<i>Objective</i>: The role
of the gut in diabetes remission after gastric bypass (RYGB) is incompletely
understood. We therefore assessed the temporal change in insulin secretory
capacity after RYGB, using oral and intravenous
(IV) glucose, in individuals with type 2 diabetes.
<p><i>Research
Design and Methods:</i> Longitudinal, prospective measures of β-cell
function after oral glucose and IV 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.</p>
<p><i>Results</i>: 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 differed by remission status (p=0.04): greater
(6.5 fold, p<0.01) and sustained in full remitters, moderate and not
sustained past 12 months in partial remitters (3.3 fold, p<0.001), minimal
in non-remitters (2.7 fold, p=ns). The
improvement in β-cell function after IV glucose was not apparent until 12
months, significant only in full remitters, and only ~1/3 of that observed after
oral glucose.</p>
<p>Pre-intervention
β-cell function and its change after surgery predicted remission; weight loss and
insulin sensitivity did not. </p>
<p><i>Conclusion</i>: 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.</p>
Gastric bypass and banding equally improve insulin sensitivity and β cell function
