Vitamin C in Health and Diabetes (Protocol 04DK0021)

National Institute Of Diabetes And Digestive And Kidney Diseases

Investigators

Abstract

In our research publication titled “Abnormal urinary loss of vitamin C in diabetes: prevalence and clinical characteristics of a vitamin C renal leak” [Ebenuwa I et al., Am J Clin Nutr. 2022 Jul 6;116(1):274-284.], we derived the precise sex-specific estimates of normal vitamin C renal threshold—the plasma vitamin C concentrations at which renal reabsorption is maximized and urinary excretion occurs. We used data from vitamin C depletion-repletion studies, mathematical modeling tools and sensitive vitamin C assays developed in our laboratory. We also described the minimal elimination threshold (MET), the plasma vitamin C concentrations below which urinary vitamin C excretion would be abnormal. We incorporated these physiologic vitamin C parameters to into a set of criteria for determining when an individual has abnormal urinary vitamin C loss or a renal leak. We applied these criteria and investigated vitamin C renal leak prevalence. We found that individuals with diabetes had significantly lower plasma vitamin C concentrations and higher prevalence of vitamin C renal leak compared to nondiabetic controls. We also found that vitamin C renal leak was significantly associated with hyperglycemia, proteinuria, and microvascular complications.