Effects of sitagliptin and vitamin D3 on T helper cell transcription factors and cytokine production in clinical subgroups of type 2 diabetes mellitus: highlights upregulation of FOXP3 and IL-37

Objective: Gene expression level of T helper cell transcription factors and cytokines production in type-2 diabetes mellitus (T2DM) patients treated with mono- or combined sitagliptin and vitamin D3 (VitD3) were evaluated. Methods: Fifty-four nephropathic and 57 non-nephropathic T2DM patients were divided into the subgroups based on their treatment with/without sitagliptin and VitD3. The expression of T-bet, ROR gamma t, BCL6, and FOXP3 was evaluated using real-time PCR. The levels of IFN-gamma, IL-6, IL-17, IL-21, TGF-beta, and IL-37 were assessed in PBMC supernatants using ELISA. Results: The production of IFN-gamma and IL-17 was increased in untreated (without sitagliptin and VitD3) nephropathic and non-nephropathic T2DM patients compared with healthy controls, whereas FOXP3 expression was decreased. Treatment with sitagliptin alone or in combination with VitD3 reduced the production of IFN-gamma in the patients. Production of IL-17 and IL-21 and the expression of ROR gamma t and BCL6 was diminished in patients treated with combined sitagliptin and VitD3, whereas the production of IL-37 and FOXP3 expression were increased in the patients treated with sitagliptin or sitagliptin plus VitD3. Conclusion: These data demonstrate that sitagliptin in combination with VitD3 may accelerate the process of T2DM treatment by exerting synergic anti-inflammatory effects on immune system through upregulation of FOXP3 and IL-37, and downregulation of ROR gamma t and BCL6 as well as IFN-gamma, IL-17 and IL-21 production. Combined sitagliptin and VitD3 can be safely utilized to modulate the inflammatory conditions of T2DM.