Friday, July 10, 2009

Antibiotic 'boosts lifespan' (in mice)

But the side-effects could be severe. Fancy a suppressed immune system or feeling hungry all the time?

A COMPOUND found in the soil of Easter Island stunningly boosts the lifespan of mice, enabling some to live more than 100 years old in human terms, researchers reported today. The remarkable molecule, a bacterial byproduct discovered in a sample taken from the remote Pacific archipelago in the 1970s, is called rapamycin, after the island's Polynesian name of Rapa Nui.

Rapamycin first came to light because of its qualities as a fungus fighter. It was later used to prevent organ rejection in transplant patients and then became incorporated into "stents" - implants used to keep arteries open in patients with coronary disease. It is now in clinical trials for cancer treatment.

The latest step in this remarkable odyssey is the vision that rapamycin, or something like it, may one day massively boost human life expectancy. "I've been in ageing research for 35 years and there have been many so-called anti-ageing interventions over those years that were never successful," said Arlan Richardson, director of the Barshop Institute, one of three centres that carried out the experiments. "I never thought we could find an anti-ageing pill for people in my lifetime. However, rapamycin shows a great deal of promise to do just that."

Intrigued by findings that suggest rampamycin inhibits an enzyme linked to ageing in invertebrates, the researchers decided to add the drug to the diet of older mice. The rodents were 20 months old at the time, which in human terms is equivalent to around 60 years of age. Female mice with rapamycin added to their food lived 13 per cent longer on average compared with non-rapamycin counterparts. Males which were fed the drug gained nine per cent in their lifetime. The change was even more striking among the 10 per cent of mice that lived longest. Within this group, rapamycin females lived 38 per cent longer and rapamycin males 28 per cent longer than non-rapamycin counterparts.

Rapamycin may retard ageing processes or the onset of cancer but has no impact on the causes of death itself, the study said.

The project, reported in the British science journal Nature, is part of a test program under the US National Institute on Ageing (NIA), which is looking for drugs that will help people remain healthy and active throughout their lives. Previous work on rapamycin longevity was carried out on yeast, worms and flies. This study is the first to show it also appears to work on mammals.

Scientists have already found that by keeping mice skinny by restricting their diet, they could make the rodents live longer. The theory behind rapamycin is that it works on the same molecular mechanisms as calorie restriction.

Initially, the US researchers hoped to start giving rapamycin to mice from four months of age. But the project was hit by delays in formulating the drug so that it could enter the specially-bred animals' bloodstream more effectively. As a result, the experiment was not started until the mice were 20 months old, but the team decided to press ahead anyway.

"Most reports indicate that calorie restriction doesn't work when implemented in old animals," said Mr Richardson. "The fact that rapamycin increases lifespan in relatively old mice was totally unexpected."

In a commentary also published by Nature, University of Washington biocehmists Matt Kaeberlein and Brian Kennedy cautioned middle-aged people against rushing to take rapamycin, given that the drug is known to suppress the immune system, which fights invading microbes. Despite the rush of optimism sparked by rapamycin, "extending human lifespan with a pill remains the purview of science-fiction writers for now", they said.


Working mothers have fatter kids, paper finds

At last! An "obesity" writer who is realistic about social class effects

CHILDREN of many full-time working mothers are up to 12 per cent more likely to be overweight than the kids of stay-at-home mums. But the link between a mother's paid work and her kids' waist lines is only found in families at the lower end of the socioeconomic spectrum.

In a paper to be presented today to the Australian Social Policy Conference in Sydney, economic researcher Anna Zhu finds children in families earning less than $1000 a week with a full-time working mother are most at risk of being overweight. "The main reason is that to maintain a healthy lifestyle requires time and/or money," Ms Zhu told The Australian. "Indeed, it could just be money because we don't find the effect in high-income families."

Ms Zhu, from the University of NSW's Social Policy Research Centre, said stay-at-home mothers had the time to prepare meals and richer full-time working mothers could outsource the preparation of healthier food to a nanny or carer, but poorer mothers working long hours had fewer options. "These mothers are constrained for time (so they resort to) things like pre-packaged food. And without the income, they turn to cheaper options that have higher calorific value."

The rate of mothers joining the labour force and with a youngest child aged less than five years old rose from 36 to 43 per cent between 1986 and 2000, according to the Australian Bureau of Statistics. Over a similar period, the prevalence of overweight children almost doubled, and the prevalence of obese children tripled.

While Ms Zhu's study focused on 4 to 5-year olds, she said similar research conducted overseas produced the same outcome for children of all ages. She warned the results should not be interpreted as support for the view that mothers shouldn't work. "There are an array of other benefits of the mother working," she said. "This study is more presenting the reality that full-time working mothers face significant time constraints, and a lack of money limits their options to provide their children with a healthy lifestyle."

The other factor determining a child's chances of being overweight was the amount of exercise they did. "Families with low incomes won't be able to afford to pay people to take them to outdoor activities while they work," Ms Zhu said. "Instead the kids are more likely to be at home watching TV. If the full-time working mum isn't earning enough to hire a nanny to take them to the park, the mum is probably happier for them to be indoors because they feel they are safer there."

Ms Zhu said governments should be looking at policy options to provide greater support for working mothers. She said for low-income families, a full-time working father had a beneficial impact on a child's propensity to be overweight because the extra income for the family means better nutrition and a healthier lifestyle.


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