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 3

Aged Cpt1aCKO mice have increased inflammation but not increased fibrosis.

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Aged Cpt1aCKO mice have increased inflammation but not increased fibrosi...
No differences in fibrosis between aged Cpt1aCKO mice and floxed controls were observed by Picrosirius red staining (A) and quantification (n = 3–5) (B) or collagen I staining (C) and quantification (n = 3–6) (D). Aged Cpt1aCKO mice had increased macrophages, measured by immunohistochemistry for F4/80, shown in brown and quantified (n = 4–6) (E and F). Gene expression of IL-1β (Il1b, n = 5) and IL-6 (Il6, n = 5) in renal cortices are quantified by qPCR and normalized to Gapdh (G and H). Renal cortices were immunoblotted for p16 and GAPDH (loading control) and quantified (n = 4) using ImageJ (I and J). The use of GAPDH as loading control was validated against β-actin in Supplemental Figure 4. Data are shown as the mean ± SD. *P < 0.05, ***P < 0.001. One-way ANOVA was performed followed by Šidák’s multiple comparisons test for F, and unpaired t test between the 2 genotypes was used to measure significance in B, G, H, and J. Scale bar: 50 μM.