Liver Vitamin A Research Articles

Vitamin D Maintains Growth and Bone Mineral Density against a Background of Severe Vitamin A Deficiency and Moderate Toxicity in a Swine Model.

Excessive vitamin A (VA) negatively impacts bone. Interactions between VA and vitamin D (VD) in bone health are not well-understood. This study used a traditional two-by-two factorial design. Pigs were weaned and randomized to four treatments (n = 13/group): -A-D, -A+D, +A-D, and +A+D for 3 and 5 wk. Serum, liver, kidney, adrenal glands, spleen, and lung were analyzed by ultra-performance LC. Growth was evaluated by weight measured weekly and BMD by DXA. Weights were higher in -A+D (18.1 ± 1.0 kg) and +A+D (18.2 ± 2.3 kg) at 5 wk than in -A-D (15.5 ± 2.1 kg) and +A-D (15.8 ± 1.5 kg). Serum retinol concentrations were 0.25 ± 0.023, 0.22 ± 0.10, 0.77 ± 0.12, and 0.84 ± 0.28 µmol/L; and liver VA concentrations were 0.016 ± 0.015, 0.0065 ± 0.0035, 2.97 ± 0.43, 3.05 ± 0.68 µmol/g in -A-D, -A+D, +A-D, and +A+D, respectively. Serum 25(OH)D3 concentrations were 1.5 ± 1.11, 1.8 ± 0.43, 27.7 ± 8.91, and 23.9 ± 6.67 ng/mL in -A-D, +A-D, -A+D, +A+D, respectively, indicating a deficiency in -D and adequacy in +D. BMD was highest in +D (p < 0.001). VA and the interaction had no effect on BMD. Dietary VD influenced weight gain, BMD, and health despite VA status.

56 Metabolic status of respiratory disease challenged beef steers altered by intranasal Zn and vitamin A treatments

Abstract Bovine respiratory disease (BRD) is a major cause of morbidity and mortality in the cattle industry. Increasing the ability of a calf to respond to disease is of interest due to the loss of production during disease. Zinc and vitamin A (VA) are key micronutrients involved in many immunologic processes such as cell signaling and mucosal immunity. Angus crossbred steers [n = 48; body weight (BW) = 333 ± 4.2 kg] were utilized in this 14-d BRD challenge investigating intranasal (IN) treatments of Zn and VA. Steers were split into two groups (n = 24) with identical disease challenge and sample collection schedules. Before disease challenge, steers were housed at the Iowa State University Beef Nutrition farm (BNF). Steers were weighed on d -2 and -1 of viral challenge and trucked for 6 h before delivery to the Iowa State University Animal Resource Station. On d 0, steers were challenged with an aerosol inoculation with 104 TCID50 BRSV followed by 5x108 CFU of Mannheimia haemolytica on d 5. On d 4, steers received IN treatments of Zn (ZN; ZnO nanoparticles), VA (VA), Zn and VA (VA+ZN), or control with no IN treatment (CON). For trace mineral and VA analysis, liver biopsies were collected on d -9 and 20 and plasma collected on d 0, 4 (trace mineral only), 5, 7 and 14. Steers were tested for viral shedding on d 0, 4, 5, 7, 10 and 14. RNA was isolated from bronchioalveolar lavage (BAL) cells (d 0 and 7) for gene expression related to inflammation, VA and trace mineral metabolism. Statistical analysis was completed using the GLIMMIX and MIXED procedures in SAS 9.4. Throughout the study, viral shedding was not affected by intranasal treatment (P ≥ 0.59). There were no group × TRT × day effects for plasma trace minerals (Cu, Zn, Fe) or VA concentrations (P ≥ 0.18). Intranasal VA prevented a decrease in plasma VA on d 5, after which all treatments were similar (P &amp;lt; 0.01). There were no TRT × day effects for plasma Zn and Cu (P ≥ 0.50). Post challenge, liver VA was increased in VA treated steers compared with steers not treated with VA (P = 0.04). Liver Mn tended to be increased post challenge in IN ZN treated steers (P = 0.08). IN Zn treated steers tended to have lesser expression of IL-10 in BAL cells on d 7 post infection (P = 0.07). Local IN supplementation of Zn and VA can have systemic and local affects on respiratory disease challenged steers and may support increased response to disease.

Analysis of published and clinical sample data to develop new ranges of liver and blood concentrations of vitamin A for diagnosis of vitamin A deficiency in cattle

In cattle, liver stores of vitamin A (VA) maintain blood VA concentrations until liver supplies are nearly exhausted, pro­viding VA to tissues during insufficient dietary intake. There­fore, normal blood levels do not indicate adequate VA, but low blood levels indicate a deficiency. We hypothesized that previous diagnostic criteria for VA deficiency needed updating and that blood levels of VA could be used as indicators of liver VA deficiency. We performed multiple regressions of paired blood and liver sample data from published experimental and field case reports of VA deficiency in cattle to demonstrate this. We fitted various models using data from unpaired clini­cal samples submitted to the Iowa State University Diagnostic Laboratory by comparing fractiles of liver and plasma/serum samples. Using these relationships, we propose new ranges for severely deficient, deficient, marginal and adequate, and we also propose that blood samples alone can be used to di­agnose deficiency in the presence of clinical signs of VA defi­ciency. Veterinary diagnostic laboratories can use this infor­mation to better estimate serum and liver VA concentrations for unpaired data and recommend to cattle practitioners the status of VA in their herds.

Hepatic Vitamin A Concentrations and Association with Infectious Causes of Child Death

To assess postmortem vitamin A (VA) concentrations in children under 5years of age and evaluate the association between VA deficiency (VAD) and infectious causes of death (CoD). In this cross-sectional study from the Child Health and Mortality Prevention Surveillance (CHAMPS) Network, liver biopsies collected within 72hours of death were analyzed from 405 stillbirths and children under 5years in Kenya and South Africa. Total liver VA (TLVA) concentrations were quantified using ultra-performance liquid chromatography, and cutoffs of ≤0.1μmol/g, >0.1 to <0.7μmol/g, ≥0.7 to <1.0μmol/g, and ≥1.0μmol/g were used to define VAD, adequate VA status, high VA, and hypervitaminosis A, respectively. CoD were determined by expert panel review. Among 366 liver samples with viable extraction, pooled prevalences of VAD, adequacy, high VA, and hypervitaminosis were 34.2%, 51.1%, 6.0%, and 8.7%, respectively. VAD was more common among neonates compared with stillbirths, infants, or children, and among those with low birthweight (LBW), underweight, or stunting (P<.05). When adjusting for site, age, and sex, there was no significant association of VAD with increased infectious CoD (OR 1.9, 95% confidence interval [CI] 0.9, 3.8, P=.073). In stratified analyses, VA deficient boys, but not girls, had an increased risk of infectious CoD (OR 3.4, 95% CI 1.3, 10.3, P=.013). Definitive postmortem assessment of VA status identified both VAD and VA excess among children under 5years of age in Kenya and South Africa. VAD in boys was associated with increased risk of infectious mortality. Our findings may inform a transition from universal VA supplementation (VAS) to targeted strategies in certain countries.

Inadequate Niacin Intake Disrupts Growth and Retinol Homeostasis Resulting in Higher Liver and Lower Serum Retinol Concentrations in Male Rats

BackgroundNiacin-derived nicotinamide adenine dinucleotide is an essential cofactor for many dehydrogenase enzymes involved in vitamin A (VA) metabolism. Several countries with high prevalence of VA deficiency rely on maize, a poor source of available niacin, as a dietary staple. ObjectivesThis study evaluated the interaction of dietary niacin on VA homeostasis using male Sprague-Dawley rats, aged 21 d (baseline body weight 88.3 ± 6.6 g). MethodsAfter 1 wk of acclimation, baseline samples were collected (n = 4). Remaining rats (n = 54) were split into 9 groups to receive low tryptophan, VA-deficient feed with 3 different amounts of niacin (0, 15, or 30 mg/kg) and 3 different oral VA doses (50, 350, or 3500 nmol/d) in a 3 × 3 design. After 4 wk, the study was terminated. Serum, livers, and small intestine were analyzed for retinoids using high-performance liquid chromatography. Niacin and metabolites were evaluated with nuclear magnetic resonance. Plasma pyridoxal-P (PLP) was measured with high-performance liquid chromatography. ResultsNiacin intake correlated with serum retinol concentrations (r = 0.853, P < 0.001). For rats receiving the highest VA dose, liver retinol concentrations were lower in the 30-mg/kg niacin group (5.39 ± 0.27 μmol/g) than those in the 0-mg/kg and 15-mg/kg groups (9.18 ± 0.62 and 8.75 ± 0.07 μmol/g, respectively; P ≤ 0.05 for both). This phenomenon also occurred in the lower VA doses (P ≤ 0.05 for all). Growth and tissue weight at endline were associated with niacin intake (P ≤ 0.001 for all). Plasma PLP correlated with estimated niacin intake (r = 0.814, P < 0.001). ConclusionsOptimal niacin intake is associated with lower liver VA and higher serum retinol and plasma PLP concentrations. The extent to which vitamin B intake affects VA homeostasis requires further investigation to determine if the effects are maintained in humans.

Reactive astrocytes targeting with oral vitamin A: Efficient neuronal regeneration for Parkinson's disease treatment and reversal of associated liver fibrosis.

A recent approach to cure neurodegenerative diseases is to reprogram fibroblasts into functioning neurons using multiple exogenous transcription factors (TFs) and micro-RNAs. Administering agents that can endogenously induce these TFs may bypass the limitations of this approach. Astrocytes may represent a part of the extrahepatic-stellate system involved in vitamin-A (VA ) homeostasis. Activated-stellate cells lose their VA -storage capacity, and this was previously applied for hepatic-stellate cells (HSCs) targeting to treat liver fibrosis. Accordingly, it is hypothesized that Parkinson's disease (PD) may be coupled with retinoid depletion that may extract VA from VA -rich-HSCs triggering liver fibrosis. Thus, VA administration may selectively target VA -deficient reactive astrocytes and HSCs. Besides, VA has the regenerative capability and may induce endogenous-TFs generation. Fluorescently labeled VA -coupled liposomes (FLV) were traced using confocal laser microscope in rats with induced PD for detecting brain accumulation and uptake into fluorescently labeled astrocytes. Liver fibrosis associated with PD was assessed biochemically and histopathologically, while VA deficiency was confirmed by assessing retinol-binding protein gene expression in the brain and liver. Multiple VA doses were tested for reversing PD-associated liver fibrosis, generating TFs (involved in reprograming astrocytes/fibroblasts into different neuronal types) and capability of dopaminergic-neurons regeneration. Fluorescently labeled VA -coupled liposomes revealed selective brain accumulation and uptake into astrocytes. PD was associated with significant liver fibrosis and VA deficiency in the brain and liver. Furthermore, VA -medium dose (VAMD) was the optimum one for reversing PD-associated liver fibrosis, generating multiple astrocytes/fibroblasts reprogramming TFs, regenerating dopaminergic neurons, and improving PD. VA -medium dose pursued brain targeting in PD with the potential capability of regenerating neurons and restoring dopaminergic transmission. This may place this therapy as an essential treatment in PD management protocol.

Anthocyanin and Lycopene Contents Do Not Affect β-Carotene Bioefficacy from Multicolored Carrots (Daucus carota L.) in Male Mongolian Gerbils

BackgroundAnthocyanins and carotenoids are phytochemicals that may benefit health through provitamin A carotenoid (PAC), antioxidant, and anti-inflammatory activities. These bioactives may mitigate chronic diseases. Consumption of multiple phytochemicals may impact bioactivity in synergistic or antagonistic manners. ObjectivesTwo studies in weanling male Mongolian gerbils assessed the relative bioefficacy of β-carotene equivalents (BCEs) to vitamin A (VA) with simultaneous consumption of the non-PAC lycopene or anthocyanins from multicolored carrots. MethodsAfter 3-wk VA depletion, 5–6 gerbils were killed as baseline groups. The remaining gerbils were divided into 4 carrot treatment groups; the positive control group received retinyl acetate and the negative control group was given vehicle soybean oil (n = 10/group; n = 60/study). In the lycopene study, gerbils consumed feed varying in lycopene sourced from red carrots. In the anthocyanin study, gerbils consumed feed varying in anthocyanin content sourced from purple-red carrots, and positive controls received lycopene. Treatment feeds had equalized BCEs: 5.59 ± 0.96 μg/g (lycopene study) and 7.02 ± 0.39 μg/g (anthocyanin study). Controls consumed feeds without pigments. Serum, liver, and lung samples were analyzed for retinol and carotenoid concentrations using HPLC. Data were analyzed by ANOVA and Tukey’s studentized range test. ResultsIn the lycopene study, liver VA did not differ between groups (0.11 ± 0.07 μmol/g) indicating no effect of varying lycopene content. In the anthocyanin study, liver VA concentrations in the medium-to-high (0.22 ± 0.14 μmol/g) and medium-to-low anthocyanin (0.25 ± 0.07 μmol/g) groups were higher than the negative control (0.11 ± 0.07 μmol/g) (P < 0.05). All treatment groups maintained baseline VA concentrations (0.23 ± 0.06 μmol/g). Combining studies, serum retinol had 12% sensitivity to predict VA deficiency, defined as 0.7 μmol/L. ConclusionsThese gerbil studies suggested that simultaneous consumption of carotenoids and anthocyanins does not impact relative BCE bioefficacy. Breeding carrots for enhanced pigments to improve dietary intake should continue.

Total Liver Vitamin A Reserves, Determined With 13C2-Retinol Isotope Dilution, are Similar Among Tanzanian Preschool Children in Areas With Low and High Vitamin A Exposure

In Tanzania, some districts have single vitamin A (VA) interventions and others have multiple interventions. There is limited information on total liver VA reserves (TLRs) among preschool children (PSC) in Tanzania. We assessed total body VA stores (TBSs) and TLRs among PSC living in 2 districts with low and high exposures to VA interventions using 13C-retinol isotope dilution. A cross-sectional, health facility-based study was conducted in 2 districts with access to VA supplementation only (low exposure to VA interventions) or multiple interventions (high exposure to VA interventions) to determine TLRs in 120 PSC aged 36-59months. A questionnaire was used to collect data. Height and weight were measured, and the prevalence of undernutrition was based on z-scores. Blood samples were collected for measurement of TBSs, TLRs, retinol, biomarkers of infection and inflammation, and hemoglobin. 13C2-retinyl acetate (1.0μmol) was administered to each child after blood collection, and the second sample was taken 14 days later. Serum was analyzed with HPLC and gas chromatography-combustion-isotope ratio mass spectrometry. Mann-Whitney U test was used to compare medians of nonnormally distributed variables. Pearson χ2 test was used to assess associations between 2 categorical variables. Median TBSs differed between PSC from low-exposure (196 μmol; IQR, 120 μmol) and high-exposure (231 μmol; IQR, 162 μmol) intervention areas (P=0.015). Median TLRs were 0.23 μmol/g liver (IQR, 0.14 μmol/g liver) and 0.26 μmol/g liver (IQR, 0.16 μmol/g liver) from low- and high-exposure areas, respectively, which did not significantly differ (P=0.12). Prevalences of VA deficiency (VAD; ≤0.1μmol/g liver) were 6.3% and 1.7% for PSC from low- and high-exposure areas, respectively. There was no significant difference in VAD (P=0.25). No child had hypervitaminosis A (≥1.0μmol/g liver). TLRs in Tanzanian PSC from 2 districts did not differ between low and high exposures to VA interventions. The majority had adequate VA stores. VAD in the study area presented a mild public health problem.

Breast Milk Retinol Concentrations Reflect Total Liver Vitamin A Reserves and Dietary Exposure in Thai Lactating Women from Urban and Rural Areas

Measuring vitamin A (VA) status during lactation is required to inform dietary recommendations. Limited data exist on VA stores in women. Our objective was to assess VA status in lactating Thai women by measuring total body VA stores (TBSs), serum and breast milk retinol concentrations, and dietary intake. Lactating women (n=94), 6-8 wk postpartum, were enrolled from rural (Ayutthaya) and urban (Bangkok) areas. TBSs were measured by the 13C-retinol isotope dilution (RID) technique using 2.0 μmol 13C-retinyl acetate and a single blood sample 14 d post-dose. Natural 13C-enrichment was determined in nonenrolled women (n=11). Estimated total liver VA reserves (TLRs) were determined using assumptions for lactation. Serum, foremilk, and hindmilk samples were analyzed for retinol by HPLC. Dietary VA intake was assessed by FFQ and 24-h dietary recalls for 3 d. Multiple regression and Pearson correlation were used to evaluate relations. Median VA intakes were 51.8% of 2003 Thai daily recommendations for lactating women, with the majority from animal-source foods. Many women in Ayutthaya consumed liver weekly. Considering TLRs as 50% TBS, 20% and 11% of mothers in Ayutthaya and Bangkok, respectively, showed deficient reserves (≤0.10μmol retinol/g). Median (quartile 1, quartile 3) serum [1.58 (1.34, 1.91) and 1.52 (1.30, 1.70) μmol/L] and milk [1.88 (1.29, 2.95) and 1.74 (0.96, 2.26) μmol/L] retinol in Ayutthaya and Bangkok, respectively, were normal. Women with deficient TLRs showed low milk retinol concentrations (≤1.0μmol/L) and consumed less dietary VA, especially from animal-source foods. Breast milk retinol concentrations, especially hindmilk, demonstrated strong correlation with TBSs and TLRs estimated from the RID test. Approximately 15% of Thai lactating women had deficient TLRs. Breast milk retinol concentrations in conjunction with dietary intake records show potential to screen mothers at risk of VA deficiency to guide interventions.The Thai Clinical Trials Registry number is TCTR20160824001 for the work in Thailand.

Filipino Children with High Usual Vitamin A Intakes and Exposure to Multiple Sources of Vitamin A Have Elevated Total Body Stores of Vitamin A But Do Not Show Clear Evidence of Vitamin A Toxicity

ABSTRACTBackgroundYoung children exposed to high-dose vitamin A supplements (VAS) and vitamin A (VA)–fortified foods may be at risk of high VA intake and high VA total body stores (TBS).ObjectivesTBS and estimated liver VA concentration were compared among children with adequate or high VA intake and different timing of exposure to VAS, and associations between estimated liver VA concentrations and biomarkers of VA toxicity were examined.MethodsChildren 12–18 mo of age (n = 123) were selected for 3 groups: 1) retinol intake >600 µg/d and VAS within the past mo, 2) retinol intake >600 µg/d and VAS in the past 3–6 mo, and 3) VA intake 200–500 µg retinol activity equivalents (RAE)/d and VAS in the past 3–6 mo. Dietary intake data were collected to measure VA intakes from complementary foods, breast milk, and low-dose, over-the-counter supplements. TBS were assessed by retinol isotope dilution, and VA toxicity biomarkers were measured. Main outcomes were compared by group.ResultsMean (95% CI) VA intakes excluding VAS were 1184 (942, 1426), 980 (772, 1187), and 627 (530, 724) µg RAE/d, in groups 1–3, respectively; mean VA intake was higher in groups 1 and 2 compared with group 3 (P < 0.05). Geometric mean (GM) (95% CI) TBS were 589 (525, 661), 493 (435, 559), and 466 (411, 528) µmol, respectively. GM TBS and GM liver VA concentrations were higher in group 1 compared with group 3 (liver VA concentration: 1.62 vs. 1.33 µmol/g; P < 0.05). Plasma retinyl ester and 4-oxo-retinoic acid concentrations and serum markers of bone turnover and liver damage did not indicate VA toxicity.ConclusionsIn this sample, most children had retinol intakes above the Tolerable Upper Intake Level (UL) and liver VA concentrations above the proposed cutoff for “hypervitaminosis A” (>1 µmol/g liver). There was no evidence of chronic VA toxicity, suggesting that the liver VA cutoff value should be re-evaluated. This trial was registered at www.clinicaltrials.gov as NCT03030339.

Chronic and acute hypervitaminosis A are associated with suboptimal anthropometric measurements in a cohort of South African preschool children

Excessive vitamin A (VA) can cause bone resorption and impair growth. Government-mandated VA supplementation (VAS) and adequate intake through dietary fortification and liver consumption led to excessive VA in South African children. We evaluated the relation between VAS and underlying hypervitaminosis A assessed by retinol isotope dilution (RID) with measures of growth and bone turnover in this cohort. Primary outcomes in these children (n=94, 36-60 mo) were anthropometric measurements [height-for-age (HAZ), weight-for-age (WAZ), and weight-for-height (WHZ) z scores], serum bone turnover markers [C-terminal telopeptide of type I collagen (CTX) and N-terminal propeptide of type I procollagen (P1NP)], and inflammation defined as C-reactive protein (CRP; ≥5mg/L) and/or α1-acid glycoprotein (AGP; ≥1g/L). VA status was previously measured by RID-estimated total body VA stores (TBSs) and total liver VA reserves (TLRs), and serum retinol and carotenoid concentrations, before and 4 wk after children were administered 200,000 IU VAS. Serum 25-hydroxyvitamin D3 was measured by ultra-performance LC. In this largely hypervitaminotic A cohort, HAZ, WAZ, and WHZ were negatively associated with increasing TLRs, where TLRs predicted 6-10% of the variation before VAS (P < 0.05), increasing to 14-19% 4 wk after VAS (P < 0.01). Bone resorption decreased after VAS (P < 0.0001), whereas formation was unaffected. Neither CTX nor P1NP were correlated with TLRs at either time. Serum carotenoids were low. One child at each time point was vitamin D deficient (<50nmol/L). CRP and AGP were not associated with growth measurements. Excessive TLRs due to dietary VA intake and VAS are associated with lower anthropometric measures and bone resorption decreased after supplementation. VA supplementation programs should monitor VA status with biomarkers sensitive to TLRs to avoid causing negative consequences in children with hypervitaminosis A. This trial is registered at clinicaltrials.gov as NCT02915731.

Vitamin A–fortified rice increases total body vitamin A stores in lactating Thai women measured by retinol isotope dilution: a double-blind, randomized, controlled trial

Lactating women are at increased risk for vitamin A (VA) deficiency due to demands for breast milk content and limited hepatic stores for women in some countries. Previously, consumption of triple-fortified rice, which included VA, iron, and zinc, successfully improved the VA status of Thai children in whom their total body VA stores (TBSs) were doubled in 2 mo. This study assessed the efficacy of consuming VA-fortified rice, which delivered 500 µg retinol activity equivalents (RAEs)/d, on TBSs and estimated total liver VA reserves (TLRs) in Thai lactating women using the retinol isotope dilution (RID) test. A randomized controlled trial was conducted with 70 lactating women (n=35/group) who received either VA-fortified rice (500 µg RAEs/d) or unfortified rice for 14 wk on weekdays only. Serum retinol concentrations (SRs), C-reactive protein, and TBSs were assessed before and after the intervention. The paired 13C-RID test was used to measure TBSs. After a baseline blood sample, 2.0 µmol [14,15]-13C2-retinyl acetate was administered orally. A follow-up blood sample was drawn 14 d later. The RID test was repeated after the intervention. TBSs increased significantly (P<0.05) in the intervention group from 240 (182, 316) to 331 (251, 447) [geometric means (95% CIs)] µmol retinol, and this change in TBSs was significantly higher (P<0.05) than that in the control group [+52.9 (-74, 453) compared with -4.3 (-106, 275) µmol retinol]. Estimated TLRs indicated a high prevalence of VA deficiency among these lactating women. Initial and final SRs did not differ by group and did not change over the course of the intervention. VA-fortified rice improved the VA status of lactating women by increasing TBSs. A targeted approach to disseminate VA interventions among vulnerable groups should be considered in some contexts. This trial was registered at clinicaltrials.gov as NCT03056625.

Findings in 3 clinical trials challenge the accuracy of the Institute of Medicine’s estimated average requirements for vitamin A in children and women

Vitamin A (VA) estimated average requirements (EARs) for women and children are extrapolated from rats and adult males. The retinol isotope dilution (RID) test can sensitively characterize VA status and intake requirements. These studies evaluated current EARs for children 4-8 y and women 19-30 y old. Zambian children (n=133, ages 5-7 y), US women (n=51, ages 19-27 y), and Indonesian women (n=29, ages 19-30 y) were provided diets or supplements containing 30%-155% of VA EARs for 42-90 d. RID was performed before and after the intervention to quantify changes in total body VA stores (TBSs) and total liver VA reserves (TLRs). Linear regression was performed between VA intake and change in TBSs or TLRs. Baseline mean±SD TLRs were hypervitaminotic in Zambian children (1.13±0.41 μmol VA/g liver), optimal in US women (0.46±0.32 μmol/g VA/g liver), and deficient to marginal in Indonesian women (0.10±0.08 μmol VA/g liver). VA intakes, resulting in no change in TBSs or TLRs, were 185 (95% CI: 18, 288) or 257 (95% CI: 124, 411) and 285 or 330 (CIs undefined) μg retinol activity equivalents (RAE)/d in the Zambian and US trials, respectively, but inconclusive in Indonesian women. The regression was not significant in either group of women. Point estimates of VA intakes to maintain stores were below the current EARs of 275 (children) and 500 (women) μg RAE/d despite the TLRs being higher than the EARs were formulated to maintain (i.e., 0.07 μmol VA/g liver). Interventions based on these EARs may need to be scaled back. Lack of change in VA stores in women taking lower doses may result from physiological adaptation resulting in lower VA utilization. Longer, larger, and controlled studies are needed to accurately define EARs for VA.These trials were registered at Clinicaltrials.gov as NCT04123210 and NCT01814891.

Systematic Review and Meta-Analysis of the Relative Dose-Response Tests to Assess Vitamin A Status

Vitamin A (VA) is an essential nutrient often lacking in the diets of people in developing countries. Accurate biomarkers of VA status are vital to inform public health policy and monitor interventions. The relative dose-response (RDR) and modified-RDR (MRDR) tests are semi-quantitative screening tests for VA deficiency that have been used in Demographic and Health Surveys and VA intervention studies. A systematic review and meta-analysis of sensitivity and specificity were conducted to summarize the physiological evidence to support the RDR tests as methods to assess VA status and investigate the impact of different pathological and physiological states on the tests. A total of 190 studies were screened for inclusion, with 21 studies comparing the RDR tests with the gold-standard biomarker, liver VA concentration (68% and 80% sensitivity and 85% and 69% specificity for the RDR and MRDR, respectively). Nearly all studies with VA interventions in VA-deficient populations demonstrated a response of the tests to VA intake that would be expected to improve VA status. The impacts of chronic liver disease, protein malnutrition, age, pregnancy and lactation, infection and inflammation, and various other conditions were examined in 51 studies. The RDR and MRDR tests were reported to have been used in 39 observational studies, and the MRDR has been used in at least 6 national micronutrient surveys. The RDR and MRDR are sensitive tests for determining population VA status and assessing VA interventions. Although they are robust to most physiological and pathological states, caution may be warranted when using the tests in neonates, individuals with chronic liver disease, and those with protein or iron malnutrition. Research on further improvements to the tests to increase accessibility, such as sampling breast milk instead of blood or using intramuscular doses in subjects with malabsorption, will allow wider adoption. This review was registered with PROSPERO as CRD42019124180.

Overlapping Vitamin A Interventions with Provitamin A Carotenoids and Preformed Vitamin A Cause Excessive Liver Retinol Stores in Male Mongolian Gerbils

Vitamin A (VA) deficiency is a public health problem in some countries. Fortification, supplementation, and increased provitamin A consumption through biofortification are efficacious, but monitoring is needed due to risk of excessive VA intake when interventions overlap. Two studies in 28-36-d-old male Mongolian gerbils simulated exposure to multiple VA interventions to determine the effects of provitamin A carotenoid consumption from biofortified maize and carrots and preformed VA fortificant on status. Study 1 was a 2×2×2 factorial design (n=85) with high-β-carotene maize, orange carrots, and VA fortification at 50% estimated gerbil needs, compared with white maize and white carrot controls. Study 2 was a 2×3 factorial design (n=66) evaluating orange carrot and VA consumption through fortification at 100% and 200% estimated needs. Both studies utilized 2-wk VA depletion, baseline evaluation, 9-wk treatments, and liver VA stores by HPLC. Intestinal scavenger receptor class B member 1 (Scarb1), β-carotene 15,15'-dioxygenase (Bco1), β-carotene 9',10'-oxygenase (Bco2), intestine-specific homeobox (Isx), and cytochrome P450 26A1 isoform α1 (Cyp26a1) expression was analyzed by qRT-PCR in study 2. In study 1, liver VA concentrations were significantly higher in orange carrot (0.69±0.12 μmol/g) and orange maize groups (0.52±0.21 μmol/g) compared with baseline (0.23±0.069 μmol/g) and controls. Liver VA concentrations from VA fortificant alone (0.11±0.053 μmol/g) did not differ from negative control. In study 2, orange carrot significantly enhanced liver VA concentrations (0.85±0.24 μmol/g) relative to baseline (0.43±0.14 μmol/g), but VA fortificant alone (0.42±0.21 μmol/g) did not. Intestinal Scarb1 and Bco1 were negatively correlated with increasing liver VA concentrations (P <0.01, r2=0.25-0.27). Serum retinol concentrations did not differ. Biofortified carrots and maize without fortification prevented VA deficiency in gerbils. During adequate provitamin A dietary intake, preformed VA intake resulted in excessive liver stores in gerbils, despite downregulation of carotenoid absorption and cleavage gene expression.

Prediction of Vitamin A Stores in Young Children Provides Insights into the Adequacy of Current Dietary Reference Intakes.

ABSTRACTBackgroundLimited data were available in infants and children when vitamin A (VA) DRIs were established; recommendations were developed based on average breast milk VA intake and extrapolation of data from adults.ObjectivesOur objective was to evaluate whether DRIs and reported intakes, with and without VA from intervention programs, would be sufficient to develop adequate VA stores from birth to age 5 y in Bangladeshi, Filipino, Guatemalan, and Mexican children.MethodsA mathematical relationship was established, defined by a series of equations, to predict VA total body stores (TBS) as a function of age based on VA intake and utilization. TBS calculated using reported VA intakes, with and without additional VA from intervention programs, were compared to those predicted using DRIs (specifically, Adequate Intake and RDA). Liver VA concentrations were also estimated.ResultsOur predictions showed that for these 4 groups, DRIs were sufficient to attain liver VA concentrations >0.07 μmol/g by 1 wk of age and sustain positive VA balance for 5 y. Using reported intakes, which were lowest in Bangladeshis from 1 y on and highest in Guatemalans, predicted VA stores in Bangladeshi and Filipino children increased until ∼2–3 y, then TBS stabilized and liver VA concentrations decreased with age. When VA interventions were included, stores exceeded those predicted using DRIs by 12–18 mo. In contrast, reported intakes alone in Guatemalan and Mexican children resulted in VA stores that surpassed those calculated using DRIs. For all populations, reported intakes were sufficient to build liver concentrations >0.07 μmol/g by 3 mo.ConclusionsAlthough more information is needed to better define dietary VA requirements in children, our results suggest that for an average, generally healthy child in a low- or middle-income country, current DRIs are sufficient to maintain positive VA balance during the first 5 y of life.

Perturbed Vitamin A Status Induced by Iron Deficiency Is Corrected by Iron Repletion in Rats with Pre-Existing Iron Deficiency

Although iron deficiency is known to interrupt vitamin A (VA) metabolism, the ability of iron repletion to restore VA metabolism and kinetics in iron-deficient rats is not well understood. In the present study, we examined the effects of dietary iron repletion on VA status in rats with pre-existing iron deficiency. Weanling Sprague-Dawley rats were fed a VA-marginal diet (0.35mg retinol/kg diet) containing either a normal concentration of iron [35ppm, control group (CN)] or reduced iron (3ppm, iron-deficient group, ID-); after 5 wk, 4 rats/group were killed for baseline measurements. A 3H-labeled retinol emulsion was administered intravenously to the remaining rats (n=6, CN; n=10, ID-) as tracer to initiate the kinetic study. On day 21 after dosing, n=5 ID- rats were switched to the CN diet, generating an iron-repletion group (ID+). Blood samples were collected at 34 time points ≤92 d after dose administration, when all rats were killed and iron and VA status were determined. At baseline, ID- rats had developed iron deficiency, with a reduced plasma VA concentration (0.67compared with 1.20μmol/L in ID- and CN rats, respectively; P <0.01) and a tendency toward higher liver VA (265compared with 187nmol in ID- and CN rats, respectively; P=0.10). On day 92, iron deficiency persisted in ID- rats, accompanied by 2-times higher liver VA (456nmol compared with 190nmol in ID- and CN rats, respectively; P <0.001) but lower plasma VA (0.64compared with 0.94μmol/L in ID- and CN rats, respectively; P=0.05). ID+ rats not only recovered from iron deficiency, but also exhibited less liver VA sequestration (276nmol) and normal plasma VA (0.91μmol/L, not different from CN rats). Our results suggest that iron repletion can remove the inhibitory effect of iron deficiency on hepatic mobilization of VA and restore plasma retinol concentrations in iron-deficient rats, setting the stage for kinetic studies of VA turnover in this setting.

Dietary Iron Repletion Stimulates Hepatic Mobilization of Vitamin A in Previously Iron-Deficient Rats as Determined by Model-Based Compartmental Analysis

Iron deficiency can result in hyporetinolemia and hepatic vitamin A (VA) sequestration. We used model-based compartmental analysis to determine the impact of iron repletion on VA metabolism and kinetics in iron-deficient rats. At weaning, Sprague-Dawley rats were assigned to either a VA-marginal diet (0.35mg retinol equivalent/kg) with adequate iron (35ppm, control group [CN]) or reduced iron (3ppm, iron-deficient group [ID-]), with an equivalent average body weight for each group. After 5 wk, n=4 rats from each group were euthanized for baseline measurements of VA and iron indices, and the remaining rats (n=6 CN, n=10 ID-) received an intravenous injection of 3H-labeled retinol in an emulsion as tracer to initiate the kinetic study. On day 21 after dosing, half of the ID- rats were switched to the CN diet to initiate iron repletion, referred to as the iron-repletion group (ID+). From the time of dosing, 34 serial blood samples were collected from each rat over a 92-d time course. Plasma tracer and tissue tracee data were fitted to 6- and 4-compartment models, respectively, to analyze the kinetic behavior of VA in all groups. Our mathematical model indicated that ID- rats exhibited a nearly 6-fold decrease in liver VA secretion and >4-fold reduction in whole-body VA utilization, compared with CN rats, whereas these perturbed kinetic behaviors were notably corrected in ID+rats, close to those from the CN group. Iron repletion can remove the inhibitory effect that iron deficiency exerts on hepatic mobilization of VA and restore retinol kinetic parameters to values similar to that of never-deficient CN rats. Together with improvements in iron and VA indices, our results suggest that restoration of an iron-adequate diet is sufficient to improve VA kinetics after a previous state of iron deficiency.

Vitamin A Status in Neonatal and Weanling Rats Reared by Mothers Consuming Normal and High Fat Diets with or Without Vitamin A Supplementation

Abstract Objectives Although the circulating level of vitamin A (VA) is reported to be significantly lower in obese adults, it is unknown if maternal adiposity would influence the VA status of the offspring. The aim of this study was to investigate the status and distribution of VA in the offspring of rats consuming a normal fat diet (NFD) or a high fat diet (HFD), with or without VA supplementation. Methods Sprague-Dawley rats arrived on their second day of gestation and were randomized to either a NFD (25% fat) or a HFD (50% fat) both with an adequate level of VA at 2.6 mg/kg. Upon the delivery of pups, half of rat mothers from the NFD or HFD cohort were switched to a NFD or a HFD both with supplemented VA at 129 mg/kg (NFD + VA and HFD + VA group), respectively. The other half remained on their diets with adequate VA (NFD and HFD group). At postnatal day 14 (P14) and P25, 4 pups/group were euthanized. At P25, the remaining weanling pups (n = 3/group) were fed diets of their respective mothers until being euthanized at P35. Concentrations of total retinol in serum, liver, visceral white AT (WAT), and brown AT (BAT) were measured by UPLC. Results Through the study, pups in non-supplemented groups showed a normal serum retinol concentration but a marginal liver VA status. At all the time points, serum retinol concentration was significantly (P &amp;lt; 0.05) increased in VA-supplemented groups as compared to non-supplemented ones; no significant difference was noted between the NFD and the HFD group. At P14, serum retinol concentration was significantly lower in the HFD + VA group than in the NFD + VA group. In liver, WAT, and BAT, both the concentration and the mass of total retinol was significantly higher in HFD + VA and NFD + VA group than in their respective control at all the time points, with no significant difference noted between the two control groups. At P25, both the concentration and the mass of total retinol in liver and in WAT was significantly higher in HFD + VA than in NFD + VA group. Conclusions Maternal VA supplementation added to both NFD and HFD raised VA status of the offspring. A lower VA concentration in serum but higher concentration in liver and WAT was observed in the HFD + VA group as compared to the NFD + VA group at given time points, indicating that maternal HFD consumption potentially compromised the availability of functional VA in circulation by increasing its deposition in storage organs. Funding Sources NIH.

Anthocyanin and Lycopene Content Do Not Affect Beta-Carotene Bioefficacy from Multicolored Carrots in Male Mongolian Gerbils

Abstract Objectives Increasing provitamin A carotenoid consumption is one way to combat vitamin A (VA) deficiency, which is a public health problem in various countries. Multicolored carrots contain provitamin A carotenoids as well as other bioactive phytochemicals, such as anthocyanins and lycopene. Two studies in male Mongolian gerbils were conducted to assess the bioefficacy of β-carotene (BC) with simultaneous consumption of anthocyanins and lycopene from multicolored carrots. Methods In Study 1 (n = 65), BC bioefficacy was compared in gerbils fed diets with a range of lycopene concentrations, sourced from freeze-dried red carrots. Study 2 (n = 66) utilized purple red carrots to create diets with varying anthocyanin content. Each study included positive and negative control groups (n = 10/group) fed white carrot VA-free feeds. Each study included 3-wk VA-depletion, baseline evaluation in 5 or 6 gerbils, and 4-wk treatment periods with 10 gerbils/treatment. HPLC analysis of liver VA stores and serum VA were performed. Results In Study 1, there were no differences among groups. These results may have been influenced by an unanticipated high variation in gerbil starting weight, which was correlated to their final hepatic VA stores. In Study 2, vitamin A liver stores (0.21 ± 0.08 μmol/g) of the treatment groups did not differ from baseline (0.23 ± 0.06 μmol/g) or the positive control group (0.22 ± 0.08 μmol/g), but all groups significantly differed from the negative control group (0.11 ± 0.07μmol/g). Serum retinol concentrations did not correlate with the hepatic VA stores in either study. Conclusions These results confirm previous studies that BC is bioavailable from purple red carrots. The results from Study 2, suggest that simultaneous consumption of carotenoids and anthocyanins do not impact the relative bioavailability of BC. These results add more evidence that serum VA concentrations do not accurately represent hepatic VA stores at deficient to normal concentrations. Funding Sources California Fresh Carrot Advisory Board and the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2016–51,181-25,400 (PWS).