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

Objective. Plasma adiponectin is associated with insulin resistance and atherosclerosis. Adiponectin expression in adipose tissue is up-regulated by peroxisome proliferator-activated receptor (PPAR)-gamma 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 mu U 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.