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)-␥-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)-␣-, (R,R,R)-␥-, and DL-␣-tocopherol. (R,R,R)-␣-tocopherol transport was dependent on incubation temperature, with a 60% reduction in absorption at 4°C compared with 37°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, ␥-tocopherol, or lutein significantly impaired ␣-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)-␥-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)-␥-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.

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.

For the first time, we report the involvement of a transporter, CD36, in carotenoid uptake by adipocytes and adipose tissue.