[The role of hyperinsulinemia on the renal mechanism of hyperuricemia in overweight patients with essential hypertension].

The aim of the present study was to investigate the role of insulin on the renal mechanism of hyperuricemia in overweight patients with essential hypertension. Thirty-four essential hypertensives(EHT), receiving a regular diet containing 120mEq of sodium, 75mEq of potassium and 2000 kilocalories daily, were divided into two groups of non-obese(NHT) and obese(OHT) EHT. NHT as categorized as a body mass index (BMI) less than, and OHT as a BMI equal to or more than, 25 kg/m2 in male patients and 24 kg/m2 in female patients. In the early morning after overnight fast, renal uric acid and sodium clearance were examined while the patients remained in a supine position. During the two-hour clearance period, mean arterial pressure(MAP), heart rate(HR), endogenous creatinine clearance(Ccr), immunoreactive insulin(IRI), serum uric acid(SUA), fractional excretion of uric acid(FEUA) and sodium(FENa) were measured. Although there were no significant differences in age, MAP, HR, Ccr, nor SUA between the two groups, a higher ratio of female to male patients was found in OHT than in NHT. On the other hand, higher SUA and IRI and lower FEUA and FENa were observed in OHT than in sex-and Ccr-matched NHT. SUA was negatively correlated with FEUA in all patients (r = -0.392, p less than 0.05) and in NHT (r = -0.553, p less than 0.05), unlike in OHT. A significant negative correlation between BMI and FEUA was revealed in all EHT (r = -0.441, p less than 0.01) and in OHT (r = -0.597, p less than 0.01) but not in NHT. FEUA was positively correlated with FENa in all EHT (r = 0.554, p less than 0.001) as well as in NHT (r = 0.548, p less than 0.05) and OHT (r = 0.507, p less than 0.05). Moreover, there was a significant negative correlation between IRI and FENa in all EHT (r = -0.361, P less than 0.05) and in OHT (r = -0.470, p less than 0.05). However, no significant relation was demonstrated between IRI and SUA or FEUA in NHT or OHT. From these results, it is concluded that an attenuated renal excretion of uric acid related to natriuretic ability may play an important role in hyperuricemia in EHT. However, the role of hyperinsulinemia, which contributes to the blunting of natriuresis, might be relatively small in the renal mechanism of hyperuricemia in EHT, particularly in OHT.