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~ Of Worms and Women: SARCOPENIA: and its Role in Disability and Mortality~
by
Barbara Riley-Baker, BA, MA, CMC, C.P.G.

Article Review: The nonparasitic nematode Caenorhabditis elegans (C. elegans) are microscopic worm-like organisms. C. elegans were discovered about ten years ago to be powerful genetic systems in which to study biochemical and molecular events involved in aging organisms. The total lifespan of C. elegans ranges from 12 to 18 days making them ideal for studying aging changes such as Sarcopenia.

Sarcopenia is a Greek word (poverty of flesh) for loss of muscle mass. In humans and C. elegans, sarcopenia leads to declines in strength, mobility and overall functioning. Sarcopenia also serves as a marker for increased mortality and a possible biomarker for biological age. In aging C. elegans, sarcopenia starts in 7 days, the post reproductive period. The affected worms show a progressive and irreversible decline in mobility affecting their ability to find food, avoid predators, and escape unfavorable environmental conditions.

In humans our muscle mass peaks in young adulthood and begins to decline starting at age 45. By age 90, in most humans, Sarcopenia causes the loss of nearly 50% in our muscle mass. Fat infiltrates into the remaining muscles. This older muscle mass is unable to produce equivalent power per unit of area to that of a younger muscle. These changes are more noticeable in men but more problematic in women.  Women are not as muscular as men.

In humans, factors contributing to sarcopenia include; sedentary lifestyle, and insufficient amounts of protein and calories in the diet. However, these factors are inadequate to account for the prevalence and progressive nature of sarcopenia. Sarcopenia is observed in other aging mammals such as mice.

The Framingham cohort data shows that women aged 55 to 64 showed a 40% loss, women aged 65-74 showed a 45% loss, women aged 65-74 showed a 65% loss and women aged 75 to 84 were unable to lift objects weighing 10 pounds and more. The study also showed a decline in leg and knee strength resulting in decreases in mobility, ability to climb stairs and walking speed. Sarcopenia has also been associated with declines in independence (activities of daily living) and increased need of assistive devices to reduce the risk of falls.

Mutations affecting the age-1 gene, slow aging in the C. elegans resulting in significant delays in the development of sarcopenia and an extended lifespan of 60 to 100%.  This little worm is a genetic system in which to study pathophysiology of sarcopenia and possible pharmacological interventions to improve mobility and reduce death in  C. elegans and humans, especially in women.

Opinion:  This article by Alfred L. Fisher, MD, PhD is an interesting study on the loss of muscle mass that occurs during aging and the role the microscopic worm, C. elegans, can play in understanding this process. C. elegans are also a perfect testing-ground for possible interventions to delay the onset of Sarcopenia, a biological marker. The title, “Of Worms and Women”, grabs your attention and peaks your interest.

Muscle wasting is a major cause of frailty and loss of independence in seniors. This frailty contributes to falls, fractures, fears, and changes in life styles. Seniors often give up enjoyable activities after a fall.  Even after the broken bones are healed, seniors may become more isolated, withdrawn, and depressed fearing another fall.  The loss of muscle mass increases their dependence on others to perform ADLs and IADLs.  This  loss of functioning  is a factor in placing loved ones in nursing homes.

If this little worm can accelerate the study of sarcopenia the impact on all of us would be immeasurable. If the decline in our muscle mass could possibly be delayed from 45 years to 75 years of age, the quality of human life would be greatly enhanced; there would be a tremendous reduction in hospital visits, and other medical costs including the costs for Medicare and Medicaid and the taxes that pay for them.  The cost savings would benefit the entire society, not just seniors.

Strengths and Weaknesses of the Article:  The development of sarcopenia represents the aging of the muscular system and a biological marker for biological age and mortality. The article makes a strong case for the use of C. elegans in the study of sarcopenia in loss of muscle mass.  However, optimal muscle functioning is not only determined by muscle mass but also by muscle strength. The little worms, C. elegans, won’t be able to help us in this area.  Also, as mentioned in the article, scientists need to arrive at a consensus in the definition of sarcopenia and a consistent means of measuring it.

Correlation to text: 

• The life cycle of the C. elegans is similar to that of humans; development, maturation and aging.

• The life span of the C. elegans can be enhanced by altering the age-1 gene. In humans life span will not change without altering the genetic code.

• Loss of muscle mass in C. elegans and humans encompasses multiple theories in biological aging.  Biological Aging Theories: programmed aging theory, somatic mutation theory, free radical theory, stress theory, hormone theories, and the wear and tear theory.

Reference

 Fisher, Alfred, L., (2004).  Of Worms and Women: Sarcopenia And its Role in disability and Mortality.  Journal of the American Geriatrics Society, V 52, No. 7, p. 1185-1190, July 2004.