Renal tubule Cpt1a overexpression protects from kidney fibrosis by restoring mitochondrial homeostasis
Verónica Miguel, … , Ricardo Ramos, Santiago Lamas
Verónica Miguel, … , Ricardo Ramos, Santiago Lamas
Published January 19, 2021
Citation Information: J Clin Invest. 2021;131(5):e140695. https://doi.org/10.1172/JCI140695.
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Research Article Nephrology

Renal tubule Cpt1a overexpression protects from kidney fibrosis by restoring mitochondrial homeostasis

Abstract

Chronic kidney disease (CKD) remains a major epidemiological, clinical, and biomedical challenge. During CKD, renal tubular epithelial cells (TECs) present a persistent inflammatory and profibrotic response. Fatty acid oxidation (FAO), the main source of energy for TECs, is reduced in kidney fibrosis and contributes to its pathogenesis. To determine whether gain of function in FAO (FAO-GOF) could protect from fibrosis, we generated a conditional transgenic mouse model with overexpression of the fatty acid shuttling enzyme carnitine palmitoyl-transferase 1A (CPT1A) in TECs. Cpt1a-knockin (CPT1A-KI) mice subjected to 3 models of renal fibrosis (unilateral ureteral obstruction, folic acid nephropathy [FAN], and adenine-induced nephrotoxicity) exhibited decreased expression of fibrotic markers, a blunted proinflammatory response, and reduced epithelial cell damage and macrophage influx. Protection from fibrosis was also observed when Cpt1a overexpression was induced after FAN. FAO-GOF restored oxidative metabolism and mitochondrial number and enhanced bioenergetics, increasing palmitate oxidation and ATP levels, changes that were also recapitulated in TECs exposed to profibrotic stimuli. Studies in patients showed decreased CPT1 levels and increased accumulation of short- and middle-chain acylcarnitines, reflecting impaired FAO in human CKD. We propose that strategies based on FAO-GOF may constitute powerful alternatives to combat fibrosis inherent to CKD.

Authors

Verónica Miguel, Jessica Tituaña, J. Ignacio Herrero, Laura Herrero, Dolors Serra, Paula Cuevas, Coral Barbas, Diego Rodríguez Puyol, Laura Márquez-Expósito, Marta Ruiz-Ortega, Carolina Castillo, Xin Sheng, Katalin Susztak, Miguel Ruiz-Canela, Jordi Salas-Salvadó, Miguel A. Martínez González, Sagrario Ortega, Ricardo Ramos, Santiago Lamas

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Figure 5

Overexpression of CPT1A reduces M1 macrophage infiltration in the FAN model.

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Overexpression of CPT1A reduces M1 macrophage infiltration in the FAN mo...
(A) Representative micrographs of 1 mouse per group showing the expression of F4/80 in kidney sections of mice treated as described above. Scale bar: 50 μm. (B) Bar graph represents the quantification of the percentage of F4/80+ stained area in FA-treated mouse kidneys (FAN). Bar graphs represent the mean ± SEM, n = 4 mice. (C) Representative multiparameter flow cytometry dot plots showing the expression of CD45 and F4/80 in kidney cells from WT and Pax8-CPT1A mice subjected to FAN after doxycycline induction (upper panels) (1 mouse per group is represented). CD86 and CD206 were used to determine the proportion of M1 and M2 macrophage subpopulations, respectively, in the total macrophage population (F4/80+, CD45+) (lower panels). Numbers in quadrants indicate cell proportions in percentage of cells that express both markers. (D) Bar graph represents the percentage of kidney cells expressing CD86 (M1), CD206 (M2), or both (M1/M2) markers. Data represent mean ± SEM (n = 4 mice). ***P < 0.001 compared with M1 subpopulation in damaged kidneys from WT mice; #P < 0.05 compared with corresponding cell subpopulation in damaged kidneys from WT mice. (E) mRNA levels of inflammation-associated genes were determined by qRT-PCR using TaqMan qPCR probes in kidneys from control (CT) and FA-treated (FAN) WT and Pax8-CPT1A mice after doxycycline induction. Bar graphs represent the mean ± SEM of fold changes (n = 6 mice). *P < 0.05, **P < 0.01 compared with their corresponding CT kidneys; #P < 0.05 compared with kidneys from WT mice with the same experimental condition. Statistical significance between 2 independent groups was determined using nonparametric 2-tailed Mann-Whitney U test; more than 2 groups were compared with Kruskal-Wallis test. For detailed gene nomenclature, see Supplemental Table 4.