Clinical Observations, Plasma Retinol Concentrations, and In Vitro Lymphocyte Functions in Children With Sickle Cell Disease

Fat-Soluble Vitamers: Parent-Child Concordance and Population Epidemiology in the Longitudinal Study of Australian Children

Fat-soluble vitamers (FSV) are a class of diverse organic substances important in a wide range of biological processes, including immune function, vision, bone health, and coagulation. Profiling FSV in parents and children enables insights into gene-environment contributions to their circulating levels, but no studies have reported on the population epidemiology of FSV in these groups as of yet. In this study, we report distributions of FSV, their parent-child concordance and variation by key characteristics for 2490 children (aged 11-12 years) and adults (aged 28-71 years) in the Child Health CheckPoint of the Longitudinal Study of Australian Children. Ten A, D, E and K vitamers were quantified using a novel automated LC-MS/MS method. All three K vitamers (i.e., K1, MK-4, MK-7) and 1-α-25(OH)₂D₃ were below the instrument detection limit and were removed from the present analysis. We observed a strong vitamer-specific parent-child concordance for the six quantifiable A, D and E FSVs. FSV concentrations all varied by age, BMI, and sex. We provide the first cross-sectional population values for multiple FSV. Future studies could examine relative genetic vs. environmental determinants of FSV, how FSV values change longitudinally, and how they contribute to future health and disease.

What Are the Effects of Vitamin A Oral Supplementation in the Prevention and Management of Viral Infections? A Systematic Review of Randomized Clinical Trials

Vitamin A (VA) deficiency is associated with increased host susceptibility to infections, but evidence on its role in the prevention and management of viral infections is still lacking. This review aimed at summarizing the effects of VA supplementation against viral infections to support clinicians in evaluating supplemental treatments. PubMed, Scopus, and Web of Science were searched. Randomized clinical trials comparing the direct effects of VA oral supplementation in any form vs. placebo or standard of care in the prevention and/or management of confirmed viral infections in people of any age were included. A narrative synthesis of the results was performed. The revised Cochrane Risk-Of-Bias tool was used to assess quality. Overall, 40 articles of heterogeneous quality were included. We found data on infections sustained by Retroviridae (n = 17), Caliciviradae (n = 2), Flaviviridae (n = 1), Papillomaviridae (n = 3), Pneumoviridae (n = 4), and Paramyxoviridae (n = 13). Studies were published between 1987 and 2017 and mostly conducted in Africa. The findings were heterogeneous across and within viral families regarding virological, immunological, and biological response, and no meaningful results were found in the prevention of viral infections. For a few diseases, VA-supplemented individuals had a better prognosis and improved outcomes, including clearance of HPV lesions or reduction in some measles-related complications. The effects of VA oral supplementation seem encouraging in relation to the management of a few viral infections. Difference in populations considered, variety in recruitment and treatment protocols might explain the heterogeneity of the results. Further investigations are needed to better identify the benefits of VA administration.

In Vitro Lymphocyte Functions in Undernourished Children With Sickle Cell Anemia

Background: Children with sickle cell disease (SCD) often suffer from growth deficits and impaired immunity. However, the association between mild to moderate malnutrition and in vitro lymphocyte function has not been well studied. The goal of this study was to investigate the effects of undernutrition on lymphocyte functions in children with SCD. Methods: Weight; height; plasma concentrations of albumin (Alb), prealbumin (PA), transferrin (Tf), retinol-binding protein (RBP), α₁-acid glycoprotein (AGP), C-reactive protein (CRP), and ceruloplasmin (Cp); and lymphocyte proliferation and interleukin (IL)-2 in phytohemagglutinin-treated blood lymphocytes were measured in 90 children with SCD (59 SS, 4 Sβ°, 27 SC hemoglobin genotypes). Results: The mean age of the children included in the analysis was 7.65 years. Four of the 90 children had weight and height below the fifth percentile. A higher percentage of children with HbSS/HbSβ° (61.4%) than of those with HbSC (44%) had ≥2 plasma protein concentrations below normal (Alb <35 g/L, PA <160 mg/L, Tf <2.0 g/L, and RBP ≤20 mg/L). Mean anthropometric measurements, hemoglobin, and hematocrit were lower in children with HbSS/HbSβ° than in those with HbSC (P<0.05). Lymphocyte proliferation was reduced by 20% to 27% in children with HbSS/HbSβ° with undernutrition plus inflammation (AGP >1 g/L, CRP >5 mg/L, Cp >600 mg/L) compared to children with neither. Regardless of inflammatory status, lymphocyte proliferation was reduced by 29% to 49% in children with HbSS/HbSβ° and undernutrition defined by PA or Alb plus RBP (P<0.05) compared to those with RBP within normal range. Neither undernutrition nor inflammation reduced lymphocyte proliferation in children with HbSC. Mean IL-2 activity was reduced by undernutrition, defined as PA <160 mg/L, in both groups. PA, RBP, and hemoglobin concentrations positively correlated with in vitro lymphocyte functions (P<0.05). Conclusion: Undernutrition altered in vitro lymphocyte function in children with the HbSS/HbSβ° genotypes. Dietary supplements may improve the altered functions in these children.

Hemoglobin alters vitamin carrier uptake and vitamin D metabolism in proximal tubule cells: implications for sickle cell disease

Kidney disease, including proximal tubule (PT) dysfunction, and vitamin D deficiency are among the most prevalent complications in sickle cell disease (SCD) patients. Although these two comorbidities have never been linked in SCD, the PT is the primary site for activation of vitamin D. Precursor 25-hydroxyvitamin D [25(OH)D] bound to vitamin D-binding protein (DBP) is taken up by PT cells via megalin/cubilin receptors, hydroxylated to the active 1,25-dihydroxyvitamin D [1,25(OH)₂D] form, and released into the bloodstream. We tested the hypothesis that cell-free hemoglobin (Hb) filtered into the PT lumen impairs vitamin D uptake and metabolism. Hb at concentrations expected to be chronically present in the ultrafiltrate of SCD patients competed directly with DBP for apical uptake by PT cells. By contrast, uptake of retinol binding protein was impaired only at considerably higher Hb concentrations. Prolonged exposure to Hb led to increased oxidative stress in PT cells and to a selective increase in mRNA levels of the CYP27B1 hydroxylase, although protein levels were unchanged. Hb exposure also impaired vitamin D metabolism in PT cells, resulting in reduced ratio of 1,25(OH)₂D:25(OH)D. Moreover, plasma levels of 1,25(OH)₂D were reduced in a mouse model of SCD. Together, our data suggest that Hb released by chronic hemolysis has multiple effects on PT function that contribute to vitamin D deficiency in SCD patients.