Limited appearance of apocarotenoids is observed in plasma after consumption of tomato juices: a randomized human clinical trial.

Background: Nonvitamin A apocarotenoids occur in foods. Some function as retinoic acid receptor antagonists in vitro, though it is unclear if apocarotenoids are absorbed or accumulate to levels needed to elicit biological function. Objective: The aim of this study was to quantify carotenoids and apocarotenoids (ß-apo-8'-, -10'-, -12'-, and -14'-carotenal, apo-6'-, -8'-, -10'-, -12'-, and -14'-lycopenal, retinal, acycloretinal, ß-apo-13-carotenone, and apo-13-lycopenone) in human plasma after controlled consumption of carotenoid-rich tomato juices. Design: Healthy subjects (n = 35) consumed a low-carotenoid diet for 2 wk, then consumed 360 mL of high-ß-carotene tomato juice (30.4 mg of ß-carotene, 34.5 µg total ß-apocarotenoids/d), high-lycopene tomato juice (42.5 mg of lycopene, 119.2 µg total apolycopenoids/d), or a carotenoid-free control (cucumber juice) per day for 4 wk. Plasma was sampled at baseline (after washout) and after 2 and 4 wk, and analyzed for carotenoids and apocarotenoids using high-pressure liquid chromatography (HPLC) and HPLC-tandem mass spectrometry, respectively. The methods used to analyze the apocarotenoids had limits of detection of ∼ 100 pmol/L. Results: Apocarotenoids are present in tomato juices at 0.1-0.5% of the parent carotenoids. Plasma lycopene and ß-carotene increased (P < 0.001) after consuming high-lycopene and ß-carotene tomato juices, respectively, while retinol remained unchanged. ß-Apo-13-carotenone was found in the blood of all subjects at every visit, although elevated (P < 0.001) after consuming ß-carotene tomato juice for 4 wk (1.01 ± 0.27 nmol/L) compared with both baseline (0.37 ± 0.17 nmol/L) and control (0.46 ± 0.11 nmol/L). Apo-6'-lycopenal was detected or quantifiable in 29 subjects, while ß-apo-10'- and 12'-carotenal were detected in 6 and 2 subjects, respectively. No other apolycopenoids or apocarotenoids were detected. Conclusions: ß-Apo-13-carotenone was the only apocarotenoid that was quantifiable in all subjects, and was elevated in those consuming high-ß-carotene tomato juice. Levels were similar to previous reports of all-trans-retinoic acid. Other apocarotenoids are either poorly absorbed or rapidly metabolized or cleared, and so are absent or limited in blood. ß-Apo-13-carotenone may form from vitamin A and its presence warrants further investigation. This trial was registered at clinicaltrials.gov as NCT02550483.

Maternal Retinoids Increase PDGFRα+ Progenitor Population and Beige Adipogenesis in Progeny by Stimulating Vascular Development.

Maternal vitamin A intake varies but its impact on offspring metabolic health is unknown. Here we found that maternal vitamin A or retinoic acid (RA) administration expanded PDGFRα+ adipose progenitor population in progeny, accompanied by increased blood vessel density and enhanced brown-like (beige) phenotype in adipose tissue, protecting offspring from obesity. Blockage of retinoic acid signaling by either BMS493 or negative RA receptor (RARαDN) over-expression abolished the increase in blood vessel density, adipose progenitor population, and beige adipogenesis stimulated by RA. Furthermore, RA-induced beige adipogenesis was blocked following vascular endothelial growth factor receptor (VEGFR) 2 knock out in PDGFRα+ cells, suggesting its mediatory role. Our data reveal an intrinsic link between maternal retinoid level and offspring health via promoting beige adipogenesis. Thus, enhancing maternal retinoids is an amiable therapeutic strategy to prevent obesity in offspring, especially for those born to obese mothers which account for one third of all pregnancies.

Serum levels of lipid metabolites in age-related macular degeneration.

Age-related macular degeneration (AMD) is a neurodegenerative disease that causes adult-onset blindness. There are 2 forms of this progressive disease: wet and dry. Currently there is no cure for AMD, but several treatment options have started to emerge making early detection critical for therapeutic success. Analysis of the eyes of Abca4(-/-)Rdh8(-/-) mice that display light-induced retinal degeneration indicates that 11-cis-retinal and docosahexaenoic acid (DHA) levels were significantly decreased as compared with the eyes of control dark-adapted C57BL/6J mice. In addition, exposure to intense light correlated with higher levels of prostaglandin G2 in the eyes of Abca4(-/-)Rdh8(-/-) mice. Intense light exposure also lowered DHA levels in the eyes of wild-type C57BL/6J mice without discernible retinal degeneration. Analysis of human serum from patients with AMD recapitulated these dysregulated DHA levels and revealed dysregulation of arachidonic acid (AA) levels as well (∼32% increase in patients with AMD compared with average levels in healthy individuals). From these observations, we then built a statistical model that included levels of DHA and AA from human serum. This model had a 74% probability of correctly identifying patients with AMD from controls. Addition of a genetic analysis for one of the most prevalent amino acid substitutions in the age-related maculopathy susceptibility 2 gene linked to AMD, Ala(69)→Ser, did not improve the statistical model. Thus, we have characterized a reliable method with the potential to detect AMD without a genetic component, paving the way for a larger-scale clinical evaluation. Our studies on mouse models along with the analysis of human serum suggest that our small molecule-based model may serve as an effective tool to estimate the risk of developing AMD.

Quantitation of retinaldehyde in small biological samples using ultrahigh-performance liquid chromatography tandem mass spectrometry.

We report an ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method to quantify all-trans-retinal in biological samples of limited size (15-35mg), which is especially advantageous for use with adipose. To facilitate recovery, retinal and the internal standard 3,4-didehydroretinal were derivatized in situ into their O-ethyloximes. UHPLC resolution combined with high sensitivity and specificity of MS/MS allowed quantification of retinal-O-ethyloximes with a 5-fmol lower limit of detection and a linear range from 5fmol to 1pmol. This assay revealed that extraocular concentrations of retinal range from approximately 2 to 40pmol/g in multiple tissues-the same range as all-trans-retinoic acid. All-trans-retinoic acid has high affinity (kd⩽0.4nM) for its nuclear receptors (RARα, -ß, and -γ), whereas retinal has low (if any) affinity for these receptors, making it unlikely that these retinal concentrations would activate RAR. We also show that the copious amount of vitamin A used in chow diets increases retinal in adipose depots 2- to 5-fold relative to levels in adipose of mice fed a vitamin A-sufficient diet, as recommended for laboratory rodents. This assay also is proficient for quantifying conversion of retinol into retinal in vitro and, therefore, provides an efficient method to study metabolism of retinol in vivo and in vitro.

Expression of keratinocyte transglutaminase in cornea of vitamin A-deficient rats.

PURPOSE: To determine the role played by keratinocyte transglutaminase (TG1, TG(K)) in the abnormal keratinization of the cornea. METHODS: Vitamin A-deficient rats were produced as a model of severe dry eyes, and the expression of the mRNA and the enzyme activity of TG1 were examined in the corneas. The envelope proteins and keratins of cornified cells were also examined immunohistochemically. RESULTS: The expression and enzyme activity of TG1 mRNA on the ocular surface were significantly upregulated as the vitamin A deficiency developed. As the TG1 expression was upregulated, involucrin, loricrin, and keratin 10 began to be expressed on the epithelial cells of the cornea. CONCLUSIONS: Upregulation of TG1 expression followed by the appearance of the envelope proteins and keratin10 in cornified cells indicated that TG1 is involved in the abnormal keratinization of the cornea.

Retinals and retinols induced by estrogen in the blood plasma of Xenopus laevis.

Injection of estrogen into male Xenopus laevis induced the appearance of retinals (retinal and 3-dehydroretinal) and a considerable increase in the amount of retinols (retinol and 3-dehydroretinol) in the blood plasma. These retinoids were mainly in the all-trans form. Without estrogen injection, retinols were normally found in the blood plasma of both males and females, but only trace amounts of retinals were detected and these were restricted to the plasma of females. The proteins in the blood plasma of estrogen-injected males were separated into two fractions. One fraction included vitellogenin, the precursor of egg yolk proteins, and the other contained some plasma proteins other than vitellogenin. Retinals were detected in the former and retinols in the latter. It is suggested that retinals are bound to vitellogenin and are taken up into oocytes in the process of vitellogenesis.

Xerophthalmia in Ethiopia: a nationwide ophthalmological, biochemical and anthropometric survey.

A total of 6636 children, aged from 6 months to 6 years and selected throughout the country using a multi-staged stratified sample design, were examined for signs of xerophthalmia. The concentrations of retinol and of beta-carotene were measured in 742 children, including those with xerophthalmia and every twentieth of the remaining children. Anthropometric measurements were made on 2909 of the children. Bitot's spots were seen in 1.0% of all children, with a higher prevalence in the pastoral (1.6%) and cropping (1.1%) agro-ecological zones than in the zones characterized by cash crops (0.4%) and 'ensete' (false banana, Ensete ventricosum) (0.0%). One case of corneal xerosis and 2 cases of corneal scar were also seen. Serum retinol levels were in the 'deficient' range (less than 0.35 mumol l-1) in 16% and 'low' (0.35-0.69 mumol l-1) in 44% of children. Serum retinol and clinical signs did not show any correlation with occupation and education of head of household, household size or anthropometric measurements. More stunting than wasting was observed, with peak prevalence of these signs of malnutrition being observed in the second year of life.

Increased removal of remnants of triglyceride-rich lipoproteins on a diet rich in polyunsaturated fatty acids.

We studied the effect of two diets, one rich in polyunsaturated and the other in saturated fatty acids, on the postprandial processing of exogenous and endogenous triglyceride-rich lipoproteins (chylomicrons, very-low-density lipoproteins, and their remnants). For this purpose, 12 normolipidaemic young volunteers were fed, in a cross-over design of 9 days on each diet, either a diet rich in saturated fat (21% of their daily energy intake from saturated fat, 12% from monounsaturated fat, and 3% from polyunsaturated fat) or a diet rich in polyunsaturated fat (10% saturated fat, 9% monounsaturated fat, and 18% polyunsaturated fat) (P/S ratios 0.14 and 1.8, respectively). On the last day of each dietary period blood samples were drawn six times over a 24-h period for determination, by densitometric scanning of SDS gels, of the diurnal pattern of apoprotein B-48 and B-100 in the d less than 1.019 g ml-1 fractions, as estimates for the processing of chylomicrons and very-low-density lipoproteins. In addition to the usual decrease in the fasting and diurnal concentrations of total serum cholesterol and of cholesterol in the low-density lipoprotein fractions (between 15 and 21%), the diet rich in polyunsaturated fat resulted in 43% lower daily concentrations of chylomicrons and their remnants. This was due to differences in the clearance rate of chylomicrons and their remnants, rather than to differences in the absorption rate of exogenous fat. In addition, the concentrations of very low density lipoproteins and their remnants during the day were 20% lower on the diet rich in polyunsaturated fat.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative distribution, pharmacokinetics and placental permeabilities of all-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxo-retinoic acid, retinyl acetate and 9-cis-retinal in hamsters.

Pregnant hamsters were given a single oral dose (35 mumol/kg) of all-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxo-retinoic acid, 9-cis-retinal or all-trans-retinyl acetate during the early primitive streak stage of development. The radioactivity associated with the acidic retinoids was distributed to all tissues sampled (including placenta and fetus), with the largest accumulation in the liver and the least accumulation in fat. Radioactivity from 9-cis-retinal or retinyl acetate concentrated in the liver and lung. The all-trans-retinoic acid was oxidized in vivo to all-trans-4-oxo-retinoic acid and isomerized to 13-cis-retinoic acid: 13-cis-retinoic acid was oxidized to 13-cis-4-oxo-retinoic acid and isomerized to all-trans-retinoic acid. No parent 9-cis-retinal or retinyl acetate could be detected in maternal plasma. Plasma concentrations of the parent acidic retinoids reached their maxima within 60 min and then followed exponential decay. Of all the retinoids examined here, 13-cis-retinoic acid showed the largest area under the plasma curve, the slowest clearance and the longest elimination t1/2. Total plasma radioactivity, consisting of unidentified metabolites, remained elevated at 4 days after dosing. Maternal peak circulating concentrations of the parent retinoids, total radioactivity, plasma pharmacokinetic parameters or the total concentrations of residual radioactivity in fetal tissues could not be correlated with the differential teratogenic potencies of these retinoids.

Occurrence of a binding protein for 11-cis-retinal in retina.

A binding protein for retinal has been found in the soluble protein fraction of bovine retina. It was separable from the intracellular retinol- and retinoic acid-binding proteins by gel filtration on Sephadex G-100 and appeared to have a molecular weight of about 50,000. The new binding protein did not bind retinol or retinoic acid. The binding protein neither oxidized retinal in the presence of reduced pyridine nucleotides and is presumed, therefore, not to be a dehydrogenase. Bound retinal was reduced to retinol in the presence of liver alcohol dehydrogenase and NADH, indicating that the functional group remained accessible when in the protein complex. The binding protein bound cis isomers of retinal preferentially. Bound ligand was displaced most effectively by 11-cis-retinal. When individual cis-trans isomers of retinal were presented to the binding protein, binding was maximal with the 11-cis isomer. It is proposed that the protein be referred to as 11-cis-retinal-binding protein.