Gannon, Mary C., Ph.D.

ENDOCRINOLOGY AND METABOLISM/NUTRITIONAL BIOCHEMISTRY

Our research is aimed at understanding the mechanism by which ingested nutrients affect carbohydrate metabolism. Ingestion of various nutrients results in changes in several hormone and metabolite concentrations. Many of these hormones, e.g., insulin, glucagon, gastric inhibitory polypeptide, and metabolites, e.g., ATP, AMP, Pi affect enzymes that regulate intermediary metabolism. We would like to identify the changes in hormone levels and metabolite concentrations that occur following ingestion of different carbohydrates, proteins, and fats, and determine how these changes regulate carbohydrate storage or utilization. We have cloned one of the genes involved in glycogen metabolism (human liver glycogen synthase) and localized it to chromosome 12. We have begun work on an expression vector system in which the catalytic activity and allosteric regulation of the enzyme, glycogen synthase, are maintained. Such a system will allow site-directed mutagenesis studies to be performed. We also have done considerable work on the characterization of the enzyme liver glycogenin, which is involved in de novo glycogen synthesis. In addition, we also have been interested in determining the effect of ingestion of various individual foods, and mixed meals on plasma glucose, insulin and glucagon concentrations in order to be able to make recommendations for the dietary management of diabetes mellitus. We would like to be able to design a diet that is both acceptable to patients and likely to result in a lower blood glucose concentration (integrated over an extended period of time) than the typical American diet, or the diet recommended by the American Diabetes Association, American Heart Association, or the US Government for the general population.