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Blood glucose concentration is controlled by a number of hormone and neurotransmitter signals, either increasing or reducing glucose levels in the case of hypoglycemia or hyperglycemia, respectively. The pancreatic beta-cell responds to an increase in circulating glucose levels by a cascade of metabolic and electrophysiological events leading to the secretion of insulin. Type 2 diabetes is a metabolic disorder characterized by chronic hyperglycemia; the progressive pancreatic beta-cell dysfunction, with altered insulin production and secretion, is a major pathophysiological determinant of the disease together with the resistance of insulin-sensitive tissues to the action of the hormone. Hence, drugs which stimulate or enhance insulin secretion will reduce plasma glucose concentrations; this lowering of hyperglycemia will, in turn, reduce the occurrence of long-term complications. K(ATP) channels play a critical role in insulin secretion and can be considered as transducers of glucose-induced metabolic changes into biophysical events leading to the exocytosis of insulin granules. All currently marketed insulin secretagogues, sulfonylureas and glinides, target the beta-cell K(ATP) channels and reduce their opening probability. They induce insulin release regardless of the plasma glucose concentration, thus favoring the occurrence of hypoglycemia in the fasting state. Despite the intensive use of current drugs, many patients suffering from type 2 diabetes still exhibit poor glycemic control, others fail to respond to the treatment, and some develop serious complications. Therefore, there is a real need for innovative compounds, either enhancing insulin secretion from the pancreas or improving insulin action on the hormone-sensitive tissues. Here, we overview the existing and novel approaches targeting the beta-cell to enhance the release of insulin, with special emphasis on new ways of amplifying insulin secretion in a glucose-dependent manner.

P2Y 12 receptors as future antidiabetic targets in human pancreatic islets and to determine their cellular localization: 1. An increase in cAMP is responsible for the glucose-dependant insulinotropic effect of GLP-1, the most promising antidiabetic drug presently in development; 2. P2Y agonists induce a glucose-dependent increase in insulin secretion in human pancreatic islets [11] ; and 3. The cAMP / PKA pathway intervenes in ATP S insulin secretory effect in rat islets [12] . Materials and Methods & Isolation of human isletsHuman pancreata were obtained from healthy brain-dead donors in the context of a human islet transplantation protocol, as previously reported [13] . After perfusion and extraction, organs were maintained at 4 ° C for 2 -6 hours in a solution developed by the University of Wisconsin. Human islets were then isolated after digestion according to a modifi cation of Ricordi ' s automatic method. Islets were then collected by hand-picking under a stereomicroscope and frozen at − 80 ° C. RNA isolation and RT-PCRTotal RNAs were isolated by TRIzol Reagent (Invitrogen, Carlsbad, CA) from human islets and treated with DNAse I. Then, fi rst strand cDNA was generated from 3 g RNA by using Superscript II RNAse H -Reverse Transcriptase (Invitrogen), oligo(dT) (Promega, Madison, WI), and random primers (Promega). Subsequently, PCR was carried out using the following conditions: 95 ° C for 3 minutes, 95 ° C for 30 seconds, 56 ° C for 45 seconds, 72 ° C for 30 seconds (45 cycles), and fi nally 72 ° C for 5 minutes. The sequences of the primers used for P2Y 11 were 5 Ј -ACTGGTGGTTGAGTTC-CTGG-3 Ј and 5 Ј -TCAGGTGGGAGAAGCTGAGT-3 Ј

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