High-fat diet promotes lipotoxicity in the podocytes of uninephrectomized mice: A targeted lipidomics and kidney podocyte-specific analysis

Abnormal lipid metabolism is an independent risk factor of renal injury. Moreover, in cases of a single kidney, abnormal lipid metabolism significantly alters the expression of genes associated with renal injury.Using targeted lipidomics analysis and podocyte-specific assays, the modification of lipid profiles attributed to high-fat diet and the development of podocyte injury caused by lipid metabolism in mice who underwent unilateral nephrectomy were examined.Mice who underwent unilateral nephrectomy and who were fed with a high-fat diet for 13 weeks exhibited progressive renal dysfunction, including the expression of lipid droplets in podocytes, vacuolization of tubular cells, and glomerular hypertrophy. Liquid chromatography-triple quadrupole mass spectrometry confirmed a significant increase in cholesteryl ester 20:4 levels in the podocytes of mice who underwent uninephrectomy and who were fed with a high-fat diet. In vitro, cholesteryl ester 20:4 treatment decreased mitochondrial respiration capacity and mitochondrial glycolysis in podocytes. Further, it changed the expression of proteins including ATP Binding Cassette Subfamily A Member 1, carnitine palmitoyltransferase 1A, acyl-CoA cholesterol acyltransferase, nuclear respiratory factor 1/2, dynamin-1-like protein, and p62, which are associated with lipid metabolism and transport, mitochondrial activity, and autophagy. Impaired function in podocytes and altered gene expression on transcriptome sequencing analysis were associated with the progression of renal fibrosis in unilateral nephrectomy mice with a high-fat diet. Increased expression of matrix metalloproteinases and collagen genes was related to the progression of renal fibrosis in mice that underwent unilateral nephrectomy and were fed a high-fat diet. In addition, fibrosis protein markers such as fibronectin and collagen IV were identified.In conclusion, a high-fat diet induces lipid accumulation in a unilateral nephrectomy model. That is, increased cholesteryl ester 20:4 levels in podocytes can induce mitochondrial damage and abnormal autophagy, thereby possibly leading to structural and functional deterioration in the kidney.