X-Message-Number: 24207
Date: Mon, 7 Jun 2004 13:56:16 -0700
Subject: High metabolic rate gives mice a longer life 
From: Kennita Watson <>

Interesting, though somewhat counterintuitive...
Kennita

Nature Online, 2 June 2004
HELEN PEARSON

Long lived mice may have more efficient mitochondria.

Mice with sky-high metabolic rates live far longer than their sluggish 
cousins, UK researchers have found, raising the prospect that human 
lifespan might be lengthened with metabolism-boosting drugs.

Metabolic rate is the pace at which the body burns food to produce 
energy. John Speakman of the University of Aberdeen, UK, and his 
colleagues measured the metabolism of 42 mice, based on the amount of 
oxygen they consumed, and then waited until they died.

The group of animals with the highest metabolic rates lived over a 
third longer than the group with the lowest rates, they found, and had 
metabolisms that ran about 30% faster. If the same is true in humans, 
this means that people with a speedy metabolism might add an extra 27 
years onto a typical 70-year lifespan.

The finding challenges a century-old theory that animals with higher 
metabolic rates die younger. This is based on observations that big 
animals with low metabolic rates, such as elephants, tend to outlive 
small, high metabolism ones, such as mice: hence the old adage, "live 
fast, die young."

While this overall trend may be true when comparing different species, 
the new study suggests it may be reversed for animals within one 
species. "It was a complete surprise," says Speakman.

More efficient cells

The secret to longevity may lie inside mitochondria, the powerhouses of 
the cell that help to set the metabolic rate. Mitochondria use oxygen 
to 'burn' food molecules to produce chemical fuel that is used by the 
cell   but in the process they generate harmful free radicals that 
damage other molecules and are linked to ageing.

Speakman's team found evidence that mice with a high metabolic rate 
have more vigorous 'uncoupling proteins', which cause the mitochondria 
to generate heat instead of producing fuel. Since more of their energy 
escapes as heat, the mitochondria have to run at full speed in order to 
keep generating enough chemical fuel for the cell.

At the same time, the mitochondria may run more efficiently and release 
fewer harmful free radicals, hence slowing the ageing process. "That's 
when they run the cleanest," explains Wayne Van Voorhies, who studies 
ageing at New Mexico State University, Las Cruces.

Speakman now plans to test if a higher metabolic rate can prolong human 
life, but he cautions that a quick fix to ageing is unlikely to be just 
around the corner. Although drugs such as amphetamines are known to 
speed up metabolism, Speakman says that they may not simultaneously 
increase the activity of uncoupling proteins, the key to cutting 
free-radical production and thus potentially prolonging life.

Indeed, finding drugs that really do boost uncoupling proteins may be 
difficult, warns Van Voorhies. "You're really messing with some 
fundamental characteristics of [the cell]," he says.
References

    1. Speakman, J.R. et al. Aging Cell, 3, 87, (2004). |Article|

  Nature News Service / Macmillan Magazines Ltd 2003

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