Higher triglyceride-glucose index is associated with severe proteinuria and decreased renal function in patients with primary membranous nephropathy

Background: In recent years, the triglyceride-glucose (TyG) index has emerged as a reliable surrogate marker of insulin resistance (IR). This study aimed to investigate the association between the TyG index and severe proteinuria or decreased renal function in patients with primary membranous nephropathy (PMN). Methods: We consecutively enrolled 536 patients with PMN hospitalized at Peking University Third Hospital from January, 2014 to December, 2023. The TyG index was calculated as Ln[fasting triglyceride (mg/dL)xfasting blood glucose (mg/dL)/2]. All participants were categorized into quantiles according to the TyG index. Severe proteinuria was defined as 24 h urine protein > 3.5 g/d, and decreased renal function was defined as the estimated glomerular filtration rate < 90 mL/min/1.73m(2). Multivariable logistic regression, restricted cubic spline (RCS) curves, and receiver operating characteristic (ROC) curves were used for analysis. Results: Among 536 patients with PMN, 355 patients had severe proteinuria and 149 patients had decreased renal function. The levels of TyG index was significantly elevated in PMN patients with severe proteinuria or decreased renal function. The RCS analysis revealed a positive linear relationship of the TyG index with the risk of severe proteinuria (P for non-linear = 0.317) or decreased renal function (P for non-linear = 0.199) in patients with PMN. Using the lowest quantile as the reference, multivariate-adjusted logistic regression indicated that patients in the highest quantile of the TyG index had a significantly increased risk of severe proteinuria [odds ratio (OR) = 2.08, 95% confidence interval (CI): 1.44-3.01, P < 0.001] and decreased renal function (OR = 1.57, 95% CI: 1.04-2.36, P = 0.032). The area under the ROC curve (AUC) of the TyG index is 0.613 (95% CI: 0.564-0.662) for severe proteinuria and 0.590 (95% CI: 0.536-0.643) for decreased renal function. Conclusion: Our findings indicated that the TyG index has a positive linear correlation with severe proteinuria or decreased renal function in patients with PMN.