Effects of 7 days of exercise training on insulin sensitivity and responsiveness in type 2 diabetes mellitus

Exercise as a tool to mitigate metabolic disease

Metabolic diseases, notably obesity and type 2 diabetes (T2D), have reached alarming proportions and constitute a significant global health challenge, emphasizing the urgent need for effective preventive and therapeutic strategies. In contrast, exercise training emerges as a potent intervention, exerting numerous positive effects on metabolic health through adaptations to the metabolic tissues. Here, we reviewed the major features of our current understanding with respect to the intricate interplay between metabolic diseases and key metabolic tissues, including adipose tissue, skeletal muscle, and liver, describing some of the main underlying mechanisms driving pathogenesis, as well as the role of exercise to combat and treat obesity and metabolic disease.

Mechanism underlying the effects of exercise against type 2 diabetes: A review on research progress

Exercise has emerged as one of the important and effective non-drug therapies used for management of type 2 diabetes (T2D) in certain nations. The present report summarizes the latest findings from the research on the beneficial effect of exercise on T2D. The objectives were to provide references for the theoretical study and the clinical practice of exercise-based management of T2D, in addition to identify the limitations of the existing literature, thereby provide direction for future research in this field.

Alternative therapeutic strategies in diabetes management

Diabetes is a heterogeneous metabolic disease characterized by elevated blood glucose levels resulting from the destruction or malfunction of pancreatic β cells, insulin resistance in peripheral tissues, or both, and results in a non-sufficient production of insulin. To adjust blood glucose levels, diabetic patients need exogenous insulin administration together with medical nutrition therapy and physical activity. With the aim of improving insulin availability in diabetic patients as well as ameliorating diabetes comorbidities, different strategies have been investigated. The first approaches included enhancing endogenous β cell activity or transplanting new islets. The protocol for this kind of intervention has recently been optimized, leading to standardized procedures. It is indicated for diabetic patients with severe hypoglycemia, complicated by impaired hypoglycemia awareness or exacerbated glycemic lability. Transplantation has been associated with improvement in all comorbidities associated with diabetes, quality of life, and survival. However, different trials are ongoing to further improve the beneficial effects of transplantation. Furthermore, to overcome some limitations associated with the availability of islets/pancreas, alternative therapeutic strategies are under evaluation, such as the use of mesenchymal stem cells (MSCs) or induced pluripotent stem cells for transplantation. The cotransplantation of MSCs with islets has been successful, thus providing protection against proinflammatory cytokines and hypoxia through different mechanisms, including exosome release. The use of induced pluripotent stem cells is recent and requires further investigation. The advantages of MSC implantation have also included the improvement of diabetes-related comorbidities, such as wound healing. Despite the number of advantages of the direct injection of MSCs, new strategies involving biomaterials and scaffolds have been developed to improve the efficacy of mesenchymal cell delivery with promising results. In conclusion, this paper offered an overview of new alternative strategies for diabetes management while highlighting some limitations that will need to be overcome by future approaches.

Exercise Training Independent of Intensity Lowers Plasma Bile Acids in Prediabetes

INTRODUCTION

People with obesity have high circulating bile acids (BA). Although aerobic fitness favors low circulating BA, the effect of training intensity before clinically meaningful weight loss on BA is unclear. This study aimed to test the hypothesis that 2 wk of interval (INT) versus continuous (CONT) exercise would lower plasma BA in relation to insulin sensitivity.

METHODS

Twenty-three older adults with prediabetes (ADA criteria) were randomized to 12 work-matched bouts of INT ( n = 11, 60.3 ± 2.4 yr, 32.1 ± 1.2 kg·m -2 ) at 3 min at 50% HR peak and 3 min at 90% HR peak or CONT ( n = 12, 60.8 ± 2.4 yr, 34.0 ± 1.7 kg·m -2 ) at 70% HR peak cycling training for 60 min·d -1 over 2 wk. A 180-min 75-g oral glucose tolerance test (OGTT) was performed to assess glucose tolerance (tAUC), insulin sensitivity (Siis), and metabolic flexibility (RER postprandial -RER fast ; indirect calorimetry). BA ( n = 8 conjugated and 7 unconjugated) were analyzed at 0, 30, and 60 min of the OGTT. Anthropometrics and fitness (V̇O 2peak ) were also assessed.

RESULTS

INT and CONT comparably reduced body mass index (BMI; P < 0.001) and fasting RER ( P < 0.001) but raised insulin sensitivity ( P = 0.03). INT increased V̇O 2peak as compared with CONT ( P = 0.01). Exercise decreased the unconjugated BA chenodeoxycholic acid iAUC 60min ( P < 0.001), deoxycholic acid iAUC 60min ( P < 0.001), lithocholic acid iAUC 60min ( P < 0.001), and glycodeoxycholic acid (GCDCA) iAUC 60min ( P < 0.001). Comparable reductions were also seen in the conjugated BA hyodeoxycholic acid iAUC 60min ( P = 0.01) and taurolithocholic acid iAUC 60min ( P = 0.007). Increased V̇O 2peak was associated with lowered UDCA 0min ( r = -0.56, P = 0.02) and cholic acid iAUC 60min ( r = -0.60, P = 0.005), whereas reduced BMI was related to higher GDCA 0min ( r = 0.60, P = 0.005) and GCDCA 0min ( r = 0.53, P = 0.01). Improved insulin sensitivity correlated with lower GCDCA iAUC 60min ( r = -0.45, P = 0.03) and GDCA iAUC 60min ( r = -0.48, P = 0.02), whereas increased metabolic flexibility was related to deoxycholic acid iAUC 60min ( r = 0.64, P = 0.004) and GCDCA iAUC 60min ( r = 0.43, P = 0.05).

CONCLUSIONS

Short-term training lowers some BA in relation to insulin sensitivity independent of intensity.

Diabetes-induced peripheral neuropathy: Is prescribing physical exercise the answer?

Diabetes mellitus, a chronic metabolic disorder characterized by hyperglycemia, has become a global health concern with an increasing prevalence worldwide. The International Diabetes Federation (IDF) estimates that over 537 million adults currently have diabetes, and they project that this figure will likely exceed 780 million by 2045. In addition, a further 541 million adults are thought to exhibit impaired glucose tolerance/prediabetes. Among its many complications, diabetic peripheral neuropathy (DPN) affects up to 50% of sufferers, with some studies showing that its prevalence, even in prediabetes, may be as high as 77%. Read more in the PDF.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

The effects of combined exercise training on glucose metabolism and inflammatory markers in sedentary adults: a systematic review and meta-analysis

This systematic review and meta-analysis aimed to determine the magnitude of the effect of combined exercise training on glucose metabolism markers, adipokines, and inflammatory cytokines in non-diabetic sedentary adults. PubMed, Web of Science, Scopus, Cochrane Library electronic databases and reference lists of included studies were explored for randomized controlled trials (RCTs) that included physically inactive adults and provided combined training interventions (aerobic plus resistance exercise). Effects on fasting glucose and insulin, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), HbA1c, adiponectin, leptin, IL-6, TNF-α, and C-reactive protein (CRP) in exercise vs control groups were analyzed using random effects meta-analysis. The Cochrane Risk of Bias Tool for Randomized Trials 2.0 (RoB 2) was used to assess the risk of bias. A total of 24 RCTs were included in the quantitative analysis. Combined exercise training significantly decrease fasting glucose (standardized mean difference, SMD: - 0.474, 95% CI [- 0.829, - 0.120], p = 0.009, 35 study arms), fasting insulin (SMD: - 1.024, 95% CI [- 1.502, - 0.545], p < 0.001, 27 study arms), HOMA-IR (SMD: - 0.946, 95% CI [- 1.450, - 0.442], p < 0.001, 23 study arms), TNF-α (SMD: - 0.972, 95% CI [- 1.361, - 0.582], p < 0.001, 10 study arms), and CRP (SMD: - 0.507, 95% CI [- 0.818, - 0.196], p = 0.001, 14 study arms). No significant effects were observed for HbA1c, adiponectin, leptin, and IL-6 levels. Random effects meta-regression models by age, sex, and intervention length were not able to explain any of the variation in the effect size of HOMA-IR. Findings from this systematic review and meta-analysis suggest that combined exercise training improves some glucose metabolism markers and inflammatory parameters in sedentary adults without diabetes.

Weight-independent effects of Roux-en-Y gastric bypass surgery on remission of nonalcoholic fatty liver disease in mice

OBJECTIVE

Obesity is a driver of non-alcoholic fatty liver disease (NAFLD), and interventions that decrease body weight, such as bariatric surgery and/or calorie restriction (CR), may serve as effective therapies. This study compared the effects of Roux-en-Y gastric bypass surgery (RYGB) and CR on hepatic function in mice with obesity and NAFLD.

METHODS

C57BL/6J mice were fed a high-fat diet to promote obesity. At 16 weeks of age, mice were randomized to sham surgery (sham), RYGB, or CR weight matched to RYGB (WM). Body weight/composition, food intake, and energy expenditure (EE) were measured throughout treatment. Liver histopathology was evaluated from H&E-stained sections. Hepatic enzymes and glycogen content were determined by ELISA. Transcriptional signatures were revealed via RNA sequencing.

RESULTS

RYGB reduced hepatic lipid content and adiposity while increasing EE and lean body mass relative to WM. Hepatic glycogen and bile acid content were increased after RYGB relative to sham and WM. RYGB activated enterohepatic signaling and genes regulating hepatic lipid homeostasis.

CONCLUSIONS

RYGB improved whole-body composition and hepatic lipid homeostasis to a greater extent than CR in mice. RYGB was associated with discrete remodeling of the hepatic transcriptome, suggesting that surgery may be mechanistically additive to CR.

Non-drug interventions of traditional Chinese medicine in preventing type 2 diabetes: a review

Traditional Chinese medicine (TCM) is increasingly used to manage type 2 diabetes and its nonpharmacological interventions are showing potential for preventing type 2 diabetes. This study mainly reviews relevant research. The most mentioned non-drug treatments for preventing type 2 diabetes in TCM are healthy diet, physical activity, emotional therapy, and acupuncture. In most studies, blood glucose status in patients with prediabetes and type 2 diabetes was significantly improved after TCM non-drug interventions, and there was no significant difference between the adverse effect of TCM and control groups or other intervention groups, while the methodological quality of the clinical trials involving TCM generally kept a low level. The effectiveness of TCM in preventing type 2 diabetes has yet to be validated in large randomized controlled trials and the underlying mechanism also needs further exploration.

Effect of Exercise on Liver Function and Insulin Resistance Markers in Patients with Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Structured exercise as part of lifestyle modification plays an important role in the improvement of non-alcoholic fatty liver disease (NAFLD); however, its effectiveness has been shown to vary. This systematic review with meta-analysis investigated the effects of exercise on liver function and insulin resistance markers in patients with NAFLD.

METHODS

Six electronic databases were searched using terms related to exercise and NAFLD up to March 2022. Data were analyzed using a random-effects model to estimate the standardized mean difference (SMD) and 95% confidence interval.

RESULTS

The systematic search identified 2583 articles, of which a total of 26 studies met the inclusion criteria and were eligible. Exercise training had a moderate effect on reducing ALT (SMD: -0.59, p = 0.01) and small effects on reducing AST (SMD: -0.40, p = 0.01) and insulin (SMD: -0.43, p = 0.02). Significant reductions in ALT were found following aerobic training (SMD: -0.63, p < 0.01) and resistance training (SMD: -0.45, p < 0.001). Moreover, reductions in AST were found following resistance training (SMD: -0.54, p = 0.001), but not after aerobic training and combined training. However, reductions in insulin were found following aerobic training (SMD: -0.55, p = 0.03). Exercise interventions for <12 weeks compared to ≥12 weeks were more effective in reducing FBG and HOMA-IR, while interventions for ≥12 weeks compared to <12 weeks were more effective in reducing ALT and AST levels.

CONCLUSIONS

Our findings support the effectiveness of exercise in improving liver function markers but not in blood glucose control in NAFLD patients. Additional studies are needed to determine the exercise prescription to maximize health in these patients.

Comprehensive Approach to Medical Nutrition Therapy in Patients with Type 2 Diabetes Mellitus: From Diet to Bioactive Compounds

In the pathogenesis of type 2 diabetes mellitus (T2DM), diet plays a key role. Individualized medical nutritional therapy, as part of lifestyle optimization, is one of the cornerstones for the management of T2DM and has been shown to improve metabolic outcomes. This paper discusses major aspects of the nutritional intervention (including macro- and micronutrients, nutraceuticals, and supplements), with key practical advice. Various eating patterns, such as the Mediterranean-style, low-carbohydrate, vegetarian or plant-based diets, as well as healthy eating plans with caloric deficits have been proven to have beneficial effects for patients with T2DM. So far, the evidence does not support a specific macronutrient distribution and meal plans should be individualized. Reducing the overall carbohydrate intake and replacing high glycemic index (GI) foods with low GI foods have been shown as valid options for patients with T2DM to improve glycemic control. Additionally, evidence supports the current recommendation to reduce the intake of free sugars to less than 10% of total energy intake, since their excessive intake promotes weight gain. The quality of fats seems to be rather important and the substitution of saturated and trans fatty acids with foods rich in monounsaturated and polyunsaturated fats lowers cardiovascular risk and improves glucose metabolism. There is no benefit of supplementation with antioxidants, such as carotene, vitamins E and C, or other micronutrients, due to the lack of consistent evidence showing efficacy and long-term safety. Some studies suggest possible beneficial metabolic effects of nutraceuticals in patients with T2DM, but more evidence about their efficacy and safety is still needed.

Exercise and inactivity as modifiers of β cell function and type 2 diabetes risk

Exercise and regular physical activity are beneficial for the prevention and management of metabolic diseases such as obesity and type 2 diabetes, whereas exercise cessation, defined as deconditioning from regular exercise or physical activity that has lasted for a period of months to years, can lead to metabolic derangements that drive disease. Adaptations to the insulin-secreting pancreatic β-cells are an important benefit of exercise, whereas less is known about how exercise cessation affects these cells. Our aim is to review the impact that exercise and exercise cessation have on β-cell function, with a focus on the evidence from studies examining glucose-stimulated insulin secretion (GSIS) using gold-standard techniques. Potential mechanisms by which the β-cell adapts to exercise, including exerkine and incretin signaling, autonomic nervous system signaling, and changes in insulin clearance, will also be explored. We will highlight areas for future research.

Therapeutic Physical Exercise Programs in the Context of NASH Cirrhosis and Liver Transplantation: A Systematic Review

In recent years, various physical exercise interventions have been developed with a view to reducing comorbidity and morbidity rates among patients with chronic diseases. Regular physical exercise has been shown to reduce hypertension and mortality in patients with type 2 diabetes. Diabetes and obesity are often associated with the development of nonalcoholic fatty liver disease, which can lead to liver fibrosis and then (in some cases) nonalcoholic steatohepatitis cirrhosis. We searched the literature for publications on personalized physical exercise programs in cirrhotic patients before and after liver transplantation. Eleven studies in cirrhotic patients and one study in liver transplant recipients were included in the systematic review, the results of which were reported in compliance with the preferred reporting items for systematic reviews and meta-analyses guidelines. The personalized physical exercise programs lasted for 6 to 16 weeks. Our review evidenced improvements in peak oxygen consumption and six-minute walk test performance and a reduction in the hepatic venous pressure gradient. In cirrhotic patients, personalized physical exercise programs improve quality of life, are not associated with adverse effects, and (for transplant recipients) might reduce the 90-day hospital readmission rate. However, none of the literature data evidenced reductions in the mortality rates before and after transplantation. Further prospective studies are needed to evaluate the benefit of long-term physical exercise programs in cirrhotic patients before and after liver transplantation.

Exercise in the Prevention and Treatment of Type 2 Diabetes

Type 2 diabetes is a systemic, multifactorial disease that is a leading cause of morbidity and mortality globally. Despite a rise in the number of available medications and treatments available for management, exercise remains a first-line prevention and intervention strategy due to established safety, efficacy, and tolerability in the general population. Herein we review the predisposing risk factors for, prevention, pathophysiology, and treatment of type 2 diabetes. We emphasize key cellular and molecular adaptive processes that provide insight into our evolving understanding of how, when, and what types of exercise may improve glycemic control. © 2023 American Physiological Society. Compr Physiol 13:1-27, 2023.

Labeled breath tests in patients with NASH: Octanoate oxidation relates best to measures of glucose metabolism

In vivo methods to estimate human liver mitochondrial activity are lacking and this project's goal was to use a non-invasive breath test to quantify complete mitochondrial fat oxidation and determine how test results changed when liver disease state was altered over time. Patients with suspected non-alcoholic fatty liver disease (NAFLD; 9 men, 16 women, 47 ± 10 years, 113 ± 23 kg) underwent a diagnostic liver biopsy and liver tissue was histologically scored by a pathologist using the NAFLD activity score (0-8). To assess liver oxidation activity, a labeled medium chain fatty acid was consumed orally (23.4 mg ¹³C₄-octanoate) and breath samples collected over 135 min. Total CO₂ production rates were measured using breath ¹³CO₂ analysis by isotope ratio mass spectrometry. Fasting endogenous glucose production (EGP) was measured using an IV infusion of ¹³C₆-glucose. At baseline, subjects oxidized 23.4 ± 3.9% (14.9%-31.5%) of the octanoate dose and octanoate oxidation (OctOx) was negatively correlated with fasting plasma glucose (r = -0.474, p = 0.017) and EGP (r = -0.441, p = 0.028). Twenty-two subjects returned for repeat tests 10.2 ± 1.0 months later, following lifestyle treatment or standardized care. OctOx (% dose/kg) was significantly greater across all subjects (p = 0.044), negatively related to reductions in EGP (r = -0.401, p = 0.064), and tended to correlate with reduced fasting glucose (r = -0.371, p = 0.090). Subjects exhibited reductions in steatosis (p = 0.007) which tended to correlate with increased OctOx (% of dose/kg, r = -0.411, p = 0.058). Based on our findings, the use of an ¹³C-octanoate breath test may be an indicator of hepatic steatosis and glucose metabolism, but these relationships require verification through larger studies in NAFLD populations.

Gestational diabetes mellitus in the COVID-19 pandemic: A retrospective study from Hangzhou, China

AIMS

Our study aimed to investigate changes in the prevalence of gestational diabetes mellitus (GDM) in the COVID-19 pandemic and postpandemic era and the risk of adverse pregnancy outcomes in pregnant women diagnosed with GDM during the blockade period.

METHODS

First, we investigated changes in the prevalence of GDM and the population undergoing oral glucose tolerance tests (OGTT) after the COVID-19 pandemic. We then collected clinical information from pregnant women diagnosed with GDM to explore the risk of adverse pregnancy outcomes in pregnant women with GDM during the COVID-19 pandemic.

RESULTS

After the COVID-19 pandemic, the proportion of pregnant women in the total number of outpatient OGTT tests decreased yearly. The ratio was 81.30%, 79.71%, and 75.48% from 2019 to 2021, respectively, with the highest proportion of pregnant women in February 2020 (92.03%). The prevalence of GDM was higher in March 2020 compared to the same period in 2019. However, from 2019 to 2021, the prevalence decreased year by year with 21.46%, 19.81%, and 18.48%, respectively. The risk of adverse pregnancy outcomes for pregnant women diagnosed with GDM during the most severe period of the COVID-19 pandemic did not differ from before the COVID-19 pandemic.

CONCLUSIONS

After the COVID-19 pandemic, the prevalence of GDM increased during the most severe period of the epidemic, but the overall prevalence of GDM decreased year by year. In addition, the pandemic did not change the risk of adverse pregnancy outcomes in pregnant women with GDM.

Exercise timing influences multi-tissue metabolome and skeletal muscle proteome profiles in type 2 diabetic patients - A randomized crossover trial

AIMS/HYPOTHESIS

Metabolic effects of exercise may partly depend on the time-of-day when exercise is performed. We tested the hypothesis that exercise timing affects the adaptations in multi-tissue metabolome and skeletal muscle proteome profiles in men with type 2 diabetes.

METHODS

Men fitting the inclusion (type 2 diabetes, age 45-68 years and body mass index 23-33 kg/m²) and exclusion criteria (insulin treatment, smoking, concurrent systemic disease, and regular exercise training) were included in a randomized crossover trial (n = 15). Participants included in this metabolomics and proteomics analysis fully completed all exercise sessions (n = 8). The trial consisted of two weeks of high-intensity interval training (HIT) (three sessions/week) either in the morning (08:00, n = 5) or afternoon (16:45, n = 3), a two-week wash-out period, and an additional two weeks of HIT at the opposing time. Participants and researchers were not blinded to group allocation. Blood, skeletal muscle and subcutaneous adipose tissue were obtained before the first, and after each training period. Broad-spectrum, untargeted proteomic analysis was performed on skeletal muscle, and metabolomic analysis was performed on all biosamples. Differential content was assessed by linear regression and pathway set enrichment analyses were performed. Coordinated metabolic changes across tissues were identified by Spearman correlation analysis.

RESULTS

Metabolic and proteomic profiles remained stable after two weeks of HIT, and individual metabolites and proteins were not altered, irrespective of the time of day at which the training was performed. However, coordinated changes in relevant metabolic pathways and protein categories were identified. Morning and afternoon HIT similarly increased plasma diacylglycerols, skeletal muscle acyl-carnitines, and subcutaneous adipose tissue sphingomyelins and lysophospholipids. Acyl-carnitines were central to training-induced metabolic cross-talk across tissues. Plasma carbohydrates, via the penthose phosphate pathway, were increased and skeletal muscle lipids were decreased after morning compared to afternoon HIT. Skeletal muscle lipoproteins were higher, and mitochondrial complex III abundance was lower after morning compared to afternoon HIT.

CONCLUSIONS/INTERPRETATION

We provide a comprehensive analysis of a multi-tissue metabolomic and skeletal muscle proteomic responses to training at different times of the day in men with type 2 diabetes. Increased circulating lipids and changes in adipose tissue lipid composition were common between morning and afternoon HIT. However, afternoon HIT increased skeletal muscle lipids and mitochondrial content to a greater degree than morning training. Thus, there is a diurnal component in the metabolomic and proteomic response to exercise in men with type 2 diabetes. The clinical relevance of this response warrants further investigation.

The complex relationship between physical activity and diabetes: an overview

Diabetes mellitus (DM) is a widespread condition, representing a challenging disease to manage. Exercise is being increasingly recommended as part of the therapeutic regimen for DM but the management of different forms of physical activity is difficult for individuals with diabetes, trainers, and physicians. Regular exercise can improve health and well-being, helping individuals to achieve their target lipid profile, body composition, cardio-respiratory fitness, and glycemic goals. People with diabetes tend to be as inactive as the general population, with a large percentage of individuals not achieving the minimum amount of recommended physical activity levels. Indeed, several barriers to exercise exist for persons with diabetes, including sports eligibility, multi-modality management of diabetic athletes, and inadequate knowledge about adequate type and intensity of exercise. The aim of the present review is to provide the current understanding of mechanisms, recommendations, and beneficial effects of different modalities of exercise for the treatment of DM.

Post-translational Modifications: The Signals at the Intersection of Exercise, Glucose Uptake, and Insulin Sensitivity

Diabetes is a global epidemic, of which type 2 diabetes makes up the majority of cases. Nonetheless, for some individuals, type 2 diabetes is eminently preventable and treatable via lifestyle interventions. Glucose uptake into skeletal muscle increases during and in recovery from exercise, with exercise effective at controlling glucose homeostasis in individuals with type 2 diabetes. Furthermore, acute and chronic exercise sensitizes skeletal muscle to insulin. A complex network of signals converge and interact to regulate glucose metabolism and insulin sensitivity in response to exercise. Numerous forms of post-translational modifications (eg, phosphorylation, ubiquitination, acetylation, ribosylation, and more) are regulated by exercise. Here we review the current state of the art of the role of post-translational modifications in transducing exercise-induced signals to modulate glucose uptake and insulin sensitivity within skeletal muscle. Furthermore, we consider emerging evidence for noncanonical signaling in the control of glucose homeostasis and the potential for regulation by exercise. While exercise is clearly an effective intervention to reduce glycemia and improve insulin sensitivity, the insulin- and exercise-sensitive signaling networks orchestrating this biology are not fully clarified. Elucidation of the complex proteome-wide interactions between post-translational modifications and the associated functional implications will identify mechanisms by which exercise regulates glucose homeostasis and insulin sensitivity. In doing so, this knowledge should illuminate novel therapeutic targets to enhance insulin sensitivity for the clinical management of type 2 diabetes.

Effects of chronic metformin treatment on training adaptations in men and women with hyperglycemia: A prospective study

OBJECTIVE

This study aimed to determine whether chronic metformin use interferes with the improvements in insulin resistance (IR) and cardiorespiratory fitness with aerobic training in people with hyperglycemia and metabolic syndrome (MetS).

METHODS

A total of 63 middle-aged (53 [7] years) individuals with MetS and obesity (BMI = 32.8 [4.5] kg/m² ) completed 16 weeks of supervised high-intensity interval training (3 d/wk, 43 min/session). Participants were either taking metformin (EXER+MET; n = 29) or were free of any pharmacological treatment for their MetS factors (EXER; n = 34). Groups were similar in their initial cardiorespiratory fitness (maximal oxygen uptake [VO_2MAX ]), age, percentage of women, BMI, and MetS factors (z score). The effects of exercise training on IR (homeostatic model assessment of insulin resistance [HOMA-IR]), MetS z score, VO_2MAX , maximal fat oxidation during exercise, and maximal aerobic power output were measured.

RESULTS

Fasting insulin and HOMA-IR decreased similarly in both groups with training (EXER+MET: -4.3% and -10.6%; EXER: -5.3% and -14.5%; p value for time = 0.005). However, metformin use reduced VO_2MAX improvements by half (i.e., EXER+MET: 12.7%; EXER: 25.3%; p value for time × group = 0.012). Maximal fat oxidation during exercise increased similarly in both groups (EXER+MET: 20.7%; EXER: 25.3%; p value for time = 0.040). VO_2MAX gains were not associated with HOMA-IR reductions (EXER+MET: r = -0.098; p = 0.580; EXER: r = -0.255; p = 0.182).

CONCLUSIONS

Metformin use was associated with attenuated VO_2MAX improvements but did not affect fasting IR reductions with aerobic training in individuals with hyperglycemia and high cardiovascular risk (i.e., MetS).

Aerobic training reduces pancreatic fat content and improves β-cell function: A randomized controlled trial using IDEAL-IQ magnetic resonance imaging

AIMS

To explore the effects of six months of moderate-intensity aerobic exercise on pancreatic fat content and its impact on β-cell function.

MATERIALS AND METHODS

A total of 106 patients with type 2 diabetes mellitus were randomized to either a moderate-intensity aerobic training group (three times a week, including 5 min warm-up, 50 min aerobic dancing, and 5 min relaxation, n = 53) or control group (n = 53) with 6-month intervention. The primary endpoint was change in pancreatic fat content. An intention-to-treat analysis was conducted.

RESULTS

Eighty-six patients completed the study with 43 patients in the aerobic training group. The average age, HbA1c, and pancreatic fat content for all participants (106 patients) were 66.39 ± 5.59 years, 7.05 ± 1.24%, and 10.35 ± 9.20%, respectively. Nearly half (49.06%) of patients were males. Subjects in the aerobic training group saw a significant reduction in pancreatic fat content when compared to controls (p = 0.001). In logistic regression models containing age, diabetes duration, change in BMI, smoking/drinking status, changes in lipid indices, and other abdominal fat content, only reduction in pancreatic fat content (p < 0.05) was an independent protective factor for β-cell function and HbA1c.

CONCLUSIONS

Six months of moderate-intensity aerobic training significantly reduced the pancreatic fat content. The reduction of pancreatic fat content was an independent protective factor for β-cell function and HbA1c.

The associations between health-related physical fitness and fasting blood glucose in war veterans: a population-based study

The main purpose of the study was to analyze the associations between health-related physical fitness and fasting blood glucose in war veterans. In this cross-sectional study, we recruited 764 men and women aged 45-75 years, who were part of the Homeland War between 1990 and 1995 (33.5% women). Health-related physical fitness included: (1) fat mass and fat-free mass (body composition), (2) push-ups in 30 s (muscular dynamic endurance of upper extremities), (3) sit-ups in 30 s (repetitive upper body strength), (4) chair-stands in 30 s (lower body strength), (5) sit-and-reach test (flexibility) and (6) the 2-min step test (cardiorespiratory function). Laboratory measurement of fasting blood glucose was performed according to standardized procedures in resting seated position after a 12-h overnight fast. Generalized estimating equations with multiple regression models were used to calculate the associations between health-related physical fitness and fasting blood glucose. In men, fasting blood glucose was significantly correlated with fat-free mass (β = - 0.25, p < 0.001), push-ups in 30 s (β = - 0.55, p < 0.001), chair-stands in 30 s (β = - 0.50, p < 0.001), sit-ups in 30 s (r = - 0.45, p < 0.001), the sit-and reach test (r = - 0.46, p < 0.001) and the 2-min step test (r = - 0.19, p < 0.001), while fat mass was positively correlated with fasting blood glucose (β = 0.14, p = 0.004). In women, fasting blood glucose was significantly correlated with fat mass (β = 0.20, p = 0.002), fat-free mass (β = - 0.15, p = 0.014), push-ups in 30 s (β = - 0.49, p < 0.001), chair-stands in 30 s (β = - 0.43, p < 0.001), sit-ups in 30 s (β = - 0.52, p < 0.001), the sit-and reach test (β = - 0.40, p < 0.001) and the 2-min step test (β = - 0.35, p < 0.001). This study shows that fasting blood glucose may be predicted by health-related physical fitness test in war veterans.

Exercise as a Moderator of Persistent Neuroendocrine Symptoms of COVID-19

Precipitated by chronic psychological stress, immune system dysregulation, and a hyperinflammatory state, the sequelae of postacute COVID-19 (long COVID) include depression and new-onset diabetes. We hypothesize that exercise counters the neuropsychiatric and endocrine sequelae of long COVID by inducing the release of circulating factors that mediate the anti-inflammatory response, support brain homeostasis, and increase insulin sensitivity.

Effects of a 13-Week Personalized Lifestyle Intervention Based on the Diabetes Subtype for People with Newly Diagnosed Type 2 Diabetes

A type 2 diabetes mellitus (T2DM) subtyping method that determines the T2DM phenotype based on an extended oral glucose tolerance test is proposed. It assigns participants to one of seven subtypes according to their β-cell function and the presence of hepatic and/or muscle insulin resistance. The effectiveness of this subtyping approach and subsequent personalized lifestyle treatment in ameliorating T2DM was assessed in a primary care setting. Sixty participants, newly diagnosed with (pre)diabetes type 2 and not taking diabetes medication, completed the intervention. Retrospectively collected data of 60 people with T2DM from usual care were used as controls. Bodyweight (p < 0.01) and HbA1c (p < 0.01) were significantly reduced after 13 weeks in the intervention group, but not in the usual care group. The intervention group achieved 75.0% diabetes remission after 13 weeks (fasting glucose ≤ 6.9 mmol/L and HbA1c < 6.5% (48 mmol/mol)); for the usual care group, this was 22.0%. Lasting (two years) remission was especially achieved in subgroups with isolated hepatic insulin resistance. Our study shows that a personalized diagnosis and lifestyle intervention for T2DM in a primary care setting may be more effective in improving T2DM-related parameters than usual care, with long-term effects seen especially in subgroups with hepatic insulin resistance.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

Exercise/Physical Activity in Individuals with Type 2 Diabetes: A Consensus Statement from the American College of Sports Medicine

ABSTRACT

This consensus statement is an update of the 2010 American College of Sports Medicine position stand on exercise and type 2 diabetes. Since then, a substantial amount of research on select topics in exercise in individuals of various ages with type 2 diabetes has been published while diabetes prevalence has continued to expand worldwide. This consensus statement provides a brief summary of the current evidence and extends and updates the prior recommendations. The document has been expanded to include physical activity, a broader, more comprehensive definition of human movement than planned exercise, and reducing sedentary time. Various types of physical activity enhance health and glycemic management in people with type 2 diabetes, including flexibility and balance exercise, and the importance of each recommended type or mode are discussed. In general, the 2018 Physical Activity Guidelines for Americans apply to all individuals with type 2 diabetes, with a few exceptions and modifications. People with type 2 diabetes should engage in physical activity regularly and be encouraged to reduce sedentary time and break up sitting time with frequent activity breaks. Any activities undertaken with acute and chronic health complications related to diabetes may require accommodations to ensure safe and effective participation. Other topics addressed are exercise timing to maximize its glucose-lowering effects and barriers to and inequities in physical activity adoption and maintenance.

Alterations in Glycemic Variability, Vascular Health, and Oxidative Stress following a 12-Week Aerobic Exercise Intervention-A Pilot Study

The state of being overweight or obese leads to an increased risk of development of cardiometabolic disease. Increases in glycemic variability have been associated with greater induction of oxidative stress and declined vascular health, which may be exacerbated by higher weight status and improved through exercise. The purpose of this study was to examine the impact of a twelve-week aerobic exercise intervention on continuous glucose monitor (CGM) assessed glucose concentrations and glycemic variability, and biomarkers of vascular health and oxidative stress in overweight or obese adults. Eight adults (Age = 48.9 ± 5.2 years; BMI = 29.4 ± 8.3 kg/m2) completed a twelve-week aerobic exercise intervention. Participants walked three times per week at moderate intensity for ~150 minutes each week. All participants wore a CGM for seven consecutive days at baseline and post-intervention. On the final day of monitoring, a fasting blood sample was collected, and an oral glucose tolerance test (OGTT) was performed. Intra- and inter-day glycemic variability was assessed as the mean amplitude of glycemic excursions, continuous overlapping net glycemic action of one-, two-, and four-hour, and the mean observation of daily differences. Plasma concentrations of nitric oxide (NO) and myeloperoxidase (MPO) were measured, and their ratio was calculated (NO:MPO). No CGM-assessed glucose concentrations or measures of glycemic variability changed from baseline to post-intervention. MPO concentration decreased (24.8 ± 8.2 ng/mL to 16.4 ± 4.6 ng/mL, p < 0.01), the NO:MPO ratio improved (3.5:1 to 6.4:1, p < 0.01) following the twelve-week intervention. Individual level changes in body weight and V̇O₂peak were found. In conclusion, twelve weeks of aerobic exercise reduced oxidative stress and improved the propensity to vasodilate but did not alter CGM-assessed glucose concentrations or glycemic variability in this group of overweight or obese non-diabetic adults. These findings may be due to individual changes in body weight or V̇O2peak, which necessitates further research to explore their influence on these outcomes of interest.

Insulin resistance and insulin sensitizing agents

Insulin resistance is a common feature of obesity and type 2 diabetes, but novel approaches of diabetes subtyping (clustering) revealed variable degrees of insulin resistance in people with diabetes. Specifically, the severe insulin resistant diabetes (SIRD) subtype not only exhibits metabolic abnormalities, but also bears a higher risk for cardiovascular, renal and hepatic comorbidities. In humans, insulin resistance comprises dysfunctional adipose tissue, lipotoxic insulin signaling followed by glucotoxicity, oxidative stress and low-grade inflammation. Recent studies show that aside from metabolites (free fatty acids, amino acids) and signaling proteins (myokines, adipokines, hepatokines) also exosomes with their cargo (proteins, mRNA and microRNA) contribute to altered crosstalk between skeletal muscle, liver and adipose tissue during the development of insulin resistance. Reduction of fat mass mainly, but not exclusively, explains the success of lifestyle modification and bariatric surgery to improve insulin sensitivity. Moreover, some older antihyperglycemic drugs (metformin, thiazolidinediones), but also novel therapeutic concepts (new peroxisome proliferator-activated receptor agonists, incretin mimetics, sodium glucose cotransporter inhibitors, modulators of energy metabolism) can directly or indirectly reduce insulin resistance. This review summarizes molecular mechanisms underlying insulin resistance including the roles of exosomes and microRNAs, as well as strategies for the management of insulin resistance in humans.

Interactions between insulin and exercise

The interaction between insulin and exercise is an example of balancing and modifying the effects of two opposing metabolic regulatory forces under varying conditions. While insulin is secreted after food intake and is the primary hormone increasing glucose storage as glycogen and fatty acid storage as triglycerides, exercise is a condition where fuel stores need to be mobilized and oxidized. Thus, during physical activity the fuel storage effects of insulin need to be suppressed. This is done primarily by inhibiting insulin secretion during exercise as well as activating local and systemic fuel mobilizing processes. In contrast, following exercise there is a need for refilling the fuel depots mobilized during exercise, particularly the glycogen stores in muscle. This process is facilitated by an increase in insulin sensitivity of the muscles previously engaged in physical activity which directs glucose to glycogen resynthesis. In physically trained individuals, insulin sensitivity is also higher than in untrained individuals due to adaptations in the vasculature, skeletal muscle and adipose tissue. In this paper, we review the interactions between insulin and exercise during and after exercise, as well as the effects of regular exercise training on insulin action.

The aetiology and molecular landscape of insulin resistance

Insulin resistance, defined as a defect in insulin-mediated control of glucose metabolism in tissues - prominently in muscle, fat and liver - is one of the earliest manifestations of a constellation of human diseases that includes type 2 diabetes and cardiovascular disease. These diseases are typically associated with intertwined metabolic abnormalities, including obesity, hyperinsulinaemia, hyperglycaemia and hyperlipidaemia. Insulin resistance is caused by a combination of genetic and environmental factors. Recent genetic and biochemical studies suggest a key role for adipose tissue in the development of insulin resistance, potentially by releasing lipids and other circulating factors that promote insulin resistance in other organs. These extracellular factors perturb the intracellular concentration of a range of intermediates, including ceramide and other lipids, leading to defects in responsiveness of cells to insulin. Such intermediates may cause insulin resistance by inhibiting one or more of the proximal components in the signalling cascade downstream of insulin (insulin receptor, insulin receptor substrate (IRS) proteins or AKT). However, there is now evidence to support the view that insulin resistance is a heterogeneous disorder that may variably arise in a range of metabolic tissues and that the mechanism for this effect likely involves a unified insulin resistance pathway that affects a distal step in the insulin action pathway that is more closely linked to the terminal biological response. Identifying these targets is of major importance, as it will reveal potential new targets for treatments of diseases associated with insulin resistance.

The effect of insulin on post-exercise hypoglycemia in adults with type 2 diabetes participating in outpatient exercise-based cardiac rehabilitation

PURPOSE

Few studies have reported on self-monitored blood glucose changes following acute exercise, particularly in patients with type 2 diabetes prescribed oral sulfonylureas and insulin medication. This study sought to determine the magnitude of post-exercise blood glucose changes and incidence of hypoglycemia (blood glucose < 4.0 mmol/L) in relation to medication regimen.

METHODS

A retrospective chart review was conducted in adults with type 2 diabetes attending a 6-month rehabilitation program. Demographics, medications, exercise prescription and patient-reported pre/post-BG values were collected at program initiation. It was hypothesized that patients with type 2 diabetes will experience a post-exercise capillary blood glucose reduction (ΔcapBG), and that incidents of hypoglycemia (< 4.0 mmol/L) will be strongly associated with insulin or oral secretagogue class of medication.

RESULTS

A chart review was conducted (n = 52, 46.2% males, mean age: 62.7 ± 8.3 years, A1c: 7.7 ± 1.6%, body mass index, BMI: 34.4 ± 7.8 kg/m²) in patients with type 2 diabetes (9.0 ± 7.7 years since diagnosis). A greater reduction in BG was related to a greater pre-exercise BG (beta [95% CI]: - 0.46 [- 0.54, - 0.37] mmol, p < 0.0001), independent of BMI and exercise duration. Post-exercise hypoglycemia (< 4.0 mmol) was associated with prescribed insulin use (vs. non-users: 14.5% vs. 3.0%, p < 0.05). Among insulin users, pre-mixed insulin had the highest incidence of hypoglycemia (vs. non-users: 50% vs. 3%, p < 0.0001) and insulin (bolus and basal; vs. non-users: 11.1% vs. 3%, p = 0.04).

CONCLUSIONS

These findings may suggest a low post-exercise hypoglycemia occurrence in patients with type 2 diabetes, except when taking insulin. Self-management strategies should be considered, especially for patients on insulin medications.

Iranian National Clinical Practice Guideline for Exercise in Patients with Diabetes

CONTEXT

Growing evidence highlights the importance of physical activity as a critical element for the prevention and control of diabetes. However, there is no clinical practice guideline focusing on the different aspects of exercise in patients with diabetes, especially for the Iranian population.

OBJECTIVE

We aimed to prepare and adopt a clinical practice guideline to provide well-defined, simple, and concise responses to certain questions related to physical activity and exercise in all patients with diabetes, including type 1, 2, and gestational diabetes mellitus (GDM).

EVIDENCE ACQUISITION

A multidisciplinary team of experts in various fields (sports medicine specialists, endocrinologists, and cardiologists) developed the guideline. This group did the task in four stages: (1) identifying and refining the subject area using 17 clinical questions; (2) appraising evidence through a systematic review of the literature; (3) extracting recommendations from evidence and grading them as A, B, C, or D based on the quality, quantity, and consistency of existing evidence; and (4) subjecting the guideline to external review and finally selecting the recommendations with high scores of appropriateness and agreement. The final version was evaluated and approved by the National Deputy for Curative Affairs - Ministry of Health and Medical Education and has also been endorsed by the Iran Endocrine Society (IES) and Iranian Association of Sports and Exercise Medicine (IASEM).

RESULTS

The guideline consists of 52 recommendations addressing 17 important questions concerning different aspects of exercise prescription in Iranian patients with diabetes.

CONCLUSIONS

The guideline provides evidence-based information that may help physicians to prescribe exercise for Iranian patients with diabetes safely and effectively.

Exercise-nutrient interactions for improved postprandial glycemic control and insulin sensitivity

Type 2 diabetes (T2D) is a rapidly growing yet largely preventable chronic disease. Exaggerated increases in blood glucose concentration following meals is a primary contributor to many long-term complications of the disease that decrease quality of life and reduce lifespan. Adverse health consequences also manifest years prior to the development of T2D due to underlying insulin resistance and exaggerated postprandial concentrations of the glucose-lowering hormone insulin. Postprandial hyperglycemic and hyperinsulinemic excursions can be improved by exercise, which contributes to the well-established benefits of physical activity for the prevention and treatment of T2D. The aim of this review is to describe the postprandial dysmetabolism that occurs in individuals at risk for and with T2D, and highlight how acute and chronic exercise can lower postprandial glucose and insulin excursions. In addition to describing the effects of traditional moderate-intensity continuous exercise on glycemic control, we highlight other forms of activity including low-intensity walking, high-intensity interval exercise, and resistance training. In an effort to improve knowledge translation and implementation of exercise for maximal glycemic benefits, we also describe how timing of exercise around meals and post-exercise nutrition can modify acute and chronic effects of exercise on glycemic control and insulin sensitivity. Novelty: Exaggerated postprandial blood glucose and insulin excursions are associated with disease risk. Both a single session and repeated sessions of exercise improve postprandial glycemic control in individuals with and without T2D. The glycemic benefits of exercise can be enhanced by considering the timing and macronutrient composition of meals around exercise.

The many actions of insulin in skeletal muscle, the paramount tissue determining glycemia

As the principal tissue for insulin-stimulated glucose disposal, skeletal muscle is a primary driver of whole-body glycemic control. Skeletal muscle also uniquely responds to muscle contraction or exercise with increased sensitivity to subsequent insulin stimulation. Insulin's dominating control of glucose metabolism is orchestrated by complex and highly regulated signaling cascades that elicit diverse and unique effects on skeletal muscle. We discuss the discoveries that have led to our current understanding of how insulin promotes glucose uptake in muscle. We also touch upon insulin access to muscle, and insulin signaling toward glycogen, lipid, and protein metabolism. We draw from human and rodent studies in vivo, isolated muscle preparations, and muscle cell cultures to home in on the molecular, biophysical, and structural elements mediating these responses. Finally, we offer some perspective on molecular defects that potentially underlie the failure of muscle to take up glucose efficiently during obesity and type 2 diabetes.

Exercise, CaMKII, and type 2 diabetes

Individuals who exercise regularly are protected from type 2 diabetes and other metabolic syndromes, in part by enhanced gene transcription and induction of many signaling pathways crucial in correcting impaired metabolic pathways associated with a sedentary lifestyle. Exercise activates Calmodulin-dependent protein kinase (CaMK)II, resulting in increased mitochondrial oxidative capacity and glucose transport. CaMKII regulates many health beneficial cellular functions in individuals who exercise compared with those who do not exercise. The role of exercise in the regulation of carbohydrate, lipid metabolism, and insulin signaling pathways are explained at the onset. Followed by the role of exercise in the regulation of glucose transporter (GLUT)4 expression and mitochondrial biogenesis are explained. Next, the main functions of Calmodulin-dependent protein kinase and the mechanism to activate it are illustrated, finally, an overview of the role of CaMKII in regulating GLUT4 expression, mitochondrial biogenesis, and histone modification are discussed.

Exercise Training Impacts Skeletal Muscle Clock Machinery in Prediabetes

PURPOSE

Disruption of the skeletal muscle molecular clock leads to metabolic disease, whereas exercise may be restorative, leading to improvements in metabolic health. The purpose of this study was to evaluate the effects of a 12-wk exercise intervention on skeletal muscle molecular clock machinery in adults with obesity and prediabetes, and determine whether these changes were related to exercise-induced improvements in metabolic health.

METHODS

Twenty-six adults (age, 66 ± 4.5 yr; body mass index (BMI), 34 ± 3.4 kg·m; fasting plasma glucose, 105 ± 15 mg·dL) participated in a 12-wk exercise intervention and were fully provided isoenergetic diets. Body composition (dual x-ray absorptiometry), abdominal adiposity (computed tomography scans), peripheral insulin sensitivity (euglycemic-hyperinsulinemic clamp), exercise capacity (maximal oxygen consumption), and skeletal muscle molecular clock machinery (vastus lateralis biopsy) were assessed at baseline and after intervention. Gene and protein expression of skeletal muscle BMAL1, CLOCK, CRY1/2, and PER 1/2 were measured by quantitative real-time polymerase chain reaction and Western blot, respectively.

RESULTS

Body composition (BMI, dual x-ray absorptiometry, computed tomography), peripheral insulin sensitivity (glucose disposal rate), and exercise capacity (maximal oxygen consumption) all improved (P < 0.005) with exercise training. Skeletal muscle BMAL1 gene (fold change, 1.62 ± 1.01; P = 0.027) and PER2 protein expression (fold change, 1.35 ± 0.05; P = 0.02) increased, whereas CLOCK, CRY1/2, and PER1 were unchanged. The fold change in BMAL1 correlated with post-glucose disposal rate (r = 0.43, P = 0.044), BMI (r = -0.44, P = 0.042), and body weight changes (r = -0.44, P = 0.039) expressed as percent delta.

CONCLUSIONS

Exercise training impacts skeletal muscle molecular clock machinery in a clinically relevant cohort of adults with obesity and prediabetes. Skeletal muscle BMAL1 gene expression may improve insulin sensitivity. Future studies are needed to determine the physiological significance of exercise-induced alterations in skeletal muscle clock machinery.

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.

Metformin May Contribute to Inter-individual Variability for Glycemic Responses to Exercise

Metformin and exercise independently improve glycemic control. Metformin traditionally is considered to reduce hepatic glucose production, while exercise training is thought to stimulate skeletal muscle glucose disposal. Collectively, combining treatments would lead to the anticipation for additive glucose regulatory effects. Herein, we discuss recent literature suggesting that metformin may inhibit, enhance or have no effect on exercise mediated benefits toward glucose regulation, with particular emphasis on insulin sensitivity. Importantly, we address issues surrounding the impact of metformin on exercise induced glycemic benefit across multiple insulin sensitive tissues (e.g., skeletal muscle, liver, adipose, vasculature, and the brain) in effort to illuminate potential sources of inter-individual glycemic variation. Therefore, the review identifies gaps in knowledge that require attention in order to optimize medical approaches that improve care of people with elevated blood glucose levels and are at risk of cardiovascular disease.

Train like an athlete: applying exercise interventions to manage type 2 diabetes

Exercise elicits high energy demands, stimulating cardiorespiratory function and substrate mobilisation and oxidation. Repeated bouts of exercise lead to whole-body adaptations, which improve athletic performance. Distinct exercise modalities and intensities and nutritional conditions pose specific physiological challenges, subsequently inducing different adaptations to training. Athletes often modify these variables to achieve individualised training goals and maximise performance. Exercise training improves glycaemic control in individuals with type 2 diabetes; however, the precise training regimen that confers the most beneficial metabolic adaptations in this population is unknown. In this review, we discuss how modifying exercise type, intensity and modality and nutritional status affects the beneficial effects of exercise on glycaemic control in individuals with type 2 diabetes. Evidence indicates that greater improvements in glycaemic control can be achieved through combined aerobic and resistance training regimens compared with either training type alone. However, the increased frequency of training and a greater number of exercise bouts during combined programmes could be responsible for apparent advantages over a single training modality. The beneficial effects of aerobic exercise on glycaemic control seem to rise with training intensity, with superior adaptations achieved by high-intensity interval training (HIT). In addition, training with low carbohydrate availability ('training low') improves cardiorespiratory function and skeletal muscle oxidative capacity more than conventional training in healthy untrained individuals. Examinations of various training regimens are warranted to assess the safety, efficacy, feasibility and beneficial effects in the type 2 diabetes population. Just like competitive athletes, individuals with type 2 diabetes should be encouraged to adopt training regimens that improve fitness and metabolism. Graphical abstract.

Efficacy of 10-20-30 training versus moderate-intensity continuous training on HbA1c, body composition and maximum oxygen uptake in male patients with type 2 diabetes: A randomized controlled trial

AIM

To compare the efficacy of 10-20-30 training versus moderate-intensity continuous training (MICT) on HbA1c, body composition and maximum oxygen uptake (V˙O₂ max) in male patients with type 2 diabetes (T2D).

MATERIALS AND METHODS

Fifty-one male participants with T2D were randomly assigned (1:1) to a 10-20-30 (N = 26) and a MICT (N = 25) training group. Interventions consisted of supervised cycling three times weekly for 10 weeks, lasting 29 minutes (10-20-30) and 50 minutes (MICT) in a local non-clinical setting. The primary outcome was change in HbA1c from baseline to 10-week follow-up.

RESULTS

Of 51 participants enrolled, 44 (mean age 61.0 ± 6.8 [mean ± SD] years, diagnosed 7.5 ± 5.8 years, baseline HbA1c 7.4% ± 1.3%) were included in the analysis. Training compliance was 84% and 86% in 10-20-30 and MICT, respectively. No adverse events occurred during the intervention. HbA1c decreased (P <0.001) by 0.5 (95% CI -0.72 to -0.21) percentage points with training in 10-20-30, with no change in MICT. The change in 10-20-30 was greater (P <0.05) than in MICT. Visceral fat mass decreased (P <0.05) only with 10-20-30 training, whereas total fat mass decreased (P <0.01) and V˙O₂ max increased (P <0.01) with training in both groups.

CONCLUSIONS

Ten weeks of 10-20-30 training was superior to MICT in lowering HbA1c, and only 10-20-30 training decreased visceral fat mass in patients with T2D. Furthermore, 10-20-30 training was as effective as MICT in reducing total fat mass and increasing V˙O₂ max, despite a 42% lower training time commitment.

Mitochondrial Dysfunction, Insulin Resistance, and Potential Genetic Implications

Insulin resistance (IR) is fundamental to the development of type 2 diabetes (T2D) and is present in most prediabetic (preDM) individuals. Insulin resistance has both heritable and environmental determinants centered on energy storage and metabolism. Recent insights from human genetic studies, coupled with comprehensive in vivo and ex vivo metabolic studies in humans and rodents, have highlighted the critical role of reduced mitochondrial function as a predisposing condition for ectopic lipid deposition and IR. These studies support the hypothesis that reduced mitochondrial function, particularly in insulin-responsive tissues such as skeletal muscle, white adipose tissue, and the liver, is inextricably linked to tissue and whole body IR through the effects on cellular energy balance. Here we discuss these findings as well as address potential mechanisms that serve as the nexus between mitochondrial malfunction and IR.

Efficacy and Safety of an mHealth App and Wearable Device in Physical Performance for Patients With Hepatocellular Carcinoma: Development and Usability Study

Background

Exercise is predicted to have a positive effect among hepatocellular carcinoma (HCC) patients. However, these patients are hesitant to start and build up an exercise program for one major reason: the vague fear of developing hepatic decompensation, a potentially fatal condition that can lead to death. Integrating mobile health (mHealth) with individualized exercise programs could be a possible option for promoting physical capacity among HCC patients.

Objective

The aim of this study was to evaluate the efficacy and safety of rehabilitation exercises, which have been individually prescribed via an mHealth app, on physical fitness, body composition, biochemical profile, and quality of life among HCC patients.

Methods

A total of 37 HCC patients were enrolled in a 12-week course with an mHealth app program targeted to HCC patients. The wearable wristband device Neofit (Partron Co) was provided to participants, and recorded daily physical data, such as the number of steps, calorie expenditure, exercise time, and heart rate. Each participant was given an individualized rehabilitation exercise program that was prescribed and adjusted at the 6-week midintervention period based on the assessment results. At baseline, 6-week, and 12-week sessions, participants’ physical fitness levels (ie, 6-minute walk test, grip strength test, and 30-second chair stand test) were measured. Physical activity levels, as measured by the International Physical Activity Questionnaire-Short Form (IPAQ-SF); body composition (ie, body mass index, body fat percentage, and muscle mass); biochemical profiles; and quality of life, as measured by the European Organization for Research and Treatment of Cancer Quality-of-Life Questionnaire C30, were assessed at baseline and at the end point. At the 6-week midpoint, exercise intensity was individually adjusted.

Results

Of the 37 patients, 31 (84%) completed the 12-week intervention. Grip strength improved significantly after 12 weeks of the intervention. The 30-second chair stand test and the 6-minute walk test showed significant improvement from 0 to 6 weeks, from 0 to 12 weeks, and from 6 to 12 weeks. Muscle mass and the IPAQ-SF score increased significantly after 12 weeks of the intervention without biochemical deterioration.

Conclusions

Following 12 weeks of mHealth care, including an individually prescribed rehabilitation exercise program, we saw significant improvements in physical fitness, body composition, and physical activity without any complication or biochemical deterioration among compensated HCC patients who had completed therapy.

Compliant Titin Isoform Content Is Reduced in Left Ventricles of Sedentary Versus Active Rats

A sedentary lifestyle is associated with increased cardiovascular risk factors and reduced cardiac compliance when compared to a lifestyle that includes exercise training. Exercise training increases cardiac compliance in humans, but the mechanisms underlying this improvement are unknown. A major determinant of cardiac compliance is the compliance of the giant elastic protein titin. Experimentally reducing titin compliance in animal models reduces exercise tolerance, but it is not known whether sedentary versus chronic exercise conditions cause differences in titin isoform content. We hypothesized that sedentary conditions would be associated with a reduction in the content of the longer, more compliant N2BA isoform relative to the stiffer N2B isoform (yielding a reduced N2BA:N2B ratio) compared to age-matched exercising controls. We obtained left ventricles from 16-week old rats housed for 12 weeks in standard (sedentary) or voluntary running wheel (exercised) housing. The N2BA:N2B ratio was decreased in the hearts of sedentary versus active rats (p = 0.041). Gene expression of a titin mRNA splicing factor, RNA Binding Motif 20 protein (RBM20), correlated negatively with N2BA:N2B ratios (p = 0.006, r = -0.449), but was not different between groups, suggesting that RBM20 may be regulated post-transcriptionally. Total phosphorylation of cardiac titin was not different between the active and sedentary groups. This study is the first to demonstrate that sedentary rats exhibit reduced cardiac titin N2BA:N2B isoform ratios, which implies reduced cardiac compliance. These data suggest that a lack of exercise (running wheel) reduces cardiac compliance and that exercise itself increases cardiac compliance.

Exercise-Induced Improvements in Postprandial Glucose Response Are Blunted by Pre-Exercise Hyperglycemia: A Randomized Crossover Trial in Healthy Individuals

BACKGROUND

Exercise improves glycemic control but the magnitude, and in some cases, the direction of this effect is variable. Ambient hyperglycemia has been implicated in this exercise response heterogeneity. The current study investigated whether pre-exercise hyperglycemia directly impacts the effect of exercise on glycemic control.

METHODS

Twelve healthy normal glucose-tolerant males completed four trials in a randomized, crossover design. Each trial consisted of 24-h pre-intervention monitoring, a 7-h intervention, and 24-h post-intervention monitoring. Glycemic control was measured throughout the study by continuous glucose monitoring. The four interventions were no exercise (CON) or 45 min of cycling exercise (70%HRmax) preceded by 3.5 h of either normoglycemia (NG-Ex), steady-state hyperglycemia induced by constant glucose infusion (HG-Ex) or fluctuating glycemia induced by repeated glucose bolus infusions (FG-Ex).

RESULTS

Physical activity and diet were similar between trials, and energy expenditure during exercise was matched between exercise trials (all P > 0.05). Mean glucose during the 3.5 h ± infusion period was higher in HG-Ex (mean ± SEM; 7.2 ± 0.4 mmol/L) and FG-Ex (7.3 ± 0.3 mmol/L) compared to CON (4.8 ± 0.2 mmol/L) and NG-Ex (5.0 ± 0.2 mmol/L) trials (P < 0.01). Glycemic variability was greatest in FG-Ex (P < 0.01). Following the interventions, the postprandial glucose response (iAUC) was reduced by exercise in NG-Ex compared to CON (321.1 ± 38.6 vs. 445.5 ± 49.7 mmol/L.8h, P < 0.05, d=0.81). This benefit was blunted when exercise was preceded by steady-state (HG-Ex, 425.3 ± 45.7 mmol/L.8h) and fluctuating (FG-Ex, 465.5 ± 39.3 mmol/L.8h) hyperglycemia (both P > 0.05 vs. CON).

CONCLUSION

Pre-exercise hyperglycemia blunted the glucoregulatory benefits of acute exercise upon postprandial glucose response, suggesting that exposure to hyperglycemia contributes to exercise response heterogeneity.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT03284216.

The Impact of Physical Activity on Glycemic Variability Assessed by Continuous Glucose Monitoring in Patients With Type 2 Diabetes Mellitus: A Systematic Review

Aim: Patients with Type 2 Diabetes Mellitus (T2DM) have increased risk of developing vascular complications due to chronic hyperglycemia. Glycemic variability (GV) has been suggested to play an even more important role in the risk of developing diabetic complications than sustained hyperglycemia. Physical activity (PA) has shown reducing effects on mean plasma glucose; however, the effect on GV in T2DM needs further description. The objective of this review is to evaluate the effect of PA on GV, assessed by continuous glucose monitoring (CGM) in people with T2DM. Methods: A systematic literature search was conducted on MEDLINE and Embase to find randomized controlled trials (RCTs) covering the aspects T2DM, PA, and CGM. Following eligibility screening, variables of population characteristics, PA interventions, and GV outcomes were extracted and processed through qualitative synthesis. Risk of bias (ROB) was assessed using Cochrane ROB tool v2.0. Results: Of 1,825 identified articles, 40 full texts were screened. In the ten included RCTs matching the eligibility criteria, sample sizes ranged from nine to 63, mean age from 51 (SD 11) to 65 (SD 2) years and mean T2DM duration from four (SD 3) to ten (SD 6) years. Eight RCTs examined GV following single bouts of exercise, while two RCTs examined GV following training interventions. One RCT applied parallel group design, while nine RCTs applied crossover design. Numeric reductions in GV following acute exercise were seen, with four RCTs reaching statistical significance. Numeric reductions in GV were seen following training interventions, with one RCT reaching statistical significance. Numeric reductions of GV after PA appeared independently of intensity and T2DM progression but higher in participants with high baseline HbA1c and GV than with low. 80% of the trials were evaluated as uncertain/high ROB. Conclusion: The systematic literature search revealed limited and biased evidence showing that acute PA numerically reduced GV in patients with T2DM. PA reduced GV independently of PA intensity and T2DM progression. Prolonged RCTs with low ROB are needed to confirm reducing effects of PA on GV and to assess the influence of patient- and intervention characteristics on the effect of PA on GV.

Exercise-Induced Improvements to Whole Body Glucose Metabolism in Type 2 Diabetes: The Essential Role of the Liver

Type 2 diabetes (T2D) is a metabolic disease characterized by obesity, insulin resistance, and the dysfunction of several key glucoregulatory organs. Among these organs, impaired liver function is recognized as one of the earliest contributors to impaired whole-body glucose homeostasis, with well-characterized hepatic insulin resistance resulting in elevated rates of hepatic glucose production (HGP) and fasting hyperglycemia. One portion of this review will provide an overview of how HGP is regulated during the fasted state in healthy humans and how this process becomes dysregulated in patients with T2D. Less well-appreciated is the liver's role in post-prandial glucose metabolism, where it takes up and metabolizes one-third of orally ingested glucose. An abundance of literature has shown that the process of hepatic glucose uptake is impaired in patients with T2D, thereby contributing to glucose intolerance. A second portion of this review will outline how hepatic glucose uptake is regulated during the post-prandial state, and how it becomes dysfunctional in patients with T2D. Finally, it is well-known that exercise training has an insulin-sensitizing effect on the liver, which contributes to improved whole-body glucose metabolism in patients with T2D, thereby making it a cornerstone in the management of the disease. To this end, the impact of exercise on hepatic glucose metabolism will be thoroughly discussed, referencing key findings in the literature. At the same time, sources of heterogeneity that contribute to inconsistent findings in the field will be pointed out, as will important topics for future investigation.

Effects of Exercise Training and IL-6 Receptor Blockade on Gastric Emptying and GLP-1 Secretion in Obese Humans: Secondary Analyses From a Double Blind Randomized Clinical Trial

Background

Interleukin-6 (IL-6) is released from skeletal muscle during exercise and systemic IL-6 levels therefore increase acutely in response to a single bout of exercise. We recently showed that an acute increase in IL-6 delayed gastric emptying rate and improved postprandial glycemia. Here we investigate whether repeated increases in IL-6, induced by exercise training, influence gastric emptying rate and moreover if IL-6 is required for exercise-induced adaptations in glycemic control including secretion of glucagon and glucagon-like peptide-1 (GLP-1).

Methods

A total of 52 abdominally obese non-diabetic men and women were randomly assigned into four groups performing 12 weeks of endurance exercise or no exercise with or without IL-6 receptor blockade (tocilizumab). The primary endpoint was change in gastric emptying rate in response to the intervention and other endpoints included changes in glycemic control, glucagon, and GLP-1 secretion.

Results

There was no change in gastric emptying rate in any of the four groups following the intervention and comparing differences in change between groups also revealed no difference. Postprandial glucose remained unchanged in all groups but the exercise + tocilizumab group, which improved postprandial glucose in response to the intervention. The area under the curve for meal-stimulated glucagon, active and total GLP-1 increased in response to IL-6 receptor blockade, this effect was independent of exercise.

Conclusion

Exercise training and long-term IL-6 receptor blockade did not change gastric emptying rates in obese humans. IL-6 receptor blockade increased glucagon and GLP-1 secretion and implicate IL-6 in the regulation of the human alpha and L cells.

Cardiovascular Risk in Fatty Liver Disease: The Liver-Heart Axis-Literature Review

According to the World Health Organization, cardiovascular disease (CVD) remains the leading cause of death worldwide, accounting for approximately 18 million deaths per year. Nevertheless, the worldwide prevalence of metabolic diseases, such as type 2 diabetes mellitus, obesity, and non-alcoholic fatty liver disease (NAFLD), also known to be common risk factors for CVD, have dramatically increased over the last decades. Chronic alcohol consumption is a major cause of chronic liver diseases (CLD) as well as being a major health care cost expenditure accounting for the spending of tremendous amounts of money annually. NAFLD has become one of the major diseases plaguing the world while standing as the most common cause of liver disease in the Western countries by representing about 75% of all CLD. Currently, the most common cause of death in NAFLD remains to be CVD. Several mechanisms have been suggested to be responsible for associating FLD with CVD through several mechanisms including low-grade systemic inflammation, oxidative stress, adipokines, endoplasmic reticulum stress, lipotoxicity and microbiota dysbiosis which may also be influenced by other factors such as genetic and epigenetic variations. Despite of all this evidence, the exact mechanisms of how FLD can causally contribute to CVD are not fully elucidated and much remains unknown. Moreover, the current literature supports the increasing evidence associating FLD with several cardiovascular (CV) adverse events including coronary artery disease, increased subclinical atherosclerosis risk, structural alterations mainly left ventricular hypertrophy, increased epicardial fat thickness, valvular calcifications including aortic valve sclerosis and mitral annular calcification and functional cardiac modifications mainly diastolic dysfunction in addition to cardiac arrhythmias such as atrial fibrillation and ventricular arrythmias and conduction defects including atrioventricular blocks and bundle branch blocks. Patients with FLD should be evaluated and managed accordingly in order to prevent further complications. Possible management methods include non-pharmacological strategies including life style modifications, pharmacological therapies as well as surgical management. This review aims to summarize the current state of knowledge regarding the pathophysiological mechanisms linking FLD with an increased CV risk, in addition to associated CV adverse events and current management modalities.

The Effects of a Single Versus Three Consecutive Sessions of Football Training on Postprandial Lipemia: a Randomized, Controlled Trial in Healthy, Recreationally Active Males

BACKGROUND

Exercise frequency is important for maintaining health; however, its effects on postprandial responses remain largely unknown. Better understanding this during popular sports activities such as football may influence exercise habits. Therefore, the aim of the present study was to examine the effects of playing one single versus three consecutive days of 60-min small-sided football matches on postprandial lipemia.

METHODS

Fifteen males performed either one (1FOOT; n = 7) or three 60-min football (3FOOT; n = 8) sessions across an 8-day trial period. On day 1, a blood sample was collected at fasted (0 min) and 0.75, 2, 4, 6 h after a high-fat meal. Participants were then randomly allocated to the 1FOOT (day 7) or 3FOOT (days 5, 6, 7) condition. On day 8, they repeated the high-fat meal and blood sampling for 6 h following the meal. Postprandial total and incremental area under the curve (AUC, iAUC, respectively) were calculated.

RESULTS

The postprandial triglyceride iAUC was 41% lower from pre- to post-measures for the 1FOOT (p < 0.05; ES = 1.02) and 15.7% lower for the 3FOOT (ns; ES = 0.41). Total triglyceride AUC was lower (26%) post-football matches in the 3FOOT group only (p < 0.01; ES = 1.23). In 3FOOT, insulin concentration was lower for post- compared to pre-measures at 0.75 and 2 h, respectively (p < 0.001).

CONCLUSION

One single 60-min small-sided football match lowered postprandial TG incremental area under the curve while performing three consecutive days of football matches did not result in a greater attenuation.

TRIAL REGISTRATION

ISRCTN17934193 , registered 06 April 2019.