Downregulated microRNA-155 expression in peripheral blood mononuclear cells of type 2 diabetic patients is not correlated with increased inflammatory cytokine production

• Aberrant expression of miR-155 has been linked to multiple inflammatory diseases.
• Role of miR-155 in inflammatory responses of the diabetic patients remains unknown.
• LPS upregulates miR-155 expression in PBMCs of both control and diabetic groups.
• In basal state, miR-155 is downregulated in PBMCs of the diabetic patients.
• miR-155 has not a role in increased cytokine production from PBMCs of diabetic patients.

Objectives: The role of miR-155 in immune responses of PBMCs of type 2 diabetic (T2D) patients has not been studied. Design and methods: 20 Healthy and 20 T2D subjects were participated in the study. miR-155 expression in PBMCs of the subjects was measured using real-time PCR. The levels of secreted IL-6 and TNF-α cytokines were quantified using ELISA. Results: A downregulation of miR-155 expression was observed in untreated and LPS treated PBMCs of diabetic patients compared to controls. There was a significant upregulation of miR-155 after LPS treatment in PBMCs of both control and diabetic groups. In healthy subjects and in both untreated and LPS-treated conditions, miR-155 expression was negatively correlated with weight, waist circumference and body mass index. In diabetic group, there was a negative correlation between miR-155 expression and glucose levels only in LPS treated cells. Furthermore, systolic blood pressure was found to negatively correlate with miR-155 expression in untreated PBMCs of both healthy and diabetic subjects. The results also showed a significant correlation between miR-155 expression and TNF-α and IL-6 levels in LPS treated cells. Conclusions: Our data demonstrate that miR-155 expression is reduced in PBMCs of diabetic patients and this reduced expression does not seem to be involved in increased cytokine production from PBMCs of these patients.