Mechanisms of metformin action: In and out of the gut.

Recent evidence suggests that metformin exerts glucose-lowering effects via its action in the gut. The accumulation in the colon of 18 F-labeled fluorodeoxyglucose (FDG), a nonmetabolizable derivative of glucose, is markedly augmented after metformin administration, indicating that metformin affects the handling of glucose in colon whereas the underlying mechanism and the significance to glucose metabolism of the finding remain to be determined.