Wednesday, June 20, 2007

A gene for deafness

A gene that contributes to one of the commonest causes of deafness has been identified for the first time, in a step towards improving diagnosis and treatment. People with otosclerosis, the most common reason for hearing loss among white adults, are more likely to carry a particular variant of a gene called TGBF1 than those who are unaffected, scientists in Belgium have discovered.

The findings, from a team based at the University of Antwerp, promise new insights into the origins and development of the condition, which usually begins in the twenties or thirties and affects about one in 250 people. In the long term, that could lead to new ways of preventing and treating otosclerosis, for which the best option today is usually an operation that is not always effective. One of the most attractive prospects would be to use the new genetic clue to design a drug that stops the progression of otosclerosis before it causes potentially irreversible tinnitus and hearing loss. Much more research is still needed to confirm the effect, to establish how it influences the disorder, and to develop a drug. Melissa Thys, who led the study team, said that it could be ten years before the results have an impact on medicine.

Otosclerosis is known to be affected by genetic and environmental factors. TGBF1 is the first gene to be conclusively linked to it. The find is especially promising because the gene is known to be involved in the embryonic development of the ear and influences a pathway that appears important to the progression of otosclerosis.

The condition involves abnormal bone growth in the middle ear, which impairs movement of the stapes or "stirrup" - the last of the three tiny bones that transmit sound to the inner ear. It generally causes tinnitus and the loss of hearing at lower frequencies.

Ms Thys, who presented the research to the European Society of Human Genetics conference in Nice yesterday, said: "The gene in which the variant is located points to a pathway that contributes to the disease. This may be a lead for better forms of treatment in the future. Currently the best option is an operation. However, there is often an additional component of hearing loss, which can't be restored by surgery. As the gene involved is a growth factor, and the disease manifests itself by the abnormal growth of bone in the middle ear, it may have a large potential for therapy."

In the study, Ms Thys's team compared 630 patients with otosclerosis with the same number of unaffected controls in Belgium and the Netherlands. They found that a protective variant of TGBF1 was carried by 7 per cent of healthy subjects, compared with only 2.5 per cent of the otosclerosis group. The data has been confirmed in a French group of 457 patients and 497 controls. Ms Thys said: "Combining the data from both groups with a common odds ratio gave a significant result, from which we were able to conclude that we were the first to identify a gene that influences the susceptibility for otosclerosis. And, as further evidence, we were also able to show that a more active variant of this gene is protective against the disease."

Catriona Crombie, of the Royal National Institute for Deaf People, welcomed the findings. "The discovery of this gene responsible for a common cause of hearing loss is a fantastic breakthrough," she said. "The effects of otosclerosis can be devastating - imagine the frustration of incessant ringing in your ears, or of being constantly asked to `speak up'. "Researchers can now focus their effort on this gene and the processes it controls to develop new ways of preventing and treating otosclerosis." "If a drug could be developed for this devastating condition, it could save many from repeated painful surgery. This study highlights the vital role genetic research can play in helping us understand the causes of many types of hearing loss, which could lead to ways of protecting and restoring hearing ."


Another oldster gives his recipe for long life

The fact that the recipes vary so much suggests that it is your genes rather than what you do or eat that matters. So eat what you like!

With Japan’s welfare system buckling under the demands of an ageing society, the world’s oldest man apologised yesterday for his longevity. As Tomoji Tanabe, 111, received his certificate from Guinness World Records, the former engineer, who never touches alcohol, said that his feat of survival was nothing special. “I have been around too long,” he joked, “I am sorry.”

Mr Tanabe added his customary explanation of how he has managed to reach such a ripe old age: “Not drinking alcohol is the best formula for keeping myself healthy,” he said. Other residents of his village attributed Mr Tanabe’s long life to a diet that consists chiefly of vegetables and very little fried food.

His explanation fuels a continuing mystery about the ideal formula for longevity – as each new holder of the title is crowned, each attributes his or her success to diets, lifestyles and habits that differ widely. Some have said that fresh air is the key, others have been heavy smokers. Some have taken vigorous exercise, others have sworn by periods of inactivity.

The Mayor of Miyakonojo, the village where Mr Tanabe lives with his family, presented the certificate to its famous resident after nearly five months of birthdate verification by the Guinness World Records team. Mr Tanabe unofficially inherited the title when its previous incumbent, Emiliano Mercado del Toro, of Puerto Rico, died in January, aged 115. The crowning of Mr Tanabe, who was born in the southern island of Kyushi in 1895, brings the coveted “double trophy” back to Japan. Yone Minagawa, who lives in the same prefecture, is 114 and holds the title of world’s oldest woman.

Japan’s population of centenarians is the largest in the world. Most of the 28,000 Japanese who have made it beyond 100 are women and the highest concentration of the very elderly is in the southern part of the archipelago. The area around Hiroshima and the island of Okinawa are especially rich in former “world’s oldest” title holders.

The number of centenarians has risen 160-fold since records began in the 1960s. Although Japan is proud of its record-breaking longevity, the success of Mr Tanabe comes as the country is running short of ideas for how to solve its ageing crisis. With the fertility rate still at record lows, government and private sector efforts to stimulate the birthrate have met with little success. As the number of children dwindles, the future welfare burden for working-age Japanese may become intolerably large.

The problem is already acute in the very rural areas where the likes of Mr Tanabe and Ms Yone have grown so old. The few children who are born in those regions move quickly to the big cities when they grow up, pushing the average age of some villages above 50.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.


1 comment:

Aaron Marks said...

Thank you for these articles. I'm a bit of a skeptic myself. But we'll see how this all goes.