http://story.news.yahoo.com/news?tmpl=story2&cid=571&ncid=751&e=10&u=/nm/2
0021224/hl_nm/climate_calories_dc
Native Climate May Influence How Body Burns Energy
Mon Dec 23, 9:02 PM ET Add to My Yahoo!
NEW YORK (Reuters Health) - A person's native climate might influence how
his or her body goes about burning calories, according to a study
published Monday.
People whose ancestors hail from chilly regions have gene adaptations
that may allow their bodies to produce more heat while burning calories,
an international team of researchers reports, while those with roots in
warmer climates use calories more efficiently and produce scant excess
heat.
Mitochondria, found in every cell, are responsible for producing energy
and play a key role in regulating metabolism. The DNA in mitochondria is
inherited maternally, and shows "striking differences" from one
geographic region to another, Douglas C. Wallace from the University of
California at Irvine and colleagues note. To investigate whether
adaptation to different climates might explain this variation, the
researchers analyzed gene sequences from the mitochondria of 104 people
who represented all the known major types of mitochondrial DNA.
In the Proceedings of the National Academy of Sciences ( - ) paper,
Wallace and his team report that mitochondrial gene variants may confer
advantages in some climates, but disadvantages in others.
For instance, arctic and sub-arctic native peoples had variants that
programmed them to produce more heat, but put out less energy. Their
bodies were thus more efficient at keeping them warm. Previous studies
have shown that indigenous populations around the North and South Poles
tend to have a higher resting metabolism.
Tropical and sub-tropical natives made more efficient use of energy,
producing little heat.
The authors say the variants are evidence of natural selection at
work--that genes evolved in response to environmental stresses.
But this adaptive response might not be beneficial when people native to
one climate relocate to another climate, the authors say. "Given that
mitochondrial DNA lineages are functionally different, it follows that
the same variants that are advantageous in one climatic and dietary
environment might be maladaptive when these individuals are placed in a
different environment," they write.
Natives of cold regions are used to stoking their bodies with
heat-producing high-calorie meals. That dietary habit might not serve
them well if they move to a warmer region, and may play a role in causing
disease, the authors say.
"Ancient regionally beneficial mitochondrial DNA variants could be
contributing to modern bioenergetic disorders such as obesity, diabetes,
hypertension, cardiovascular disease, and neurodegenerative diseases as
people move to new regions and adopt new lifestyles," they write.
SOURCE: Proceedings of the National Academy of Sciences
_______________________________________________
http://www.mccmedia.com/mailman/listinfo/brin-l
