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 7

Assessment of Cpt1a tubular deletion on mitochondria.

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Assessment of Cpt1a tubular deletion on mitochondria. Mitochondrial DNA ...
Mitochondrial DNA copy number was measured using mitochondrial-encoded ND1 gene expression and normalized to nuclear-encoded actin (n = 4–5) (A). The common mitochondrial mutation, D17, was measured using qPCR and normalized to mitochondrial ND1 expression (n = 4–5) (B). Mitochondrial complexes were measured and quantified using immunoblots on cortical kidney tissue using ImageJ from aged (C and D), aristolochic acid–treated (AA-treated) (E and F), and UUO-injured mice (n = 4–5) (G and H). Representative electron micrograph images are shown (I) from aged mice, with quantification of area and aspect ratio (J and K) (see Methods). Each dot represents an average value for 1 mouse (n = 3). 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, except for A and B, where 1-way ANOVA was performed, followed by Šidák’s multiple comparisons. Scale bar: 500 nM.