Impact of interleukin-32α on T helper cell-related cytokines, transcription factors, and proliferation in patients with type 2 diabetes mellitus

Abstract

Objective

The ability of interleukin (IL)-32α to induce T helper (Th) 1, Th17, and Treg cytokines (interferon gamma [IFN-γ], IL-17, and IL-10, respectively), and transcription factors ([signal transducer and activator of transcription (STAT) 1 and T-box (T-bet) for Th1, STAT3 and retinoid-related orphan receptor (ROR)-γt for Th17, and STAT5 and forkhead box P3 (Foxp3) for Treg]) were investigated in type 2 diabetes mellitus (T2DM). IL-32α effects on Th cell proliferation and related factors including IL-2 and NF-κB were also explored.

Methods

Serum levels of IL-32α in 31 patients and 31 healthy controls (HCs) were determined by ELISA assay. CD4⁺ T cells cultured with polyclonal activators in the presence and absence of recombinant IL-32α (rIL-32α). Gene expressions in cultured Th cells were assessed with real-time PCR. Cytokines in supernatants were measured with ELISA. Proliferation experiments were assessed by flow cytometry.

Results

The patients showed significant increase in IL-32α levels compared with HCs and its levels were positively correlated with fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c). rIL-32α enhanced IL-17 and IL-2 production, increased ROR-γt and NF-κB expression, and enhanced Th proliferation in both patients and HCs. In patients, IL-17, ROR-γt, NF-κB, and proliferation levels were higher than those in HCs, in cultures with and without rIL-32α (rIL-32α⁺ and rIL-32α^-). IL-2 levels in rIL-32α⁺cultures of patients were significantly higher than the HCs, and it was positively correlated with proliferation rate and NF-κB expression.

Conclusions

Aberrant IL-32α levels are participated in T2DM pathogenesis. IL-32α potently induces Th17-related factors and amplifies the proliferative function of T cells.

Highlights

• Enhanced serum levels of IL-32α in T2DM patients was correlated with FPG and HbA1c.

• IL-32α increases ROR-γt expression and IL-17 production, and induces Th17 cells.

• IL-32α enhances NF-κB expression and IL-2 production, and promotes Th proliferation.

• IL-32α is more effective for inducing Th17 cells and proliferation in the patients.

• IL-32α axis could be mentioned as a future therapeutic goal for the T2DM.

Keywords:

• IL-32
• T cell
• proliferation
• STAT
• transcription factor
• type 2 diabetes mellitus

Acknowledgments

We are grateful to our participants and laboratory staff.

Author contributions

Sh. B. and M. B. carried out and analyzed the experiments. Sh. B. took care of the participants. M. B. and M. GH. H. conceptualized the project. M. GH. H. and M. B. prepared the paper. All authors have seen the final version of manuscript and approved it.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The study was funded by Vice-chancellor for Research and Technology, Hamadan University of Medical Sciences, Hamadan, Iran [no. 140008256998 to M. B.].