TRL-plasma concentrations of retinyl esters increased in response to consumption of both biofortified cassava porridge and gari, and the VA equivalencies of beta-carotene in porridge and gari were estimated as ~4.
TRL-plasma concentrations of retinyl esters increased in response to consumption of biofortified maize porridge, and the VA equivalence of beta-carotene was estimated as 6.
The diet provides retinol as retinyl esters or as provitamin carotenoids, and majority of them are stored within the hepatic lipid droplets (Blaner et al.
CRBP II binds specifically to retinol or retinal, and the CRBP II-retinal and CRBP II-retinol complexes serve as substrate not only for the conversion of retinal into retinol, but also for the conversion of retinol into retinyl esters (Suruga et al.
Topical beta-carotene penetrated well into human and mouse epidermis and induced a 10-fold (human) and a threefold (mouse) increase of epidermal retinyl esters
, which demonstrates that topical beta-carotene is converted into retinyl esters
by human and mouse epidermis and thus appears as a precursor of epidermal vitamin A.
Retinoids allowed for use in cosmetic products include retinol and retinyl esters
(for example, retinyl palmitate).
In addition, the concentrations of retinyl esters
after ingestion of a fat-rich meal containing vitamin A have been used as markers of the presence of apo B-48-containing RLPs of intestinal origin.
Retinol, alpha-tocopherol, lutein/zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, trans-beta-carotene, and four retinyl esters
in serum determined simultaneously by reversed-phase HPLC with multi-wavelength detection.
This can lead to a buildup in the liver of compounds called retinyl esters
, which can be toxic in large amounts.
Anthropometric measurements and blood pressure were assessed upon enrollment, and blood samples were analyzed for the antioxidant nutrients retinol, retinyl esters
, carotenoids, vitamin C and vitamin E, as well as glucose, lipids, C-reactive protein, and other factors.
Retinol and retinyl esters
are already present in skin where they account for more than 99% of the total cutaneous retinoids, but retinaldehyde and ATRA are present at the limit of detection.
Because the former determination is difficult to obtain by immunological techniques due to the identity of apolipoprotein B48 with the amino terminus of apolipoprotein B100 (a marker for lipoproteins secreted by the liver), several investigators have decided to determine retinyl esters
after a fatty meal containing high doses of retinyl palmitate as a marker of chylomicrons and chylomicron remnants (10-15).