Vitamin D deficiency is associated with an oxidized plasma cysteine redox potential in critically Ill children

Critically ill populations incur high levels of oxidative stress and commonly present with vitamin D deficiency. This study aimed to investigate the relationship between vitamin D status and plasma markers of glutathione (GSH) and cysteine (Cys) redox and immunity in critically ill children. This was a cross-sectional study of n = 50 PICU patients. Subjects were categorized according to their plasma 25-hydroxyvitamin D [25(OH)D] concentrations: (<20, 20-30, and ≥30 ng/dL). Plasma GSH, glutathione disulfide (GSSG), Cys, and cystine (CySS) were measured with high-performance liquid chromatography, and their associated redox potentials determined (EhGSSG and EhCySS, respectively). Plasma LL-37, an indicator of innate immune function, was assayed with ELISA. Data were analyzed using general linear regression before and after adjustment for age, sex, and race. Results showed that EhCySS was more reduced in subjects with plasma 25(OH)D concentrations ≥30 ng/mL compared to those with 25(OH)D concentrations <20 ng/mL (P = 0.009). Plasma GSH, GSSG, and total GSH decreased with increasing 25(OH)D category (P = 0.06, 0.03, and 0.01, respectively), and plasma glutamine levels were lowest in subjects with plasma 25(OH)D concentrations ≥30 ng/mL (P = 0.004). Plasma LL-37 concentrations did not significantly differ by vitamin D status (P = 0.08). In conclusion, vitamin D sufficiency was associated with more reduced plasma EhCySS, indicative of lower oxidative stress in critically ill children. Plasma GSH, GSSG, and glutamine, however, were lower in the vitamin D sufficient group. The role of vitamin D in maintaining redox status during pediatric critical illness requires further study.