Insulin resistance in obesity and noninsulin dependent diabetes mellitus.

Insulin clamp studies were carried out on 13 non-diabetics and 12 non-insulin-dependent diabetics (NIDDM). Based upon the body mass index (BMI), they were further divided into obese (BMI greater than or equal to 27 kg/m2) and nonbese groups (BMI less than 27 kg/m2). All received euglycemic insulin clamp study (Humulin-S 40mU/m2/min). Thermoregulated venous samplings were done every five minutes for measurements of plasma glucose (PG) and immunoreactive insulin (IRI). Steady state plasma glucose (SSPG) was obtained 20-80 minutes and kept for 100 more minutes. The data of final 40 minutes of clamp were used for analysis. Variations in SSPG and metabolic clearance rate of glucose (MCRG) instead of glucose infusion rate (M) value were used to assess the insulin sensitivity. The results showed that insulin resistance was noted in obese non-diabetic and diabetic subjects as well as in non-obese diabetic patients, as evidenced by higher basal IRI and lower MCRG than non-obese normal controls. Correlation analysis revealed that there was no correlation between the reduction of MCRG and the BMI in either non-diabetic or diabetic patients. There was a strong negative correlation between MCRG and the ambient fasting plasma glucose in the diabetic group, whereas this correlation was not found in the non-diabetic group. In conclusion, obesity with or without diabetes did have remarkable insulin resistance. In non-diabetic obese subjects the insulin resistance did not go up as the BMI increased further. In diabetic patients, both obesity and hyperglycemia contributed significantly insulin resistance.