Resistance training enhances insulin-mediated glucose disposal with minimal effect on the tumor necrosis factor-alpha system in older hypertensives

Resistance training, skeletal muscle hypertrophy, and glucose homeostasis: how related are they? A Systematic review and Meta-analysis

Resistance training (RT) promotes skeletal muscle (Skm) hypertrophy, increases muscular strength, and improves metabolic health. Whether changes in fat-free mass (FFM; a surrogate marker of muscle hypertrophy) moderate RT-induced improvements in glucose homeostasis has not been determined, despite extensive research on the benefits of RT for health and performance. The aim of this meta-analysis is to examine whether RT-induced Skm hypertrophy drives improvements in glucose metabolism and to explore confounders, such as biological sex and training parameters. Random-effects meta-analyses were performed using variance random effects. Meta-regressions were performed for confounding factors depending on the heterogeneity (I2). Analyses from 33 intervention studies revealed significant within-study increases in FFM with a moderate effect size (within-studies: (effect size; ES = 0.24 [0.10; 0.39]; p = 0.002; I2 = 56%) and a tendency for significance when compared with control groups (ES = 0.42 [-0.04-0.88]; p = 0.07). Within-study significant increases in glucose tolerance (2 h glucose: ES = -0.3 [-0.50; -0.11]; p < 0.01; I2 = 43%; glucose area under the curve (AUC): -0.40 [-0.66; -0.13] I2 = 76.1%; p < 0.01) and insulin sensitivity (ES = 0.38 [0.13; 0.62]; I2 = 53.0%; p < 0.01) were also apparent with RT. When compared to control groups, there was no significant difference in 2 h glucose, nor in glucose AUC from baseline in RT intervention groups. Meta-regression analyses failed to consistently reveal increases in FFM as a moderator of glucose homeostasis. Other mixed-effect models were also unsuccessful to unveil biological sex or training parameters as moderators of FFM increases and glucose homeostasis changes. Although Skm hypertrophy and improvements in glycemic control occur concurrently during RT, changes in these variables were not always related. Well-controlled trials including detailed description of training parameters are needed to inform RT guidelines for improving metabolic health. Registration and protocol number (Prospero): CRD42023397362.

Photobiomodulation Enhances the Effect of Strength Training on Insulin Resistance Regardless of Exercise Volume in Mice Fed a High-Fat Diet

The aim was to investigate the effects of different volumes of strength training (ST) in association with photobiomodulation (PBMt) in mice fed a high-fat diet (HFD) on insulin resistance (IR). Male Swiss albino mice were fed HFD and performed high- or low-volume (one-third) ST (3 days/week), associated with PBMt (660 nm + 850 nm; ~42 J delivered) or not (lights off). ST improved IR, lowered visceral adiposity and circulating cytokines, and increased skeletal muscle hypertrophy and mitochondrial activity. The smaller volume of ST did not interfere with the improvement in IR, mitochondrial activity, or inflammatory profile, but exerted a smaller effect on visceral adiposity and skeletal muscle hypertrophy. Association with PBMt further improved IR, regardless of ST volume, although it did not affect adiposity, mitochondrial activity, and the inflammatory profile. Interestingly, PBMt positively affected quadriceps, but attenuated gluteus maximus hypertrophy. The association with PBMt induced greater improvement than ST alone.

A pilot study on biomarkers for tendinopathy: lower levels of serum TNF-α and other cytokines in females but not males with Achilles tendinopathy

Background

Achilles tendinopathy is a painful musculoskeletal condition that is common among athletes, and which limits training capacity and competitive performance. The lack of biomarkers for tendinopathy limits research into risk factors and also the evaluation of new treatments. Cytokines and growth factors involved in regulating the response of tendon cells to mechanical load have potential as biomarkers for tendinopathy.

Methods

This case–control study compared serum concentration of cytokines and growth factors (TNF-α, IL-1β, bFGF, PDFG-BB, IFN-γ, VEGF) between individuals with chronic Achilles tendinopathy and controls. These were measured in fasting serum from 22 individuals with chronic Achilles tendinopathy and 10 healthy controls. Results were analysed in relation to gender and physical activity pattern.

Results

TNF-α concentration was lower in the entire tendinopathy group compared with the entire control group; none of the other cytokines were significantly different. TNF-α levels were nevertheless highly correlated with the other cytokines measured, in most of the subgroups. Analysed by gender, TNF-α and PDGF-BB concentrations were lower in the female tendinopathy group but not the male tendinopathy group. A trend was seen for lower IL-1β in the female tendinopathy group. Physical activity was correlated with TNF-α, PDGF-BB and IL-1β to varying extents for control subgroups, but not for the female tendinopathy group. No correlations were seen with BMI or duration of symptoms.

Conclusions

This pilot study indicates a lower level of TNF-α and PDGF-BB, and to some extent IL-1β among females, but not males, in the chronic phase of Achilles tendinopathy. It is suggested that future studies on tendinopathy biomarkers analyse male and female data separately. The lack of correlation between cytokine level and physical activity in the female tendinopathy group warrants further study.

Metabolic syndrome and insulin resistance: underlying causes and modification by exercise training

Metabolic syndrome (MS) is a collection of cardiometabolic risk factors that includes obesity, insulin resistance, hypertension, and dyslipidemia. Although there has been significant debate regarding the criteria and concept of the syndrome, this clustering of risk factors is unequivocally linked to an increased risk of developing type 2 diabetes and cardiovascular disease. Regardless of the true definition, based on current population estimates, nearly 100 million have MS. It is often characterized by insulin resistance, which some have suggested is a major underpinning link between physical inactivity and MS. The purpose of this review is to: (i) provide an overview of the history, causes and clinical aspects of MS, (ii) review the molecular mechanisms of insulin action and the causes of insulin resistance, and (iii) discuss the epidemiological and intervention data on the effects of exercise on MS and insulin sensitivity.

Resistance training decreases serum inflammatory markers in diabetic rats

Inflammation plays an important role in the genesis and progression of diabetes. The purpose of this study was to investigate the effect of resistance training on serum levels of some inflammatory markers associated with diabetes mellitus. Twenty-four male Wistar rats (290 ± 19 g) were randomly divided into three groups: non-diabetic control (non-DC), diabetic control (DC), and diabetic trained (DT). Animals in DT group were subjected to a resistance training program with the use of a ladder (3 days/week, for 4 weeks). Body weight, serum high sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, tumor necrosis factor (TNF)-α, fasting glucose, and insulin were measured. Four weeks of resistance training decreased serum levels of TNF-α, hs-CRP, and IL-6 in diabetic rats when compared with DC animals. We conclude that resistance training with appropriate intensity, duration, and recovery between exercise bouts has marked anti-inflammatory effects on diabetic rats. This may be an efficient strategy to protect against some diabetic complications.

Nutrition and physical activity programs for obesity treatment (PRONAF study): methodological approach of the project

BACKGROUND

At present, scientific consensus exists on the multifactorial etiopatogenia of obesity. Both professionals and researchers agree that treatment must also have a multifactorial approach, including diet, physical activity, pharmacology and/or surgical treatment. These two last ones should be reserved for those cases of morbid obesities or in case of failure of the previous ones. The aim of the PRONAF study is to determine what type of exercise combined with caloric restriction is the most appropriate to be included in overweigth and obesity intervention programs, and the aim of this paper is to describe the design and the evaluation methods used to carry out the PRONAF study.

METHODS/DESIGN

One-hundred nineteen overweight (46 males) and 120 obese (61 males) subjects aged 18-50 years were randomly assigned to a strength training group, an endurance training group, a combined strength + endurance training group or a diet and physical activity recommendations group. The intervention period was 22 weeks (in all cases 3 times/wk of training for 22 weeks and 2 weeks for pre and post evaluation). All subjects followed a hypocaloric diet (25-30% less energy intake than the daily energy expenditure estimated by accelerometry). 29-34% of the total energy intake came from fat, 14-20% from protein, and 50-55% from carbohydrates. The mayor outcome variables assesed were, biochemical and inflamatory markers, body composition, energy balance, physical fitness, nutritional habits, genetic profile and quality of life. 180 (75.3%) subjects finished the study, with a dropout rate of 24.7%. Dropout reasons included: personal reasons 17 (28.8%), low adherence to exercise 3 (5.1%), low adherence to diet 6 (10.2%), job change 6 (10.2%), and lost interest 27 (45.8%).

DISCUSSION

Feasibility of the study has been proven, with a low dropout rate which corresponds to the estimated sample size. Transfer of knowledge is foreseen as a spin-off, in order that overweight and obese subjects can benefit from the results. The aim is to transfer it to sports centres. Effectiveness on individual health-related parameter in order to determine the most effective training programme will be analysed in forthcoming publications.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01116856.

Strength training as a countermeasure to aging muscle and chronic disease

Strength training (ST) has long been considered a promising intervention for reversing the loss of muscle function and the deterioration of muscle structure associated with advanced age but, until recently, the evidence was insufficient to support its role in the prevention or treatment of disease. In recent decades, there has been a long list of quality reviews examining the effects of ST on functional abilities and a few on risk factors for specific diseases, but none have provided a comprehensive assessment of ST as an intervention for a broad range of diseases. This review provides an overview of research addressing the effectiveness of ST as an intervention for the prevention or treatment of the adverse consequences of (i) aging muscle; (ii) the metabolic syndrome (MetS) and its components, i.e. insulin resistance, abdominal obesity, hyperlipidaemia and hypertension; (iii) fibromyalgia; (iv) rheumatoid arthritis; and (v) Alzheimer's disease. Collectively, these studies indicate that ST may serve as an effective countermeasure to some of the adverse consequences of the MetS, fibromyalgia and rheumatoid arthritis. Evidence in support of the hypothesis that ST reduces insulin resistance or improves insulin action comes both from indirect biomarkers, such as glycosylated haemoglobin (HbA(1c)), and insulin responses to oral glucose tolerance tests, as well as from more direct procedures such as hyperglycaemic and hyperinsulinaemic-euglycaemic clamp techniques. The evidence for the use of ST as a countermeasure of abdominal obesity is less convincing. Although some reports show statistically significant reductions in visceral fat, it is unclear if the magnitude of these changes are physiologically meaningful and if they are independent of dietary influences. The efficacy of ST as an intervention for reducing dyslipidaemia is at best inconsistent, particularly when compared with other pharmacological and non-pharmacological interventions, such as aerobic exercise training. However, there is more consistent evidence for the effectiveness of ST in reducing triglyceride levels. This finding could have clinical significance, given that elevated triglyceride is one of the five criterion measures for the diagnosis of the MetS. Small to moderate reductions in resting and exercise blood pressure have been reported with some indication that this effect may be genotype dependent. ST improves or reverses some of the adverse effects of fibromyalgia and rheumatoid arthritis, particularly pain, inflammation, muscle weakness and fatigue. Investigations are needed to determine how these effects compare with those elicited from aerobic exercise training and/or standard treatments. There is no evidence that ST can reverse any of the major biological or behavioural outcomes of Alzheimer's disease, but there is evidence that the prevalence of this disease is inversely associated with muscle mass and strength. Some indicators of cognitive function may also improve with ST. Thus, ST is an effective countermeasure for some of the adverse effects experienced by patients of many chronic diseases, as discussed in this review.

Inflammation, hepatic enzymes and resistance training in individuals with metabolic risk factors

AIMS

Increases in inflammatory markers, hepatic enzymes and physical inactivity are associated with the development of the metabolic syndrome (MetS). We examined whether inflammatory markers and hepatic enzymes are correlated with traditional risk factors for MetS and studied the effects of resistance training (RT) on these emerging risk factors in individuals with a high number of metabolic risk factors (HiMF, 2.9 +/- 0.8) and those with a low number of metabolic risk factors (LoMF, 0.5 +/- 0.5).

METHODS

Twenty-eight men and 27 women aged 50.8 +/- 6.5 years (mean +/- sd) participated in the study. Participants were randomized to four groups, HiMF training (HiMFT), HiMF control (HiMFC), LoMF training (LoMFT) and LoMF control (LoMFC). Before and after 10 weeks of RT [3 days/week, seven exercises, three sets with intensity gradually increased from 40-50% of one repetition maximum (1RM) to 75-85% of 1RM], blood samples were obtained for the measurement of pro-inflammatory cytokines, C-reactive protein (CRP), gamma-glutamyltransferase (GGT) and alanine aminotransferase (ALT).

RESULTS

At baseline, HiMF had higher interleukin-6 (33.9%), CRP (57.1%), GGT (45.2%) and ALT (40.6%) levels, compared with LoMF (all P < 0.05). CRP, GGT and ALT correlated with the number of risk factors (r = 0.48, 0.51 and 0.57, respectively, all P < 0.01) and with other anthropometric and clinical measures (r range from 0.26 to 0.60, P < 0.05). RT did not significantly alter inflammatory markers or hepatic enzymes (all P > 0.05).

CONCLUSIONS

HiMF was associated with increased inflammatory markers and hepatic enzyme concentrations. RT did not reduce inflammatory markers and hepatic enzymes in individuals with HiMF.

Type 2 diabetes mellitus, resistance training, and innate immunity: is there a common link?

Type 2 diabetes mellitus is a serious chronic disease that is very prevalent in the developed world. The etiology of this disease is not well understood. Recently, the role of the innate immune system in the pathogenesis of type 2 diabetes and its complications has received a great deal of attention. Cytokines, acute phase proteins, and phagocytes have been implicated in this model. Resistance training has known benefits in type 2 diabetic patients and older adults, such as improved insulin action, insulin sensitivity, fasting blood glucose and insulin, and glucose tolerance levels. Actions of pro-inflammatory mediators linked to dysregulated innate immune activity have been associated with type 2 diabetes. The immunomodulatory effects of exercise, and in particular approaches such as resistance training, may provide a strategy to counter these pro-inflammatory effectors. However, the effects of resistance training on innate immunity have not been studied extensively in adults with type 2 diabetes or in older adults who are at increased risk for development of type 2 diabetes. This review discusses the possibility that resistance training may have positive effects on innate immunity in this population and so may provide benefits in addition to improving strength and functional abilities. In particular, the potential of resistance training to modulate pro-inflammatory parameters associated with type 2 diabetes, as a strategy that could provide multiple beneficial health outcomes, is addressed.

Plasma levels of interleukin-6 and C-reactive protein are associated with physical inactivity independent of obesity

It is recognized that the path from physical inactivity and obesity to lifestyle-related diseases involves low-grade inflammation, indicated by elevated plasma levels of inflammatory markers. Interestingly, contracting skeletal muscle is a major source of circulating interleukin-6 (IL-6) in response to acute exercise, but with a markedly lower response in trained subjects. As C-reactive protein (CRP) is induced by IL-6, we hypothesized that basal levels of IL-6 and CRP reflect the degree of regular physical activity when compared with other markers of inflammation associated with lifestyle-related morbidity. Fasting plasma/serum levels of IL-6, IL-18, CRP, tumur necrosis factor-alpha (TNF-alpha), soluble TNF receptor II (sTNF-RII), and adiponectin were measured in healthy non-diabetic men and women (n=84). The amount of leisure-time physical activity (LTPA) was assessed by interview. Obesity was associated with elevated insulin, C-peptide, triglycerides, low-density lipoprotein, IL-6, CRP, and adiponectin (all P<0.05). Importantly, physical inactivity was associated with elevated C-peptide (P=0.036), IL-6 (P=0.014), and CRP (P=0.007) independent of obesity, age, gender, and smoking. Furthermore, the LTPA score was inversely associated with IL-6 (P=0.017) and CRP (P=0.005), but with neither of the other markers. The results indicate that low levels of IL-6 and CRP - not IL-18, TNF-alpha, sTNF-RII, or adiponectin - reflect regular physical activity.

Resistance exercise in individuals with and without cardiovascular disease: 2007 update: a scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism

Prescribed and supervised resistance training (RT) enhances muscular strength and endurance, functional capacity and independence, and quality of life while reducing disability in persons with and without cardiovascular disease. These benefits have made RT an accepted component of programs for health and fitness. The American Heart Association recommendations describing the rationale for participation in and considerations for prescribing RT were published in 2000. This update provides current information regarding the (1) health benefits of RT, (2) impact of RT on the cardiovascular system structure and function, (3) role of RT in modifying cardiovascular disease risk factors, (4) benefits in selected populations, (5) process of medical evaluation for participation in RT, and (6) prescriptive methods. The purpose of this update is to provide clinicians with recommendations to facilitate the use of this valuable modality.

Physical activity in prevention and treatment of the metabolic syndrome

Randomised controlled trials have shown that exercise training has a mild or moderate favourable effect on many metabolic and cardiovascular risk factors that constitute or are related to the metabolic syndrome (MetS). Epidemiological studies suggest that regular physical activity prevents type 2 diabetes, cardiovascular disease, and premature mortality in large part through these risk factors. Although randomized controlled trials with the prevention or treatment of the MetS as the main outcome have not been published, several large randomized controlled trials provide strong evidence that favourable lifestyle changes, including regular physical activity, are effective in the prevention of type 2 diabetes in individuals who are overweight and have impaired glucose tolerance. Compliance with the current recommendations to increase the total volume of moderate-intensity physical activity and to maintain good cardiorespiratory and muscular fitness appears to markedly decrease the likelihood of developing the MetS, especially in high-risk groups. Walking is the most common form of physical activity--it improves health in many ways and is generally safe. Therefore, brisk walking for at least 30 min daily can be recommended as the principal form of physical activity at the population level. If there are no contraindications, more vigorous physical exercise or resistance training should also be considered to obtain additional health benefits. Unstructured and low-intensity physical activity may also decrease the likelihood of developing the MetS, especially when substituted for sedentary behaviours such as watching television. The measurement of maximal oxygen consumption may provide an efficient means to target even individuals with relatively few metabolic risk factors who may benefit from more intensive intervention.

Dynamic strength training improves insulin sensitivity without altering plasma levels and gene expression of adipokines in subcutaneous adipose tissue in obese men

CONTEXT

Obesity is characterized by a low-grade inflammatory state, which could play a role in insulin resistance. Dynamic strength training improves insulin sensitivity.

OBJECTIVE

The objective of this study was to investigate, in obese subjects, whether the insulin sensitizing effect of dynamic strength training is associated with changes in plasma levels and gene expression of adipokines potentially involved in the development of insulin resistance.

DESIGN

Twelve obese male subjects were investigated before and at the end of 3 months of dynamic strength training. Insulin sensitivity was evaluated using euglycemic-hyperinsulinemic clamp. Blood samples and needle biopsy samples of sc abdominal adipose tissue were obtained. The plasma levels and adipose tissue mRNA levels of adiponectin, leptin, IL-1beta, IL-6, and TNF-alpha were determined.

RESULTS

The training induced an increase in the whole-body glucose disposal rate by 24% (P = 0.04). The body weight was not altered during the training. Plasma levels of leptin decreased during the training (16.6 +/- 6.3 vs. 13.1 +/- 5.7 ng/ml) by 21% (P < 0.02), whereas no change in plasma levels of other adipokines and C-reactive protein was observed. Gene expression of the investigated adipokines was not changed in sc adipose tissue during the training.

CONCLUSIONS

In obese subjects, the dynamic strength training resulted in an improvement of whole-body insulin sensitivity. The increase in insulin sensitivity was not associated with training-induced modifications of plasma levels or adipose tissue gene expression of adipokines supposedly involved in the development of insulin resistance.

Regional differences in glucose clearance: effects of insulin and resistance training on arm and leg glucose clearance in older hypertensive individuals

The purpose of this study was to compare insulin's ability to stimulate glucose uptake in the arm and leg in a group of older hypertensive individuals (n = 13, 66 +/- 2 yr old). We also examined the effect of a 4-mo whole body resistance-training (RT) program on arm and leg glucose clearance (GC) during a hyperinsulinemic-euglycemic clamp. During the hyperinsulinemic-euglycemic clamp, GC was assessed by simultaneous measurement of arm and leg blood flow (BF) and assessment of fractional glucose extraction (GE) in blood samples from the brachial artery, brachial vein, and popliteal vein. At baseline, a significant main effect (arm vs. leg) demonstrated greater GC and BF in the arm than in the leg (P = 0.006 for GC and P = 0.012 for BF). Insulin significantly increased GE, BF, and GC in the arm and leg (main effects: P = 0.0001 for GE, P = 0.0001 for BF, and P = 0.0001 for GC) at baseline. However, the effect of insulin was similar in the arm and leg. After RT, a significant main effect (baseline vs. RT) demonstrated greater GE and GC in the leg (P = 0.024 for GE and P = 0.053 for GE), but not in the arm (P = 0.31 for GE and P = 0.14 for GC). No significant main effect (baseline vs. RT) for BF in the arm or leg was observed after RT. In conclusion, the greater GC in the arm than in the leg at baseline is primarily due to enhanced arm BF. Furthermore, whole body RT appears to increase GC in the leg but not in the arm.

Insulin sensitivity derived from oral glucose tolerance testing in athletes: Disagreement between available indices

The aims of the present study were to determine whether available "fasting" and oral glucose tolerance test-derived insulin sensitivity indices could effectively discriminate between individuals with higher than normal insulin sensitivity, and whether they would all provide similar information in clinical practice. Sprint runners (n = 8), endurance runners (n = 8) and sedentary controls (n = 7) received a 75-g oral glucose tolerance test. All participants were healthy lean males, aged 21-29 years. Besides glucose and insulin responses, a total of nine such indices were computed. Fasting as well as post-load glucose concentrations were similar in the three groups, while basal plasma insulin and the insulinaemic response to glucose were both higher in untrained individuals (at P < 0.05 and P < 0.02, respectively). There were no differences between endurance and sprint runners. The results for insulin sensitivity, however, were quite variable: three indices showed that both groups of athletes were more insulin-sensitive than controls; three indicated that this was the case for endurance runners only; one indicated that this was the case for sprint runners only; and two showed that sprint runners were more insulin-sensitive than either sedentary individuals or endurance runners (all differences were significant at P < 0.05). Controlling for total body weight or lean mass did not effectively resolve this disagreement. Apparently, the various insulin sensitivity indices examined provided different quantitative and qualitative information, despite insulin action being greater in both groups of athletes relative to controls, as reflected by their similar glucose tolerance with lower insulin concentrations. We suggest, therefore, that the use and interpretation of such indices among physically active individuals be made with caution.