Changes of Regulatory T Cells and of Proinflammatory and Immunosuppressive Cytokines in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Abstract EN

Objective.

The aim of this study was to investigate the changes of regulatory T cells (Treg), interleukin-6 (IL-6), IL-10, transforming growth factor-β (TGF-β), and tumor necrosis factor-alpha (TNF-α) in patients with type 2 diabetes mellitus (T2DM).

Methods.

We performed a comprehensive search up to July 2016 for all clinical studies about the changes of Treg, IL-6, IL-10, IL-17, TGF-β, and TNF-α in T2DM patients versus healthy controls.

Results.

A total of 91 articles (5642 cases and 7378 controls) were included for this meta-analysis.

Compared with the controls (all p<0.001), the patients had increased serum levels of IL-6, TGF-β, and TNF-α but decreased the percentage of peripheral CD4+CD25+Foxp3+Treg and serum IL-10 level.

Furthermore, the percentage of peripheral CD4+CD25+Foxp3+Treg (p<0.001) and serum IL-10 level (p=0.033) were significantly lower in the patients with complication and in the patients without complication, respectively.

No significant changes about the percentage of CD4+CD25+Treg (p=0.360) and serum IL-17 level (p=0.459) were found in T2DM patients.

Conclusions.

T2DM patients have decreased the percentage of peripheral CD4+CD25+Foxp3+Treg and levels of serum IL-10 but elevated serum levels of IL-6, TGF-β, and TNF-α.

Presence of diabetic complications further lowers the peripheral CD4+CD25+Foxp3+Treg number.