The role of the body mass index and triglyceride levels in identifying insulin-sensitive and insulin-resistant variants in Japanese non-insulin-dependent diabetic patients

Using the minimal model approach shown by Bergman, our group had previously shown 2 variants among non-obese mildly diabetic patients, one with normal insulin sensitivity and the other with insulin resistance, The present stu dy examines whether these 2 variants exist in the ordinary Japanese non-ins ulin-dependent diabetes mellitus (NIDDM) population and compares the clinic al profile between the 2 discrete forms of NIDDM. In addition, we investiga ted the factors responsible for insulin resistance observed in Japanese NID DM populations. One hundred eleven untreated Japanese NIDDM subjects (fasti ng glucose < 10 mmol/L) were assessed for insulin action (homeostasis model assessment [HOMA-IR] = fasting serum insulin (mu U/mL) x fasting plasma gl ucose (mmol/L)/22.5) and the fasting lipid profile. Sixty percent of these patients had normal insulin sensitivity (HOMA-IR < 2.5). The insulin-resist ant patients had higher serum cholesterol (188.1 +/- 5.2 v 182.2 +/- 3.9 mg /dL, P > .05) and low density lipoprotein (LDL) cholesterol (501.2 +/- 16.7 v 469.4 +/- 14.8 mg/dL, P > .05) than the insulin-sensitive patients, but the difference was not statistically significant, In contrast, the former g roup had a significantly higher body mass index ([BMI] 26.6 +/- 0.8 v 21.7 +/- 0.4 kg/m(2), P < .0001) and higher serum triglycerides (181.0 +/- 16.4 (range, 79 to 545) v 95.1 +/- 4.1 (range, 36 to 204) mg/dL, P < .0001) and lower high-density lipoprotein (HDL) cholesterol (47.2 +/- 1.7 v 58.2 +/- 2 .5 mg/dL, P < .005) than the latter group. HOMA-IR was related to the BMI. Fifteen of 17 (88%) NIDDM patients with a BMI greater than 27.0 were insuli n-resistant, whereas 35 of 38 (92%) NIDDM patients with a BMI less than 21. 5 were insulin-sensitive. In the midrange BMI (21.5 to 27.0 kg/m2), patient s were equally likely to be insulin-resistant or insulin-sensitive. Analysi s of the midrange BMI group showed that HOMA-IR was associated with serum t riglycerides (P < .0001) but not with the BMI. These data suggest the follo wing conclusions: (1) Japanese NIDDM patients can be classified into 2 popu lations, one with normal insulin sensitivity and the other with insulin res istance; (2) NIDDM patients with normal insulin action have a low cardiovas cular disease risk factor, whereas those with insulin resistance have a mar kedly increased cardiovascular disease risk factor; and (3) the BMI and ser um triglyceride level per se are associated with insulin action in Japanese NIDDM populations. Copyright (C) 2000 by W.B. Saunders Company.