The role of phospholipid transfer protein in sepsis-associated acute kidney injury

Background Phospholipid transfer protein (PLTP), a glycoprotein widely expressed in the body, is primarily involved in plasma lipoprotein metabolism. Previous research has demonstrated that PLTP can exert anti-inflammatory effects and improve individual survival in patients with sepsis and endotoxemia by neutralizing LPS and facilitating LPS clearance. However, the role of PLTP in sepsis-associated acute kidney injury (SA-AKI) and the specific mechanism of its protective effects are unclear. This study aimed to assess the potential role of PLTP in SA-AKI. Methods This is a population-based prospective observational study of patients with sepsis admitted to the intensive care unit. Blood samples were collected on days 1, 3, 5, and 7 after admission to the ICU. Plasma PLTP lipotransfer activity was measured to assess outcomes, including the incidence of SA-AKI and 30-day major adverse kidney events (MAKE 30). The correlation between PLTP lipotransfer activity and SA-AKI and MAKE 30 was evaluated through logistic regression modeling. Receiver operating characteristic curves were used to assess the diagnostic value of PLTP lipotransfer activity for SA-AKI and MAKE 30. The PLTP lipotransfer activity was categorized into high and low groups based on the optimal cut-off values. The differences between the high and low PLTP lipotransfer activity groups in terms of MAKE 30 were evaluated using Kaplan-Meier analysis. The SA-AKI mouse model was established via cecum ligation and puncture (CLP) in the animal experimental phase. The impact of PLTP on renal function was then investigated in wild-type and PLTP +/- mice. The wild-type mice were given recombinant human PLTP (25 mu g, 200 mu L each/dose) via the tail vein at 1-, 7-, and 23-h intervals on the day preceding CLP. The control group received an equal volume of solvent. The 10-day survival and kidney function among the treatment groups were then evaluated. Results A total of 93 patients were enrolled in this clinical trial, of which 52 developed acute kidney injury (AKI). A total of 32 patients died over the course of the 30-day follow-up period, 34 underwent kidney replacement therapy, 37 developed persistent acute kidney injury, and 55 patients met the composite endpoint. The plasma PLTP lipotransfer activity was identified as an independent predictor of SA-AKI (crude OR = 0.96, 95% CI 0.95-0.98, p < 0.001; adjusted OR = 0.92, 95% CI 0.86-0.96, p = 0.001) and MAKE 30 (crude OR = 0.97, 95% CI 0.96-0.98, p < 0.001; adjusted OR = 0.96, 95% CI 0.93-0.98, p = 0.001). The area under the curve (AUC) of plasma PLTP lipotransfer activity within 24 h of ICU admission could predict the occurrence of SA-AKI and MAKE 30 in septic patients (AUC values; 0.87 (95% CI 0.79-0.94) and 0.87 (95% CI 0.80-0.94), respectively). The cumulative incidence of main kidney adverse events was significantly lower in the high group than in the low group (p < 0.001). Compared with the controls, creatinine levels were significantly elevated in the CLP mice, while PLTP lipotransfer activity was significantly decreased at 24 h postoperatively. Moreover, the PTLP +/- mice exhibited significantly impaired renal function and markedly elevated plasma levels of inflammatory mediators compared with the wild-type CLP mice. Notably, human recombinant PTLP significantly prolonged 10-day survival, improved renal function, and attenuated mitochondrial structural damage in wild-type CLP mice. Conclusions These findings indicate that PLTP is a potential therapeutic target in sepsis-associated acute kidney injury.