Low levels of adiponectin in plasma have recently been implicated in the development of obesity, insulin resistance, and type 2 diabetes in mice and humans (14). We examined a role of adiponectin as a clinical examination in obesity and type 2 diabetes and raise a question of clinical worth of evaluating adiponectin levels in the management of type 2 diabetic patients.

In the first group, 39 Japanese subjects with type 2 diabetes, including 19 men and 20 women matched for age, HbA1c, and plasma glucose levels, were assessed in a cross-sectional analysis. Plasma adiponectin levels were determined in type 2 diabetic subjects with normal BMI (21.6 ± 0.3 kg/m2, n = 22 [11 men and 11 women], 63 ± 1 years) and those who were overweight (26.3 ± 0.3 kg/m2, n = 17 [8 men and 9 women], 64 ± 2 years). These subjects were treated by diet therapy alone before assessment. No significant differences in plasma adiponectin levels were observed in type 2 diabetic subjects who were nonobese (adiponectin 5.9 ± 0.4 μg/ml) and overweight (6.2 ± 0.5 μg/ml). These results indicate that plasma adiponectin levels are not an indicator of mild obesity in type 2 diabetic patients.

In the second group, a total of 14 Japanese type 2 diabetic subjects who were treated with antidiabetic agents without pioglitazone were evaluated prospectively. Of the 14, 8 subjects (4 men and 4 women, 62 ± 2 years) displayed better glycemic control, whereas 6 subjects (5 men and 1 woman, 65 ± 1 years) displayed worse glycemic control during the management. Decreases in HbA1c and plasma glucose levels were not associated with elevations in plasma adiponectin levels (BMI 24.7 ± 1.1 to 25.0 ± 1.1 kg/m2, HbA1c 8.6 ± 0.2 to 7.1 ± 0.2% [P < 0.05], glucose 187 ± 17 to 128 ± 14 mg/ml [P < 0.05], and adiponectin 5.2 ± 0.9 to 5.1 ± 0.8 μg/ml). In addition, elevations in HbA1c were not associated with decreases in plasma adiponectin levels. Rather, we observed that the elevations in HbA1c levels were associated with elevations in adiponectin levels (BMI 23.0 ± 0.8 to 23.2 ± 0.6 kg/m2, HbA1c 7.6 ± 0.2 to 8.0 ± 0.1% [P < 0.05], glucose 176 ± 17 to 175 ± 32 mg/ml, and adiponectin 5.5 ± 1.4 to 7.2 ± 1.0 μg/ml [P < 0.05]). These findings indicate that adiponectin levels are not directly related to glycemic control in type 2 diabetic patients.

Moreover, in the third group of randomized subjects with type 2 diabetes (n = 9 [5 men and 4 women], age 56 ± 2 years) without any antidiabetic drugs, fasting plasma adiponectin levels were not negatively correlated with BMI, HbA1c, fasting plasma glucose and insulin levels, or 2-h glucose levels after 75-g glucose ingestion, whereas plasma leptin levels were positively correlated with BMI (r = 0.598, P < 0.01).

These findings indicate that plasma adiponectin levels are unlikely to be a clinical indicator of mild obesity and glycemic control in Japanese type 2 diabetic patients. The clinical worth of adiponectin levels in the management of type 2 diabetes warrants further examination in the future.

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