Abstract Body: Introduction: Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Most studies of DKD are glomerulo-centric. The recent progress in the control of renal glucose handling by SGLT2i makes the proximal tubule (PT) a prime candidate. Mitochondrial (mito) dysfunction and mito-induced oxidative stress in DKD is well-studied and is known to accelerate tubular injury. Some studies have suggested the role of the Atrial Natriuretic Peptide (ANP) in DKD. ANP is a hormone that regulates renal salt/water homeostasis and renal hemodynamics. We hypothesize that in DKD, ANP is a beneficial factor that improves proximal tubule mitochondrial function via protection from oxidative stress-induced ferroptosis.

Methods: Using male ANP knock-out (SS^NPPA-/-) and wild-type (SS^WT) rats on the Dahl SS background, T1DKD was induced by streptozotocin (STZ; 75mg/kg) at 9-10 weeks of age. Baseline, midpoint, and endpoint blood glucose, urine, and body weights were collected. Western blotting was done on isolated cortical tissue and tissue fibrosis was measured in PicroSirius Red staining. ANOVA through Origin 2019b was used for comparisons.

Results: STZ- SS^WT and STZ-SS^NPPA-/- groups exhibited similar body weight (231.7 ± 14.8 vs. 230.9 ± 8.4 g, respectively), two-kidney weight to body weight ratio (31.8 ± 0.9 vs. 28.4 ± 1.5 mg/g), and endpoint hyperglycemia (with blood glucose levels >650 mg/dL). Both, STZ- SS^WT and STZ-SS^NPPA-/- groups had high diuresis (59.9 ± 3.1 vs. 52.7 ± 3.2 mL/24hr/100gTBW). Histological analysis revealed elevated cortical fibrosis in the STZ-SS^NPPA-/- compared to STZ- SS^WT (4.6 ± 0.2 vs. 3.1 ± 0.2 % area, respectively, p<0.05). Moreover, in the kidney cortex, STZ-SS^NPPA-/- rats compared to STZ- SS^WT rats exhibit a significant increase in OXPHOS complexes IV and V (p<0.05) and a decrease in glutathione peroxidase 4 (GPX4; a core regulator of ferroptosis) abundance (1.5 ± 0.2 vs. 1.9 ± 0.1 a.u., respectively, p<0.05).

Conclusion: Data showed that lack of ANP may promote DKD-related tubulointerstitial fibrosis and suggested a relationship with renal cortical mitochondrial function. Future studies will provide mechanistic insight into the role of ANP in mito-related oxidative stress and further assess the role of ANP in PT ferroptosis.