Leptin concentrations and insulin sensitivity in normoglycemic men

Abstract

OBJECTIVE: Leptin is a hormone regulating weight in the mouse. Leptin regulates food intake and appetite. Leptin concentrations are increased in obese individuals suggesting resistance to its effect. However, there is considerable variability in leptin levels at each level of adiposity suggesting that environmental and genetic factors may regulate leptin concentrations. We examined whether subjects with decreased insulin sensitivity have increased leptin levels. METHODS: We used a radioimmunoassay to measure serum leptin levels and the hyperinsulinemic euglycemic clamp (with indirect calorimetry) to measure insulin sensitivity in 87 normoglycemic relatively lean men. RESULTS: Leptin levels were signi®cantly correlated with fasting insulin (r 0.58), insulin area (r 0.45), overall (r 70.57), non-oxidative (r 70.51) and oxidative (r 70.51) whole body glucose disposal (all P-values`0.001). After adjustment for body mass index, leptin levels remained signi®cantly correlated with fasting insulin (r 0.44), insulin area (r 0.40), overall (r 70.40), non-oxidative (r 70.28) and oxidative (r 70.33) whole body glucose disposal although the magnitude of the associations was considerably decreased. Leptin levels were signi®cantly related to insulin sensitivity in both less obese and more obese subjects. CONCLUSIONS: We conclude that leptin concentrations are related to insulin resistance and insulin concentrations in relatively lean normoglycemic men and these associations are to some extent independent of body mass index. Thus, subjects with insulin resistance may be relatively resistant to the effects of leptin.

Plasma leptin concentrations and obesity in relation to insulin resistance syndrome components among school children in Taiwan—The Taipei Children Heart Study

“…In a population of 87 lean men, Haffner et al showed plasma leptin levels were correlated with insulin levels and insulin sensitivity even after controlling for BMI. 23 We extend these results to children and further show that a single assessment of leptin is a better predictor of insulin resistance syndrome than WHR.…”

“…Leptin, obesity and insulin resistance syndrome among children N-F Chu et al Others also have found that insulin resistance is associated with elevated plasma leptin levels independent of body fat mass, 19,23,28,52 but these studies have been limited to adult populations. In a population of 87 lean men, Haffner et al showed plasma leptin levels were correlated with insulin levels and insulin sensitivity even after controlling for BMI.…”

Relatively low serum leptin levels in adults born with intra-uterine growth retardation

“…Prolonged hyperinsulinemia is known to increase circulating leptin levels. 8,9,20 In rodents, both in vivo and in vitro studies have demonstrated that leptin increases peripheral glucose uptake and improves glucose metabolism in skeletal muscles. 10 ± 12 Therefore, according to the results obtained in animal models, we cannot exclude the theory that increased leptin production could be a regulatory component aimed at improving, at least in part, insulin-sensitivity.…”

Is there a relationship between leptin and insulin sensitivity independent of obesity?A population-based study in the Indian Ocean nation of Mauritius

“…Both fasting insulin and insulin sensitivity (hyperinsulinaemic, euglycaemic clamp) were correlated with leptin independently of BMI in middle-aged Finnish men, but no attempt was made to assess which was more important. 42 In subjects with Type 2 diabetes mellitus, the association between insulin concentration and resistance is not as close, and in two studies making use of this phenomenon, leptin was found to be more closely correlated with insulin concentration than with insulin resistance. These inconsistent results indicate the need to standardize the approach to investigations into leptin, insulin and obesity.…”