Exosomal miR-let-7c-5p is involved in the cognitive function of type 2 diabetes mellitus patients by interleukin 10: A cross-sectional study

Background: Interleukin (IL)-10 plays a notable role in the inflammatory-associated mild cognitive impairment (MCI). We aimed to investigate whether IL-10 and its upstream factors exert an impact on MCI in type 2 diabetes mellitus (T2DM) patients.

Methods: A total of 117 T2DM patients were recruited and divided into Control group and MCI group based on the presence or absence of MCI. Clinical parameters were collected. The Montreal Cognitive Assessment (MoCA) was conducted for global cognitive function. Digit Span Test (DST), Verbal Fluency Test (VFT), and Trail Making Test-B (TMTB) were used to evaluate the executive functions of the diabetic patients. Trail Making Test-A (TMTA) was performed to examine the information processing speed function. Patients' scene memory was examined by Logical Memory Test (LMT). After the baseline data were compared, correlation and regression analyses were performed to explore the relationship among IL-10, miR-let-7c-5p and cognitive function.

Results: Compared to 80 patients in the control group, 37 patients in the MCI group exhibited lower IL-10 in plasma and higher miR-let-7c-5p levels in exosomes from plasma. The IL-10 level was negatively associated with MoCA. Likewise, miR-let-7c-5p levels were negatively correlated with IL-10 levels and MoCA. Elevated miR-let-7c-5p levels and decreased IL-10 levels are risk factors for MCI in T2DM patients. Increased miR-let-7c-5p and downregulated IL-10 may influence VFT and TMTB, respectively, associated with executive function.

Conclusions: We demonstrated that IL-10 is correlated to the executive function of T2DM patients. Decreased IL-10 may result from the regulation of miR-let-7c-5p in exosomes.