Sulfonylurea Stimulation of Insulin Secretion Peter Proks,1 Frank Reimann,2 Nick Green,1 Fiona Gribble,2 and Frances Ashcroft1
Sulfonylurea Stimulation of Insulin Secretion Peter Proks,1 Frank Reimann,2 Nick Green,1 Fiona Gribble,2 and Frances Ashcroft1 Sulfonylureas are widely used to treat type 2 diabetes smooth, and skeletal muscle, and some brain neurones. In because they stimulate insulin secretion from pancre- all these tissues, opening of KATP channels in response to atic -cells. They primarily act by binding to the SUR metabolic stress leads to inhibition of electrical activity. subunit of the ATP-sensitive potassium (KATP) channel Thus they are involved in the response to both cardiac and and inducing channel closure. However, the channel is cerebral ischemia (2). They are also important in neuronal still able to open to a limited extent when the drug is regulation of glucose homeostasis (3), seizure protection bound, so that high-affinity sulfonylurea inhibition is not complete, even at saturating drug concentrations. (4), and the control of vascular smooth muscle tone (and, thereby, blood pressure) (5). KATP channels are also found in cardiac, skeletal, and smooth muscle, but in these tissues are composed of The KATP channel is a hetero-octameric complex of two different SUR subunits that confer different drug different types of protein subunits: an inwardly rectifying sensitivities. Thus tolbutamide and gliclazide block Kϩ channel, Kir6.x, and a sulfonylurea receptor, SUR (6,7).  ϩ channels containing SUR1 ( -cell type), but not SUR2 Kir6.x belongs to the family of inwardly rectifying K (cardiac, smooth muscle types), whereas glibenclamide, (Kir) channels and assembles as a tetramer to form the glimepiride, repaglinide, and meglitinide block both types of channels.
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