The vascular architecture of the pancreatic islets: A homage to August Krogh.

The vascular network supporting the islets of Langerhans represents a highly specialised system of arterioles, capillaries and venules. Several features of the islet vasculature (density and fenestration of the capillaries) ensure rapid exchange of nutrients and hormones, which is central to the islets' capacity to control of systemic metabolism via reciprocal changes of insulin and glucagon secretion. Here we discuss how changes in islet blood flow may underlie pulsatile insulin secretion, which becomes impaired in type-2 diabetes. Improved understanding of the architecture and regulation of pancreas/islet blood flow may therefore illuminate the causes underlying this common metabolic disorder. The pioneering work of August Krogh on blood flow, oxygen diffusion and capillary anatomy (that was awarded with the Nobel Prize in 1920) is a cornerstone in these efforts and remains relevant to today's research.