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

OBJECTIVE

It has been shown previously in smaller studies that fasting serum leptin and insulin concentrations are highly correlated, and insulin sensitive men have lower leptin levels than insulin resistant men matched for fat mass. We have examined the association between insulin resistance (assessed by fasting insulin) and leptin after controlling for overall and central adiposity in a population-based cohort.

DESIGN

Leptin levels were compared across insulin resistance quartiles within three categories of obesity (tertiles of body mass index (BMI)). Partial correlation coefficents and multiple linear regression models were used to assess the relationship between leptin and fasting insulin after adjusting for BMI and waist to hip ratio (WHR) or waist circumference.

SUBJECTS

Subjects were normoglycemic participants of a 1987 non-communicable diseases survey conducted in the multiethnic population of Mauritius. 1227 men and 1310 women of Asian Indian, Creole and Chinese ethnicity had normal glucose tolerance and fasting serum leptin measurements.

RESULTS

Mean serum leptin concentration increased across quartiles of fasting insulin in each BMI group and gender, after controlling for BMI, WHR and age. Furthermore, fasting insulin was a significant determinant of serum leptin concentration, independent of BMI and WHR, in both men and women. Similar results were found if waist circumference replaced BMI and WHR in the model.

CONCLUSION

These results suggest that insulin resistance/concentration may contribute to the relatively wide variation in leptin levels seen at similar levels of body mass or alternatively, leptin may play a role in the etiology of insulin resistance. Further studies will be important to determine whether the hyperleptinemia/insulin resistance relationship has a role in the natural history of obesity, Type 2 diabetes mellitus and the other metabolic abnormalities associated with insulin resistance.