Renal tubule Cpt1a overexpression protects from kidney fibrosis by restoring mitochondrial homeostasis
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
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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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 3

CPT1A prevents impaired mitochondrial morphology and FAO defect in FAN-induced kidney fibrosis.

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CPT1A prevents impaired mitochondrial morphology and FAO defect in FAN-i...
(A) Representative electron microscopy images of cortical proximal tubules from control and Pax8-CPT1A mice subjected to FAN after doxycycline induction. Scale bars: 10 μm (upper panels), 100 nm (lower panels). (B) Mitochondrial DNA copy number (mtDNA) was determined in kidneys of WT and Pax8-CPT1A mice in the FAN model. Bar graphs represent the mean ± SEM of fold changes (n = 6 mice). **P < 0.01 compared with their corresponding control (CT) kidneys; ##P < 0.05 compared with kidneys from WT mice with the same experimental condition. (C) Radiolabeled palmitate-derived CO2 was determined after incubation of 14C-palmitate with kidney tissue from WT and Pax8-CPT1A mice in the FAN model after doxycycline induction. (D) ATP levels in total kidney tissue determined in mice subjected to FAN model. (C and D) Bar graphs represent the mean ± SEM (n = 4 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. (E and F) mRNA levels of glucose utilization–associated genes (E) and peroxisomal/mitochondrial function–associated genes (F) were determined by qRT-PCR using TaqMan qPCR probes in kidneys from CT and FA-treated (FAN) WT and Pax8-CPT1A mice after doxycycline induction. (E and F) 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, ##P < 0.01 compared with kidneys from WT mice with the same experimental condition. Statistical significance between 2 independent groups was determined using nonparametric 2-tailed Kruskal-Wallis test. For detailed gene nomenclature, see Supplemental Table 4.