Vitamin E Bioavailability: Mechanisms of Intestinal Absorption in the Spotlight

Abstract

Vitamin E is an essential fat-soluble micronutrient whose effects on human health can be attributed to both antioxidant and non-antioxidant properties. A growing number of studies aim to promote vitamin E bioavailability in foods. It is thus of major interest to gain deeper insight into the mechanisms of vitamin E absorption, which remain only partly understood. It was long assumed that vitamin E was absorbed by passive diffusion, but recent data has shown that this process is actually far more complex than previously thought. This review describes the fate of vitamin E in the human gastrointestinal lumen during digestion and focuses on the proteins involved in the intestinal membrane and cellular transport of vitamin E across the enterocyte. Special attention is also given to the factors modulating both vitamin E micellarization and absorption. Although these latest results significantly improve our understanding of vitamin E intestinal absorption, further studies are still needed to decipher the molecular mechanisms driving this multifaceted process.

Vitamin E intestinal absorption: Regulation of membrane transport across the enterocyte

“…Among the dietary factors negatively affecting vitamin E absorption (see for review Ref. ), we showed in Caco‐2 cells that α‐tocopherol could compete for absorption with cholesterol, as well as with γ‐tocopherol, vitamin A, D, K, and carotenoids . Except for vitamin A, these competitions are likely due to shared uptake routes involving common transporters.…”

“…During the digestion process, vitamin E is extracted from its food matrix, dissolved in the fat phase of the bolus at the gastric level and finally incorporated into mixed micelles with other lipid hydrolysis products during duodenal digestion (see for review Ref. 7).…”

“…During the digestion process, vitamin E is extracted from its food matrix, dissolved in the fat phase of the bolus at the gastric level and finally incorporated into mixed micelles with other lipid hydrolysis products during duodenal digestion (see for review Ref. 7). Mixed micelles then diffuse through the unstirred water layer of the glycocalix area to approach the apical membrane of the enterocytes, i.e.…”

“…Furthermore, vitamin E metabolism is altered in SR-BI-deficient mice (15) and a protein analog to SR-BI can mediate vitamin E uptake in Drosophila (16). SR-BI was later confirmed to be a major protein in vitamin E intestinal uptake, at least in Caco-2 cell and mouse models (17), as well as in the uptake of fat-soluble micronutrients and phytochemicals in general (7). Interestingly, SR-BI was also shown to mediate vitamin E efflux from the cytosolic compartment of Caco-2 cells to the apical medium, suggesting a potential regulatory role of this protein in vitamin E cellular concentrations (10).…”

Hypercaloric Diet and Vitamin E Intake

“…In the duodenum, vitamin E is incorporated along with lipid digestion products in micelles which are then absorbed by enterocytes [13][14][15].…”