Effects of Roux-en-Y gastric bypass and sleeve gastrectomy on β-cell function at one year after surgery: a systematic review

Bariatric surgery is a highly effective obesity treatment resulting in substantial weight loss and improved glucose metabolism. We hereby aimed to summarize available evidence of the effect of the two most common bariatric surgery procedures, Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), on dynamic measures of β-cell function (BCF). A systematic search of the literature was conducted in 3 bibliographic databases for studies reporting effects of RYGB and/or SG on BCF assessed using dynamic metabolic perturbation (oral or intravenous bolus stimulation), performed before and 1 year (± 3 months) after surgery. Twenty-seven unique studies (6 randomized controlled trials and 21 observational studies), involving a total of 1,856 obese adults were included for final analysis. 25 and 9 studies report effects of RYGB and SG on BCF respectively (7 studies compared the two procedures). 7 studies report results according to pre-surgical diabetic status. Owing to variable testing procedures and BCF indices reported, no meta-analysis was feasible, and data were summarized qualitatively. For both surgical procedures, most studies suggest an increase in BCF and disposition index, particularly when using oral stimulation, with a more pronounced increase in diabetic than non-diabetic individuals. Additionally, limited indications for greater effects after RYGB and SG was found. The quality of the included studies was in general satisfactory. The considerable heterogeneity of test protocols and outcome measures underscores the need for a harmonization of BCF testing in future research.