Practical PA recommendations and suggestions for the future direction of research in this area are also provided.

Inflammation and metabolism: the role of adiposity in sarcopenic obesity

Sarcopenic obesity is characterised by the double burden of diminished skeletal muscle mass and the presence of excess adiposity. From a mechanistic perspective, both obesity and sarcopenia are associated with sub-acute, chronic pro-inflammatory states that impede metabolic processes, disrupting adipose and skeletal functionality, which may potentiate disease. Recent evidence suggests that there is an important cross-talk between metabolism and inflammation, which has shifted focus upon metabolic-inflammation as a key emerging biological interaction. Dietary intake, physical activity and nutritional status are important environmental factors that may modulate metabolic-inflammation. This paradigm will be discussed within the context of sarcopenic obesity risk. There is a paucity of data in relation to the nature and the extent to which nutritional status affects metabolic-inflammation in sarcopenic obesity. Research suggests that there may be scope for the modulation of sarcopenic obesity with alterations in diet. The potential impact of increasing protein consumption and reconfiguration of dietary fat composition in human dietary interventions are evaluated. This review will explore emerging data with respect to if and how different dietary components may modulate metabolic-inflammation, particularly with respect to adiposity, within the context of sarcopenic obesity.