Tubular CPT1A deletion minimally affects aging and chronic kidney injury
Safaa Hammoud, Alla Ivanova, Yosuke Osaki, Steven Funk, Haichun Yang, Olga Viquez, Rachel Delgado, Dongliang Lu, Melanie Phillips Mignemi, Jane Tonello, Selene Colon, Louise Lantier, David H. Wasserman, Benjamin D. Humphreys, Jeffrey Koenitzer, Justin Kern, Mark de Caestecker, Toren Finkel, Agnes Fogo, Nidia Messias, Irfan J. Lodhi, Leslie S. Gewin
Safaa Hammoud, Alla Ivanova, Yosuke Osaki, Steven Funk, Haichun Yang, Olga Viquez, Rachel Delgado, Dongliang Lu, Melanie Phillips Mignemi, Jane Tonello, Selene Colon, Louise Lantier, David H. Wasserman, Benjamin D. Humphreys, Jeffrey Koenitzer, Justin Kern, Mark de Caestecker, Toren Finkel, Agnes Fogo, Nidia Messias, Irfan J. Lodhi, Leslie S. Gewin
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Research Article Metabolism Nephrology

Tubular CPT1A deletion minimally affects aging and chronic kidney injury

Abstract

Kidney tubules use fatty acid oxidation (FAO) to support their high energetic requirements. Carnitine palmitoyltransferase 1A (CPT1A) is the rate-limiting enzyme for FAO, and it is necessary to transport long-chain fatty acids into mitochondria. To define the role of tubular CPT1A in aging and injury, we generated mice with tubule-specific deletion of Cpt1a (Cpt1aCKO mice), and the mice were either aged for 2 years or injured by aristolochic acid or unilateral ureteral obstruction. Surprisingly, Cpt1aCKO mice had no significant differences in kidney function or fibrosis compared with wild-type mice after aging or chronic injury. Primary tubule cells from aged Cpt1aCKO mice had a modest decrease in palmitate oxidation but retained the ability to metabolize long-chain fatty acids. Very-long-chain fatty acids, exclusively oxidized by peroxisomes, were reduced in kidneys lacking tubular CPT1A, consistent with increased peroxisomal activity. Single-nuclear RNA-Seq showed significantly increased expression of peroxisomal FAO enzymes in proximal tubules of mice lacking tubular CPT1A. These data suggest that peroxisomal FAO may compensate in the absence of CPT1A, and future genetic studies are needed to confirm the role of peroxisomal β-oxidation when mitochondrial FAO is impaired.

Authors

Safaa Hammoud, Alla Ivanova, Yosuke Osaki, Steven Funk, Haichun Yang, Olga Viquez, Rachel Delgado, Dongliang Lu, Melanie Phillips Mignemi, Jane Tonello, Selene Colon, Louise Lantier, David H. Wasserman, Benjamin D. Humphreys, Jeffrey Koenitzer, Justin Kern, Mark de Caestecker, Toren Finkel, Agnes Fogo, Nidia Messias, Irfan J. Lodhi, Leslie S. Gewin

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Figure 6

Primary proximal tubule–enriched cells lacking Cpt1a have altered metabolism but are still able to metabolize LCFA.

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Primary proximal tubule–enriched cells lacking Cpt1a have altered metabo...
Representative data from Seahorse analysis show oxygen consumption rate (OCR) after treatment with palmitate, FCCP, and antimycin A/rotenone in primary proximal tubule–enriched cells (PT cells) from aged mice (A). An expanded view (boxed area in A) of the OCR response to palmitate is shown (B). Average OCR responses to palmitate from Cpt1afl/fl (n = 4) and Cpt1aCKO (n = 3) mice are quantified (C). Representative tracing from PT cells isolated from young mice showing OCR after palmitate, oligomycin, FCCP, and antimycin A/rotenone (D) with an expanded view of the response to palmitate (E) and quantification of this palmitate response with n = 8 per genotype (F). Kidney tissues from young Cpt1afl/fl and Cpt1aCKO mice were used to measure oxygen consumption in response to palmitoyl-CoA, a LCFA (G). Each dot represents a separate kidney (n = 3), and oxygen consumption is measured as picomole per second per mg of kidney (wet weight). Representative data from a glycolysis test measuring extracellular acidification rate (ECAR) are shown (H). Oligomycin is used to detect maximal glycolytic capacity, and 2-DG blocks glycolytic acidification to define the glucose-dependent ECAR (I). Glycolytic capacity of primary PT cells from young and old mice (each dot represents a separate mouse n = 3–4) and glycolytic reserve (the ECAR value after oligomycin minus that after the addition of glucose) are shown (J). Results are shown as the mean ± SD. *P < 0.05, **P < 0.01. Unpaired t test between the 2 genotypes was used to detect statistical significance. FCCP, carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone; 2-DG, 2-deoxy-glucose; LCFA, long-chain fatty acid.