Research News

Vitamin C May Help Prevent Long-Term Complications of Type 1 Diabetes

Diabetic Adolescents Who Received Vitamin C During Infusion Didn’t Experience Endothelial Impairment Caused by Hyperglycemia 

Vitamin C infusions may help prevent and restore endothelial impairment caused by hyperglycemia, according to a study from Nationwide Children’s Hospital.  These findings appear in Pediatric Diabetes. 
Adults and adolescents with type 1 diabetes have impaired endothelial function.  “Specifically, hyperglycemia increases oxygen radicals which decrease the nitric oxide stress response,” says Robert P. Hoffman, MD, member of the Section of Endocrinology and Metabolism at Nationwide Children’s Hospital. 
Research in healthy adults has shown that intravenous or oral doses of vitamin C blocks the dilatory effects of hyperglycemia on endothelial function.  Also, a 12-hour vitamin C infusion can restore endothelial function to normal levels in adults with recent onset or well-controlled type 1 diabetes.  However, it is unknown whether vitamin C can prevent acute effects of hyperglycemia in patients with type 1 diabetes, particularly adolescents.  
To test this scenario, Dr. Hoffman and colleagues at Nationwide Children’s enrolled eight adolescents with type 1 diabetes in a clinical study.  After having their fasting plasma glucose level recorded, each participant received insulin infusion.  Samples were taken every five minutes to determine plasma glucose.  When euglycemia was achieved, dextrose was added to maintain this level for 30 minutes and endothelial function measurements were performed at the end of euglycemia.  The dextrose infusion was then increased to raise the plasma glucose to 200 mg/dl for 1 hour and endothelial function was retested. The participants returned for a second study during which vitamin C infusion was initiated at the same time as the insulin infusion. 
Findings showed that acute vitamin C infusion was able to minimize acute, hyperglycemic impairment of endothelial function in the study participants. Hyperglycemia caused a fall in the reactive hyperemic response to arterial occlusion, but these decreases did not occur during hyperglycemia with vitamin C infusion. 
“Our results demonstrate that hyperglycemic impairment of endothelial function occurs without a change in plasma insulin since our patients were insulin-deficient and treated with a continuous insulin infusion,” says Dr. Hoffman.  “The fact that vitamin C infusion prevents and restores hyperglycemic-induced endothelial impairment indicates that its use may be helpful in preventing long-term diabetic complications.” 
Hoffman RP, Dye AS, Bauer JA. Ascorbic acid blocks hyperglycemic impairment of endothelial function in adolescents with type 1 diabetes.  Pediatr Diabetes. 2012 Aug 28;9999(9999). doi: 10.1111/j.1399-5448.2012.00882.x. [Epub ahead of print]

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