Uptake of intact TPGS (d-a-tocopheryl polyethylene glycol 1 000 succinate) a water-miscible form of vitamin E by human cells in vitro13

ABSTRACT ’ The mechanism by which TPGS (a-tocopheryl succinate esterified to poly-ethylene glycol 1000 [PEG 1000]) delivers tocopherol (vitamin E) was studied in human fi-broblasts and erythrocytes and a human intestinal cell line, Caco-2. The total cellular tocoph-erol content of saponified samples of fibroblasts or Caco-2 incubated for 4 h with TPGS (4 imol/L) increased 10-fold without an increase in the free tocopherol content of nonsaponified samples. A 24-h incubation resulted in a free tocopherol content of 20%, suggesting that intracellular hydrolysis ofester bonds had occurred. The increase in total tocopherol content after a 4-h incubation with TPGS was temperature dependent; no change was measurable at 4 #{176}C.Addition ofmetabolic inhibitors during incubation with TPGS at 37 #{176}Cdid not prevent the increase. [‘4C]TPGS (synthesized from [‘4C]PEG 1000) was taken up by Caco-2 cells but [‘4C]PEG 1000 was not. The intracellular total tocopherol (pmol) equaled the [‘4C]TPGS (pmol), unequivocally demonstrating uptake ofthe intact TPGS molecule. Am JClin Nut