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Incretin, islet hormone adaptation varied with caloric demands
Increasing meal size prompts a calorie-dependent insulin response due to increased beta-cell secretion that occurs with elevated levels of glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, according to research published in The Journal of Clinical Endocrinology & Metabolism.
In a single-center study involving 24 healthy adults, Wathik Alsalim, MD, of Lund University in Sweden, with colleagues from that institution and the Institute of Biomedical Engineering, National Research Council, Padova, Italy, observed the differences in adaptation responses.
“The increased insulinemia at the two larger meals perfectly adapts to the caloric demand with higher insulin after larger than medium meal size, resulting in identical glucose excursions,” the researchers wrote. “In contrast, after a lower caloric lunch the insulin response seems to be inappropriately high resulting in post-peak suppression of glucose below baseline.”
The researchers gave 12 men and 12 women (mean age, 25 ± 2 years) a standard breakfast after an overnight fast. After 4 hours, participants received lunch of varied calories (511 kcal, 743 kcal or 1,034 kcal) but identical nutrient composition, along with 1.5 g paracetamol.
After meals, glucose, insulin, C-peptide, glucagon, intact GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) and paracetamol were measured.
The investigators were primarily concerned with area under the 180-minute curve (AUC) for insulin, C-peptide, glucagon, GLP-1 and GIP and model-derived beta-cell function and paracetamol appearance.
Similar glucose profiles were seen after the two larger meals. After the smaller meal, however, a post-peak reduction below baseline to a low point of 3.8 ± 0.1 mmol/L after 75 minutes (P<.001) was observed.
By increasing the caloric load, AUC for GLP-1, GIP, insulin and C-peptide were significantly higher, as was beta-cell sensitivity to glucose. Conversely, AUC glucagon remained the same for all three meals, with an increase in glucagon observed after the post-peak glucose reduction in the smaller meal. Paracetamol appearance (0-20 minutes) increased with increasing meal size.
“Based on these findings, we suggest that there is an almost perfect adapting insulin response to caloric demands after mixed lunch meals of medium or large size in healthy humans, whereas a lower-calorie meal may need extra carbohydrate content to prevent eliciting a counter-regulatory response,” the researchers wrote.
Disclosure: The research was supported by the Swedish Research Council, Region Skåne and the Faculty of Medicine, Lund University.