19 August 2010

What can beetles tell us about slowing aging? Answers are in the mitochondria

Mitochondrial genes influence life expectancy in beetles, a new study reports.
Genetic research into aging and longevity revolves mainly around the nuclear genome, which encodes most of our multicellular bodies, but a new Monash University study performed on beetles suggests shifting focus to the mitochondrial genome.  

The mitochondria—kidney-shaped organelles often referred to as the cell's powerhouses—each contain their own set of DNA, passed on from mother to offspring, and according to the study, it's these strands that may hold key genes that determine one's life expectancy, at least in bugs.  

The study, published in the August issue of The American Naturalist, found evidence that particular combinations of genes (haplotypes) in the mitochondrial genome influenced lifespan in a species of seed beetles (Callosobruchus maculates).  

As a result, the research supports growing evidence that particular mitochondrial gene combinations could also play a major role in accelerating the aging process in humans because they could cause mitochondria to produce greater amounts of toxic molecules called free radicals causing oxidative damage to cells, cellular proteins and DNA.  

Evolutionary biologist Damian Dowling of Melbourne, who conducted the study, hopes his research will help medical scientists identify which gene combinations accelerate aging, as well as develop gene therapies that alter the combinations, or develop antioxidant therapies that neutralize free radicals and protect cells from oxidative damage. Do mothers show favoritism toward daughters?  

Although Dowling found his discovery interesting, he said it was not the original intent of his research; in fact, he was testing a debated theory that mitochondrial genes make an impact on the tug-of-war between the sexes in the beetles. Previous research in beetles and fruit flies has explored a ubiquitous phenomenon in insects commonly called the "cost of mating"—that is, that the simple act of sexual reproduction can take a toll on mothers, and sometimes fathers, by reducing their life expectancy.  

Dowling’s wanted to find out if mitochondria bestowed any reward to female beetles. He explained to me: "Because the mitochondrial genome is maternally inherited it has been hypothesized that it will take the female's best interests at heart." 

But, he adds, "Our study was the first experimental test of this idea, and we didn't support the controversial idea." However, what Dowling did find was something more exciting—that different mitochondrial gene combinations, sourced from different geographic locations from around the globe, produced large differences in life spans in the beetles.  

“Beetles that harbored certain mitochondrial DNA sequences could live up to 30 percent longer,” he told me. Thirty percent longer is about 20 more days for the life of a beetle, which is nothing short of a leap for the crawling critters—when scaled up to human years, it amounts to adding about 23 more years.

No comments: