This study is NOT currently recruiting participants.
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 During the two sampling periods, samples will be withdrawn via venous catheter for RBC deformability, vitamin C concentrations and other related research studies.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 concentrations before and after supplementation. In this manner, each participant serves as his/her own control, and deformability of red blood cells can be determined in relation to glycemia and to vitamin C concentrations in RBCs and plasma.
INCLUSION CRITERIA:
Study Initiation
-Male or female 18-65 years old, able to give informed consent.
-Diabetes type 2 HgA1C <= 12% on insulin and/or oral hypoglycemic agents or nondiabetic without any prior history or diagnosis of diabetes.
-In general good health with no other significant illness.
-Mild concomitant disease such as mild hypothyroidism (TSH <10) is acceptable.
-Blood pressure with or without medication <160/90 mmHg with no known significant target organ damage (end organ damage includes the following: proliferative retinopathy, serum creatinine >1.5 or EGFR < 55 mL/min, symptomatic ischemic heart disease, severe congestive heart failure, advanced peripheral vascular disease.
-Willingness to use effective contraceptive methods such as barrier method for the duration of study (female subjects).
8-week follow-up
Above criteria with addition of RBC vitamin C concentration >30 uM prior to inpatient studies.
EXCLUSION CRITERIA:
Entire duration of study
-Diabetic type 1 subjects will be excluded due to the possibility of ketosis and hemodynamic instability with lack of insulin.
-Any subjective or objective evidence of microangiopathy such as history of claudication, symptomatic peripheral vascular disease, symptomatic coronary artery disease, stroke, retinopathy, nephropathy (serum creatinine >1.5 or EGFR < 55 mL/min).
-Diabetic subjects with retinopathy to avoid accelerated retinopathy with hyperglycemia.
-Concomitant disease such as severe heart failure, severe liver disease (transaminases > 3 times normal), or severe systemic disease of any sort.
-Pregnancy, breastfeeding.
-History of diabetic ketoacidosis or hyperosmolar coma.
-Subjects with clear evidence of non-compliance with protocol/study instructions.
-Subjects who are unwilling or lack capacity to provide informed consent.