Urinary SIRT2 Reflects Kidney Injury in Type 2 Diabetes.

Abstract

The early diagnosis of kidney injury in type 2 diabetes (T2DM) is important to prevent the long-term damaging effects of kidney loss and is decisive for patient outcomes. While SIRT2 is implicated in diabetes pathogenesis, its correlation with diabetic nephropathy remains unexplored. This study was designed to evaluate the association of circulating and urine SIRT2 levels with diabetic kidney injury, as well as potential underlying mechanisms. In T2DM patients, db/db mice, and high-glucose plus palmitic acid treated HK-2 cell models, ELISA, immunoturbidimetry, immunohistochemistry, western blot and RT-qPCR were used to detect SIRT2 levels and kidneys damage. According to urinary albumin/creatinine ratio (UACR), 163 T2DM patients were divided into three groups. Spearman correlation analysis was used to investigate the relationship between urinary sirtuin2/creatinine ratio (USCR) and biomarkers of kidney injury. The influencing factors of proteinuria in T2DM patients were analyzed by Logistic regression model. In our findings, the Macro group exhibited the highest USCR levels as UACR increased. There was a positive association between USCR and UACR, α1-microglobulin/creatinine ratio (UαCR), β2-microglobulin/creatinine ratio (UβCR), and retinol-binding protein/creatinine ratio (URCR), with a negative correlation observed with eGFR. Logistic ordered multiclassification regression analysis, adjusting for confounding variables, confirmed that USCR remained a significant risk factor for the severity of proteinuria in T2DM patients. In the kidney tissue of db/db mice, increased KIM-1 levels were associated with increased SIRT2 levels. Increased SIRT2 protein levels were also observed in renal tubular epithelial cells treated with high-glucose plus palmitic acid. Moreover, SIRT2 promotes the expression of pro-inflammatory factors TNF-α and IL-6 by modulating the phosphorylation of p38 MAPK and pJNK in renal tubular cells induced by high glucose and palmitic acid. Urinary SIRT2 is closely related to eGFR, renal tubule injury and urinary albumin excretion in T2DM patients, which is expected to be an important indicator to comprehensively reflect renal injury.