Fitness is a determinant of the metabolic response to endurance training in adolescents at risk of type 2 diabetes mellitus

Increasing aerobic exercise intensity fails to consistently improve the glycemic response in people living with prediabetes or type 2 diabetes mellitus: the INTENSITY trial

Some individuals with prediabetes or type 2 diabetes mellitus (T2DM) who engage in exercise will not experience the anticipated improvements in glycemic control, referred to as non-responders. Increasing exercise intensity may improve the proportion of individuals who become responders. The objectives were to (i) identify responders and non-responders based on changes in glycated hemoglobin (HbA1c) in individuals with prediabetes or T2DM following 16 weeks of aerobic exercise; (ii) investigate if increasing exercise intensity enhances the responders' status for individuals not previously responding favourably to the intervention. Participants (n = 40; age = 58.0 years (52.0-66.0); HbA1c = 7.0% (6.0-7.2)) engaged in a two-phase, randomized study design. During phase one, participants performed 16 weeks of treadmill-based, supervised, aerobic exercise at 4.5 metabolic equivalents (METs) for 150 min per week. Thereafter, participants were categorized as responders, non-responders, or unclear based on the 90% confidence interval above, below, or crossing a 0.3% reduction in HbA1c. For phase two, participants were randomized to a maintained intensity (4.5 METs) or increased intensity (6.0 METs) group for 12 weeks. Following phase one, two (4.1%) participants were categorized as responders, four (8.2%) as non-responders, and 43 (87.7%) as unclear. Following phase two, two from the increased intensity group and one from the maintained intensity group experienced an improvement in response categorization. There were no significant between or within group (maintained vs. increased) differences in HbA1c. For most people with prediabetes or T2DM, increasing exercise intensity by 1.5 METs does not improve response categorization.

Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial

Limited data exist regarding the impact of an acute bout of exercise with varying intensities on irisin levels in the youth of different obesity statuses. The objectives were to (1) compare an acute bout of moderate continuous intensity (MCI) exercise and an acute bout of high‐intensity interval training (HIIT) on irisin response in youth with different obesity statuses and, (2) investigate whether changes in irisin levels are correlated with exploratory outcomes. A randomized crossover design study was conducted on 25 youth aged 12–18 years old. Participants were classified as either healthy weight (BMI percentile <85; n = 14) or overweight/obese (BMI percentile ≥85; n = 11). Participants performed an MCI exercise session at 50% of heart rate reserve for 35 min and a HIIT exercise session for 35 min, with intervals every 5 min increasing from 50% heart rate reserve to 85–90% for 2 min. Irisin was measured using an enzyme‐linked immunoabsorbent assay from plasma sampling obtained throughout the exercise (at times 0, 7, 14, 21, 28, and 35 min). A time effect was observed throughout the HIIT session [F(1,5) = 6.478, p < 0.001]. Bonferonni post‐hoc analysis revealed significant differences in irisin levels post‐exercise (35 min) compared to times 7, 14, 21, and 28 min. Irisin increased during HIIT (81.0% ± 71.3; p = 0.012) in youth with a healthy weight. No differences were observed for youth living as overweight or with obesity. Overall, HIIT elicits a higher peak irisin response compared to MCI exercise training in youth.

Vigorous physical activity is important in maintaining a favourable health trajectory in active children: the CHAMPS Study-DK

Physical activity (PA) is critical to improving health factors such as weight, adiposity, and aerobic fitness. However, children who meet PA guideline recommendations demonstrate developmental differences in health-related outcomes. To investigate prospective associations between PA behaviour (overall PA and PA intensity) and trajectories of health-related factors among physically active children. This prospective study (2.5 years) included 391 children (baseline age: 8.1 ± 1.4 years; girls 36.3%) from ten public schools. All children performed 60-min or more of moderate-to-vigorous physical activity (MVPA) per day objectively measured. Trajectories of BMI, waist circumference, and aerobic fitness were constructed with a group-based multi-trajectory model. Three trajectory subgroups were identified: ‘high fitness/normal weight’ (48.4% of children), ‘moderate fitness /normal weight’ (42.5% of children), and ‘low fitness/overweight-obese’ (9.1% of children). Children performing higher overall PA, were less likely of being classified as members of the ‘Low Fitness/Overweight-Obese’ [Relative Risk Ratio (RRR and 95% CI) = 0.56 (0.37 to 0.85) compared to ‘high fitness/normal weight’ subgroup. Each additional 5% in light PA time was associated with approximately twofold [RRR 2.12 (1.24–3.61)] increased risk of being in the ‘low fitness/overweight-obese’ trajectory relative to the ‘high fitness/normal weight’ trajectory. Each additional 2% in vigorous-PA time was associated with a 42% and 85% reduced risk (relative to ‘high fitness/normal weight’) of being in the ‘moderate fitness/normal weight’ [RRR 0.58 (0.38–0.96)] and ‘low fitness/overweight-obesity’ [RRR 0.15 (0.06–0.37)] trajectory, respectively. Overall PA and additional time in vigorous-PA was associated with improved health-related outcomes, while light PA was negatively associated with health-related outcomes among children who adhere to PA guideline recommendations. Vigorous PA was the strongest predictor of the health trajectories. All PA guidelines for children should place greater emphasis on the importance of vigorous PA.

Directions for Exercise Treatment Response Heterogeneity and Individual Response Research

Treatment response heterogeneity and individual responses following exercise training are topics of interest for personalized medicine. Proposed methods to determine the contribution of exercise to the magnitude of treatment response heterogeneity and categorizing participants have expanded and evolved. Setting clear research objectives and having a comprehensive understanding of the strengths and weaknesses of the available methods are vital to ensure the correct study design and analytical approach are used. Doing so will ensure contributions to the field are conducted as rigorously as possible. Nonetheless, concerns have emerged regarding the ability to truly isolate the impact of exercise training, and the nature of individual responses in relation to mean group changes. The purpose of this review is threefold. First, the strengths and limitations associated with current methods for quantifying the contribution of exercise to observed treatment response heterogeneity will be discussed. Second, current methods used to categorize participants based on their response to exercise will be outlined, as well as proposed mechanisms for factors that contribute to response variation. Finally, this review will provide an overview of some current issues at the forefront of individual response research.

Effects of sprint interval training on substrate oxidation in adults living with and without obesity: The i-FLEX study

Metabolic flexibility is the ability to adapt substrate oxidation according to metabolic demand. Exercise increases fat oxidation responses in individuals living with obesity; however, limited research exists on the relationship between substrate oxidation and insulin sensitivity after sprint interval training (SIT). The primary objective was to investigate changes in substrate oxidation at rest and during submaximal exercise, and in insulin sensitivity after 4 weeks of SIT in individuals living with or without obesity. The secondary objective was to investigate correlations between changes in substrate oxidation and insulin sensitivity following SIT. Adults living with obesity (n = 16, body mass index (BMI) = 34.1 kg/m2  ± 3.8) and without obesity (n = 18, BMI = 22.9 kg/m2  ± 1.6) took part in a 4-week SIT intervention. Participants completed three sessions of SIT per week, consisting of repeated sets of a 30-s Wingate separated by 4 m of active recovery. Substrate oxidation at rest and during submaximal exercise was measured using VCO2 /VO2 . Insulin sensitivity was calculated using the Matsuda index. No difference in substrate oxidation at rest was observed for either group (p > 0.05), while a significant increase in fat oxidation was observed in individuals living with obesity [F(1,31) = 14.55, p = 0.001] during the submaximal exercise test. A significant decrease in insulin sensitivity was observed among individuals without obesity [F(1,31) = 5.010, p = 0.033]. No correlations were observed between changes in substrate oxidation and insulin sensitivity (p > 0.05). Following SIT, individuals living with obesity increased submaximal fat oxidation compared to individuals without obesity. No correlations were observed between substrate oxidation and insulin sensitivity. Thus, SIT impacts fat oxidation during exercise in individuals living with obesity while having no such influence on insulin sensitivity.

Can non-responders be 'rescued' by increasing exercise intensity? A quasi-experimental trial of individual responses among humans living with pre-diabetes or type 2 diabetes mellitus in Canada

INTRODUCTION

Exercise is recommended to improve glycaemic control. Yet, individual changes in glycaemic control following exercise can vary greatly, meaning while some significantly improve others, coined 'non-responders', do not. Increasing the intensity of exercise may 'rescue' non-responders and help generate a response to training. This trial will identify non-responders to changes in glycated haemoglobin (HbA1c) across inactive individuals living with pre-diabetes or type 2 diabetes mellitus following an aerobic exercise programme and evaluate if increasing training intensity will elicit beneficial changes to 'rescue' previously categorised non-responders.

METHODS AND ANALYSIS

This study will recruit 60 participants for a two-phase aerobic exercise training programme. Participants will be allocated to a control group or assigned to an intervention group. Control participants will maintain their current lifestyle habits. During phase 1, intervention participants will complete 16 weeks of aerobic exercise at an intensity of 4.5 metabolic equivalents (METs) for 150 min per week. Participants will then be categorised as responders or non-responders based on the change in HbA1c. For phase 2, participants will be blocked based on responder status and randomly allocated to a maintained intensity, or increased intensity group for 12 weeks. The maintained group will continue to train at 4.5 METs, while the increased intensity group will train at 6.0 METs for 150 min per week.

ETHICS AND DISSEMINATION

Results will be presented at scientific meetings and submitted to peer-reviewed journals. Publications and presentations related to the study will be authorised and reviewed by all investigators. Findings from this study will be used to provide support for future randomised control trials. All experimental procedures have been approved by the Research Ethics Board at the University of New Brunswick (REB: 2018-168).

TRIAL REGISTRATION NUMBER

NCT03787836.

Interindividual variation in cardiometabolic health outcomes following 6 months of endurance training in youth at risk of type 2 diabetes mellitus

This study determined the interindividual variation in the cardiometabolic response to 6 months of moderate or vigorous intensity exercise training (ET) among youth at risk for type 2 diabetes mellitus. Youth were randomized to moderate intensity ET (45-55% heart rate reserve; n = 31), vigorous intensity ET (70-85% heart rate reserve; n = 37), or control (n = 36). Only those attending ≥70% of ET sessions were included. Cardiometabolic measures included insulin sensitivity, hepatic triglyceride content, visceral adipose area, and cardiorespiratory fitness. The contribution of ET to interindividual variation was determined using the standard deviation of individual responses (SD_IR) and considered meaningful if the SD_IR surpassed the smallest worthwhile difference (SWD), calculated as 0.2 × the standard deviation of the control group baseline values. ET meaningfully contributed to the interindividual variation among changes in peak oxygen uptake following moderate (SD_IR: 2.04) and vigorous (SD_IR: 3.43) ET (SWD: 1.17 mL·kg fat free mass^-1·min^-1), body fat percentage and hepatic triglyceride content following moderate-intensity ET (SD_IR: 1.64, SWD: 1.05%; SD_IR: 10.08, SWD: 1.06%, respectively), and visceral fat mass following vigorous ET (SD_IR: 11.06, SWD: 7.13 cm²). Variation in the changes in insulin sensitivity were not influenced by ET. The contribution of ET to interindividual variation appears to be influenced by the desired outcome and prescribed intensity. Trial registration at ClinicalTrials.gov (identifier no.: NCT00755547). Novelty: The contribution of exercise to interindividual variation following training depends on the outcome and exercise intensity. Increasing exercise intensity does not systematically reduce non-response among youth at risk for type 2 diabetes.

Developmental Trajectories of Body Mass Index, Waist Circumference, and Aerobic Fitness in Youth: Implications for Physical Activity Guideline Recommendations (CHAMPS Study-DK)

OBJECTIVES

Describe the trajectories of body mass index (BMI), waist circumference, and aerobic fitness in children and identify different outcomes of guideline-recommended physical activity (PA) in a subset of active children.

METHODS

We recruited students from 10 public primary schools and obtained repeated measures of BMI, waist circumference, and aerobic fitness over 30 months. Aerobic fitness was measured with the Andersen test. We objectively measured physical activity behaviour with accelerometers and classified children as 'physically active' when they achieved ≥ 60 min of moderate-to-vigorous PA per day (guideline concordance). Univariate trajectories of BMI, waist circumference, and aerobic fitness were calculated for all children, and we constructed a multi-trajectory model comprising all outcomes in the subgroup of physically active children. The construct validity of all models was investigated by examining for between-group differences in cardiovascular disease risk factors obtained from fasting blood samples.

RESULTS

Data from 1208 children (53% female) with a mean (SD) age of 8.4 (1.4) years were included. The univariate trajectory models identified three distinct trajectories for BMI, waist circumference, and aerobic fitness. The multi-trajectory model classified 9.1% of physically active children as following an 'overweight/obese/low fitness' trajectory. There were moderate-to-large differences in cardiovascular risk factors between all trajectory groups (p < 0.001; d = 0.4-1.20).

CONCLUSION

We identified distinct developmental trajectories of BMI, waist circumference, and aerobic fitness in children. Nearly one in 10 children who met PA guideline recommendations followed an unfavourable health trajectory. Health-related PA recommendations may be insufficient for some children.

Prevalence of responders for hepatic fat, adiposity and liver enzyme levels in response to a lifestyle intervention in children with overweight/obesity: EFIGRO randomized controlled trial

BACKGROUND/OBJECTIVE

Exercise and lifestyle interventions have been shown to reduce hepatic fat (HF) and adiposity in youth. However, the interindividual response in HF after a lifestyle intervention with or without exercise in children is unknown. The aim of the present study was to compare interindividual variability for HF, adiposity, gamma-glutamyl transferase (GGT), and the aspartate aminotransferase to alanine aminotransferase ratio (AST/ALT) in children with overweight/obesity participating in a 22-week lifestyle intervention with (intensive intervention) or without exercise (control intervention).

METHODS

Data from 102 children (9-12 years, 55% girls) with overweight/obesity participating in the EFIGRO randomized controlled trial were analyzed. Percentage HF (magnetic resonance imaging), weight, body and fat mass index (BMI and FMI), GGT, AST/ALT, cardiorespiratory fitness (CRF, 20 meters shuttle run test) were assessed before and after the intervention by the same trained researchers. The control intervention consisted in 11 sessions of a family-based lifestyle and psycho-educational program. The intensive intervention included the control intervention plus supervised exercise (3 sessions/week).

RESULTS

The prevalence of responders for HF (54% vs. 34%), weight (27% vs. 11%), BMI (71% vs. 47%), FMI (90% vs. 60%), and GGT (69% vs. 39%) was higher in the intensive than in the control group (Ps < 0.05). Responders for weight (16 ± 3 vs. 6 ± 2 laps) and BMI (11 ± 2 vs. 3 ± 4 laps) improved more CRF levels than non-responders (Ps < 0.05).

CONCLUSIONS

The addition of exercise to a lifestyle intervention may increase the responder rates for HF, adiposity, and GGT in children with overweight/obesity. Improvements in CRF may explain differences between weight and BMI responders and non-responders.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02258126.

Evaluation of Metabolic Syndrome and Its Associated Risk Factors in Type 2 Diabetes: A Descriptive Cross-Sectional Study at the Komfo Anokye Teaching Hospital, Kumasi, Ghana

Background. Metabolic syndrome (MS) is a collection of cardiovascular risk factors comprising insulin resistance, dyslipidemia, obesity, and hypertension, which may cause further complications in diabetes. Although metabolic syndrome (MS) is increasing in incidence in diabetics and leading to significant cardiovascular diseases and mortality, there is dearth of data in Ghana. This study investigated metabolic syndrome, its prevalence, and its associated risk factors in type 2 diabetes at the Komfo Anokye Teaching Hospital, Kumasi, Ghana. Methods. The study involved 405 diabetic patients attending the Diabetic Clinic of the Komfo Anokye Teaching Hospital (KATH) Kumasi, in the Ashanti Region of Ghana. A well-structured questionnaire was used to obtain demographic background such as their age and gender. Anthropometric measurements were obtained using the Body Composition Monitor (Omron ® 500, Germany) which generated digital results on a screen and also by manual methods. Fasting venous blood was collected for the measurement of biochemical parameters comprising fasting plasma glucose (FPG), glycated haemoglobin (HbA1c), high density lipoprotein cholesterol (HDL-c), and triglyceride (TG). Metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). Results. Out of the total of 405 participants, 81 were males and 324 were females, and the estimated mean age was 58.5 ± 9.9 years. The female patients exhibited higher mean waist circumference (WC) and mean hip circumference (HC) as well as an approximately higher body mass index than males (28.3 ± 5.1, 26.5 ± 4.2 for the female and male respectively). Overall, the prevalence of metabolic syndrome observed among the study population was 90.6%. Conclusions. The prevalence of metabolic syndrome observed among the study population was 90.6%, with a higher percentage in females than males. High triglyceride levels and high waist circumference were the main risk factors for MS in the diabetic population.

Exercise-induced irisin release as a determinant of the metabolic response to exercise training in obese youth: the EXIT trial

The mechanisms underlying the metabolic improvements following aerobic exercise training remain poorly understood. The primary aim of this study was to determine if an adipomyokine, irisin, responded to acute exercise was associated with the metabolic adaptations to chronic aerobic exercise in obese youth. The acute response to exercise was assessed in 11 obese youth following 45‐min acute bouts of aerobic (AE) and resistance exercise (RE). The irisin area under the curve (pre‐exercise, 15, 30, and 45 min) during these AE sessions were the main exposure variables. The primary outcome measure was the change in insulin sensitivity using the Matsuda index, following 6 weeks of RE training, delivered for 45 min, three times per week at 60–65% 1RM. Participants were also categorized as either responders (above) or nonresponders (below) based on the percentage change in the Matsuda index following the 6‐week intervention. Irisin increased significantly during the acute bout of AE from 29.23 ± 6.96 to 39.30 ± 7.05 ng/mL; P = 0.028, but not significantly during the RE session (P = 0.182). Absolute and relative change in irisin during the acute bout of AE was associated with absolute and relative change in Matsuda index (r = 0.68; P = 0.022 and r = 0.63; P = 0.037) following the 6‐week RE intervention. No such association was observed with the irisin response to acute RE (all P > 0.05). Responders to the 6‐week RE intervention displayed a fourfold greater irisin response to acute AE (90.0 ± 28.0% vs. 22.8 ± 18.7%; P = 0.024) compared to nonresponders. Irisin increases significantly following an acute bout of AE, but not RE, and this response is associated with a greater improvement in insulin sensitivity in response to chronic resistance training.

Effects of an exercise program on hepatic metabolism, hepatic fat, and cardiovascular health in overweight/obese adolescents from Bogotá, Colombia (the HEPAFIT study): study protocol for a randomized controlled trial

Background

A considerable proportion of contemporary youth have a high risk of obesity-related disorders such as cardiovascular disease, metabolic syndrome, or non-alcoholic fatty liver disease (NAFLD). Although there is consistent evidence for the positive effects of physical activity on several health aspects, most adolescents in Colombia are sedentary. It is, therefore, important to implement strategies that generate changes in lifestyle. The HEPAFIT study aims to examine whether a 6-month exercise program has benefits for hepatic fat content and cardiovascular health outcomes among overweight/obese adolescents from Bogotá, Colombia.

Methods/design

Altogether, 100 hundred overweight/obese, sedentary adolescents (aged 11–17 years) attending two public schools in Bogotá, Colombia, will be included in a parallel-group randomized controlled trial. Adolescents will be randomly assigned to an intervention group following one of four curricula: (1) the standard physical education curriculum (60 min per week of physical activity, n = 25) at low-to-moderate intensity; (2) a high-intensity physical education curriculum (HIPE, n = 25), consisting of endurance and resistance games and non-competitive activities, such as running, gymkhanas, lifting, pushing, wrestling, or hauling, for 60-min sessions, three times per week, with an energy expenditure goal of 300 to 500 kcal/session at 75–85% maximum heart rate (HRmax); (3) a low-to-moderate intensity physical education curriculum (LIPE, n = 25) consisting of endurance and resistance games and non-competitive activities (e.g., chasing, sprinting, dribbling, or hopping) for 60-min sessions, three times per week with an energy expenditure goal of 300 kcal/session at 55–75% HRmax; and (4) a combined HIPE and LIPE curriculum (n = 25). The HIPE, LIPE, and combined interventions were performed in addition to the standard physical education curriculum. The primary outcome for effectiveness is liver fat content, as measured by the controlled attenuation parameter 1 week after the end of the intervention program.

Discussion

The translational focus may be suitable for collecting new information in a school setting on the possible effects of physical activity interventions to reduce liver fat content and to improve metabolic profiles and the cardiometabolic health of overweight/obese adolescents. This may lead to the more efficient use of school physical education resources.

Trial registration

ClinicalTrials.gov, NCT02753231. Registered on 21 April 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2721-5) contains supplementary material, which is available to authorized users.

Effect of a pilot multi-component intervention on motor performance and metabolic risks in overweight/obese youth

This study evaluated the effect of a multi-component intervention on motor performance (MP) and metabolic risk markers (MRM) in overweight/obese youth. A secondary aim was to examine whether changes in MP are associated to changes in MRM. A 3-month multi-component intervention was performed, consisting of physical exercise sessions (twice/week;1h), nutritional education sessions (once/month), and parental support (twice/week). The sample included 35 volunteers (7-13 y.o), allocated to intervention (INT, n = 17) and control (CONT, n = 18) group. Variables were measured pre (T0) and post intervention (T1). Fasting blood samples were analyzed for MRM. MP tests included the measurement of health related physical fitness components and motor coordination performance (KTK battery). To assess food intake, a 24-hour recall diary was used. GLM-ANCOVA was performed. Standardized scores were calculated for the outcome variables, and multilinear regressions were applied to analyze associations between the key variables. INT group showed improvements in MP, glycolytic and hepatic profiles. After adjustments for MVPA, SB, total intake and maturational stage, negative associations between %ΔMP and %Δglycolytic (β = -.424; 95%CI:-0.343:-0.022), and %Δhepatic scores (β = -.382 95%CI:-0.001:-0.009) were observed. The intervention produced a moderate-to-high effect on the MP and some MRM. Changes in MP were inversely associated with changes in glycolytic and hepatic markers.

Cardiorespiratory fitness, waist circumference and liver enzyme levels in European adolescents: The HELENA cross-sectional study

OBJECTIVES

(1) To examine whether cardiorespiratory fitness (CRF) is related to liver enzyme levels independent of waist circumference (WC), and (2) To test whether having a high CRF is associated with an improved liver enzyme profile with a high WC.

DESIGN

Cross-sectional.

METHODS

CRF (20m-shuttle-run test) and WC were assessed in 811 European adolescents (48.5% males) aged 12.5-17.5 years. Fatty liver biomarkers included fasting serum alanine-aminotransferase (ALT), gamma-glutamyl-transpeptidase (GGT) and the aspartate-aminotransferase to ALT (AST/ALT) ratio. Participants were categorized as fit or unfit (CRF below or above 43.8mL/kg/min and 34.6mL/kg/min, for boys and girls, respectively) and as high or non-high WC (sex and age-specific cut-offs).

RESULTS

CRF was associated with ALT (β=-0.106; p=0.049) and GGT levels (β=-0.225; p<0.001) and AST/ALT ratio (β=0.234; p<0.001), yet these relationships were attenuated after further controlling for WC (all p>0.1). High WC and fit adolescents had lower ALT levels (28±1U/L vs. 23±2U/L, unfit and fit respectively, p=0.018) and higher AST/ALT ratio (0.94±0.04 vs. 1.10±0.06, unfit and fit respectively, p=0.010) than those who were high WC but unfit.

CONCLUSIONS

The results showed that CRF is not independently associated with liver enzymes, and that WC is a stronger predictor in adolescents. These findings also suggest that high CRF may have specific protective effects on liver enzyme levels in adolescents with high WC. Exercise programs focused on increasing CRF and decreasing abdominal adiposity could be a good alternative in the treatment and prevention of obesity related fatty liver disease in adolescents.

Vascular repair strategies in type 2 diabetes: novel insights

Impaired functions of vascular cells are responsible for the majority of complications in patients with type 2 diabetes (T2D). Recently a better understanding of mechanisms contributing to development of vascular dysfunction and the role of systemic inflammatory activation and functional alterations of several secretory organs, of which adipose tissue has more recently been investigated, has been achieved. Notably, the progression of vascular disease within the context of T2D appears to be driven by a multitude of incremental signaling shifts. Hence, successful therapies need to target several mechanisms in parallel, and over a long time period. This review will summarize the latest molecular strategies and translational developments of cardiovascular therapy in patients with T2D.

Targeting skeletal muscle mitochondria to prevent type 2 diabetes in youth

The prevalence of type 2 diabetes (T2D) has increased dramatically over the past two decades, not only among adults but also among adolescents. T2D is a systemic disorder affecting every organ system and is especially damaging to the cardiovascular system, predisposing individuals to severe cardiac and vascular complications. The precise mechanisms that cause T2D are an area of active research. Most current theories suggest that the process begins with peripheral insulin resistance that precedes failure of the pancreatic β-cells to secrete sufficient insulin to maintain normoglycemia. A growing body of literature has highlighted multiple aspects of mitochondrial function, including oxidative phosphorylation, lipid homeostasis, and mitochondrial quality control in the regulation of peripheral insulin sensitivity. Whether the cellular mechanisms of insulin resistance in adults are comparable to that in adolescents remains unclear. This review will summarize both clinical and basic studies that shed light on how alterations in skeletal muscle mitochondrial function contribute to whole body insulin resistance and will discuss the evidence supporting high-intensity exercise training as a therapy to circumvent skeletal muscle mitochondrial dysfunction to restore insulin sensitivity in both adults and adolescents.