The insulin response to intravenous fructose in relation to blood glucose levels.

The insulinotropic action of intravenous fructose was examined in 24 subjects without known metabolic disease. When blood glucose values before the fructose infusion were at or below normal fasting levels, fructose elicited only a small plasma insulin response. In contrast, the insulin response was strikingly augmented when preinfusion blood glucose and plasma insulin levels were moderately elevated. The insulinotropic action of fructose appears closely related to the preinfusion blood glucose level. Fructose has little or no insulinotropic action in the absence of glucose but potentiates glucose-mediated insulin release. The insulinotropic potency of other glucose analogues in vivo may show a similar dependence on concomitant blood glucose levels.