GLP-1 Help to Control Diabetes after Gastric Bypass

There is a positive association between glucagon-like peptide-1 (GLP-1) concentrations and insulin concentrations following gastric bypass (GBP) surgery in patients with type 2 diabetes, suggesting a role for GLP-1 in glucose control, according to a published study.

The object of the study was to characterize the magnitude and variance of the change of glucose and glucagon-like peptide-1 (GLP-1) concentrations, and to identify determinants of glucose control up to 2 years after gastric bypass (GBP).

Bart J. Van Der Schueren, Ph.D., of St. Luke's Roosevelt Hospital Center in New York City, and colleagues studied 15 obese patients with type 2 diabetes (one man, 14 women) before GBP surgery and one, 12, and 24 months following surgery. Glucose and GLP-1 concentrations were measured during an oral glucose challenge.

The researchers found that weight, glucose area under the curve from 0 to 180 min (AUC_0-180), insulin sensitivity index, and the homeostasis model assessment of insulin resistance all decreased significantly up to one year following GBP, but did not decrease any further at the two-year marker. The decrease in insulin AUC_0-180 became significant at the two-year point. GLP-1 AUC_0-180 was positively associated with insulin AUC_0-180. Glucose AUC_0-180 started decreasing in magnitude one month after surgery, while the GLP-1 AUC_0-180 increased in magnitude one month after GBP, but did not achieve increased variance until the one-year follow-up point.

From the results it was concluded that, the increase in variance of GLP-1 at 1 and 2 years after GBP suggests mechanisms other than proximal gut bypass to explain the enhancement of GLP-1 secretion. The association between GLP-1 and insulin concentrations supports the idea that the incretins are involved in glucose control after GBP.

The enhanced glucagon-like peptide-1 (GLP-1) levels and incretin effect on insulin secretion, with weight loss, explain improved diabetes control after gastric bypass (GBP) surgery. However, the long-term clinical outcome after GBP differs greatly between patients, with diabetes relapse in up to 30%. This study aimed to assess the changes in magnitude and variance of GLP-1 and glucose concentrations in response to an oral glucose challenge (OGTT) in patients with type 2 diabetes and to identify determinants of glucose control up to 2 years after GBP.

Diabetes Care January 2012 vol. 35 no. 1 42-46