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Oxidative Stress Extends Lifespan

Scientists at the University of California, San Diego claim to have identified a mechanism of oxidative stress that prevents cellular  damage.

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“We may drink pomegranate juice to protect our bodies from so-called ‘free radicals‘ or look at restricting calorie intake to extend our lifespan,” said Dr Trey Ideker, chief of the Division of Genetics in the Department of Medicine at UC San Diego’s School of Medicine and professor of bioengineering at the Jacobs School of Engineering.

“But our study suggests why humans may actually be able to prolong the aging process by regularly exposing our bodies to minimal amounts of oxidants,” Ideker added.

Reactive oxygen species (ROS), ions that form as a natural byproduct of the metabolism of oxygen, play important roles in cell signalling. However, due to environmental stress like ultraviolet radiation or heat or chemical exposure the ROS levels can increase dramatically, resulting insignificant damage to cellular damage to DNA, RNA and proteins, cumulating in an effect called oxidative stress.

The scientists claim to have discovered the gene responsible for this effect.

One major contributor to oxidative stress is hydrogen peroxide. While the cell has ways to help minimize the damaging effects of hydrogen peroxide by converting it to oxygen and water, this conversion isn’t 100 percent successful.

During the study, the researchers designed a way to identify genes involved in adaptation to hydrogen peroxide.

To figure out which genes might control this adaptation mechanism, the team ran a series of experiments in which cells were forced to adapt while each gene in the genome was removed, one by one, covering a total of nearly 5,000 genes.

They identified a novel factor called Mga2, which is essential for adaptation.

“This was a surprise, because Mga2 is found at the control point of a completely different pathway than those which respond to acute exposure of oxidative agents,” said Ideker.

“This second pathway is only active at lower doses of oxidation,” Ideker added.

“It may be that adaptation to oxidative stress is the main factor responsible for the lifespan-expanding effects of caloric restriction,” said Ideker.

“Our next step is to figure out how Mga2 works to create a separate pathway, to discover the upstream mechanism that senses low doses of oxidation and triggers a protective mechanism downstream.”

Click to see : Extend Your Life By Eating Right

Sources: :The study is published in PLoS Genetics.

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Vitamin E, C Supplements Reduce Exercise Benefits

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A new study suggests that some vitamin supplements may reduce some of the beneficial effects of exercise.

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Michael Ristow, of the University of Jena in Germany, has shown that antioxidant supplements like vitamin C or E can interfere with the benefits of exercising.

Previous studies have also revealed that taking antioxidants may hasten death through an unknown mechanism.

One possibility, according to the researcher, is that they interfere with the beneficial effects of exercise, as there are hints that free radicals might be used by the body to prevent cellular damage after exercise.

During the study, the researchers recruited 40 volunteers. Half of them were asked to take 1000 milligrams of vitamin C and 400 international units of vitamin E per day – equivalent to amounts in some vitamin supplements.

The volunteers were also asked to exercise for 85 minutes a day, five days a week, for four weeks.

The researchers found that muscle biopsies showed a two-fold increase in a marker of free radicals called TBARS (thiobarbituric acid-reactive substances) in those volunteers who didn’t take antioxidants

However, they found no increase in those who did take the supplements – suggesting that they were indeed mopping them up.

Ristow pointed out that exercise is well known to have a beneficial effect on insulin resistance – a precursor condition to type 2 diabetes.

However, when the team measured the effects of exercise on insulin sensitivity, they found no increase in those volunteers taking antioxidants, but a significant increase in those who didn’t take the supplements.

“These data are fully in accord with recent work on the actions of reactive oxygen species in cells, although clearly at odds with the popular concept that dietary antioxidants are inevitably beneficial,” New Scientist magazine quoted Malcolm Jackson at the University of Liverpool, UK, who was not involved in the research as saying.

In fact, in this case, “antioxidants are preventing the health effects of exercise,” said Ristow,

He, however, cautions that not all vitamin supplements contain such high doses of vitamin C and E.

The study appears in Proceedings of the National Academy of Sciences.

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If Tea is Hot, Wait Four Minutes

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Drinking very hot tea appears to increase the risk of oesophageal cancer, a new study has shown, prompting suggestions for a four-minute wait before swallows of freshly boiled tea.

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The study from northern Iran, the largest so far to explore tea-drinking habits and oesophageal cancer, has corroborated earlier research from India, Singapore and South America that linked this cancer to hot beverages.

Researchers from the Tehran University of Medical Sciences studied tea-drinking habits and patterns of oesophageal cancer in Golestan province where black tea is popular. They found that people who consumed very hot tea (defined as 70°C or higher) had an eight-fold higher risk of oesophageal cancer than people who drank tepid tea (65°C or lower).

They found that drinking tea at temperatures between 65°C and 69°C — defined as simply hot — was associated with twice the risk of cancer of the oesophagus. Their research will appear in the British Medical Journal on Friday.

“It’s clear hot beverages are contributing to high levels of oesophageal cancer in this population, Paul Brennan, a research team member from the International Agency for Research in Cancer in Lyons, France, told The Telegraph.

“But other factors may be associated with oesophageal cancer in other populations,” said Brennan, head of genetic epidemiology unit at the IARC. “We need to investigate different factors in different regions or populations.”

The Iranian study also showed that waiting for tea to cool lowered the risk of the cancer. People who typically drank their tea within two minutes after it was poured had a five-fold higher risk than those who waited for four minutes or longer.

Although previous studies have pointed to the potential danger of hot beverages, Iranian digestive disorder specialist Reza Malekzadeh and his colleagues are among the first to investigate the link through rigorous temperature measurements.

Malekzadeh said the significance of the new research was in the use of statistical techniques to eliminate the effects of other risk factors that could also contribute to oesophageal cancer.

But doctors assert that there is no cause for alarm. “The public health message here is that people should wait four minutes before they begin sipping from a cup of hot tea,” Malekzadeh told The Telegraph.

Eight years ago, Rup Kumar Phukan and his colleagues at the Regional Medical Research Centre, Dibrugarh, Assam, had examined dietary habits in parts of northeastern India and shown that hot beverages and spicy food were linked to oesophageal cancer.

They had suggested that the long-term consumption of exceptionally hot food or beverages could cause chronic irritation and harm the lining of the oesophagus. “But chewing tobacco and smoking are also likely to be among the contributing factors in this region,” said a scientist at the Dibrugarh centre.

The Iranian study measured tea temperatures consumed by more than 48,500 people and studied tea-drinking habits of 300 patients with oesophageal cancer and 571 healthy people, emerging as the largest study on the topic.

Speculating on mechanisms to explain the link, the researchers have pointed out that chronic inflammation by high temperatures may stimulate the release of nitric oxide and reactive oxygen species — potentially harmful biomolecules.

Doctors caution that cancer is almost always a multi-factorial disease. The risk may be lowered or increased by several factors. Low consumption of fruits and vegetables, for instance, may increase the risk of cancer.

You may click to see:->Steaming hot tea linked to cancer

Sources: The Telegraph (Kolkata, India)

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Broccoli May Undo Diabetes Damage

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Eating broccoli could reverse the damage caused by diabetes to heart blood vessels, research suggests.

A University of Warwick team believe the key is a compound found in the vegetable, called sulforaphane.

It encourages production of enzymes which protect the blood vessels, and a reduction in high levels of molecules which cause significant cell damage.

Brassica vegetables such as broccoli have previously been linked to a lower risk of heart attacks and strokes.

It encourages production of enzymes which protect the blood vessels, and a reduction in high levels of molecules which cause significant cell damage.

Brassica vegetables such as broccoli have previously been linked to a lower risk of heart attacks and strokes.

” Our study suggests that compounds such as sulforaphane from broccoli may help counter processes linked to the development of vascular disease in diabetes “…..Says Professor Paul Thornalley of University of Warwick.

People with diabetes are up to five times more likely to develop cardiovascular diseases such as heart attacks and strokes; both are linked to damaged blood vessels.

The Warwick team, whose work is reported in the journal Diabetes, tested the effects of sulforaphane on blood vessel cells damaged by high glucose levels (hyperglycaemia), which are associated with diabetes.

They recorded a 73% reduction of molecules in the body called Reactive Oxygen Species (ROS).

Hyperglycaemia can cause levels of ROS to increase three-fold and such high levels can damage human cells.

The researchers also found that sulforaphane activated a protein in the body called nrf2, which protects cells and tissues from damage by activating protective antioxidant and detoxifying enzymes.

Countering vascular disease

Lead researcher Professor Paul Thornalley said: “Our study suggests that compounds such as sulforaphane from broccoli may help counter processes linked to the development of vascular disease in diabetes.

“In future, it will be important to test if eating a diet rich in brassica vegetables has health benefits for diabetic patients. We expect that it will.”

Dr Iain Frame, director of research at the charity Diabetes UK, stressed that research carried out on cells in the lab was a long way from the real life situation.

However, he said: “It is encouraging to see that Professor Thornalley and his team have identified a potentially important substance that may protect and repair blood vessels from the damaging effects of diabetes.

“It also may help add some scientific weight to the argument that eating broccoli is good for you.”

Sources: BBC NEWS:5th. Aug.’08

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