Transport and distribution of α-tocopherol in lymph, serum and liver cells in rats

Bjørneboe, Anders; Bjørneboe, Gunn‐Elin Aa.; Bodd, Egil; Hagen, Bente F.; Kveseth, N. J.; Drevon, Christian A.

doi:10.1016/0167-4889(86)90193-x

Cited by 99 publications

(55 citation statements)

References 28 publications

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“…These variations are most likely due to individual differences in α-TOH distribution in the lipoproteins caused by differing dietary α-TOH intake, metabolic states [68] , and other factors influencing bioavailability and the status of vitamin E. In addition, results obtained from human studies regarding the distribution of α-TOH to lipoproteins differ from studies performed on rodents. As shown by Bjørneboe et al [67] , under non-fasting conditions in rats 51% of serum α-TOH were associated with chylomicrons and VLDL whereas 47% were found within HDL. These differences across species highlight clearly the complexity of this topic.…”

Section: Vascular Transportmentioning

confidence: 89%

“…Vitamin E metabolism stereoisomer [65,66] . Under normal physiological conditions, α-TOH is mostly transported via chylomicrons, very low density lipoproteins (VLDL) and high density lipoproteins (HDL), whereas under fasting conditions low density lipoproteins (LDL) take on this task [67] . The distribution ratio of α-TOH between the different types of lipoproteins is difficult to define.…”

Section: Vascular Transportmentioning

confidence: 99%

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Complexity of vitamin E metabolism

Schmölz¹,

Birringer²,

Lorkowski³

et al. 2016

WJBC

183

138

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Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e. , when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their sidechain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a REVIEW

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Section: Vascular Transportmentioning

confidence: 89%

Section: Vascular Transportmentioning

confidence: 99%

Complexity of vitamin E metabolism

Schmölz¹,

Birringer²,

Lorkowski³

et al. 2016

WJBC

183

138

View full text Add to dashboard Cite

show abstract

“…8). Since chylomicron remnants are the primary source of α-T for liver (Bjorneboe et al, 1986;Kaempf-Rotzoll et al, 2003;Traber et al, 1988) and hepatic α-T is less severely depleted than that of the other tissues, it is inferred that α-TTP deficiency has a modest effect on the uptake of α-T from chylomicron remnants.…”

Section: Liver Is Spared From Severe α-T Deficiency In α-Ttp-ko Micementioning

confidence: 99%

Mice lacking α-tocopherol transfer protein gene have severe α-tocopherol deficiency in multiple regions of the central nervous system

et al. 2008

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Ataxia with vitamin E deficiency is caused by mutations in α-tocopherol transfer protein (α-TTP) gene and it can be experimentally generated in mice by α-TTP gene inactivation (α-TTP-KO). This study compared α-tocopherol (α-T) concentrations of five brain regions and of four peripheral organs from 5 months old, male and female, wild-type (WT) and α-TTP-KO mice. All brain regions of female WT mice contained significantly higher α-T than those from WT males. α-T concentration in the cerebellum was significantly lower than that in other brain regions of WT mice. These sex and regional differences in brain α-T concentrations do not appear to be determined by α-TTP expression which was undetectable in all brain regions. All the brain regions of α-TTP-KO mice were severely depleted in α-T. The concentration of another endogenous antioxidant, total glutathione, was unaffected by gender but was decreased slightly but significantly in most brain regions of α-TTP-KO mice. The results show that both gender and the hepatic α-TTP, but not brain α-TTP gene expression are important in determining α-T concentrations within the brain. Interestingly, functional abnormality (ataxia) develops only very late in α-TTP-KO mice in spite of the severe α-tocopherol deficiency in brain starting at an early age.

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“…In the rat, maximal absorption takes place at the junction between the upper and middle thirds of the small intestine (Hollander et al 1975;Gallo-Torres, 1980). Within the mucosal cell, a-tocopherol combines with other lipids and with apoproteins, forming lipoproteins such as the chylomicrons, in which form it is transported out of the cells (Bjorneboe et al 1986;Traber et al 1988). Intracellular a-tocopherol transport does not appear to rely on a transfer protein (Catignani & Bieri, 1977).…”

Section: Symposium On 'Micronutrient Transport Processes' Tocopherol mentioning

confidence: 99%