Uric acid: a surrogate of insulin resistance in older women

OBJECTIVES: The relationship between serum uric acid (UA) and cardiovascular disease has been debated extensively and no conclusion has been reached yet. The main purpose of this study was to explore the sex-different relationship among insulin resistance, metabolic syndrome (MS) and hyperuricemia. METHODS: A community-based prospective study was conducted among people aged over 40 years in I-Lan County, Taiwan. A complete history taking, physical examination and laboratory tests were performed for each subject by the well-trained research staff. Insulin resistance was determined by the homeostasis model assessment (HOMA-IR). Serial comparisons were performed to evaluate the associations between MS, insulin resistance and hyperuricemia in both sexes. RESULTS: A total of 852 subjects (mean age=64.6+/-11.3 years, 56.7% female) were enrolled. The prevalence of obesity, hyperuricemia, chronic kidney disease (CKD), insulin resistance and MS was 42.2, 31.2, 30.9, 36.0 and 47.5%, respectively. Subjects with MS were significantly older (63.4+/-10.0 years versus 60.4+/-12.4 years, P=0.019), higher in body mass index (BMI) (26.3+/-3.5 kg/m(2) versus 23.6+/-3.0 kg/m(2), P<0.001), serum UA (6.1+/-2.1mg/dl versus 5.5+/-1.7 mg/dl, P=0.003), HOMA-IR (2.7+/-3.4 versus 1.0+/-0.8, P<0.001) and lower in glomerular filtration rate (GFR) (66.3+/-17.7 ml/min/1.73 m(2) versus 72.0+/-15.2 ml/min/1.73 m(2), P=0.001). Male gender, CKD, BMI>23 kg/m(2) and insulin resistance were all independent risk factor for hyperuricemia with the covariate of age. When age and BMI were controlled, females had significantly higher prevalence of CKD and insulin resistance, but less hyperuricemia than males (P all<0.05). Adjusted for age, BMI and GFR, hyperuricemia and MS were both independent risk factors for insulin resistance in females (P=0.006, <0.001, respectively). In males, MS remained significantly associated with insulin resistance (P=0.002) but not hyperuricemia (P=0.813). When age, BMI and GFR were controlled, serum UA was positively related to HOMA-IR in females (gamma=0.117, P=0.012), but not in males (P=0.93). CONCLUSION: A positive association was identified between serum UA and insulin resistance in older women but not in men. Studies related to insulin resistance may be needed when hyperuricemia was identified in older women.