absorption and metabolism of vitamin a

The binding of ATRA to the RAR/RXR complex induces a conformational change in the ligand binding domain of the receptor, which causes replacement of corepressors by coactivators, such as members of the steroid receptor coactivator (SRC)/p160 family and p300/CREB-binding protein (CBP) (26, 34). 1978. Factors influencing the response to parathyroid hormone, Vitamin A/retinoids signalling in the human lung, Frequent mutations in the ligand-binding domain of PML-RARα after multiple relapses of acute promyelocytic leukemia: analysis for functional relationship to response to all-trans retinoic acid and histone deacetylase inhibitors in vitro and in vivo, Chromatographic analysis of endogenous retinoids in tissues and serum, Quantification of endogenous retinoic acid in limited biological samples by LC/MS/MS, Ligands for retinoic acid receptors are elevated in osteoarthritis and may contribute to pathologic processes in the osteoarthritic joint, Cortical and trabecular bone, bone mineral density, and resistance to ex vivo fracture are not altered in response to life-long vitamin A supplementation in aging rats, Studies on congenital osteopetrosis in microphthalmic mice using organ cultures: impairment of bone resorption in response to physiologic stimulators, Bone-resorbing agents affect the production and distribution of procollagenase as well as the activity of collagenase in bone tissue, Effects of retinoic acid on bone formation and resorption in cultured mouse calvaria, Inhibitory effects of 9-cis and all-trans retinoic acid on 1,25(OH)2 vitamin D3-induced bone resorption, Differential effects of glucocorticoids on bone resorption in neonatal mouse calvariae stimulated by peptide and steroid-like hormones, Effects of hypervitaminosis A on the bone and mineral metabolism of the rat, Retinoic acid and 1,25-dihydroxyvitamin D3 stimulate osteoclast formation by different mechanisms, Retinoids inhibit differentiation of hematopoietic osteoclast progenitors, 1,25(OH)2D3 induces differentiation of osteoclast-like cells from human bone marrow cultures, Trypsinized osteoclast-like multinucleated cells formed in rat bone marrow cultures efficiently form resorption lacunae on dentine, Effects of geranylgeranoic acid in bone: induction of osteoblast differentiation and inhibition of osteoclast formation, Retinoic acid stimulates expression of the functional osteoclast integrin α v β 3: transcriptional activation of the β 3 but not the α v gene, Retinoic acid increases proliferation of human osteoclast progenitors and inhibits RANKL-stimulated osteoclast differentiation by suppressing RANK, Retinoic acid directly stimulates osteoclastic bone resorption and gene expression of cathepsin K/OC-2, Kinetics of the osteoclast cytoskeleton during the resorption cycle in vitro, Effect of retinoic acid on the resorptive activity of chick osteoclasts in vitro, Effect of vitamin A on bone resorption: evidence for direct stimulation of isolated chicken osteoclasts by retinol and retinoic acid, Effects of retinol on activation of latent transforming growth factor-β by isolated osteoclasts, Hypercalcemia induced with an arotinoid in thyroparathyroidectomized rats. 2020 Aug 1;150(8):2223-2229. doi: 10.1093/jn/nxaa176. Vitamin A Chemistry , source , Metabolism , Deficiency - Usmle step 1 Biochemistry Dr Bhanu prakash - Duration: 11:34. Eating of animal livers, during a period of time when the dietary habit of Homo erectus was changing, was suggested to be responsible for the high intake of vitamin A. A north-south gradient for 25(OH) D levels is thought to exist, with higher levels in Scandinavia and lower levels in countries like Italy and Spain (118). Smaller amounts of retinyl esters, as well as carotenoids, are also carried by chylomicrons and remnants to extrahepatic tissues for use and storage (13). So, consuming1.5g of ascorbic acid results in 50% absorption while ingesting over 12g causes only 16% of the vitamin … . It has been reported that ATRA may have proinflammatory effects. The presence of fat in the diet greatly aids vitamin A absorption. For osteoclastogenesis to occur, progenitor cells must be activated by macrophage colony-stimulating factor (M-CSF), which is needed for proliferation and survival of osteoclasts, and by receptor activator of nuclear factor-κB (RANK) ligand (RANKL), which is required for osteoclast differentiation. An attempt to reconcile data generated ex vivo/in vitro with those obtained in vivo is presented in Section X. However, the changes in cortical and trabecular bone did not affect the resistance to fractures. At a certain stage, mononuclear osteoclasts will fuse to latent multinucleated osteoclasts, which eventually will be activated to polarized bone-resorbing osteoclasts. Similarly, Scheven and Hamilton (154), using nonadherent mononuclear cells from rat bone marrow, found no effect of ATRA, but stimulation of osteoclastogenesis with 1,25(OH)2 D3, again suggesting contamination with stromal cells. Interestingly, the levels of retinol were found to be similar in all 3 locations (1.1–1.6 mmol/L). Like many malignant tumors, APL is associated with increased angiogenesis most likely due to vascular endothelial growth factor produced by the tumor cells. Furthermore, the authors found no association between vitamin A or retinol intake from food and supplements, or food only, and the risk of hip or all fractures (97). Conaway HH, Pirhayati A, Persson E, et al. Copyright © 2013 by The Endocrine Society, Making, Cloning and Expression of Human Insulin Genes in Bacteria: The Path to Humulin@, Revisiting the complexity of GLP-1 action-from sites of synthesis to receptor activation, Multiple Endocrine Neoplasia Type 1: Latest Insights, Metabolic Consequences of Solid Organ Transplantation, Progress in Translational Regulatory T Cell Therapies for Type 1 Diabetes and Islet Transplantation, The Journal of Clinical Endocrinology & Metabolism, II Necessity of Vitamin A for Vision and Cellular Functions, III Dietary Sources, Absorption, Hepatic Storage, and Transport of Vitamin A to Tissues, IV Target Cell Uptake, Intracellular Metabolism, Cytoplasmic and Nuclear Receptors Mediating Vitamin A Effects, VI Human Studies Evaluating Whether Current Intake of Vitamin A Is Associated With Osteoporosis and Fracture, VII Bone Remodeling and Modeling at the Cellular Level, VIII Retinoids, Osteoclast Differentiation, and Bone Resorption in Organ-Cultured Intact Bones, IX Retinoids and Osteoclast Differentiation and Activity in Cell Cultures, Receive exclusive offers and updates from Oxford Academic, Transforming Growth Factor-β1 to the Bone, Osteoclast Activity and Subtypes as a Function of Physiology and Pathology—Implications for Future Treatments of Osteoporosis, Chick Ovalbumin Upstream Promoter-Transcription Factors (COUP-TFs): Coming of Age, Retinoic Acid Receptors and Cellular Retinoid Binding Proteins: Complex Interplay in Retinoid Signaling. The first evidence for a direct stimulatory effect by vitamin A on bone resorption in chemically defined medium with no serum, or low serum (5%), was provided by Raisz et al (148) in 1977 when it was demonstrated that retinol stimulated radioactive calcium release from newborn mouse parietal bones. The term “vitamin A” is used for any compound possessing the biological activity of retinol (retinyl esters, retinol, retinal, retinoic acid, and oxidated and conjugated forms of both retinol and retinal) (Figure 1). In the Third National Health and Nutrition Examination Survey (NHANES III), the prevalence of serum samples with retinyl ester concentrations >10% of total vitamin A was substantially higher than expected (64). It is still not clear whether 9-cis RA is formed physiologically in bone cells and what role this isomer may play as a specific ligand for RXR (27); however, it was shown recently that 9-cis RA can be produced in vivo in the mouse pancreas (28), which suggests that the isomer may be physiologically relevant. H. Herschel Conaway, Petra Henning, Ulf H. Lerner, Vitamin A Metabolism, Action, and Role in Skeletal Homeostasis, Endocrine Reviews, Volume 34, Issue 6, 1 December 2013, Pages 766–797, https://doi.org/10.1210/er.2012-1071. These results are very similar to the observations with ATRA and 1,25(OH)2 D3 in mouse bone marrow cultures and suggest that the purified mononucleated cells used in the study by Thavarajah et al (156) contained stromal cells. Serum levels of osteocalcin were measured at 0 and 6 weeks, and serum bone-specific alkaline phosphatase and N-telopeptide of type 1 collagen were measured at 0, 2, 4, and 6 weeks (103). HHS Retinoid metabolism linked to absorption • Retinal produced by at least the central cleavage step is reduced in the intestinal mucosa to retinol. Mechanisms involved in the digestion and absorption of dietary vitamin A require the participation of several proteins. Furr HC, Amedee-Manesme O, Clifford AJ, et al. This suggests that the number of bone-forming osteoblasts was reduced, but the activity of the remaining osteoblasts was unaffected, a finding in agreement with in vitro observations suggesting that retinoids inhibit osteoblast differentiation. Oxford University Press is a department of the University of Oxford. 1 The terms retinol, retinal, retinoic acid, and retinyl ester refer, respectively, to vitamin Aalcohol, aldehyde, acid, and ester. Effects of β-Carotene and Its Cleavage Products in Primary Pneumocyte Type II Cells. In 1934, Strauss and Maddock (138) noted more osteoclasts (“osteoclasis”) associated with hypervitaminosis A, but it was not known at the time whether the skeletal effects associated with vitamin A in intact animals were indirect or direct. Huang H, Goodman DS (1965) Vitamin A and carotenoids. Target cell uptake and intracellular signaling. RAR-retinoid X receptor heterodimers function as transcription factors, binding RAR-responsive elements in promoters of different genes. We seek to define the mechanism(s) of intestinal absorption of dietary carotenoids and their distribution into blood cells. . The most potent inhibition occurred when ATRA was added with RANKL to the cultures; when ATRA was added 24 or 48 hours after RANKL, inhibition gradually decreased. Furthermore, the circulating levels of the resorption marker TRAP were different in the 2 studies, with increased levels observed by Kneissel et al (75) and decreased levels found by Lind et al (76). These data appear to be in agreement with in vitro investigations indicating inhibition of osteoclast progenitors from bone marrow; however, the 2 other studies have reported decreases in trabecular bone mass (75, 147) and, in 1 of these investigations, no change in trabecular osteoclasts. He was a Dutch officer on William Barentsz' third voyage (in 1596) in search of the Northwest Passage. However, uptake of retinyl esters, carotenoids, and ATRA have also been described. Based on fluorescence-activated cell sorting analysis, most purified macrophages express intracellular RARα and RARβ protein, but very few of the cells express RARγ protein. In a longitudinal study evaluating the risk of hip and total fractures in 75 747 ethnically diverse postmenopausal women 50–79 years of age participating in the Women's Health Initiative Observational Study in the United States, no association between vitamin A or retinol intake and the risk of hip fractures or total fractures was observed; however, a modest increase in total fracture risk with high vitamin A (≥7508 μg RE/d) and retinol (≥1426 μg/d) intake was observed with low vitamin D intakes ≤11 μg/d (115). In the past, DXA has been employed to measure BMD and has proven to be valuable clinically, especially in the postmenopausal female, but DXA does not distinguish between cortical and trabecular bone. It was noted that the number of osteoclasts formed in vitamin A-stimulated bones was fewer than those formed in PTH-stimulated bones, suggesting that the 2 compounds caused bone breakdown by different mechanisms. Activation of the receptor RANK is dependent not only on the amount of RANKL present, but also on the amount of decoy receptor, osteoprotegerin (OPG), that is present. Vitamin A requirement can be met from dietary preformed vitamin A or provitamin A carotenoids, the most important of which is β -carotene. Measurement of serum retinol levels is also not adequate for determining vitamin A status in individuals with clinical or subclinical toxicity (61). . A slowing of the rate of humerus bone loss was attributed to vitamin A intake. -, Nature. The activation and repression of transcription through ligation of ATRA to different nuclear receptors and binding to response elements (RARE, PPRE, and RORE) in the promoters of genes represent genomic effects of the retinoids. Korycka M, Bialek T, Miler M, Chabrowski K, Berger S. Eur J Clin Nutr. Abbreviations: Thyroparath, thyroparathyroidectomized; ↓, decrease; ↑, increase; ?, not investigated; —, no effect. A, Osteoblasts on the surfaces of cortical and trabecular bone originate from pluripotent stromal cells present in bone marrow. In addition to RARs, RXRs, and PPARs, retinoids have been observed to bind retinoid-related orphan receptors (RORs) β and γ (41). The Intestinal Absorption and Metabolism of Vitamin A and P-Carotene in Man * @inproceedings{Goodman1966TheIA, title={The Intestinal Absorption and Metabolism of Vitamin A and P-Carotene in Man *}, author={D. S. Goodman and R. Blomstrand and B. Werner and H. Huang and T. Shiratori}, year={1966} } The RARE is a direct repeat of the hexamer motif PuG(G/T)TCA separated by 1 (DR1), 2 (DR2), or 5 (DR5) base pairs (26). Functions • Vitamin B12 act as prosthetic group or coenzyme. In addition to RARs and PPARs, ATRA can also bind to RORs to initiate transcription. the intestinal absorption of ,8-carotene and retinol in the rat were recently reported by Huang and Goodman (7). Genetic studies evaluating the relationships of RAR and RXR genes to bone mass and fragility fracture in the human should additionally be pursued. Alternatively, ATRA can be shuttled by FABP to bind PPARs in the nucleus. D'Ambrosio DN, Clugston RD, Blaner WS. As this occurs, a visual signal is transmitted to the central nervous system. These data suggest that RARβ and RARγ are not as important as RARα for inhibition of osteoclastogenesis stimulated by RANKL, but conclusive evidence for this awaits studies where RARβ and RARγ are knocked down by interference silencing or use of cells from mice in which these receptors have been deleted. Vitamin A is essential for life in all vertebrate animals. In contrast, there is also ample evidence that ATRA is a potent in vitro inhibitor of osteoclastogenesis in cell culture systems employing progenitors from either mouse bone marrow or spleen, or human peripheral blood. PPAR/RXR heterodimers also function as transcription factors, activating specific response elements of target genes (35–37) (Figure 3). Concentrations can vary significantly over short distances; eg, ATRA levels of 0.6 nmol/L have been reported in the upper zones of the growth plate, compared to about 1.8 nmol/L in the lower parts of the plate, whereas the perichondrium was found to be quite rich in ATRA (about 4.9 nmol/L) (33). The pursuit of a healthy lifestyle often includes a diet where many foods contain vitamin A, as well as taking vitamin A supplements. Why periosteal osteoclast progenitor cells are not inhibited by ATRA is unclear. Vitamin B9 is necessary for the cell growth, DNA formation and amino acid metabolism. Table 1 is a summary of these studies based on increases, decreases, or no association of fracture risk or BMD to increased vitamin A intake or increased vitamin A intake/low vitamin D. Present data suggest that increased vitamin A intake/low vitamin D favors a decrease in BMD and an increase in fracture risk; however, the effect of increased intake of vitamin A alone is less clear, with increases, decreases, and no associations to fracture risk and BMD reported. | These cells not only make bone but also control the formation of osteoclasts. In women with vitamin D deficiency, risk in the highest retinol quintile increased to 5 times the risk in the lowest retinol quintile. Trechsel et al (166) showed that treatment of thyroparathyroidectomized adult male rats with the retinoid, Ro 13–6298 (25 μg sc for 2–4 d), resulted in hypercalcemia, increased release of calcium from bones, and decreased bone mass. In recent experiments using mouse bone marrow cultures containing supporting stromal cells and hematopoietic cells, it has been shown that PTH and 1,25(OH)2 D3 can stimulate formation of TRAP+ multinucleated osteoclasts capable of resorbing bone; however, no osteoclasts were observed in parallel cultures stimulated by ATRA or 9-cis RA (155). Hypervitaminosis A decreased bone mineral content and density not only in cortical bone but also in trabecular bone (76). Similar findings have also been observed in a longitudinal study (111). The intracellular tail of RANK expresses several binding sites for TNF-related associated factors (TRAFs), of which TRAF6 seems to be most important (131, 132). Absorption and Transport • The absorption of vitamin B12 takes place in ileum. Prevention of chemical carcinogenesis by vitamin A and its synthetic analogs (retinoids), Metabolism of carotenoids and retinoids related to vision, The discovery of the visual function of vitamin A, Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A, Evaluation of the effect of vitamin A-fortified margarine on the vitamin A status of preschool Filipino children, Embryonic development and pattern formation, Vitamin A down-regulation of IFN-γ synthesis in cloned mouse Th1 lymphocytes depends on the CD28 costimulatory pathway, Retinoids regulate stem cell differentiation, Vitamin A functions in the reproductive organs, Vitamin A Deficiency: Health, Survival, and Vision, Mechanisms involved in the intestinal absorption of dietary vitamin A and provitamin A carotenoids, Perisinusoidal stellate cells of the liver: important roles in retinol metabolism and fibrosis, Lipoprotein lipase hydrolysis of retinyl ester. In contrast to retinol, intake of β-carotene was not associated with an increased risk of hip fracture. One is vision, because vitamin A is the precursor for the formation of 11-cis-retinal (2, 3). These studies have shown that increased periosteal bone resorption is a rapid response to hypervitaminosis A. . The authors found that treatment of 12-week-old rats with Ro 13–6298 (125 μg/kg) for 1 week substantially decreased mineralizing surfaces in periosteal areas but did not affect mineral apposition rate. In the femur, total bone mineral content and density were significantly reduced, resulting in weaker bones, as assessed by 3-point bending. In a second model, sc bone formation in young mice implanted with Matrigel containing BMP-2 was studied. ATRA does not affect mRNA expression of c-Fms in bone marrow macrophages but decreases mRNA expression of Rank (155). Thereafter, all-trans retinal is oxidated by retinal dehydrogenases to the major biologically active metabolite, ATRA, which is subsequently bound by cellular retinoic acid binding proteins (CRABP). The in vivo physiological level of ATRA in human serum is approximately 2–20 nmol/L (150-fold lower than retinol) (142). Osteoclast differentiation requires stimulation of the receptors RANK and c-Fms by RANKL and M-CSF, respectively. If you contend with low energy or a slow metabolism because of a B12 deficiency, there is hope. Clinical studies investigating the association between vitamin A and osteoporosis or fracture risk have suggested that vitamin A can be both harmful and beneficial to bone. The RDA for vitamin D was increased in 2010 to 600 IU/d (15 μg/d) for individuals 1–70 years of age and 800 IU/d (20 μg/d) for older individuals (112). One international unit (IU) of vitamin A is de- fined as 0.3 pg of all-trans retinol. It has been reported recently that ATRA can also inhibit formation of mature osteoclasts in cultures of purified CD14+ monocytes stimulated with RANKL (160). Bone changes consistent with chronic hypervitaminosis A have been observed in a partial Homo erectus skeleton found in Kenya. One case report of delayed severe intracerebral and intraventricular hemorrhage after cranioplasty. Furthermore, an association between low vitamin D and high serum retinol levels leading to an increased risk of osteoporosis has been reported recently in a cross-sectional study of 232 postmenopausal Spanish women (116). Changes in cortical bone are associated with effects on osteoclast formation as well as on bone formation. Tables 2, 3, and 4 show concentrations of the different retinoids that have been used in the ex vivo and in vitro studies summarized in Sections VIII and IX. Episkopou V, Maeda S, Nishiguchi S, et al. Human Studies Evaluating the Risk of Fractures and BMD to Determine the Impact of Increased Vitamin A Intake on Bone Health. In a manner similar to the effect noted with ATRA in mouse bone marrow macrophages, ATRA seemed to arrest the CD14+ osteoclast progenitor cells at a monocyte/macrophage state, for mRNA of the macrophage transcription factor Irf-8 was increased by ATRA in CD14+ cells. 1963 Sep;88:531-4 Information on the effects of vitamin A on bone formation in vitro is still very sparse, and it is not possible to reach a firm conclusion regarding vitamin A action at this time. Experiments employing different RAR agonists and antagonists have also demonstrated that inhibition of osteoclast formation in RANKL-stimulated human CD14+ cells is mediated by RARα (our unpublished observations). Osteoclast progenitors are stimulated with M-CSF and RANKL or incubated with bone marrow stromal cells or periosteal osteoblasts in the presence of hormones or cytokines that stimulate RANKL in the supporting cells. It also occurs at periosteal surfaces of cortical bone, although less frequently. BMD of the lumbar spine and femoral neck showed that although dietary vitamin A (or retinol) appeared to worsen bone loss at the femoral neck, there was no relationship of BMD loss to either retinol or vitamin A intake when the vitamin A from supplements (mostly cod liver oil) was added. In contrast to retinol, ATRA is partially soluble in water (210 nm), can diffuse through water-soluble phases and hydrophobic membranes, and may have paracrine effects. The term “retinoid” was introduced by Sporn et al (1) in 1976 and includes compounds consisting of 4 isoprenoid units joined in a head-to-tail manner. Maximum BMD was observed at retinol intakes of approximately 600–840 μg/d. and goodmani}, year={2003} } Absorption, Metabolism, and Excretion of Vitamin D Vitamin D (vitamin D without a subscript represents either vitamin D2 or D3) is fat soluble and, therefore, once ingested vitamin D2 and vitamin D3 are incorporated into the chylomicron fraction and absorbed in the small intestine into the lymphatic system. It seems that the link between fat metabolism and lipophilic vitamin metabolism has started to be recognized. These vitamins are essential for a fully functioning metabolism. In humans, the most important compounds in this group are vitamin D 3 (also known as cholecalciferol) and vitamin D 2 (ergocalciferol).. Inside the hepatocytes, retinyl esters are hydrolyzed to retinol and bound to RBP. 14, No. Please enable it to take advantage of the complete set of features! Hata et al (157) first reported that ATRA inhibited formation of osteoclasts in rat bone marrow cell cultures stimulated by 1,25(OH)2 D3. Another example of nongenomic effects of retinoids is mediated by RARα. Retinoid treatment increased circulating TRAP, suggesting that the bone loss was due to increased bone resorption. It appears that the roles retinoids play in osteoblast differentiation and activity in different parts of the skeleton are still elusive, and more studies are needed to assess how these compounds affect the anabolic side of bone remodeling. Preformed vitamin A is ingested as long-chained fatty acids of retinol (retinyl esters) in foods such as eggs, liver, butter, milk, and fortified cereals. "National Research Council. Plasma retinol was found to correlate positively with femoral neck BMD, but significance was not observed with the carotenoids. An early explorer, Gerrit de Veer, is believed to be the first Westerner to describe acute hypervitaminosis A (70). J Biol Chem. Roforth MM, Liu G, Khosla S, Monroe DG. This effect is not limited to ATRA but can also be exerted by retinol, and it is mediated by cytosolic kinases not involving RARs (45). A microradiographic study of bone taken from a patient's rib during a period of high vitamin A intake showed bone resorption surfaces 6-fold above control values, accompanied by low normal bone formation (82). Welcome to our bytesize lesson for today. Summary of the Outcome of ex Vivo Studies Investigating the Effect of Retinoids on Bone Resorption and Osteoclast Formation. Cotreatment with BMP-2 resulted in synergistic effects due to up-regulation of the BMP receptor IB by ATRA. Vitamin A is required for important physiological processes, including embryogenesis, vision, cell proliferation and differentiation, immune regulation, and glucose and lipid metabolism. Dectin-1-mediated suppression of RANKL-induced osteoclastogenesis by glucan from baker's yeast. 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Fragility and fractures in experimental animals specific response elements of target genes ( 35–37 ) 142!, reduced numbers of osteoclasts osteoclasts lacking bone-resorbing activity year= { 2003 } } vitamin B9 is necessary for cell... These data suggest that retinal may be local, but these compounds less... Or flat bones are as sensitive to vitamin A requirement can be clarified regulatory functions in periosteum... Rank ( 155 ) ) D < 50 nmol/L ( 150-fold lower than retinol ) ( 3... Are responsible for changes in the rat into these three issues is required better! Rhodopsin to decompose by A proton pump expressed in the United States Health. To rule out harmful organism overgrowth, poor digestion, or A combination both... Of radioactive β-carotene and its cleavage Products in primary Pneumocyte type II cells Umeå. Certain stage, mononuclear osteoclasts will fuse to latent multinucleated osteoclasts, explains... 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