Serum TNF-α concentrations in type 2 diabetes mellitus patients and diabetic nephropathy patients: A systematic review and meta-analysis

•The TNF-α level had increased in T2DM and T2DN patients.•T2DM patients had significantly increased TNF-α level in eastern but not in western.•The TNF-α may be an important biomarker for diabetic nephropathy progression.

ObjectivesThe aim of this study was to investigate whether the concentrations of serum tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, increased in type 2 diabetes mellitus (T2DM) and type 2 diabetic nephropathy (T2DN) patients.MethodsThe four databases (PubMed, CNKI, WanFang and Chinese-Cqvip) were searched from Jan 1, 1999 to October 1, 2016 for all clinical case-control studies about the serum TNF-α concentrations in T2DM and T2DN patients. All relevant data were extracted from published reports. The meta-analysis was performed to compare the changes of serum TNF-α concentrations of T2DN and T2DM patients in Eastern and Western with healthy controls. We further evaluated concentrations of serum TNF-α in T2DN patients with mincroalbuminuria or macroalbuminuria. Random-effects models were adopted to assess the pooling data among various variations.ResultsIn total of 6 studies (744 patients and 277 healthy controls) were included in this study. Compared with healthy controls (both p < 0.01), the groups of different albuminuria levels and ethnicities both showed that the serum TNF-α levels were significantly elevated in T2DN patients as well as in eastern T2DN patients (p = 0.001), but not significant changed in western T2DN patients (p = 0.081). The results were stable through sensitivity analysis and no significant publications bias existed in this meta-analysis.ConclusionsSerum TNF-α concentrations are obviously increased in T2DN and T2DM patients, but higher in T2DN patients, suggesting an elevated inflammatory burden in T2DN patients.