The incretin effect does not differ in trained and untrained, young, healthy men

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Aim: After both oral and intravenous glucose administration, peripheral
insulin concentrations are lower in trained compared with untrained
humans. Part of this is explained by an adaptation within the b-cell. The
insulin secretion rate is higher after oral compared with intravenous glucose
administration due to the release of glucagon-like peptide-1 (GLP-1)
and glucose-dependent insulinotropic polypeptide (GIP) enhancing the glucose-
induced insulin secretion (the incretin effect). Our aim was to investigate
whether GIP or GLP-1 release or the incretin effect was different in
trained compared with untrained humans after oral and intravenous
glucose administration.
Methods: A 3½-h oral glucose tolerance test was performed in eleven
trained and ten untrained, young, healthy men. On a separate day, an isoglycaemic
intravenous glucose infusion was performed matching the individual
glucose concentrations obtained during the oral glucose tolerance
test. Blood samples for insulin, C-peptide, GIP and GLP-1 analyses were
obtained frequently during both tests, and the insulin secretion rate, incretin
effect and insulin clearance were calculated.
Results: Plasma GIP and GLP-1 concentrations, the incretin effect and the
insulin clearance did not differ, and plasma glucose, insulin and C-peptide
concentrations and the insulin secretion rate were lower in trained compared
with untrained subjects during both tests.
Conclusion: With no difference in incretin effect and insulin clearance
between the two groups, the lower plasma insulin concentrations found in
trained compared with untrained, young, healthy men are most likely
explained by lower b-cell sensitivity to glucose and enhanced glucose
uptake in skeletal muscle in the former group.
Original languageEnglish
JournalActa Physiologica
Issue number3
Pages (from-to)565-72
Number of pages8
Publication statusPublished - Mar 2014

ID: 106713600