A low molar ratio of retinol binding protein to transthyretin indicates vitamin A deficiency during inflammation: studies in rats and a posterior analysis of vitamin A-supplemented children with measles

Vitamin A homeostasis and cardiometabolic disease in humans: lost in translation?

Vitamin A (retinol) is an essential, fat-soluble vitamin that plays critical roles in embryonic development, vision, immunity, and reproduction. Severe vitamin A deficiency results in profound embryonic dysgenesis, blindness, and infertility. The roles of bioactive vitamin A metabolites in regulating cell proliferation, cellular differentiation, and immune cell function form the basis of their clinical use in the treatment of dermatologic conditions and hematologic malignancies. Increasingly, vitamin A also has been recognized to play important roles in cardiometabolic health, including the regulation of adipogenesis, energy partitioning, and lipoprotein metabolism. While these roles are strongly supported by animal and in vitro studies, they remain poorly understood in human physiology and disease. This review briefly introduces vitamin A biology and presents the key preclinical data that have generated interest in vitamin A as a mediator of cardiometabolic health. The review also summarizes clinical studies performed to date, highlighting the limitations of many of these studies and the ongoing controversies in the field. Finally, additional perspectives are suggested that may help position vitamin A metabolism within a broader biological context and thereby contribute to enhanced understanding of vitamin A's complex roles in clinical cardiometabolic disease.

Hypothesis: Low Vitamin A and D Levels Worsen Clinical Outcomes When Children with Sickle Cell Disease Encounter Parvovirus B19

Human parvovirus B19 causes life-threatening anemia due to transient red cell aplasia (TRCA) in individuals with sickle cell disease (SCD). Children with SCD experiencing profound anemia during TRCA often require red blood cell transfusions and hospitalization. The prevalence of vitamin deficiencies in SCD is high and deficiencies are associated with respiratory and pain symptoms, but the effects of vitamins on acute infection with parvovirus B19 remain unclear. We performed a clinical study in which 20 SCD patients hospitalized with parvovirus B19 infections (Day 0) were monitored over a 120-day time course to query relationships between vitamins A and D and clinical outcomes. There were significant negative correlations between Day 0 vitamin levels and disease consequences (e.g., red blood cell transfusion requirements, inflammatory cytokines). There were significant positive correlations (i) between Day 0 vitamins and peak virus-specific antibodies in nasal wash, and (ii) between Day 0 virus-specific serum plus nasal wash antibodies and absolute reticulocyte counts. There was a significant negative correlation between Day 0 virus-specific serum antibodies and virus loads. To explain the results, we propose circular and complex mechanisms. Low baseline vitamin levels may weaken virus-specific immune responses to permit virus amplification and reticulocyte loss; consequent damage may further reduce vitamin levels and virus-specific immunity. While the complex benefits of vitamins are not fully understood, we propose that maintenance of replete vitamin A and D levels in children with SCD will serve as prophylaxis against parvovirus B19-induced TRCA complications.

Nutritional markers and proteome in patients undergoing treatment for pulmonary tuberculosis differ by geographic region

Introduction

Contemporary phase 2 TB disease treatment clinical trials have found that microbiologic treatment responses differ between African versus non-African regions, the reasons for which remain unclear. Understanding host and disease phenotypes that may vary by region is important for optimizing curative treatments.

Methods

We characterized clinical features and the serum proteome of phase 2 TB clinical trial participants undergoing treatment for smear positive, culture-confirmed TB, comparing host serum protein expression in clinical trial participants enrolled in African and Non-African regions. Serum samples were collected from 289 participants enrolled in the Centers for Disease Control and Prevention TBTC Study 29 (NCT00694629) at time of enrollment and at the end of the intensive phase (after 40 doses of TB treatment).

Results

After a peptide level proteome analysis utilizing a unique liquid chromatography IM-MS platform (LC-IM-MS) and subsequent statistical analysis, a total of 183 core proteins demonstrated significant differences at both baseline and at week 8 timepoints between participants enrolled from African and non-African regions. The majority of the differentially expressed proteins were upregulated in participants from the African region, and included acute phase proteins, mediators of inflammation, as well as coagulation and complement pathways. Downregulated proteins in the African population were primarily linked to nutritional status and lipid metabolism pathways.

Conclusions

We have identified differentially expressed nutrition and lipid pathway proteins by geographic region in TB patients undergoing treatment for pulmonary tuberculosis, which appear to be associated with differential treatment responses. Future TB clinical trials should collect expanded measures of nutritional status and further evaluate the relationship between nutrition and microbiologic treatment response.

The coronavirus disease (COVID-19) - A supportive approach with selected micronutrients

Worldwide the pandemic of COVID-19 spreads rapidly and has had an enormous public health impact with substantial morbidity and mortality especially in high-risk groups, such as older people and patients with comorbidities like diabetes, dementia or cancer. In the absence of a vaccine against COVID-19 there is an urgent need to find supportive therapies that can stabilize the immune system and can help to deal with the infection, especially for vulnerable groups such as the elderly. This is especially relevant for our geriatric institutions and nursing homes. A major potential contributing factor for elderly is due to their high incidence of malnutrition: up to 80% among the hospitalized elderly. Malnutrition results when adequate macronutrients and micronutrients are lacking in the diet. Often missing in public health discussions around preventing and treating COVID-19 patients are nutritional strategies to support optimal function of their immune system. This is surprising, given the importance that nutrients play a significant role for immune function. Several micronutrients, such as vitamin D, retinol, vitamin C, selenium and zinc are of special importance supporting both the adaptive and innate immune systems. As suboptimal status or deficiencies in these immune-relevant micronutrients impair immune function and reduces the resistance to infections, micronutrient deficiencies should therefore be corrected as soon as possible, especially in the elderly and other vulnerable groups. According to epidemiological, experimental and observational studies, some case reports and a few intervention studies the supplementation of vitamin D and/or zinc are promising. The multiple anti-inflammatory and immunomodulatory effects of Vitamin D could explain its protective role against immune hyper reaction and cytokine storm in patients with severe COVID-19. A randomized, placebo-controlled intervention study even shows that high dose vitamin D supplementation promotes viral clearance in asymptomatic and mildly symptomatic SARS-CoV-2 positive individuals. Besides, the data of a recent prospective study with COVID-19 patients reveal that a significant number of them were zinc deficient. The zinc deficient patients had more complications and the deficiency was associated with a prolonged hospital stay and increased mortality. Thus, immune-relevant micronutrients may help to increase the physiological resilience against COVID-19.

Adiposity, inflammation and fat-soluble vitamins in adolescents

OBJECTIVE

Evaluate the association between inflammatory process, adiposity, and vitamins A, D, and E in adolescents, according to gender.

METHODS

Cross-sectional study with adolescents aged 12-19 years old of both genders attending public schools in Recife. A questionnaire was used to collect data on socioeconomic level, lifestyle, and food intake of adolescents. Then, an anthropometric evaluation and a blood sampling were performed to analyze serum concentrations of α-1-acid glycoprotein, retinol, β-carotene, α-tocopherol, and 25-hydroxy-vitamin D.

RESULTS

The levels of α-1-acid glycoprotein were higher for abdominal obesity in both genders. Male adolescents with insufficient serum α-tocopherol levels had low levels of α-1-acid glycoprotein (p=0.03) and an increased risk of 25-hydroxy-vitamin D and β-carotene deficiency in relation to total and abdominal fat; female adolescents had an increased risk of insufficient β-carotene with abdominal obesity (PR: 1.33; 95% CI: 1.2-1.5).

CONCLUSION

Abdominal adiposity implies a higher risk of inflammation and causes different changes to the levels of fat-soluble vitamins according to gender.

Low plasma vitamin A concentration is associated with tuberculosis in Moroccan population: a preliminary case control study

BACKGROUND

Vitamin A plays numerous roles in immune system. Its deficiency alters both the innate and adaptive immunity. Previous results reported that the micronutrients deficiency, particularly vitamin A, is observed in patients with tuberculosis. Thus, we aimed in this study to assess vitamin A concentrations in Moroccan patients with tuberculosis to set up a large efficacy study of vitamin A supplementation for TB infected patients. Plasma retinol concentration was measured by HPLC in 44 recently diagnosed TB patients and 40 healthy controls.

RESULTS

We showed that plasma vitamin A is significantly lower in tuberculosis patients as compared to healthy controls (p < 0.0001). Moreover, no significant association was found between vitamin A deficiency and, TB severity and patients' ages.

CONCLUSION

Our study confirms the association between low vitamin A levels and tuberculosis disease.

Metabolic Effects of Inflammation on Vitamin A and Carotenoids in Humans and Animal Models

The association between inflammation and vitamin A (VA) metabolism and status assessment has been documented in multiple studies with animals and humans. The relation between inflammation and carotenoid status is less clear. Nonetheless, it is well known that carotenoids are associated with certain health benefits. Understanding these relations is key to improving health outcomes and mortality risk in infants and young children. Hyporetinolemia, i.e., low serum retinol concentrations, occurs during inflammation, and this can lead to the misdiagnosis of VA deficiency. On the other hand, inflammation causes impaired VA absorption and urinary losses that can precipitate VA deficiency in at-risk groups of children. Many epidemiologic studies have suggested that high dietary carotenoid intake and elevated plasma concentrations are correlated with a decreased risk of several chronic diseases; however, large-scale carotenoid supplementation trials have been unable to confirm the health benefits and in some cases resulted in controversial results. However, it has been documented that dietary carotenoids and retinoids play important roles in innate and acquired immunity and in the body's response to inflammation. Although animal models have been useful in investigating retinoid effects on developmental immunity, it is more challenging to tease out the effects of carotenoids because of differences in the absorption, kinetics, and metabolism between humans and animal models. The current understanding of the relations between inflammation and retinoid and carotenoid metabolism and status are the topics of this review.

Proxy markers of serum retinol concentration, used alone and in combination, to assess population vitamin A status in Kenyan children: a cross-sectional study

BACKGROUND

Serum retinol concentration determined by high-performance liquid chromatography (HPLC) is recommended by the World Health Organization to assess population vitamin A status. This assay is expensive, technically demanding and rarely available in developing countries. Our objective was a) to assess the diagnostic performance of proxy markers in detecting vitamin A deficiency and b) to derive decision rules based on these markers to estimate vitamin A deficiency prevalence.

METHODS

A survey was conducted in 15 rural primary schools in Eastern Province, Kenya, with 375 children aged 6 to 12 years (25 randomly selected per school). Serum retinol concentration <0.70 μmol/L by HPLC was used to define vitamin A deficiency. Proxy markers for vitamin A deficiency were serum concentrations of retinol binding protein (RBP), transthyretin, retinol measured by fluorometry and RBP:transthyretin molar ratio.

RESULTS

The prevalence of vitamin A deficiency (HPLC) was 18%. Transthyretin and RBP showed the best diagnostic performance individually, with area-under-the-curve (AUC) values of 0.96 and 0.93. When combined, and with C-reactive protein added, the AUC increased to 0.98. A simple decision rule {(-15.277 × [RBP, μmol/L] - 7.013 × [Transthyretin, μmol/L] + 0.367 × [C-reactive protein, mg/L] + 24.714) > 0.496} yielded prevalence estimates of vitamin A deficiency that is unbiased by diagnostic error.

CONCLUSIONS

The combination of transthyretin, RBP and C-reactive protein concentrations could eventually replace retinol concentration by HPLC in resource-poor settings as the preferred method to assess the population burden of vitamin A deficiency.

Reduced serum retinol-binding protein levels in patients with de novo acute myeloid leukaemia

Retinol-binding protein (RBP) has been used as a nutritional index for children with acute myeloid leukaemia (AML) in previous studies. However, no studies have yet examined RBP levels in AML patients from all age groups. In this study, AML patients presented with lower RBP concentrations than healthy control subjects and patients with benign haematopathies. A negative association was observed between serum RBP level and peripheral white blood cell count in M4 and M5 AML patients. Moreover, patients carrying the FLT3-ITD mutation and young patients had lower RBP levels than those lacking this mutation and elderly patients. In conclusion, these observations suggest that aberrant retinol levels may be associated with AML.

The effect of vitamin A supplementation on thyroid function in premenopausal women

OBJECTIVE

Vitamin A and its retinoid derivates play an important role in regulation of normal growth and development. Vitamin A has been shown to regulate thyroid hormone metabolism and inhibit thyroid-stimulating hormone (TSH) secretion via down regulation of TSH-β gene expression; however, the effect of vitamin A on thyroid function in obese individuals who are at higher risk of subclinical hypothyroidism is still unclear. In the present study we investigate the impact of vitamin A supplementation on thyroid function in obese women.

METHOD

A 4-month randomized, double blind controlled trial was conducted among 84 healthy women aged 17-50 years old: 56 were obese (body mass index [BMI] 30-35 kg/m(2)) and 28 were nonobese (BMI 18.5-24.9 kg/m(2)). Obese women were randomly allocated to receive either vitamin A (25,000 IU/d retinyl palmitate) or placebo. Nonobese women received vitamin A. At baseline and 4 months after intervention, serum concentrations of TSH, total thyroxine (T4), total triiodothyronine (T3), retinol-binding protein (RBP), and transthyretin (TTR) were measured.

RESULTS

Baseline concentrations of thyroid hormones, RBP and TTR were not significantly different between groups. Vitamin A caused a significant reduction in serum TSH concentrations in obese (p = 0.004) and nonobese (p = 0.001) groups. Serum T3 concentrations also increased in both obese and nonobese vitamin A-treated groups (p < 0.001). Serum T4 decreased in all 3 groups after treatment. The results showed a significant reduction in serum RBP in the obese group after vitamin A supplementation (p = 0.007), but no significant change was seen in serum TTR.

CONCLUSIONS

Serum TSH concentrations in vitamin A-treated subjects were significantly reduced; therefore, vitamin A supplementation might reduce the risk of subclinical hypothyroidism in premenopausal women.

Vitamin A deficiency alters airway resistance in children with acute upper respiratory infection

OBJECTIVE

To assess whether vitamin A deficiency alters the recovery of total respiratory resistance (TRR) following acute upper respiratory tract infection (URI).

METHODS

This is a case control study of children, age 4-6 years and grouped as: URI, (n = 74), URI and wheezing, (URI-wheezing, n = 52), and healthy controls (n = 51). Vitamin A and total respiratory resistance (TRR) were assessed using the modified relative dose response (MRDR) and forced oscillometry, respectively.

RESULTS

Children with URI and URI-wheezing had lower retinol, 32.4 ± 13.12 and 18.3 ± 6.83 µg/dl respectively, compared to controls, 56.9 ± 29.82 µg/dl (ANOVA, P < 0.001). The MRDR was elevated in children in the URI or URI-wheezing groups 0.066 ± 0.045 and 0.021 ± 0.021, respectively, compared to controls 0.007 ± 0.006 (ANOVA, P < 0.0001). The TRR in the URI and URI-wheezing groups differed from controls. During convalescence, the TRR failed to decline in the URI-group only when the MRDR was >0.06. In the URI-wheezing group, TRR declined independently of retinol and MRDR.

CONCLUSION

Vitamin A contributes to preservation of airway function during and in recovery after upper respiratory infection in children.

In vitro effect of human serum and fetal calf serum on CD4+ T cells proliferation in response to myelin oligodendrocyte glycoprotein (MOG) in correlation with RBP/TTR ratio in multiple sclerotic patients

Myelin oligodendrocyte glycoprotein (MOG) is one of the autoantigens used in evaluation of the CD4(+) T cells proliferation response in multiple sclerotic patients. In cell culture, human serum (HS) is one of the promising substitutions for fetal calf serum (FCS) that can induce different autoreactivity of T cells and fluctuation of autoantibody production from B cells. Because of immunomodulatory function of vitamin A, we examined the effect of HS and FCS on CD4(+) T cells proliferation in response to MOG in correlation with serum retinol-binding protein (RBP)/transthyretin (TTR) ratio, as an indirect way to assess vitamin A status in multiple sclerotic patients. Patients' peripheral blood mononuclear cells were isolated and cultured in the presence of MOG as well as FCS and HS both separately and together. Cell proliferation was evaluated using BrdU kit. Serum RBP and TTR levels were measured by ELISA kit. FCS and HS increase CD4(+) T cell proliferation. RBP/TTR ratio has significant negative correlation with cell proliferation in the presence of MOG, HS, and FCS. HS with FCS provides an appropriate medium for autoreactivity and proliferation of CD4(+) T cells. Vitamin A has a crucial role in regulation of this pathway.

Effect of all-transretinoic acid on Th17 and T regulatory cell subsets in patients with ankylosing spondylitis

OBJECTIVE

We compared Th17 and T regulatory cells in patients with ankylosing spondylitis (AS) and in healthy controls. The effect of all-transretinoic acid (ATRA) was studied on cultured CD4+ T cells of patients with AS compared to controls.

METHODS

Eighteen patients with AS and 18 age- and sex-matched healthy controls were included. CD4+ T cells were separated and cultured in conditions of anti-CD3 and anti-CD28 stimulation with and without ATRA. Intracellular and secreted cytokines, transcription factors, and gene expression were evaluated after 72 h.

RESULTS

The frequency of CD4+IL-17+ T cells was significantly higher in patients with AS compared to controls, and ATRA could significantly decrease it. The frequency of forkhead box protein 3 (FOXP3)+ retinoic acid-related orphan receptor γt (RORγt) negative T-bet negative CD4+ cells was significantly lower in cases compared to controls. Intracellular and secreted interferon-γ (IFN-γ) was not significantly different between cases and controls. ATRA significantly increased intracellular IFN-γ in cases but not in controls. Tumor necrosis factor-α (TNF-α) secretion was significantly higher and interleukin 10 secretion was significantly lower in culture supernatant of cases compared to controls. ATRA could significantly decrease TNF-α secretion in cases.

CONCLUSION

Our findings favor a pathogenic role for Th17 cells in AS. Th1 cells did not seem to contribute in the pathogenesis of this disease. The effect of ATRA as an immunomodulator on deviated immune cells was associated with decreased inflammatory markers. This association could be a reason for a clinical trial of ATRA in patients with AS.

Association of high-sensitivity C-reactive protein with cardiometabolic risk factors and micronutrient deficiencies in adults of Ouagadougou, Burkina Faso

Increasing evidence suggests that high-sensitivity C-reactive protein (hs-CRP) is associated with cardiometabolic risk factors (CMRF) while being also related to micronutrient deficiencies. As part of a project on the double burden of under- and overnutrition in sub-Saharan Africa, we assessed the relationship between hs-CRP and both CMRF and micronutrient deficiencies in a population-based cross-sectional study carried out in the Northern district of Ouagadougou, the capital city of Burkina Faso. We randomly selected 330 households stratified by income tertile. In each income stratum, 110 individuals aged 25-60 years and having lived in Ouagadougou for at least 6 months were randomly selected, and underwent anthropometric measurements and blood sample collection. The prevalence of high hs-CRP was 39.4 %, with no sex difference. Vitamin A-deficient subjects (12.7 %) exhibited significant risk of elevated hs-CRP (OR 2.5; P= 0.015). Serum ferritin was positively correlated with log hs-CRP (r 0.194; P= 0.002). The risk of elevated hs-CRP was significant in subjects with BMI ≥ 25 kg/m² (OR 6.9; 95 % CI 3.6, 13.3), abdominal obesity (OR 4.6; 95 % CI 2.2, 7.3) and high body fat (OR 10.2; 95 % CI 5.1, 20.3) (P< 0.001, respectively). Independent predictors of hs-CRP in linear regression models were waist circumference (β = 0.306; P= 0.018) and serum TAG (β = 0.158; P= 0.027). In this sub-Saharan population, hs-CRP was consistently associated with adiposity. Assuming that plasma hs-CRP reflects future risk of cardiovascular events, intervention which reduces CRP, or chronic and acute nutrition conditions associated with it, could be effective in preventing their occurrence particularly in sub-Saharan Africa.

Retinoic acid influences neuronal migration from the ganglionic eminence to the cerebral cortex

The ganglionic eminence contributes cells to several forebrain structures including the cerebral cortex, for which it provides GABAergic interneurons. Migration of neuronal precursors from the retinoic-acid rich embryonic ganglionic eminence to the cerebral cortex is known to be regulated by several factors, but retinoic acid has not been previously implicated. We found retinoic acid to potently inhibit cell migration in slice preparations of embryonic mouse forebrains, which was reversed by an antagonist of the dopamine-D(2) receptor, whose gene is transcriptionally regulated by retinoic acid. Histone-deacetylase inhibitors, which amplify nuclear receptor-mediated transcription, potentiated the inhibitory effect of retinoic acid. Surprisingly, when retinoic acid signalling was completely blocked with a pan-retinoic acid receptor antagonist, this also decreased cell migration into the cortex, implying that a minimal level of endogenous retinoic acid is necessary for tangential migration. Given these opposing effects of retinoic acid in vitro, the in vivo contribution of retinoic acid to migration was tested by counting GABAergic interneurons in cortices of adult mice with experimental reductions in retinoic acid signalling: a range of perturbations resulted in significant reductions in the numerical density of some GABAergic interneuron subpopulations. These observations suggest functions of retinoic acid in interneuron diversity and organization of cortical excitatory-inhibitory balance.

Vitamin A: biomarkers of nutrition for development

Vitamin A is essential for multiple functions in mammals. Without vitamin A, mammals cannot grow, reproduce, or fight off disease. Because of its numerous functions in humans, biomarkers of vitamin A status are quite diverse. Assessment of liver reserves of vitamin A is considered the gold standard because the liver is the major storage organ. However, this measure is not feasible in human studies. Alternative biomarkers of status can be classified as biological, functional, histologic, and biochemical. Historically, signs of xerophthalmia were used to determine vitamin A deficiency. Before overt clinical damage to the eye, individuals who suffer from vitamin A deficiency are plagued by night blindness and longer vision-restoration times. These types of assessments require large population-based evaluations. Therefore, surrogate biochemical measures of vitamin A status, as defined by liver reserves, have been developed. Serum retinol concentrations are a common method used to evaluate vitamin A deficiency. Serum retinol concentrations are homeostatically controlled until liver reserves are dangerously low. Therefore, other biochemical methods that respond to liver reserves in the marginal category were developed. These included dose-response tests and isotope dilution assays. Dose-response tests work on the principle that apo-retinol-binding protein builds up in the liver as liver reserves become depleted. A challenge dose of vitamin A binds to this protein, and serum concentrations increase within a few hours if liver vitamin A concentrations are low. Isotope dilution assays use stable isotopes as tracers of total body reserves of vitamin A and evaluate a wide range of liver reserves. Resources available and study objectives often dictate the choice of a biomarker.

Changes in retinol-binding protein concentrations and thyroid homeostasis with nonoccupational exposure to DDT

BACKGROUND

The insecticide dichlorodiphenyltrichloroethane (DDT) has been used for malaria vector control in the northern and eastern parts of the Vhembe District of Limpopo Province, South Africa, since 1945. Bioaccumulation of DDT raises concern because it reportedly affects thyroid function.

OBJECTIVE

Our objective was to investigate the association between DDT uptake (as reflected in plasma concentrations) and thyroid homeostasis while considering related factors.

METHODS

We compared dietary intake, serum retinol-binding protein (RBP), transthyretin (TTR) and albumin concentrations, and liver and thyroid function between cases with evidence of a body burden of DDT in the circulation (concentration of any DDT isomer ≥ 0.02 µg/g lipid; n = 278) and controls (concentration of all DDT isomers < 0.02 µg/g lipid; n = 40) in a cross-sectional study. Further analyses were performed to assess the relevance of changes in RBP status associated with DDT uptake.

RESULTS

RBP concentrations below the reference range were more prevalent in cases (54% vs. 10% in controls; χ² = 27.4; p < 0.001), which could not be explained by nutrient intake. We observed significantly lower thyroid hormone concentrations among cases (p ≤ 0.01). We also observed a significant linear trend for serum concentrations of free thyroxine and free triiodothyronine (p < 0.001) and a significant quadratic trend for serum thyroid-stimulating hormone (p = 0.025) and TTR (p < 0.001) across the control group and case groups with normal and relatively low RBP concentrations. Relatively low RBP concentrations were associated with significantly higher DDT and 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) isomer concentrations and with a higher DDE/DDT ratio (p ≤ 0.01), which signifies long-term exposure. Inadequate intake of vitamin A and zinc were observed in 84% and 58%, respectively, of the total study population.

CONCLUSION

RBP concentrations appear to decrease in the presence of long-term DDT uptake, which may have deleterious effects on thyroid function and vitamin A nutritional status. This is of major concern in a population with poor vitamin A and zinc intake.

Urinary vitamin A excretion in very low birth weight infants

Vitamin A (VA) deficiency in very low birth weight (VLBW) infants is associated with an increased risk for disorders related to kidney and lung maturation and function. VA losses through increased urinary retinol (ROH) excretion might contribute to this deficiency risk. The mechanism accounting for ROH loss in the urine has not yet been clarified. The aim of this study was to assess the excretion of ROH, retinol-binding protein 4 (RBP4) and transthyretin (TTR) in urine from VLBW infants in comparison with that in term infants in relation to kidney function. Urine specimens were collected from 15 VLBW infants (birth weight < 1,500 g) as well as from 20 term infants during the first 2 days after birth. ROH in urine was detectable in 14 of the 15 VLBW infants at a median concentration of 234 nmol/g creatinine. In the group of term infants, 17 of the 20 excreted ROH, but at an approximately five-times lower concentration (P < 0.001). Excretion of RBP4 and TTR was also much higher in VLBW infants (both P< 0.001). The urinary ROH excretion in VLBW infants may be related to the impaired tubular handling of its carrier proteins RBP4 and TTR. Thus, ROH excretion might contribute to an increased risk of VA deficiency, especially in VLBW infants.

High-normal C-reactive protein levels do not affect the vitamin A transport complex in serum of children and adolescents with type 1 diabetes

Type 1 diabetes is associated with the presence of inflammation, which in turn affects parameters used to assess the vitamin A status. In the present study, we evaluated the influence of inflammatory status on retinol, retinol-binding protein 4 (RBP4), and transthyretin (TTR) in children and adolescents with type 1 diabetes. A total of 40 children with type 1 diabetes (median age, 14.2 y; median BMI-SDS, 0.53; median diabetes duration, 5.8 y; median HbA1c, 7.3%) and 46 healthy subjects (median age, 12.8 y; median BMI-SDS, 0.34; median HbA1c 5.4%) were recruited. Serum levels of CRP were significantly elevated (p = 0.005) and retinol concentrations were significantly lower (p = 0.02) in children and adolescents with type 1 diabetes compared with healthy subjects. Serum RBP4 and TTR showed no differences between the groups. Healthy children with CRP levels above 0.6 mg/L had significant lower levels of retinol (p = 0.03). This was not observed in children with type 1 diabetes. The results suggest that, in contrast to healthy children, minor CRP elevation does not affect vitamin A transport complex in serum of children with type 1 diabetes.

Assessment of vitamin A nutritional status in newborn preterm infants

OBJECTIVE

This study assessed the vitamin A nutritional status of preterm infants determined by the vitamin A relative dose-response test (RDR) compared with serum levels of vitamin A, retinol-binding protein (RBP), transthyretin (TTR), and retinol relations with carrier proteins.

METHODS

Serum levels of retinol, RBP, and TTR and retinol/RBP, retinol/TTR, and RBP/TTR molar ratios were determined in 120 infants at 7 d and in 92 at 28 d. For the determination of the performance of the tests, the RDR was considered the reference method. The sensitivity and specificity for all possible cutoff values were determined by constructing receiver operator characteristic curves. The areas under the curves were used to estimate the overall accuracy of the tests. The best cutoff values to be used for the calculation of sensitivity and specificity were determined with 95% confidence intervals.

RESULTS

RDR indicated vitamin A deficiency in 60% of the infants at 7 d and in 51.1% at 28 d. In the receiver operator characteristic curves, the best area under the curve was 0.710 obtained for serum retinol at 28 d of postnatal age and considered moderately accurate. The least inadequate cutoff level was set at 25 mg/dL, but no value was considered adequate due to low sensitivity and/or low specificity.

CONCLUSION

Compared with RDR, the determination of serum levels of retinol, RBP, and TTR and their molar ratios are not adequate to assess nutritional vitamin A status in preterm infants.

Use of the retinol-binding protein : transthyretin ratio for assessment of vitamin A status during the acute-phase response

The ratio plasma retinol-binding protein (RBP) : transthyretin (TTR) has been proposed as a means to improve the assessment of vitamin A status of individuals with concurrent infection or inflammation. We have measured RBP and TTR in stored sera from South African children who had accidentally ingested kerosene. Samples were collected from these children in hospital when suffering acute inflammation and respiratory distress, and from them and neighbourhood control children 3 months later. Vitamin A status was defined by modified relative dose response (MRDR) tests of liver retinol stores at 3 months and by serum retinol concentration both when children were ill and when they were well. Illness was defined as either being in hospital or, at follow-up, as having a raised plasma α1-acid glycoprotein (AGP) level. The RBP : TTR value was significantly decreased by both illness and low liver retinol stores. When the effects on RBP : TTR of illness and vitamin A stores were considered together for the 3-month follow-up samples, only vitamin A status significantly decreased the value. We calculated sensitivity and specificity of the RBP : TTR ratio against established measures of vitamin A status using a cut-off value of 0·3 for RBP : TTR and standard cut-off values for MRDR (0·06) and plasma retinol (0·7 μmol/l). Compared with MRDR, RBP : TTR had sensitivities of 76 % and 43 % and specificities of 22 % and 81 % to detect vitamin A deficiency in hospitalized and well children respectively. Compared with plasma retinol, sensitivities were 88 % and 44 % and specificities were 55 % and 64 % in hospitalized and well children respectively. Only for the case of clinically well children with biochemical evidence of subclinical inflammation did sensitivity (62 % and 100 % against MRDR and plasma retinol respectively) and specificity (100 % and 60 % against MRDR and retinol) approach useful levels for an assessment tool. Overall, although a trend supporting the theory behind the use of the RBP : TTR for assessment of vitamin A status in infection was observed in the current study, the ratio did not provide adequate sensitivity and specificity to be a useful assessment tool.

Vitamin A supplementation in children with poor vitamin A and iron status increases erythropoietin and hemoglobin concentrations without changing total body iron

BACKGROUND

Vitamin A deficiency impairs iron metabolism; vitamin A supplementation of vitamin A-deficient populations may reduce anemia. The mechanism of these effects is unclear. In vitro and in animal models, vitamin A treatment increases the production of erythropoietin (EPO), a stimulant of erythropoiesis.

OBJECTIVE

We measured the effect of vitamin A supplementation on hemoglobin, iron status, and circulating EPO concentrations in children with poor iron and vitamin A status.

DESIGN

In a double-blind, randomized trial, Moroccan schoolchildren (n = 81) were given either vitamin A (200,000 IU) or placebo at baseline and at 5 mo. At baseline, 5 mo, and 10 mo, hemoglobin, indicators of iron and vitamin A status, and EPO were measured.

RESULTS

At baseline, 54% of children were anemic; 77% had low vitamin A status. In the vitamin A group at 10 mo, serum retinol improved significantly compared with the control group (P < 0.02). Vitamin A treatment increased mean hemoglobin by 7 g/L (P < 0.02) and reduced the prevalence of anemia from 54% to 38% (P < 0.01). Vitamin A treatment increased mean corpuscular volume (P < 0.001) and decreased serum transferrin receptor (P < 0.001), indicating improved iron-deficient erythropoiesis. Vitamin A decreased serum ferritin (P < 0.02), suggesting mobilization of hepatic iron stores. Calculated from the ratio of transferrin receptor to serum ferritin, overall body iron stores remained unchanged. In the vitamin A group at 10 mo, we observed an increase in EPO (P < 0.05) and a decrease in the slope of the regression line of log10(EPO) on hemoglobin (P < 0.01).

CONCLUSION

In children deficient in vitamin A and iron, vitamin A supplementation mobilizes iron from existing stores to support increased erythropoiesis, an effect likely mediated by increases in circulating EPO.

Plasma alpha1-acid glycoprotein can be used to adjust inflammation-induced hyporetinolemia in vitamin A-sufficient, but not vitamin A-deficient or -supplemented rats

We examined the association between alpha(1)-acid glycoprotein (AGP), all-trans-retinol (retinol), and albumin concentrations in a longitudinal animal model of IL-6-induced inflammation. Vitamin A-sufficient (VAS) male Sprague-Dawley rats were administered recombinant human IL-6 [n = 4, 65 mug/(kg.d)] or PBS (n = 4) continuously for 7 d via osmotic minipumps. Plasma samples were obtained daily and concentrations of retinol, AGP, albumin, and total protein were measured. Compared with both baseline and controls, retinol and albumin decreased (P < 0.05), AGP increased (P < 0.05), and total protein concentrations were unaffected in IL-6-treated rats. In vitamin A-deficient (VAD) rats, AGP concentrations were significantly lower at all time points and increased only to one-third of that in VAS rats. The AGP cut-off value indicative of inflammation was 0.11 g/L (i.e., 95% upper limit of baseline concentrations). After 20.5 h, there was an inverse linear correlation between AGP concentrations and the relative change in retinol to baseline (y = -0.18x + 0.48, r = -0.84, P < 0.001). However, changes in AGP and albumin were not correlated (P = 0.94). The application of this function to retinol concentrations in rats from separate experiments showed that hyporetinolemia cannot be adjusted using plasma AGP in VAD or vitamin A-supplemented rats. In conclusion, correcting inflammation-induced hyporetinolemia using an acute-phase protein requires longitudinally derived data, knowledge of vitamin A status, and a common underlying mechanism of change.

HIV-1 infection alters the retinol-binding protein:transthyretin ratio even in the absence of the acute phase response

The ratio of retinol-binding protein (RBP) to transthyretin (TTR) has been proposed as an indirect method with which to assess vitamin A status in the context of inflammation. Few studies have been conducted among adults, and none examined the effect of HIV-1 infection. Our goal was to assess the RBP:TTR ratio among adults, including the effects of HIV-1 and the acute phase response. We used data from a cross-sectional study of 600 Kenyan women, of whom 400 had HIV-1. The effect of vitamin A supplementation among the HIV-1-infected participants was subsequently assessed in a randomized trial. Among HIV-1-uninfected women without an acute phase response, a RBP:TTR cut-off value of 0.25 had approximately 80% sensitivity and specificity to detect vitamin A deficiency (retinol <0.70 micromol/L). No RBP:TTR cut-off value demonstrated both high sensitivity and specificity among HIV-1 infected women without evidence of inflammation. HIV-1 infection and advanced HIV-1 disease were associated with higher RBP:TTR ratios. The effect of HIV-1 was independent of the acute phase response, which also increased the RBP:TTR ratio. Serum retinol increased with vitamin A supplementation among those with a low RBP:TTR ratio, although the effect was small and was not present among those with concurrent inflammation. Thus, the RBP:TTR ratio has modest ability to predict vitamin A deficiency among healthy adults, but HIV-1 infection alters the ratio, even in the absence of the acute phase response. Our results raise questions about the utility of this measurement given the high prevalence of HIV-1 infection in areas where vitamin A deficiency is common.

Retinol-binding protein, transthyretin, and C-reactive protein in extremely low birth weight (ELBW) infants

BACKGROUND

Vitamin A deficiency reduces retinol binding protein (RBP) but not transthyretin (TTR), while inflammation reduces both RBP and TTR and increases C-reactive protein (CRP), an acute phase reactant.

OBJECTIVE

To estimate serum RBP, TTR, and CRP in ELBW infants to test the hypotheses that (a) TTR is a negative acute phase reactant and (b) a higher RBP/TTR ratio or CRP is associated with death/BPD by 36 weeks corrected age.

DESIGN/METHODS

Serum RBP, TTR, and CRP were measured in 79 ELBW infants at 28 days. Area under the curve (AUC) of receiver operating characteristic curve analysis evaluated the predictive value of TTR, the RBP/TTR ratio, and CRP for death/BPD at 36 weeks.

RESULTS

(1) TTR inversely correlated with CRP (r=-0.45, p<0.0001) consistent with TTR being a negative acute phase reactant. (2) The RBP/TTR ratio predicted death/BPD (AUC 0.68 (CI 0.57 to 0.78)). (3) CRP strongly predicted death/BPD (AUC 0.85 (CI 0.76 to 0.92)), even after exclusion of sepsis.

CONCLUSIONS

A higher CRP and RBP/TTR molar ratio on day 28 are associated with death/BPD at 36 weeks in ELBW infants. Lower TTR and maintained RBP/TTR ratios suggest inflammation rather than vitamin A deficiency as the cause for lower serum vitamin A levels in ELBW infants..

Low plasma retinol concentrations increase the risk of developing bronchopulmonary dysplasia and long-term respiratory disability in very-low-birth-weight infants

BACKGROUND

The effect of inadequate vitamin A during the neonatal period on lung status is still unknown.

OBJECTIVE

We tested the hypothesis that low plasma retinol concentrations during the first month of life are independently associated with bronchopulmonary dysplasia (BPD) and long-term respiratory morbidity at 6 mo gestationally corrected age (ie, the age the infant would be had the pregnancy gone to term).

DESIGN

Respiratory outcome information was obtained to 6 mo corrected age for a historical cohort of very-low-birth-weight neonates (<1250 g) who were admitted to intensive care over a 7-y period. Neonates with one or more plasma measurements of retinol concentrations < 0.35 micromol/L (<100 microg/L) on days 1-28 were classified as having low vitamin A. BPD was defined at day 28 by clinical and radiologic criteria and by use of supplemental oxygen at 36 wk postmenstrual age (PMA). Dependence on supplemental oxygen was used to identify long-term respiratory disability at 6 mo corrected age. Multivariate logistic regression analyses were conducted.

RESULTS

Of the 350 study infants, 192 (55%) had low vitamin A status. BPD occurred in 52% of survivors at day 28 (173/331) and at 36 wk PMA (147/285). Fourteen percent (33/244) required oxygen support at 6 mo corrected age. Adjusted odds ratios of BPD with low vitamin A were 3.5 (95% CI: 1.7, 7.2) at day 28 and 1.7 (1.0, 2.7) at 36 wk PMA. At 6 mo corrected age, the adjusted odds ratio was 2.6 (1.1, 6.4) for respiratory disability with low vitamin A.

CONCLUSION

Poor vitamin A status during the first month of life significantly increased the risk of developing BPD and long-term respiratory disability.

Triple fortification of salt with microcapsules of iodine, iron, and vitamin A

BACKGROUND

In many developing countries, children are at high risk of goiter, vitamin A deficiency, and iron deficiency anemia.

OBJECTIVE

We aimed to develop a stable, efficacious salt fortified with iodine, iron, and vitamin A.

DESIGN

A novel spray-cooling technique was used with hydrogenated palm oil to package potassium iodate, micronized ferric pyrophosphate, and retinyl palmitate into microcapsules (mean particle size: 100 mum). We used the microcapsules to create triple-fortified salt (TFS) with 30 mug I, 2 mg Fe, and 60 mug vitamin A/g salt. After storage trials, we compared the efficacy of TFS with that of iodized salt in a 10-mo, randomized, double-blind trial in goitrous schoolchildren (n = 157) who had a high prevalence of vitamin A deficiency and iron deficiency anemia.

RESULTS

After storage for 6 mo, losses of iodine and vitamin A from the TFS were approximately 12-15%, and color was stable. In the TFS group, mean hemoglobin increased by 15 g/L at 10 mo (P < 0.01), iron status indexes and body iron stores improved significantly (P < 0.05), and mean serum retinol, retinol-binding protein, and the ratio of retinol-binding protein to prealbumin increased significantly (P < 0.01). At 10 mo, prevalences of vitamin A deficiency and iron deficiency anemia were significantly lower in the TFS group than in the iodized salt group (P < 0.001).

CONCLUSION

Newly developed microcapsules containing iodine, iron, and vitamin A are highly stable when added to local African salt. TFS was efficacious in reducing the prevalence of iron, iodine, and vitamin A deficiencies in school-age children.

The effects of vitamin A deficiency and vitamin A supplementation on thyroid function in goitrous children

In developing countries, children are at high risk for both the iodine deficiency disorders (IDD) and vitamin A deficiency (VAD). The study aim was to determine the effects of VAD and vitamin A (VA) supplementation on thyroid function in an area of endemic goiter. In a double-blind, randomized, 10-month trial, Moroccan children with IDD and VAD (n = 138) were given iodized salt and either VA (200,000 IU) or placebo at 0 and 5 months. At 0, 5, and 10 months, measurements of VA status and thyroid function were made. At baseline, increasing VAD severity was a predictor of greater thyroid volume and higher concentrations of TSH and thyroglobulin (P < 0.001). In children with VAD, the odds ratio for goiter was 6.51 (95% confidence interval, 2.94, 14.41). VAD severity was also a strong predictor of higher concentrations of total T(4) (P < 0.001); the odds ratio for hypothyroidism in VAD was 0.06 (95% confidence interval, 0.03, 0.14). During the intervention, mean thyroglobulin, median TSH, and the goiter rate significantly decreased in the VA-treated group compared with those in the placebo group (P < 0.01). The findings indicate that VAD in severely IDD-affected children increases TSH stimulation and thyroid size and reduces the risk for hypothyroidism. This effect could be due to decreased VA-mediated suppression of the pituitary TSHbeta gene. In IDD- and VAD-affected children receiving iodized salt, concurrent VA supplementation improves iodine efficacy.

Inverse gene expression patterns for macrophage activating hepatotoxicants and peroxisome proliferators in rat liver

Macrophage activation contributes to adverse effects produced by a number of hepatotoxic compounds. Transcriptional profiles elicited by two macrophage activators, LPS and zymosan A, were compared to those produced by 100 paradigm compounds (mostly hepatotoxicants) using cDNA microarrays. Several hepatotoxicants previously reported to activate liver macrophages produced transcriptional responses similar to LPS and zymosan, and these were used to construct a gene signature profile for macrophage activators in the liver. Measurement of cytokine mRNAs in the same liver samples by RT-PCR independently confirmed that these compounds are associated with macrophage activation. In addition to expected effects on acute phase proteins and metabolic pathways that are regulated by LPS and inflammation, a strong induction was observed for many endoplasmic reticulum-associated stress/chaperone proteins. Additionally, many genes in our macrophage activator signature profile were well-characterized PPARalpha-induced genes which were repressed by macrophage activators. A shared gene signature profile for peroxisome proliferators was determined using a training set of clofibrate, WY 14643, diethylhexylphthalate, diisononylphthalate, perfluorodecanoic acid, perfluoroheptanoic acid, and perfluorooctanoic acid. The signature profile included macrophage activator-induced genes that were repressed by peroxisome proliferators. NSAIDs comprised an interesting pharmacological class in that some compounds, notably diflunisal, co-clustered with peroxisome proliferators whereas several others co-clustered with macrophage activators, possibly due to endotoxin exposure secondary to their adverse effects on the gastrointestinal system. While much of these data confirmed findings from the literature, the transcriptional patterns detected using this toxicogenomics approach showed relationships between genes and biological pathways requiring complex analysis to be discerned.

Metabolic effects of acute measles in chronically malnourished Nigerian children

We hypothesized that acute measles infection imposes severe metabolic demands on malnourished children. Nigerian rural communities, characterized by severe poverty and extensive malnutrition, served as site for this study. Sixty-five children (mean [+/-SD] age 2.67 +/- 1.96 years) with measles and a randomly selected equal number of children (age 2.83 +/- 1.23 years) from the same communities but measles-free were studied. Both groups were serologically negative for human immunodeficiency virus. The percentages of nonmeasles group who were underweight and wasted as exemplified by weight for age (WAZ) and weight for height (WHZ) scores less than -2.0 SD were 43% and 23%, respectively. Comparative values for the measles group (66% and 54% respectively) were significantly (P < 0.01 or 0.001) different. Compared to the controls, measles-infected children had significantly (P < 0.001) higher plasma cortisol level, marked hyporetinemia (plasma retinol 0.62 +/- 0.24 micromol/L) and prominent reduction (P < 0.002) in the sum of serum essential amino acids. Measles promoted a TH(1) to TH(2) cytokine shift, with severe depletion of plasma interleukin (IL)-12, a key cytokine in the development of cell mediated immunity. IL-6, a key stimulator of hepatic acute phase protein response, was prominently (P < 0.002) increased in plasma in measles-infected children. Glucocorticoids exert effects on cytokine expression, as well as on cytokine receptor expression and cytokine-regulated biological responses. They enhance synergistically, the effects of IL-1 and IL-6 type cytokines on many acute phase proteins. Because of the prominent increase in circulating level of cortisol in acute measles, glucocorticoid treatment for associated sepsis may pose serious problems. Additionally, glucocorticoids antagonize several effects of retinoids at cellular and transcriptional levels, thus suggesting that hypercortisolemia may increase the requirement for retinoids.

Assessing vitamin A status: past, present and future

Xerophthalmia classification was traditionally used to identify populations with vitamin A deficiency. Currently, night blindness and dark adaptometry have been proposed as population assessment methods. While eye signs and function tests are still used in areas where vitamin A deficiency is severe, a subclinical vitamin A deficiency is more prevalent. Serum and breast milk retinol concentrations are used to identify vitamin A deficiency risk. However, in healthy individuals, serum retinol concentrations are homeostatically controlled and do not begin to decline until liver reserves of vitamin A are dangerously low. Moreover, serum retinol and retinol binding protein (RBP) concentrations fall during times of infection. The RBP:transthyretin ratio may help to determine if serum retinol concentrations are depressed by infection. Other methods better reflect liver reserves of vitamin A, the "gold" standard. The relative dose response and modified relative dose response tests involve giving a small dose of retinyl or dehydroretinyl ester, respectively, and determining a response in the serum at about 5 h. A new response test where retinoyl beta-glucuronide is administered and the degree of hydrolysis to retinoic acid is measured has been investigated. Unlike isotope dilution tests, the dose response tests lack utility in defining the total body reserve of vitamin A. The deuterated retinol isotope dilution test has been used in several different groups. Recently, a new isotope assay was developed using 13C-retinyl acetate and gas chromatography-combustion-isotope ratio mass spectrometry for analysis. Thus, having many choices of vitamin A assessment methods, laboratory sophistication and resources available will usually dictate which methods are chosen.

Assessment of vitamin A status with the relative-dose-response test in Peruvian children recovering from pneumonia

BACKGROUND

The relative-dose-response (RDR) test is used to identify subjects with marginal liver vitamin A stores, but its use has not been evaluated during episodes of infection.

OBJECTIVE

The objective was to assess, with the RDR test, the vitamin A status of children recovering from pneumonia.

DESIGN

As part of a double-blind, placebo-controlled clinical trial of high-dose vitamin A supplements among children hospitalized with pneumonia in Lima, Peru, we examined the association of treatment group, nutritional status, severity of disease, and induction of the acute phase response [on the basis of serum C-reactive protein (CRP)] on serum retinol and the RDR test.

RESULTS

Serum retinol was low at admission and increased significantly in both the vitamin A and placebo groups during recovery. Serum CRP had a significant, inverse association with retinol at both admission and discharge. Serum retinol and CRP concentrations never differed significantly between the treatment groups. Among subjects with CRP > or =10 mg/L, 21% in the vitamin A group and 20% in the placebo groups (P = 0.83) had a positive RDR test result. Among subjects with CRP <10 mg/L, 56% in the placebo group but only 6% in the vitamin A group had positive RDR test results (P = 0.002).

CONCLUSION

The RDR test was useful in assessing the vitamin A status of children recovering from pneumonia when CRP concentrations were <10 mg/L but not when CRP concentrations were higher.

Determination of a cut-off value for the molar ratio of retinol-binding protein to transthyretin (RBP:TTR) in Bangladeshi patients with low hepatic vitamin A stores

The purpose of this study was to determine a cut-off value of the molar ratio of retinol-binding protein to transthyretin (RBP:TTR) to indicate marginal vitamin A (VA) deficiency. Plasma RBP and TTR were measured by radial immunodiffusion in two groups of patients, i.e., surgical patients with known hepatic VA stores, and a cohort of children residing in a malaria-endemic area of Papua New Guinea who had received placebo or 210 micro mol of VA every 3 mo for 9 mo. A RBP:TTR ratio < or =0.36 selectively detected five of seven patients (71% sensitivity) with hepatic VA stores < or =69.9 nmol/g of tissue (i.e., < or =20 micro g/g), indicative of marginal VA deficiency. Using this cut-off value, 28% (n = 245) of children from Papua New Guinea had marginal VA deficiency before supplementation. After 7 mo, a low ratio persisted in 29% (n = 92) of placebo-treated children but in only 11% (n = 83) of those receiving VA supplements (chi(2), P < 0.01). At the end of the study, 13 mo after initiation or 4 mo after the last dose of VA, the percentage of children with a low ratio was still lower (chi(2), P < 0.02) in the VA group, 42.5% (n = 113) than in the placebo group, 58.6% (n = 118). These results demonstrate that a cut-off value < or =0.36 is indicative of marginal VA deficiency and can be used as an indirect method of VA assessment.

Vitamin a supplementation of vitamin a deficient measles patients lowers the risk of measles-related pneumonia in zambian children

This is an a posteriori analysis of previously published data to assess whether improving vitamin A (VA) status resolves measles-related pneumonia (MP). Nonhospitalized acute measles patients (2 d of rash onset) had their VA status determined based on the molar ratio of retinol-binding protein to transthyretin (RBP/TTR). Using a cutoff value of </=0.36, indicative of marginal VA deficiency, 82 children were diagnosed as marginally VA deficient and 114 were diagnosed as VA sufficient. At baseline, marginally VA-deficient patients had significantly lower serum retinol and higher serum C-reactive protein concentrations than VA-sufficient children. At the 2-wk follow-up visit, serum retinol and the RBP/TTR ratio were significantly greater in marginally VA-deficient measles patients receiving VA supplements than in those receiving placebo; whereas in VA-sufficient measles patients, retinol increased in those receiving VA supplements or placebo. Concomitantly the odds ratio of unresolved pneumonia in marginally VA-deficient measles patients receiving VA supplements compared with those receiving placebo was 0.20 (95% confidence interval, 0.05-0.71). In conclusion, VA supplements during measles infection improved VA status of VA-deficient children and helped resolve MP, demonstrating the importance of determining VA status when assessing the efficacy of VA supplements.

The molar ratio of retinol-binding protein to transthyretin in the assessment of vitamin A status in adults. Proposal of a cut-off point

The molar ratio of retinol-binding protein to transthyretin (RBP:TTR) has been proposed as an indirect method to assess vitamin A status in children with inflammation. Neither reference values nor appropriate cut-off point are available for adults. RBP, TTR and retinol were determined in plasma from 100 healthy adults and 31 low-risk surgical patients with no inflammatory response. RBP:TTR percentile distribution from 99 healthy adults with plasma retinol > or = 0.7 micromol/l was: 2.5th = 0.24; 5th = 0.31; 10th = 0.32; 25th = 0.41; 50th = 0.47; 75th = 0.54; 90th = 0.67; 95th = 0.78 and 97.5th = 0.81. In order to define a cut-off point, receiver operating characteristic (ROC) curve was constructed, using plasma retinol as gold standard. ROC curve was based on data from the 131 studied subjects, 11 of whom (8.4%) were classified as deficient on the basis of plasma retinol < 0.7 pmol/l. According to ROC curve criteria, RBP:TTR ratio was considered a good test, the area under the curve being 0.822, p < 0.001. A cut-off-point of < or = 0.37 is proposed to detect vitamin A deficiency in adults, since it allows reaching high sensitivity (81.8%), specificity (79.2%) and predictive value (79.4%). The proposed cut-off point falls between 13th and 14th percentiles.

Vitamin A deficiency promotes bronchial hyperreactivity in rats by altering muscarinic M(2) receptor function

Vitamin A deficiency (VAD) remains an important health problem among children in developing countries. Children living in these areas have a higher mortality from respiratory infections, which likely results in part from suboptimal nutrition, including VAD. Bronchial hyperreactivity can follow viral respiratory infections and may complicate the recovery. To investigate whether VAD promotes bronchial hyperreactivity, we have assessed methacholine-induced bronchoconstriction in VAD and vitamin A-sufficient rats. Bronchial constriction developed at lower concentrations of inhaled methacholine in VAD than in vitamin A-sufficient rats. This did not result from an increase in the bronchial wall thickness or the clearance of a small molecule (with a size similar to methacholine) from the air space. The function and abundance of the muscarinic M(2) receptors in bronchial tissue were reduced in VAD rats, suggesting that this receptor may contribute to these animals' diminished ability to limit cholinergic-mediated bronchoconstriction. A similar reduction in muscarinic M(2) receptor function has been observed in asthma. Vitamin A (retinol) and its congeners (retinoids) may be required to regulate bronchial responsiveness in addition to maintaining a normal bronchial epithelium.

Vitamin A, infection, and immune function

In populations where vitamin A availability from food is low, infectious diseases can precipitate vitamin A deficiency by decreasing intake, decreasing absorption, and increasing excretion. Infectious diseases that induce the acute-phase response also impair the assessment of vitamin A status by transiently depressing serum retinol concentrations. Vitamin A deficiency impairs innate immunity by impeding normal regeneration of mucosal barriers damaged by infection, and by diminishing the function of neutrophils, macrophages, and natural killer cells. Vitamin A is also required for adaptive immunity and plays a role in the development of T both-helper (Th) cells and B-cells. In particular, vitamin A deficiency diminishes antibody-mediated responses directed by Th2 cells, although some aspects of Th1-mediated immunity are also diminished. These changes in mucosal epithelial regeneration and immune function presumably account for the increased mortality seen in vitamin A-deficient infants, young children, and pregnant women in many areas of the world today.

The molar ratio of serum retinol-binding protein (RBP) to transthyretin (TTR) is not useful to assess vitamin A status during infection in hospitalised children

OBJECTIVE

To assess the usefulness of the molar ratio of serum retinol-binding protein (RBP) to transthyretin (TTR) to determine vitamin A (VA) status during infection.

DESIGN

We took advantage of previously collected data during a randomised double-blind, placebo-controlled clinical trial to conduct a secondary analysis of the RBP/TTR ratio and its relationship to infection and VA status. In this clinical trial, children were randomly assigned to one of three groups and received either one single oral high dose of VA (200 000 IU) on the day of admission and subsequently a placebo daily until discharge or daily oral low doses of VA (5000 IU) from admission until discharge or a placebo daily from admission until discharge.

SETTING

Lwiro pediatric hospital, Province of South Kivu, Democratic Republic of Congo.

SUBJECTS

A total of 900 children aged 0-72 months hospitalised consecutively between March 1994 and March 1996.

MAIN OUTCOME MEASURES

RBP/TTR molar ratio after 7 days hospitalisation.

RESULTS

After 7 days hospitalisation, molar RBP:TTR ratio (mean+/-s.d.) of infected children (C-reactive proteins>10 mg/l) was 0.67+/-0.31 in the high-dose group (n=81), 0.74+/-0.44 in the low dose group (n=71) and 0.73+/-0.39 in the placebo group (n=81). These values did not differ significantly (one-way ANOVA P=0.472). In patients with baseline serum retinol concentrations<0.70 micromol/l, changes in RBP:TTR ratio between admission and day 7 were not statistically different in the three groups (one-way ANOVA P=0.548).

CONCLUSIONS

In this population of malnourished hospitalised children, molar RBP:TTR ratio does not appear to be useful to assess VA status during infection.

SPONSORSHIP

Our research was partially supported by a grant from the Fonds de la Recherche Scientifique et Médicale (contract 3.4505.94) and the David and Alice Van Buuren Foundation.

Inflammation-induced changes in the nutritional biomarkers serum retinol and carotenoids

Inflammation causes a decrease in serum retinol and carotenoids as a consequence of the acute phase response of the organism. Under normal conditions both the acute phase response and the alterations in dynamics of retinol and carotenoids are transient. For both retinoids and carotenoids the adaptive benefit or the principal mechanism causing this decrease are not clear. Because nutritional deficiency results in a similar decrease of these nutritional biomarkers, it is necessary to be able to differentiate between inflammation or nutrition deficiency as the cause. This is of importance with regard to the supplementation of both critically ill patients and populations with a high infection load. The review covers several very recent publications shedding new light on and expanding our knowledge of the interaction between inflammation and the decrease in serum retinol and carotenoids.

Vitamin A: recent advances in the biotransformation, transport, and metabolism of retinoids

Advances in vitamin A research in 1999 and 2000 have improved the understanding the molecular processes through which beta-carotene and other provitamin A carotenoids are converted to vitamin A, the roles of cellular retinoid-binding proteins that serve as retinoid chaperones during metabolism, the regulation of retinoid transport, and the nature and regulation of several enzymes required for the absorption, storage, activation, and inactivation or degradation of retinoids. Not only has a clearer picture emerged of specific molecular processes, but it is also becoming evident that whole-body retinoid homeostasis is facilitated by close communication among organs due to the rapid interorgan recirculation of retinoids, and by the "autoregulation" by retinoic acid of several enzymes and retinoid-binding proteins that mediate retinoid homeostasis.