Background/Purpose: Weight loss leads to reduced serum urate (SU) in people with obesity. However, the clinical relevance of such reductions in SU are unknown. This study examined the impact of non-surgical weight loss and bariatric surgery on SU targets in people with morbid obesity and diabetes.

Methods: This was a single-centre, prospective study of 60 people with type 2 diabetes and morbid obesity (body mass index ≥ 35kg/m²). Following six months of non-surgical weight loss, all participants had laparoscopic sleeve gastrectomy, with a further one year of follow-up. SU concentrations were measured at each visit throughout the study.

Results: Participants experienced mean (SD) weight loss of 5.5 (4.1) kg prior to surgery and 34.3 (11.1) kg following surgery. SU did not change following non-surgical weight loss (mean (SD) SU 6.4 (1.5) mg/dL at baseline and 6.4 (1.7) mg/dL at follow-up), but increased to 7.4 (2.5) mg/dL in the immediate post-operative period and reduced to 5.0 (1.3) mg/dL one year after surgery (p<0.05 for both compared to baseline) (Figure). Baseline SU, cessation of diuretics, female sex, and change in creatinine independently predicted change in SU at the final visit. In participants without gout, SU above saturation levels (>6.8 mg/dL) were present in 19/48 (40%) at baseline and 1/48 (2%) one year after surgery (p<0.0001). In participants with gout, SU above therapeutic target levels (>6.0 mg/dL) were present in 10/12 (83%) at baseline and 4/12 (33%) one year after surgery (p=0.031). At the final study visit, 8/12 (67%) participants with gout were on no urate-lowering therapy. SU concentrations were above therapeutic target in 8/8 of these participants at baseline and 3/8 at follow-up (p=0.004).

Conclusion: Clinically relevant reductions in SU occur following bariatric surgery in people with morbid obesity and diabetes. The reduction of serum urate concentrations to sub-saturation concentrations indicates that the risk of developing gout can be substantially reduced in most people following bariatric surgery. Furthermore, for those with gout, bariatric surgery allows achievement of therapeutic target serum urate concentrations and may enable cessation of urate-lowering therapy.

Figure: Changes in SU concentrations in the entire study group (n=60). A. Mean (95% CI) SU concentrations.  B. Percentage of participants with SU above saturation levels (>6.8mg/dL). C. Percentage of participants with SU above therapeutic treatment target levels (>6mg/dL).  *P<0.05, **P<0.01, ***P<0.001 compared with baseline (-6 months) values. Dashed line refers to day of surgery.