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 4

CPT1A overexpression prevents TGF-β1–induced FAO impairment.

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CPT1A overexpression prevents TGF-β1–induced FAO impairment. (A) Bright ...
(A) Bright field or GFP immunofluorescence images of primary kidney epithelial cells (TECs) isolated from kidneys of WT and Pax8-CPT1A mice. Scale bar: 20 μm. (B) Oxygen consumption rate (OCR) of TECs from WT mice was measured with a Seahorse XF24 Extracellular Flux Analyzer. Where indicated, cells were pretreated with palmitate-BSA FAO substrate (200 μM) or the CPT1 inhibitor etomoxir (Eto, 400 μM). Oligomycin (1 μM), FCCP (3 μM), and a combination of antimycin A (1 μM) and rotenone (1 μM) (AA/Rot) were injected sequentially at the time points indicated. Each data point represents the mean ± SEM of 4 independent experiments, each performed in triplicate. (C) OCR of TECs from WT and Pax8-CPT1A mice was measured with a Seahorse XF24 Extracellular Flux Analyzer. Bar graphs (right panel) show the rates of OCR associated with basal, proton-leak, ATP-linked, maximum, reserve capacity, and nonmitochondrial respiratory statuses. *P < 0.05 compared with their corresponding control (CT) TECs; #P < 0.05 compared with TECs from WT mice with the same experimental condition. (D) Extracellular acidification rate (ECAR) of cells treated as in A. Each data point represents the mean ± SEM of 4 independent experiments, each performed in triplicate. (E) ATP levels of TECs from WT and Pax8-CPT1A mice. Bar graphs represent the mean ± SEM (n = 4 mice per group). #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 Kruskal-Wallis test.