DHA-Triacylglycerol Accumulation in Tacrolimus-Induced Nephrotoxicity Identified by Lipidomic Profiling

Abstract

Tacrolimus (TAC)-induced chronic nephrotoxicity (TAC nephrotoxicity) remains a major contributor to late allograft dysfunction in kidney transplant recipients. Although detailed mechanisms remain incompletely understood, our previous metabolomic studies revealed disruptions in carnitine-related and redox pathways, suggesting impaired mitochondrial β-oxidation of fatty acids. To further characterize metabolic alterations associated with this condition, we conducted an untargeted lipidomic analysis of renal tissues using a murine model of TAC nephrotoxicity. TAC (1 mg/kg/day) or saline was subcutaneously administered to male ICR mice for 28 days, and kidney tissues were harvested for comprehensive lipidomic profiling. Lipidomic analysis was performed with liquid chromatography-tandem mass spectrometry (p < 0.05, n = 5/group). Triacylglycerols (TGs) were the predominant lipid class identified. TAC-treated mice exhibited reduced levels of unsaturated TG species with low carbon numbers, whereas TGs with higher carbon numbers and various degrees of unsaturation were increased. All detected TGs containing docosahexaenoic acid (DHA) showed an increasing trend in TAC-treated kidneys. Although accumulation of polyunsaturated TGs has been previously observed in chronic kidney disease, the preferential increase in DHA-containing TGs appears to be a unique feature of TAC-induced nephrotoxicity. These results suggest that DHA-enriched TGs may serve as a metabolic signature of TAC nephrotoxicity and offer new insights into its pathophysiology.

Keywords: calcineurin inhibitor; docosahexaenoic acid; lipidomics; renal injury; tacrolimus; triacylglycerol profiling.

Figure 1

Overview of detected metabolites and distribution of triacylglycerols (TGs). (A) We identified 519 lipid metabolites. The number in parentheses following each lipid class indicates the number of detected metabolites in that class. TGs comprised the predominant class (139 species) (n = 5/group). (B) Volcano plot of TGs showing the log2 fold change (TAC group/control group) on the x-axis and the –log10 p-value on the y-axis. Each green dot represents an individual TG species. The two vertical dotted lines indicate −1 and 1 for Log2 Fold change, respectively. The horizontal dotted line indicates a p-value of 0.05. Abbreviations: Cer: ceramide; Cl: cardiolipin; DG: diacylglycerol; LPG: lysophosphatidylglycerol; PC: phosphatidylcholine; PE: phosphatidylethanolamine; PG: phosphatidylglycerol; PS: phosphatidylserine; SM: sphingomyelin; Pl: phosphatidylinositol; TG: triacylglycerol.

Figure 2

Heatmaps of triacylglycerol (TG) profiles categorized by carbon numbers and numbers of double bonds. (A) Relative abundance of TG species based on carbon number and unsaturation. (B) Ether-linked TG species analyzed separately due to overlapping classification. The yellow background color in this figure represents the TG blank. Red indicates an increase (TAC/Control ratio > 1), and blue indicates a decrease (TAC/Control ratio < 1). The x-axis shows the total carbon number. The y-axis shows the number of double bonds. The ratio was calculated as follows: the relative ratio = average relative areas of the TAC group/average relative areas of the control group (* p < 0.05). TG, triacylglycerol; O-TG, ether-linked triacylglycerol.

Figure 3

Volcano plots of TGs containing representative PUFAs. (A) TGs containing linoleic acid (C18:2); (B) linolenic acid (C18:3); (C) docosahexaenoic acid (DHA, C22:6); (D) docosapentaenoic acid (DPA, C22:5). Gray dots represent all TGs; red dots indicate TGs containing the specified PUFA. The x-axis shows the log2 fold change (TAC/Control); the y-axis shows the −log10 p-value. The two vertical dotted lines indicate −1 and 1 for Log2 Fold change, respectively. The horizontal dotted line indicates a p-value of 0.05. TG; triacylglycerol, PUFA; polyunsaturated fatty acid, C18:2; linoleic acid, C18:3; linolenic acid, C22:5; DPA, C22:6; DHA.