Vitamin C supplementation reconstitutes polyfunctional T cells in streptozotocin-induced diabetic rats.

Background: Studies have demonstrated that vitamin C supplementation enhances the immune system, prevents DNA damage, and decreases the risk of a wide range of diseases. Other study reported that leukocyte vitamin C level was low in diabetic individuals compared with nondiabetic controls. Aim of the work: To study the effect of vitamin C on oxidative stress, blood lipid profile, and T-cell responsiveness during streptozotocin (STZ)-induced type I diabetes mellitus. Methods: Thirty male Sprague-Dawley rats were randomly split into three groups. The first served as a control group ( n = 10) in which rats were injected with the vehicle alone. The second ( n = 10) and the third groups ( n = 10) were rendered diabetic by intraperitoneal (i.p.) injection of single doses of STZ (60 mg/kg body weight). The third group was supplemented with vitamin C (100 mg/kg body weight) for 2 months. Results: T lymphocytes from the diabetic rats were found to be in a stunned state, with a decreased surface expression of the CD28 costimulatory molecule, low levels of phosphorylated AKT, altered actin polymerization, diminished proliferation and cytokine production, and, eventually, a marked decrease in abundance in the periphery. Vitamin C was found to significantly decrease the elevated levels of blood hydroperoxide, glucose, cholesterol, triglycerides and low-density lipoprotein (LDL) in diabetic rats. Furthermore, it was found to restore CD28 expression, AKT phosphorylation, actin polymerization, and polyfunctional T cells (IFN-γ- and IL-2-producing cells that exhibit a high proliferation capacity). Conclusion: Vitamin C treatment restores and reconstitutes polyfunctional, long-lived T cells in diabetic rats. [ABSTRACT FROM AUTHOR]