Postprandial chylomicron and plasma vitamin E responses in healthy older subjects compared with younger ones

Abstract

The effect of ageing on vitamin E bioavailability in humans was assessed by comparing chylomicron and plasma alpha-tocopherol postprandial concentrations after a dose of vitamin E (432 or 937 IU as d1-alpha-tocopherol acetate), in eight young (20-30 years old) and eight healthy elderly men (64-72 years old). The fasting plasma alpha-tocopherol concentration was significantly higher in the elderly (33 +/- 2 mumol L-1) than in the young (22 +/- 2 mumol L-1). In both groups, the plasma and chylomicron alpha-tocopherol postprandial concentrations were significantly, approximately twofold, higher after the 937-IU meal than after the 432-IU meal. For both test meals, the chylomicron alpha-tocopherol areas under the curve were significantly lower in the elderly than in the young subjects: 98.9 +/- 16.5 (young group) vs. 55.3 +/- 7.8 (elderly group) mumol L-1 h for the 937-IU test meal and 60.4 +/- 14.1 (young group) vs. 26.0 +/- 7.6 (elderly group) mumol L-1 h for the 432-IU test meal, whereas the plasma alpha-tocopherol area under the curve was significantly higher in elderly than in young subjects: 337.56 +/- 16.11 (937-IU test meal) vs. 159.81 +/- 35.55 (432-IU test meal) mumol L-1 h in the young group and 709.55 +/- 69.33 (937-IU test meal) vs. 436.39 +/- 41.08 (432-IU test meal) mumol L-1 h in the elderly group. We concluded that (a) the amount of vitamin E appearing in plasma is proportional to the dose ingested (up to 937 IU); (b) the intestinal absorption of vitamin E is not increased, even possibly decreased, in the elderly; and (c) the amount of vitamin E transported by non-chylomicron lipoproteins is apparently higher in the elderly. This suggests that vitamin E postprandial transport is affected by ageing, mainly as the consequence of age-related modifications of lipoprotein metabolism.

Effects of Fats and Oils on the Bioaccessibility of Carotenoids and Vitamin E in Vegetables

“…The lack of an effect of triacylglycerols on lutein might also have been due to the lower solubility of xanthophylls in fats and oils than that of -carotene. 18) This was not the case with -tocopherol because of its miscibility with oils.…”

“…The long-chain triacylglycerols of major edible oils were superior to the medium-chain triacylglycerols in enhancing the bioaccessibility of -carotene, although the solubility of carotenoids has been reported to be higher in trioctanoylglycerol (C8) than in such long-chain triacylglycerols (C18) as trioleoylglycerol and trilinoleoylglycerol. 18) This was quite unexpected, considering that triacylglycerol enhances the bioaccessibility of -carotene by dissolving carotenoid in its bulk phase. The bioaccessibility of -carotene in the presence of triacylglycerol was therefore not associated with the solubility of the carotenoids in triacylglycerol, although it was well associated with the effects of the corresponding free fatty acids per se as already mentioned.…”

Mechanisms for the prevention of vitamin E excess

“…Chylomicrons transport vitamin E from the intestine through the circulation to the liver ( 43,54 ). The body's preference for ␣ -tocopherol occurs as a result of the specifi c secretion of ␣ -tocopherol from the liver and the hepatic metabolism of non-␣ -tocopherol forms; this latter topic is discussed further below.…”

Mammalian carotenoid absorption and metabolism

“…Non-polar carotenes most likely migrate to the triacylglycerol-rich core of the particle, while the more polar xanthophylls orient at the surface monolayer along with proteins, phospholipids, and partially ionized fatty acids. Borel et al [31] reported this selective orientation of carotenoids in phospholipid-triacylglycerol droplets using an in vitro biological emulsion model. b-Carotene, a non-polar carotene, solubilized in the core of droplets, while zeaxanthin, a more polar xanthophyll, accumulated at the surface.…”