Fate of Amadori compounds in processing and digestion of multi-ingredients tomato based sauces and their effect on other microconstituents.

Amadori compounds (ACs), the first stable products of Maillard reaction, are detected in various products of fruits and vegetables, and show an antioxidant activity which can be related to beneficial effects in human health. In order to optimize the nutritional quality of a multi-ingredient tomato sauce (tomato puree - onion - olive oil - dried pepper), the fate of ACs during processing (drying, heating) and gastrointestinal digestion of a model meal was assessed as well as that of other microconstituents, i.e. carotenoids, phenolic compounds and capsaicinoids. The drying at 50 °C of fresh pepper induced the formation and accumulation of ACs after 6 days. During the heat treatment by microwave of multi-ingredient tomato sauce, Maillard reaction occurs in presence of dried pepper and the content in ACs in the tomato-based sauces increased (+33% to + 53%) depending of quantities of dried pepper added. The bioaccessibility of total ACs was 24-31% in duodenal phase and 18-22% in jejunal phase. Individual ACs have shown variable bioaccessibility, e.g. very high for Fru-Arg (50.8% to 71.3%), and very low for Fru-Met (1.8% to 2.2%). The kinetic monitoring of ACs in digestion medium showed that ACs are not stable (-46% in gastric phase, -49 % in intestinal phase) which indicated their potential degradation in the digestive tract. The presence of ACs in the multi-ingredients tomato sauces had no effect on the content of the other bioactive compounds monitored in the study and even promoted the bioaccessibility of total lycopene (+30%) but decreased the bioaccessibility of total phenolic compounds.

Food Structure Modulates the Bioavailability of Triglycerides and Vitamin D, and Partly That of Lutein: A Randomized Trial with a Crossover Design in Adults.

SCOPE: The specific effect of the food matrix structure on fat-soluble micronutrient bioavailability is only partly understood. Evaluating fat-soluble micronutrient bioavailability after consumption of foods displaying similar composition but different structure is aimed at. METHODS AND RESULTS: Twelve healthy subjects are enrolled in a randomized, open label, crossover postprandial trial. Four different model foods are tested: custard, pudding, sponge cake, and biscuit. Vitamin D3 , lutein, and triglyceride chylomicron responses, evaluated as postprandial areas under the curve, are then assayed. Custard triglyceride response is higher than pudding and biscuit responses (up to +122.7%, p < 0.0001). Sponge cake vitamin D3 response is higher than biscuit response (+26.6%, p = 0.047). No difference between the model foods are observed regarding lutein responses. Triglyceride responses peak at 3 h for all conditions, while vitamin D3 and lutein peaks are delayed by 1 h with the biscuit matrix compared to other model foods. CONCLUSION: Food structure can significantly impact on triglyceride and vitamin D3 bioavailability in terms of absorbed amounts and/or maximum absorption time. The data highlight positive correlations between triglyceride, vitamin D, and lutein nutrient responses. These results are of particular interest to develop functional foods for population subgroups such as the elderly.

Impact of onions in tomato-based sauces on isomerization and bioaccessibility of colorless carotenes: phytoene and phytofluene.

Onions as an interesting ingredient have been proved to promote Z-isomerization of lycopene and increase bioaccessibility of total-lycopene. Phytoene (PT) and phytofluene (PTF), the precursors of lycopene, are colorless carotenes, which are attracting much attention and are also abundant in tomatoes. Therefore, onions might also affect the distribution and bioaccessibility of PT and PTF isomers during heating tomato (hot-break and cold-break purees)-onion-extra virgin olive oil (EVOO) sauces. The addition of onions (or diallyl disulfide present in onions) into tomato purees did not cause degradation of PT or PTF; however it favored E/Z-isomerization of PT and PTF by reducing the proportions of their natural Z-isomers (Z-15-PT and Z2,3-PTF) and decreased the bioaccessibility of total-PT and total-PTF. Simultaneously, a complex picture was obtained for the effect of onions on the bioaccessibility of individual PT and PTF isomers, depending on the precise isomer. Bioaccessibility of PT and PTF isomers in tomato-based sauces decreased in the order: 15-Z-PT > all-E-PT; Z2,3-PTF > all-E-PTF > Z4 or Z5-PTF; total-PT > total-PTF. E-isomerization of PT and PTF enhanced by onions during heating tomato-onion purees decreased their bioaccessibility.

The Effect of an Iron Supplement on Lycopene Metabolism and Absorption During Digestion in Healthy Humans.

SCOPE: To investigate the formation and absorption of lycopene (LYC) metabolites in the human upper gastrointestinal lumen, in the absence and presence of iron. METHODS: Healthy males (n = 7) consumed test meals that deliver ≈22 mg LYC + ≈0.3 mg apo-lycopenals from oleoresin without (-FeSO4 ) and with ferrous sulfate (160 mg, +FeSO4 ). Subjects were intubated with a naso-gastric/naso-duodenal tube. Digesta, blood plasma, and the triglyceride-rich lipoprotein (TRL) fractions of plasma were analyzed using LC-MS/MS, to measure LYC and apo-lycopenoids. RESULTS: Digesta LYC concentrations increased with time (p = 1.2 × 10-7 ), decrease with time × iron (p = 1.1 × 10-5 ), and remain ≈200× higher than apo-lycopenals/lycopenone. Digesta apo-8'-, -10'-, -12'-, -14'-, -15-lycopenal, and apo-13-lycopenone concentrations increased with time (p < 0.01), apo-12'-, -14'-, -15-lycopenal, apo-13-lycopenone increase with iron (p < 0.05), and time × iron decrease apo-8'-, -10'-, -12'-, -14'-, -15-lycopenal, apo-13-lycopenone concentrations (p < 0.01). A 1.9-fold decrease in LYC TRL area-under-the-time-concentration-curve is observed after the test meal +FeSO4 versus the test meal -FeSO4 (p = 0.02). Apo-lycopenals were detected in later TRL fractions, and no apo-lycopenols or apo-lycopenoic acids were observed in any samples. CONCLUSIONS: FeSO4 reduces LYC absorption. Apo-lycopenals appear to be absorbed from foods, and not made in significant quantities during digestion.

Heating tomato puree in the presence of lipids and onion: The impact of onion on lycopene isomerization.

Z-lycopene isomers are more bioavailable than all-E-lycopene, especially 5-Z-lycopene. Based on our observations, the addition of unblanched onion could favor Z-isomerization of lycopene (by more than 94%) during heating tomato-onion-extra virgin olive oil (EVOO) purees at 90 °C for 2 h. The increase in Z-lycopene was correlated linearly with the addition of unblanched onion, with R2 > 0.92, and increased rates of 5-Z-lycopene were 3-4 times higher than for 9-Z-lycopene and 13-Z-lycopene. Diallyl disulfide (DADS), formed by alliinase-catalyzed breakdown of non-volatile precursors in onion, contributed to these increases and correlated linearly (R2 > 0.79, 0-0.50 mg/g puree) with increased Z-lycopene. Increased rates of 5-Z-lycopene were also 3-4 times higher than for 9-Z-lycopene and 13-Z-lycopene. However, blanching of onion, in tomato-onion-EVOO purees, before heating, significantly decreased the effect of onion on Z-isomerization of lycopene.

A D-optimal mixture design of tomato-based sauce formulations: effects of onion and EVOO on lycopene isomerization and bioaccessibility.

A D-optimal mixture design was used to study the effects of onion and extra virgin olive oil (EVOO) on lycopene Z-isomerization, lycopene diffusion into oil (expressed as a partition factor between tomato-based puree and oil) and in vitro bioaccessibility of lycopene isomers after thermal treatment of tomato-based puree consisting of tomato (75-100%), onion (0-20%) and EVOO (0-5%). A decrease of tomato puree could improve lycopene Z-isomerization, lycopene diffusion and lycopene bioaccessibility. The component interactions had an important influence on the Z-isomerization of lycopene, besides the linear mixtures of components. However, only linear mixtures of components appeared to have significant effects on the diffusion and bioaccessibility of lycopene, in which EVOO had the highest positive effect followed by onion. The bioaccessibility of lycopene isomers in every tomato-based sauce formulation decreased in the order: 13-Z-lycopene > 9-Z-lycopene > 5-Z-lycopene > all-E-lycopene. The bioaccessibility of total-Z-lycopene was at least 10 times higher than that of all-E-lycopene. Proportions of total-Z-lycopene were correlated positively with the partition factor and bioaccessibility of total-lycopene, with an r over 0.730 (p = 0.0031). Therefore, increased Z-lycopene proportions probably contributed to enhanced lycopene diffusion and bioaccessibility. The positive effects of components, especially onion, on total-lycopene diffusion and bioaccessibility were probably because the components increased the Z-isomerization of lycopene during heating of tomato-based puree.

ß-Cyclodextrin Does not Alter the Bioaccessibility and the Uptake by Caco-2 Cells of Olive By-Product Phenolic Compounds.

Alperujo-a two-phase olive mill waste that is composed of olive vegetation water and solid skin, pulp, and seed fragments - is a highly valuable olive by-product due to its high content in phenolic compounds. In this study, we assessed whether ß-cyclodextrin (ß-CD), which is used to extract and protect alpejuro phenolic compounds (hydroxytyrosol-O-glucoside, tyrosol, caffeic, and p-coumaric acids) could impact on their bioaccessibility (i.e., the percentage of molecule found in the aqueous phase of the digesta) and uptake by intestinal cells, by using an in vitro digestion model and Caco-2 TC7 cells in culture, respectively. Our results showed that ß-CD did not change the bioaccessibility of the selected phenols. Hydroxytyrosol-O-glucoside and caffeic did not cross Caco-2 cell monolayers. Conversely ferulic acid, identified as the main caffeic acid intestinal metabolite, was absorbed through intestinal cell monolayers (~20%). Interestingly, ß-CD moderately but significantly improved the local absorption of tyrosol and p-coumaric acid (2.3 + 1.4% and 8.5 ± 4.2%, respectively, p < 0.05), even if their final bioavailability (expressed as bioaccessibility × absorption by Caco-2 cells) was not modified (16.2 ± 0.6% vs. 16.8 ± 0.5% for tyrosol and 32.0 ± 3.2% vs. 37.2 ± 3.2% for p-coumaric acid, from pure alperujo and alperujo complexed with ß-CD, respectively). Overall, our results show that ß-CD is an interesting extraction and storage agent for phenolic compounds that does not alter their in vitro bioavailability.

Production of asymmetric oxidative metabolites of [13C]-ß-carotene during digestion in the gastrointestinal lumen of healthy men.

Background: Asymmetric ß-apo-carotenoids (nonvitamin A-active metabolites) of provitamin A carotenoids have been observed in humans, but no study has investigated their formation during digestion. Objective: The aim of this study was to follow the formation and absorption of asymmetric ß-apo-carotenoids during digestion. Design: Healthy men were intragastrically and intraduodenally intubated, and randomly assigned to consume a lipid-rich control meal (n = 3) or a lipid-rich test meal containing 20 mg [13C-10]-ß-carotene (n = 7). Digesta samples were collected over 5 h, and blood collected over 7 h. The triglyceride-rich lipoprotein (TRL) fractions of plasma were also isolated. Lipophilic extracts of digesta, plasma, and TRL were analyzed via a high-performance liquid chromatography-tandem mass spectrometry method developed to identify [13C]-labeled ß-apo-carotenals/carotenone, [13C]-ß-apo-carotenols, and [13C]-ß-apo-carotenoic acids. Results: Relative to [13C]-ß-carotene, [13C]-ß-apo-carotenal levels remained ∼3 orders of magnitude lower throughout digestion (no [13C]-ß-apo-carotenols, or [13C]-ß-apo-carotenoic acids were observed). A mixed model determined relative influence of digesta type and time on digesta metabolite level. Increasing time significantly increased the model levels of digesta [13C]-ß-apo-10',12',14',15-carotenal and [13C]-ß-apo-13-carotenone (P < 0.05) and trended toward decreased [13C]-ß-apo-8'-carotenal (P = 0.0876). Gastric digesta were associated with a significantly higher level of [13C]-ß-apo-8'-carotenal (P = 0.0289), and lower levels of [13C]-ß-apo-12',14',15-carotenal (P < 0.05), relative to duodenal digesta. Anticipated retinoids, but no asymmetric [13C]-ß-apo-carotenals, [13C]-ß-apo-carotenols, or [13C]-ß-apo-carotenoic acids, were observed in the blood or TRL samples. Conclusions: ß-Carotene appears to be robust to digestion, with minor amounts of ß-apo-carotenals/carotenone formed. Absence of asymmetric [13C]-ß-apo-carotenals in plasma and TRL suggests lack of absorption, levels below the limit of detection, lack of stability, or further conversion during the digestive process to as-yet unidentified products. Lack of asymmetric [13C]-ß-apo-carotenals in plasma also suggests a lack of postprandial intestinal BCO2 activity in healthy humans. This trial was registered at clinicaltrials.gov as NCT03492593.

Are lutein, lycopene, and ß-carotene lost through the digestive process?

The bioavailability of many carotenoids has been assessed, but little attention has been given to the metabolism of these antioxidant compounds during digestion. The isomerization and loss of lutein, lycopene, and ß-carotene incorporated into a lipid-rich liquid meal was determined in vitro through the gastric, duodenal, and jejunal phases in the presence and absence of digestive enzymes, and in the presence and absence of known oxidizing agents often found in mixed meals (metmyoglobin in red meat and ferrous sulfate in supplemental iron). Carotenoids were quantitated using HPLC-PDA. In the absence of enzymes, lutein and lycopene were lost during earlier phases of the digestive process. In the presence of enzymes, lutein and lycopene were robust through the gastric and duodenal phases, with statistically significant losses of 40% and 20%, respectively, observed only during the jejunal phase. Regardless of the presence or absence of enzymes, an initial 25% of ß-carotene was lost during the gastric phase, but no further loss was observed. Ferrous sulfate had no significant impact on any carotenoid level. Metmyoglobin had no impact on lutein, but significantly reduced lycopene and ß-carotene levels by 30% and 80%, respectively, by the end of the jejunal phase. No significant isomerization was observed between the initial and jejunal phases for any of the carotenoids.

Form of phytosterols and food matrix in which they are incorporated modulate their incorporation into mixed micelles and impact cholesterol micellarization.

SCOPE: The ability of different plant sterols/stanols (PS) mixtures, which differed in the degree of B-ring saturation and aliphatic side chain structure and saturation, to reduce cholesterol (CH) micellarization was explored. METHODS AND RESULTS: Experiments were performed using an in vitro digestion model, synthetic mixed micelles, and pure porcine pancreatic lipases. Sterols were measured by GC-FID. The ability of PS to reduce CH micellarization was dependent on the form of PS and on the type of delivery matrix (low-fat yogurt or olive oil). Long-chain PS esters delivered in the yogurt matrix, and medium chain PS esters delivered in olive oil provided the greatest reduction in CH micellarization. In yogurt, the ability to impair CH micellarization was inversely related (rho = -0.41, p < 0.0005) to PS melting point. In olive oil, the more hydrophobic PS mixtures, i.e. those rich in long-chain PS esters, had the lower ability to impair CH micellarization. CONCLUSIONS: Different forms of PS have a different ability to impair CH micellarization. This ability depends on the transfer efficiency of PS from the food matrix to the micelle, which in turn depends on the melting point and the hydrophobicity of PS and on the delivery food matrix.

ß-lactoglobulin as a vector for ß-carotene food fortification.

Food fortification is a strategy to overcome vitamin A deficiency in developing countries. Our aim was to investigate the involvement of the bovine milk protein ß-lactoglobulin (ß-Lg), a potential retinoid carrier, in vitamin A absorption. In vivo experiments were conducted by force-feeding mice with retinol or ß-carotene associated with either ß-Lg or oil-in-water emulsion, with subsequent determination of both vitamin A intestinal mucosa and plasma contents. Caco-2 cells were then used to investigate the mechanisms of vitamin A uptake when delivered by either ß-Lg or mixed micelles. We showed that ß-Lg was as efficient as emulsion to promote ß-carotene, but not retinol, absorption in mice. Similar results were obtained in vitro. Interestingly, an inhibitor of the Scavenger Receptor Class B Type I significantly decreased the uptake of micellar ß-carotene but not that of ß-carotene bound to ß-Lg. Overall, we showed that ß-Lg would be a good vector for ß-carotene food fortification.

Fatty acids affect micellar properties and modulate vitamin D uptake and basolateral efflux in Caco-2 cells.

We have recently shown that vitamin D3 (cholecalciferol) absorption is not a simple passive diffusion but involves cholesterol transporters. As free fatty acids (FAs) modulate cholesterol intestinal absorption and metabolism, we hypothesized that FAs may also interact with vitamin D absorption. Effects of FAs were evaluated at different levels of cholecalciferol intestinal absorption. First, the physicochemical properties of micelles formed with different FAs were analyzed. The micelles were then administered to human Caco-2 cells in culture to evaluate FA effects on (i) cholecalciferol uptake and basolateral efflux and (ii) the regulation of genes coding proteins involved in lipid absorption process. Micellar electric charge was correlated with both FA chain length and degree of unsaturation. Long-chain FAs at 500 µM in mixed micelles decreased cholecalciferol uptake in Caco-2 cells. This decrease was annihilated as soon as the long-chain FAs were mixed with other FAs. Oleic acid significantly improved cholecalciferol basolateral efflux compared to other FAs. These results were partly explained by a modulation of genes coding for lipid transport proteins such as Niemann-pick C1-like 1 and scavenger receptor class B type I. The data reported here show for the first time that FAs can interact with cholecalciferol intestinal absorption at different key steps of the absorption process. Cholecalciferol intestinal absorption may thus be optimized according to oil FA composition.

Effect of type of TAG fatty acids on lutein and zeaxanthin bioavailability.

The xanthophylls lutein and zeaxanthin probably play a role in visual function and may participate in the prevention of age-related eye diseases. Although a minimum amount of TAG is required for an optimal bioavailability of these carotenoids, the effect of the type of TAG fatty acids (FA) is less clear. The aim was to assess the effect of the type of TAG FA on bioavailability of these xanthophylls. A total of three complementary models were used: an in vitro digestion model to study bioaccessibility, Caco-2 cells to study uptake efficiency and orally administered rats to study in vivo bioavailability. Results showed that lutein and zeaxanthin bioaccessibility was greater (about 20-30 %, P< 0·05) with butter and palm oil than with olive and fish oils. Mixed micelle size, which was significantly lower (about 8 %, P< 0·05) with SFA than with unsaturated FA, was inversely related to lutein and zeaxanthin bioaccessibility. There was no significant effect of the type of TAG FA on xanthophyll uptake by Caco-2 cells, but some compounds present in natural oils significantly affected xanthophyll uptake. Oral administration of rats with spinach and butter over 3 d led to a higher fasting plasma lutein concentration than oral administration with olive or fish oils. In conclusion, dietary fats rich in SFA lead to a higher bioavailability of lutein and zeaxanthin, as compared with fats rich in MUFA and PUFA. This is due partly to the higher bioaccessibility of these xanthophylls in the smaller mixed micelles produced when SFA are incorporated into mixed micelles.

Simple and fast HPLC method for simultaneous determination of retinol, tocopherols, coenzyme Q(10) and carotenoids in complex samples.

The effects of fat-soluble vitamins (such as vitamins A and E) and lipid microconstituents (such as carotenoids) on human health are now well established. However, high-performance liquid chromatography (HPLC) methods able to detect these molecules in simultaneous runs are often difficult to set up. We report here a 35-min reversed-phase HPLC method using a single C30 column kept at 35°C with a gradient system of methanol, methyl-tert-butyl ether and water at a flow-rate of 1 mL/min. This method resolves 11 carotenoids, retinol, α- and γ-tocopherol from complex matrixes such as food samples, human plasma and human adipose tissue within 35 min. The method is also able to separate coenzyme Q(10). The intra-day and inter-day coefficients of variation are suitable for routine clinical and scientific applications for the determination of lipid micronutrients from various sample types.

Effects of physicochemical properties of carotenoids on their bioaccessibility, intestinal cell uptake, and blood and tissue concentrations.

SCOPE: Carotenoid bioavailability is affected by numerous factors. Our aim was to assess the involvement of known carotenoid physicochemical properties (e.g., hydrophobicity, van der Waals volume,…) on the transport of the main dietary carotenoids (ß-carotene, lycopene, lutein, and astaxanthin, from their food matrix to their main storage tissues. METHODS AND RESULTS: We used four complementary models: synthetic mixed micelles, an in vitro digestion procedure, Caco-2 cell monolayers, and a gavage experiment in rats. The efficiency with which pure carotenoids were incorporated into synthetic mixed micelles was related to their melting points (r = 0.99, p = 0.015). The efficiency with which pure carotenoids were transferred from dietary triglycerides into mixed micelles was related to carotenoid hydrophobicity (r = -1, p = 0.005). There was no relationship between the carotenoid physicochemical properties studied and their uptake efficiency by Caco-2. The postprandial plasma carotenoid response to carotenoid gavage was related to carotenoid hydrophobicity (r = -0.99, p = 0.006). Carotenoid adipose tissue response was not related to the carotenoid physicochemical properties studied. CONCLUSION: Thus, carotenoid hydrophobicity is important for bioaccessibility and postprandial blood response of carotenoids. In contrast, the carotenoid physicochemical properties studied are apparently not strong determinants of carotenoid uptake by enterocytes and adipose tissue.

Lycopene attenuates LPS-induced TNF-α secretion in macrophages and inflammatory markers in adipocytes exposed to macrophage-conditioned media.

SCOPE: Adipose tissue is infiltrated by an increasing number of macrophages during the development of obesity. These immune cells are suspected to be a major source of TNF-α that interferes with adipocyte function. Because lycopene possesses anti-inflammatory properties, we hypothesize that lycopene could reduce the production of TNF-α by macrophages and thus interfere in the cross-talk between macrophages and adipocytes. METHODS AND RESULTS: We demonstrated that physiological concentrations of lycopene were able to attenuate the lipopolysaccharide (LPS)-mediated induction of TNF-α in RAW 264.7 macrophages, at both the mRNA and protein levels. The molecular mechanism was studied. It appeared that the LPS-activation of both JNK and NF-κB signaling pathways was modulated by lycopene. The anti-inflammatory effects of lycopene on macrophages were accompanied by a decrease in LPS-stimulated macrophage migration in the presence of lycopene. Furthermore, lycopene decreased macrophage conditioned medium-induced proinflammatory cytokine, acute phase protein, and chemokine mRNA expression in 3T3-L1 adipocytes. CONCLUSION: These data indicate that lycopene displayed an anti-inflammatory effect on macrophages that beneficially impacted adipocyte function. Thus, these results suggest that lycopene could block the vicious cycle that occurs between adipocytes and macrophages in adipose tissue during obesity.

Phytosterols can impair vitamin D intestinal absorption in vitro and in mice.

SCOPE: Adequate vitamin D status is necessary and beneficial for health, although deficiency and insufficiency are very common. As cholecalciferol (vitamin D(3) ) structure is close to cholesterol structure, we hypothesized that phytosterols, frequently used to decrease cholesterol, intestinal absorption and consequently to reduce hypercholesterolemia, may also interact with cholecalciferol absorption. METHODS AND RESULTS: ß-Sitosterol effect on cholecalciferol postprandial response was first assessed in mice. We then evaluated the effect of different sterols on (i) cholecalciferol micellar incorporation, (ii) cholecalciferol apical uptake and (iii) basolateral efflux in vitro or ex vivo. In mice, cholecalciferol bioavailability was 15-fold lower in the presence of ß-sitosterol (p<0.05). This can partly be explained by the fact that phytosterols significantly impaired cholecalciferol incorporation into mixed micelles (from -16 to -36% depending on sterol micellar composition). This can also be due to the fact that in Caco-2 cells and mouse intestinal explants, phytosterols significantly lowered cholecalciferol apical uptake (from -13 to -39%). Conversely, phytosterols had no effect on cholecalciferol secretion at the basolateral side of Caco-2 cells. CONCLUSION: The present data suggest for the first time that phytosterols can interact with vitamin D(3) intestinal absorption. This interaction can be explained by a competition for micellar incorporation and for apical uptake.

CD36 is involved in lycopene and lutein uptake by adipocytes and adipose tissue cultures.

SCOPE: Carotenoids are mainly stored in adipose tissue. However, nothing is known regarding the uptake of carotenoids by adipocytes. Thus, our study explored the mechanism by which lycopene and lutein, two major human plasma carotenoids, are transported. METHODS AND RESULTS: CD36 was a putative candidate for this uptake, 3T3-L1 cells were treated with sulfosuccinimidyl oleate, a CD36-specific inhibitor. sulfosuccinimidyl oleate-treated cells showed a significant decrease in both lycopene and lutein uptake as compared to control cells. Their uptake was also decreased by partial inhibition of CD36 expression using siRNA, whereas the overexpression of CD36 in Cos-1 cells increased their uptake. Finally, the effect of CD36 on carotenoid uptake was confirmed ex vivo in cultures of adipose tissue explants from CD36(-/-) mice, which exhibited reduced carotenoid uptake as compared to wild-type mice explants. CONCLUSION: For the first time, we report the involvement of a transporter, CD36, in carotenoid uptake by adipocytes and adipose tissue.

Scavenger receptor class B type I (SR-BI) is involved in vitamin E transport across the enterocyte.

Although cellular uptake of vitamin E was initially described as a passive process, recent studies in the liver and brain have shown that SR-BI (scavenger receptor class B type I) is involved in this phenomenon. As SR-BI is expressed at high levels in the intestine, the present study addressed the involvement of SR-BI in vitamin E trafficking across enterocytes. Apical uptake and efflux of the main dietary forms of vitamin E were examined using Caco-2 TC-7 cell monolayers as a model of human intestinal epithelium. (R,R,R)-gamma-tocopherol bioavailability was compared between wild-type mice and mice overexpressing SR-BI in the intestine. The effect of vitamin E on enterocyte SR-BI mRNA levels was measured by real-time quantitative reverse transcription-PCR. Concentration-dependent curves for vitamin E uptake were similar for (R,R,R)-alpha-, (R,R,R)-gamma-, and dl-alpha-tocopherol. (R,R,R)-alpha-tocopherol transport was dependent on incubation temperature, with a 60% reduction in absorption at 4 degrees C compared with 37 degrees C (p < 0.05). Vitamin E flux in enterocytes was directed from the apical to the basal side, with a relative 10-fold reduction in the transfer process when measured in the opposite direction (p < 0.05). Co-incubation with cholesterol, gamma-tocopherol, or lutein significantly impaired alpha-tocopherol absorption. Anti-human SR-BI antibodies and BLT1 (a chemical inhibitor of lipid transport via SR-BI) blocked up to 80% of vitamin E uptake and up to 30% of apical vitamin E efflux (p < 0.05), and similar results were obtained for (R,R,R)-gamma-tocopherol. SR-BI mRNA levels were not significantly modified after a 24-h incubation of Caco-2 cells with vitamin E. Finally, (R,R,R)-gamma-tocopherol bioavailability was 2.7-fold higher in mice overexpressing SR-BI than in wild-type mice (p < 0.05). The present data show for the first time that vitamin E intestinal absorption is, at least in part, mediated by SR-BI.