Effect of exercise training on serum leptin levels in type 2 diabetic patients

Effect of acute and long-term exercise on leptin levels in depressed outpatients

BACKGROUND

Depression is a leading cause of disability worldwide and a significant contributor to the global burden of disease. Altered leptin levels are known to be associated with depressive symptoms, however discrepancies in the results of increased or decreased levels exist. Due to various limitations associated with commonly used antidepressant drugs, alternatives such as exercise therapy are gaining more importance. Therefore, the current study investigates whether depressed patients have higher leptin levels compared to healthy controls and if exercise is efficient to reduce these levels.

METHODS

Leptin levels of 105 participants with major depressive disorder (MDD; 45.7% female, age mean ± SEM: 39.1 ± 1.0) and 34 healthy controls (HC; 61.8% female, age mean ± SEM: 36.0 ± 2.0) were measured before and after a bicycle ergometer test. Additionally, the MDD group was separated into three groups: two endurance exercise intervention groups (EX) differing in their intensities, and a waiting list control group (WL). Leptin levels were measured pre and post a 12-week exercise intervention or the waiting period.

RESULTS

Baseline data showed no significant differences in leptin levels between the MDD and HC groups. As expected, correlation analyses displayed significant relations between leptin levels and body weight (HC: r = 0.474, p = 0.005; MDD: r = 0.198, p = 0.043) and even more with body fat content (HC: r = 0.755, p < 0.001; MDD: r = 0.675, p < 0.001). The acute effect of the bicycle ergometer test and the 12-week training intervention showed no significant changes in circulating leptin levels.

CONCLUSION

Leptin levels were not altered in patients with major depression compared to healthy controls and exercise, both the acute response and after 12 weeks of endurance training, had no effect on the change in leptin levels.

TRIAL REGISTRATION

The study was registered at the German register for clinical studies (DRKS) and the International Clinical Trials Registry Platform of the World Health Organization https://trialsearch.who.int/Trial2.aspx?TrialID=DRKS00008869 on 28/07/2015.

Physical activity and adipokine levels in individuals with type 2 diabetes: A literature review and practical applications

We review the effects of acute and long-term physical activity on adipokine levels in individuals with type 2 diabetes (T2D). Three electronic databases were searched. Studies made in animal models were excluded, while studies based on participants with and without T2D, and also studies with type 1 diabetes were included. Of the 2,450 citations, 63 trials, including randomised control trials, cross-sectional and longitudinal studies, met our inclusion criteria. Seventy and five percent of studies reported the effects of physical activity on tumor necrosis factor-alpha (TNFα), interleukin 6 (IL-6), adiponectin, visfatin, omentin-1, and leptin levels. There are no robust results due to variations in exercise modality, intensity, duration, and also differences in cohort characteristics in the literature. Only four studies described the effects of an acute session of physical activity on adipokine levels. Overall, physical activity improves diabetes status by regulating adipokine levels. However, long-term aerobic + resistance training combined with dietary modifications is likely to be a more effective strategy for improving adipokines profiles in patients with type 2 diabetes.

Effects of volume-matched resistance training with different loads on glycemic control, inflammation, and body composition in prediabetic older adults

The purpose of the investigation was to examine the influence of resistance training (RT) with equal volume and varying load on glycemic control, inflammation, and body composition in non-obese prediabetic older adults. Non-obese older adults with prediabetes were randomized into two groups - high-load (80% 1RM) and low-load (40% of 1RM) RT (n=12/group), both with the same training volume. Oral glucose tolerance test (OGTT) and blood samples were collected at baseline and again after 10 weeks of RT. Fasting plasma glucose (103.8 vs. 99.9 mg/dL) and the area under the curve (AUC) of OGTT (0-30min) decreased significantly in older adults with prediabetes after 10-weeks of volume-matched RT (p < 0.05). Serum levels of MCP-1 (138.7 vs. 98.5 pg/mL) and TNF-α (1.8 vs. 1.3 pg/mL) showed significant decrease after 10-weeks of high-load RT (p < 0.05). There were no changes in IL-10, IL-6, and CRP levels in both groups. Leptin showed significant decrease after 10-weeks of low-load RT (p < 0.05). Changes in fasting glucose and AUC of OGTT (0-120 min) were positively correlated with changes in MCP-1 and TNF-α (p < 0.05). Lean body mass (39.6 vs. 40.3 kg) increased significantly after 10-weeks of volume-matched RT (p < 0.05). Results indicate that equal-volume RT at different loads is beneficial to glycemic control and muscle growth, and high-load RT shows more prominent anti-inflammatory effects. Novelty: ●Short-term high-load resistance training can help older adults bring their blood sugar level back to normal. ●High-load resistance training attenuates aging-associated chronic inflammation.

The effects of physical activity on adipokines in individuals with overweight/obesity across the lifespan: A narrative review

This narrative review summarizes current knowledge on the effects of physical activity (PA) on adipokine levels in individuals with overweight and obesity. Approximately 90 investigations including randomized control, cross-sectional and longitudinal studies that reported on the effects of a single session of PA (acute) or long-term PA (chronic) on adipokine levels in individuals with overweight/obesity were reviewed. The findings support the notion that there is consensus on the benefits of chronic exercise training-regardless of the mode (resistance vs. aerobic), intensity and cohort (healthy vs. diabetes)-on adipokine levels (such as tumour necrosis factor-alpha, interleukin-6, adiponectin, visfatin, omentin-1 and leptin). However, several confounding factors (frequency, intensity, time and type of exercise) can alter the magnitude of the effects of an acute exercise session. Available evidence suggests that PA, as a part of routine lifestyle behaviour, improves obesity complications by modulating adipokine levels. However, additional research is needed to help identify the most effective interventions to elicit the most beneficial changes in adipokine levels in individuals with overweight/obesity.

Potential exerkines for physical exercise-elicited pro-cognitive effects: Insight from clinical and animal research

A sedentary lifestyle is now known as a critical risk factor for accelerated aging-related neurodegenerative disorders. In contract, having regular physical exercise has opposite effects. Clinical findings have suggested that physical exercise can promote brain plasticity, particularly the hippocampus and the prefrontal cortex, that are important for learning and memory and mood regulations. However, the underlying mechanisms are still unclear. Animal studies reveal that the effects of physical exercise on promoting neuroplasticity could be mediated by different exerkines derived from the peripheral system and the brain itself. This book chapter summarizes the recent evidence from clinical and pre-clinical studies showing the emerging mediators for exercise-promoted brain health, including myokines secreted from skeletal muscles, adipokines from adipose tissues, and other factors secreted from the bone and liver.

Exercise Increases Adiponectin and Reduces Leptin Levels in Prediabetic and Diabetic Individuals: Systematic Review and Meta-Analysis of Randomized Controlled Trials

It is speculated that lifestyle interventions known to improve diabetic metabolic state may exert their effects via adipokines. The aim of this systematic review and meta-analysis was to evaluate the chronic effects of physical exercise on adiponectin and leptin levels in adult prediabetic and diabetic individuals. PubMed, Embase, Scopus, The Cochrane Library, clinicaltrials.gov, and WHO Clinical Trials Registry were searched for randomized controlled trials. Pooled effects of interventions were assessed as mean difference (MD) with random effects model. Sensitivity analysis was conducted to test data robustness and subgroup analysis for study heterogeneity. Twenty-two trials with 2996 individuals were included in the meta-analysis. Physical exercise increased levels of adiponectin (MD: 0.42 µg/mL; 95% confidence interval (CI), 0.23, 0.60, p < 0.00001, n = 19 trials) and reduced leptin levels (MD: −1.89 ng/mL; 95% CI, −2.64, −1.14, p < 0.00001, n = 14 trials). These results were robust and remained significant after sensitivity analysis. Study heterogeneity was generally high. As for physical exercise modalities, aerobic exercise, but not other modalities, increased adiponectin and reduced leptin levels. In conclusion, physical exercise and, specifically, aerobic exercise, leads to higher adiponectin and lower leptin levels in prediabetic and diabetic adults. However, cautious interpretation of current findings is warranted.

Impact to short-term high intensity intermittent training on different storages of body fat, leptin and soluble leptin receptor levels in physically active non-obese men: A pilot investigation

BACKGROUND & AIMS

Studies have postulated High Intensity Intermittent Training (HIIT) as a superior strategy to reduce body fat. The purpose of this study was to compare the effects HIIT and steady-state training (SST) on body composition, leptin, soluble leptin receptor (sOB-R) levels, and hunger perception in physically active non-obese men.

METHODS

Twenty men performed five weeks of HIIT (5 km - 1 min running at 100% speed correspondent to VȩO_2peak - v VȩO_2peak - interspersed with 1-min passive recovery; n = 10) or SST (5 km at 70% of vVȩO_2peak continuously; n = 10) three times a week. Body composition, and hunger perception were assessed at pre- and post-training and were compared by a two-way analysis (group and training period) with repeated measures in the second factor. A fasting time-course (baseline, 24 h, and 48 h after an experimental session of exercise) of leptin and sOB-R levels were measured at pre- and post-five weeks of training and assessed by a three-way analysis (group, period and time of measurement) with repeated measures in the second and third factors.

RESULTS

There was no effect on body composition and hunger perception. Leptin was reduced in both groups, while sOB-R was increased post-five weeks of training in HIIT but not in the SST.

CONCLUSIONS

Although both training groups exerted alterations in leptin levels, only HIIT was able increased sOB-R levels, this suggest a superior impact on central responses in physically active non-obese men.

Endurance exercise training decreased serum levels of surfactant protein D and improved aerobic fitness of obese women with type-2 diabetes

BACKGROUND

Surfactant protein D (SP-D) is a member of the collectin family and is an important component of the pulmonary innate host defense. To find the relationship between exercise training and SP-D in diabetes, we examined the possible effects of a 10-week endurance exercise-training program on serum levels of SP-D, leptin, lipid profile and insulin resistance in obese women with type-2 diabetes mellitus (T2DM).

METHODS

Twenty-two obese women with T2DM were randomly assigned to either exercise training (ET) or control (C) group. A subject dropped from ET group due to personal reasons and 1 subject dropped from C group due to commitment to experiments conditions. A total of twenty obese women with T2DM were randomly assigned into endurance exercise training (ET = 10) and control (C = 10) groups. The training group underwent a progressive endurance-training program for 10 weeks (running on a treadmill for 30-55 min/day at 50-75% heart rate reserve) and the control group did not participate in any exercise program. Venous blood samples were collected from both groups before and 72 h after the last session of exercise training for analysis of serum SP-D, leptin, lipid profile, glucose and insulin. Data were analyzed using 2 (group: control, endurance training) × 2 (time: pre, post) ANOVA with repeated measures on the second factor. Absolute changes from rest (∆ baseline) values were calculated according to the following formula: ((measure-baseline)·baseline-1)·100. Percent change between groups was analyzed using independent t-tests (p < 0.05). All analyses were completed using SPSS 19.

RESULTS

The serum SP-D levels were decreased after exercise training in ET (∆ = - 78.78 ± 17.14%, p = 0.001) when compare to C (∆ = 9.41 ± 4.75%). Obese diabetic women in the ET group showed significantly lower serum leptin levels (8053.27 ± 878.7 pg/ml, ∆ = - 26.97 ± 16.41%) when compared with women in the control group (9885.5 ± 696 pg/ml, ∆ = 7.02 ± 3.46%, p = 0.003). Fasting glucose was favorably and significantly affected by the intervention (ET ∆ = - 17.01 ± 12.74%, Control ∆ = 15.47 ± 7.32%, p = 0.011). VO2max as an index of aerobic fitness was significantly increased after 10-weeks of endurance exercise training (ET ∆ = 19.29 ± 6.18%).

CONCLUSIONS

Endurance exercise training with improvement in aerobic fitness induced a significant reduction of serum SP-D levels in obese women with T2DM.

The impact of duration on effectiveness of exercise, the implication for periodization of training and goal setting for individuals who are overfat, a meta-analysis

Given the assumption that all methods of exercise, e.g., endurance (ET), resistance (RT), or combination of both (E+R), can induce a beneficial effect size (ES) for changes in body composition and health status of individuals who are overfat. Thus the aim and purpose of this study is to evaluate the current body of knowledge to address the question as to the impact that the duration of exercise has on its relative effectiveness for inducing health and body compositional changes in individuals who are overfat to assist with developing periodized exercise protocols and establishing short and long term goals. A tiered meta-analysis of 92-studies and 200-exercise groupings were used for establishing pooled ES within and between groupings based on the increments of 4-week of duration and study designs of ≤8, 9-16, 17-23, 24-36, and ≥36 weeks. Analysis based on random-effect of response indicates a continuum of effectiveness within and between ET, RT and E+R based on duration. Where beneficial effectiveness is not indicated for any measures until after 8-weeks of continuous training with progressive effectiveness being noted in changes to cardiorespiratory fitness, inflammatory cytokines, and alteration of metabolic status from 12-weeks through 32-weeks of continuous training. Results indicate a greater ES for RT and E+R versus ET early in intervention that equalizes with longer durations. Supporting the use of RT and E+R within a periodized program. And secondarily, goals should be established first on performance gains and second body composition or health status modifications for the individual who is overfat.

Evaluation of Trigonella foenum-graecum extract in combination with swimming exercise compared to glibenclamide consumption on type 2 Diabetic rodents

Background/objective

The purpose of the present study was to evaluate the effect of fenugreek seed extract in combination with swimming exercise compared to glibenclamide consumption on type 2 diabetic rats.

Design

The acute toxicity test was carried out to choose the safe doses and identify the toxicity effects of the fenugreek seed extract. To investigate the hypoglycemic effect of the extract and its effect in combination with swimming training, 80 Wistar Kyoto male streptozotocin-induced diabetic rats were divided randomly into eight groups: diabetic control (C); fenugreek seed extract 0.8 g/kg (F1); fenugreek extract 1.6 g/kg (F2); swimming training (S); swimming training plus fenugreek extract 0.8 g/kg (SF1); swimming training plus fenugreek extract 1.6 g/kg (SF2); glibenclamide (G) and swimming training plus glibenclamide (SG). The rats were orally administrated with the treatments once a day with the respective treatment, and the training groups were subjected to swimming training every day for 60 min. Fasting blood samples were collected to measure fasting blood glucose, lipid profile, adiponectin, leptin, and insulin concentrations.

Results

The results obtained from acute toxicity study showed no toxicity effect of fenugreek seed extract on the tested dose. Biochemical analysis showed significant improvements in all of the groups compared to the control group (p<0.05). Plasma insulin concentration and insulin resistance (HOMA-IR) was significantly reduced in treated groups compared with the diabetic control group. Plasma leptin were significantly decreased in treated groups compared with the control group; while adiponectin had markedly increased (p<0.05).

Conclusion

The findings suggest that fenugreek seed consuming, alongside swimming exercise, has a strong therapeutic effect on the improvement of diabetic parameters.

The integrative role of leptin, oestrogen and the insulin family in obesity-associated breast cancer: potential effects of exercise

Obesity is an established risk factor for postmenopausal breast cancer. The mechanisms through which obesity influences the development and progression of breast cancer are not fully elucidated; however, several factors such as increased oestrogen, concentrations of various members of the insulin family and inflammation that are associated with adiposity are purported to be important factors in this relationship. Emerging research has also begun to focus on the role of adipokines, (i.e. adipocyte secreted factors), in breast cancer. Leptin secretion is directly related to adiposity and is believed to promote breast cancer directly and independently, as well as through involvement with the oestrogen and insulin signalling pathways. As leptin is secreted from white adipose tissue, any intervention that reduces adiposity may be favourable. However, it is also important to consider that energy expenditure through exercise, independent of fat loss, may improve leptin regulation. The purpose of this narrative review was to explore the role of leptin in breast cancer development and progression, identify key interactions with oestrogen and the insulin family, and distinguish the potential effects of exercise on these interactions.

Does 8 weeks of strenuous bicycle exercise improve diabetes-related inflammatory cytokines and free fatty acids in type 2 diabetes patients and individuals at high-risk of metabolic syndrome?

In the present study, the effects of 8 weeks of low volume high intensity interval training (HIIT) was investigated on circulating diabetes-related cytokines and free fatty acids (FFA) in adults with type 2 diabetes (T2D) and matched controls (CON).

METHODS

Participants exercised for 8 weeks (3 weekly sessions: 10 × 60 sec HIIT) on a cycle ergometer supervised by medical staff. Prior to the intervention and after the last HIIT session, venous blood samples were collected.

RESULTS

Circulating omentin-1 concentrations increased significantly in both the CON-group (p = 0.003) and in the T2D-group (p = 0.002). Pentraxin-3 (p = 0.010) and IL-1ra (p = 0.031) levels increased significantly in the CON-group. Plasma FFA in the T2D-group was significantly reduced after 60 min (p = 0.011). Post HIIT area under curve of circulating FFAs was reduced by -17.73 ± 6.99% (p = 0.041) in the T2D-group.

CONCLUSION

We observed only modest exercise-induced improvements of multiple diabetes-related cytokines. Circulating levels of FFAs were significantly lowered in the T2D-group.

Immune and Inflammatory Signaling Pathways in Exercise and Obesity

Over the last decades the combination of both a sedentary lifestyle and excessive food availability has led to a significant increase in the prevalence of obesity, which is increasingly recognized as an important risk factor for type 2 diabetes. Several lines of evidence exist demonstrating that expanded visceral adipose tissue produces several pro-inflammatory mediators that activate signaling pathways that contribute to the development of insulin resistance. Exercise training is an important lifestyle factor that is widely used as a tool for preventing and improving lifestyle-related obesity and insulin resistance. In this regard, exercise training is useful to increase energy expenditure thereby counteracting a positive energy balance. Exercise training is also able to attenuate the activation of several obesity-induced pathways of inflammation and oxidative stress. Thus, a better understanding of the molecular mechanisms and immune pathways in exercise, obesity, and diabetes can be extremely useful to exploit optimized lifestyle strategies to combat the increasing incidence of metabolic diseases.

Role of exercise in the management of diabetes mellitus: the global scenario

Background

Exercise training programs have emerged as a useful therapeutic regimen for the management of type 2 diabetes mellitus (T2DM). Majority of the Western studies highlighted the effective role of exercise in T2DM. Therefore, the main aim was to focus on the extent, type of exercise and its clinical significance in T2DM in order to educate the clinicians from developing countries, especially in Asians.

Methods

Pubmed, Science Direct, Scopus, ISI Web of Knowledge and Google scholar were searched using the terms “type 2 diabetes mellitus,” “type 2 DM,” “exercise,” and/or “physical activity,” and “type 2 diabetes mellitus with exercise.” Only clinical or human studies published in English language between 2000 and 2012 were included. Certain criteria were assigned to achieve appropriate results.

Results

Twenty five studies met the selected criteria. The majority of the studies were randomized controlled trial study design (65%). Most of the aerobic exercise based studies showed a beneficial effect in T2DM. Resistance exercise also proved to have positive effect on T2DM patients. Minimal studies related to other types of exercises such as yoga classes, joba riding and endurance-type exercise were found. On the other hand, United States of America (USA) showed strong interest of exercise management towards T2DM.

Conclusion

Aerobic exercise is more common in clinical practice compared to resistance exercise in managing T2DM. Treatment of T2DM with exercise training showed promising role in USA. A large number of researches are mandatory in the developing countries for incorporating exercise in the effective management of T2DM.

The effects of exercise training on obesity-induced dysregulated expression of adipokines in white adipose tissue

Obesity is recognized as a risk factor for lifestyle-related diseases such as type 2 diabetes and cardiovascular disease. White adipose tissue (WAT) is not only a static storage site for energy; it is also a dynamic tissue that is actively involved in metabolic reactions and produces humoral factors, such as leptin and adiponectin, which are collectively referred to as adipokines. Additionally, because there is much evidence that obesity-induced inflammatory changes in WAT, which is caused by dysregulated expression of inflammation-related adipokines involving tumor necrosis factor- α and monocyte chemoattractant protein 1, contribute to the development of insulin resistance, WAT has attracted special attention as an organ that causes diabetes and other lifestyle-related diseases. Exercise training (TR) not only leads to a decrease in WAT mass but also attenuates obesity-induced dysregulated expression of the inflammation-related adipokines in WAT. Therefore, TR is widely used as a tool for preventing and improving lifestyle-related diseases. This review outlines the impact of TR on the expression and secretory response of adipokines in WAT.

Resistance training, visceral obesity and inflammatory response: a review of the evidence

Intra-abdominal obesity is an important risk factor for low-grade inflammation, which is associated with increased risk for diabetes mellitus and cardiovascular disease. For the most part, recommendations to treat or prevent overweight and obesity via physical activity have focused on aerobic endurance training as it is clear that aerobic training is associated with much greater energy expenditure during the exercise session than resistance training. However, due to the metabolic consequences of reduced muscle mass, it is understood that normal ageing and/or decreased physical activity may lead to a higher prevalence of metabolic disorders. Whether resistance training alters visceral fat and the levels of several pro-inflammatory cytokines produced in adipose tissue has not been addressed in earlier reviews. Because evidence suggests that resistance training may promote a negative energy balance and may change body fat distribution, it is possible that an increase in muscle mass after resistance training may be a key mediator leading to a better metabolic control. Considering the benefits of resistance training on visceral fat and inflammatory response, an important question is: how much resistance training is needed to confer such benefits? Therefore, the purpose of this review was to address the importance of resistance training on abdominal obesity, visceral fat and inflammatory response.

Different approaches of physical training used in the management of type 2 diabetes

Background

Type 2 diabetes is now a common and serious global health problem, which, for most countries, has evolved in association with rapid cultural and social changes, ageing populations, increasing urbanisation, dietary changes, reduced physical activity and other unhealthy lifestyle and behavioural patterns.

Aims

To identify the different approaches to physical training used in the last decade in the management of type 2 diabetes.

Methods

We searched PubMed and Science Direct for all randomised clinical trials from 1999 to 30 May 2010.

Results

We selected 17 randomised controlled trials, five studies with aerobic exercise, five with resistance exercise and seven combined exercise studies.

Conclusions

The use of resistance training for the treatment of type 2 diabetes is becoming more commonly used in the management of type 2 diabetes. The number of studies using resistance exercise has been growing over the last decade, and has actually become as widely used as the popular aerobic exercise. In turn, most of the reviewed studies have used interventions combining resistance and aerobic exercise. An exercise programme for diabetic patients should be seen as a form of treatment. Hence, there were no established guidelines for the duration of the programme, because exercise should become a habitual daily task, and assumed in a new lifestyle for long-term glucose control.

High plasma leptin levels confer increased risk of atherosclerosis in women with systemic lupus erythematosus, and are associated with inflammatory oxidised lipids

Background

Patients with systemic lupus erythematosus (SLE) are at increased risk of atherosclerosis, even after accounting for traditional risk factors. High levels of leptin and low levels of adiponectin are associated with both atherosclerosis and immunomodulatory functions in the general population.

Objective

To examine the association between these adipokines and subclinical atherosclerosis in SLE, and also with other known inflammatory biomarkers of atherosclerosis.

Methods

Carotid ultrasonography was performed in 250 women with SLE and 122 controls. Plasma leptin and adiponectin levels were measured. Lipoprotein a (Lp(a)), oxidised phospholipids on apoB100 (OxPL/apoB100), paraoxonase, apoA-1 and inflammatory high-density lipoprotein (HDL) function were also assessed.

Results

Leptin levels were significantly higher in patients with SLE than in controls (23.7±28.0 vs 13.3±12.9 ng/ml, p<0.001). Leptin was also higher in the 43 patients with SLE with plaque than without plaque (36.4±32.3 vs 20.9±26.4 ng/ml, p=0.002). After multivariate analysis, the only significant factors associated with plaque in SLE were leptin levels in the highest quartile (≥29.5 ng/ml) (OR=2.8, p=0.03), proinflammatory HDL (piHDL) (OR=12.8, p<0.001), age (OR=1.1, p<0.001), tobacco use (OR=7.7, p=0.03) and hypertension (OR=3.0, p=0.01). Adiponectin levels were not significantly associated with plaque in our cohort. A significant correlation between leptin and piHDL function (p<0.001), Lp(a) (p=0.01) and OxPL/apoB100 (p=0.02) was also present.

Conclusions

High leptin levels greatly increase the risk of subclinical atherosclerosis in SLE, and are also associated with an increase in inflammatory biomarkers of atherosclerosis such as piHDL, Lp(a) and OxPL/apoB100. High leptin levels may help to identify patients with SLE at risk of atherosclerosis.

Exercise and the Prevention of Oesophageal Cancer (EPOC) study protocol: a randomized controlled trial of exercise versus stretching in males with Barrett's oesophagus

BACKGROUND

Chronic gastro-oesophageal reflux disease and excessive body fat are considered principal causes of Barrett's oesophagus (a metaplastic change in the cells lining the oesophagus) and its neoplastic progression, oesophageal adenocarcinoma. Metabolic disturbances including altered levels of obesity-related cytokines, chronic inflammation and insulin resistance have also been associated with oesophageal cancer development, especially in males. Physical activity may have the potential to abrogate metabolic disturbances in males with Barrett's oesophagus and elicit beneficial reductions in body fat and gastro-oesophageal reflux symptoms. Thus, exercise may be an effective intervention in reducing oesophageal adenocarcinoma risk. However, to date this hypothesis remains untested.The 'Exercise and the Prevention of Oesophageal Cancer Study' will determine whether 24 weeks of exercise training will lead to alterations in risk factors or biomarkers for oesophageal adenocarcinoma in males with Barrett's oesophagus. Our primary outcomes are serum concentrations of leptin, adiponectin, tumour necrosis factor-alpha, C-reactive protein and interleukin-6 as well as insulin resistance. Body composition, gastro-oesophageal reflux disease symptoms, cardiovascular fitness and muscular strength will also be assessed as secondary outcomes.

METHODS/DESIGN

A randomized controlled trial of 80 overweight or obese, inactive males with Barrett's oesophagus will be conducted in Brisbane, Australia. Participants will be randomized to an intervention arm (60 minutes of moderate-intensity aerobic and resistance training, five days per week) or a control arm (45 minutes of stretching, five days per week) for 24 weeks. Primary and secondary endpoints will be measured at baseline (week 0), midpoint (week 12) and at the end of the intervention (week 24).

DISCUSSION

Due to the increasing incidence and very high mortality associated with oesophageal adenocarcinoma, interventions effective in preventing the progression of Barrett's oesophagus are urgently needed. We propose that exercise may be successful in reducing oesophageal adenocarcinoma risk. This primary prevention trial will also provide information on whether the protective association between physical activity and cancer is causal.

TRIAL REGISTRATION

ACTRN12609000401257.

Interaction of single nucleotide polymorphisms in ADRB2, ADRB3, TNF, IL6, IGF1R, LIPC, LEPR, and GHRL with physical activity on the risk of type 2 diabetes mellitus and changes in characteristics of the metabolic syndrome: The Finnish Diabetes Prevention Study

Single nucleotide polymorphisms (SNPs) in the ADRB2, ADRB3, TNF, IL6, IGF1R, LIPC, LEPR, and GHRL genes were associated with the conversion from impaired glucose tolerance (IGT) to type 2 diabetes mellitus (T2D) in the Finnish Diabetes Prevention Study (DPS). In this study, we determined whether polymorphisms in these genes modified the effect of changes in physical activity (PA) on the risk of T2D in the DPS. Moreover, we assessed whether the polymorphisms modified the effect of changes in PA on changes in measures of body fat, serum lipids, and blood pressure during the first year of the follow-up of the DPS. Overweight subjects with IGT (n = 487) were followed for an average of 4.1 years, and PA was assessed annually with a questionnaire. The interactions of the polymorphisms with changes in total and moderate-to-vigorous PA on the conversion to T2D during the 4.1-year follow-up were assessed using Cox regression with adjustments for the other components of the intervention (dietary changes, weight reduction). Univariate analysis of variance was used to assess interactions on changes in continuous variables during the first year of the follow-up. No interaction between the polymorphisms and PA on the conversion to T2D was found. The Leu72Met (rs696217) polymorphism in GHRL modified the effect of moderate-to-vigorous PA on changes in weight and waist circumference, the -501A/C (rs26802) polymorphism in GHRL modified the effect of total and moderate-to-vigorous PA on change in high-density lipoprotein cholesterol, and the Lys109Arg (rs1137100) polymorphism in LEPR modified the effect of total PA on change in blood pressure. In conclusion, genetic variation may modify the magnitude of the beneficial effects of PA on characteristics of the metabolic syndrome in persons with IGT.

The effect of short-term exercise on plasma leptin levels in patients with anorexia nervosa

Plasma leptin concentrations are markedly reduced in malnourished patients with anorexia nervosa (AN). Whether the long-term underweight and low-fat stores affect the leptin response to exercise remains unknown. We investigated the effect of 45-minute cycle ergometer exercise (2 W kg-1 of lean body mass [LBM]) on plasma leptin, norepinephrine (NE), glycerol, and insulin levels in 10 patients with AN and in 15 healthy age-matched women (C). Plasma leptin levels immediately and 90 minutes after the exercise bout were significantly reduced compared with basal leptin levels in both AN and C groups (P<.05). Compared with the control trial, leptin levels were significantly lower immediately and 90 minutes after exercise in the AN group (P<.05) but not in the C group. Basal and exercise-induced plasma glycerol and NE levels did not differ significantly between the groups. Basal and exercise-induced plasma insulin levels were significantly lower in the AN group compared with the C group (P<.05). In conclusion, we demonstrated that a single bout of low-intensity exercise significantly reduces plasma leptin levels in patients with AN. In healthy women, exercise had no effect on lowering leptin concentrations beyond the diurnal decrease that occurs in the absence of exercise. Neither NE nor insulin are responsible for the different response of leptin to exercise in AN.

Effect of Physical Training on Insulin Resistance in Patients With Chronic Heart Failure

BACKGROUND

The effect of physical training on insulin resistance (IR) in chronic heart failure (CHF) remains unclear.

METHODS AND RESULTS

Fourteen patients with CHF performed physical training using a bicycle ergometer; 9 patients (64%) were hyperinsulinemic and insulin resistant (HOMA IR > 1.97). Exercise tolerance increased (5.1 +/- 1.7 to 6.9 +/- 2.7 METs, p < 0.05) and heart rate at rest decreased (82 +/- 15 to 72 +/- 6, p < 0.05) in the IR group after physical training. Physical training also decreased the insulin level (15.1 +/- 5.6 to 9.8 +/- 2.6 microU/ml, p < 0.05) and HOMA IR (3.7 +/- 1.4 to 2.3 +/- 0.6, p < 0.05) in the IR group, but not in the 5 patients (36%) without IR or in 6 control patients.

CONCLUSION

Physical training can improve hyperinsulinemia and IR in patients with CHF.

Fat as an endocrine organ: influence of exercise

The prevalence of diabetes and obesity continues to increase. It is therefore important to identify the pathophysiology underlying these disorders. An inability of insulin to stimulate glucose uptake, i.e., insulin resistance, appears to be a common link between diabetes and obesity. The identification of various adipocyte-secreted cytokines (adipocytokines) that influence satiety, energy balance, and insulin sensitivity provide a novel target for the treatment of these disorders. Adipocytokines are differentially expressed with obesity and diabetes, making them a strong candidate for linking insulin resistance to these pathological conditions. This review explores the role of adipocytokines in insulin action and examines the effect of exercise training on adipocytokine content.

Leptin and altitude in the cardiovascular diseases

OBJECTIVE

The lower mortality from coronary ischemic disease in populations living at high altitude has been related to an increase of high-density lipoprotein (HDL)-cholesterol at altitude. Leptin has been proposed as a cardiovascular risk factor. We investigated whether leptin varies according to the altitude at which people live.

RESEARCH METHODS AND PROCEDURES

This was a cross-sectional study of the first 889 people enrolled in a cohort study in the Canary Islands, Spain. The relationship among serum leptin, altitude, obesity, and other cardiovascular risk factors was analyzed by bivariate and multivariate tests.

RESULTS

Leptin levels showed an inverse correlation to altitude expressed in meters (r = -0.10). Obese subjects had this leptin-altitude association (r = -0.19), but they also had a direct correlation of leptin to HDL-cholesterol (r = 0.27) and an inverse correlation of leptin to the total cholesterol-to-HDL-cholesterol ratio (r = -0.34), triglycerides (r = -0.29), apolipoprotein B (r = -0.21), and glycemia (r = -0.19). Nonobese subjects had only the leptin-altitude association (r = -0.11). The final regression model included altitude as predictor. Other associated variables were gender, physical activity, BMI, age, smoking (reducing leptin independently of BMI), alcohol, heart rate, and income.

DISCUSSION

Serum leptin level decreases when altitude increases, and this association could help to explain the lower cardiovascular mortality rate at high altitude. However, because in obese subjects there is a direct association of leptin with HDL-cholesterol and an inverse association with the lipid atherogenic fractions, we suggest the hypothesis of different roles for bound and free leptin, with free leptin being a cardiovascular protective factor in obese people.

Effects of life-long exercise on circulating free fatty acids and muscle triglyceride content in ageing rats

Regular physical exercise has emerged, together with dietary restriction, as an effective intervention in delaying degenerative diseases and augmenting life span in rodents. The mechanisms involved remain largely unknown, although a beneficial influence on the age-related alteration of insulin sensitivity has been hypothesized. As muscle triglyceride (TG) accumulation is considered a reliable index of muscle insulin resistance, in this study we explored muscle TG content in 23-month-old male Sprague-Dawley rats subjected to life-long training. Plasma glucose, insulin, free fatty acid (FFA) and leptin levels were also measured. Both voluntary running in wheels (RW) and forced training in treadmill (TM) were studied. As RW rats weighed less than controls, a cohort of untrained animals, fed to pair weight (PW) with RW, was added to discriminate the effect of exercise from that of food restriction. Sedentary ad libitum fed rats served as controls. In 23-month-old RW rats, muscle TG content was reduced by 50% with respect to age-matched sedentary controls, while in TM group this reduction was smaller but still highly significant, and occurred independently on the changes in body fat mass. In both the trained rat groups, there was a significant decrease in circulating FFA levels and a trend to reduced insulin levels. In PW rats, muscle TG levels decreased similarly to RW rats, while plasma parameters were less modified. In particular, RW training was more effective than PW in preventing the age-related increase in circulating leptin levels. Our results suggest that voluntary exercise effectively counteracts the development of insulin resistance in the muscles of ageing rats as well as other related changes such as hyperlipacidaemia and compensatory hyperleptinaemia. Forced training or moderate food restriction appear slightly less effective than voluntary exercise in preventing age-dependent alterations in nutrient distribution and/or utilization.

Plasma leptin and exercise: recent findings

It is established that plasma leptin is associated with satiety and that leptin stimulates lipid metabolism, and increases energy expenditure. These effects implicate leptin as a major regulator of energy homeostasis, which may serve to limit excess energy storage. As plasma leptin concentrations are tightly coupled with fat mass in humans, decreases in adipose mass with weight loss coincide with decreased concentrations of circulating leptin. However, due to many confounding factors, the effects of exercise on circulating leptin are less clear. The data from investigations examining single exercise bouts suggest that serum leptin concentrations are unaltered by short duration (41 minutes or less), non-exhaustive exercise, but may be affected by short duration, exhaustive exercise. More convincingly, studies investigating long duration exercise bouts indicate that serum leptin concentrations are reduced with exercise durations ranging from one to multiple hours. These findings raise speculation that exercise-associated reductions in leptin may be due to alterations in nutrient availability or nutrient flux at the level of the adipocytes, the primary site of leptin production and secretion. Thus, one purpose of this review is to discuss the effects of exercise on circulating leptin concentrations with special emphasis on studies that have examined single exercise bouts that are associated with high levels of energy expenditure and energy deficit. In addition, a 'nutrient sensing pathway' (the hexosamine biosynthetic pathway), which regulates leptin gene expression, will be discussed as a possible mechanism by which exercise-induced energy deficit may modulate serum leptin concentrations.

Effects of a 3-week integrated body weight reduction program on leptin levels and body composition in severe obese subjects

The effects of short-term (3 weeks) integrated body weight reduction (BWR) program (including energy-restricted diet, aerobic and strength exercise (5 days/week), nutritional education and psychological counseling) on plasma leptin levels and body composition were investigated in 54 morbidly obese patients (38 females/16 males; mean BMI +/- SE: 41.8 +/- 0.1 kg/m2, range 35-58 kg/m2; mean age: 29.8 +/- 1.0 yr, age range: 18-46 yr). The BWR program induced a significant (p < 0.001) weight loss (BMI reduction: -4.8%) and a significant modification in body composition, consisting in a fat mass (FM) decrease (-7.0 +/- 0.4%, p < 0.001) with a concomitant fat-free (FFM) mass increase (1.8 +/- 0.3%, p < 0.001). On average, plasma leptin levels decreased significantly both in males (from 19.4 +/- 2.6 ng/ml to 11.6 +/- 1.3 ng/ml, p < 0.001) and in females (from 41.1 +/- 3.6 ng/ml to 29.9 +/- 3.0 ng/ml, p < 0.001). Both before and after weight loss, leptin levels were positively correlated (p < 0.001) with BMI and percent fat mass (FM) values. Weight changes after the BWR program were negatively correlated with baseline leptin concentrations both in absolute terms and expressed per unit FM. In conclusion, a short-term diet plus aerobic/strength training effectively induces body composition changes and reduces plasma leptin levels. Body FM reduction appears to be not the unique determinant of leptin levels regulation and the degree of leptin over-expression may negatively affect weight loss in morbidly obese patients.

Leptin and exercise

Short-term exercise (<60 min) studies suggest that leptin concentrations are not acutely affected in healthy males and females. Most reports of reductions in serum leptin may be attributed to circadian rhythms or hemoconcentration. For long-term (> or =60 min) exercise, a reduction in leptin concentrations reported from 1 to 3 hr of running or cycling has been attributed to diurnal reduction in circulating leptin, independent of exercise. Exercise that produces a sufficient energy imbalance (kilocalorie intake versus kilocalorie expenditure) suppresses 24-hr mean and amplitude of the diurnal rhythm of leptin in women. Suppression of leptin concentrations may be counterbalanced by feeding and may explain consistent reports of reductions in leptin concentrations following extreme bouts of exercise such as marathons or ultramarathons. In addition, leptin concentrations are reduced 48 hr after long-term aerobic exercise and long-term resistance exercise is associated with delayed leptin reduction 9 hr postexercise. Training studies have documented that short-term exercise training (< or =12 weeks) does not affect leptin levels, with the exception of patients with type 2 diabetes. Exercise training protocols that result in reduced fat mass will lower leptin concentrations, thus, most investigators have reported leptin concentrations after accounting for fat loss. There are disparate findings concerning long-term (>12 weeks) training studies, with a number of studies finding no effect of training on leptin concentrations other than effects induced by fat loss, and other studies finding reductions in leptin concentrations after accounting for fat loss. Exercise training-induced reductions in leptin levels have been attributed to alterations in energy balance, improvements in insulin sensitivity, alterations in lipid metabolism, and unknown factors. Hormone replacement does not seem to affect leptin adaptations to training. Patients with type 2 diabetes show delayed effects of short-term resistance exercise on leptin concentrations, reduced leptin levels with long-term training, and appear to be more sensitive to training-induced leptin adaptations than other populations.