Skin Aging Photoaging

The aging of skin is an intrinsic, degenerative process over time, comparable to what occurs in other organs, that results in a thinner but smooth skin with reduced elasticity. This process is superimposed to varying degrees by premature (extrinsic) aging caused by exposure to environmental stress, e.g., ultraviolet (UV) radiation. Photoaged skin occurs at unshielded body sites such as the face and the backside of hands as a consequence of chronic overexposure to natural or artificial sunlight...

Conclusions

Although ascorbic acid functions as an important water-soluble antioxidant, it has effects separate and apart from its antioxidant properties. We used the NHANES III data set to examine the relation of ascorbic acid to CVD and nontraditional CVD risk factors, gallbladder disease, lead toxicity, bone mineral density, and serologic evidence of infection with Helicobacter pylori. These analyses have a number of strengths and limitations. First, NHANES III data are available for analysis to the...

Formation of Lipid Hydroperoxides

Lipid hydroperoxides are formed nonenzymatically by reactive oxygen species (ROS) such as superoxide (O2 -), peroxide (O22-), and hydroxyl radical (HO). The endogenous pathways for ROS generation include normal mitochondrial aerobic respiration, phagocytosis of bacteria or virus-containing cells, peroxisomal-mediated degradation of fatty acids, and cytochrome P450-mediated metabolism of xenobiotics DNA (26). Mixtures of vitamin C and transition metal ions (27), and the conversion of catechols...

Basic Research on Role of Vitamin E in Atherosclerosis

The scientific rationale for vitamin E supplements protecting against atherosclerosis and its clinical complications is based primarily on the LDL oxidation theory of atherosclerosis (1). Accordingly, a-tocopherol (the most active form of vitamin E) is the most abundant radical scavenger of LDL (15) and may prevent a number of athero-genic events. These include the adhesion of leukocytes to endothelial cells (16), endothelial dysfunction (17), platelet aggregation (18), and the proliferation of...

Molecular Properties of aTocopherol Antioxidant and Nonantioxidant Functions

It is commonly believed that phenolic compounds such as vitamin E play only a protective role against free radical damage and that vitamin E is the major hydrophobic chain-breaking antioxidant that prevents the propagation of free radical reactions in membranes and lipoproteins. The antioxidant properties of vitamin E are well known (33), especially in connection with the prevention of low density lipoprotein (LDL) oxidation (34), although the correlation between LDL oxidation and...

Definitions of Bioavailability and Potency

Bioavailability is defined as the rate and extent of a drug's appearance in blood. The purpose of conducting bioavailability studies comparing two drugs is to determine whether they are bioequivalent. Bioequivalence has been defined as follows Two medicinal products are bioequivalent if they are pharmaceutical equivalents (containing the same amount of the same active substance in the same form) or pharmaceutical alternatives (containing the same active moiety but in a different chemical form,...

Vitamin E Kinetics During Pregnancy and Lactation in Sows

The biological activities of RRR- and all-rac-a-tocopherols were also evaluated during pregnancy and lactation, using pigs as a model system (27). Vitamin E delivery to fetuses and to suckling piglets was monitored by feeding 150 mg each of dj-RRR-a-and d6-all-rac-a-tocopheryl acetates daily to 3 pregnant sows from 7 d before to 7 d after birth. Blood from fasting sows was obtained in the morning of d -7, -4, 1, and 4 (during supplementation, d 1 was delivery day) and on d 7, 14, 21. Sow's...

Milestones in Vitamin E Research

Four milestones of vitamin E research have been recognized, namely, (i) its biological importance in reproduction and essentiality as a micronutrient (ii) its unique role as lipophilic antioxidant in lipoproteins and cell membranes (iii) its effects on cell signaling and gene expression and (iv) the identification of vitamin E deficiency diseases and the recognition of beneficial effects of vitamin E in human health and disease prevention. Milestone I Biological importance of vitamin E in...

Collaborative Group for the Primary Prevention Project PPP

In the Primary Prevention Project (PPP), the investigators followed 4495 people with hypertension, hypercholesterolemia, diabetes, obesity, family history of premature Mi, or those who were elderly (25). The mean age of the patients was 64.4 y and 58 were women. The patients were prescribed either aspirin (100 mg d) or all-rac-AT (300 mg d). This was a 2 x 2 factorial design study with a mean follow-up period of 3.6 y. The primary end point of this study was cardiovascular death, nonfatal Mi,...

Iron Overload and Iron Toxicity

Vitamin C promotes the absorption of dietary nonheme iron and contributes to the prevention of iron deficiency anemia (53,54). Mealtime vitamin C in the range of 50-100 mg has the most marked effect on iron absorption, and supplemental vitamin C beyond these levels had minimal additional effects on iron status in healthy individuals (55). Whether vitamin C supplementation might enhance the uptake and storage of nonheme iron in individuals with iron-overload pathologies (e.g., hereditary...

Lack of Bioequivalence of RRR and allracaTocopherols

Bioequivalence implies comparable bioavailability and biopotency (9). Different formulations are bioequivalent if the rate and extent of absorption of the active ingredients are not significantly different when administered under similar conditions, or result in the same concentration vs. time curves, or if all of their effects are identical (10). RRR- and all-rac-a-tocopherols have not been proven to meet any of these criteria for bioequivalence thus, they must be presumed to be different...

Vitamin C

Vitamin C is an essential micronutrient for humans, who have lost the ability to synthesize ascorbic acid due to a mutation in the gene coding for L-gulono-y-lactone oxidase (1). A lack of vitamin C in the human diet causes the deficiency disease scurvy. The current Recommended Dietary Allowance (RDA) for vitamin C is 75 mg d for women and 90 mg d for men (2). The RDA for men is based on near-maximal neutrophil concentration and minimal urinary excretion of vitamin C at daily doses of between...

Summary

There is strong indication that a decreased bioavailability of endothelium-derived NO predisposes to atherosclerosis and related disease states. Among other factors, oxidative stress might be responsible for the development of endothelial dysfunction, implying that atherogenesis and progression of atherosclerosis can be inhibited by antioxidants. This concept is supported by the consistent finding that ascorbic acid can facilitate endothelium-dependent vasodilation. The data presented and...

Transition Metal Ions Vitamin C and ROS

Transition metal ion-mediated Haber Weiss reactions are known to produce ROS, which then cause oxidative damage to the DNA. Vitamin C is used as an antioxidant because it can prevent such damage (32). When vitamin C reacts with hydrogen peroxide, the vitamin C radical anion and a hydroxyl radical are produced. The reactive hydroxyl radical is then detoxified by reaction with vitamin C radical anion or vitamin C itself to give a water molecule. If the vitamin C radical anion reacts with the...

Systemic Conditioning Rebound Scurvy

There is some evidence that systemic conditioning (the accelerated metabolism or disposal of ascorbic acid) may occur after prolonged supplementation of high doses of vitamin C. The physiologic relevance of accelerated vitamin C metabolism in otherwise healthy individuals, however, has not been addressed adequately. In human subjects consuming a vitamin C-deficient diet (5 mg d) in a live-in metabolic unit, abrupt withdraw of vitamin C supplementation (600 mg d for 3 wk) was associated with a...

Antioxidant Supplementation in Atherosclerosis Prevention Study ASAP Study

The ASAP study was a randomized trial of the effect of vitamin E and C on 3-y progression of carotid atherosclerosis. This was a placebo-controlled, randomized, 2 x 2 factorial trial in hypercholesterolemic patients and consisted of an 8-wk placebo lead-in phase, followed by a 3-y double-blind treatment period 26 . Subjects n 520 were randomly assigned to receive RRR-AT 136 iu twice a day , slow release ascorbate 250 mg twice a day , or both RRR-AT and ascorbate or placebo. Carotid...