New study results say that patients with type 2 diabetes (T2DM) may not have impaired secretion of glucagon-like peptide-1 (GLP-1). A meta-analysis of several trials revealed that patients with type 2 diabetes had similar levels of GLP-1 secretion as controls after an oral glucose tolerance test (OGTT) or a mixed meal, Filip Knop, MD, PhD, of Gentofte Hospital at the University of Copenhagen, and colleagues reported online in Diabetologia.

The study included 275 patients with T2DM and 279 controls, from 22 trials published between 1996 and 2012. They found that both groups of patients had similar secretion of total GLP-1 as evaluated from peak plasma concentrations (weighted mean difference 1.09 pmol/L, not significant). A fixed-effects meta-analysis actually revealed higher peak plasma GLP-1 concentrations in patients with type 2 diabetes compared with controls (weighted mean difference, 1.79 pmol/L). Also, a subgroup analysis showed that type 2 diabetics had increased GLP-1 responses after a liquid mixed meal test and after a 50-g OGTT.

But type 2 diabetics did have reduced GLP-1 responses compared with controls after a solid mixed meal test. The researchers said the difference between solid and liquid meals could have something to do with variations in the absorption of nutrients among type 2 diabetes patients.