Human CPT1A adenoviral particles

During chronic kidney disease (CKD), renal tubular epithelial cells (TECs) display a persistent inflammatory and profibrotic response. Fatty acid oxidation (FAO), the major energy source for TECs, is reduced in renal fibrosis and contributes to its pathogenesis. To determine whether FAO gain-of-function (FAO-GOF) could protect against fibrosis, researchers generated a conditional transgenic mouse model in which the fatty acid shuttle enzyme carnitine palmitoyltransferase 1A (CPT1A) was overexpressed in TECs. Cpt1a-knockin (CPT1A-KI) mice subjected to 3 models of renal fibrosis exhibited reduced expression of fibrotic markers, attenuated proinflammatory responses, and reduced epithelial cell damage and macrophage influx. Protection against fibrosis was also observed when Cpt1a overexpression was induced after FAN. FAO-GOF restored oxidative metabolism and mitochondrial number, enhanced bioenergetics, and increased palmitate oxidation and ATP levels, changes that were also recapitulated in TECs exposed to profibrotic stimuli. Studies in patients have shown reduced CPT1 levels and increased accumulation of short- and medium-chain acylcarnitines, reflecting impaired FAO in human CKD. Therefore, FAO-GOF-based strategies may be a powerful alternative to combat intrinsic fibrosis in CKD.

To confirm the metabolic functional consequences of CPT1A overexpression in a human setting, the researchers examined OCR and ECAR in the human renal tubular epithelial cell line HKC-8. Adenovirus carrying CPT1A (AdCPT1A) or adenovirus control (AdControl) as a negative control was used to infect HKC-8 cells. In HKC-8 cells expressing CPT1A, CPT1A protein levels were 4-fold higher than in control cells (Figure 1A and B). HKC-8 cells transduced with CPT1A exhibited reduced TGF-β1-induced FAO inhibition (Figure 1C) and inhibition of glycolysis, which was reflected in ECAR levels (Figure 1D). As expected, FAO rates were 2-fold higher in HKC-8 cells expressing AdCPT1A, which was confirmed by measuring ¹⁴C-palmitate-derived ¹⁴CO₂ (Figure 1E). Consistently, CPT1A overexpression increased the fluorescence resonance energy transfer (FRET) signal of a specific ATP sensor and promoted the reduced decay in the presence of TGF-β1 .

Figure 1. HKC-8 cells transduced with CPT1A exhibit reduced TGF-β1-induced FAO inhibition and fibrogenic transformation. (Miguel V, et al., 2021)