Regulatory Role of Fructose-2,6-Bisphosphate in Pancreatic Islet Glucose Metabolism Remains Unsettled

Fructose-2,6-P₂ was measured in perifused, isolated rat pancreatic islets. Fructose-2,6-P₂ was present in pancreatic islets at low levels approximately equal to fructose-2,6-P₂ content of liver from fasted rats. In islets perifused with glucose at physiologic concentrations, fructose-2,6-P₂ was increased from 0.8 μM in the presence of 5.5 mM glucose to 1.0 μM at 10 mM glucose and 1.3 μM at 16.7 mM glucose, but did not increase further at higher glucose concentration. Therefore, only modest increases in the phosphofructokinase-1 activator, fructose-2,6-P₂, occur at glucose concentrations stimulating insulin secretion.