Table 1 shows the characteristics of the two study groups. Fasting adiponectin serum levels were significantly lower in diabetic subjects compared to controls (Table 1). However, differences did not reach significance when males and females in both diabetic 6.9 ± 3.5 vs. 8.4 ± 5.2 μg/ml, (P = 0.06) and control 9.1 ± 6.3 vs. 10.2 ± 5.4 μg/ml, (P = 0.16) groups where compared. Adiponectin did not correlate to BMI in diabetic group(r = −0.12, P = 0.24), but it correlated significantly negative in the control subjects (r = −0.38, P = 0.002).
Adiponectin concentrations correlated significantly negative with HOMA B in subjects with type 2 diabetes only (r = −0.21, P = 0.04), whereas no significant correlation to HOMA IR was found in subjects with type 2 diabetes (r = 0.08, P = 0.44) or controls (r = −0.16, P = 0.33). Serum adiponectin in diabetic subjects did not correlate significantly with systolic (r = −0.13, P = 0.20) and diastolic (r = −0.13, P = 0.20) blood pressure, this correlation remained non-significant after adjustment for BMI. In non-diabetic subjects, the systolic and diastolic blood pressures were not related to adiponectin concentrations.
Adiponectin levels correlated significantly negative to serum proinsulin in diabetic subjects (r = −0.22, P = 0.03), but not to insulin (r = −0.16, P = 0.12) or proinsulin/insulin ratio (r = −0.18, P = 0.06), whereas no correlation was seen between adiponectin and the insulin or proinsulin/insulin ratio in control subjects (r = 0.03, P = 0.83) and (r = −0.01, P = 0.53).
Also serum adiponectin levels correlated significantly positive with serum glucose in diabetic subjects (r = 0.22, P = 0.03), however no significance was found between adiponectin and serum glucose in control subjects (r = −0.1, P = 0.5).
Type 2 diabetic subjects treated by sulphonylurea, had almost the same levels of adiponectin (7.3 ± 4.6 μg/ml, n = 81) compared to those treated with diet alone, or metformin (7.6 ± 4.7 μg/ml, n = 23, P = 0.99). Adjusting for BMI (P = 0.87) did not changed the results. The subjects treated with sulphonylurea had, however, also lower BMI than the other group, (22.7 ± 4.9 versus 26.1 ± 5.9, P = 0.0017), but no differences in HOMA B (P = 0.28) or HOMA IR (P = 0.15) was found. Fasting serum leptin levels did not correlate with adiponectin levels neither in diabetic (r = 0.03, P = 0.73) nor in control (r = −0.01, P = 0.1) groups.
However, serum adiponectin level correlated significantly with serum ghrelin in diabetic subjects (r = 0.29, P = 0.003), but not in control subjects (r = 0.18, P = 0.14).