Role of the Gut in the Temporal Changes of β-Cell Function After Gastric Bypass in Individuals With and Without Diabetes Remission

Objective: The role of the gut in diabetes remission after Roux-en-Y gastric bypass (RYGB) is incompletely understood. We assessed the temporal change in insulin secretory capacity after RYGB, using oral and intravenous (IV) glucose, in individuals with type 2 diabetes.

Research Design And Methods: Longitudinal, prospective measures of β-cell function were assessed after oral glucose intake and graded glucose infusion in individuals with severe obesity and diabetes studied at 0, 3 (n = 29), 12 (n = 24), and 24 (n = 20) months after RYGB. Data were collected between 2015 and 2019 in an academic clinical research center.

Results: The decreases in body weight, fat mass, waist circumference, and insulin resistance after surgery (all P < 0.001 at 12 and 24 months) did not differ according to diabetes remission status. In contrast, both the magnitude and temporal changes in β-cell glucose sensitivity after oral glucose intake differed by remission status (P = 0.04): greater (6.5-fold; P < 0.01) and sustained in those in full remission, moderate and not sustained past 12 months in those with partial remission (3.3-fold; P < 0.001), and minimal in those not experiencing remission (2.7-fold; P = not significant). The improvement in β-cell function after IV glucose administration was not apparent until 12 months, significant only in those in full remission, and only ∼33% of that observed after oral glucose intake. Preintervention β-cell function and its change after surgery predicted remission; weight loss and insulin sensitivity did not.

Conclusions: Our data show the time course of changes in β-cell function after RYGB. The improvement in β-cell function after RYGB, but not changes in weight loss or insulin sensitivity, drives diabetes remission.