Adiponectin and leptin are adipokines that are mainly produced in adipocytes and exert various functions. Adiponectin decreases atherosclerosis, oxidative stress, angiogenesis, inflammation, and apoptosis, whereas leptin works oppositely. Angiotensin type-1 receptor (AT1R) blockers (ARBs) are widely used as antihypertensive drugs. Some ARBs are known to activate peroxisome proliferator-activated receptor (PPAR) γ, which is a key regulator of fatty acid metabolism. It is reported that adiponectin secretion increases by pioglitazone, a full agonist of PPARγ, and some ARBs via PPAR γ activation. However, the effects of ARBs on leptin secretion are controversial. The present study aimed to examine the effects of ARBs on the expression and secretion of adiponectin and leptin in human white adipocytes.
Human white preadipocytes (Promo Cell) were differentiated into mature adipocytes in the medium containing insulin, dexamethasone, thyroxin and isobutylmethylxanthine. Pioglitazone and ARBs including telmisartan, irbesartan, azilsartan, candesartan, losartan, olmesartan and valsartan (1µM) were administered in the culture medium on day 4 and 8. The medium was collected on day 12 and the concentrations of adiponectin and leptin were measured by enzyme immunoassay. Real time PCR was performed to quantitate the mRNA expression of adiponectin and leptin in adipocytes. The experiments were performed in quadruplicate.
Pioglitazone significantly increased adiponectin secretion (386.7 ± 133.7 vs. 7.3 ± 1.9 ng/ml in control) from human adipocytes. Among ARBs, adiponectin secretion significantly increased by telmisartan (136.7 ± 16.3 ng/ml) and irbesartan (69.7 ± 23.1 ng/ml), while the other 5 ARBs did not have any influence on adiponectin secretion. Real-time PCR also showed that mRNA expression increased 5.1-fold, 3.8-fold and 1.5-fold by pioglitazone, telmisartan and irbesartan, respectively. Leptin secretion significantly decreased by pioglitazone (27.7 ± 5.0 vs. 82.5 ± 3.8 ng/ml in control). Among ARBs, only telmisartan (38.7 ± 4.2 ng/ml) decreased leptin secretion. Real-time PCR also showed that mRNA expression decreased to be 0.5-fold and 0.7-fold by pioglitazone and telmisartan, respectively. GW9662, a selective antagonist of PPARγ, potently blocked pioglitazone-induced changes of adiponectin and leptin expression and secretion. On the other hand, GW9662 did not reverse telmisartan and irbesartan induced changes.