RRM2 attenuates the renal tubular ferroptosis in diabetic kidney disease through PI3K/Akt/Nrf2 pathway.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is associated with significant metabolic and renal complications, including diabetic nephropathy (DN). AIM: To investigate the role of ribonucleotide reductase regulatory subunit M2 (RRM2) in T2DM and its potential involvement in renal injury through oxidative stress, apoptosis, and ferroptosis. METHODS: A cross-sectional study was conducted, comprising 194 patients with T2DM and 120 healthy controls at our hospital between January 2022 and December 2023. The data were analyzed to ascertain the correlation between RRM2 levels and DN onset in patients with T2DM. The apoptosis rate, reactive oxygen species (ROS) levels, oxidative stress, cystine uptake, and ferrous ion (Fe(2+)) levels were quantified using the HK-2 cell lysates. Reverse transcription quantitative PCR and western blotting were used to assess mRNA and protein expression, respectively. RESULTS: Serum RRM2 levels were significantly higher in T2DM patients than in controls (P < 0.05) but declined in the macroalbuminuria subgroup. Receiver operating characteristic analysis identified 30 pg/mL as the optimal cut-off (area under the curve = 0.958; sensitivity = 86%; specificity = 95%). RRM2 was negatively correlated with age, diabetes duration, systolic blood pressure, fasting blood glucose, glycosylated hemoglobin, serum creatinine, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and malondialdehyde, and positively correlated with estimated glomerular filtration rate, glutathione (GSH), solute carrier family 7 member 11 (SLC7A11), and GSH peroxidase 4 (GPX4). Logistic regression confirmed RRM2 as an independent protective factor against DN [odds ratio (OR) = 0.820, 95% confidence interval (95%CI) = 0.712-0.945, P = 0.006]. In vitro, RRM2 overexpression enhanced HK-2 cell proliferation, activated PI3K/Akt signaling, and reduced apoptosis, ROS, oxidative stress, and ferroptosis, accompanied by the restoration of GSH, Nrf2, SLC7A11, and GPX4. These protective effects were abolished by PI3K/Akt inhibition, highlighting RRM2's renoprotective, pathway-dependent role. CONCLUSION: These findings suggest that RRM2 plays a crucial protective role against diabetic renal injury by mitigating oxidative stress, apoptosis, and ferroptosis via PI3K/Akt activation. Serum RRM2 may serve as a novel biomarker for early DN detection, and therapeutic strategies targeting RRM2 may offer potential benefits in preventing diabetic kidney disease progression.