Reduced GFR and albuminuria in Chinese type 2 diabetes mellitus patients are both independently associated with activation of the TNF-α system

Abstract

Aims/hypothesis: The involvement of chronic inflammation in albuminuria and renal function was investigated in a cross-sectional study of 320 type 2 diabetic Chinese patients from the Singapore Diabetes Cohort Study. Methods: Plasma levels of TNF-α and its two cellular receptors and of IL-6 and C-reactive protein (CRP) were measured. A composite TNF-α score was extracted using principal component analysis. Multiple linear regression analysis was implemented to evaluate the relationship between log e (ln) albumin:creatinine ratio (ACR) and estimated GFR (eGFR) with the inflammatory variables and other clinical covariates. A Bonferroni correction was applied based on the total number of variables entered into regression analyses. Results: ln ACR was significantly associated with TNF-α score independently of eGFR even after a Bonferroni correction. TNF-α score was also significantly associated with eGFR independently of ln ACR even after correction for multiple testing. These findings were similar when the individual molecules of the TNF-α system were analysed separately instead of using the composite TNF-α score. No association was observed for IL-6 and CRP with either renal trait. Diabetes duration was a significant predictor for ln ACR but not eGFR. Conversely, age was significantly associated with eGFR but not ln ACR. Conclusions/interpretation: Activation of the TNF-α system may potentially exert independent effects on ln ACR and eGFR in type 2 diabetes. Because of the study design, one may also consider the possibility that changes in these renal traits may conversely be responsible for such an inflammatory response. © 2008 Springer-Verlag.