title: Multiple mass isotopomer tracing of acetyl-CoA metabolism in Langendorff-perfused rat hearts: channeling of acetyl-CoA from pyruvate dehydrogenase to carnitine acetyltransferase.
abstract: We developed an isotopic technique to assess mitochondrial acetyl-CoA turnover (≈citric acid flux) in perfused rat hearts. Hearts are perfused with buffer containing tracer [(13)C2,(2)H3]acetate, which forms M5 + M4 + M3 acetyl-CoA. The buffer may also contain one or two labeled substrates, which generate M2 acetyl-CoA (e.g. [(13)C6]glucose or [1,2-(13)C2]palmitate) or/and M1 acetyl-CoA (e.g. [1-(13)C]octanoate). The total acetyl-CoA turnover and the contributions of fuels to acetyl-CoA are calculated from the uptake of the acetate tracer and the mass isotopomer distribution of acetyl-CoA. The method was applied to measurements of acetyl-CoA turnover under different conditions (glucose ± palmitate ± insulin ± dichloroacetate). The data revealed (i) substrate cycling between glycogen and glucose-6-P and between glucose-6-P and triose phosphates, (ii) the release of small excess acetyl groups as acetylcarnitine and ketone bodies, and (iii) the channeling of mitochondrial acetyl-CoA from pyruvate dehydrogenase to carnitine acetyltransferase. Because of this channeling, the labeling of acetylcarnitine and ketone bodies released by the heart are not proxies of the labeling of mitochondrial acetyl-CoA.
authors: From the Departments of Nutrition and.
authors: Qingling
authors: Q
authors: Li
authors: From the Departments of Nutrition and.
authors: Shuang
authors: S
authors: Deng
authors: From the Departments of Nutrition and.
authors: Rafael A
authors: RA
authors: Ibarra
authors: Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
authors: Vernon E
authors: VE
authors: Anderson
authors: From the Departments of Nutrition and.
authors: Henri
authors: H
authors: Brunengraber
authors: From the Departments of Nutrition and gxz35@case.edu.
authors: Guo-Fang
authors: GF
authors: Zhang
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D002247:Carbon Isotopes / Q000378:metabolism; D002332:Carnitine O-Acetyltransferase / Q000378:metabolism*; D003903:Deuterium / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006019:Glycolysis; D066298:In Vitro Techniques; D007657:Ketone Bodies / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry
chemical_list: D002247:Carbon Isotopes; D007657:Ketone Bodies; D011768:Pyruvate Dehydrogenase Complex; D019298:Glucose-6-Phosphate; D000105:Acetyl Coenzyme A; D003903:Deuterium; D002332:Carnitine O-Acetyltransferase
keywords: Acetoacetate; Acetyl Coenzyme A (Acetyl-CoA); Acetylcarnitine; Acetyltransferase; Cell Compartmentalization; Citric Acid Cycle; Glycolysis; Metabolic Channeling; Metabolomics; Substrate Cycling
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