Mitochondrial DNA Levels Tied to Outcome in Critically ill Patients

Increasing blood-cell levels of mitochondrial DNA (MtDNA) appear to be associated with short-term survival in critically ill patients, according to a new study.

Researchers at the University of British Columbia (Vancouver, Canada) prospectively studied mitochondrial DNA levels--and indication of mitochondrial function--in 28 hypotensive, mechanically ventilated, critically ill intensive care unit (ICU) patients.

The researchers found that at baseline, the ratio of mitochondrial to nuclear DNA was about 30% lower than that seen in 24 control subjects. By day four, the change in this ratio in survivors (+29.5%) was significantly greater than that seen in non-survivors (-5.7%). The change also tended to be higher in survivors at the last measurement than in non-survivors (38.4% versus 7.1%). The researchers suggest that the results hint that some mitochondrial shutdown may take place in humans during shock, providing corroborative evidence to observations obtained from animal models. The study was published in the August 15, 2007, issue of Critical Care.

"Blood mitochondrial DNA levels appeared initially low, increased over time in patients who ultimately survived, and remained low in those who did not,” said lead investigator Dr. Helene C. F. Cote. "The findings are consistent with mitochondrial dysfunction playing a role in shock, and open new research avenues.”

Mitochondrial DNA is located in the mitochondria, parts of the cell that generate fuel in the form of adenosine triphosphate (ATP), which drives the varied machinery of the cell. Because mitochondrial DNA is inherited only from the mother, it provides an unaltered link to past generations, serving as a genetic research tool.


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