What's Hot Archive
January 30, 2002
Aspirin has antioxidant properties
Aspirin is well known for its ability to help prevent cardiovascular disease, attributable to its anticoagulant and antiinflammatory properties. Because oxidative stress also plays a strong role in heart disease, researchers at the University of Montreal in Quebec sought to determine what effect aspirin has on superoxide anion generation in a rat model.
Tissue was taken from the aortas of four rats and incubated with aspirin at room temperature for ten minutes before the production of superoxide anions was quantified. In order to determine aspirin's effect in vivo, 100 milligrams per kilogram aspirin was given to five groups of rats for either zero, three, six, nine or twelve days. Control groups of rats received either water or varying doses of aspirin for twelve days. In a separate experiment, rats received angiotensin II, a hypertension-inducing agent, alone or in combination with aspirin. In yet another experiment, normal and spontaneously hypertensive rats were treated with aspirin for 53 days or were or were part of a control group. Blood pressure was measured throughout the course of the experiment. Aortic and smooth muscle cells from similar rats were cultured and superoxide anion levels measured.
Although no short term benefits were provided by aspirin in vitro and in vivo, longterm treatment consisting of 100 milligrams per kilogram daily for twelve days reduced superoxide anion production by 27% in the aortas of normal mice and by 45% in those of hypertensive rats. Oxidation was also found to be lower in smooth muscle cells incubated with aspirin. In rats given angiotensin II, hypertension and oxidative stress were both prevented. In the spontaneously hypertensive rats studied, aspirin was found to significantly benefit the age-dependent development of hypertension.
The researchers concluded that longterm aspirin treatment "markedly reduced vascular superoxide anion production", and that the antioxidant properties "are likely involved in the restoration of aortic vasorelaxation." (Circulation 105:387,January 29 2002)
January 28, 2002
Antioxidant prevents onset of diabetes type 1 in mice
A study funded by the National Institutes of Health and the National Heart, Lung and Blood Institute conducted at two centers in Denver, Colorado, revealed that a synthetic oxidant called AEOL 10113 prevents or delays the onset of diabetes type 1 in mice. The antioxidant mimics the body's naturally occurring antioxidant superoxide dismutase, but is longer lasting and effective against a greater number of oxidative substances. It was found to protect the beta cells of the pancreas (which produce insulin) from the oxygen radicals generated by the disease, as well as preventing the immune system from recognizing and attacking these cells, which is what occurs in this form of diabetes. The research was published in the February 2002 issue of the journal Diabetes.
The antioxidant was injected by the researchers into a group of mice the day before the mice received transplants of T cells that cause diabetes type 1. The mice then received AEOL 10113 four times during a nine day period. The control mice who did not receive the antioxidant were diagnosed with diabetes on the thirteenth day of the study, but the mice receiving the antioxidant did not develop the disease until the twenty-first day. At four weeks, half of this group were still free of the disease.
Study coauthor and Chairman of the Department of Medicine at National Jewish Medical and Research Center, James Crapo MD, commented, "These data show that antioxidants protect against diabetes on two fronts. They not only mop up destructive oxygen radicals, but also alter the immune response. That suggests the intriguing possibility that we might one day treat a variety of autoimmune diseases by altering the oxidant/antioxidant balance of immune system . . . Obviously we have a long way to go. But we believe that these findings have opened a very promising new line of research."
January 25, 2002
Whole organ viable after freezing
The January 24 2002 issue of the journal Nature, announced that whole ovaries have been frozen and reimplanted in rats, allowing them to later conceive. The success of the procedure is a boon to women who face sterilization due to chemotherapeutic procedures, who may be able to have ovarian tissue frozen, allowing them to have children in the future. Yet the greater impact may be on transplant surgery in general, which has for decades been dependent upon the availability of fresh donor organs.
The researchers utilized eight fresh ovaries and reproductive tracts from donor rats, and seven that had been perfused with a solution containing fructose and varying concentrations of dimethylsulfoxide, and frozen overnight in liquid nitrogen. The organs were thawed the following day, and the cryoprotectant removed prior to implantation in a group of recipient rats who had their ovaries removed.
All of the animals who received the fresh transplants restarted their estrus cycles and maintained normal hormone levels and normal numbers of ovarian follicles. Over half the rats who received the cryopreserved tissue had ovaries which produced follicles and showed evidence of ovulation. One animal in the group became pregnant after mating. The nonovarian reproductive tract tissue received by this group was not distinguishable from that of a control group of rats who did not receive transplanted tissue.
The authors state that the problem of intravascular ice formation which may be responsible for the limitations in using frozen organs may be overcome by advances in vitrification, a low temperature technology that does not create ice crystals.
January 23, 2002
Mechanism of action found for vitamin C against cancer
A letter published in the January 12, 2002 issue of The Lancet suggests an explanation for the benefit of vitamin C against cancer. Researchers from Cornell University and Seoul National University in Korea discovered that the vitamin inhibits the cancer-causing effects of hydrogen peroxide on communication between cells. They also found that the phytochemical quercetin, which exists in apples and other plant foods, has an even stronger effect than vitamin C.
Study coauthor Professor C Y Lee of Cornell explained, "Vitamin C has been considered one of the most important essential nutrients in our diet since the discovery in 1907 that it prevents scurvy. In addition, vitamin C has several important functions in our body for the synthesis of amino acids and collagen, wound healing, metabolism of iron, lipids and cholesterol and others. In particular, vitamin C is a well known antioxidant that scavenges free radicals. Vitamin C prevents the inhibition of gap-junction intercellular communication (GJIC) induced by hydrogen peroxide."
Gap junction intercellular communication is necessary for the maintenance of normal cell growth and differentiation, and when inhibited, is associated with cancer promotion. Hydrogen peroxide, which is known to promote tumor growth, inhibits GJIC by modification of a protein. The researchers pretreated rat liver epithelial cells with vitamin C and found that hydrogen peroxide was unable exert this inhibitory effect, while other antioxidants tested failed to prevent it. This suggests that vitamin C's mechanism of action in tumor inhibition is other than that of an a free radical scavenger, and that prevention of CJIC is more likely. They conclude that "a diet rich in phytochemicals and vitamin C will reduce the risk of cancer."
January 21, 2002
Don't forget B12
A research letter published in the January 18 2002 issue of The Lancet emphasized the role of vitamin B12 in lowering homocysteine and suggested that the vitamin be included with folic acid in mandatory food fortification. Previous research has found that folic acid fortification of food provided a 19% reduction in neural tube defects, yet research reported in What's Hot on March 12 2001 showed that the amounts typically received when consuming a fortified diet are not enough to lower homocysteine to an optimal level. Vitamin B12, which is necessary along with folate to remethylate homocysteine to methionine, had been shown to be less important than folate in determining serum homocysteine levels. However, these results may have been due to a masking effect by folic acid.
The Irish researchers conducted two experiments to determine the relationship of the vitamins to homocysteine levels. In the first study, thirty men with normal folate and vitamin B12 levels were given folic acid in doses that increased from 100 to 400 micrograms over a twenty-six week period. The second experiment gave 23 women 500 micrograms folic acid per day for the same period. At both experiments' onset a strong inverse correlation was noted between plasma homocysteine and folate levels. Although homocysteine levels fell as serum folate levels rose, analysis of the data showed that vitamin B12 levels, which remained relatively unchanged in the participants during the course of the study, were a more important determinant of homocysteine levels than folate during the supplementation period. The association was reversed ten weeks following this period.
These results imply that folic acid supplementation causes a change in the dependency of homocysteine levels on folate to B12. The researchers suggest that food fortification would be much more effective at lowering homocysteine levels if vitamin B12 were added.
January 18, 2002
Diabetic mice regenerate insulin-producing cells
In research conducted at Harvard Medical School, mice with type 1 diabetes whose underlying diabetes was successfully treated were found to have regenerated the islet cells of the pancreas. In this form of the disease, the islet cells that produce insulin are destroyed in an autoimmune attack by the body. Transplanted islet cells have had limited success because the underlying disease goes on to destroy the new cells. The researchers, led by American Diabetes Association professional member, Dr Denise Faustman, taught the immune system cells of mice not to attack the islet cells, and then destroyed the immune cells existing in the pancreas, thereby halting the progression of the disease. New islet cells were subsequently transplanted into the mice. This combination appeared to have successfully treated the disease. Because the researchers wished to later remove the transplanted cells, it was not possible to transplant them into the pancreas, so the cells were placed into a kidney where they performed the same insulin-secreting function they would normally perform in the pancreas. To prove that the animals' diabetes would return upon removal of the islet cells, the kidneys containing the cells were then excised. To the researchers' surprise, the mice continued to make their own insulin and appeared to be free of the disease. It was found that the animals' pancreases had formed new insulin-making islet cells in the absence of the destructive autoimmune process.
The researchers do not yet know if the new islet cells arose from the animals' pancreas or from immature cells elsewhere in the body. This discovery, if replicable in humans, may mean that islet cell transplants will not be necessary if science can apply the knowledge of how to train the immune systems of type 1 diabetics not to attack pancreatic islet cells.
January 16, 2002
Folic acid deficient mice develop Parkinson's symptoms
The incidence of Parkinson's disease increases with age. Symptoms of the disease include tremor or trembling, slowness of movement, rigidity of the limbs and trunk, and impaired balance and coordination. Individuals with Parkinson's disease have been shown to have low levels of serum folic acid, and studies with mice have led researchers to believe that a deficiency in the vitamin may render the brain more susceptible to the disease. In a study conducted by researchers at the National Institute on Aging, folic acid protected mice from the development of Parkinson-like symptoms when given MPTP, a drug known to produce these symptoms. The research, published in the January 2002 issue of Journal of Neurochemistry, involved the administration of MPTP to mice whose diets included folate and to mice whose diets were deficient. The deficient mice developed elevated homocysteine levels in the brain and serum, inducing DNA damage to dopamine-producing cells in the substantia nigra. This leads to cell death in this region of the brain, causing the disordered movements characteristic of Parkinson's disease. Mice who received adequate levels of folate are more able to repair DNA damage, and therefore demonstrated only mild Parkinson's symptoms when administered MPTP.
National Institute of Aging Laboratory of Neurosciences chief, Mark Mattson PhD, commented, "This is the first direct evidence that folic acid may have a key role in protecting adult nerve cells against age-related disease. It is clear from this study that a deficiency of this vitamin is associated with increased toxin-induced damage to the dopamine-producing neurons in the mouse brain."
Dr Mattson suggests that ensuring an adequate intake of folic acid by dietary means or by consuming supplements could help to protect the brain from Parkinson's and other neurodegenerative diseases.
January 14, 2002
Vitamin E prevents ataxia in mouse model
In a report published in the December 18 2001 issue of the Proceedings of the National Academy of Sciences, Japanese researchers succeeded in creating a strain of mice lacking the gene for alpha-tocopherol transfer protein, which maintains the concentration of the vitamin in the body by enabling its transport from the liver. When this mouse model was deprived of dietary vitamin E, a movement disorder known as ataxia as well as retinal degeneration developed after approximately one year, caused by the oxidative stress that occurs in the absence of the antioxidant protection that vitamins such as vitamin E confer. However, supplementation with vitamin E almost completely corrected the abnormalities found in this mouse model of human degenerative disease.
The mice were bred to develop a disease called ataxia with isolated vitamin E deficiency or AVED, symptoms of which are often indistinguishable from Friedreich ataxia, the most common ataxia found in the western world. Groups of mice with and without the mutation were fed a normal diet containing 36 milligrams alpha-tocopherol per kilogram body weight, a diet enhanced to contain 600 milligrams alpha-tocopherol per kilogram, or a diet deficient in the vitamin. At one year of age, the mice with the mutation who were on the normal and vitamin E deficient diets showed movement difficulties that worsened over the following months. When the deficient mice, whose symptoms were more severe, were supplemented with alpha-tocopherol, the disabilities improved.
Postmortem examination of the animals showed a correlation between undectable levels of vitamin E in mice lacking the alpha-tocopherol transfer protein gene and the development of ataxia. When lipid peroxidation in the brain was measured, it was found to be markedly increased in the mutant mice, and improved in those who were supplemented with vitamin E. This confirms that oxidation caused by a lack of vitamin E results in the degeneration of neurons. This animal model may prove useful in investigating other age-related neurological disorders such as Alzheimer's disease.
January 11, 2002
Vitamin C helps drugs cross blood brain barrier
In an article scheduled to appear in the January 31 2002 issue of the Journal of Medicinal Chemistry, researchers in Milan, Italy report that the addition of a vitamin C molecule to drugs used to treat Alzheimer's disease and epilepsy enabled the drugs to more readily enter the brain. One of the challenges in targeting a drug to this organ is the blood brain barrier, which selectively filters the substances seeking entry. A newly discovered blood brain barrier cell receptor, the SVCT2 transporter, has been found to be involved in regulating the transport of vitamin C into the brain, which contains high levels of the vitamin. The researchers believe that adding vitamin C to a substance will more readily facilitate its passage into the brain, via the SVCT2 transporter.
The researchers tested three drugs, nipecotic acid, kynurenic acid and diclofenamic acid, using retinal pigment cells which also contain the SVCT2 transporter, which enabled the researchers to predict whether the drugs would be able to gain blood brain barrier entry. The addition of vitamin C to each of the drug caused the compounds to successfully interact with the transporter. The enhanced nipecotic acid was then tested on mice in which convulsions had been induced. While nipecotic alone had no effect, the addition of vitamin C delayed the convulsions. The animals experienced no deaths and minimal side effects.
Research team leader Professor Stefano Manfredini, of the Department of Pharmaceutical Chemistry at the University of Ferrara in Ferrara, Italy stated, "We've opened a door for a promising new way to improve delivery of drugs into the brain using a natural nutrient, ascorbic acid."
The scientists believe that this research will reveal some of vitamin C's mechanisms of action in the body.
January 09, 2002
Low B vitamin levels linked with cervical dysplasia
In a study conducted by the Cancer Research Center of Hawaii in Honolulu, published in the December 2001 issue of the journal Cancer Epidemiology, Biomarkers & Prevention, researchers discovered an inverse relationship of dietary intake of vitamin B6, vitamin B12 and folate with the incidence of squamous intraepithelial lesions, which can lead to cervical cancer. It was also discovered that a mutation of the gene responsible for the expression of methylenetetrahydrofolate reductase increases the odds of the development of these lesions. The enzyme is necessary for the synthesis of 5-methyltetrahydrofolate which helps methylate homocysteine to methionine, and mutations of the gene necessary for its expression cause variant forms of the enzyme.
The investigators collected blood and cervical cell samples from 150 women whose pap smears had revealed squamous intraepithelial lesions and 179 women with normal pap smears. The blood samples were analyzed for the presence of mutations in the methylenetetrahydrofolate reductase gene, and cervical samples were studied for human papillomavirus, a known risk factor for cervical dysplasia. Participants were interviewed in regard to reproductive history, diet including supplements for the previous year, tobacco and alcohol use and other lifestyle information. A food composition database was used to daily nutrient intake.
A positive correlation was observed between incidence of cervical squamous intraepithelial lesions and variants in the methylenetetrahydrofolate reductase gene. Women who took folic acid supplements experienced a significantly lower risk of the abnormal lesions. Dietary intake of folate, B6 and B12 were also associated with lowered risk. Women who reported consuming low amounts of folate and who had one variant of the gene had a five times greater risk than women with high folate intakes without the mutation. This provides evidence that lowered methylation of the cervical epithelium may play a role in the development of cervical cancer.
January 07, 2002
Folic acid improves heart endothelial function
Folic acid is known for its ability to lower homocysteine, which, when elevated, is a significant risk factor for coronary artery disease. However, a recent study published in the January 1, 2002 issue of the journal, Circulation, has uncovered the fact folic acid can improve endothelial function in coronary artery disease by a mechanism other than that of lowering levels of this potentially dangerous substance. Dysfunction of the endothelium of the blood vessels is part of the atherosclerotic process and is considered a predictor of cardiovascular events.
Researchers from the University of Wales College of Medicine, in Cardiff, Wales, randomized thirty-three patients diagnosed with coronary artery disease to received five milligrams folic acid per day or a placebo, for a period of six weeks. Flow-mediated dilatation was used to assess endothelial function two and four hours subsequent to the initial dose of folic acid and at the study's conclusion. Folic acid levels were found to be elevated one hour after the initial dose of the vitamin was administered and remained elevated for the course of the study in the group receiving the vitamin. Homocysteine levels did not significantly differ between the groups at four hours, although both groups experienced an initial decline, previously documented as attributable to postural changes in the subjects. While endothelial function in the folate group showed improvement at two and four hours, no improvement in endothelial function was observed in those receiving the placebo. At six weeks, homocysteine was significantly lower in the group receiving folic acid, but only a slight further improvement in endothelial function occurred.
This study points to the probability that most of the enhanced endothelial function seen with folic acid supplementation is caused by a direct action of folic acid rather than a reduction in homocysteine. The authors stress that the levels of plasma folate achieved in this study cannot be met by fortified dietary intake or by taking the commonly available 400 microgram folic acid supplements.
January 04, 2002
Tumor suppressor gene may play role in aging
The p53 tumor suppressor gene, which expresses a protein that induces apoptosis (programmed cell death), cell cycle arrest, or cellular senescence, is activated in response to DNA damage, low oxygen conditions and oncogene activation. Contrary to what might be expected, in findings published in the January 3 2002 issue of Nature www.nature.com, researchers discovered that mice genetically engineered to have activated p53 and who resultingly possessed enhanced tumor resistance, experienced early signs of aging, such as organ atrophy, osteoporosis, diminished ability to tolerate stress and a reduction in lifespan compared to littermates without the mutation. A second group of mice containing a temperature-sensitive p53 mutation were observed to experience early aging as well.
The mutant mice were monitored for tumors throughout their lifespan, and none were found to have developed any that were life-threatening, compared to over 45% of littermates without the mutation who developed large tumors including lymphomas, carcinomas, osteosarcomas and soft tissue sarcomas. Median lifespan for the mutant group was 96 weeks and maximum lifespan 136 weeks compared to 118 weeks median lifespan and 164 weeks maximum lifespan for those without the mutation. The researchers reported that the cause of death in the mutant group was difficult to determine, with examination failing to reveal obvious genetically based-disease. Postmortem examinations of the mutant group revealed reductions in body mass, fat tissue, and muscle, and spinal abnormalities. Spleen, liver, kidney and testes were also smaller, containing fewer cells. In experiments with wound healing, the mutant mice showed a signficiant delay in wound closure, and demonstrated other signs of lowered ability to tolerate stress.
The researchers conclude that p53 has a role in the regulation of aging and longevity in mice, and reaffirm that senescence is a mechanism of tumor suppression. Because a reduction in the proliferation of stem cells may occur earlier in the mutant mice due to their stem cells undergoing senescence sooner, this reduction in stem cell proliferation may play an important role in longevity.
January 02, 2002
Apoptotic response declines with age
In a letter published in the January 2002 issue of Nature Medicine, researchers from Seoul, Korea and the United States reported the results of a study that showed that apoptosis is dramatically reduced in the livers of old rats. Apoptosis, or programmed cell death, is necessary to maintain the fidelity of the genome. An inadequate apoptotic response can lead to an accumulation of genetic errors, and may be responsible for the link between the elevated incidence of cancer with age.
The researchers treated two month old and twenty-six month old female rats with methyl methanesulfonate, a genotoxic agent, and examined their livers for the presence of apoptotic cells after one hour and at two hours. In the younger rats, over 700 out of 100,000 cells were observed to be apoptotic after one hour, which increased to 1,300 after two hours. The older rats however were found to have only 200 apoptotic cells after one hour, which did not change at two hours.
These results showed that the livers of old rats are more resistent to apoptosis in response to a moderate dose of a genotoxin, compared to young rats. The researchers speculate that this may be the cause of the increase in liver cancer observed in old rodents as well as the rise in DNA damage that occurs with with age. They make note of the fact that previous studies showed that calorie restricted animals, who experience increased lifespan, also experience increased levels of spontanous apoptosis in the liver. They conclude that improved understanding of the mechanism controlling the decline of apoptotic response in aging may reveal new targets for interventions that could help prevent cancer in older individuals.
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