Plasma adiponectin is modestly decreased during 24‐hour insulin infusion but not after inhibition of lipolysis by Acipimox

Abstract

Objective. Plasma adiponectin is associated with insulin resistance and atherosclerosis. Adiponectin expression in adipose tissue is up‐regulated by peroxisome proliferator‐activated receptor (PPAR)‐γ agonist treatment and its plasma level may be affected by insulin. We tested the hypothesis that prolonged exogenous insulin infusion decreases plasma adiponectin, and examined whether a possible effect of insulin on plasma adiponectin is attributable to inhibition of lipolysis. Material and methods. The effect of insulin infusion on plasma adiponectin (Linco enzyme‐linked immunosorbent assay) was evaluated during a 24‐h moderately hyperinsulinemic clamp (8.3 µU kg−1 s−1) in 8 male type 2 diabetic patients and in 8 healthy men. On a separate day, acipimox (250 mg/4 h for 24 h) was administered to inhibit lipolysis. Insulin and acipimox were administered in random order with 1 week between study days. Results. In type 2 diabetic patients, insulin infusion decreased plasma adiponectin from 7.74±2.53 mg/l to 6.76±2.41 mg/l after 24 h (p<0.05). In healthy subjects, the change in plasma adiponectin after 24 h of insulin was not significant (8.10±2.76 and 7.55±2.41 mg/l at baseline and after 24 h of insulin, respectively). The change in plasma adiponectin after 24 h insulin in healthy subjects was not different from the change in diabetic patients. Plasma adiponectin did not decrease after 24 h acipimox administration in either group (type 2 diabetic patients: 6.84±2.19 and 6.54±2.93 mg/l at baseline and after 24 h, respectively (NS); healthy subjects; 7.35±2.52 and 8.31±3.37 mg/l, at baseline and after 24 h, respectively (NS)). When the results from diabetic and healthy subjects were combined, the decrease in plasma adiponectin after 24 h of insulin infusion (−0.76±1.08 mg/l, equivalent to a −9% change from baseline, p<0.05) was different (p = 0.05) from the change after 24 h acipimox (+0.33±1.74 mg/l, equivalent to a +4% change from baseline). Plasma free fatty acids decreased during insulin infusion (p<0.01 for both groups after 24 h) as well as in response to acipimox (p<0.05 for healthy subjects; p<0.01 type 2 diabetic patients after 24 h). After administration of acipimox, plasma insulin did not change in either group. Conclusions. Plasma adiponectin is modestly decreased during 24 h of insulin infusion. It is unlikely that this response to exogenous insulin is attributable to inhibition of lipolysis, since plasma adiponectin did not decrease after acipimox.