Metabolism of Islets of Langerhans and Hormone Release

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DESCRIPTION (provided by applicant): The long-term goal of the research program supported by the present grant is to understand in depth the role of intermediary metabolism of pancreatic beta-cells in fuel stimulated insulin release. Glucose and glutamine metabolism and their interconnections are the primary focus. This program is strongly influenced by relevant clinical studies of well-defined, inherited, hypo- and hyperglycemia syndromes in men, including Glucokinase Disease and GDH or SUR-1/Kir 6.2 linked hypoglycemia. We have formulated the following projects. Project 1. Continue structure/activity studies of glucokinase (GK) using spontaneous and designer mutants of the enzyme with emphasis on the unexplained MODY-2 and PNDM-GK cases, on selected newly-discovered cases of GK disease and on the molecular basis and physiological relevance of nonessential heterotopic allosteric activation of GK. Project 2. Investigate expression control of GK in beta-cells by focusing on the direct control of glucose and/or other fuel molecules and possible modifications by hormones and neurotransmitters, in particular on the possibility of an indirect autocrine role of insulin in the process. Project 3. Study the role of glutamine metabolism and its regulation by glucose in beta-cell function by focusing on the molecular mechanisms that regulate glutaminase, glutamine synthetase, glutamate dehydrogenase and transaminases, and exploring a hypothetical dual role of glutamine as fuel and as cofactor in stimulated insulin release.