Mucosal-associated invariant T cells in diabetes mellitus: Protective or destructive?

Diabetes mellitus (DM) is a chronic metabolic condition that can be categorized into two major subsets, type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Recently, studies in diabetic patients and animal models have demonstrated the dual role of mucosal-associated invariant T (MAIT) cells in the context of diabetes mellitus. MAIT cell populations are altered in T1DM, exhibiting a reduced frequency and exhausted profile characterized by reduced cytokine production. These alterations correlate with disease progression and may contribute to destruction of β-cells. Conversely, in T2DM, MAIT cells are often reduced and exhibit a pro-inflammatory phenotype related to obesity and insulin resistance. Understanding the precise role of MAIT cells in DM may provide insight into innovative therapeutic approaches aimed at modulating their function to enhance disease outcomes. This review highlights the characteristics, function and activation of MAIT cells. We also review the in vivo and in vitro studies on the role of MAIT cells in T1DM and T2DM. Finally, we focus on the therapeutic applications of these cells for the management of DM patients.