Cystatin C is Associated with Serum Uric Acid in a Hypertensive Population

Abstract

Hyperuricemia has been related with the development of arterial hypertension Cystatin C, a marker of renal function has been proposed recently as a marker of cardiovascular risk, independently of renal function. We investigate if serum uric acid is related with serum cystatin C in patients with essential hypertension. We included 885 patients (50.7% males), aged 57,8 +/- 14,9 y., diagnosed of essential hypertension and attended in our Hypertension Unit during a 12 month. We performed in all of them a clinical history, a physical examination and routine analysis, including cystatin C (Nephelometry, Behring). Hyperuricemia was defined as serum uric acid > 7 mg/dl (males) or >6 mg/dl (females) or being on treatment with allopurinol. The result was that 272 patients had hyperuricemia (30,7%) with male predominance (36.1%) vs. females (25.5%), [p < 0.0001]. Serum cystatin C did not shown gender differences (males 0.87 +/- 0.269 mg/L and females (0.90 +/- 0.47 mg/L), [p: 0.061]. After adjusting for age, gender, estimated glomerular filtration rate (e-GFR) and diuretic (38.2%) and allopurinol treatment (8.1%), serum uric acid showed a positive correlation with abdominal circumference(r:0.277, p< 0,0001), triglycerides(r:0.195, p < 0.0001), body mass index (r:0,274, p< 0.0001), total cholesterol (r:0.136, p =0.009, LDL-cholesterol (r:0.104; p= 0.049), microalbuminuria (r:0.163, p =0.002), serum ferritin (r.0.108, p= 0.041) and cystatin C (r:0.302, p < 0.0001). Others partial correlations analysed (HDL-cholesterol, glucose, CRP, fibrinogen and systolic and diastolic blood pressure) did not shown significant differences. Multivariate analysis, adjusted for age, gender, MDRD-GFR, and diuretic and allopurinol treatment, showed that triglycerides (B = 0.004, IC 95%:0.002–0.005; p< 0.0001), BMI (B = 0.038, IC 95%: 0.012–0.065; p = 0.005), abdominal circumference (B = 0.013, IC 95%: 0.002–0.25; p = 0.023 and cystatin C (B= 0.875, IC 95%: 0.509–1.241; p < 0.0001) as independent determinants of uric acid levels (model R2= 0.36). In conclusion, in our hypertensive patients serum cystatin C was the main independent predictor of serum uric acid levels. This association, independent of renal function and diuretic and allopurinol treatment, support the relationship of both parameters as cardiovascular risk factors in hypertensive patients.