Background: Type 2 diabetes mellitus (T2DM) and obesity share a common pathogenesis involving an insulin resistance, and adiponectin, a factor specific to adipose tissue, plays an important role in a glucose metabolism and an insulin resistance. The adiponectin level is reduced not only in patients with obesity and T2DM, but also in patients with coronary artery disease. Thus, the aim of this study is to investigate and characterize the insulin resistance and to evaluate the relationship between adiponectin level and visceral and skeletal muscle fat areas among obese, T2DM patients and non diabetic obese patients.
Methods: The anthropmetric parameters, biochemical profiles, clinical characteristics and serum adiponectin concentrations of 16 obese type 2 diabetic subjects (BMI 225 kg/㎡) and 12 obese non diabetic subjects were measured. And, abdominal adipose tissue areas and mid-thigh skeletal muscle areas were measured by computed tomography (CT). The HOMA-IR and HOMA-β scores were calculated to assess the insulin sensitivity and insulin secretory function. We analysed the relationship between serum adiponectin level with body fat distribution, anthropometric parameters, biochemical profiles, and clinical characteristics.
Results: There were no differences in age, height, weight, BMI, body fat, waist circumference, and blood pressure between T2DM obesity group and non diabetic obesity group, where as total cholesterol, LDL-cholesterol, triglyceride and free fatty acid levels were significantly higher in T2DM obesity group. However, the abdominal subcutaneous fat area, visceral fat area, VSR were higher in non diabetic obesity group, while mid-thigh low density muscle areas were greater in T2DM group. Moreover, no significant difference was noted in HOMA-IR between the two groups, but C-peptide, serum adiponectin concentration, and HOMA-β were lower in T2DM obesity group. The age, weight, height, BMI, systolic blood pressure, HbA_(IC), HOMA- IR, visceral fat area, and low density muscle area were in negative correlations with the serum adiponectin concentration. Also, in the multiple regression analysis, age, HbA_(IC), HOMA-IR, visceral fat area and low density muscle area were found to correlate well with the serum adiponectin concentration.
Conclusion: This study demonstrates that in the setting of similar insulin resistance levels, the abdominal visceral fat area is significantly higher in non diabetic obesity group, and the low density muscle area is higher in diabetic obesity group. This implies that in addition to various genetic and environmental factors that affect insulin resistance, adipocytokine concentration, such as adiponectinin, has a significant role in glucose metabolism and insulin resistance. Moreover, the present study suggests that aforementioned characteristics of insulin resistance and adipocytokines may lead to somewhat different clinical manifestations and complications such as atherosclerosis in the diabetic and obese patients.

Keywords: Adiponectin, type 2 diabtes mellitus, Obesity, Visceral fat, Subcutaneous fat, Insulin resistance