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Endogenous glucagon production less suppressed with OGTT vs. glucose infusion

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August 23, 2016

Oral glucose tolerance testing results in less-suppressed endogenous glucagon production compared with isoglycemic intravenous glucose infusion in adults with and without diabetes, study data show.

Flip K. Knop, MD, PhD, of the Center for Diabetes Research, Gentofte Hospital, University of Copenhagen in Denmark, and colleagues evaluated 10 adults with type 2 diabetes (mean age, 57.1 years) and 10 matched controls (mean age, 56 years) without diabetes. Researchers sought to determine the differences in suppression of endogenous glucose production during OGTT and isoglycemic IV glucose infusion (IIGI).

Over a minimum 4-week period, all participants underwent three experimental days: 75 g OGTT, IIGI and IIGI with a concomitant glucagon infusion.

In both groups, plasma glucagon concentrations were higher during the initial phase of OGTT compared with the IIGI phase; the increase was greater among the group with diabetes compared with controls (P = .02). Compared with OGTT, higher peak levels of glucagon were observed during the IIGI plus glucagon day (group with diabetes, P < .001; controls, P < .001).

Both groups had higher insulin concentrations, glucose-dependent insulinotropic polypeptide concentrations and glucagon-like peptide-1 concentrations during the OGTT day compared with the other 2 days.

The group with diabetes had higher fasting glucose concentrations (P < .001), higher peak concentrations of glucose (P < .001), higher baseline levels of total glucose rate of appearance and total glucose rate of disappearance (P = .003 for both) compared with controls.

Total glucose rate of appearance and rate of disappearance were higher during OGTT in controls compared with the other 2 days. The control group had higher oral glucose rate of appearance compared with the IV glucose rate of appearance during both the IIGI and IIGI plus glucagon days.

Endogenous glucagon production suppression at baseline was greater in the diabetes group compared with controls (P = .008); all interventions suppressed endogenous glucagon production in both groups. During OGTT, endogenous glucagon production was less suppressed compared with IIGI in both groups.

“We found that [endogenous glucose production] was less suppressed during OGTT than during IIGI in patients with type 2 diabetes as well as in matched nondiabetic control subjects,” the researchers wrote. “Furthermore, we found that glucose disappearance was similar during the two glucose administration routes in patients with type 2 diabetes, but greater during OGTT compared to during IIGI in nondiabetic control subjects.” – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.