Impact of Glucose Loading on Variations in CD4+ and CD8+ T Cells in Japanese Participants with or without Type 2 Diabetes

Objective: The aim of this study was to examine the fluctuations in CD4(+) T cells, CD8(+) T cells, and natural CD4(+)CD25(+)FoxP3(+) T-regulatory (Treg) cells following an oral glucose tolerance test (OGTT) in participants with and those without type 2 diabetes (T2DM). Methods: 19 Japanese participants with T2DM (DM group) and 21 participants without diabetes (non-DM group) were recruited and underwent a 75-g OGTT. The cell numbers of leukocytes, lymphocytes, and the T cell compartment, such as CD4(+), CD8(+), and Treg, were calculated for blood samples obtained after an overnight 12 h fast and during a 75-g OGTT at 60 and 120 min. Results: Before glucose loading, no differences in the cell numbers of leukocytes, lymphocytes, CD4(+), CD8(+), and Treg were observed between the DM group and the non-DM group. The proportion of CD8(+) was significantly reduced, whereas the proportion of CD4(+) was significantly increased, after 120 min of glucose loading in both groups. The proportion of Treg was not affected. Furthermore, a significant positive correlation was observed between the AUC(0-120 min) of CD8(+) and the change in the free fatty acid level following the OGTT (rho = 0.39, P < 0.05), but not that of glucose or insulin. Conclusion: The proportion of CD4(+) T cells was increased and that of CD8(+) T cells was reduced after glucose loading in both subjects with and without diabetes. These findings suggest that glucose loading dynamically affects the balance of the circulating T lymphocyte subset, regardless of glucose tolerance.