Potentiation of the early-phase insulin response by a prior meal contributes to the second-meal phenomenon in type 2 diabetes.

Improved glucose tolerance following a sequential meal is known as the second-meal phenomenon. We aimed to investigate its extent and underlying mechanisms in patients with type 2 diabetes. Metabolic responses after lunch in 12 diabetic patients were compared on two separate days: one with (Day BL) and another without (Day FL) breakfast. The responses of hormones were calculated by the incremental area under the curve (iAUC) values for 180 min after each meal. Indexes of early-phase insulin secretion were assessed, and β-cell function was estimated by mathematical modeling. [iAUC(glucose(180-360 min))] was significantly lower on Day BL than on Day FL (181 ± 43 vs. 472 ± 29 mmol·liter(-1)·min, P = 0.0005). The magnitude of the The second-meal phenomenon [iAUC(glucose(180-360 min)) on Day BL/Day FL] was 35 ± 9%. The peak levels of insulin and C-peptide were attained 45 min earlier after the second meal than after the first meal. iAUC(glucose(180-360 min)) correlated negatively with iAUC(insulin(180-210 min)) (r = -0.443, P = 0.0300), insulinogenic index (r = -0.769, P < 0.0001), acute C-peptide response (r = -0.596, P = 0.0021), and potentiation factor [i.e., potentiation effect on insulin secretion] ratio (180-360)/(0-20) (r = -0.559, P = 0.0045), while correlated positively with free fatty acid level before lunch (r = 0.679, P = 0.0003). The second-meal phenomenon was evident in patients with type 2 diabetes. Potentiation of the early-phase insulin response by a prior meal contributes to this phenomenon in type 2 diabetes.