Relation between riboflavin, flavin mononucleotide and flavin adenine dinucleotide concentrations in plasma and red cells in patients with critical illness

BackgroundThere is some evidence that the relationship between plasma and red cell vitamin B2 concentrations is perturbed in the critically ill patient. The aim of the present study was to examine the longitudinal interrelationships between riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) in plasma and red cells in patients with critical illness.MethodsRiboflavin, FMN and FAD concentrations were measured, by HPLC, in plasma and red cells in healthy subjects (n = 119) and in critically ill patients (n = 125) on admission and on follow-up.ResultsOn admission, compared with the controls, critically ill patients had significantly higher plasma riboflavin and FMN concentrations (p < 0.001) and lower median plasma FAD concentrations (p < 0.001). In the red cell, FAD concentrations were significantly lower in critically ill patients (p < 0.001). In healthy subjects, plasma riboflavin was directly associated with both plasma FMN (rs = 0.55, p < 0.001) and plasma FAD (rs = 0.49, p < 0.001). Red cell riboflavin was directly associated with red cell FMN (rs = 0.52, p < 0.001) but not red cell FAD. In the critically ill patients, plasma riboflavin was not significantly associated with either plasma FMN or FAD. Red cell riboflavin was directly associated with red cell FMN (rs = 0.79, p < 0.001) and red cell FAD (rs = 0.72, p < 0.001). Longitudinal measurements (n = 60) were similar.ConclusionsThe relationship between plasma riboflavin, FMN and FAD was significantly perturbed in critical illness. This effect was less pronounced in red cells. Therefore, red cell FAD concentrations are more likely to be a reliable measure of status in the critically ill patient.