DIABETES AND BLADDER SMOOTH MUSCLE METABOLIC DYSFUNCTION

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One widespread complication of diabetes mellitus is urinary bladder dysfunction. Although there have been numerous studies on the effects of experimental diabetes on overall bladder function, few studies have been aimed at understanding the metabolic dysfunction of the major cellular component of urinary bladder which is smooth muscle. The metabolic pathologies associated with diabetes in smooth muscle of large arteries involve cell phenotypic transformation and alterations in lipid and glucose metabolism. However, in microvascular smooth muscle, pathological flux through the sorbitol pathway is a primary defect. The metabolic pathologies associated with diabetes in bladder smooth muscle are unknown. The experiments proposed in this application will utilize state-of-the-art multinuclear NMR spectroscopic methods to investigate several possible sites of metabolic dysfunction in bladder smooth muscle from diabetic/hyperlipidemic pigs. Since smooth muscle function is closely linked to smooth muscle metabolism, metabolic dysfunctions unveiled by these studies will provide key insights into the mechanisms of diabetes-induced myopathies of bladder smooth muscle. The investigators will use 1 C-NMR isotopomer analysis of glutamate to examine the substrate selection by oxidative metabolism in bladder smooth muscle from normal (specific aim 1a) and diabetic/hyperlipidemic (specific aim 1b) pigs. The factor(s) responsible for any alterations in substrate selection will be identified in controlled organ culture of bladder smooth muscle (specific aim 1c). The mechanism(s) for the alteration in substrate selection (inhibition of pyruvate dehydrogenase or glucose transport/phosphorylation) will be examined using 31P-NMR (specific aim 1d). In various smooth muscles carbohydrate metabolism is structured (compartmentalized) and this compartmentalization fundamentally alters metabolic regulation and cell function. The investigators will use 1H-NMR to measure the extent of compartmentation of carbohydrate metabolism in bladder smooth muscle from normal and diabetic/hyperlipidemic pigs (specific aim 2). To determine whether bladder smooth muscle exhibits metabolic pathology similar to microvascular smooth muscle, the investigators will measure sorbitol pathway activity (1-13C-sorbitol production specifically from 1-13C- glucose) and determine the metabolic consequences of enhanced sorbitol pathway flux (specific aim 3). These experiments will provide fundamental insights to the normal metabolism of the bladder smooth muscle and to the pathological metabolic changes associated with diabetes.