3.5 Early kidney biomarkers of cisplatin-induced acute kidney injury
Hierarchical clustering revealed that the majority of significantly altered kidney metabolites were increased by cisplatin treatment, with 44/63 (69.8%) of metabolites being increased in C57BL/6 mice (Figure 3C ) and 50/73 (68.5%) metabolites increased in FVB/N mice (Figure S4C ). Creatine, p-cresol glucuronide, p-cresol sulfate, phenylacetylglycine, phenylalanine, and tryptophan were found to be elevated by cisplatin treatment in kidney tissue. Creatine showed significant elevation throughout all four timepoints in FVB/N mice, and similarly was also increased in C57BL/6 mice, though only significantly increased at days 2 and 3 (Figure 6A, S7A ). P-cresol glucuronide (Figure S7D ), p-cresol sulfate (Figure S7E ), and phenylacetylglycine (Figure S7F ) were all significantly elevated from day 2-4 in cisplatin-treated FVB/N kidneys. These metabolites followed a similar pattern in C57BL/6 mice but were significantly altered only at day 3 and 4 for p-cresol glucuronide and sulfate (Figure 6D, 6E ), and days 1 and 4 for phenylacetylglycine (Figure 6F ). Kidney levels of phenylalanine (Figure 6G , S7G ) and tryptophan (Figure 6J, S7J ) were also generally increased by cisplatin treatment, but only tryptophan in C57BL/6 mice was shown to be significantly increased in the early timepoints (Figure 6J ).
Equol 4-sulfate, LysoPC(20:3), proline betaine, and trigonelline were kidney metabolites identified to be decreased by cisplatin treatment. In kidneys from FVB/N mice, levels of equol 4-sulfate were significantly decreased following cisplatin treatment for all timepoints (Figure S7B ), and though equol 4-sulfate followed this decreasing trend in C57BL/6 kidneys, none of the changes were significant (Figure S7B ). Proline betaine was consistently altered by cisplatin treatment in both strains, being significantly decreased from days 2-4 (Figure 6H, S7H ). LysoPC(20:3) and trigonelline were also significantly decreased from days 2-4 in cisplatin-treated FVB/N mice (Figure S7C, S7I ). These metabolites exhibited similar trends in C57BL/6 kidneys, though they were only significantly altered on day 4 for both metabolites(Figure 6C, 6I ).