Validation of a simple index (SIisOGTT) of insulin sensitivity in a population of sedentary men.
AIM
The ongoing obesity epidemic is associated with numerous health problems related to altered metabolic function. Among these is type 2 diabetes, characterized by lowered insulin sensitivity (IS). Consequently, the development of simple indices to assess IS has research and clinical importance. The SI(is)OGTT, a new index of IS, was recently described by Bastard et al. (Diabetes & Metabolism 2007;33:261-8), and validated in sedentary, non-diabetic, overweight and obese postmenopausal women. The aim of the present study was to validate the index in men.


METHODS
The data used in this project came from sedentary men (n=36), aged 34-53 years, all of whom underwent a hyperinsulinaemic-euglycaemic clamp and 2-hour oral glucose tolerance test (OGTT). Correlations with M/I (glucose infusion rate [GIR] divided by insulin concentration), GIR and GIR divided by fat-free mass (FFM) were obtained by four well-known indices (HOMA, QUICKI, Cederholm and Matsuda) as well as with the new SI(is)OGTT index. Pearson correlations and Bland-Altman analyses were obtained for every index versus clamp value.


RESULTS
The best correlate of IS in the present study was the SI(is)OGTT (r=0.84, P<0.0001). The agreement of this method with the hyperinsulinaemic-euglycaemic clamp, as assessed by Bland-Altman plots, was similar to those of the other indices and to those previously described in postmenopausal women.


CONCLUSION
The new index proposed by Bastard et al. is as good a predictor of IS in sedentary men as the other commonly used indices, and appears to be as reliable in this population as it was in the original study of postmenopausal women.