Weight Loss, Xanthine Oxidase, and Serum Urate Levels: A Prospective Longitudinal Study of Obese Patients.

The mechanisms by which weight loss decreases serum uric acid (SUA) levels are poorly known. We aimed to investigate the role played by xanthine oxidase (XOD), metabolic status, and low-grade inflammation in decreased SUA levels induced by weight loss in obese patients.

Data were from a series of consecutive patients with severe obesity involved in a bariatric surgery program. Measurements of body composition and biologic samples were obtained before surgery and 6 months after surgery.

Among the 154 patients (mean ± SD age 41.0 ± 12.3 years, body mass index [BMI] 47.8 ± 7.2 kg/m(2) , 81% female), the mean ± SD weight loss at 6 months was 31.3 ± 7.8 kg. Reduction in SUA levels was modest (-10%): 4.98 ± 1.21 mg/dl at 6 months versus 5.52 ± 1.33 mg/dl at baseline (P < 0.001). The decrease in SUA levels was greatest (-18%) in hyperuricemic patients (n = 48). In these patients, circulating XOD activity decreased with weight loss (P < 0.0001). Multiple linear regression analysis revealed decreased SUA levels associated with decreased triglyceride levels (P = 0.0001) and BMI (P = 0.02) but not XOD activity, adipokine levels (leptin and adiponectin), insulin resistance, or levels of inflammatory variables (interleukin 6, orosomucoid, fibrinogen, and high-sensitivity C-reactive protein).

In obese patients, weight loss was associated with a decrease in both SUA levels and XOD activity. Our findings suggest that reduced SUA levels are not mediated by decreased XOD activity or improved insulin resistance but could be partly due to a reduction in triglyceride levels.