Insulin sensitivity in physically fit and unfit children of parents with Type 2 diabetes

Decreased arterial distensibility and postmeal hyperinsulinemia in young Japanese women with family history of diabetes

INTRODUCTION

To assess vascular function and characterize insulin secretion using a physiological approach in Japanese women with family history of type 2 diabetes (FHD).

RESEARCH DESIGN AND METHODS

Standardized mixed-meal tests were performed with multiple postprandial glucose, insulin and free fatty acids (FFA) measurements over a 30-120 min period in 31 Japanese women aged 21-24 years. Arterial distensibility was assessed as well.

RESULTS

Fasting glucose, triglyceride and insulin averaged <90 mg/dL, <60 mg/dL and <5 μU/mL, respectively, and did not differ cross-sectionally between 10 with (FHD+) and 21 without FHD (FHD-). FHD+ showed higher insulin responses not only during the first 30 min (p=0.005) but also during the second hour (60-120 min, p<0,05) in spite of identical postprandial suppression of FFA and identical fasting and postprandial glucose and FFA concentrations, except for higher 60 min FFA in FHD+. Further, FHD+ had decreased arterial distensibility (p=0.003). On multivariate regression analysis, arterial distensibility emerged as the only significant independent predictor of FHD+. Endurance training in FHD+ did not alter decreased arterial distensibility whereas it abolished postprandial hyperinsulinemia.

CONCLUSIONS

FHD was associated with decreased arterial distensibility and postprandial hyperinsulinemia despite nearly identical postprandial glycemia and postprandial FFA suppression, suggesting that impaired vascular insulin sensitivity may precede glucose and lipid dysmetabolism in normal weight Japanese women aged 22 years.

Special Article: Physical Activity, Physical Fitness, and Cardiovascular Risk Factors in Childhood

In adults, physical activity and exercise training are associated with reduced cardiovascular morbidity and mortality, a reduced likelihood of developing adverse cardiovascular risk factors, and improved insulin sensitivity. In childhood, participation in appropriate physical activity may prevent the development of cardiovascular risk factors in the future and complement treatment of existing cardiovascular risk factors, including hypertension, dyslipidemia, and overweight. Exercise in children can also significantly improve insulin sensitivity independent of weight loss. These e fects are mediated in overweight children by increases in lean body mass relative to fat mass and associated improvements in inflammatory mediators, endothelial function, and the associated adverse hormonal milieu.

Glucose metabolism in discordant monozygotic twins for cardiorespiratory fitness

OBJECTIVE

To determine if glucose and insulin concentrations are regulated by cardiorespiratory fitness (VO2max) regardless of their genetic effects.

METHODS

This cross-sectional study enrolled 38 pairs of young monozygotic twins (11 to 18 years-old). All subjects underwent a progressive maximal exercise test on a treadmill to determine the VO2max with gas exchange analysis (MedGraphics VO2000® - Medical Graphics Corp., St. Paul, MN). Blood samples were drawn after fasting to determine glucose and insulin levels. Monozygosity was confirmed by genotyping 15 informative genetic markers. Nine pairs had at least 10mL.kg-1.min-1 difference in VO2max and were divided into the more and less active group, according to their VO2max. Mean differences between more and less active groups were evaluated by Wilcoxon's test for paired data.

RESULTS

On average, twins from the more active group presented a 17% (13.5±3.7mL.kg-1.min-1) higher VO2max compared to their less active siblings. No significant differences were observed between the groups for fasting insulin (36.5±34.6 versus 25.3±13.7mg/dL; p<0.813). However, the more active twins had lower fasting glucose than the less active ones (82.9±7.3 versus 86.7±7.6mg/dL; p<0.010).

CONCLUSIONS

In this case-control study (discordant monozygotic twins), the less active co-twins were characterized by higher fasting plasma glucose levels. This implies that poor cardiorespiratory fitness can be associated with defective glucose metabolism regardless of genetic factors.

Metabolic flexibility and obesity in children and youth

The concept of metabolic flexibility describes the ability of skeletal muscle to switch between the oxidation of lipid as a fuel during fasting periods to the oxidation of carbohydrate during insulin stimulated period. Alterations in energy metabolism in adults with obesity, insulin resistance and/or type 2 diabetes induce a state of impaired metabolic flexibility, or metabolic inflexibility. Despite the increase in the prevalence of type 2 diabetes in obese children and youth, less is known about the factors involved in the development of metabolic inflexibility in the paediatric population. Metabolic flexibility is conditioned by nutrient partitioning in response to feeding, substrate mobilization and delivery to skeletal muscle during fasting or exercising condition, and skeletal muscle oxidative capacity. Our aim in this review was to identify among these factors those making obese children at risk of metabolic inflexibility. The development of ectopic rather than peripheral fat storage appears to be a factor strongly linked with a reduced metabolic flexibility. Tissue growth and maturation are determinants of impaired energy metabolism later in life but also as a promising way to reverse metabolic inflexibility given the plasticity of many tissues in youth. Finally, we have attempted to identify perspectives for future investigations of metabolic flexibility in obese children that will improve our understanding of the genesis of metabolic diseases associated with obesity.

Exercise training reverses impaired skeletal muscle metabolism induced by artificial selection for low aerobic capacity

We have used a novel model of genetically imparted endurance exercise capacity and metabolic health to study the genetic and environmental contributions to skeletal muscle glucose and lipid metabolism. We hypothesized that metabolic abnormalities associated with low intrinsic running capacity would be ameliorated by exercise training. Selective breeding for 22 generations resulted in rat models with a fivefold difference in intrinsic aerobic capacity. Low (LCR)- and high (HCR)-capacity runners remained sedentary (SED) or underwent 6 wk of exercise training (EXT). Insulin-stimulated glucose transport, insulin signal transduction, and rates of palmitate oxidation were lower in LCR SED vs. HCR SED (P < 0.05). Decreases in glucose and lipid metabolism were associated with decreased β₂-adrenergic receptor (β₂-AR), and reduced expression of Nur77 target proteins that are critical regulators of muscle glucose and lipid metabolism [uncoupling protein-3 (UCP3), fatty acid transporter (FAT)/CD36; P < 0.01 and P < 0.05, respectively]. EXT reversed the impairments to glucose and lipid metabolism observed in the skeletal muscle of LCR, while increasing the expression of β₂-AR, Nur77, GLUT4, UCP3, and FAT/CD36 (P < 0.05) in this tissue. However, no metabolic improvements were observed following exercise training in HCR. Our results demonstrate that metabolic impairments resulting from genetic factors (low intrinsic aerobic capacity) can be overcome by an environmental intervention (exercise training). Furthermore, we identify Nur77 as a potential mechanism for improved skeletal muscle metabolism in response to EXT.

Exercise prescription and the patient with type 2 diabetes: a clinical approach to optimizing patient outcomes

PURPOSE

To review the current recommendations for physical activity in type 2 diabetes mellitus (T2DM) and propose methods to optimize compliance, reduce the pharmaceutical burden, and improve the general health and well-being of patients with T2DM.

DATA SOURCES

PubMed, SportDiscus, Ovid MEDLINE, Psychinfo, Web of Science, LexisNexis, and EBM reviews.

CONCLUSIONS

T2DM is a condition in which physical activity has been documented to improve patient outcomes, yet research has noted that healthcare professionals inadequately address this issue, resulting in physical activity being an underutilized therapy.

IMPLICATIONS FOR PRACTICE

An exercise prescription consists of mode (type), frequency, intensity, duration, and progression. Determining the appropriate mode depends upon patient preference and safety issues regarding the state of T2DM or other conditions. Frequency, intensity, and duration are specific to the type of activity and should be tailored to the patient's abilities to safely perform the activity. Finally, the health professional addresses periodic progression in order to maintain the exercise stimulus needed to promote continued health improvements and prevent "plateauing." In this article, on the basis of the current scientific research, we propose recommendations that enable healthcare professionals to advocate for their patients with T2DM by offering safe and effective treatment options.

Erythrocyte fatty acid composition and insulin sensitivity in daughters of Type 2 diabetic patients and women with no family history of diabetes

BACKGROUND

There is evidence that the impact of environmental factors on insulin sensitivity is modified by the presence of family history of diabetes.

AIM

To compare the association between the erythrocyte phospholipid fatty acid composition (a biomarker of dietary fatty acids) and insulin sensitivity in daughters of Type 2 diabetic patients with the corresponding association in women without family history of diabetes.

MATERIAL/SUBJECTS AND METHODS

Eighteen offspring of Type 2 diabetic patients [age 30+/-6.5 yr; body mass index (BMI) 22.2+/-2.5 kg/m2; body fat 31.8+/-5.1%] and 18 matched women (age 30.1+/-6.8 yr; BMI 22.2+/-1.8 kg/m2; body fat 32.2+/-6.0%) participated in the study.

RESULTS

Insulin Sensitivity Index (ISI)-Matsuda tended to be lower (p=0.06) in the Offspring than the control group. Weight proportions of erythrocyte phospholipid saturated (SFA), polyunsaturated (PUFA), and monounsaturated fatty acids (MUFA) were similar between the two groups. In the offspring, erythrocyte total SFA were negatively correlated with ISI-Matsuda [r=-0.47, p<0.05), ISI(gly)-Belfiore (r=-0.52, p<0.05) and ISI(ffa)-Belfiore (r=-0.53, p<0.05)], whereas total PUFA were positively correlated with insulin sensitivity [ISI-Matsuda, r=0.46, p<0.05; ISI(gly)-Belfiore, r=0.53, p<0.05; ISI(ffa)-Belfiore, r=0.54, p<0.05]. No significant correlations were observed in the control group.

CONCLUSIONS

The associations between erythrocyte fatty acid composition and insulin sensitivity are distinct between daughters of Type 2 diabetic patients and women without family history of diabetes.

Exercise training has greater effects on insulin sensitivity in daughters of patients with type 2 diabetes than in women with no family history of diabetes

AIMS/HYPOTHESIS

Sedentary offspring of patients with type 2 diabetes are often more insulin-resistant than persons with no family history of diabetes, but when active or fit offspring of type 2 diabetic patients are compared with non-diabetic persons, differences in insulin resistance are less evident. This study aimed to determine the effects of an exercise training intervention on insulin sensitivity in both groups.

METHODS

Women offspring (n = 34) of type 2 diabetic patients (offspring age 35.6 +/- 7.0 years, BMI 28.1 +/- 5.1 kg/m(2)) and 36 matched female controls (age 33.6 +/- 6.1 years, BMI 27.3 +/- 4.7 kg/m(2)) participated. Body composition, fitness and metabolic measurements were made at baseline and after a controlled 7 week exercise intervention.

RESULTS

At baseline, insulin sensitivity index (ISI) was 22% lower in offspring than controls (p < 0.05), despite similar body fat and maximal oxygen uptake (.VO(2max)) values in the two groups. ISI increased by 23% (p < 0.05) in offspring following the exercise intervention, compared with 7% (NS) in the controls. Increases in .VO(2max) were similar in both groups (controls 12%, offspring 15%, p < 0.05 for both). Plasma leptin concentrations decreased significantly in the offspring (-24%, p < 0.01) but not in controls (0%, NS). Change in ISI correlated significantly with baseline ISI (r = -0.47, p < 0.0005) and change in leptin (r = -0.43, p < 0.0005). The latter relationship was not attenuated by adjustment for changes in body fat.

CONCLUSIONS/INTERPRETATION

Offspring, but not controls, significantly increased ISI in response to an exercise intervention, indicating that insulin sensitivity is more highly modulated by physical activity in daughters of patients with type 2 diabetes than in women with no family history of the disease.

Fatness, fitness, and insulin sensitivity among 7- to 9-year-old children

OBJECTIVE

The purpose of this study was to examine the relationships among fatness and aerobic fitness on indices of insulin resistance and sensitivity in children.

RESEARCH DESIGN AND METHODS

A total of 375 children (193 girls and 182 boys) 7 to 9 years of age were categorized by weight as normal-weight, overweight, or obese and by aerobic fitness based on a submaximal physical working capacity test (PWC). Fasting blood glucose (GLU) and insulin (INS) were used to calculate various indices of insulin sensitivity (GLU/INS), the homeostasis model assessment (HOMA), and the quantitative insulin sensitivity check index (QUICKI). Surrogate measures of pancreatic beta cell function included the insulinogenic index (INS/GLU) and the HOMA estimate of pancreatic beta-cell function (HOMA %B).

RESULTS

Insulin sensitivity and secretion variables were significantly different between the normal-weight children and the overweight and obese subjects. Fasting insulin (FI), HOMA, QUICKI, and INS/GLU were significantly different between the overweight and obese subjects. Likewise, the high fitness group possessed a better insulin sensitivity profile. In general, the normal-weight-high fit group possessed the best insulin sensitivity profile and the obese-unfit group possessed the worst insulin sensitivity profile. Several significant differences existed among the six fat-fit groups. Of particular note are the differences within BMI groups by fitness level and the comparison of values between the normal-weight-unfit subjects and the overweight and obese subjects with high fitness.

CONCLUSIONS

The results indicate that aerobic fitness attenuates the difference in insulin sensitivity within BMI categories, thus emphasizing the role of fitness even among overweight and obese children.

Physical activity, fitness and cardiovascular disease risk in adults: interactions with insulin resistance and obesity

There is a considerable body of evidence gathered from studies over the past half a century indicating that a high level of physical activity and a moderately high or high degree of cardiorespiratory fitness reduces the risk of CVD (cardiovascular disease). Recent data suggest that high levels of physical activity or fitness may be particularly beneficial to individuals with insulin-resistant conditions, such as the metabolic syndrome, Type II diabetes or obesity. These individuals, if unfit and sedentary, exhibit increased CVD risk, but their dose-response relationship for physical activity/fitness appears to be particularly steep such that, when they undertake high levels of activity (or have high fitness), their level of risk becomes closer to that of their normal weight or nondiabetic peers. This may be due to effects of physical activity in normalizing the metabolic dysfunction particularly associated with insulin-resistant conditions.

Early decrease of the percent of HOMA ɛ-cell function is independently related to family history of diabetes in healthy young nonobese individuals

OBJECTIVE

To determine the relationship between family history of diabetes (FHD) and decrease in percent of HOMA beta-cell function (HOMA-beta%) index in healthy betanon-obese Mexican subjects.

MATERIALS AND METHODS

Forty-eight individuals (30 women and 18 men) with FHD were compared vs 48 control subjects (30 women and 18 men) in a cross-sectional study matched by age, sex, and Waist-to-Hip ratio. Pregnancy, obesity, being overweight, alcohol consumption, high blood pressure, and heavy physical activity were exclusion criteria. All the participants were required to have a Body Mass Index < 25 kg/m2 and serum fasting and 2-hours postload glucose levels lower than 6.1 mmol/l and 7.8 mmol/l, respectively. The reciprocal of serum fasting insulin concentrations (1/Ins0) (microU/ml) and HOMA-B% index were used as indicators of insulin sensitivity and beta-cell function.

RESULTS

Average age was of 19.4 +/- 3.6 vs 19.8 +/- 2.6, P = 0.66 for the subjects with and without FHD. HOMA-beta% index was significantly lower in the subjects with FHD (186.1 +/- 74.1 vs 252.7 +/- 149.5, P = 0.01). For similar levels of insulin sensitivity, subjects with FHD showed lower HOMA-beta% index than control subjects (P < 0.001). Multivariate regression analysis showed a strong and independent relationship between FHD and decrease of HOMA-beta% index (OR 2.6, CI95% 1.2-4.3, P = 0.01).

CONCLUSIONS

This study shows that normal-weight offspring of type 2 diabetes subjects exhibited a significant decrease of HOMA-beta% index suggesting that FHD exerts an independent early negative effect on beta-cell function.

Association of physical inactivity with components of metabolic syndrome and coronary artery disease--the Chennai Urban Population Study (CUPS no. 15)

AIM

The aim of the study was to assess the influence of physical activity on the components of metabolic syndrome (MS) in an urban south Indian population in Chennai.

METHODS

The Chennai Urban Population Study (CUPS) is an epidemiological study involving two residential areas in Chennai in South India. Of the total of 1399 eligible subjects (age > or = 20 years), 1262 individuals participated in the study. MS was diagnosed based on modified Adult Treatment Panel (ATP) III guidelines. Details about the physical activity were collected using questionnaire, which included job-related and leisure-time activities, and specific questions on exercise. Study individuals were then graded as light, moderate and heavy using a scoring system. We assessed the relationship between the grades of physical activity and the components of MS and coronary artery disease (CAD). Insulin resistance was calculated using the homeostasis assessment model (HOMA-IR).

RESULTS

Prevalence of most of the components of MS (diabetes P < 0.001, obesity P = 0.003, abdominal obesity P < 0.001 and hypertension P < 0.001) and MS per se (P < 0.001) increased significantly with decrease in physical activity. Among non-diabetic subjects, HOMA-IR was significantly higher in subjects who did light-grade activity compared with heavy-grade activity (P = 0.041). Logistic regression analysis revealed physical activity to be significantly associated with MS [heavy activity: reference, moderate activity, odds ratio (OR) 1.639, (P = 0.017); light activity: OR 2.289, (P < 0.001)]. Subjects in the light-grade activity group also had higher odds of CAD (OR 2.42, 95% confidence interval 1.40, 4.24, P = 0.011), compared with the heavy-grade activity group.

CONCLUSION

Physical inactivity is associated with the components of MS and CAD in this urban south-Indian population. Lifestyle changes focusing on increasing physical activity could help to prevent the exploding epidemic of MS and CAD in India.