Oxidative Stress Response Pathways in Animal Models of Impaired Proximal Kidney Tubule Phosphate Transport

Introduction: We have previously published studies suggesting that kidney cortex of animals with deficiency of the Na-H Exchanger Regulatory Factor 1 (NHERF1) shows increased activity of the pentose phosphate pathway and a lower ratio of reduced/oxidized glutathione compared to wild type mouse kidney cortex, suggesting the presence of oxidative stress. Because NHERF1 knock out animals are phosphaturic due to diminished proximal tubule apical membrane expression of the type IIa sodium phosphate cotransproter (Npt2a), we hypothesized that diminished Npt2a-mediated phosphate transport produces oxidative stress in proximal tubule, leading to activation of oxidative stress pathways. Methods: We performed targeted metabolomics on kidney cortex of 3 models of hypophosphatemia in C57Bl6 mice: 1) conditional proximal tubule specific NHERF1 knock out mice, 2) conditional proximal tubule specific Npt2a knock out mice, and 3) wild type mice on a low phosphate diet (2 weeks, 0.02%) with wild type mice on normal diet as controls. We analyzed the results with Metaboanalyst 6.0, identifying differentially expressed metabolites of interest as those with p value < 0.05 or greater than 2-fold difference in expression. We compared metabolomic profiles using principal component analysis and Sparse AutoEncoder Neural Network analysis. Pathway analysis was performed using STRING and KEGG programs. Results: All conditions of low phosphate uptake resulted in significant changes in the metabolomic profile of kidney cortex when compared to WT. Analysis revealed pathways common to all three low phosphate conditions including the pentose phosphate pathway and purine metabolism; however, the specific metabolites linked to these pathways and the relative contribution of these pathways differed between conditions. Comparison of the metabolomic profiles and pathway analysis in the proximal tubule specific NHERF1 KO vs WT and the low vs normal phosphate diet showed substantial differences. Moreover, the relative abundance of specific metabolites and the relative impact of specific pathways on the metabolic profiles showed substantial gender differences under basal and experimental conditions. Metabolomic profiles of male mice under low phosphate conditions compared to wild type conditions showed significant alterations in glucose metabolism and the Warburg Effect, while the profiles of female mice showed evidence of alterations in glutathione metabolism, methionine metabolism and homocysteine metabolism. Male-female differences were least under low dietary phosphate condition. Conclusions: 1. Phosphate deficiency results in substantial changes in the metabolomic profile 2. Metabolic changes resulting from transporter deficiency differ significantly from those of low phosphate diet suggesting a contribution of transporter specific phosphate transport on metabolism. 3. Our findings suggest that male and female mouse kidney cortex exhibit differential metabolic responses to phosphate deficiency stress, likely representing oxidative stress. Kidney cortex of male mice showing increased reliance on glucose metabolism while females upregulate glutathione production. Whether the gender differences in metabolic responses to phosphate deficiency reflect different degrees of.oxidative stress or intrinsic differences in kidney cortex metabolism remains to be determined. 4. These findings may suggest the need for gender specific therapies for kidney insults. Dept Veterans Affairs CX0001614 NIH NORC grant to UTSW Metabolic Phenotyping Core This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.