Medicinal Plants Classification Biosynthesis and ... - Index of

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Rosa Martha Perez Gutierrez, Adriana Maria Neira Gonzalez et al.
carotene content in national brand multivitamins. Four studies contributing 109,394 subjects
were available for analysis. The average daily beta-carotene dosage in these trials ranged
from 20 to 30 mg daily. High-dose β-carotene supplementation appears to increase the risk of
lung cancer among current smokers. Although beta-carotene was prevalent in multivitamins,
high-dose β-carotene was observed among multivitamin formulas sold to promote visual
health (Tanvetyanon and Bepler, 2008).
Gastrointestinal Cancer
The incidence of esophageal adenocarcinoma has been increasing rapidly among many
countries. Antioxidant intake is a potentially modifiable protective factor, although the results
from individual studies are inconclusive. In an study, were evaluated the associations
between vitamin C, vitamin E, or β-carotene/vitamin A and the risk of esophageal
adenocarcinoma or the adjacent gastric cardia (gastroesophageal junction) adenocarcinoma.
Studies (1 cohort, 9 case-control; 1,057 esophageal and 644 cardia cases). Higher intakes of
vitamin C, β-carotene/vitamin A, and vitamin E were inversely associated with the risk of
esophageal adenocarcinoma. β-Carotene intake was also inversely associated with the risk of
cardia adenocarcinoma. Pooled results from observational studies suggest that antioxidant
intake may be protective against esophageal adenocarcinoma; the data do not support a
consistent association between antioxidant intake and the risk of cardiac carcinoma. These
findings suggest possible etiological differences between these two adjacent malignancies
(Kubo and Corley, 2007).
Oxidative stress may cause gastrointestinal cancers. Epidemiologic studies of vitamin A,
retinol (preformed vitamin A), and provitamin A carotenoids in relation to the risk of gastric
cancer have documented inconsistent results. The evidence on whether antioxidant
supplements are effective in preventing gastrointestinal cancers is contradictory. Results
supported not find evidence that the studied antioxidant supplements prevent gastrointestinal
cancers. On the contrary, they seem to increase overall mortality (Bjelakovic et al., 2008).
Mechanisms of -Carotene in Cancer
Although several mechanisms have been proposed to explain the putative role of βcarotene
in cancer, no studies have investigated a possible influence of β-carotene on
caveolin-1 (cav-1) pathway, an important intracellular signalling deregulated in cancer.
Here, different human colon and prostate cancer cell lines, expressing (HCT-116, PC-3
cells) or not (Caco-2, LNCaP cells) cav-1, were treated with varying concentrations of
β-carotene (0.5-30 muM) for different periods of time (3-72 h) and the effects on cell
growth were investigated. The results of this study show that: a) β-carotene acted as a
growth-inhibitory agent in cav-1-positive cells, but not in cav-1-negative cells; b) in
cav-1-positive cells, the carotenoid down-regulated in a dose- and time-dependent
manner the expression of cav-1 protein and mRNA levels and inhibited AKT
phosphorylation which, in turn, stimulated apoptosis by increasing the expression of β-