Incretin Effect Independent of Glycemia Level

The enhanced insulin secretion after meals mediated by two intestinal hormones, known as the incretin effect, is independent of glycemia in healthy individuals, according to a study.

To examine the role of plasma glycemia on the incretin effect, Marzieh Salehi, M.D., from the University of Cincinnati, and colleagues gave 13 healthy subjects without diabetes 50 g of an oral glucose solution mixed with D-xylose at two levels of fixed plasma hyperglycemia: 8 mmol/L and 10.5 mmol/L. The experiment was performed twice at the low glycemia level and once at the high level.

The researchers found that the relative increase in insulin secretion was similar at both glycemia levels. The response of the intestinal hormone glucagon-like peptide-1 (GLP-1) was significantly lower at higher plasma glycemia, while the response of glucose-dependent insulinotropic polypeptide was similar in all studies. The incretin effect was found to be reproducible.

"These findings indicate that the incretin contribution to postprandial insulin release is independent of glycemia in healthy individuals, despite differences in GLP-1 secretion," Salehi and colleagues conclude. "These findings suggest that in healthy humans, control of the magnitude of the incretin effect is complex and occurs primarily at the level of the gastrointestinal tract."

Diabetes, June 25, 2012