Postprandial hypoglycaemia after Roux-en-Y gastric bypass in individuals with type 2 diabetes

Postprandial hypoglycaemia (PPHG) is a complication of Roux-en-Y gastric bypass (RYGB) surgery in normoglycaemic individuals. In type 2 diabetes, RYGB improves glucose metabolism, but whether this improvement is related to the later development of PPHG is not known. We investigated the presence and mechanisms of PPHG in individuals with type 2 diabetes undergoing RYGB.

A total of 35 obese individuals with type 2 diabetes underwent an OGTT before and 24 months after surgery. PPHG was defined as a plasma glucose level of ≤3.3 mmol/l when not taking glucose-lowering agents. Insulin sensitivity was assessed by oral glucose insulin sensitivity index and beta-cell function by mathematical modelling of the plasma glucose, insulin and C-peptide concentrations.

After surgery, PPHG occurred in 11 of 35 individuals who underwent RYGB. Before surgery, BMI was lower, glycaemic control less good and time of glucose peak earlier in the PPHG vs No PPHG group, and the duration of diabetes was shorter with PPHG (all p ≤ 0.05). In addition, insulin sensitivity was greater in the PPHG than No PPHG group (p = 0.03). After surgery, BMI and fasting glucose and insulin levels decreased similarly in the two groups; insulin secretion during the first hour of the OGTT increased more in the PPHG than No PPHG group (p = 0.04). Beta-cell glucose sensitivity increased more in individuals with PPHG than those without (p = 0.002). Over the same time interval, the glucagon-like peptide 1 (GLP-1) response was lower in individuals with PPHG before surgery (p = 0.05), and increased more after surgery. At 2 h after glucose ingestion in the OGTT, postsurgery plasma glucagon level was significantly lower in the PPHG than No PPHG group.

In morbidly obese individuals with type 2 diabetes, spontaneous PPHG may occur after bariatric surgery independently of a remission of diabetes. Before surgery, individuals had a shorter duration and were more insulin sensitive. Two years after surgery, these individuals developed greater beta-cell glucose sensitivity, and showed greater insulin and GLP-1 release early in the OGTT.