Retinol plasma

Reduced plasma levels during the first developmental months have a considerable influence on the total development as well as on the susceptibility for infections of infants. With reduced retinol plasma levels. 

The method of Thurnham etal. (1988) was modified for the quantification of plasma j3C and retinol. Plasma extracts were dissolved in 40 /il of dimeth-ylforamide and vortexed and then 210 pil of acetonitrile/methanol/chloro-form (47/47/6, v/v/v) was added. Reconstituted samples were vortexed and sonicated for 40 sec prior to being transferred to autosampler vials and sealed under nitrogen. The HPLC system consisted of a photodiode array detector (Waters 9%, Miliipore Corp., Milford, MA) with Millennium software, a Waters 717 plus autosampler, and a Hewlett-Packard Model 1050 pump. Analytes of interest were separated using acetonitrile/methanol/ chloroform (47/47/6, v/v/v), with 0.05 M of ammonium acetate and 1% triethylamine at a flow rate of 1.2 ml/min and a 4.6 X 15-cm Spherisorb ODS-2 column (LKB Instruments Ltd., Surrey, UK) maintained at 26°C using a column heater (Timberline Instruments Ltd., Boulder, CO). This analysis does not discriminate between C-enriched and nonenriched analytes, but rather measures the total concentration of each isotopomer. The retention times of retinol, retinyl acetate (internal standard), and /3-carotene were 2.1, 2.6, and 16.9 min, respectively. Plasma concentrations of retinol and /3C were calculated using a standard curve for each analyte and an internal standard to correct for volume recovery. 

When liver vitamin A reserves fall below about 20-30 pg retinol g liver, the secretion of holo-RBP is compromised due to inadequate retinol. Plasma retinol levels begin to fall and, if liver vitamin A continues to decline, plasma levels will fall into the deficient range and will be inadequate to supply retinol to tissues. Essentially all of the vitamin A in liver can be mobilized when it is needed to meet the needs of peripheral tissues. But ultimately, vitamin A intake must increase to bring plasma retinol levels back to the normal range. 

More specific methods involve chromatographic separation of the retinoids and carotenoids followed by an appropriate detection method. This subject has been reviewed (57). Typically, hplc techniques are used and are coupled with detection by uv. For the retinoids, fluorescent detection is possible and picogram quantities of retinol in plasma have been measured (58—62). These techniques are particularly powerful for the separation of isomers. Owing to the thermal lability of these compounds, gc methods have also been used but to a lesser extent. Recently, the utiUty of cool-on-column injection methods for these materials has been demonstrated (63). 

The first example is the plasma-borne retinol-binding protein, RBP, which is a single polypeptide chain of 182 amino acid residues. This protein is responsible for transporting the lipid alcohol vitamin A (retinol) from its storage site in the liver to the various vitamin-A-dependent tissues. It is a disposable package in the sense that each RBP molecule transports only a single retinol molecule and is then degraded. 

RBP is synthesized in the hepatocytes, where it picks up one molecule of retinol in the endoplasmic reticulum. Both its synthesis and its secretion from the hepatocytes to the plasma are regulated by retinol. In plasma, the... 

Figure S.3 Schematic diagram of the structure of human plasma retinol-binding protein (RBP), which is an up-and-down P barrel. The eight antiparallel P strands twist and curl such that the structure can also be regarded as two p sheets (green and blue) packed against each other. Some of the twisted p strands (red) participate in both P sheets. A retinol molecule, vitamin A (yellow), is bound inside the barrel, between the two P sheets, such that its only hydrophilic part (an OH tail) is at the surface of the molecule. The topological diagram of this stmcture is the same as that in Figure 5.2. (Courtesy of Alwyn Jones, Uppsala, Sweden.)...

Figure S.S Amino acid sequence of p strands 2 3 4 in human plasma retinol-binding protein. The sequences are listed in such a way that residues which point into the barrel are aligned. These hydrophobic residues are arrowed and colored green. The remaining residues are exposed to the solvent.

Papiz, M.Z., et al. The structure of p-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986. 

R. Ruhl and H. Nau, Deteimination of adapalene (CD271/Differin ) and retinol in plasma and tissue by on-line solid-phase exti action and HPEC analysis , Chro-matographia 45 269-274 (1997). 

Subsequent studies have confirmed that the reason for this discrepancy is that the rat is able to rapidly metabolise P-carotene to retinol in the intestine, through the action of intestinal dioxygenase. In contrast humans absorb P-carotene systemically such that plasma levels of P-carotene increase to levels not found in the rodent. A more appropriate animal model is the ferret, which shows a similar metabolism to humans. High levels of plasma P-carotene in the ferret induce the cellular transcription factors c-fos and c-jun, and squamous metaplasia is seen in the lung with or without exposure to cigarette smoke (SCF, 2000). Even after the investment of all these resources it has not been possible for the EU Scientific Committee on Food to set an ADI. 

Novotny, J.A. et al.. Plasma appearance of labeled -carotene, lutein, and retinol in humans after consumption of isotopicaUy labeled kale, J. Lipid Res., 46, 1896, 2005. 

Azeredo, V. B. and N. M. Trugo (2008). Retinol, carotenoids, and tocopherols in the milk of lactating adolescents and relationships with plasma concentrations. Nutrition 24(2) 133-139. 

The other major class of extracellular LBPs of mammals is the lipocalins (Flower, 1996). These are approximately 20 kDa, P-sheet-rich proteins, performing functions such as the transport of retinol in plasma or milk, the capture of odorants in olfaction, invertebrate coloration, dispersal of pheromones, and solubilizing the lipids in tears (Flower, 1996). The retinol-binding protein (RBP) of human plasma is found in association with a larger protein, transthyretin, the complex being larger than the kidney threshold and thus not excreted, although the RBP itself may dissociate from the complex to interact with cell surface receptors in the delivery of retinol (Papiz et al., 1986 Sundaram et al., 1998). 

Carotene (all-trans), (3-cryptoxanthin (all-trans and -cis), zeaxanthin (all-trans), luteoxanthin isomers, violaxanthin (all-trans and -cis), and neoxanthin (all-trans and -cis) were identified in several mango cultivars (Mercadante and others 1997 Ornelas-Paz and others 2007, 2008). Mango retinol was found to be highly bioavail-able by estimating vitamin A and carotene reserves in the liver and plasma of rats. Information on the tocopherol content in mango is very scarce, but it seems to be low (Burns and others 2003 Ornelas-Paz and others 2007). 

McGuire, J.T., E.S. Dierenfeld, R.H. Poppenga, and W.E. Brazelton. 1989. Plasma alpha-tocopherol, retinol, cholesterol, and mineral concentrations in captive gorillas. Jour. Med. Primatol. 18 155-161. 

Ah-responsive and Ah-nonresponsive strains females, age 10 weeks given single ip injection of 50 mg/kg BW killed after 7 days Both groups had increased body weight, increased blood EROD activity, decreased plasma retinol levels, and increased plasma total thyroid hormone levels. The Ah-responsive group also had increased hepatic pentoxyresorufin-O-deethylase activity, increased livercytochrome P-450 activity, and increased liver weight 12... 

Gundersen and Blomhoff (1999) used online dilution with online SPE to measure vitamin A (retinol) and other active retinoids in animal plasma. The intention of online dilution in this application was on optimizing SPE extraction conditions rather than on peak focusing during analytical separation. An SPE cartridge packed with Bondapak C18 materials (37 to 53 jt/M, 300 A, Waters, Milford, Massachusetts) and a reversed-phase analytical column (250 x 2.1 mm inner diameter, Superlex pkb-100, Supelco, Bellefonte, Pennsylvania) were controlled by a six-port switching valve (Rheodyne, Cotati,... 

CONCENTRATIONS OF PLASMA RETINOL (1, NG/ML), LUTEIN (2, NG/ML), ZEAXANTHIN (3, NG/ ML), CANTHAXANTHIN (4, NG/ML) AND a-TOCOPHEROL (5, /xG/ML) IN CONTROL AND EXPERIMENTAL GREEN IGUANAS AFTER INGESTING DIETS SUPPLEMENTED WITH DIFFERENT CAROTENOIDS (80 MG/KG DIET) FOR 28 DAYS (MEAN S.D N = 5)... 

T.W. Knight and A.F. Death, Effects of oral and injected vitamin A (retinol) supplements on liver vitamin A and plasma carotenoid and cholesterol concentrations in cattle. Animal Sci. 69 (1999) 607-612. 

The overall metabolism of vitamin A in the body is regulated by esterases. Dietary retinyl esters are hydrolyzed enzymatically in the intestinal lumen, and free retinol enters the enterocyte, where it is re-esterified. The resulting esters are then packed into chylomicrons delivered via the lymphatic system to the liver, where they are again hydrolyzed and re-esterified for storage. Prior to mobilization from the liver, the retinyl esters are hydrolyzed, and free retinol is complexed with the retinol-binding protein for secretion from the liver [101]. Different esterases are involved in this sequence. Hydrolysis of dietary retinyl esters in the lumen is catalyzed by pancreatic sterol esterase (steryl-ester acylhydrolase, cholesterol esterase, EC 3.1.1.13) [102], A bile salt independent retinyl-palmitate esterase (EC 3.1.1.21) located in the liver cell plasma hydrolyzes retinyl esters delivered to the liver by chylomicrons. Another neutral retinyl ester hydrolase has been found in the nuclear and cytosolic fractions of liver homogenates. This enzyme is stimulated by bile salts and has properties nearly identical to those observed for... 

K2. Kanai, M., Raz, A., and Goodman, D. S., Retinol-binding protein the transport protein for vitamin A in human plasma. J. Clin. Invest. 47, 2025-2044 (1968). 

Repeatedly it was shown that the semm retinol level and RBP level in prematures are significantly lower than that of neonates (Shah and Rajalekshmi, 1984). In the liver of prematures, significantly lower retinol levels can be foimd in comparison to neonates (Shensi et ah, 1985). Plasma values lower than 20 gg/dl are not rare in this case and they should be taken as an indicator of a relative vitamin A deficit. But a moderate vitamin A deficiency is not only a problem of countries with poor or inadequate food sources. 

Recently we published data that even in countries with excellent food sources and availability, insufficient vitamin A supply will occur (Schulz et ah, 2007). The aim of this trial was to analyze vitamin A and p-carotene status and investigate the contribution of nutrition to vitamin A and p-carotene supply in mother-infant pairs of multiparous births or births within short birth rates. Twenty-nine volimteers aged between 21 and 36 years were evaluated for 48 hours after delivery. In order to establish overall supply, retinol and p-carotene were determined in maternal plasma, cord blood, and colostrum via HPLC analysis. A food frequency protocol was obtained from all participants. Regardless of the high-to-moderate socioeconomic background, 27.6% of participants showed plasma retinol levels below 1.4 pmol/liter, which can be taken as borderline deficiency. In addition, 46.4% showed retinol intake <66% of RDA and 50.0% did not consume liver at all, although liver contributes as a main source for preformed retinol. Despite a high total carotenoid intake of 6.9 3.9mg/day, 20.7% of mothers showed plasma levels <0.5 pmol/liter p-carotene. 

Retinol and p-carotene levels were highly significant correlated between maternal plasma versus cord blood and colostrum. In addition, significantly lower levels were found in cord blood [31.2 13% (retinol), 4.1 1.4% (p-carotene)] compared with maternal plasma. Despite the fact that vitamin A- and p-carotene-rich food is generally available, in contrast to developing countries, risk groups for low vitamin A supply indeed exist in the western world. 

Biesalski, FI. K. (1996). Effects of intratracheal application of vitamin A on concentrations of retinol derivates in plasma, lungs and selected tissue of rats. Int. ]. Vitam. Nutr. Res. 66, 106-112. 

Although the majority of analytes do not possess natural fluorescence, the fluorescence detector has gained popularity due to its high sensitivity. The development of derivatization procedures used to label the separated analytes with a fluorescent compound has facilitated the broad application of fluorescence detection. These labeling reactions can be performed either pre- or post-separation, and a variety of these derivatization techniques have been recently reviewed by Fukushima et al. [18]. The usefulness of fluorescence detectors has recently been further demonstrated by the Wainer group, who developed a simple HPLC technique for the determination of all-trani-retinol and tocopherols in human plasma using variable wavelength fluorescence detection [19]. 

In the body retinol can also be made from the vitamin precursor carotene. Vegetables like carrots, broccoli, spinach and sweet potatoes are rich sources of carotene. Conversion to retinol can take place in the intestine after which retinyl esters are formed by esterifying retinol to long chain fats. These are then absorbed into chylomicrons. Some of the absorbed vitamin A is transported by chylomicrons to extra-hepatic tissues but most goes to the liver where the vitamin is stored as retinyl palmitate in stellate cells. Vitamin A is released from the liver coupled to the retinol-binding protein in plasma. 

Vitamin A absorption from the small intestine requires dietary fat and pancreatic lipase to break down retinyl esters and bile salts to promote the uptake of retinol and carotene. Drugs, such as mineral oil, neomycin and cholestyramine, that can modify lipid absorption from the gastrointestinal tract can impair vitamin A absorption. The use of oral contraceptives can signihcantly increase plasma vitamin A levels. 

Pharmacokinetics Rapidly absorbed from the GI tract if bile salts, pancreatic lipase, protein, and dietary fat are present. Transported in blood to the liver, where it s metabolized stored in parenchymal hepatic cells, then transported in plasma as retinol, as needed. Excreted primarily in bile and, to a lesser extent, in urine. 

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