Inborn Errors of Long Chain Fat Metabolism

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DESCRIPTION (provided by applicant): This application addresses Notice Number (NOT-OD-09-058) and Notice Title: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications, and asks for competitive revision of R01DK78755. The acyl-CoA dehydrogenases (ACDs) are a family of multimeric flavoenzymes that catalyze the 1,2-dehydrogenation of acyl-CoA esters in fatty acid 2-oxidation and amino acid catabolism. Inborn errors of metabolism have been identified in seven of the ACDs. The long range objective of this project has been to investigate important structure/function relationships in the ACD gene family. We have described and characterized several new members of the ACD gene family. Among these are 3 enzymes with significant activities with long chain substrates: long and very long chain acyl-CoA dehydrogenases (LCAD and VLCAD, respectively), and ACD9 and. Our prior and preliminary studies show that these enzymes have distinct substrate utilization profiles, tissue and developmental expression patterns, exist in multiple active forms in the cell, and are present in multiple subcellular locations. The goal of the funded application is to characterize the physiologic roles of LCAD, VLCAD, and ACD9 and explore the ramifications of genetic deficiencies of these enzymes in humans and mouse models. Specific Aim 2 of the original application is to more completely characterize ACD9 and its deficiency in humans. Specific Aim 2a is identification of additional patients with ACD9 deficiency and definition of its clinical spectrum. Specific Aim 2b is characterization of the subcellular distribution of ACD9 and the function and molecular configuration of ACD9 protein outside of mitochondria. I hypothesize that this alternative form of ACD9 has non-enzymatic "moonlighting" functions in the cell. I am requesting a supplement to the application to extend my ability to address these aims. First, I have identified more potential deficient patients than originally anticipated. I am requesting funds to support additional technician time to process these samples more quickly and accelerate our progress. Secondly, our understanding of the pathophysiology of ACAD9 deficiency and our ability to study the moonlighting functions of this gene product are limited by the availability of only tissue culture cells with ACAD9 deficiency. To augment these studies, I am requesting supplemental funds to purchase an ACAD9 knock out mouse from the Texas A&M Institute for Genome Medicine, which has it available in its catalogue. The biochemical and pathophysiologic phenotype of the animal will be characterized including metabolic profiling, complete histologic survey, and physiologic effects of the deficiency on the animal under basal and resting conditions. Immunohistochemistry and subcellular fractionation studies will examine for presences of ACAD9 in non-mitochondrial locations and loss in the knock out mouse model. PUBLIC HEALTH RELEVANCE: The acyl-CoA dehydrogenases are important enzymes in maintaining normal chemical balance in the body. We have identified a new genetic disorder of one of these enzymes that leads to liver failure. Studying this disorder is important to learn more about its clinical presentation and treatment