Study Links Mitochondrial Function to Fatigue in Cancer Survivors

A pilot study, published in Biomedicines, has utilized a non-invasive MRI technique to investigate the connection between muscle cell energy production and persistent fatigue in cancer survivors.

The research suggests that slower recovery of muscle energy after exercise is linked to higher fatigue and reduced physical function in survivors, particularly in older adults and those who received immunotherapy.

The Method: Measuring Muscle Energy in Real Time

The study employed phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS), an NIH-validated MRI test, to measure mitochondrial function directly in skeletal muscle cells. Mitochondria are the power plants of cells, and their efficiency is crucial for energy production.

Researchers measured how quickly mitochondria rebuilt energy reserves in the quadriceps muscle after a brief session of knee extension exercises. The study involved 11 cancer survivors, aged 34–70, who had completed treatment for various cancers.

Key Findings

Age-Related Differences:

• Participants aged 65 and older showed approximately 10% slower muscle energy recovery than younger participants.
• This slower recovery was accompanied by weaker grip strength, higher self-reported fatigue, and fewer daily steps.

Impact of Treatment:

• While most participants had received multiple therapies, the type of cancer treatment predicted muscle recovery to some extent.
• Participants who had received immunotherapy reported more fatigue, had slower muscle recovery, weaker grip strength, and fewer daily steps than those who had not.

A Notable Anomaly:

• Among younger participants, those with worse mitochondrial recovery unexpectedly reported less fatigue and showed higher resilience. Researchers noted this counterintuitive finding could reflect statistical instability due to the study's small sample size.

Context and Limitations

Senior author Leorey Saligan highlighted that previous research often measured mitochondrial markers in blood, which is less stable. "This study demonstrates the feasibility of using ³¹P-MRS as a noninvasive measure of mitochondrial function," Saligan stated.

The authors acknowledge several limitations, including the small sample size and the mix of different cancer types and treatments among participants, which makes drawing broad conclusions difficult.

Next Steps for Research

Saligan said the immediate next step is to replicate the work with larger, more defined cohorts to confirm the findings.

A further goal would be to measure energy recovery in the brain and skeletal muscle simultaneously, providing a more complete picture of a survivor's fatigue.

Saligan stated this approach could eventually help clinicians with exercise dosing and timing exercise programs to better support recovery and quality of life for cancer survivors.