References
181. Selenium.
Barceloux DG
dgbarcelou@aol.com
J Toxicol Clin Toxicol, 1999, 37:2, 145?72
The 4 natural oxidation states of selenium are elemental
selenium (0), selenide (?2), selenite (+4), and selenate
(+6). Inorganic selenate and selenite predominate in water
whereas organic selenium compounds (selenomethionine,
selenocysteine) are the major selenium species in cereal and
in vegetables. The principal applications of selenium include
the manufacture of ceramics, glass, photoelectric cells,
pigments, rectifiers, semiconductors, and steel as well as
use in photography, pharmaceutical production, and rubber
vulcanizing. High concentrations of selenium in surface and
in ground water usually occur in farm areas where irrigation
water drains from soils with high selenium content (Kesterson
Reservoir, California) or in lakes receiving condenser
cooling water from coal?fired electric power plants (Belews
Lake, North Carolina). For the general population, the
primary pathway of exposure to selenium is food, followed by
water and air. Both selenite and selenate possess substantial
bioavailability. However, plants preferentially absorb
selenates and convert them to organic compounds. Aquatic
organisms (e.g., bivalves) can accumulate and magnify
selenium in the food chain. Selenium is an essential
component of glutathione peroxidase, which is an important
enzyme for processes that protect lipids in polyunsaturated
membranes from oxidative degradation. Inadequate
concentrations of selenium in the Chinese diet account, at
least in part, for the illness called Keshan disease.
Selenium deficiency occurs in the geographic areas where
Balkan nephropathy appears, but there is no direct evidence
that selenium deficiency contributes to the development of
this chronic, progressive kidney disease. Several lines of
scientific inquiry suggest that an increased risk of cancer
occurs as a result of low concentrations of selenium in the
diet; however, insufficient evidence exists at the present
time to recommend the use of selenium supplements for the
prevention of cancer. The toxicity of most forms of selenium
is low and the toxicity depends on the chemical form of
selenium. The acute ingestion of selenious acid is almost
invariably fatal, preceded by stupor, hypotension, and
respiratory depression. Chronic selenium poisoning has been
reported in China where changes in the hair and nails
resulted from excessive environmental exposures to selenium.
Garlic odor on the breath is an indication of excessive
selenium exposure as a result of the expiration of dimethyl
selenide. The US National Toxicology Program lists selenium
sulfide as an animal carcinogen, but there is no evidence
that other selenium compounds are carcinogens.
182. Selenium and
cardiovascular diseases??an update.
Huttunen JK
National Public Health Institute, Helsinki, Finland.
Biomed Environ Sci, 1997 Sep, 10:2?3, 220?6
Dietary deficiency of selenium has been incriminated in
the etiology of cardiovascular diseases. Thus, cardiomyopathy
associated with low selenium intake has been described in
areas of exceptionally low selenium intake and in patients
receiving total parenteral nutrition. Epidemiological studies
have provided some evidence for the role of selenium
deficiency in the etiology of atherosclerotic disease. An
inverse association between the incidence of ischaemic heart
disease and selenium intake has been described in population
comparisons. The results of longitudinal studies within
populations are conflicting. While some investigations have
observed a relationship between low serum?selenium levels and
the risk of coronary disease, others have not. Final evidence
for the role of selenium in preventing atherosclerotic
disease can be obtained only from controlled prevention
trials.
183. Selenium and
cardiovascular pathology
Neve J
UnitÆe de Toxicologie et de Chimie Bioanalytique,
FacultÆe de MÆedecine et de Pharmacie,
UniversitÆe Libre de Bruxelle, Belgique.
Pathol Biol (Paris), 1989 Dec, 37:10, 1102?6
Selenium deficiency has established implications in
cardiovascular diseases, particularly on cardiac muscle
integrity. The essential trace element takes part not only in
the direct protection of endothelial cells against the
accumulation of aggressive oxygen species, but also in the
biosynthesis of arachidonic acid derivatives involved in
platelet and leucocyte functions, or in the regulation of
cholesterol. Moreover, it prevents toxic effects of cadmium
and mercury, and modulates the active transport of calcium.
Some clinical investigations have underlined its importance
in the cardiac function and the prevention of coronary
atherosclerosis, and several recent prospective
epidemiological studies have attributed to selenium
deficiency a greater incidence of cardiovascular diseases.
Further studies should be devoted to the influence of
marginal deficiency in this trace element whose optimal
requirement does not seem to be met by the usual dietary
intake.
184. Association between
beta?carotene and acute myocardial infarction depends on
polyunsaturated fatty acid status. The EURAMIC Study.
European Study on Antioxidants, Myocardial Infarction, and
Cancer of the Breast.
Kardinaal AF; Aro A; Kark JD; Riemersma RA; van t Veer P;
Gomez Aracena J; Kohlmeier L; Ringstad J; Martin BC; Mazaev
VP; et al
Department of Epidemiology, TNO Nutrition and Food Research,
Zeist, Netherlands.
Arterioscler Thromb Vasc Biol, 1995 Jun, 15:6, 726?32
Because antioxidants may play a role in the prevention of
coronary heart disease by inhibiting the peroxidation of
polyunsaturated fatty acids (PUFAs), the combined association
of diet?derived antioxidants and PUFAs with acute myocardial
infarction (MI) was investigated. This multicenter
case?control study included 674 patients and 725 control
subjects in eight European countries and Israel. Fatty acid
composition and alpha?tocopherol and beta?carotene levels
were determined in adipose tissue; selenium level was
determined in toenails. For alpha?tocopherol no association
with MI was observed at any PUFA level. The overall
multivariate odds ratio (OR) for low (10th percentile) versus
high (90th percentile) beta?carotene was 1.98 (95% confidence
interval [CI], 1.39 to 2.82). The strength of this inverse
association with MI was dependent on PUFA levels (in
tertiles): for low PUFA, the OR for low versus high
beta?carotene was 1.79 (95% CI, 0.98 to 3.25), for medium
PUFA the OR was 1.76 (95% CI, 1.00 to 3.11), and for high
PUFA 3.47 (95% CI, 1.93 to 6.24). For selenium increased risk
was observed only at the lowest PUFA tertile (OR, 2.49; 95%
CI, 1.22 to 5.09). This interaction between selenium and
PUFAs was not significant and may at least partly be
explained by a higher proportion of smokers at the low PUFA
level. These findings support the hypothesis that
beta?carotene plays a role in the protection of PUFAs against
oxidation and subsequently in the protection against MI. No
evidence was found that alpha?tocopherol or selenium may
protect against MI at any level of PUFA intake.
185. Antioxidants and coronary
heart disease.
van Poppel G; Kardinaal A; Princen H; Kok FJ
Department of Epidemiology, TNO Nutrition and Food Research
Institute, Zeist, The Netherlands.
Ann Med, 1994 Dec, 26:6, 429?34
This review briefly summarizes the scientific evidence for
a possible role of antioxidants in the prevention of coronary
heart disease (CHD). Antioxidants in our diet include
vitamins E, C, and beta?carotene, whereas selenium is an
integral part of the antioxidant enzyme glutathione
peroxidase (GSHPx). Experimental evidence suggests that
free?radical damage and antioxidant defence may play an
important role in the development of coronary heart disease.
Epidemiological studies have produced some intriguing
results, but have not indicated unequivocally that a high
intake of antioxidants leads to a decreased cardiovascular
disease risk. We conclude that the antioxidant
atherosclerosis hypothesis is promising, but that the results
of long?term intervention studies are still to be awaited.
Preventive action based on antioxidant supplementation is
therefore not justifiable as yet. Nevertheless, the findings
so far certainly do support the recommendations for a varied
diet rich in vegetables and fruit.
186. Selenium, glutathione
peroxidase, peroxides and platelet functions
Vitoux D; Chappuis P; Arnaud J; Bost M; Accominotti M;
Roussel AM
Laboratoire central de biochimie, hÈopital
LariboisiÄere, Paris, France.
Ann Biol Clin (Paris), 1996, 54:5, 181?7
In the last five years, there has been a renewal of
interest in the protective role of selenium in vascular
disorders, inspired by experimental evidence that this trace
element could modulate leukotriene and prostaglandin
synthesis in both endothelial cells and platelets. In people
living in low?selenium areas, a relationship has been
established between a decrease in plasma selenium and an
increase in the risk of coronary disease, atherosclerosis,
platelet hyperaggregability and synthesis of proaggregant and
proinflammatory compounds like thromboxane A2 and
leukotrienes. Selenium, as an essential part of glutathione
peroxidase, takes part in the reduction of hydrogen peroxides
and lipid peroxides. The concentration of these peroxides, in
turn, regulates the activities of cyclooxygenase and
lipooxygenase pathways, ultimately influencing the production
of eicosanoids and modulating the balance between a
proaggregatory and antiaggregatory state.Recent evidence
shows that selenium, via its action on glutathione peroxidase
activity, may be primarily responsible for the regulation of
the endogenous hydroperoxide level. In human platelets, the
activity of glutathione peroxidase is particularly high and
is very sensitive to the requirement of selenium. This
sensitivity could explain why platelets of selenium?deficient
subjects show increased aggregation, thromboxane B2
production and synthesis of the lipoxygenase?derived
compounds. In these deficient subjects, selenium
administration increases platelet glutathione peroxidase
activity and inhibits platelet hyperaggregation and
leukotriene synthesis. These results support the hypothesis
that selenium supplementation has a positive effect on
platelet aggregation in selenium?deficient subjects. In
France, more than 10% of the population is selenium?deficient
and long?term supplementation with low doses of selenium
could have a beneficial effect on the prevention of both
thrombosis and coronary heart disease in these
subjects.
187. Selenium as a risk factor
for cardiovascular diseases.
Nève J
UniversitÆe Libre de Bruxelles, Institut de Pharmacie,
Belgium.
J Cardiovasc Risk, 1996 Feb, 3:1, 42?7
Selenium is a powerful antioxidant regulating the activity
of the glutathione peroxidase enzymes, which catalyse the
detoxification of hydrogen peroxide and organic
hydroperoxides. Selenium deficiency has been implicated in
the aetiopathogeny of Keshan disease, an endemic
cardiomyopathy observed in China, and in other cases of
congestive cardiomyopathy in subjects on artificial
nutrition. However, the evidence from case?control and
prospective studies for an association between low selenium
status and cardiovascular diseases remains controversial.
Mechanisms whereby selenium protects against such diseases
include increased resistance of
low?density lipoproteins against oxidative modification,
modulation of prostaglandin synthesis and platelet
aggregation, and protection against toxic heavy metals. The
therapeutic benefit of selenium administration in the
prevention and treatment of cardiovascular diseases still
remains insufficiently documented.
188. Natural antioxidants for
the prevention of atherosclerosis.
Odeh RM; Cornish LA
Department of Pharmacy Services, University of Michigan
Medical Center and College of Pharmacy, Ann Arbor 48109,
USA.
Pharmacotherapy, 1995 Sep, 15:5, 648?59
Hypercholesterolemia, cigarette smoking, hypertension, and
obesity are known contributing risk factors for the
development of atherosclerotic coronary artery disease (CAD).
However, they account for only half of all cases of CAD, and
the complete pathologic process underlying atherosclerosis
remains unknown. Growing evidence suggests that oxidative
modification of low?density lipoprotein (LDL) may be of
particular importance in the pathogenesis. Oxidized LDL
exhibits proatherogenic effects. Therefore, current research
has focused on inhibiting the oxidation of LDL as a means of
inhibiting the atherosclerotic process. One such approach is
to enhance the endogenous antioxidant defense systems within
the LDL particle with lipophilic antioxidants such as
alpha?tocopherol and beta?carotene, or by supplementing the
aqueous?phase antioxidant capacity with ascorbic acid.
Observational data suggest a protective effect of antioxidant
supplementation on the incidence of CAD; however, specific
doses cannot be recommended since the data are
inconclusive.
189. Nutrition in the
prevention of ischemic heart disease
Ginter E
Bratisl Lek Listy, 1989 Mar, 90:3, 203?21
The survey presents current knowledge on the role of
nutrition in prevention of
hypercholesterolemia and ischemic heart disease. From the
standpoint of their role in atherogenesis, nutritional
factors can be divided into protective and risk factors. The
group of protective factors includes n?3 and n?6
polyunsaturated fatty acids, oleic acid, plant sterols, plant
lecithins, some fiber components (e.g. pectin), plant
proteins (e.g. soybean), vitamin C, vitamin E, magnesium,
potassium, calcium, chromium, and selenium. The group of risk
factors comprises saturated fatty acids, cholesterol,
sucrose, sodium, vitamin D, and ethanol. After World War II
the development of food consumption in Czechoslovakia
resulted in an imbalanced state persisting for some decades
now which is characterized by a high involvement of risk
factors (high consumption of meat, sausages, animal fats,
eggs, common salt, and alcoholic beverages) and by a low
involvement of protective factors (low consumption of
vegetables, fruit, potatoes, legumes, fish, and roughly
milled grain). The imbalance of risk and protective factors
in nutrition is conceivably one of the main causes of the
extremely high mortality from cardiovascular diseases in
Czechoslovakia. The current unfavorable trend in the rate of
ischemic heart disease and in life expectancy of the
population in Czechoslovakia can not be reversed without
substantial changes in the composition of nutrition.
190. Recent nutritional
approaches to the prevention and therapy of cardiovascular
disease.
Kendler BS
Manhattan College, NY, USA.
Prog Cardiovasc Nurs, 1997 Sum, 12:3, 3?23
Nutritional factors play an important role in the
development and treatment of cardiovascular disease (CVD).
However, health care professionals may overlook, or even
disregard, some of these factors for several reasons,
including inadequate training and conflicting reports in the
biomedical literature. This review provides a synopsis of
more than two?dozen nutritional approaches to primary and
secondary prevention and therapy of CVD. Favorable
cardiovascular effects have been reported with the use of
unsaturated fatty acids, vegetarian and semi?vegetarian
diets, dietary fiber, plant sterols, alcoholic beverages,
vitamins (niacin, E, C, B6, B12, folate), minerals
(potassium, calcium, magnesium, selenium),
conditionally?essential nutrients (coenzyme Q10, L?carnitine,
taurine) and botanical agents (garlic, hawthorn, gugulipid).
In contrast, trans?fatty acids, oxysterols, homocysteinemia,
carbohydrate intolerance, and excessive sodium chloride and
iron have been associated with undesirable cardiovascular
effects. A nutritional approach to CVD provides a pivotal
adjuvant to traditional pharmaceutical and/or surgical
interventions by maximizing the likelihood of success in
decreasing CVD morbidity and mortality and minimizing the
economic and social costs associated with this disease.