Discover the biological relationship between pain and fatigue

A recent study by the University of Iowa found a biological link between pain and fatigue. This may help to understand why more and more people are diagnosed with chronic pain and fatigue such as fibromyalgia or chronic fatigue syndrome.

Researchers are led by Professor Dr. Kathleen Sluka and Lucille A. Carver. Sluka is professor of master's program in physical therapy and rehabilitation science at Pharmacy University UI Roy J. and Lucille A. Carver; and Carver of the University of Medicine. Research done on mice found a protein involved in muscle pain associated with male sex hormones testoterone to protect muscles from fatigue. .

Chronic pain and fatigue often occur concurrently - three out of four people with chronic musculoskeletal pain are accompanied by fatigue; 94% of people with chronic fatigue syndrome have muscle pain. Women make up the majority of patients suffering from this disease.

The nerve endings of a muscle in mice show that ASIC3 (red) is present in the pain receptor (orange).(Photo: Dr. Masahiko Ikeuchi MD, scientist at Kochi University at Kochi, Japan)

To investigate the relationship between pain and fatigue, as well as the effects of gender, the UI team compared muscle fatigue due to exercise in male and female mice, using and not using ASIC3. - an acid-activated ion protein that the team has shown is involved in musculoskeletal pain

An exercise consisting of three runs within an hour showed different levels of fatigue in different groups of mice, measured by the reduction in strength due to the exercise.

Male mice that used ASIC3 suffered less fatigue than female mice. However, male rats that did not use ASIC3 had a similar fatigue rate to female mice and remained much more than normal male mice.

In addition, when female mice using ASIC3 were given male sex hormones, their muscles became resistant to fatigue like normal male mice. In contrast, muscle strength of female mice without this protein is not increased by male sex hormones.

'The difference between fatigue in males and females depends on the presence of male sex hormones and the activation of ASIC3. This suggests that they interact with each other and protect them from fatigue. These differences may help explain some of the contradictions we often see in chronic pain that lead to fatigue that primarily occurs in women. '

The study was published on February 28 in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. Research indicates that muscle aches and fatigue are not independent diseases but may have a common path broken when patients suffer from chronic muscle pain. Scientists plan to continue the study with the goal of understanding whether pain makes women more tired than men.

Sluka said: 'Our long-term goal is to find better treatment for chronic musculoskeletal pain. But fatigue often associated with chronic pain is also a serious medical problem - it makes the sick person unable to work or participate in social activities. If we can find ways to reduce fatigue, it will improve the quality of life of patients. "

In addition to Sluka, UI's research team includes Lynn Burnes, the study's lead author, Sandra Kolker, Jing Danielson and Roxanne Walder. The study was funded by the National Academy of Arthritis, Musculoskeletal, and Dermatology.