Chicco 2013 Abstract IOC79

Chicco AJ (2013) Substrate-specific impairment of oxidative phosphorylation in Tafazzin-deficient cardiac mitochondria: potential role of CoA deficiency. Mitochondr Physiol Network 18.07

Link: http://www.barthsyndrome.org/english/view.asp?x=1

Le CH, deMooy AB, Mulligan CM, Heuberger AL, Prenni JE, Chicco AJ (2013)

Event: IOC79

Barth syndrome is an X-linked cardioskeletal myopathy that results from mutations in the Tafazzin (Taz) gene encoding a phospholipid transacylase required for the remodeling of the cardiolipin. Cardiolipin is an inner mitochondrial membrane phospholipid essential for the function of several mitochondrial proteins, but how Taz deficiency and defective cardiolipin remodeling influences mammalian mitochondrial function is unclear. We recently characterized the cardiac mitochondrial phenotype of a new Taz shRNA mouse model of BTHS by high resolution respirometry (HRR) on isolated mitochondria and permeabilized heart fibers, complemented by cardiac metabolomics and mitochondrial proteomic profiling. HRR revealed 40-60% lower rates of oxidative phosphorylation in Taz shRNA compared to wild-type (WT) mitochondria using pyruvate and palmitoylcarnitine (+ malate) as substrates in isolated subsarcolemmal and interfibrillar mitochondria, as well as permeabilized cardiac muscle fibers. Less robust impairments were seen in complex II-supported respiration (12%) and maximal enzymatic activity of respiratory complexes 1 (17%) and 4 (26%) in Taz shRNA vs. WT mitochondria. Unexpectedly, glutamate + malate respiration was markedly elevated in Taz shRNA vs. WT, reaching respiratory rates equal to those obtained with pyruvate and fatty acid substrates in WT mitochondria and fibers. Analysis of the Taz shRNA mitochondrial proteome revealed deficiencies in enzymes involved in amino acid catabolism, respiratory complex 1 assembly and fatty acid oxidation, while stress response enzymes, acyl-CoA thioesterases, and malate dehydrogenase were elevated. Cardiac metabolomics revealed a marked deficiency in pantothenic acid that paralleled 43% lower levels of CoA in Taz shRNA vs. WT mitochondria. To further investigate the potential role of CoA deficiency on the observed respiratory phenotype, isolated mitochondria were incubated with exogenous CoA prior to respirometry experiments, which significantly improved OXPHOS rates using pyruvate as a substrate. Taken together, our studies indicate that while Taz deficiency elicits expected impairments in respiratory chain function, the primary defect is a selective impairment of carbohydrate and lipid oxidation, perhaps due to a deficiency in mitochondria CoA that deserves further investigation.

• Keywords: cardiolipin, heart failure, diabetes, polyunsaturated fatty acids, comparative biology

• O2k-Network Lab: US CO Fort Collins Chicco AJ

Labels: MiParea: Respiration, Genetic knockout;overexpression  Pathology: Inherited  Stress:Mitochondrial disease  Organism: Mouse  Tissue;cell: Heart  Preparation: Permeabilized cells, Isolated mitochondria 

Regulation: Flux control, Substrate, Fatty acid  Coupling state: OXPHOS  Pathway: F, N, S  HRR: Oxygraph-2k 

Colorado State University, Fort Collins, CO USA.