Amount of mitochondrial DNA predicts frailty, mortality in humans

December 17, 2014

Mitochondrial DNA from the snake adrenal gland, where the mitochondrion is adjacent to a highly ordered array of endoplasmic reticulum (bottom left). Credit: John Long

Chuck Bednar for redOrbit.com Your Universe Online

The amount of mitochondrial DNA (mtDNA) found in a persons blood could be used to predict his or her overall risk of frailty and death from any cause 10 to 15 years before the first symptoms appear, researchers from The Johns Hopkins University say in a new study.

Mitochondrial DNA, the cellular organelles that help convert food into chemical energy for cells, can be used to enhance our scientific understanding of aging, the study authors explained. Their findings, which were published online earlier this month in the Journal of Molecular Medicine, could be used to develop a new test to identify at-risk individuals.

Dr. Dan Arking, an associate professor of genetic medicine at the university, said that he and his colleagues dont know enough yet to say whether the relationship is one of correlation or causation, but either way, mitochondrial DNA could be a very useful biomarker in the field of aging. It could be used to identify people who could benefit health-wise from lifestyle changes.

Unlike other cell structures, mitochondria (which are also known as power houses since they are responsible for generating the majority of a cells energy) contain their own DNA separate from those enclosed in the nucleus. Their DNA comes in the form of between two and 10 small, circular chromosomes which code for 37 genes necessary for mitochondrial function.

Previous research from Dr. Arkings laboratory has found a link between genetic differences in mtDNA and the reduced muscle strength and increased frailty experienced by older men and women. In medical terms, frailty refers to a highly recognizable set of aging symptoms, including weakness, decreased energy, reduced activity and weight loss, the study authors added.

In order to further study this correlation, the investigative team analyzed the amount of mtDNA in blood samples collected for a pair of large studies that began during the late 1980s. They monitored the health of individuals for up to 20 years and calculated the amount of mtDNA each sampled contained relative to the amount of nuclear DNA.

Dr. Arking and his colleagues then reviewed measures of frailty and health status gathered on the studies participants over time. They found that, on average, study participants that met the criteria for frailty had nine percent less mtDNA than nonfrail participants. Furthermore, white participants in the bottom one-fifth of the study population in terms of mtDNA were 31 percent more likely to be clinically frail than participants in the top one-fifth.

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Amount of mitochondrial DNA predicts frailty, mortality in humans