Exercising for Insulin Sensitivity - Is There a Mechanistic Relationship With Quantitative Changes in Skeletal Muscle Mass?

Comparative efficacy of different exercise types on inflammatory markers in women with overweight and obesity: A systematic review and network meta-analysis of randomized controlled trials

OBJECTIVES

This study aimed to compare and rank the effectiveness of aerobic exercise, resistance training, combined aerobic and resistance exercise, and high-intensity interval training on inflammatory marker levels in women with overweight and obesity by using network meta-analysis.

DESIGN

Systematic review with network meta-analysis and Grading Recommendations Assessment, Development, and Evaluation of the evidence.

METHODS

Literature as of April 2023 was searched from databases such as Cochrane, Embase, Pubmed, Web of Science, and EBSCO, and English-language randomized controlled trials that meet the inclusion criteria were selected. A random-effects network meta-analysis was performed within a frequentist framework.

RESULTS

A total of 75 articles and 4048 participants were included. Resistance training was the most recommended type of exercise to decrease C-reactive protein levels (surface under cumulative ranking = 90.1; standardized mean difference = -0.79, 95 % confidence interval: -1.17, -0.42); aerobic exercise was the most effective exercise type to reduce tumor necrosis factor-α levels (surface under cumulative ranking = 87.9; standardized mean difference = -0.79, 95 % confidence interval: -1.19, -0.39); combined aerobic and resistance exercise was the most effective type of exercise to reduce interleukin-6 levels (surface under cumulative ranking = 75.8; standardized mean difference = -0.77, 95 % confidence interval: -1.38, -0.16) and leptin levels (surface under cumulative ranking = 77.1; standardized mean difference = -0.96, 95 % confidence interval: -1.72, -0.20), and high-intensity interval training was the type of exercise that was well suited to increase adiponectin levels (surface under cumulative ranking = 87.2; standardized mean difference = 0.99, 95 % confidence interval: 0.27, 1.71).

CONCLUSIONS

This network meta-analysis based on randomized controlled trials confirmed that different exercise types have different efficacies on inflammation indicators among women with overweight and obesity. The findings may provide clinicians and healthcare professionals with insights into the implementation of exercise programs for women struggling with overweight and obesity.

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.

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.

Effects of 12-Week Combined Strength and Endurance Circuit Training Program on Insulin Sensitivity and Retinol-Binding Protein 4 in Women with Insulin-Resistance and Overweight or Mild Obesity: A Randomized Controlled Trial

Background

Circuit training is an exercise mode, that may include both endurance and resistance components. There are premises that a combination of these two modalities brings additional benefits, particularly in improving insulin sensitivity. The retinol-binding protein 4 (RBP4) may inhibit signaling from insulin metabolic pathways in skeletal muscles, thus developing insulin resistance. This study aimed to evaluate whether moderate intensity circuit training combining strength and endurance exercise induces changes in tissue insulin sensitivity, carbohydrate and lipid metabolism, and serum RBP4 levels in insulin-resistant women.

Methods

In this clinical controlled trial women diagnosed with insulin-resistance were randomly divided into two groups. The training group (T) performed circuit training combining strength (50%-80%1RM) and endurance (50%-75%HRR) exercise on five weight and two cardio machines, for 33 minutes, three times per week, for 3 months. Women from the control non-training group (NT) did not change their previous physical activity. At the beginning of the study and after the intervention period, a one-repetition maximum, body mass, and composition, resting heart rate (HR), blood pressure, glucose, insulin, blood lipids, thyroid-stimulating hormone (TSH), insulin-like growth factor-1 (IGF-1), RBP4, and insulin resistance (HOMA-IR) were measured. The results of 27 patients were analyzed using a two-way repeated measures ANOVA.

Results

Significant differences in the pattern of change over time between the groups for resting HR (p < 0.010) and total lean mass (p < 0.039) were found. No differences in HOMA-IR, and RBP4 were observed post-study compared to pre-study in the T group. A significant correlation between RBP4 and TSH concentration was found.

Conclusion

Twelve-week circuit training combining strength and endurance exercise has minor effects on HOMA-IR, glucose and lipid metabolism, IGF-1, TSH, and RBP4. Although moderate-intensity circuit training is considered safe, its effectiveness in patients with overweight and mild obesity may be insufficient to reduce insulin resistance.

Trial Registration

ClinicalTrials.gov: NCT04528693, registered August 23, 2020.

DEXA-based Fat Mass with the Risk of Worsening Insulin Resistance in Adolescents: A 9-Year Temporal and Mediation Study

CONTEXT

Surrogate measures of childhood and adolescent obesity have impaired the understanding of body composition's relationship with insulin resistance in the young population.

OBJECTIVES

We aim to examine the longitudinal associations of directly measured total fat mass, trunk fat mass, and lean mass with the risk of hyperglycaemia, hyperinsulinemia, and insulin resistance from ages 15-24 years, the mediation path through which lipids and inflammation influence insulin resistance and whether increased fat mass temporally precede insulin resistance.

METHODS

We studied 3160 adolescents from the Avon Longitudinal Study of Parents and Children (ALSPAC), UK birth cohort, who had complete dual-energy Xray absorptiometry measure and fasting blood samples at age 15 years and repeated measures at ages 17- and 24-years clinic visit. Fasting glucose >6.1 mmol/L, insulin >11.78 mU/L, and homeostatic model assessment for insulin resistance (HOMA-IR) ≥75th percentile were categorized as hyperglycaemia, hyperinsulinemia, and high insulin resistance, respectively. Longitudinal associations were examined with generalized logit-mixed effect models, whilst mediation and temporal path analyses were examined using structural equation models, adjusting for cardiometabolic and other lifestyle factors.

RESULTS

Among 3160 participants (51% female), fat mass and lean mass increased linearly in both males and females while glucose, insulin, and HOMA-IR had a U-shaped course from age 15 through 24 years. After full adjustment, each 1 kg cumulative increase in total fat mass [odds ratio 1.12 (95% confidence interval 1.11-1.13)] and trunk fat mass [1.21 (1.19-1.23)] from ages 15 through 24 years were associated with a progressively worsening risk of high insulin resistance as well as hyperglycaemia and hyperinsulinemia. The association of increased total fat mass with increased insulin resistance was partly mediated by triglycerides (9% mediation). In the temporal path analysis, higher total fat mass at age 15 years was associated with higher insulin resistance at 17 years, but not vice versa. Higher total fat mass at 17 years was bi-directionally associated with higher insulin resistance at 24 years.

CONCLUSION

Mid-adolescence may be an optimal time for interrupting the worsening fat mass-insulin resistance pathologic cycle and attenuating the risk of progressively worsening metabolic dysfunction before young adulthood.

Thyroid Hormone Regulates the Lipid Content of Muscle Fibers, Thus Affecting Physical Exercise Performance

Skeletal muscle (SkM) lipid composition plays an essential role in physiological muscle maintenance and exercise performance. Thyroid hormones (THs) regulate muscle formation and fuel energy utilization by modulating carbohydrates and lipid and protein metabolism. The best-known effects of THs in SkM include the promotion of mitochondrial biogenesis, the fiber-type switch from oxidative to glycolytic fibers, and enhanced angiogenesis. To assess the role of THs on the lipidic composition of SkM fibers, we performed lipidomic analyses of SkM cells and tissues, glucose tolerance experiments, and exercise performance tests. Our data demonstrated that TH treatment induces remodeling of the lipid profile and changes the proportion of fatty acids in SkM. In brief, THs significantly reduced the ratio of stearic/oleic acid in the muscle similar to what is induced by physical activity. The increased proportion of unsaturated fatty acids was linked to an improvement in insulin sensitivity and endurance exercise. These findings point to THs as critical endocrine factors affecting exercise performance and indicate that homeostatic maintenance of TH signals, by improving cell permeability and receptor stability at the cell membrane, is crucial for muscle physiology.

Resistance exercise: a mighty tool that adapts, destroys, rebuilds and modulates the molecular and structural environment of skeletal muscle

PURPOSE

Skeletal muscle regulates health and performance by maintaining or increasing strength and muscle mass. Although the molecular mechanisms in response to resistance exercise (RE) significantly target the activation of protein synthesis, a plethora of other mechanisms and structures must be involved in orchestrating the communication, repair, and restoration of homeostasis after RE stimulation. In practice, RE can be modulated by variations in intensity, continuity and volume, which affect molecular responses and skeletal muscle adaptation. Knowledge of these aspects is important with respect to planning of training programs and assessing the impact of RE training on skeletal muscle.

METHODS

In this narrative review, we introduce general aspects of skeletal muscle substructures that adapt in response to RE. We further highlighted the molecular mechanisms that control human skeletal muscle anabolism, degradation, repair and memory in response to acute and repeated RE and linked these aspects to major training variables.

RESULTS

Although RE is a key stimulus for the activation of skeletal muscle anabolism, it also induces myofibrillar damage. Nevertheless, to increase muscle mass accompanied by a corresponding adaptation of the essential substructures of the sarcomeric environment, RE must be continuously repeated. This requires the permanent engagement of molecular mechanisms that re-establish skeletal muscle integrity after each RE-induced muscle damage.

CONCLUSION

Various molecular regulators coordinately control the adaptation of skeletal muscle after acute and repeated RE and expand their actions far beyond muscle growth. Variations of key resistance training variables likely affect these mechanisms without affecting muscle growth.

The role of exercise in obesity-related cancers: Current evidence and biological mechanisms

Cancer ranks among the five leading causes of death in almost all countries and has important repercussions for individual and public health, the healthcare system, and society in general. Obesity increases the incidence of many types of cancer, but growing evidence suggests that physical activity may decrease risk for developing a variety of obesity-related cancer types, and, in some cases, may improve cancer prognosis and mortality rates. This review summarizes recent evidence on the effect of physical activity on obesity-related cancer prevention and survival. For some cancers, including breast, colorectal, and endometrial cancer, there is strong evidence for a preventative effect of exercise, but for many others, including gallbladder and kidney cancer, and multiple myeloma, evidence is inconsistent or largely lacking. Though many potential mechanisms have been proposed to explain the onco-protective effect of exercise, including improved insulin sensitivity, alterations in sex hormone availability, improved immune function and inflammation, myokine secretion, and modulation of intracellular signaling at the level of AMP kinase, the exact mechanism(s) of action within each cancer subtype remains poorly defined. Overall, a deeper understanding of how exercise can help against cancer and of the exercise parameters that can be altered to optimize exercise prescription is necessary and should be the subject of future investigation.

Pubertal increment in insulin resistance is negatively related to lumbar bone mineral density in 18-year-old males

Transient insulin resistance seen during puberty is expected to favour body growth, but our results show that increment in insulin resistance even in physiological ranges during puberty might compromise lumbar spine bone mineral density accrual independently of body composition parameters, and therefore adult bone quality might be challenged.

INTRODUCTION

Insulin resistance (IR) might have a compromising effect on growing bone, and therefore adult bone quality might be challenged. The aim of the present study was to identify whether increases in IR during puberty contribute to bone mineral characteristics in males independently of body composition parameters.

METHODS

This is a retrospective cohort-based longitudinal observational study. Data from 85 subjects were included. Boys were studied annually during their pubertal years (12 years at baseline) and at follow-up at the age of 18 years. Anthropometry, bone age, fasting blood samples, body composition, total body, and lumbar spine bone mineral characteristics were measured. Insulin resistance was determined by homeostatic model assessment of IR (HOMA-IR). Multiple regression analysis was performed to determine the effect of changes in HOMA-IR during pubertal years as a longitudinal predictor to fixed bone mineral outcome variables at the age of 18 years. All models were adjusted to potential clinically justified confounding variables.

RESULTS

After adjustment to baseline bone indices and body composition-related predictors, the pubertal increment in the HOMA-IR was a negative independent predictor of lumbar spine bone mineral areal density (β =  - 0.202, p = 0.005) and lumbar spine bone mineral apparent density (β =  - 0.235, p = 0.005) in 18-year-old males.

CONCLUSIONS

Pubertal increment in IR has a potential diminishing effect on lumbar spine bone mineral density accrual independently of body composition parameters. Further studies are needed to clarify whether monitoring HOMA-IR during puberty may identify subjects at increased risk of low peak bone mass and possible osteoporosis in the future.

Is insulin resistance tissue-dependent and substrate-specific? The role of white adipose tissue and skeletal muscle

Insulin resistance (IR) refers to a reduction in the ability of insulin to exert its metabolic effects in organs such as adipose tissue (AT) and skeletal muscle (SM), leading to chronic diseases such as type 2 diabetes, hepatic steatosis, and cardiovascular diseases. Obesity is the main cause of IR, however not all subjects with obesity develop clinical insulin resistance, and not all clinically insulin-resistant people have obesity. Recent evidence implies that IR onset is tissue-dependent (AT or SM) and/or substrate-specific (glucometabolic or lipometabolic). Therefore, the aims of the present review are 1) to describe the glucometabolic and lipometabolic activities of insulin in AT and SM in the maintenance of whole-body metabolic homeostasis, 2) to discuss the pathophysiology of substrate-specific IR in AT and SM, and 3) to highlight novel validated tests to assess tissue and substrate-specific IR that are easy to perform in clinical practice. In AT, glucometabolic IR reduces glucose availability for glycerol and fatty acid synthesis, thus decreasing the esterification and synthesis of signaling bioactive lipids. Lipometabolic IR in AT impairs the antilipolytic effect of insulin and lipogenesis, leading to an increase in circulating FFAs and generating lipotoxicity in peripheral tissues. In SM, glucometabolic IR reduces glucose uptake, whereas lipometabolic IR impairs mitochondrial lipid oxidation, increasing oxidative stress and inflammation, all of which lead to metabolic inflexibility. Understanding tissue-dependent and substrate-specific IR is of paramount importance for early detection before clinical manifestations and for the development of more specific treatments or direct interventions to prevent chronic life-threatening diseases.

Comparison between aerobic exercise training and enalapril treatment as tools to improve diet-induced metabolic-associated fatty liver disease: Effects on endoplasmic reticulum stress markers

AIMS

Endoplasmic reticulum (ER) stress poses a new pathological mechanism for metabolic-associated fatty liver disease (MAFLD). MAFLD treatment has encompassed renin-angiotensin system (RAS) blockers and aerobic exercise training, but their association with hepatic ER stress is not well known. Therefore, we aimed to compare the effects of hepatic RAS modulation by enalapril and/or aerobic exercise training over ER stress in MAFLD caused by a diet-induced obesity model.

MAIN METHODS

C57BL/6 mice were fed a standard-chow (CON, n = 10) or a high-fat (HF, n = 40) diet for 8 weeks. HF group was then randomly divided into: HF (n = 10), HF + Enalapril (EN, n = 10), HF + Aerobic exercise training (AET, n = 10), and HF + Enalapril+Aerobic exercise training (EN + AET, n = 10) for 8 more weeks. Body mass (BM) and glucose profile were evaluated. In the liver, ACE and ACE2 activity, morphology, lipid profile, and protein expression of ER stress and metabolic markers were assessed.

KEY FINDINGS

Both enalapril and aerobic exercise training provided comparable efficacy in improving diet-induced MAFLD through modulation of RAS and ER stress, but the latter was more efficient in improving ER stress, liver damage and metabolism.

SIGNIFICANCE

This is the first study to evaluate pharmacological (enalapril) and non-pharmacological (aerobic exercise training) RAS modulators associated with ER stress in a diet-induced MAFLD model.

Effects of combined training during the COVID-19 pandemic on metabolic health and quality of life in sedentary workers: A randomized controlled study

This study aimed to analyze the effects of a combined training (CT) program performed during the first national lockdown due to the COVID-19 pandemic on body composition, metabolic profile, quality of life and stress in sedentary workers, and examines whether changes in the metabolic profile are associated with changes in health-related outcomes which are modifiable by exercise. We evaluated 31 sedentary workers (48.26 ± 7.89 years old). Participants were randomly assigned to a CT group (i.e., performed 16 weeks of exercise) or to a non-exercise control group. The CT program consisted of 16-week of resistance and aerobic exercise. Body composition, glycemic and lipidic profiles, cardiorespiratory fitness (CRF), health-related quality of life and stress levels were assessed pre- and post-intervention. After the intervention period, the CT group demonstrated significantly lower waist and hip circumference (p < 0.05) values than the control group. The control group significantly increased the fasting glucose and HOMA-IR after 16 weeks follow-up (+4.74 mg/dL, p = 0.029; and +0.41 units, p = 0.010, respectively), whiles no significant changes were observed in the CT group in the same parameters (+3.33 mg/dL, p = 0.176; and +0.04 units, p = 0.628, respectively). No changes were observed in the lipid profile for either group (p > 0.05). A significant positive relationship was detected between the change in BMI with the changes in insulin and HOMA-IR (r = 0.643, p = 0.024; and r = 0.605, p = 0.037, respectively). In addition, the changes in CRF were negatively associated with the changes in total cholesterol (r = -0.578, p = 0.049). We observed differences between groups on perceived stress levels and physical, psychological, and environmental domains of quality of life, with the CT group showing better results. Moreover, the CT group improved perceived life satisfaction (+3.17 points, p = 0.038). The findings of the present study suggest that the participants who remained physically active during the first pandemic-related lockdown were able to mitigate the deleterious effects associated with a sedentary lifestyle.

Overweight and Obese Adult Patients Show Larger Benefits from Concurrent Training Compared with Pharmacological Metformin Treatment on Insulin Resistance and Fat Oxidation

Metformin, a drug widely used to treat insulin resistance, and training that combines aerobic and strength exercise modalities (i.e., concurrent training) may improve insulin sensitivity. However, there is a paucity of clinical trials investigating the effects of concurrent training, particularly on insulin resistance and fat oxidation in overweight and obese patients. Furthermore, only a few studies have compared the effects of concurrent training with metformin treatment. Therefore, the aim of this study was to examine the effects of a 12-week concurrent training program versus pharmaceutical treatment with metformin on maximum fat oxidation, glucose metabolism, and insulin resistance in overweight or obese adult patients. Male and female patients with insulin resistance were allocated by convenience to a concurrent training group (n = 7 (2 males); age = 32.9 ± 8.3 years; body mass index = 30 ± 4.0 kg·m^-2) or a metformin group (n = 7 (2 males); age = 34.4 ± 14.0 years; body mass index = 34.4 ± 6.0 kg·m^-2). Before and after the interventions, all participants were assessed for total body mass, body mass index, fat mass, fat-free mass, maximum oxygen consumption, maximal fat oxidization during exercise, fasting glucose, and insulin resistance through the homeostatic model assessment (HOMA-IR). Due to non-normal distribution of the variable maximal fat oxidation, the Mann-Whitney U test was applied and revealed better maximal fat oxidization (Δ = 308%) in the exercise compared with the metformin group (Δ = -30.3%; p = 0.035). All other outcome variables were normally distributed, and significant group-by-time interactions were found for HOMA-IR (p < 0.001, Δ = -84.5%), fasting insulin (p < 0.001, Δ = -84.6%), and increased maximum oxygen consumption (p = 0.046, Δ = 12.3%) in favor of the exercise group. Similar changes were found in both groups for the remaining dependent variables. Concurrent training seems to be more effective compared with pharmaceutical metformin treatment to improve insulin resistance and fat oxidation in overweight and obese adult patients with insulin resistance. The rather small sample size calls for more research in this area.

Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderly Persons with Type 2 Diabetes Mellitus: An Exploratory Randomized Controlled Trial

Although branched-chain amino acids (BCAA) are known to stimulate myofibrillar protein synthesis and affect insulin signaling and kynurenine metabolism (the latter being a metabolite of tryptophan associated with depression and dementia), the effects of BCAA supplementation on type 2 diabetes (T2D) are not clear. Therefore, a 24-week, prospective randomized open blinded-endpoint trial was conducted to evaluate the effects of supplementation of 8 g of BCAA or 7.5 g of soy protein on skeletal muscle and glycemic control as well as adverse events in elderly individuals with T2D. Thirty-six participants were randomly assigned to the BCAA group (n = 21) and the soy protein group (n = 15). Skeletal muscle mass and HbA1c, which were primary endpoints, did not change over time or differ between groups. However, knee extension muscle strength was significantly increased in the soy protein group and showed a tendency to increase in the BCAA group. Homeostasis model assessment for insulin resistance did not significantly change during the trial. Depressive symptoms were significantly improved in the BCAA group but the difference between groups was not significant. Results suggested that BCAA supplementation may not affect skeletal muscle mass and glycemic control and may improve depressive symptoms in elderly individuals with T2D.

Link between Insulin Resistance and Obesity—From Diagnosis to Treatment

Insulin resistance (IR) has become a common health issue in medical practice. There are no detailed data on IR prevalence, but it is an increasing problem due to its close association with obesity. However, IR is not considered as a separate nosological entity and the diagnostic criteria are not well defined, which leads to overdiagnosis of IR and an inappropriate approach. This review aims to summarize the available literature on IR pathophysiology, its relationship with obesity, as well as diagnostic methods, clinical presentation and treatment. Excessive energy intake results in cell overload that triggers mechanisms to protect cells from further energy accumulation by reducing insulin sensitivity. Additionally, hypertrophied adipocytes and macrophage infiltration causes local inflammation that may result in general inflammation that induces IR. The clinical picture varies from skin lesions (e.g., acanthosis nigricans) to metabolic disorders such as diabetes mellitus or metabolic-associated fatty liver disease. There are numerous IR laboratory markers with varying sensitivities and specificities. Nutrition changes and regular physical activity are crucial for IR management because a reduction in adipose tissue may reverse the inflammatory state and consequently reduce the severity of insulin resistance. In cases of obesity, anti-obesity medications can be used.

Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance

As years progress, we are found more often in a postprandial than a postabsorptive state. Chrononutrition is an integral part of metabolism, pancreatic function, and hormone secretion. Eating most calories and carbohydrates at lunch time and early afternoon, avoiding late evening dinner, and keeping consistent number of daily meals and relative times of eating occasions seem to play a pivotal role for postprandial glycemia and insulin sensitivity. Sequence of meals and nutrients also play a significant role, as foods of low density such as vegetables, salads, or soups consumed first, followed by protein and then by starchy foods lead to ameliorated glycemic and insulin responses. There are several dietary schemes available, such as intermittent fasting regimes, which may improve glycemic and insulin responses. Weight loss is important for the treatment of insulin resistance, and it can be achieved by many approaches, such as low-fat, low-carbohydrate, Mediterranean-style diets, etc. Lifestyle interventions with small weight loss (7–10%), 150 min of weekly moderate intensity exercise and behavioral therapy approach can be highly effective in preventing and treating type 2 diabetes. Similarly, decreasing carbohydrates in meals also improves significantly glycemic and insulin responses, but the extent of this reduction should be individualized, patient-centered, and monitored. Alternative foods or ingredients, such as vinegar, yogurt, whey protein, peanuts and tree nuts should also be considered in ameliorating postprandial hyperglycemia and insulin resistance. This review aims to describe the available evidence about the effects of diet, chrononutrition, alternative dietary interventions and exercise on postprandial glycemia and insulin resistance.