Pancreatic β-cell Function is Higher in Morning Versus Intermediate Chronotypes With Obesity

Abstract

Objectives: People with later chronotypes are at greater T2D risk, yet it is unknown if β-cell function differs among chronotypes. Thus we, assessed β-cell function in morning (MORN) and intermediate (INT) chronotypes with obesity. Methods: Adults (n = 41, 9M, 55 ± 1.7 y, 36.8 ± 1.0 kg/m2) were grouped as MORN or INT per the Morningness-Eveningness Questionnaire. Glucose, insulin, C-peptide, GIP, and GLP-1(active) were collected every 30 min during a 120 min 75g-OGTT. Insulin secretion rates (ISR) were calculated (regularized deconvolution) to assess early (total area under the curve; tAUC0–30min) and total-phase (tAUC0–120min) glucose-stimulated insulin secretion (GSIS:ISR/Glucose). Skeletal muscle (glucose infusion rate/steady-state insulin) insulin sensitivity and hepatic (HOMA-IR) as well as adipose (Adipose-IR) insulin resistance were assessed during a 120 min euglycemic hyperinsulinemic clamp (40mU/m2/min, 90 mg/dL). β-cell function (disposition index (DI): GSIS adjusted insulin sensitivity) was determined. Body composition (DXA) and fitness (VO2max) were also measured. Results: Age, body composition and VO2max were similar between groups, but INT had reduced muscle insulin sensitivity and higher hepatic and adipose IR (p < 0.05). INT had higher C-peptide tAUC0–30min (p = 0.04) and lower hepatic DI (tAUC0–30min p = 0.05 and tAUC0–120min p = 0.07, respectively). Early phase hepatic DI correlated with GLP-1 tAUC0–30min (r = 0.35, p < 0.02) and tAUC0–120min (r = −0.40, p = 0.04). Conclusions: β-cell function was higher in MORN versus INT chronotypes. Further work is warranted to discern how chronotype impacts insulin secretion. Trial Registration: NCT03355469.