Changes of regulatory T cells, transforming growth factor-beta and interleukin-10 in patients with type 1 diabetes mellitus: A systematic review and meta-analysis

•Peripheral Tregs are significant low in T1DM versus healthy controls.•Levels of serum TGF-β in T1DM are significant reduced versus healthy controls.•Changes about IL-10 levels in T1DM serum are not significant.

Regulatory T lymphocyte cells (Treg) associated with interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) have implicated in the development of type 1 diabetes mellitus (T1DM), yet the existing evidence remains unclear. Hereby we performed a systematic review and meta-analysis to characterize the changes in T1DM patients. A total of 1407 T1DM patients and 1373 healthy controls from 40 case-control studies were eventually included in the pooling analysis. Compared with the controls, T1DM patients had decreased frequency of CD4+ CD25+ Treg (p = 0.0003), CD4+ CD25+ Foxp3+ Treg (p = 0.020), and the level of TGF-β (p = 0.030). Decrease in IL-10 (p = 0.14) was not significant. All the changes remained significant when the studies with low NOS scores and publication bias were excluded. In conclusion, peripheral Treg and serum TGF-β are reduced in type 1 diabetes mellitus whereas changes in serum IL-10 are not significant.