scholarly journals Retinol homeostasis in lambs given low and high intakes of vitamin A

1983 ◽  
Vol 50 (2) ◽  
pp. 235-248 ◽  
Author(s):  
Susan Donoghue ◽  
David S. Kronfeld ◽  
David Sklan
Keyword(s):  
Vitamin A ◽  
Plasma Clearance ◽  
Basal Diet ◽  
Retinol Binding Protein ◽  
Faecal Excretion ◽  
Several Variables ◽  
Supplemental Vitamin ◽  
Retinyl Esters ◽  
Plasma Retinol ◽  
Retinol Concentration

1. Four groups of lambs were fed on a low-carotene basal diet. One group received no supplemental vitamin A (mildly deficient). Remaining groups were supplemented daily with vitamin A acetate equivalent to 100 (control) 9000 (mildly intoxicated) and 18000 (severely intoxicated) μg retinol/kg body-weight. After 16 weeks lambs received a bolus of[15−3H]retinol intravenously; blood, urine and faeces were sampled for 48 h.2. Plasma retinol was complexed to a protein of 20000 molecular weight (MW), which in turn was complexed to a protein of 65000 MW; these proteins correspond respectively to retinol-binding protein and prealbumin. Plasma retinol concentration reached plateau values in intoxicated lambs, but plasma retinyl ester concentrations increased rapidly when liver contents of both retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded 30 μg. Labelled compounds, more polar than retinol, were found in plasma; their concentration increased tenfold in intoxicated lambs within 48 h.3. Plasma retinol transport rates were 0·1, 10·5 and 11·8 times control values, and clearance rates were 0·3, 14·1 and 14·3 times control values in mildly-deficient, and mildly- or severely-intoxicated lambs respectively. Turnover of retinol increased rapidly when liver contents of retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded approximately 30 μg. Plasma clearance of retinyl esters was unchanged with intake. Faecal excretion of tracer increased linearly with plasma retinol clearance.4. Our findings identify, several variables that appear to be involved in retinol homeostasis, including plasma retinol clearance and excretion.

scholarly journals Distribution of injected fat-soluble vitamins in plasma and tissues of nursery pigs

2020 ◽  
Vol 33 (12) ◽  
pp. 1985-1990 ◽  
Author(s):  
Young Dal Jang ◽  
Mikayla J. Rotering ◽  
Paige K. Isensee ◽  
Kirsten A. Rinholen ◽  
Carli J. Boston-Denton ◽  
...  
Keyword(s):  
Vitamin A ◽  
Basal Diet ◽  
Retinyl Palmitate ◽  
Post Injection ◽  
Tissue Samples ◽  
Nursery Pigs ◽  
Vitamin Status ◽  
Supplemental Vitamin ◽  
Plasma Retinol ◽  
Fat Soluble Vitamins

Objective: The objective of this experiment was to investigate the effects of fat-soluble vitamin injection on plasma and tissue vitamin status in nursery pigs.Methods: A total of 16 pigs (initial body weight: 7.15±1.1 kg) were allotted to 2 treatments at d 7 post-weaning. Pigs were fed a corn-soybean meal-based basal diet with no supplemental vitamin A and i.m. injected with 300,000 IU of retinyl palmitate, 900 IU of d-α-tocopherol and 30,000 IU of vitamin D<sub>3</sub> with control pigs having no vitamin injection. Blood (d 0, 3, 7, and 14 post-injection) and tissue samples (liver, brain, heart, lung, and muscle; d 7 and 14 post-injection) were collected from pigs. Retinyl palmitate, retinol, and α-tocopherol concentrations were analyzed in plasma and tissues, while plasma was assayed for 25-hydroxycholecalciferol (25-OHD<sub>3</sub>).Results: Plasma retinol and 25-OHD<sub>3</sub> concentrations increased by the vitamin injection from d 3 to 14 post-injection (p<0.05) whereas plasma retinyl palmitate was detected only in the vitamin treatment at d 3 and 7 post-injection (115.51 and 4.97 μg/mL, respectively). Liver retinol, retinyl palmitate, and retinol+retinyl palmitate concentrations increased by retinyl palmitate injection at d 7 and 14 post-injection (p<0.05) whereas those were not detected in the other tissues. The d-α-tocopherol injection increased α-tocopherol concentrations in plasma at d 3 and 7 post-injection (p<0.05) and in liver, heart (p<0.10), and muscle (p<0.05) at d 7 post-injection.Conclusion: Fat-soluble vitamin injection increased plasma status of α-tocopherol, retinol, retinyl palmitate and 25-OHD<sub>3</sub>. As plasma levels decreased post-injection, vitamin A level in liver and vitamin E level in muscle, heart and liver increased. The α-tocopherol found in plasma after injection was distributed to various tissues but retinyl palmitate only to the liver.

scholarly journals Streptozotocin-induced diabetes in rats is associated with impaired metabolic availability of vitamin A (retinol)

1996 ◽  
Vol 75 (4) ◽  
pp. 615-622 ◽  
Author(s):  
P. J. Tuitoek ◽  
S. Ziari ◽  
A. T. C. Tsin ◽  
R. V. Rajotte ◽  
Miyoung Suh ◽  
...  
Keyword(s):  
Vitamin A ◽  
Wistar Rats ◽  
Plasma Concentrations ◽  
Basal Diet ◽  
Diabetic Rats ◽  
Lower Plasma ◽  
Vitamin A Supplementation ◽  
Streptozotocin Induced Diabetes ◽  
Plasma Retinol ◽  
Retinol Concentration

Using streptozotocin-induced diabetic Wistar rats, studies were carried out to examine the metabolic availability of vitamin A in the plasma, liver and the retina of the eye. Control and diabetic rats were fedad lib. on a semi-purified diet either with or without (basal) vitamin A supplementation, or pair-fed on the basal diet for 4 weeks. Despite the fact that diabeticrats consumed 48% more feed, they had lower plasma concentrations of retinol (P<0·003). The decrease in plasma retinol concentration was a response to diabetes (or diabetes-induced trauma), since neither pair-feeding (P<0·01) nor vitamin A supplementation altered this effect (P<0·05). Furthermore, the hepatic concentrations of the vitamin in these animals remained elevated and this increase was greater in the supplemented diabetic group (P<0·001). Decreases in 11-cis retinal (a component of rhodopsin) concentrations in the retina were also observed in diabetic animals. The increased hepatic and the decreased plasma and retina vitamin Alevels suggest a defect in the transport of the vitamin from the liver.

scholarly journals Vitamin A Transporters in Visual Function: A Mini Review on Membrane Receptors for Dietary Vitamin A Uptake, Storage, and Transport to the Eye

Nutrients ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 3987
Author(s):  
Nicasio Martin Ask ◽  
Matthias Leung ◽  
Rakesh Radhakrishnan ◽  
Glenn P. Lobo
Keyword(s):  
Cell Growth ◽  
Vitamin A ◽  
Visual Function ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Peripheral Tissues ◽  
Retinol Binding Protein 4 ◽  
Retinyl Esters ◽  
And Function

Vitamins are essential compounds obtained through diet that are necessary for normal development and function in an organism. One of the most important vitamins for human physiology is vitamin A, a group of retinoid compounds and carotenoids, which generally function as a mediator for cell growth, differentiation, immunity, and embryonic development, as well as serving as a key component in the phototransduction cycle in the vertebrate retina. For humans, vitamin A is obtained through the diet, where provitamin A carotenoids such as β-carotene from plants or preformed vitamin A such as retinyl esters from animal sources are absorbed into the body via the small intestine and converted into all-trans retinol within the intestinal enterocytes. Specifically, once absorbed, carotenoids are cleaved by carotenoid cleavage oxygenases (CCOs), such as Beta-carotene 15,15’-monooxygenase (BCO1), to produce all-trans retinal that subsequently gets converted into all-trans retinol. CRBP2 bound retinol is then converted into retinyl esters (REs) by the enzyme lecithin retinol acyltransferase (LRAT) in the endoplasmic reticulum, which is then packaged into chylomicrons and sent into the bloodstream for storage in hepatic stellate cells in the liver or for functional use in peripheral tissues such as the retina. All-trans retinol also travels through the bloodstream bound to retinol binding protein 4 (RBP4), where it enters cells with the assistance of the transmembrane transporters, stimulated by retinoic acid 6 (STRA6) in peripheral tissues or retinol binding protein 4 receptor 2 (RBPR2) in systemic tissues (e.g., in the retina and the liver, respectively). Much is known about the intake, metabolism, storage, and function of vitamin A compounds, especially with regard to its impact on eye development and visual function in the retinoid cycle. However, there is much to learn about the role of vitamin A as a transcription factor in development and cell growth, as well as how peripheral cells signal hepatocytes to secrete all-trans retinol into the blood for peripheral cell use. This article aims to review literature regarding the major known pathways of vitamin A intake from dietary sources into hepatocytes, vitamin A excretion by hepatocytes, as well as vitamin A usage within the retinoid cycle in the RPE and retina to provide insight on future directions of novel membrane transporters for vitamin A in retinal cell physiology and visual function.

scholarly journals Retinol binding protein 4 in dairy cows: its presence in colostrum and alteration in plasma during fasting, inflammation, and the peripartum period

2009 ◽  
Vol 77 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Mabrouk A Abd Eldaim ◽  
Akihiro Kamikawa ◽  
Mohamed M Soliman ◽  
Mohamed M Ahmed ◽  
Yuko Okamatsu-Ogura ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
Retinol Binding Protein 4 ◽  
Lps Challenge ◽  
Bovine Plasma ◽  
Basal Plasma ◽  
Peripartum Period ◽  
Plasma Retinol ◽  
Retinol Concentration

Retinol-binding protein 4 (RBP4) is a plasma protein involved in retinol transportation, and recent evidence in rodents suggests that RBP4 is also a metabolic regulator that modifies insulin sensitivity. To assess how RBP4 levels are regulated in ruminants, we determined the RBP4 concentrations in bovine plasma and milk using Western blot analysis. Plasma RBP4 levels in non-pregnant non-lactating (control) cows were around 45 μg/ml, which were sustained during 60-h fasting, but decreased significantly 4 h after lipopolysaccharide (LPS) administration. Basal plasma retinol concentration was around 30 μg/dl, but this decreased to approximately one-third and one-half of these values during fasting and 8 h after LPS challenge, respectively. Plasma RBP4 and retinol levels in cows 3–6 d before parturition were comparable to those of the controls. However, on the day of parturition both were significantly decreased and had returned to basal levels by two weeks after calving. Interestingly, RBP4 was clearly detected in colostrum (16·4±5·6 μg/ml) but was only faintly detected in milk from cows at 7 d and 15 d after calving. Retinol concentrations in colostrum were almost 10-fold higher than those in plasma, while those in milk were comparable to those in plasma. These results suggest that RBP4 and retinol levels are independently regulated under physiological and pathophysiological conditions and that RBP4, like retinol, is transferred from maternal stores to calves through colostrum.

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

2000 ◽  
Vol 83 (5) ◽  
pp. 513-520 ◽  
Author(s):  
Suzanne M. Filteau ◽  
Juana F. Willumsen ◽  
Keith Sullivan ◽  
Karin Simmank ◽  
Mary Gamble
Keyword(s):  
Vitamin A ◽  
Sensitivity And Specificity ◽  
Assessment Tool ◽  
Binding Protein ◽  
Vitamin A Deficiency ◽  
Retinol Binding Protein ◽  
Serum Retinol ◽  
Vitamin A Status ◽  
Plasma Retinol

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.

scholarly journals Vitamin A status in Cuban children aged 6–11 years

2008 ◽  
Vol 11 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Consuelo Macías-Matos ◽  
Gisela Pita-Rodríguez ◽  
Pedro Monterrey-Gutiérrez ◽  
José Reboso-Pérez
Keyword(s):  
Vitamin A ◽  
Fruits And Vegetables ◽  
Sixth Grade ◽  
Eastern Region ◽  
First Semester ◽  
Vitamin A Status ◽  
Small Variety ◽  
Mother And Child ◽  
Plasma Retinol ◽  
Retinol Concentration

AbstractObjective and settingA nationwide study was performed in Cuba to assess vitamin A status and the intake of vitamin-A-providing foods in children aged 6–11 years.Design and subjectsThe sample comprised 1191 schoolchildren from first to sixth grade, both sexes, from municipalities randomly selected from the five eastern provinces of Cuba in 2002 (first semester) and from the four western and four central provinces in 2003 (first semester). A food-frequency questionnaire was completed by 2038 mother-and-child pairs.ResultsMean (±standard deviation) plasma retinol concentrations were 1.77 ± 0.48 μmol l−1in the western, 2.01 ± 0.56 μmol l−1in the central and 1.40 ± 0.41 μmol l−1in the eastern region. No child had plasma retinol concentration below 0.35 μmol l−1, indicative of a high risk of clinical deficiency. Subclinical deficiency, plasma retinol concentration of 0.35–0.7 μmol l−1, was seen in <2% of subjects in all three regions and was <5% even in the two provinces with the worst vitamin A status (Guantánamo, 4.6%; Las Tunas, 3.0%). Adequate status (>1.05 μmol l−1) was present in >90% of subjects in all western and central provinces, and in one of the eastern provinces (Holguín), whereas in the four remaining eastern provinces, adequate status was present in >75%. Only nine fruits and vegetables were consumed frequently (>3 times per week) by >50% of children. Thirty-seven per cent regularly consumed a supplement containing vitamin A.ConclusionsMost Cuban children aged 6–11 years had adequate vitamin A status. Consumption of foods rich in vitamin and provitamin A, especially vegetables, was frequent but limited to a small variety of foods.

scholarly journals Optimal nutrition: vitamin A and the carotenoids

1999 ◽  
Vol 58 (2) ◽  
pp. 449-457 ◽  
Author(s):  
David I. Thurnham ◽  
Christine A. Northrop-Clewes
Keyword(s):  
Vitamin A ◽  
Antioxidant Properties ◽  
Developed Countries ◽  
Retinol Binding Protein ◽  
Animal Origin ◽  
High Dose ◽  
Uptake Mechanism ◽  
Plant Foods ◽  
Vitamin A Status ◽  
Plasma Retinol

There are two major dietary sources of vitamin A: easily absorbed retinyl palmitate in foods of animal origin, and poorly bioavailable carotenoids from plant foods. Plasma retinol is tightly controlled, probably by regulation of retinol-binding protein (RBP) formation in the liver, and only hormonal factors (e.g. oral contraceptives) and infection will alter the homeostasis. Delivery of retinol to the tissues is facilitated by the RBP-retinol complex; however, there is evidence that this mechanism can be bypassed when very high doses of vitamin A are given. Some retinyl ester may be released to tissues from chylomicrons when the latter bind to tissue lipoprotein receptors during their passage from the gut to the liver following a meal. High-dose vitamin A therapy is a means of rapidly improving vitamin A status in persons with sub-optimal vitamin A nutrition but there are dangers of toxic symptoms (e.g. teratogenicity) from excess vitamin A usage. Evidence is presented to suggest that the plasma retinol : RBP may be a guide to optimal vitamin A status, since values less than one frequently occur in less-developed countries and during infection. In contrast to plasma retinol, plasma carotenoids reflect the dietary intake of plant foods. However, absorption is limited by poor bioavailability and a saturable uptake mechanism in competition with other phytochemicals. Recent work on bioavailability suggests that the calculation of plant food vitamin A activity should be re-examined. Illness has little influence on plasma levels except by suppressing appetite. Carotenoids are generally regarded as non-toxic yet intervention studies with β-carotene in smokers have been associated with increased lung cancer and heart disease. Some carotenoids are important as vitamin A precursors, but the physiological importance of their antioxidant properties is not known and consequently the amount needed for optimal nutrition is uncertain.

scholarly journals Vitamin A and carotenoid status in rural China

1996 ◽  
Vol 76 (6) ◽  
pp. 809-820 ◽  
Author(s):  
Guangya Wang ◽  
Thierry A. Brun ◽  
Catherine A. Geissler ◽  
Banoo Parpia ◽  
Martin Root ◽  
...  
Keyword(s):  
Vitamin A ◽  
Vegetable Consumption ◽  
Rural China ◽  
Retinol Binding Protein ◽  
Animal Products ◽  
Republic Of China ◽  
Vitamin A Status ◽  
Plasma Retinol ◽  
Highly Correlated ◽  
Β Carotene

Vitamin A status of 260 groups of twenty-five males or twenty-five females, aged 35–64 years, surveyed in twenty-four provinces of the People's Republic of China, was assessed by measuring plasma retinol, retinol-binding protein and β-carotene concentrations. Direct measurements of food intake over a 3 d period and questionnaire data on the frequency of consumption of vegetables, fruit, animal products and other dietary items were also used. Vitamin A status appeared to be low only in specific counties but in general was satisfactory or only marginally deficient. Plasma harotene levels were strikingly low in comparison with Western levels despite generous vegetable consumption suggwg that intake of vitamin A precursors may have been adequate but not abundant enough to maintain high circulating plasma levels of β-carotene. Plasma β-carotene, for both males and females, was significantly correlated with the frequency of consumption of green vegetables. Plasma retinol, for males, was highly correlated with meat, fish, oil and alcohol consumption expresPed both in quantity or frequency of consumption. Higher levels of plasma retinol, together with lower levels of plasma β-carotene in males compared with females, suggest that men consume more animal products or may have higher retinol requirements and therefore a higher rate of conversion of β-carotene to retinol.

Vitamin A and retinol-binding protein metabolism during fetal development in the rat.

1977 ◽  
Vol 233 (4) ◽  
pp. E263 ◽  
Author(s):  
Y I Takahashi ◽  
J E Smith ◽  
D S Goodman
Keyword(s):  
Vitamin A ◽  
Fetal Development ◽  
Early Phase ◽  
Fetal Liver ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
Second Phase ◽  
Organ Differentiation ◽  
Third Phase ◽  
Plasma Retinol

Studies were conducted on the metabolism and placental transport of vitamin A and plasma retinol-binding protein (RBP) during fetal development in the rat. Vitamin A accumulated in the conceptus in three phases: an early phase (days 7-9 of gestation) characterized by a high vitamin A concentration; a second phase (days 11-14) where vitamin A and RBP accumulated in parallel; and a third phase of continued vitamin A and RBP accumulation (days 16-20) in which vitamin A was stored in the fetal liver. The early phase of vitamin A accumulation may reflect a mechanism that exists to prepare the conceptus to meet the presumably higher vitamin A requirements of the critical period (days 10-14) of organ differentiation. Fetuses and placentas from retinol-deficient dams showed low levels of RBP through days 16-18 of gestation. A retinol-repletion study suggested, moreover, that the maternal retinol-RBP complex crossed the placenta. The various studies all suggest that vitamin A is transported from dam to fetus, from and after day 11, mainly by transplacental transport of maternal retinol-RBP. Finally, evidence was obtained indicating that the fetal liver begins to synthesize RBP around the 16th day of gestation and that by the 20th day, the fetal liver has a considerable capacity for RBP synthesis.

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