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 8

RNA-Seq showing Cpt1aCKO kidneys with upregulated PPAR gene expression.

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RNA-Seq showing Cpt1aCKO kidneys with upregulated PPAR gene expression. ...
Bulk RNA-Seq on aged Cpt1afl/fl and Cpt1aCKO kidneys and gene ontology overrepresentation analysis (ORA) were performed using enrichGO from clusterProfiler. Gene networks and pathways significantly altered between genotypes are shown (A and B), with the pathways and genes specifically related to fatty acid metabolism listed (C). Significant changes in Fabp1, a known transcriptional target of PPARα, expression, that were identified by RNA-Seq were confirmed with qPCR (n = 5–6) (D). Pdk4, another target involved in glycolysis, was significantly upregulated in aged Cpt1aCKO murine kidneys in RNA-Seq (E) and confirmed by qPCR (n = 5–6) and protein expression (n = 3) (F and G). Scale bar: 50 μm. Primary PT cells with or without PPARα inhibitor (GW6371) had OCR responses to palmitate measured by Seahorse with a representative tracing shown (H) and quantified (I). Data are shown as the mean ± SD. *P < 0.05, **P < 0.01. Statistical significance between the 2 genotypes was determined by unpaired t test for D–F. One-way ANOVA was performed followed by Šidák’s multiple comparisons test for H.