New research from The Johns Hopkins University suggests that the amount of mitochondrial DNA (mtDNA) found in peoples' blood directly relates to how frail they are medically. This DNA may prove to be a useful predictor of overall risk of frailty and death from any cause 10 to 15 years before symptoms appear. The investigators say their findings contribute to the scientific understanding of aging and may lead to a test that could help identify at-risk individuals whose physical fitness can be improved with drugs or lifestyle changes. A summary of the research was published online on December 4, 2014 in the Journal of Molecular Medicine. "We don't know enough yet to say whether the relationship is one of correlation or causation," says Dan Arking, Ph.D., associate professor of genetic medicine at Hopkins. "But either way, mitochondrial DNA could be a very useful biomarker in the field of aging." Mitochondria are structures within cells often referred to as "power houses" because they generate most of cells' energy. Unlike other cell structures, they contain their own DNA -- separate from that enclosed in the nucleus -- in the form of two to 10 small, circular chromosomes that code for 37 genes necessary for mitochondrial function. There are also genes important for mitochondrial function coded for by DNA in the cell nucleus. There are 10 to thousands of mitochondria per cell, depending on a cell's energy needs. Previous research from Dr. Arking's laboratory linked genetic differences in mtDNA to increased frailty and reduced muscle strength in older individuals. Medically speaking, frailty refers to a well-recognized collection of aging symptoms that include weakness, decreased energy, lower activity levels, and weight loss. To further test this link, Dr.
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