Researchers from Paris, France have found that in obese patients who had either laparoscopic gastric bypass, sleeve gastrectomy, or adjustable gastric banding, weight loss was associated with decreases in serum uric acid (SUA) levels and in xanthine oxidase (XOD) activity, and that decreases in SUA likely being mediated by reduced triglyceride levels.1
“Surprisingly, we lack information on the effect of weight loss on XOD activity, which catalyzes the conversion of hypoxanthine to xanthine and then xanthine to uric acid,” wrote Pascal Richette, PhD, from Paris Diderot University, Assistance Publique-Hôpitaux de Paris, and Hôpital Lariboisière in Paris, France and colleagues.
To investigate whether changes in XOD activity, adipokines, dyslipedemia, insulin resistance, and low-grade inflammation caused by substantial weight loss could explain decreased uricemia following weight loss, the researchers conduced a prospective lontigudinal study of obese patients who underwent bariatric surgery.
Data was collected from 154 obese patients without gout (81% women, mean age 41.0 ± 12.3 years, mean body mass index [BMI] 47.8 ± 7.2 kg/m2), who were recruited from the Department of Nutrition at at Pitié-Salpêtrière University Hospital, in Paris, France.
Biologic samples and clinical data were collected in patients before surgery and 6 months after surgery, including SUA, XOD activity, lipid profile, insulin sensitivity, body composition, and immunoassay levels of adipokines and inflammatory markers.
The researchers found that the greatest decreases of SUA levels were in those with hyperuricemia. In these patients, circulating XOD activity decreased with weight loss. Reductions in SUA levels were associated with decreased triglyceride levels and with BMI, but not with XOD activity, adipokine levels (leptin or adiponectin), inflammatory variables, or surrogates of insulin resistance.
Decreases in BMI and triglycerides were found to be the strongest predictors of SUA changes following bariatric surgery after multivariate regression analysis .
“Although weight loss was associated with a decrease in both SUA levels and XOD activity, reduced SUA levels might be mediated not by decreased XOD activity nor by improved insulin resistance but rather by decreased triglyceride levels,” the authors wrote.
The precise mechanisms behind how triglycerides might affect the renal handling of uric acid remain unknown.
Summary & Clinical Applicability
In obese patients who lost weight due to bariatric surgery, SUA levels and XOD activity were significantly reduced. The findings from this research suggest that the reduced SUA levels were not mediated by decreased XOD activity nor by improved insulin resistance, but may be mediated by decreased triglyceride levels.
Limitations & Disclosures
- Observational study design does not allow causality conclusion to be made between the change in SUA levels and the change in triglyceride levels.
- Urinary fractional excretion of uric acid was not assessed, so the researchers could not determine whether weight loss was associated with an increase in renal excretion of uric acid.
- Following the patients’ weight loss, the impact of change in medications was not assessed, which may have affected their metabolic profiles.
- Richette P, Poitou C, Manivet P, et al. Weight Loss, Xanthine Oxidase, and Serum Urate Levels: A Prospective Longitudinal Study of Obese Patients. Arthritis Care Res. 2016;68(7):1036-1042. doi:10.1002/acr.22798.