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In-Depth Information
6 Vitamin E and Inflammation
T. Barker*
The Orthopedic Specialty Hospital, Murray, Utah, USA
Supplemental Vitamin E and Inflammatory Cytokines
Regulation of inflammatory cytokines by vitamin E
Additional cell-signalling mechanisms regulated by vitamin E
Summary and Conclusions
(a-, b-, g- and d-) (Fig. 6.1). Of the different
vitamin E forms, a-tocopherol is the most com-
mon form in supplements and European diets,
whereas g-tocopherol is the predominant form
found in the American diet (McLaughlin and
Weihrauch, 1979; Lehmann et al ., 1986). The
structural difference between the two tocophe-
rols is that a-tocopherol is fully substituted in
the chromanol ring and g-tocopherol is unsub-
stituted at the C-5 position (Fig. 6.1). The chiral
centers are in the 'R' configuration at the 2, 4
Vitamin E is a fat-soluble vitamin discovered
in 1922 (Evans and Bishop, 1922). Since its dis-
covery, it has become apparent that vitamin E
possesses a variety of biological functions,
including the modulation of inflammatory
cytokines. The regulatory influence of vitamin E
on cytokine production is the focus of this
chapter. This chapter begins with an overview
of vitamin E and then evidence identifying
the regulatory influence of different forms of
vitamin E on inflammatory cytokines, as well
as the physiological mechanisms that they
govern in cytokine production, is presented.
The chain-breaking antioxidant property
of vitamin E prevents the propagation of free
radicals in membranes and plasma lipoproteins
(Traber and Atkinson, 2007). Vitamin E exists
in eight different natural forms: four tocophe-
rols (a-, b-, g- and d-) and four tocotrienols
and 8
(i.e. RRR or d) positions in the naturally
occurring tocopherol form. Synthetic tocophe-
rols (called all-rac-a-tocopherol, all racemic or
dl) exist in other stereoisomer forms (i.e. RSR,
RRS, RSS, SRR, SSS, SRS and SSR). Tocotrienols
have substituted chromanol rings and, in con-
trast to tocopherols, unsaturated side chains.
All forms of vitamin E are absorbed in the
intestine and released into the circulation in
chylomicrons. Lipoprotein lipases hydrolyse
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