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Ola Lindgren, Andrea Mari, Carolyn F. Deacon, Richard D. Carr, Maria Sörhede Winzell, Jenny Vikman, Bo Ahrén, Differential Islet and Incretin Hormone Responses in Morning Versus Afternoon after Standardized Meal in Healthy Men, The Journal of Clinical Endocrinology & Metabolism, Volume 94, Issue 8, 1 August 2009, Pages 2887–2892, https://doi.org/10.1210/jc.2009-0366
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Context: The insulin response to meal ingestion is more rapid in the morning than in the afternoon. Whether this is explained by a corresponding variation in the incretin hormones is not known.
Objective: Our objective was to assess islet and incretin hormones after meal ingestion in the morning vs. afternoon.
Design, Settings, and Participants: Ingestion at 0800 and 1700 h of a standardized meal (524 kcal) in healthy lean males (n = 12) at a University Clinical Research Unit.
Main Outcome Measures: We assessed early (30-min) area under the curve (AUC30) of plasma levels of insulin and intact (i) and total (t) glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) after meal ingestion and made an estimation of β-cell function by model analysis of glucose and C-peptide.
Results: Peak glucose was lower in the morning than in the afternoon (6.1 ± 0.2 vs. 7.4 ± 0.3 mmol/liter, P = 0.001). AUC30insulin (4.9 ± 0.6 vs. 2.8 ± 0.4 nmol/liter · 30 min; P = 0.012), AUC30tGLP-1 (300 ± 40 vs. 160 ± 30 pmol/liter · 30 min, P = 0.002), AUC30iGIP (0.7 ± 0.1 vs. 0.3 ± 0.1 nmol/liter · 30 min, P = 0.002), and AUC30tGIP (1.1 ± 0.1 vs. 0.6 ± 0.1nmol/liter · min, P = 0.007) were all higher in the morning. AUC30iGLP-1 (r = 0.68; P = 0.021) and AUC30iGIP (r = 0.78; P = 0.001) both correlated to AUC30insulin. Model analysis of β-cell function showed a higher first-hour potentiation factor in the morning (P = 0.009). This correlated negatively with the 60-min glucose level (r = −0.63; P < 0.001).
Conclusions: The early release of GLP-1 and GIP are more pronounced in the morning than in the afternoon. This may contribute to the more rapid early insulin response, more pronounced potentiation of β-cell function, and lower glucose after the morning meal.
