Improved tolerance to sequential glucose loading (Staub-Traugott effect): size and mechanisms

Bonuccelli S, Muscelli E, Gastaldelli A, Barsotti E, Astiarraga BD, Holst JJ, Mari A, Ferrannini E. Improved tolerance to sequential glucose loading (Staub-Traugott effect): size and mechanisms. Am J Physiol Endocrinol Metab 297: E532-E537, 2009. First published June 16, 2009; doi:10.1152/ajpendo.00127.2009. - Improved glucose tolerance to sequential glucose loading (Staub-Traugott effect) is an important determinant of day-to-day glycemic exposure. Its mechanisms have not been clearly established. We recruited 17 healthy volunteers to receive two sequential oral glucose tolerance tests (OGTTs), at time 0 min and 180 min (Study I). The protocol was repeated on a separate day (Study II) except that plasma glucose was clamped at 8.3 mmol/l between 60 and 180 min. beta-Cell function was analyzed by mathematical modeling of C-peptide concentrations. In a subgroup, glucose kinetics were measured by a triple-tracer technique (infusion of [6,6-H-2(2)] glucose and labeling of the 2 glucose loads with [1-H-2] glucose and [U-C-13] glucose). In both Studies I and II, the plasma glucose response to the second OGTT equaled 84 +/- 2% (P = 0.003) of the response to the first OGTT. Absolute insulin secretion was lower (37.8 +/- 4.3 vs. 42.8 +/- 5.1 nmol/m(2), P = 0.02), but glucose potentiation (i. e., higher secretion at the same glycemia) was stronger (1.08 +/- 0.02 vs. 0.92 +/- 0.02-fold, P = 0.006), the increment being higher in Study II (+36 +/- 5%) than Study I (+19 +/- 6%, P < 0.05). In pooled data, a higher glucose area during the first OGTT was associated with a higher potentiation during the second OGTT (rho = 0.60, P = 0.002). Neither insulin clearance nor glucose clearance differed between loads, and appearance of glucose over 3 h totalled 60 +/- 6 g for the first load and 52 +/- 5 g for the second load (P = not significant). Fasting endogenous glucose production [13.3 +/- 0.6 mu mol.min(-1).kg fat-free mass (FFM)(-1)] averaged 6.0 +/- 3.8 mu mol.min(-1).kg FFM-1 between 0 and 180 min and 1.7 +/- 2.6 between 180 and 360 min (P < 0.03). Glucose potentiation and stronger suppression of endogenous glucose release are the main mechanisms underlying the Staub-Traugott effect.