Famine From Feast: Linking Vitamin C, Red Blood Cell Fragility, and Diabetes

An unexpected means to prevent microvascular disease in diabetes may be coupled to the function of vitamin C in red blood cells (RBCs) of diabetic participants. Based on new and emerging data, vitamin C concentrations in RBCs may be inversely related to glucose concentrations found in diabetes. In this protocol, we will investigate physiology of vitamin C in RBCs of diabetic participants as a function of glycemia, without vitamin C supplementation (baseline) and with vitamin C supplementation (8-week follow-up). As inpatients, participants will have two venous sampling periods each of approximately 24 hours. Insulin doses will be clinically determined and titrated to achieve euglycemia (fasting and pre-meal glucoses \<140mg/dl) prior to the first sampling period (euglycemic sampling). During the two sampling periods, samples will be withdrawn via venous catheter for RBC deformability, vitamin C concentrations and other related research studies. Following baseline measurements, participants will be provided a prescription for vitamin C 500mg twice daily. Given that vitamin C and vitamin E are related antioxidants, and that both vitamins appear to be associated with RBC rigidity, diabetic participants may also be given a prescription for 400 international units (IU) of vitamin E (RRR alpha tocopherol) daily. Participants will continue vitamin C and E supplementation for a minimum of 8 weeks depending on RBC vitamin C concentrations. To evaluate any effect of vitamin E supplementation, plasma and RBC vitamin E levels may be measured concurrently with vitamin C levels, after baseline. All participants will be seen as outpatients at biweekly or monthly intervals with regular measurement of plasma and RBC vitamin C concentrations. Vitamins C and E supplementation will be discontinued upon inpatient admission at the 8-week follow-up period. Risk of both vitamin supplements are minimal as both supplementation doses are safe. Outcomes are to measure RBC rigidity and vitamin