Reduced Incretin Effect Predicts Diabetes Appearance in a Cohort of Nondiabetic Subjects after Acute Beta-Cell Mass Reduction

In type 2 diabetes incretin effect (IE) is reduced but still contributes to 20-35% of insulin response to oral glucose. One reason is the impairment of GIP and GLP1 effects. The role of IE in nondiabetic people is still under debate. In this study we evaluated changes in GLP1 levels, differential β-cell responses and IE during oral vs intravenous stimuli in nondiabetic humans before and after pancreatoduodenectomy (PD). We enrolled 37 nondiabetic patients affected by periampullary nonmalignant neoplasms scheduled for PD. Subjects underwent a 2-h hyperglycemic clamp (HC), a 830 kcal mixed meal test (MMT), and an oral glucose tolerance test (OGTT) before and after PD. GLP1 secretion was calculated during MMT stimulation. β-cell glucose sensitivity (βCGS, pmol·min−1m−2·mM−1) was calculated as the ratio of insulin secretion and glucose increments during both HC and MMT. IE was calculated as the ratio of βCGS obtained during MMT and HC. Based on post-PD OGTT, we divided nondiabetic subjects into 3 groups according to glucose tolerance after PD: normal glucose tolerance (postNGT, n=11), impaired glucose tolerance (postIGT, n=15), or diabetes (postDM, n=11). Before surgery, postIGT subjects exhibited increased GLP1 secretion during MMT compared to the other 2 groups (GLP1 AUC: postIGT 12638±688 vs postNGT 6994±1773 vs postDM 6443±1687 pmol/L·min, P<0.05). Further, a similar βCGS was observed in the 3 groups following HC stimulation (postNGT 95.2±15.5 vs postIGT 64.3±8.72 vs postDM 73.8±11.8, P=0.2), while a scaled reduction in βCGS was observed in postIGT and post-DM following MMT (postNGT 206±50.0 vs postIGT 111±19.9 vs postDM 88.2±8.45, P<0.05). Accordingly, we observed a scaled reduction of IE in postIGT and postDM groups (postNGT 2.35±0.52 vs post-IGT 1.37±0.13 vs post-DM 0.86±0.18, P<0.05). Our data show that GLP1 secretion increases in people at risk of IGT, possibly to compensate reduced IE, which seems to predict DM appearance after β-cell mass reduction. Disclosure G.Di giuseppe: None. J.J.Holst: Advisory Panel; Novo Nordisk A/S, Eli Lilly and Company, Board Member; Bainan Biotech, Antag Therapeutics, Consultant; Alphasights, Eli Lilly and Company, ShouTi Pharma Inc., Zealand Pharma A/S, Other Relationship; Novo Nordisk, Novo Nordisk Pharma, Mayo Clinic, Boehringer-Ingelheim, Scohia Pharma Inc., Research Support; ARLA, European Union, Novo Nordisk Foundation. A.Giaccari: Speaker's Bureau; Abbott, AstraZeneca, Boehringer-Ingelheim, Eli Lilly and Company, Merck Sharp & Dohme Corp., Novo Nordisk, Sanofi. T.Mezza: None. C.Cefalo: None. S.Moffa: None. G.Ciccarelli: None. L.Soldovieri: None. F.Cinti: None. U.Capece: None. F.Impronta: None. A.Mari: Consultant; Eli Lilly and Company. Funding Università Cattolica del Sacro Cuore; European Foundation for the Study of Diabetes; Ministero della Salute