Expression of CD4+CD25+Foxp3+ Regulatory T Cells, Interleukin 10 and Transforming Growth Factor β in Newly Diagnosed Type 2 Diabetic Patients.

BACKGROUND: Recent studies have shown that dysfunction and decrease of regulatory T cells (Tregs) correlates with insulin resistance (IR), one of the most significant mechanisms for type 2 diabetes mellitus (T2DM). To examine potential relationships among Tregs, IR, blood lipid content, and related cytokines, we investigated the frequency of CD4+CD25+Foxp3+ Tregs, as well as expression levels of interleukin 10 (IL-10) and transforming growth factor-β (TGF-β) in newly diagnosed T2DM patients.

METHODS: Fifty-one newly diagnosed T2DM patients and 55 control individuals were enrolled. According to body mass index (BMI), the T2DM patients were grouped into non-obese and obese groups. Blood was collected in ethylene diamine tetraacetic acid (EDTA) anticoagulant tubes for detection of CD4+CD25+Foxp3+ Tregs by flow cytometry. Serum was collected to quantify IL-10 and TGF-β levels by enzyme-linked immunosorbent assay (ELISA). By comparing percentages of Tregs between non-obese and obese groups, correlation with Treg frequency, homeostasis model assessment of insulin resistance (HOMA-IR), IL-10 and TGF-β was examined.

RESULTS: The percentage of CD4+CD25+Foxp3+ Tregs in the newly diagnosed T2DM group was significantly lower than in the control group (P<0.01). Further, levels of IL-10 and TGF-β were also lower in the T2DM group (P<0.05). The level of IL-10 was remarkably lower in the obese group than in the non-obese and the control groups (P<0.01), but there was no significant difference between non-obese group and the control group. The level of TGF-β was lower in obese group than in the control group (P<0.05). There was no significant difference between non-obese group and the control group. The frequency of CD4+CD25+Foxp3+ Tregs in the obese group was significantly lower than in the non-obese group (P<0.05). In the obese group, the percentage of Tregs negatively correlated with HOMA-IR and positively correlated with TGF-β (P<0.05). There was no obvious correlation between Treg and HOMA-IR in the non-obese group.

CONCLUSION: The percentage of CD4+CD25+Foxp3+ Tregs and levels of related cytokines IL-10 and TGF-β were precipitously decreased in newly diagnosed T2DM patients. Therefore, the function of Tregs in limiting the proinflammatory milieu represents an important pathogenic mediator of the development of obesity-induced IR in newly diagnosed T2DM patients. Notably, TGF-β may play an important role in this process. Thus, enhancing expression of Tregs may improve IR in newly diagnosed T2DM patients with obesity.