Abstract：
Increased dietary phosphate consumption intensifies renal phosphate burden. Several mechanisms for phosphate-induced renal tubulointerstitial fibrosis have been reported. Considering the dual nature of phosphate as both a potential renal toxin and an essential nutrient for the body, kidneys may possess inherent protective mechanisms against phosphate overload, rather than succumbing solely to injury. However, there is limited understanding of such mechanisms. To identify these mechanisms, we conducted single-cell RNA sequencing (scRNA-seq) analysis of the kidneys of control and dietary phosphate-loaded (Phos) mice at a time point when the Phos group had not yet developed tubulointerstitial fibrosis. scRNA-seq analysis identified the highest number of differentially expressed genes in the clusters belonging to proximal tubular epithelial cells (PTECs). Based on these differentially expressed genes, in silico analyses suggested that the Phos group activated peroxisome proliferator-activated receptor-α (PPAR-α) and fatty acid β-oxidation (FAO) in the PTECs. This activation was further substantiated through various experiments, including the use of an FAO activity visualization probe. Compared with wild-type mice, Ppara knockout mice exhibited exacerbated tubulointerstitial fibrosis in response to phosphate overload. Experiments conducted with cultured PTECs demonstrated that activation of the PPAR-α/FAO pathway leads to improved cellular viability under high-phosphate conditions. The Phos group mice showed a decreased serum concentration of free fatty acids, which are endogenous PPAR-α agonists. Instead, experiments using cultured PTECs revealed that phosphate directly activates the PPAR-α/FAO pathway. These findings indicate that noncanonical metabolic reprogramming via endogenous activation of the PPAR-α/FAO pathway in PTECs is essential to counteract phosphate toxicity.NEW & NOTEWORTHY This study revealed the activation of peroxisome proliferator-activated receptor-α and fatty acid β-oxidation in proximal tubular epithelial cells as an endogenous mechanism to protect the kidney from phosphate toxicity. These findings highlight noncanonical metabolic reprogramming as a potential target for suppressing phosphate toxicity in the kidneys.
摘要：
饮食中磷酸盐消耗的增加加剧了肾脏磷酸盐负担。已经报道了磷酸盐诱导的肾小管间质纤维化的几种机制。考虑到磷酸盐的双重性质，既是一种潜在的肾毒素，也是人体必需的营养素，肾脏可能具有针对磷酸盐超负荷的固有保护机制，而不是仅仅屈服于伤害。然而,对这种机制的理解有限。为了确定这些机制，我们在Phos组尚未发生肾小管间质纤维化的时间点,对对照(Ctrl)和饮食磷酸盐负载(Phos)小鼠的肾脏进行了单细胞RNA测序(scRNA-seq)分析.scRNA-seq分析确定了属于近端肾小管上皮细胞（PTEC）的簇中差异表达基因（DEG）的数量最高。基于这些DEG,计算机模拟分析表明，Phos基团激活了PTEC中的过氧化物酶体增殖物激活受体α（PPAR-α）和脂肪酸β氧化（FAO）。通过各种实验进一步证实了这种激活，包括使用粮农组织活动可视化探针。与野生型小鼠相比，Ppara敲除小鼠对磷酸盐超负荷的反应表现出加剧的肾小管间质纤维化。用培养的PTEC进行的实验表明,PPAR-α/FAO途径的激活导致在高磷酸盐条件下改善的细胞活力。Phos组小鼠的血清游离脂肪酸浓度降低，它们是内源性PPAR-α激动剂。相反，使用培养的PTEC的实验表明，磷酸盐直接激活PPAR-α/FAO途径。这些发现表明，通过PTEC中PPAR-α/FAO途径的内源性激活进行的非规范代谢重编程对于抵消磷酸盐毒性至关重要。
