Metabolic regulation of islet hormone secretion in diabetes

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Over 29 million Americans suffer from diabetes, including 25% of Veterans seeking VA healthcare. A strong contributor to type 2 diabetes (T2D) is that obesity rates have increased dramatically in the last 3 decades, now reaching over 30% in many parts of the country with rates over 40% in Veterans, who are disproportionally affected by diabetes. In the United States, nearly 1 in 4 Veterans receiving care from the VA, and 20% of Veterans overall have diabetes (compared to 9% in the general population). The prevalence of diabetes is even higher in Veterans over the age of 65, and across all ages the prevalence of diabetes in Veterans is climbing by 2% every year. Developing new methods for properly treating the failure of insulin secretion in T2D patients is therefore a high priority for the Veteran population. One molecule that is at the cornerstone of our research program, the glycolytic enzyme pyruvate kinase (PK), has strong potential to be of protective and therapeutic value. We have discovered that small-molecule PK activators control multiple cell types in the pancreatic islet and enhance insulin secretion, including in human islets from obese and T2D donors. The objective of this proposal is to identify the mechanisms by which PK activation is able to enhance insulin secretion at the cellular and molecular level. Based on our preliminary studies, our central hypothesis is that PK controls both α- and β- cell hormone secretion by closing ATP-sensitive K+ channels (KATP). The physiological model being tested is that islet α-cells, which are activated by amino acids, supercharge β-cell secretion to lower postprandial blood glucose. We will test our central hypothesis in multiple pre-clinical models of diabetes, and accomplish the objective of this proposal by completing the following specific aims: 1) Determine the effect of PK activation on α-cell metabolism and hormone secretion, 2) Determine how α-cell hormones enhance the β-cell response to PK activators, and 3) Assess the therapeutic potential of combining PK activators with Glp1 receptor agonists to prevent and rescue obesity/T2D. With the completion of these aims, we will gain a significantly more comprehensive understanding of PK function in the pancreatic islet, and take the critical next steps in evaluating PK as a new target for the prevention and treatment of type 2 diabetes.