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.


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 microU 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.
Dullaart
R P F
RP
Department of Endocrinology, Groningen University Medical Center, The Netherlands. r.p.f.dullaart@int.azg.nl
Riemens
S C
SC
Meinardi
J R
JR
Wolffenbuttel
B H R
BH
Sluiter
W J
WJ
D052242:Adiponectin; D000328:Adult; D000368:Aged; D003864:Depression, Chemical; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D015309:Glucose Clamp Technique; D006207:Half-Life; D006801:Humans; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood*; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D011719:Pyrazines / Q000494:pharmacology*; D013997:Time Factors
D052242:Adiponectin; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D011719:Pyrazines; C027696:acipimox