In vitro micellarization and intestinal cell uptake of cis isomers of lycopene exceed those of all-trans lycopene

The ratio of cis and all-trans lycopene (LYC) in human and animal tissues exceeds that in foods. The basis for this difference remains unknown, although differences in their stability, transport, and metabolism have been suggested. Here, we systematically compared the digestive stability, efficiency of micellarization, and uptake and intracellular stability of cis and all-trans isomers of LYC and carotenes using the coupled in vitro digestion and Caco-2 human intestinal cell model. Aril and oil from the carotenoid-rich gac fruit (Momordica cochinchinensis Spreng) were cooked with rice to provide a natural source of LYC and carotenes. The ratio of cis:trans isomers of LYC and beta-carotene was similar before and after simulated gastric and small intestinal digestion with recovery of total carotenoids in the digesta exceeding 70%. Micellarization of cis isomers of LYC during digestion of meals with both gac aril and oil was significantly greater than that of the all-trans isomer but less than for the carotenes. Uptake of cis isomers of LYC by Caco-2 cells was similar to that of carotenes and significantly greater than all-trans LYC. Micellarized carotenoids were relatively stable in micelles incubated in the cell culture environment and after accumulation in Caco-2 cells. These data suggest that the greater bioaccessibility of cis compared with all-trans isomers of LYC contributes to the enrichment of the cis isomers in tissues and that gac fruit is an excellent source of bioaccessible LYC and provitamin A carotenoids.     

The relative vitamin A value of 9-cis beta-carotene is less and that of 13-cis beta-carotene may be greater than the accepted 50% that of all-trans beta-carotene in gerbils

The effectiveness of beta-carotene (betaC) as a vitamin A (VA) precursor may be influenced by the proportions of cis isomers of betaC consumed in the diet. Although the metabolic fates of cis isomers of betaC are poorly understood, their retinol equivalency has been assigned a value 50% that of all-trans (at) betaC. A dose-response design was used to estimate the relative VA value (VAV) of atbetaC, 9-cis (9c) betaC and 13-cis (13c) betaC in gerbils using total liver retinol as a measure of VAV. Ten groups of gerbils received a daily dose of oil with or without betaC isomer by gavage for 7 d. Nine groups (n = 5) were divided equally among the three betaC dosing treatments with each isomer provided at 141, 275 and 418 nmol/d. Total liver VA (171-259 nmol) in gerbils administered atbetaC was higher than total liver betaC (25-53 nmol). Stores of VA and betaC in livers from gerbils administered atbetaC were higher than stores of VA and betaC in livers from those given 9cbetaC or 13cbetaC. The relative VAV of cis betaC isomers was estimated by comparing slopes of dose-response lines of all three betaC isomers using atbetaC as a reference. Total liver VA and betaC increased linearly (P < 0.05) with increasing betaC intake in gerbils gavaged with all three betaC isomer oils. The relative VAV of 9cbetaC was less (38%) and 13cbetaC was more (62%) than the assigned value of 50% that of atbetaC. Thus, the proportions of cis isomers of betaC contained in a food could negatively affect the vitamin A value of the diet.     

In vitro screening of relative bioaccessibility of carotenoids from foods

Carotenoids are lipophilic pigments in plant foods that are of particular interest as precursors of vitamin A, a nutrient required for vision, cell differentiation, and the immune system. In order to mediate such activities, carotenoids and their metabolites must be absorbed for delivery to tissues. Unlike many other dietary lipids, the efficiency of carotenoid absorption is typically inefficient, being affected by food matrix, style of processing, other dietary components, and nutritional and physiological status. Thus, reliable prediction of carotenoid bioavailability is problematic. We have developed a relatively simple and cost effective procedure to study the potential bioavailability, i.e., the bioaccessibility, of carotenoids. The method involves simulated oral, gastric and small intestinal digestion of test samples to access the efficiency of incorporation into micelles, an obligatory step for absorption of lipophilic compounds. The model can be further expanded by adding micelles generated during small intestinal phase of digestion to monolayers of Caco-2 human intestinal epithelial cells to investigate apical uptake, cellular metabolism and transepithelial transport of carotenoids. Recent work by Borel and associates has demonstrated that the relative bioaccessibility of carotenoids observed in vitro is highly correlated with in vivo observations and results from bioavailability trials with human subjects. Results from recent studies using the in vitro model to screen relative bioaccessibility of beta-carotene in various cultivars of cassava, impact of amount and types of fatty acyl groups in triglycerides on micellarization of carotenoids, and the mechanism of digestion and intestinal cell uptake of xanthophyll esters are presented.     

All-trans beta-carotene appears to be more bioavailable than 9-cis or 13-cis beta-carotene in gerbils given single oral doses of each isomer

Male gerbils (28 d old) were used to investigate the beta-carotene (betaC) isomer pattern in the intestine and tissues 6 h after ingestion of three betaC isomers. After a 49- to 52-d period of consuming the AIN93G diet without vitamin A (VA) or betaC, three groups (n = 7) were gavaged with crystalline all-trans (at)betaC, 9-cis (9c)betaC or 13-cis (13c)betaC solubilized in oil and a control group (n = 5) with oil alone. Total betaC per dose for gerbils in the atbetaC, 9cbetaC and 13cbetaC groups was 384 +/- 3, 391 +/- 2 and 386 +/- 2 nmol, respectively. After 6 h, gerbils were killed and serum, stomach contents, small intestinal contents (SIC), small intestinal mucosal scrapings (SIM) and liver were collected. betaC and VA in tissues were quantified using HPLC. Nonspecific isomerization of betaC occurred in the digestive tracts of gerbils administered betaC; the greatest effect was in the SIC of the 13cbetaC (50:50 cis:trans) and 9cbetaC (70:30 cis:trans) groups. Concentrations of total betaC in the SIM of gerbils administered at betaC were greater than those intubated with 9cbetaC and 13cbetaC (P < 0.05). Gerbils that received atbetaC had greater total betaC concentrations in serum (P < 0.05) and total betaC stores in liver (P < 0.01) compared with those administered 9cbetaC and 13cbetaC. Gerbils intubated with 9cbetaC had higher levels of total betaC in serum (P = 0.05) and liver (P < 0.01) compared with those intubated with 13cbetaC. Because of its preferential uptake, transport and tissue accumulation, atbetaC appears to be a more bioavailable isomer than 9cbetaC or 13cbetaC in gerbils.     

Micellarization and intestinal cell uptake of beta-carotene and lutein from drumstick (Moringa oleifera) leaves

The leaves and pods of the drumstick tree are used as food and medicine in some Asian and African countries. Although relatively high concentrations of beta-carotene and lutein have been reported in the leaves, the bioavailability of these carotenoids from this source is unknown. We have analyzed the digestive stability and bioaccessibility of carotenoids in fresh and lyophilized drumstick leaves using the coupled in vitro digestion/Caco-2 cell model. Beta-carotene and lutein were stable during simulated gastric and small intestinal digestion. The efficiency of micellarization of lutein during the small intestinal phase of digestion exceeded that of beta-carotene. Addition of peanut oil (5% vol/wt) to the test food increased micellarization of both carotenoids, and particularly beta-carotene. Caco-2 cells accumulated beta-carotene and lutein from micelles generated during digestion of drumstick leaves in a time- and concentration-dependent manner. The relatively high bioaccessibility of beta-carotene and lutein from drumstick leaves ingested with oil supports the potential use of this plant food for improving vitamin A nutrition and perhaps delaying the onset of some degenerative diseases such as cataracts.     

Divalent minerals decrease micellarization and uptake of carotenoids and digestion products into Caco-2 cells

Carotenoids are lipophilic, dietary antioxidants with the potential to prevent chronic and age-related diseases. Prior to their availability for physiological functions, carotenoids require micellarization and intestinal uptake, both constituting marginally understood processes. Based on an in vitro digestion model coupled to Caco-2 cells, we assessed the effect of dietary abundant divalent ions on spinach-derived carotenoid micellarization and cellular uptake: Ca and Mg ranging from 7.5 to 25 mmol/L in the digesta and Zn and Fe ranging from 3.8 to 12.5 mmol/L. Both micellarization and uptake were significantly inhibited by minerals in a concentration-dependent manner, with stronger effects for Fe and Zn compared to Ca and Mg. Compared to controls (no mineral addition), fractional micellarization and uptake were decreased to the greatest extent (to 22.5 and 5.0%, respectively; P < 0.001) by 12.5 mmol/L Fe. Effects of Mg were of the least magnitude; at 25 mmol/L, only uptake was decreased significantly to 69.2% of the control value (P < 0.001). Total cellular carotenoid uptake from test meals decreased similarly compared to micellarization; however, decreased β-carotene micellarization was counterbalanced by improved fractional cellular uptakes from the micelles for all ions. Compared to controls, fractional β-carotene uptake from the micelles was greater in samples digested in the presence of Fe, Ca, and Zn, by up to 5-10 times at the highest concentrations of each ion (P < 0.001). Like for the above carotenoids, a high cellular uptake of the epoxycarotenoid conversion products neochrome (from neoxanthin) and luteoxanthin+auroxanthin (from violaxanthin) was also observed. The present results indicate that divalent ions may inhibit carotenoid micellarization and uptake.     

Amount of dietary fat and type of soluble fiber independently modulate postabsorptive conversion of beta-carotene to vitamin A in mongolian gerbils

Current dietary guidelines recommend a decrease in fat intake and an increase in fiber consumption. Decreased bioavailability (BV) of carotenoids is thought to be associated with both of these recommendations. A 2 x 4 factorial design was used to test the effects of dietary fat level at 10 or 30% of total energy and fiber type using no fiber, silica, citrus pectin or oat gum (7 g/100 g) on beta-carotene (betaC) BV in 4- to 5-wk-old Mongolian gerbils. We assessed BV as both accumulation of betaC and bioconversion of betaC to vitamin A (VA) in tissues. A VA- and betaC-deficient diet was fed for 1 wk followed by one of eight isocaloric, semipurified diets supplemented with carrot powder [ approximately 1 microgram betaC, 0.5 microgram alpha-carotene (alphaC)/kJ diet] for 2 wk (n = 12/group). Increasing dietary fat resulted in higher VA (P: = 0.074) and lower betaC (P: = 0.0001) stores in the liver, suggesting that consumption of high fat diets enhances conversion of betaC to VA. The effect of soluble fiber on hepatic VA storage was dependent on fiber type. Consumption of citrus pectin resulted in lower hepatic VA stores and higher hepatic betaC stores compared with all other groups, suggesting less conversion of betaC to VA. In contrast, consumption of oat gum resulted in hepatic VA and betaC stores that were higher (P = 0.012) and lower (P = 0.022), respectively, than those of citrus pectin-fed gerbils. The level of dietary fat consumed with soluble fiber had no interactive effects on hepatic VA, betaC or alphaC stores. Results demonstrate that betaC BV is independently affected by dietary fat level and type of soluble fiber, and suggest that these dietary components modulate postabsorptive conversion of betaC to VA. This study confirms the negative effects of citrus pectin on betaC BV, and suggests that oat gum does not adversely affect betaC BV.     

The effect of plant sterol-enriched turkey meat on cholesterol bio-accessibility during in vitro digestion and Caco-2 cell uptake

This study evaluated the effect of a plant sterol-enriched turkey product on cholesterol bio-accessibility during in vitro digestion and cholesterol uptake by Caco-2 monolayers. Turkey products, one plant sterol-enriched (PS) and one plant sterol-free (C), were produced in an industrial pilot plant. Before simulated digestion, matrices were spiked with cholesterol (1:5 weight ratio of cholesterol to plant sterol). Plant sterols were included at a concentration equivalent to the minimum daily intake recommended by the European Food Safety Authority (EFSA) for cholesterol lowering. After simulated digestion, the percentage of cholesterol micellarization and uptake by Caco-2 cells in the presence of PS meat were measured. Compared to C meat, PS meat significantly inhibited cholesterol micellarization on average by 24% and Caco-2 cell accumulation by 10%. This study suggests that plant sterols in meat can reduce cholesterol uptake by intestinal epithelia and it encourages efforts to make new PS-based functional foods.     

Hydrolysis of zeaxanthin esters by carboxyl ester lipase during digestion facilitates micellarization and uptake of the xanthophyll by Caco-2 human intestinal cells

Zeaxanthin (Zea) and lutein are the only dietary carotenoids that accumulate in the macular region of the retina and lens. It was proposed that these carotenoids protect these tissues against photooxidative damage. Few plant foods are enriched in Zea, and information about the bioavailability of Zea from these foods and its accumulation in ocular tissues is limited. The amounts of free Zea and its mono- and diesters were measured for several plant foods that have relatively high concentrations of this xanthophyll. Wolfberry had the greatest concentration of Zea with a diester that accounts for 95% of the total. Free, mono-, and diesters of Zea were present in orange and red peppers, whereas only Zea monoesters were detected in squash. Zea esters were partially hydrolyzed by carboxyl ester lipase (CEL) during simulated digestion. The efficiency of micellarization was dependent on speciation with combined means of free Zea, Zea monoesters, Zea diesters from the digested foods of 81 +/- 8, 44 +/- 5, and 11 +/- 4%, respectively. When exposed to micelles generated during digestion of the test foods, Zea uptake by Caco-2 cells was proportional to the medium content (11-14%). Free Zea was the most abundant form in Caco-2 cells, although Zea monoesters also were detected (<8 +/- 0.7% vs. free Zea). CEL enhanced Zea uptake from micelles (12.3-fold; P < 0.05) by hydrolyzing Zea esters. After cell uptake, concentrations of free and monoesterified Zea remained relatively stable. These data suggest that dietary Zea esters are hydrolyzed by CEL during the small intestinal phase of digestion and that this conversion enhances Zea bioavailability.     

Comparative effects of all-trans beta-carotene vs. 9-cis beta-carotene on carcinogen-induced neoplastic transformation and connexin 43 expression in murine 10T1/2 cells and on the differentiation of human keratinocytes

9-cis beta-Carotene was extracted from a commercial extract of the algae Dunaliella salina (Betatene), and its actions on proliferation and gene expression were examined in murine 10T1/2 cells and human HaCaT keratinocytes. The 9-cis isomer was less active than all-trans beta-carotene in reducing proliferation and in upregulating expression of connexin 43 in 10T1/2 cells. However, it had comparable ability to suppress carcinogen-induced neoplastic transformation. When tested in HaCaT cells in organotypic culture, it was less active in inducing connexin 43 expression and suppressing expression of keratin K1. In this assay the all-trans isomer was highly active at 10(-6) M, whereas 10(-5) M 9-cis beta-carotene was required to produce a comparable effect. Only small reductions in expression of the basal keratin 5 were seen. All-trans and 9-cis retinoic acids, potential metabolites of beta-carotene isomers, were studied in the same systems. In contrast to the carotenoids, the 9-cis isomer of retinoic acid was approximately 10-fold more active in suppressing neoplastic transformation and inducing connexin 43 expression in both cell types than the all-trans isomer. The retinoic acid isomers were about equipotent in suppressing K1 expression. Cellular levels of 9-cis beta-carotene were approximately 3.5-fold lower than levels of all-trans beta-carotene, suggesting that part, but not all, of this decreased activity of the 9-cis isomer was due to decreased cell uptake. Thus 9-cis beta-carotene is consistently less active than the all-trans isomer; that 9-cis retinoic acid is, in general, much more potent than the all-trans isomer suggests little or no conversion from the carotenoid to the retinoid under these culture conditions.     

Bioavailability of beta-carotene (betaC) from purple carrots is the same as typical orange carrots while high-betaC carrots increase betaC stores in Mongolian gerbils (Meriones unguiculatus)

Vitamin A (VA) deficiency is a worldwide public health problem. Biofortifying existing sources of beta-carotene (betaC) and increasing dietary betaC could help combat the issue. Two studies were performed to investigate the relative betaC bioavailability of a betaC supplement to purple, high-betaC orange, and typical orange carrots using Mongolian gerbils (Meriones unguiculatus). In study 1, which used a traditional bioavailability design, gerbils (n 32) received a diet containing orange, purple, or white carrot powder, or white carrot powder +a betaC supplement. In study 2, which included betaC-biofortified carrots, gerbils (n 39) received orange, high-betaC orange, purple, or white carrot powder in their diet. Both studies lasted 21 d and the gerbils were killed to determine the effect of carrot type or supplement on serum and liver betaC, alpha-carotene, and VA concentrations. Liver stores of betaC or VA in the gerbils did not differ between orange and purple carrot diets when equal amounts of betaC from each of the diets were consumed (P>0.05). Both the orange and purple carrot diet resulted in higher liver VA compared with the supplement (P<0.05). High-betaC carrots resulted in more than 2-fold higher betaC and 1.1 times greater VA liver stores compared with typical orange carrots (P<0.05). These results suggest that high-betaC carrots may be an alternative source of VA to typical carrots in areas of VA deficiency. Second, phenolics including anthocyanins and phenolic acids in purple carrot do not interfere with the bioavailability of betaC from purple carrots.     

Uptake of lycopene and its geometrical isomers is greater from heat-processed than from unprocessed tomato juice in humans.

Lycopene and beta-carotene are the most abundant carotenoids in human blood and tissues. Although lacking provitamin A activity, lycopene may be biologically active by contributing to the antioxidative defense system of the organism. We studied the uptake of lycopene from processed (boiled with 1% corn oil for 1 h) and unprocessed tomato juice in humans. Lycopene concentrations in human serum increased only when processed tomato juice was consumed. Lycopene uptake varied with individuals, but peak serum concentrations were always reached between 24 and 48 h. The carotenoid was eliminated from serum with a half-life of 2-3 d. The increase in peak serum concentrations was dose-dependent but not linear with the dose. Repeated doses led to a continual rise of lycopene in human serum. Of the different geometrical isomers (all-trans, 9-cis and 13-cis), the cis isomers seemed to be somewhat better absorbed than the all-trans form.     

Cellular transport of lutein is greater from uncooked rather than cooked spinach irrespective of whether it is fresh,frozen, or canned

Lutein, a carotenoid found in significant levels in spinach, has attracted a great deal of attention owing to its reported function as a shield against the photooxidative effects of blue light. Therefore, the rationale of this study was to examine the effects of various processing and cooking methods on lutein bioavailability from spinach (Spinacia oleracea) using an in vitro digestion procedure coupled with the use of a human intestinal Caco-2 cell model. Fresh, frozen, and canned spinach were analyzed uncooked and after boiling or microwave cooking. Lutein content from the uncooked and cooked digested food (digestate) and appropriate micelles was determined. Micellarized lutein from the spinach samples was adjusted to 0.1 μmol/L and added to Caco-2 cells. Cellular uptake and secretion (cellular transport) of lutein were determined. Our results showed that digestate obtained from uncooked canned spinach had greater lutein content (P < .05) than uncooked fresh or frozen spinach. Microwave cooking, but not boiling, significantly lowered the lutein content of canned spinach digestate and micelles compared with their uncooked counterparts. Interestingly, there were no differences in the micellarization of lutein between the cooking and processing methods. Cellular transport of lutein was greater from uncooked spinach micelles compared with boiled or microwave-cooked spinach. To conclude, although the lutein content of digesta and micelles may have been modified, its micellarization was not significantly affected by any of the cooking or processing methods tested. In general, cellular transport of lutein was greatest in uncooked spinach irrespective of whether the spinach was fresh, frozen, or canned.     

Beta-cryptoxanthin from citrus juices: assessment of bioaccessibility using an in vitro digestion/Caco-2 cell culture model

Beta-Cryptoxanthin (beta-CX), a provitaminic carotenoid of potential interest for health, is found principally in Citrus fruit in both free and esterified forms. Little is known about the intestinal absorption of beta-CX especially with regard to the esterified forms. The aim of this study was to evaluate the absorption of free and esterified beta-CX using simulated digestion coupled with the Caco-2 model. Bioaccessibility was investigated by measuring the transfer of carotenoids from different citrus juices into micelles using an in vitro digestion system. Then, carotenoid uptake was evaluated by adding carotenoid-rich micelles (from the in vitro digestion) or synthetic micelles (made from synthetic lipids and carotenoids purified from citrus juice) to human intestinal cells (Caco-2 TC7 clone). Our results showed that beta-cryptoxanthin esters (beta-CXE) were partially hydrolysed during the in vitro digestion. The bioaccessibility of free beta-CX measured was significantly higher (40 (SD 1.05) %) than that of beta-carotene (30 (SD 1.9) %) and beta-CXE (16 (SD 1.5) %). In the same way, the incorporation of free beta-CX (27 (SD 1.01) %) into synthetic micelles exceeded (P<0.05) that of beta-carotene (10 (SD 0.7) %) and beta-CXE (8.8 (SD 0.4) %). In the case of micelles from in vitro digestion, the uptake of beta-carotene, free beta-CX and beta-CXE forms by Caco-2 cells was 14.3 (SD 1.8), 3.9 (SD 1.3), and 0.7 (SD 0.08) % respectively. These results showed a preferential uptake by Caco-2 cells of beta-carotene and free beta-CX compared with the two esters of beta-CX.     

Enrichment of tomato paste with 6% tomato peel increases lycopene and beta-carotene bioavailability in men

A high intake of tomato products is associated with a lower incidence of upper aerodigestive tract and prostate cancers. This beneficial effect might be explained by a higher intake of carotenoids such as lycopene and/or beta-carotene. Because tomato peels, usually eliminated during tomato processing, are a valuable source of these carotenoids, we designed a study to examine whether a tomato paste enriched in tomato peels (ETP, 6% peel) increases the absorption of these carotenoids compared to a classically made tomato paste (CTP). Carotenoid bioaccessibility was evaluated using an in vitro digestion model by measuring the amount of carotenoids transferred from the pastes to micelles. Carotenoid absorption by human intestinal cells (Caco-2) was evaluated after the addition of carotenoid-rich micelles (obtained from the in vitro digestion of the 2 pastes). Carotenoid bioavailability in humans was assessed by measuring chylomicron carotenoid responses in a postprandial experiment in which 8 healthy men consumed 2 meals containing either the ETP or the CTP. ETP contained 47.6 mg lycopene (58% more than CTP) and 1.75 mg beta-carotene (99% more than CTP) per 100 g of paste. In micelles, 30% more lycopene and 81% more beta-carotene were recovered after ETP than after CTP in vitro digestion. The amount of carotenoids absorbed by Caco-2 cells was 75% greater (P < or = 0.05) for lycopene and 41% greater (P < or = 0.05) for beta-carotene after the addition of micelles from ETP than from CTP. After ETP intake the chylomicron beta-carotene response was 74% greater than after CTP intake, and the lycopene response tended to be greater (34.1%, P = 0.093). Peel enrichment of tomato paste with tomato peel is an interesting option for increasing lycopene and beta-carotene intakes.     

Plasma carotenoids of monkeys (Macaca fascicularis and Saimiri sciureus) fed a nonpurified diet

The major carotenoid pigments in the plasma and in a common, nonpurified diet of two species of monkeys (Macaca fascicularis and Saimiri sciureus) were measured. The xanthophylls, lutein, zeaxanthin, alpha-cryptoxanthin, and beta-cryptoxanthin, were the principal carotenoids in both the diet and the plasma. Lutein and zeaxanthin were abundant in the all-trans, the 9-cis, and the 13-cis geometrical isomers in the diet, but the 9-cis form was rarely measurable in plasma. However, the 13-cis isomers of lutein and zeaxanthin were found in higher proportions in plasma than in the diet. For both the monohydroxy-xanthophylls, alpha-cryptoxanthin and beta-cryptoxanthin, and the dihydroxy-xanthophylls, lutein and zeaxanthin, the beta, beta structural isomer (beta-cryptoxanthin or zeaxanthin) is less abundant than the beta, epsilon isomer in plasma than in the diet. These results indicate substantial specificity in the absorption or retention of closely related carotenoid isomers in primates. The proportions of different geometrical isomers of lutein and zeaxanthin in the plasma of both species of monkeys were nearly identical and were similar to human values. The hydrocarbon carotenoids, alpha-carotene, beta-carotene and lycopene were usually undetectable in monkey plasma. The monkeys appear to be like humans in their utilization of lutein and zeaxanthin but distinctly different in some other aspects of carotenoid utilization.     

Serum response of all-trans and 9-cis isomers of beta-carotene in humans.

Little work has been performed on the serum response of various carotene isomers. The present study was carried out to examine the serum response of all-trans and 9-cis isomers of beta-carotene (BC) using frequent blood sample collections at early time points.

Serum responses of all-trans BC and a mixture of BC isomers containing 80% 9-cis BC were studied in 15 men by measuring the serum concentrations of BC at 1, 3, 5, 7, 9, 12, and 24 hours after a single large oral dose of all-trans BC or 9-cis BC.

The serum response to an oral dose of all-trans BC (120 mg) significantly increased from baseline at 24 hr (p < 0.004). After an oral dose of a mixture of BC isomers (120 mg, 80% 9-cis BC), the peak concentration of 9-cis BC was significantly greater that baseline values (p < 0.016).

Increases in serum all-trans BC levels, in part, may be due to greater intestinal absorption, whereas the inability to measure a significant increase in the concentration of 9-cis BC may indicate poor absorption, isomerization to all-trans BC, or a very rapid tissue uptake.     

Novel lycopene metabolites are detectable in plasma of preruminant calves after lycopene supplementation

Appropriate animal models such as preruminant calves are necessary to study the complex physiological functions of carotenoids and to relate them to possible health effects in humans. In this study, the bioavailability and metabolism of lycopene from 2 dietary supplements were compared. LycoVit containing synthetic lycopene and Lyc-O-Mato containing natural tomato oleoresin were administered to 2 groups of preruminant calves (each n = 8) for 14 d in daily doses of 15 mg of lycopene. Plasma was analyzed for carotenoids before the intervention period, directly after, and each day for 5 d after the end of the intervention. All-trans and 5-cis lycopene, and 3 lycopene metabolites not previously found in calf plasma were detected. These metabolites contributed 52% of the total lycopene content measured at the end of the intervention period. Based on spectroscopic data, they might be hydrogenation products, which are formed from all-trans and/or 5-cis lycopene. In the LycoVit group, total lycopene concentrations were approximately 300% higher (286 +/- 89 nmol/L) than in the Lyc-O-Mato group (72 +/- 33 nmol/L) (P < 0.001). This indicates that, unlike in humans, lycopene from LycoVit and Lyc-O-Mato does not have equal bioavailabilities in preruminant calves. Therefore, the preruminant calf may not be a suitable animal model with which to study the biological and physiological effects of lycopene.     

Assessment of lutein bioavailability from meals and a supplement using simulated digestion and caco-2 human intestinal cells

Lutein and zeaxanthin are selectively accumulated in the lens and macular region of the retina. It was suggested that these xanthophylls protect ocular tissues from free-radical damage that can cause cataracts and age-related macular degeneration. Insights regarding the absorption of dietary xanthophylls for delivery to ocular tissues are limited. Our primary objective was to examine factors affecting the transfer of lutein from foods to absorptive intestinal epithelial cells during digestion. Lutein and other carotenoids present in spinach purée and lutein from a commercial supplement were relatively stable during in vitro digestion. Micellarization of lutein and zeaxanthin during the small intestinal phase of digestion exceeded that of beta-carotene and was greater for xanthophylls in oil-based supplements than in spinach. Apical uptake of lutein from micelles by Caco-2 human intestinal cells was linear for at least 8 h, and accumulation from synthetic micelles exceeded that from micelles generated during simulated digestion. Stimulation of chylomicron synthesis resulted in the secretion of 7.6 +/- 0.1% of cellular lutein into the triglyceride-rich fraction in the basolateral chamber. These data support the use of simulated digestion and the Caco-2 cell model as effective tools for identifying factors affecting absorption of dietary carotenoids.