Assessment of indicators of vitamin A status in non-cirrhotic chronic hepatitis C patients

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.

Dietary intake of pearl millet based weaning food supplemented with iron and vitamin A enhances bioavailability of vitamin A in anemic rats

Abstract. The study was aimed to assess vitamin A bioavailability and allergenicity of pearl millet ( Pennisetum glaucum) based weaning food (PMWF) fortified with iron and retinyl acetate in male Wistar albino rats. Animals (n = 64) were divided into Normal (NG) and Anemic (AG) groups; further sub-divided into 4 sub-groups having 8 animals each receiving synthetic diet, commercial diet, iron fortified PMWF diet and iron (150.00 ± 0.73 ppm) plus retinyl acetate (393.00 ± 3.07 μg/100 g) fortified PMWF diet (Final diet). Results revealed that anemic sub-groups showed apparent digestibility coefficient (ADC) in the range of 69.5 ± 0.40–93.2 ± 0.79%, which was significantly (P < 0.01) higher than normal sub-groups (65.5 ± 0.62–84.6 ± 0.33%). In both groups, rats fed final diet presented significantly (P < 0.01) higher ADC (84.6 ± 0.33–93.2 ± 0.79%) than that of animals received iron fortified diet (69.0 ± 0.59–76.1 ± 1.02%), indicating higher bioavailability of vitamin A in final diet. Moreover, hepatic vitamin A replenished rapidly in anemic groups (1.79–27.8) when compared to normal rats (1.11–19.4 μg/g liver). Immunoglobulins IgG, IgE in blood serum and IgA in intestinal fluid ranged from 574 ± 6.48 to 603 ± 9.76 μg/ml, 287 ± 4.46 to 309 ± 5.70 ng/ml and 204 ± 10.33 to 255 ± 13.22 μg/ml, respectively. However, no significant (P > 0.05) difference was observed between the groups and/or subgroups, suggesting no allergic response of final diet. Stimulation index triggered by lipopolysaccharide (LPS) ranged from 1.22 ± 0.06 to 1.45 ± 0.09 μg ml−1 in normal sub-groups and 1.16 ± 0.02 to 1.33 ± 0.03 μg ml−1 in anemic sub-groups with no significant (P > 0.05) difference among them. Overall, it can be concluded that retinyl acetate could be an effective fortificant to improve the status of vitamin A in anemic models.

Hepatic Retinyl Ester Hydrolases and the Mobilization of Retinyl Ester Stores

For mammals, vitamin A (retinol and metabolites) is an essential micronutrient that is required for the maintenance of life. Mammals cannot synthesize vitamin A but have to obtain it from their diet. Resorbed dietary vitamin A is stored in large quantities in the form of retinyl esters (REs) in cytosolic lipid droplets of cells to ensure a constant supply of the body. The largest quantities of REs are stored in the liver, comprising around 80% of the body’s total vitamin A content. These hepatic vitamin A stores are known to be mobilized under times of insufficient dietary vitamin A intake but also under pathological conditions such as chronic alcohol consumption and different forms of liver diseases. The mobilization of REs requires the activity of RE hydrolases. It is astounding that despite their physiological significance little is known about their identities as well as about factors or stimuli which lead to their activation and consequently to the mobilization of hepatic RE stores. In this review, we focus on the recent advances for the understanding of hepatic RE hydrolases and discuss pathological conditions which lead to the mobilization of hepatic RE stores.