Temporally-regulated retinoic acid depletion produces specific neural crest, ocular and nervous system defects

Both retinoid receptor null mutants and classic nutritional deficiency studies have demonstrated that retinoids are essential for the normal development of diverse embryonic structures (e.g. eye, heart, nervous system, urogenital tract). Detailed analysis of retinoid-modulated events is hampered by several limitations of these models, including that deficiency or null mutation is present throughout gestation, making it difficult to isolate primary effects, and preventing analysis beyond embryolethality. We developed a mammalian model in which retinoid-dependent events are documented during distinct targeted windows of embryogenesis. This was accomplished through the production of vitamin A-depleted (VAD) female rats maintained on sufficient oral retinoic acid (RA) for growth and fertility. After mating to normal males, these RA-sufficient/VAD females were given oral RA doses which allowed for gestation in an RA-sufficient state; embryogenesis proceeded normally until retinoids were withdrawn dietarily to produce a sudden, acute retinoid deficiency during a selected gestational window. In this trial, final RA doses were administered on E11.5, vehicle at E12.5, and embryos analyzed on E13.5; during this 48 hour window, the last RA dose was metabolized and embryos progressed in a retinoid-deficient state. RA-sufficient embryos were normal. Retinoid-depleted embryos exhibited specific malformations of the face, neural crest, eyes, heart, and nervous system. Some defects were phenocopies of those seen in null mutant mice for RXR alpha(−/−), RXR alpha(−/−)/RAR alpha(−/−), and RAR alpha(−/−)/RAR gamma(−/−), confirming that RA transactivation of its nuclear receptors is essential for normal embryogenesis. Other defects were unique to this deficiency model, showing that complete ligand ‘knock-out’ is required to see those retinoid-dependent events previously concealed by receptor functional redundancy, and reinforcing that retinoid receptors have separate yet overlapping contributions in the embryo. This model allows for precise targeting of retinoid form and deficiency to specific developmental windows, and will facilitate studies of distinct temporal events.

Beta-carotene reduces body adiposity of mice via BCMO1

Evidence from cell culture studies indicates that β-carotene-(BC)-derived apocarotenoid signaling molecules can modulate the activities of nuclear receptors that regulate many aspects of adipocyte physiology. Two BC metabolizing enzymes, the BC-15,15′-oxygenase (Bcmo1) and the BC-9′,10′-oxygenase (Bcdo2) are expressed in adipocytes. Bcmo1 catalyzes the conversion of BC into retinaldehyde and Bcdo2 into β-10′-apocarotenal and β-ionone. Here we analyzed the impact of BC on body adiposity of mice. To genetically dissect the roles of Bcmo1 and Bcdo2 in this process, we used wild-type and Bcmo1^-/- mice for this study. In wild-type mice, BC was converted into retinoids. In contrast, Bcmo1^-/- mice showed increased expression of Bcdo2 in adipocytes and β-10′-apocarotenol accumulated as the major BC derivative. In wild-type mice, BC significantly reduced body adiposity (by 28%), leptinemia and adipocyte size. Genome wide microarray analysis of inguinal white adipose tissue revealed a generalized decrease of mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ) target genes. Consistently, the expression of this key transcription factor for lipogenesis was significantly reduced both on the mRNA and protein levels. Despite β-10′-apocarotenoid production, this effect of BC was absent in Bcmo1^-/- mice, demonstrating that it was dependent on the Bcmo1-mediated production of retinoids. Our study evidences an important role of BC for the control of body adiposity in mice and identifies Bcmo1 as critical molecular player for the regulation of PPARγ activity in adipocytes

Liquid chromatographic method for the determination of carotenoids, retinoids and tocopherols in human serum and in food

A liquid chromatographic (LC) method has been developed for the quantitative measurement of the six major carotenoids in human serum (lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, and beta-carotene) as well as retinol, retinyl palmitate, alpha-tocopherol, gamma-tocopherol, and delta-tocopherol. Several polar carotenoids, 2',3'-anhydrolutein, alpha-cryptoxanthin, and geometric isomers of lycopene and beta-carotene are also separated. Retinoids and carotenoids are monitored using a programmable ultraviolet-visible detector, while tocopherols are monitored using a fluorescence detector. The method uses a gradient containing acetonitrile, methanol, and ethyl acetate. Ammonium acetate is introduced with the methanol to minimize carotenoid losses on the LC column aggravated by the use of acetonitrile and ethyl acetate. The method is also applicable to the analysis of foods.

Chromatographic analysis of endogenous retinoids in tissues and serum

We present a reliable, highly sensitive, and versatile method for the simultaneous determination of endogenous polar (acidic) and apolar (retinol, retinal, and retinyl esters) retinoids in various biological matrices. Following a single liquid extraction of retinoids from tissues or plasma with isopropanol, polar retinoids are separated from apolar retinoids and neutral lipids via automated solid-phase extraction using an aminopropyl phase. After vacuum concentration to dryness and reconstitution of the residue in appropriate solvents, the obtained fractions are injected onto two different high-performance liquid chromatography (HPLC)-systems. Polar retinoids are analyzed on a RP18 column (2.1mm ID) using a buffered gradient composed of methanol and water and on-column-focusing large-volume injection. Apolar retinoids are separated on a normal-bore RP18 column using a nonaqueous gradient composed of acetonitrile, chloroform, and methanol. Both HPLC systems are coupled with UV detection, and retinoids are quantitated against appropriate internal standards. The method was validated with regard to recovery, precision, robustness, selectivity, and analyte stability. Using 400 microl serum or 200mg tissue, the limits of detection for all-trans-retinoic acid were 0.15ng/ml or 0.3ng/g, respectively. The corresponding values for retinol were 1.2ng/ml or 2.4ng/g, respectively. This method was successfully applied to mouse, rat, and human tissue and serum samples.

Muco-cutaneous retinoid-effects and facial erythema related to the novel triazole antifungal agent voriconazole

Voriconazole is a new azole antifungal drug with activity against a wide range of systemic fungal pathogens, including Aspergillus spp. Five patients with chronic invasive aspergillosis were treated for 12-58 weeks with voriconazole, 200 mg twice daily and developed facial erythema and cheilitis. One who received 58 weeks of therapy also developed discoid lupus erythematosus-like lesions on both sides of her neck. Both erythema and cheilitis resolved after discontinuation of voriconazole. Serum retinoids were elevated in the three patients in whom they were measured. Voriconazole has the potential for retinoid-like side-effects and facial erythema.

A sensitive and specific method for measurement of multiple retinoids in human serum with UHPLC-MS/MS

Retinol (vitamin A) circulates at 1-4 μM concentration and is easily measured in serum. However, retinol is biologically inactive. Its metabolite, retinoic acid (RA), is believed to be responsible for biological effects of vitamin A, and hence the measurement of retinol concentrations is of limited value. A UHPLC-MS/MS method using isotope-labeled internal standards was developed and validated for quantitative analysis of endogenous RA isomers and metabolites. The method was used to measure retinoids in serum samples from 20 healthy men. In the fed state, the measured concentrations were 3.1 ± 0.2 nM for atRA, 0.1 ± 0.02 nM for 9-cisRA, 5.3 ± 1.3 nM for 13-cisRA, 0.4 ± 0.4 nM for 9,13-dicisRA, and 17.2 ± 6.8 nM for 4oxo-13-cisRA. The concentrations of the retinoids were not significantly different when measured after an overnight fast (3.0 ± 0.1 nM for atRA, 0.09 ± 0.01 nM for 9-cisRA, 3.9 ± 0.2 nM for 13-cisRA, 0.3 ± 0.1 nM for 9,13-dicisRA, and 11.9 ± 1.6 nM for 4oxo-13-cisRA). 11-cisRA and 4OH-RA were not detected in human serum. The high sensitivity of the MS/MS method combined with the UHPLC separation power allowed detection of endogenous 9-cisRA and 4oxo-atRA for the first time in human serum.

Concentrations and plasma-tissue-diet relationships of carotenoids, retinoids, and tocopherols in humans

Micronutrients, such as beta-carotene and vitamins A and E, are potential chemopreventive agents; however, their concentrations in human target tissues are largely unknown. Because these micronutrients may exert their action at the site of target tissues, the tissue concentrations of the micronutrients need to be determined. In this cross-sectional study, we have measured the concentrations of seven carotenoids, two retinoids, and two tocopherols in paired plasma, buccal mucosal cells (BMC), and skin samples from 96 healthy subjects (ages 26-82 yrs). The plasma-tissue, as well as the diet-plasma and diet-tissue relationships of the micronutrients, and the impact of various potential confounders on the micronutrient concentrations were evaluated. The micronutrient concentrations of plasma and BMC used in the evaluation were the average of three measurements over a one-month period. Our data indicated that 1) the correlations between the plasma and BMC (Spearman r = 0.40-0.91, p < 0.05) and the plasma and skin (r = 0.24-0.75, p < 0.05) concentrations of most micronutrients were significant in all subjects, suggesting that the status of these micronutrients in the BMC and skin may be estimated from their plasma concentrations; 2) the correlations between the diet and plasma/tissue concentrations of the micronutrients were generally not as strong as the plasma-tissue relationships; the diet-plasma and diet-tissue relationships of the carotenoids were particularly poor in the smokers; 3) the plasma and tissue concentrations of most micronutrients were lower in smokers than in nonsmokers and higher in vitamin supplement users than in nonsupplement users; the differences remained significant after adjustment for age, gender, and diet intake estimates; 4) among the seven carotenoids examined, lycopene was unique, because its concentration was not lower in smokers or higher in supplement users but was inversely associated with age.

Quantitative analysis of retinoids in biological fluids by high-performance liquid chromatography using column switching. I. Determination of isotretinoin and tretinoin and their 4-oxo metabolites in plasma

A fully automated gradient high-performance liquid chromatographic method for the determination of isotretinoin, tretinoin and their 4-oxo metabolites in plasma was developed, using the column-switching technique. After dilution with an internal standard solution containing 20% acetonitrile, 0.5 ml of the sample was injected onto a precolumn (17 X 4.6 mm I.D.), filled with C18 Corasil 37-53 micron. Proteins and polar plasma components were washed out using 1% ammonium acetate-acetonitrile (9:1, v/v) as mobile phase 1. After valve switching, the retained components were transferred to the analytical column in the backflush mode, separated by gradient elution and detected at 360 nm by UV detection. Using two coupled reversed-phase columns (125 mm long), the separation of cis and trans isomers was possible, and all four compounds could be quantified down to 2 ng/ml of plasma. The inter-assay precision in the concentration range 20-100 ng/ml was between 1.0 and 4.7% for all compounds.

Correlation between carotenoid concentrations in serum and normal breast adipose tissue of women with benign breast tumor or breast cancer

To evaluate the relationship between carotenoid concentrations in serum and breast tissue, we measured serum carotenoid concentrations and endogenous carotenoid levels in breast adipose tissue of women with benign breast tumor (n = 46) or breast cancer (n = 44). Before extraction, serum was digested with lipase and cholesterol esterase, and breast adipose tissue was saponified. Serum and tissue carotenoids were extracted with ether/hexane and measured by using HPLC with a C30 column. Serum retinoic acid was extracted with chloroform/methanol and measured using HPLC with a C18 column. There were no significant differences in serum carotenoids [lutein, zeaxanthin, cryptoxanthin (both alpha- and beta-), alpha-carotene, all-trans beta-carotene, 13-cis beta-carotene and lycopene], retinoids (retinol, all-trans and 13-cis retinoic acids), and alpha- and gamma- tocopherol concentrations between benign breast tumor patients and breast cancer patients. A substantial amount of 9-cis beta-carotene was present in adipose tissue and was the only carotenoid that had a significantly lower level in benign breast tumor patients than in breast cancer patients. Correlations between carotenoid concentrations in serum and in breast adipose tissue were determined by combining the data of the two groups. Concentrations of the major serum carotenoids except cryptoxanthin showed significant correlations with breast adipose tissue carotenoid levels. When the concentrations of serum carotenoids were adjusted for serum triglycerides or LDL, correlations between serum carotenoid concentrations and breast adipose tissue carotenoid levels markedly increased, including that of cryptoxanthin (P <0. 001). The strong correlation between serum carotenoid concentrations and endogenous breast adipose tissue carotenoid levels indicate that dietary intake influences adipose tissue carotenoid levels as well as serum concentrations, and that adipose tissue is a dynamic reservoir of fat-soluble nutrients.

Effects of potent inhibitors of the retinoid cycle on visual function and photoreceptor protection from light damage in mice

Regeneration of the chromophore 11-cis-retinal is essential for the generation of light-sensitive visual pigments in the vertebrate retina. A deficiency in 11-cis-retinal production leads to congenital blindness in humans; however, a buildup of the photoisomerized chromophore can also be detrimental. Such is the case when the photoisomerized all-trans-retinal is produced but cannot be efficiently cleared from the internal membrane of the outer segment discs. Sustained increase of all-trans-retinal can lead to the formation of toxic condensation products in the eye. Thus, there is a need for potent, selective inhibitors that can regulate the flux of retinoids through the metabolism pathway termed the visual (retinoid) cycle. Here we systematically study the effects of the most potent inhibitor of this cycle, retinylamine (Ret-NH2), on visual function in mice. Prolonged, sustainable, but reversible suppression of the visual function was observed by Ret-NH2 as a result of its storage in a prodrug form, N-retinylamides. Direct comparison of other inhibitors such as fenretinide and 13-cis-retinoic acid showed multiple advantages of Ret-NH2 and its amides, including a higher potency, specificity, and lower transcription activation. Our results also revealed that mice treated with Ret-NH2 were completely resistant to the light-induced retina damage. As an experimental tool, Ret-NH2 allows the replacement of the native chromophore with synthetic analogs in wild-type mice to better understand the function of the chromophore in the activation of rhodopsin and its metabolism through the retinoid cycle.

Reversed-phase gradient high-performance liquid chromatographic procedure for simultaneous analysis of very polar to nonpolar retinoids, carotenoids and tocopherols in animal and plant samples

A reversed-phase gradient high-performance liquid chromatographic (HPLC) procedure, which utilizes gradient elution and detection by a photodiode-array detector, has been developed to analyze simultaneously very polar retinoids, such as 4-oxo-retinoyl-beta-glucuronide, retinoyl beta-glucuronide and 4-oxo-retinoic acid; polar retinoids, such as retinoic acid and retinol; nonpolar retinoids, such as retinyl esters; along with xanthophylls, monohydroxy carotenoids, hydrocarbon carotenoids, and tocopherols. The procedure has been applied to the simultaneous analysis of retinoids, carotenoids, and tocopherols present in human serum and liver, rat serum and tissues, and for carotenoids in a number of fruits and vegetables. Bilirubin present in human serum can also be simultaneously analyzed. By this gradient HPLC procedure, 3.4-didehydroretinyl ester (vitamin A2 ester) has been identified as a minor constituent in a human liver sample. Lycopene was identified as a major carotenoid in one specimen of papaya fruit, and 5,6,5',6'-diepoxy-beta-carotene was characterized as a major carotenoid in one specimen of mango fruit.

Retinol-binding protein-deficient mice: biochemical basis for impaired vision

We reported previously that mice lacking plasma retinol-binding protein (RBP) are phenotypically normal except that they display impaired vision at the time of weaning. This visual defect is associated with greatly diminished eyecup levels of retinaldehyde and is reversible if the mutants are maintained for several months on a vitamin A-sufficient diet. Here we provide a biochemical basis for the visual phenotype of RBP-deficient mice. This phenotype does not result from inadequate milk total retinol levels since these are not different for RBP-deficient and wild-type mice. The eye, unlike all other tissues that have been examined, takes up dietary retinol very poorly. Moreover, compared to other tissues, the eye displays a strong preference for retinol uptake when retinol is delivered bound to RBP. The poor uptake of dietary retinol by the eye coupled with its marked ability to take up retinol from RBP, we propose, provides a basis for the impaired vision observed in weanling RBP-deficient mice. Further study of the mutants suggests that the impaired vision is reversible because the eyes of mutant mice slowly acquire sufficient retinol from the low levels of retinol present in their circulation either bound to albumin or present in lipoprotein fractions. Thus, the eye is unlike other tissues in the body in that it shows a very marked preference for acquiring retinol needed to support vision from the retinol-RBP complex and is unable to meet adequately its retinol need through uptake of recently absorbed dietary retinol. This provides an explanation for the impaired vision phenotype of RBP-deficient mice.

Subclinical hypervitaminosis A causes fragile bones in rats

Excessive intake of vitamin A has been associated with an increased risk of hip fracture in humans. This finding has raised the question of whether long-term intake of relatively moderate doses ("subclinical" hypervitaminosis A) contributes to fracture risk. Although it has been known for more than half a century that toxic doses of vitamin A lead to spontaneous fractures in rats, the lowest intake that induces adverse effects is not known, and the result of exposure to excessive doses that do not cause general toxicity has been rarely investigated. In this study, mature female rats were fed a standard diet with 12 IU vitamin A/g pellet (control, C), or standard diet supplemented with either 120 IU ("10 x C") or 600 IU ("50 x C") vitamin A/g pellet for 12 weeks. Fifteen animals were included in each group. The supplemented diets correspond to a vitamin A intake of approximately 1800 IU/day and 9000 IU/day, respectively. The latter dose is about one third of that previously reported to cause skeletal lesions. At the end of the study, serum retinyl esters were elevated 4- (p < 0.01) and 20-fold (p < 0.001) and the total amount of liver retinoid had increased 3- (p < 0.001) and 7-fold (p < 0.001) in the 10 x C and 50 x C group, respectively. The animals showed no clinical signs of general toxicity, and there were no significant bone changes in the 10 x C group. However, in the 50 x C group, a characteristic thinning of the cortex (cortical area -6.5% [p < 0.001]) and reduction of the diameter of the long bones were evident (bone cross-sectional area -7.2% [p < 0.01] at the midshaft and -11.0% [p < 0.01] at the metaphysis), as measured by peripheral quantitative computed tomography. In agreement with these data and a decreased polar strength strain index (-14.0%, p < 0.01), the three-point bending breaking force of the femur was reduced by 10.3% (p < 0.01) in the 50 x C group. These data indicate that the negative skeletal effects appear at a subchronic vitamin A intake of somewhere between 10 and 50 times the standard diet. This level is considerably lower than previously reported. Our results suggest that long-term ingestion of modest excesses of vitamin A may contribute to fracture risk.

Chromatographic and electrophoretic analysis of biomedically important retinoids

The determination of retinol (vitamin A) and its metabolites, as well as synthetic retinoids, in biological samples is a challenging task due to the sensitivity of these compounds to light, heat and oxygen, high protein binding, separation of geometric isomers and determination of low endogenous levels. Numerous procedures for sample preparation have been published for biological fluids and tissues, consisting of solvent extraction, solid-phase extraction (off-line) and HPLC with column switching (on-line solid-phase extraction). The last-mentioned technique has several advantages, including a high degree of automation, no evaporation of extraction solvents, protection from light and higher sensitivity. Due to the favourable UV characteristics of most retinoids, HPLC with UV detection is most often employed, and photodiode array detection is becoming more and more popular. Fluorescence and electrochemical detection have found only a limited field of application, but the use of LC-MS resulted in a few highly sensitive methods. Reconsideration of GC through the use of better deactivated columns and cold on-column injection and evaluation of new promising separation methods, such as supercritical fluid chromatography and capillary electrophoresis, have shown preliminary encouraging results, but appear to reach the required sensitivity only by coupling to MS. Therefore, HPLC with UV detection is still the method of choice for highly sensitive and selective retinoid determination, as well as for high sample throughput and robustness.

Polychlorinated and polybrominated biphenyl congeners and retinoid levels in rat tissues: structure-activity relationships

The purpose of this study was to examine the structural requirements of polychlorinated and polybrominated biphenyls (PCBs and PBBs) for altering tissue levels of retinoids. Seven congeneric PCBs and PBBs were studied: 3,3',4,4'-tetrachlorobiphenyl (TCB), 2',3,3',4,5- and 3,3',4,4',5-pentachlorobiphenyls (-PeCBs), 3,3',4,4'- and 3,3',5,5'-tetrabromobiphenyls (-TBBs), 2,2',3,3',5,5'-hexachlorobiphenyl (-HCB), and 3,3',4,4',5,5'-hexabromobiphenyl (-HBB). Male Sprague-Dawley rats were fed a vitamin A-adequate diet (1.3 mg/kg) for 30 days before being given a single IP injection of one of seven polyhalogenated biphenyls (150 mumol/kg) in corn oil (10 ml/kg) or vehicle alone. Rats were killed 1 week later. Except for 3,3',4,4',5,5'-HBB, all PCBs and PBBs studied significantly decreased serum retinol levels and, except for 3,3',4,4',5,5'-HBB and 2,2',3,3',5,5'-HCB, all PCBs and PBBs also lowered the serum retinol-binding-protein (RBP) content. The activity of hepatic retinyl ester hydrolase (REH) was reduced by the treatment of 3,3',4,4',5-PeCB, 3,3',4,4'-TBB, and 3,3',4,4',5,5'-HBB. The levels of hepatic retinol were decreased by 2,2',3,3',5,5'-HCB, 2',3,3',4,5-PeCB, and 3,3',4,4',5-PeCB, while levels of hepatic retinyl palmitate were decreased by 2',3,3',4,5-PeCB, 3,3',4,4',5-PeCB, 3,3',4,4'-TCB, 3,3',4,4'-TBB, and 3,3',4,4',5,5'-HBB. The substantial decreases in hepatic retinyl palmitate levels could not be explained solely on the basis of hepatomegaly caused by acutely toxic PCBs and PBBs. All halogenated biphenyls which caused a decrease in hepatic retinyl palmitate also caused an increase in renal retinyl palmitate except 3,3',4,4',5-PeCB. In summary, the acutely toxic (nonortho substituted) congeners had pronounced effects on hepatic, renal, and serum retinoids whereas other biphenyls only decreased serum retinol levels. The effects of these seven compounds on REH activity were not correlated with the effects on serum retinol or RBP levels. Therefore, this study shows that the structure-activity relationships for altering hepatic retinoids differ from those for serum retinol, implying the involvement of multiple mechanisms.

Determination of several retinoids, carotenoids and E vitamers by high-performance liquid chromatography. Application to plasma and tissues of rats fed a diet rich in either beta-carotene or canthaxanthin

A method, using two different systems, is described for the high-performance liquid chromatographic analysis of retinol, retinal, retinoic acid, retinyl acetate, retinyl palmitate, alpha-, beta- and gamma-carotene, beta-apo-6'-, beta-apo-8', beta-apo-10'- and beta-apo-12'-carotenal, ethyl beta-apo-8'-carotenoate, alpha-tocopherol and alpha-tocopheryl acetate. The first system consists of a laboratory-packed Hypersil-ODS 3-microns column and a mobile phase of acetonitrile-methylene chloride-methanol-water (70:10:15:5, v/v). The second system consists of a laboratory-packed Hypersil-ODS 3-microns column and a mobile phase of acetonitrile-methylene chloride-methanol-water (70:10:15:5, v/v). The second system consists of a laboratory-packed Nucleosil C18 3-microns column and a mobile phase of acetonitrile-0.1 M ammonium acetate (80:20, v/v). The detection limits in standard solutions were 10 ng/ml for retinoids and carotenoids and 60 ng/ml for the E vitamers. Analysis of the tissues and plasma of rats, after 2 weeks on a diet supplemented with either beta-carotene or canthaxanthin (both 2 mg/g), led to the conclusion that the rats were able both to transport and store beta-carotene and canthaxanthin and to convert beta-carotene to retinol. Incubation of cytosol preparations from the mucosa of the small intestine of rat with 1 microgram of beta-carotene resulted in the formation of 10-20 ng of retinal within 1 h.

Tazarotene cream for the treatment of facial photodamage: a multicenter, investigator-masked, randomized, vehicle-controlled, parallel comparison of 0.01%, 0.025%, 0.05%, and 0.1% tazarotene creams with 0.05% tretinoin emollient cream applied once daily for 24 weeks

OBJECTIVE

To assess the safety and efficacy of 4 concentrations of tazarotene cream in the treatment of facial photodamage.

DESIGN

Prospective weekly multicenter, investigator-masked, randomized, parallel-group study.

SETTING

University hospitals and clinical research centers.

PATIENTS

Three hundred forty-nine subjects with facial photodamage.

INTERVENTION

Daily topical application of tazarotene cream (0.01%, 0.025%, 0.05%, and 0.1%) compared with its vehicle and with 0.05% tretinoin emollient cream.

RESULTS

Tazarotene cream and tretinoin cream significantly improved mottled hyperpigmentation and fine wrinkles. At week 24, treatment success rates based on global responses were 67% (39 of 58 subjects) with 0.1% tazarotene, 52% (30 of 58 subjects) with 0.05% tazarotene, 36% (21 of 58 subjects) with 0.025% tazarotene, 41% (24 of 59 subjects) with 0.01% tazarotene, 55% (32 of 58 subjects) with 0.05% tretinoin, and 22% (13 of 58 subjects) with vehicle. Local adverse events, although more frequent with tazarotene at higher concentrations, were generally mild to moderate.

CONCLUSIONS

Tazarotene in a cream formulation is safe and is associated with positive changes in the treatment of photodamaged facial skin.

Quantitative high-throughput determination of endogenous retinoids in human plasma using triple-stage liquid chromatography/tandem mass spectrometry

A high-throughput ultrasensitive analytical method based on liquid chromatography with positive ion atmospheric pressure chemical ionization (APCI) coupled to tandem mass spectrometric detection (LC/MS/MS) was developed for the determination of all-trans-4-oxo-retinoic acid (at4oxoRA), 13-cis-4-oxo-retinoic acid (13c4oxoRA), 13-cis-retinoic acid (13cRA), all-trans-retinoic acid (atRA) and all-trans-retinol (atROH) in human plasma. A stable isotope of atRA was used as internal standard (IS). The analytes and IS were isolated from 100 microL plasma by acetonitrile mono-phase extraction (MPE) performed in black 96-well microtiterplates. A 100 microL injection was focused on-column and chromatographed on an Agilent ZORBAX SB-C18 rapid-resolution high-throughput (RRHT) column with 1.8-microm particles (4.6 mmx50 mm) maintained at 60 degrees C. The initial mobile phase composition was acetonitrile/water/formic acid (10:90:0.1, v/v/v) delivered at 1.8 mL/min. Elution was accomplished by a fast gradient to acetonitrile/methanol/formic acid (90:10:0.1, v/v/v). The method had a chromatographic total run time of 7 min. An Applied Biosystems 4000 Q TRAP linear tandem mass spectrometer equipped with a heated nebulizer (APCI) ionization source was operated in multiple reaction monitoring (MRM) mode with the precursor-to-product ion transitions m/z 315.4-->297 (4-oxo-retinoic acids), 301.2-->205 (retinoic acids), 305.0-->209 (IS) and 269.2-->93 (retinol) used for quantification. The assay was fully validated and found to have acceptable accuracy, precision, linearity, sensitivity and selectivity. The mean extraction recoveries from spiked plasma samples were 80-105% for the various retinoids at three different levels. The intra-day accuracy of the assay was within 8% of nominal and intra-day precision was better than 8% coefficient of variance (CV) for retinoic acids. Inter-day precision results for quality control samples run over a 12-day period alongside clinical samples showed mean precision better than 12.5% CV. The limit of quantification was in the range of 0.1-0.2 ng/mL and the mass limit of detection (mLOD) was in the range 1-4 pg on column for the retinoic acids. The assay has been successfully applied to the analysis of 1700 plasma samples.

Identification of 9-cis-retinoic acid, 9,13-di-cis-retinoic acid, and 14-hydroxy-4,14-retro-retinol in human plasma after liver consumption

Vitamin A is a well-established teratogen in several animal species. Case reports as well as a recent epidemiological study suggest that vitamin A intake in excess of 25,000 or 10,000 IU respectively, can result in retinoid-specific defects in the offspring. A single meal of liver contains, on the average, a 10- to 20-fold higher amount of vitamin A than what is already suspected to be teratogenic. To evaluate the risk of liver consumption during pregnancy, we have studied levels of vitamin A and a number of potentially active retinoid metabolites in plasma of ten healthy male volunteers following consumption of fried turkey liver (2 g raw weight/kg body weight). HPLC, UV spectroscopy and mass spectrometry were used for identification and quantitation of retinoids in plasma. As shown previously, vitamin A intake via liver consumption resulted in greatly increased plasma levels of 13-cis-retinoic acid (13-cis-RA) and 13-cis-4-oxo-RA, and low levels of all-trans-RA and all-trans-4-oxo-RA. In our present investigation 9-cis-RA, 9,13-di-cis-RA, and 14-hydroxy-4,14-retro-retinol (14-HRR) were identified for the first time in humans as physiological metabolites of vitamin A. 9-cis-RA is a potent teratogen as well as a high affinity ligand of retinoid receptors, and 14-HRR was previously shown to promote lymphocyte activation in vitro. The present study bears on the issue of a possible teratogenic risk of liver consumption, as active retinoids were identified in human plasma, and their levels could be related to previous human studies as well as to experimental studies in sensitive animal species.

Normal serum response to oral beta-carotene in humans

This study was performed to determine (1) the normal serum response to a single oral dose of beta-carotene (BC), (2) the effect of meal timing and serum response to meal lipids on serum BC, (3) the effect of administered BC on other serum carotenoids and retinoids, and (4) the relationship of body composition to serum BC response. Subjects consumed one BC dose with a liquid 500 kcal BC-free diet; fasting and hourly venous blood was collected for 8 hours and again at 24 hours. A second liquid BC-free meal was consumed 4 hours post-dosing; this midday meal was omitted in some subjects. Serum BC levels rose and peaked initially at 5 hours, but continued to be absorbed in most subjects, remaining significantly elevated at 24 hours as compared to baseline values (p less than 0.001), independent of BC dose. The area under the BC absorption curve (8-hr AUC) increased linearly with BC dose and correlated positively with peak serum triglycerides (TG) after a meal (n = 26 tests, r = 0.56, p less than 0.003). Omission of the midday meal significantly delayed the initial BC peak to 7 hours (p less than 0.0004). Serum levels of retinol, alpha-carotene, cryptoxanthin, lycopene, and lutein remained unchanged. Serum retinyl esters did not rise in all subjects following BC intake; when it did, retinyl esters rose and peaked concomitantly with BC, but declined within 8 hours. There was no correlation between the initial serum BC, peak BC, 24-hr BC, 8-hr AUC, or peak serum TG and the percentage of body fat. We conclude that: (1) the timing of the serum response to oral BC is independent of dose, (2) the serum BC response is greater in those with a greater serum triglyceride response to meal lipids, (3) BC at the doses given does not alter the levels of other serum carotenoids, and (4) there is no correlation between the serum BC parameters measured and adiposity.

Hydroxypropylcyclodextrins in parenteral use. II: Effects on transport and disposition of lipids in rabbit and humans

Hydroxypropyl ethers of cyclodextrins, after parenteral administration, come into contact with lipids in tissues and in circulation and form water-soluble inclusion complexes with these lipids. A single intravenous administration of hydroxypropyl-beta-cyclodextrin to a hereditary hyperlipidemic Watanabe rabbit slightly and temporarily decreased the level of total cholesterol in serum. Single injections of hydroxypropyl-alpha-cyclodextrin and of the corresponding gamma-homologue, both of which are less potent solubilizers of cholesterol, had lesser effects. Repeated administration of hydroxypropyl-beta-cyclodextrin to rabbits led to a gradual increase in total cholesterol in circulation and eventually to a slight relief of atherosclerotic lesions in the thoracic aorta. The only untoward effects of repeated treatments (total doses of up to 40 g/kg) were vacuoles in cells of proximal convoluted tubules in the kidneys. Repeated administration also strongly increased cholesterol in urine, probably because of excretion of the soluble cholesterol-hydroxypropyl-beta-cyclodextrin complex. Proteins in urine increased significantly, whereas triglycerides increased only moderately after repeated administrations. Intravenous infusion of hydroxypropyl-beta-cyclodextrin into a patient with hypervitaminosis A led to a release of liver-stored retinoids into serum in quantities much higher than those that could be directly solubilized by hydroxypropyl-beta-cyclodextrin. Levels of total cholesterol in the circulation of this patient decreased during the infusion. Thus, hydroxypropylcyclodextrins may serve as artificial lipid carriers in the circulation, and because the exchanges that involve inclusion complexation occur very quickly, the presence of hydroxypropylcyclodextrins in organisms may catalytically augment the establishment of equilibria in lipid distribution.

Serum retinoids and beta-carotene as predictors of hip and other fractures in elderly women

There is debate about the possible deleterious effect of excessive vitamin A exposure on fracture risk. In this nested case control study in older women (312 cases and 934 controls), serum retinol, retinyl palmitate, and beta-carotene were not associated with fracture risk, and there was no evidence of excess risk with multivitamin or cod liver oil supplementation.

INTRODUCTION

Recent studies have suggested that higher vitamin A intake may account for a component of fracture risk within the general population and that supplemental vitamin A may be harmful even within recommended limits. No studies have examined the relationship between biochemical retinol status and fracture in older women.

MATERIALS AND METHODS

We examined serum retinol, retinyl palmitate, and beta-carotene as predictors of incident hip and other fractures in a large prospective study of British women over the age of 75 years (n = 2606, 312 incident osteoporotic fractures, 92 incident hip fractures; mean follow-up duration, 3.7 years). Fasting blood samples (9:00-11:00 a.m.) were collected at baseline. Using a case-control design (three controls per case), serum retinol, retinyl palmitate, and beta-carotene were assessed as univariate predictors of incident osteoporotic fracture or hip fracture. Baseline BMD at the total hip, age, 25(OH)D, serum beta Crosslaps, bone-specific alkaline phosphatase, weight, height, and smoking were considered as covariates in a multivariate model.

RESULTS

Serum retinol, retinyl palmitate, and beta-carotene were not significant univariate predictors of either hip fracture or any fracture (all p > 0.05; Cox proportional hazards regression). For all osteoporotic fractures, the hazard ratio (HR) was 0.92 (95% CI, 0.81-1.05) per 1 SD increase in serum retinol. Risk of any osteoporotic fracture was slightly less in the highest quartile of serum retinol compared with the lowest quartile (HR, 0.85; 95% CI, 0.69-1.05; p = 0.132) There was a tendency for increased serum retinol to predict benefit rather than harm in terms of BMD (r = 0.09, p = 0.002). Multivitamin or cod liver oil supplementation was associated with a significantly lower risk of any fracture (HR, 0.76; 95% CI, 0.60-0.96; p = 0.021). In multivariate analysis, only age, total hip BMD, and weight were associated with fracture risk (p < 0.05).

CONCLUSIONS

We found no evidence to support any skeletal harm associated with increased serum indices of retinol exposure or modest retinol supplementation in this population.

Isotretinoin improves the appearance of photodamaged skin: results of a 36-week, multicenter, double-blind, placebo-controlled trial

Photodamaged skin occurs as a result of long-term exposure to ultraviolet radiation. The incidence of photodamage in European and North American populations with Fitzpatrick skin types I, II, and III is estimated at 80% to 90%. We conducted a double-blind clinical trial to test the efficacy and safety of 0.1% isotretinoin versus vehicle cream in 800 patients with moderate to severe photodamaged skin. Patients applied either 0.1% isotretinoin or matching vehicle cream to the face, forearms, and hands once nightly for 36 weeks. Local irritation and adverse events were assessed, and plasma retinoid levels were measured before and during treatment. Treatment response increased throughout the 36-week treatment period and the overall appearance of photodamaged skin was significantly better than with the vehicle alone. Topical application of 0.1% isotretinoin is an effective and well-tolerated treatment leading to clinically apparent improvement in the appearance of photodamaged skin of the face, forearms, and hands.

Postchallenge plasma lipoprotein retinoids: chylomicron remnants in endogenous hypertriglyceridemia

This study was conducted to determine whether chylomicron remnants accumulate in the plasma of patients with "endogenous" hypertriglyceridemia. Retinyl esters were used as markers of chylomicrons and chylomicron remnants since they are carried mainly if not exclusively by lipoproteins of intestinal origin. Seventy-six fasting normotriglyceridemic and hypertriglyceridemic patients were studied 12 to 15 hours after ingesting 25,000 IU of vitamin A. Plasma retinol and retinyl esters were measured by reversed-phase high-performance liquid chromatography. Chylomicronemia was assessed by flotation at unit gravity and by chylomicron flocculation in 3% polyvinylpyrrolidone. Plasma lipids, retinoids, lipoprotein cholesterol, and the electrophoretic mobility of very-low density lipoproteins were determined in a subset of 36 subjects. Progressively elevated plasma retinyl ester concentrations were observed among patients with mild, moderate, and severe hypertriglyceridemia. All subjects with fasting chylomicronemia had retinyl ester retention. The majority of subjects with mild or moderate hypertriglyceridemia (predominantly type IV hyperlipoproteinemia) also had elevated plasma concentrations of retinyl esters. Total plasma retinyl ester and plasma triglyceride concentrations correlated significantly (rs = 0.721, P less than 0.001) in nonchylomicronemic subjects. In addition, total plasma retinol concentrations were mildly elevated among hypertriglyceridemic subjects because retinol, as well as retinyl esters, is transported by triglyceride-rich lipoproteins. If lipoprotein remnants are atherogenic in man, then chylomicron remnant retention may accelerate atherogenesis in hypertriglyceridemic individuals.

Antiepileptic drugs alter endogenous retinoid concentrations: a possible mechanism of teratogenesis of anticonvulsant therapy

The major antiepileptic drugs used for the control of seizures can induce developmental toxicity when administered during pregnancy. Vitamin A and retinoids are thought to control many processes of embryonic development including growth, differentiation and morphogenesis. We have therefore studied if the teratogenic action of antiepileptic agents could be mediated via alteration of the endogenous vitamin A--retinoid metabolism. Retinol and its oxidative metabolites all-trans-, 13-cis- and 13-cis-4-oxo-retinoic acid were measured in the plasma of 75 infants and children treated with various antiepileptic drugs for the control of seizures, and in 29 untreated controls of comparable age. Retinol levels increased with age, while the concentrations of retinoic acid compounds did not exhibit age-dependency. Valproic acid monotherapy increased retinol levels in the young age group and a trend toward increased retinol concentrations was also observed in all other patient groups. The plasma levels of the oxidative metabolites 13-cis- and 13-cis-4-oxo-retinoic acids were strongly decreased in all patient groups treated with phenytoin, phenobarbital, carbamazepine and ethosuximide, in combination with valproic acid, to levels which were below 1/3rd and 1/10th of corresponding control values, respectively. Little changes were observed with all-trans-retinoic acid except in one patient group treated with valproic acid/ethosuximide cotherapy where increased levels of this retinoid were found. Our study indicates that therapy with antiepileptic agents can have a profound effect on the endogenous retinoid metabolism. Because of the importance of retinoids for the signaling of crucial biological events during embryonic development, such altered retinoid metabolism may be highly significant in regard to antiepileptic drug teratogenesis.