Correlations between measures of insulin sensitivity and weight loss

Evaluation of surrogate markers for insulin resistance for defining metabolic syndrome in urban Indian adolescents

OBJECTIVE

To compare parameters of insulin resistance, with special reference to McAuley index, in urban Indian adolescents, and to establish their cut-off values for defining metabolic syndrome.

DESIGN

Cross-sectional study.

SETTING

Schools located in four different geographical zones of Delhi, India.

PARTICIPANTS

695 apparently healthy adolescents grouped as normal weight (298), overweight (205) and obese (192).

OUTCOME MEASURES

Cut-off point for indices of insulin resistance was assessed by fasting insulin, insulin glucose ratio, and other methods (HOMA model, QUICKI, McAuley index) to define metabolic syndrome.

RESULTS

The McAuley index increased progressively from normal weight to obese adolescents in both sexes. McAuley index was significantly lower in adolescents with metabolic syndrome (5.36 ± 1.28 vs. 7.05 ± 1.88; P<0.001). McAuley index had the highest area under curve of receiver operator characteristics [0.82 (0.02)] as compared to other indices of insulin resistance. McAuley index of 6.23 had the highest specificity (88%) with sensitivity of 63.3% for diagnosing metabolic syndrome, whereas insulin glucose ratio had the highest sensitivity (79.7%) but low (55.5%) specificity. McAuley index was negatively correlated with height (r= -0.257, P=<0.001), weight (r= -0.537, P=<0.001), body mass index (r= -0.579, P<0.001), waist circumference (r= -0.542, p<0.001), and waist hip ratio (r= -0.268, P<0.001).

CONCLUSIONS

Among various parameters of insulin resistance, McAuley index had the highest specificity, and insulin glucose ratio had the highest sensitivity in diagnosing metabolic syndrome in urban Indian adolescents.

Effects of chronic calorie restriction or dietary resveratrol supplementation on insulin sensitivity markers in a primate, Microcebus murinus

The prevalence of diabetes and hyperinsulinemia increases with age, inducing metabolic failure and limiting lifespan. Calorie restriction (CR) without malnutrition delays the aging process, but its long-term application to humans seems difficult. Resveratrol (RSV), a dietary polyphenol, appears to be a promising CR mimetic that can be easily administered in humans. In this work, we hypothesized that both CR and RSV impact insulin sensitivity in a non-human primate compared to standard-fed control (CTL) animals. Four- to five-year-old male grey mouse lemurs (Microcebus murinus) were assigned to three dietary groups: a CTL group, a CR group receiving 30% fewer calories than the CTL and a RSV group receiving the CTL diet supplemented with RSV (200 mg·day(-1)·kg(-1)). Insulin sensitivity and glycemia were assessed using an oral glucose tolerance test (OGTT) and the homeostasis model assessment of insulin resistance (HOMA-IR index) evaluation after 21 or 33 months of chronic treatment. Resting metabolic rate was also measured to assess the potential relationships between this energy expenditure parameter and insulin sensitivity markers. No differences were found after a 21-month period of treatment, except for lower glucose levels 30 min after glucose loading in CR animals. After 33 months, CR and RSV decreased glycemia after the oral glucose loading without decreasing fasting blood insulin. A general effect of treatment was observed on the HOMA-IR index, with an 81% reduction in CR animals and 53% in RSV animals after 33 months of treatment compared to CTL. Chronic CR and dietary supplementation with RSV affected insulin sensitivity by improving the glucose tolerance of animals without disturbing their baseline insulin secretion. These results suggest that both CR and RSV have beneficial effects on metabolic alterations, although these effects are different in amplitude between the two anti-aging treatments and potentially rely on different metabolic changes.