Abstract
Diabetes mellitus is an umbrella term for disorders with chronically elevated blood glucose levels outside of the 'normal' range. Malnutrition can be both a risk factor for the development of diabetes mellitus and a consequence of the disease. A micronutrient that was of interest in the current study was vitamin C and its, previously researched, tendency to be present at insufficient levels in those with diabetes.
This study aimed to investigate the possibility of a relationship between the plasma vitamin C concentration in those with type 1 diabetes mellitus (T1DM), and type 2 diabetes mellitus (T2DM), and the common complication of renal impairment. It was hypothesised that there would be a relationship between decreased plasma vitamin C concentrations and increased renal impairment, and in turn, increased urine vitamin C concentrations being observed. Additionally, differences in plasma vitamin C concentrations between T1DM and T2DM were investigated, alongside characteristics such as body weight, body mass index (BMI) and hypertension.
A retrospective observational study was conducted, using stored plasma and urine samples collected for a previous observational study, to investigate these points. Using high-performance liquid chromatography, the vitamin C concentrations in both the plasma and urine samples were measured, and their relationships analysed with the participant data collected from the original study. This cohort (n=136) was found to have a significant relationship between decreased plasma vitamin C and the presence of renal disease (p = 0.007), with elevated albumin-creatinine ratio (> 30) appearing to contribute to this relationship (p = 0.027). However, the preliminary results of this study do not suggest that the deficiency in plasma vitamin C was due to enhanced urinary output of vitamin C. The plasma vitamin C concentrations were found to be significantly lower in the T2DM cohort (n=63) than the T1DM cohort (n=73). This difference could be partially explained by the differences in weight and BMI between the two cohorts, as both weight and BMI were found to be inversely related to plasma vitamin C concentration (Rs = - 0.39, p < 0.0001; and Rs = - 0.36, p < 0.0001, respectively).
Overall, this study did find a relationship between the presence of renal disease and decreased plasma vitamin C concentrations in those with diabetes mellitus, however, this cannot be suggested as the cause of this decrease due to unmeasured variables, such as dietary intake, and the presence of renal disease being a likely indicator of the severity of diabetes mellitus.
This research provides a basis for future research into the possible effects of vitamin C supplementation and diet changes, on plasma vitamin C concentration in those with diabetes mellitus, as well as on related physiology, such as body weight and BMI.