Insulin release : the fuel concept.

Insulin release evoked by nutrient secretagogues invariably coincides with an increase in the catabolism of exogenous and/or endogenous nutrients in pancreatic islet cells, resulting in an increased generation rate of reducing equivalents and ATP, and an increase in O2 consumption. This situation was documented in response to a number of carbohydrates, including the anomers of D-glucose and D-mannose, various 2-keto acids, including pyruvate and its poorly oxidized phenylated analog 3-phenylpyruvate, and selected amino acids, including the nonmetabolized analog of L-leucine 2-aminobicyclo[2, 2, 1]heptane-2-carboxylic acid. These convergent observations indicate that the B-cell should be considered as a fuel-sensor organ. Further progress in this field requires both the identification of those circulating nutrients used by the B-cell whether in the resting or stimulated state, and a better understanding of the coupling between the generation of second messengers (H+, NAD(P)H, ATP) and more distal events in the secretory sequence, such as the remodelling of ionic fluxes across the plasma membrane and within the pancreatic B-cell.