Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK

AIMS/HYPOTHESIS: This study aimed to determine the extent to which increased insulin resistance and fasting glycaemia in South Asian men, compared with white European men, living in the UK, was due to lower cardiorespiratory fitness (maximal oxygen uptake [[Formula: see text]]) and physical activity. METHODS: One hundred South Asian and 100 age- and BMI-matched European men without diagnosed diabetes, aged 40–70 years, had fasted blood taken for measurement of glucose concentration, HOMA-estimated insulin resistance (HOMA(IR)), plus other risk factors, and underwent assessment of physical activity (using accelerometry), [Formula: see text], body size and composition, and demographic and other lifestyle factors. For 13 South Asian and one European man, HbA(1c) levels were >6.5% (>48 mmol/mol), indicating potential undiagnosed diabetes; these men were excluded from the analyses. Linear regression models were used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in HOMA(IR) and fasting glucose between South Asian and European men. RESULTS: HOMA(IR) and fasting glucose were 67% (p < 0.001) and 3% (p < 0.018) higher, respectively, in South Asians than Europeans. Lower [Formula: see text], lower physical activity and greater total adiposity in South Asians individually explained 68% (95% CI 45%, 91%), 29% (11%, 46%) and 52% (30%, 80%), respectively, and together explained 83% (50%, 119%) (all p < 0.001) of the ethnic difference in HOMA(IR). Lower [Formula: see text] and greater total adiposity, respectively, explained 61% (9%, 111%) and 39% (9%, 76%) (combined effect 63% [8%, 115%]; all p < 0.05) of the ethnic difference in fasting glucose. CONCLUSIONS/INTERPRETATION: Lower cardiorespiratory fitness is a key factor associated with the excess insulin resistance and fasting glycaemia in middle-aged South Asian, compared with European, men living in the UK. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00125-013-2969-y) contains peer-reviewed but unedited supplementary material, which is available to authorised users

Muscle fiber-type distribution predicts weight gain and unfavorable left ventricular geometry: a 19 year follow-up study

BACKGROUND: Skeletal muscle consists of type-I (slow-twitch) and type-II (fast-twitch) fibers, with proportions highly variable between individuals and mostly determined by genetic factors. Cross-sectional studies have associated low percentage of type-I fibers (type-I%) with many cardiovascular risk factors. METHODS: We investigated whether baseline type-I% predicts left ventricular (LV) structure and function at 19-year follow-up, and if so, which are the strongest mediating factors. At baseline in 1984 muscle fiber-type distribution (by actomyosin ATPase staining) was studied in 63 healthy men (aged 32–58 years). The follow-up in 2003 included echocardiography, measurement of obesity related variables, physical activity and blood pressure. RESULTS: In the 40 men not using cardiovascular drugs at follow-up, low type-I% predicted higher heart rate, blood pressure, and LV fractional shortening suggesting increased sympathetic tone. Low type-I% predicted smaller LV chamber diameters (P ≤ 0.009) and greater relative wall thickness (P = 0.034) without increase in LV mass (concentric remodeling). This was explained by the association of type-I% with obesity related variables. Type-I% was an independent predictor of follow-up body fat percentage, waist/hip ratio, weight gain in adulthood, and physical activity (in all P ≤ 0.001). After including these risk factors in the regression models, weight gain was the strongest predictor of LV geometry explaining 64% of the variation in LV end-diastolic diameter, 72% in end-systolic diameter, and 53% in relative wall thickness. CONCLUSION: Low type-I% predicts obesity and weight gain especially in the mid-abdomen, and consequently unfavourable LV geometry indicating increased cardiovascular risk

Rats selectively bred for low aerobic capacity have reduced hepatic mitochondrial oxidative capacity and susceptibility to hepatic steatosis and injury

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65411/1/jphysiol.2009.169060.pd

Blood Viscosity and Hematocrit as Risk Factors for Type 2 Diabetes Mellitus: The Atherosclerosis Risk in Communities (ARIC) Study

Several lines of evidence support the notion that elevated blood viscosity may predispose to insulin resistance and type 2 diabetes mellitus by limiting delivery of glucose, insulin, and oxygen to metabolically active tissues. To test this hypothesis, the authors analyzed longitudinal data on 12,881 initially nondiabetic adults, aged 45–64 years, who were participants in the Atherosclerosis Risk in Communities (ARIC) Study (1987–1998). Whole blood viscosity was estimated by using a validated formula based on hematocrit and total plasma proteins at baseline. At baseline, estimated blood viscosity was independently associated with several features of the metabolic syndrome. In models adjusted simultaneously for known predictors of diabetes, estimated whole blood viscosity and hematocrit predicted incident type 2 diabetes mellitus in a graded fashion (Ptrend (linear) < 0.001): Compared with their counterparts in the lowest quartiles, adults in the highest quartile of blood viscosity (hazard ratio = 1.68, 95% confidence interval: 1.53, 1.84) and hematocrit (hazard ratio = 1.63, 95% confidence interval: 1.49, 1.79) were over 60% more likely to develop diabetes. Therefore, elevated blood viscosity and hematocrit deserve attention as emerging risk factors for insulin resistance and type 2 diabetes mellitus

Continuous low- to moderate-intensity exercise training is as effective as moderate- to high-intensity exercise training at lowering blood HbA1c in obese type 2 diabetes patients

Aims/hypothesis: Exercise represents an effective interventional strategy to improve glycaemic control in type 2 diabetes patients. However, the impact of exercise intensity on the benefits of exercise training remains to be established. In the present study, we compared the clinical benefits of 6 months of continuous low- to moderate-intensity exercise training with those of continuous moderate- to high-intensity exercise training, matched for energy expenditure, in obese type 2 diabetes patients. Methods: Fifty male obese type 2 diabetes patients (age 59∈±∈8 years, BMI 32∈± ∈4 kg/m2) participated in a 6 month continuous endurance-type exercise training programme. All participants performed three supervised exercise sessions per week, either 55 min at 50% of whole body peak oxygen uptake left(VO2peak) (low to moderate intensity) or 40 min at 75% of VO2peak (moderate to high intensity). Oral glucose tolerance, blood glycated haemoglobin, lipid profile, body composition, maximal workload capacity, whole body and skeletal muscle oxidative capacity and skeletal muscle fibre type composition were assessed before and after 2 and 6 months of intervention. Results: The entire 6 month intervention programme was completed by 37 participants. Continuous endurance-type exercise training reduced blood glycated haemoglobin levels, LDL-cholesterol concentrations, body weight and leg fat mass, and increased VO2peak, lean muscle mass and skeletal muscle cytochrome c oxidase and citrate synthase activity (p∈<∈0. 05). No differences were observed between the groups training at low to moderate or moderate to high intensity. Conclusions/interpretation: When matched for energy cost, prolonged continuous low- to moderate-intensity endurance-type exercise training is equally effective as continuous moderate- to high-intensity training in lowering blood glycated haemoglobin and increasing whole body and skeletal muscle oxidative capacity in obese type 2 diabetes patients. © 2009 Springer-Verlag

Effects of High-Intensity Interval Training versus Continuous Training on Physical Fitness, Cardiovascular Function and Quality of Life in Heart Failure Patients

Introduction Physical fitness is an important prognostic factor in heart failure (HF). To improve fitness, different types of exercise have been explored, with recent focus on high-intensity interval training (HIT). We comprehensively compared effects of HIT versus continuous training (CT) in HF patients NYHA II-III on physical fitness, cardiovascular function and structure, and quality of life, and hypothesize that HIT leads to superior improvements compared to CT. Methods Twenty HF patients (male:female 19:1, 64±8 yrs, ejection fraction 38±6%) were allocated to 12-weeks of HIT (10*1-minute at 90% maximal workload—alternated by 2.5 minutes at 30% maximal workload) or CT (30 minutes at 60–75% of maximal workload). Before and after intervention, we examined physical fitness (incremental cycling test), cardiac function and structure (echocardiography), vascular function and structure (ultrasound) and quality of life (SF-36, Minnesota living with HF questionnaire (MLHFQ)). Results Training improved maximal workload, peak oxygen uptake (VO2peak) related to the predicted VO2peak, oxygen uptake at the anaerobic threshold, and maximal oxygen pulse (all P<0.05), whilst no differences were present between HIT and CT (N.S.). We found no major changes in resting cardiovascular function and structure. SF-36 physical function score improved after training (P<0.05), whilst SF-36 total score and MLHFQ did not change after training (N.S.). Conclusion Training induced significant improvements in parameters of physical fitness, although no evidence for superiority of HIT over CT was demonstrated. No major effect of training was found on cardiovascular structure and function or quality of life in HF patients NYHA II-III

The effects of upper and lower limb exercise on the microvascular reactivity in limited cutaneous systemic sclerosis patients

Background: Aerobic exercise in general and high intensity interval training (HIIT) specifically is known to improve vascular function in a range of clinical conditions. HIIT in particular has demonstrated improvements in clinical outcomes, in conditions that have a strong macroangiopathic component. Nevertheless, the effect of HIIT on microcirculation in systemic sclerosis (SSc) patients is yet to be investigated. Therefore, the purpose of the study was to compare the effects of two HIIT protocols (cycle and arm cranking) on the microcirculation of the digital area in SSc patients. Methods: Thirty four limited cutaneous SSc patients (65.3 ± 11.6 years old) were randomly allocated in three groups (cycling, arm cranking and control group). The exercise groups underwent a twelve-week exercise program twice per week. All patients performed the baseline and post-exercise intervention measurements where physical fitness, functional ability, transcutaneous oxygen tension (ΔtcpO2), body composition and quality of life were assessed. Endothelial-dependent as well as-independent vasodilation were assessed in the middle and index fingers using LDF and incremental doses of acetylcholine (ACh) and sodium nitroprusside (SNP). Cutaneous flux data were expressed as cutaneous vascular conductance (CVC). Results: Peak oxygen uptake increased in both exercise groups (p<0.01, d=1.36). ΔtcpO2 demonstrated an increase in the arm cranking group only, with a large effect, but not found statistically significant,(p=0.59, d=0.93). Endothelial-dependent vasodilation improvement was greater in the arm cranking (p<0.05, d=1.07) in comparison to other groups. Both exercise groups improved life satisfaction (p<0.001) as well as reduced discomfort and pain due to Raynaud's phenomenon (p<0.05). Arm cranking seems to be the preferred mode of exercise for study participants as compared to cycling (p<0.05). No changes were observed in the body composition or the functional ability in both exercise groups. Conclusion: Our results suggest that arm cranking has the potential to improve the microvascular endothelial function in SSc patients. Also notably, our recommended training dose (e.g., a 12-week HIIT program, twice per week), appeared to be sufficient and tolerable for this population. Future research should focus on exploring the feasibility of a combined exercise such as aerobic and resistance training by assessing individual's experience and the quality of life in SSc patients. Trial registration: ClinicalTrials.gov (NCT number): NCT03058887, February 23, 2017, https://clinicaltrials.gov/ct2/show/NCT03058887?term=NCT03058887&rank=1 Key words: High intensity interval training, vascular function, quality of lif

Rationale and design of the Exercise Intensity Trial (EXCITE): A randomized trial comparing the effects of moderate versus moderate to high-intensity aerobic training in women with operable breast cancer

<p>Abstract</p> <p>Background</p> <p>The Exercise Intensity Trial (EXcITe) is a randomized trial to compare the efficacy of supervised moderate-intensity aerobic training to moderate to high-intensity aerobic training, relative to attention control, on aerobic capacity, physiologic mechanisms, patient-reported outcomes, and biomarkers in women with operable breast cancer following the completion of definitive adjuvant therapy.</p> <p>Methods/Design</p> <p>Using a single-center, randomized design, 174 postmenopausal women (58 patients/study arm) with histologically confirmed, operable breast cancer presenting to Duke University Medical Center (DUMC) will be enrolled in this trial following completion of primary therapy (including surgery, radiation therapy, and chemotherapy). After baseline assessments, eligible participants will be randomized to one of two supervised aerobic training interventions (moderate-intensity or moderate/high-intensity aerobic training) or an attention-control group (progressive stretching). The aerobic training interventions will include 150 mins.wk^-1of supervised treadmill walking per week at an intensity of 60%-70% (moderate-intensity) or 60% to 100% (moderate to high-intensity) of the individually determined peak oxygen consumption (VO_2peak) between 20-45 minutes/session for 16 weeks. The progressive stretching program will be consistent with the exercise interventions in terms of program length (16 weeks), social interaction (participants will receive one-on-one instruction), and duration (20-45 mins/session). The primary study endpoint is VO_2peak, as measured by an incremental cardiopulmonary exercise test. Secondary endpoints include physiologic determinants that govern VO_2peak, patient-reported outcomes, and biomarkers associated with breast cancer recurrence/mortality. All endpoints will be assessed at baseline and after the intervention (16 weeks).</p> <p>Discussion</p> <p>EXCITE is designed to investigate the intensity of aerobic training required to induce optimal improvements in VO_2peakand other pertinent outcomes in women who have completed definitive adjuvant therapy for operable breast cancer. Overall, this trial will inform and refine exercise guidelines to optimize recovery in breast and other cancer survivors following the completion of primary cytotoxic therapy.</p> <p>Trial Registration</p> <p>NCT01186367</p

Are ‘Endurance’ Alleles ‘Survival’ Alleles? Insights from the ACTN3 R577X Polymorphism

Exercise phenotypes have played a key role for ensuring survival over human evolution. We speculated that some genetic variants that influence exercise phenotypes could be associated with exceptional survival (i.e. reaching ≥100years of age). Owing to its effects on muscle structure/function, a potential candidate is the Arg(R)577Ter(X) polymorphism (rs1815739) in ACTN3, the structural gene encoding the skeletal muscle protein α-actinin-3. We compared the ACTN3 R577X genotype/allele frequencies between the following groups of ethnically-matched (Spanish) individuals: centenarians (cases, n = 64; 57 female; age range: 100–108 years), young healthy controls (n = 283, 67 females, 216 males; 21±2 years), and humans who are at the two end-points of exercise capacity phenotypes, i.e. muscle endurance (50 male professional road cyclists) and muscle power (63 male jumpers/sprinters). Although there were no differences in genotype/allele frequencies between centenarians (RR:28.8%; RX:47.5%; XX:23.7%), and controls (RR:31.8%; RX:49.8%; XX:18.4%) or endurance athletes (RR:28.0%; RX:46%; XX:26.0%), we observed a significantly higher frequency of the X allele (P = 0.019) and XX genotype (P = 0.011) in centenarians compared with power athletes (RR:47.6%; RX:36.5%;XX:15.9%). Notably, the frequency of the null XX (α-actinin-3 deficient) genotype in centenarians was the highest ever reported in non-athletic Caucasian populations. In conclusion, despite there were no significant differences with the younger, control population, overall the ACTN3 genotype of centenarians resembles that of world-class elite endurance athletes and differs from that of elite power athletes. Our preliminary data would suggest a certain ‘survival’ advantage brought about by α-actinin-3 deficiency and the ‘endurance’/oxidative muscle phenotype that is commonly associated with this condition