What is Muscle Atrophy?
Muscle atrophy, as the name suggests, is a weakening or reduction of muscle due to lack of use or due to a disease. It is a result of a mismatch between the rates of protein synthesis and protein breakdown.
Protein is required for muscle mass, therefore muscle wasting occurs when the amount of protein broken down is more than that synthesized.
What is New in Muscle Atrophy?
Muscle atrophy is caused due to several reasons. Some of them are listed below (Jackman RW; Bonaldo P; medline; Vinciguerra M; Brooks NE – 2014):
Neurogenic muscle atrophy is caused when the nerve supplying a particular muscle is affected by a disease or is injured. The onset of atrophy is sudden and this form of atrophy is severe. Causes of neurogenic muscle atrophy include:
Disuse atrophy results when muscles are not used for a prolonged period. This type of atrophy can be rectified with appropriate diet and exercise. Causes of disuse atrophy include:
- Prolonged bedrest
- Sedentary form of work
- Spaceflight (due to loss of gravity)
- Reduced levels of activity
- Joint disorders like rheumatoid arthritis and osteoarthritis
Other causes of muscle atrophy include:
- Diseases that increase catabolic rates like hyperthyroidism, cancer, AIDS, burns, congestive cardiac failure, kidney failure and chronic obstructive lung disease
- Starvation / malnutrition / fasting
- Older age
- Prolonged corticosteroid treatment
- Muscular dystrophy
- Metabolic acidosis
- Genetic conditions like spinal muscular atrophy
Muscle atrophy is characterized by shrunken muscles with less strength. Some of the symptoms of muscle atrophy include:
- Thinning out of the muscle
- Muscle pain (myalgia)
In the case of spinal muscular atrophy (SMA) I, children are unable to sit, roll, or stand. They usually do not survive beyond the age of 2 years. Children with SMA II cannot walk without support although they live well into their adolescence. Children with SMA III are able to walk at a certain point in their life and have a normal lifespan.
Those with neuralgic amyotrophy have extreme pain followed by atrophy in the upper limbs.
The diagnosis of muscle atrophy is based on the clinical examination of the patient. Tests are conducted to confirm the diagnosis and to identify the underlying cause. These include:
- Radiological tests: Radiological tests like MRI, CT scan and x-ray can confirm the presence of muscle atrophy. Radiological imaging of the spine may help to detect spinal abnormalities contributing to the atrophy. Positron emission tomography (PET) scan provides information on the functioning capacity of the muscle. Dual-energy X-ray absorptiometry (DXA) gives a measure of the bone mineral density, which may also be reduced in a patient with skeletal muscle atrophy.
- Blood tests: Routine blood tests as well as specific blood tests to confirm the suspected cause will be necessary.
- Electromyography and nerve conduction studies: Electromyography (which studies the electrical activity of muscles) and nerve conduction studies can help to diagnose the location of the problem.
- Biopsy of nerves or muscles – Biopsy of the muscle and sometimes the nerve supplying the muscle can diagnose the exact reason for the muscle atrophy.
There is no effective drug to treat muscle atrophy including spinal muscle atrophy. In general, the goal of treatment is to reduce the symptoms of the condition, and make life more comfortable for the patient. Ultrasound therapy, physical therapy, and the use of wheelchairs, braces, and surgery are some of the ways used to treat muscle atrophy. Oral prednisone is also used in some patients.
Disuse muscle atrophy can be reversed with the following treatments:
It has been observed that testosterone supplementation is very useful in treating muscle atrophy due to old age. It is particularly effective when combined with load-bearing exercise. There is an improvement in the size of muscle fibers, muscle strength, and muscle-regenerating satellite cells in older people.
There are 2 types of exercises that can be performed to prevent or treat certain forms of muscle atrophy.
Resistance exercise – This form of exercise has been found to be very effective in decreasing muscle atrophy, increasing the production of proteins, and improving muscle masss and strength. This type of exercise is very effective in improving muscle mass in the elderly although other health conditions should be taken into consideration before such exercises are prescribed. Resistance exercise is when the muscle is made to exert a force against resistance, such as an immovable object, weight, or water.
Endurance exercise – This form of exercise is great for cardiovascular health. However, since there is no weight or load placed on muscles, the atrophy of skeletal muscles continues. This exercise is helpful when it is combined with resistance exercise. Aerobic exercise improves the use of oxygen by the body and also improves the heart rate.
Creatine – This nutritional supplement helps in improved recovery following a period of immobilization. Creatine improves muscle mass and the production of energy. Despite varied reports on the usefulness of creatine in preventing muscle atrophy, this inexpensive supplement remains a relevant supplement in alleviating muscle atrophy. The dosage and the time of day when the supplement is given, may play a role in relieving muscle atrophy.
Amino acid supplementation – Exercise may not always be feasible as in the case of bedrest. Hence, supplementation with essential amino acids helps to increase the synthesis of protein, though the increase in muscle mass with amino acid supplementation is not to the same extent as exercise. It is most effective when combined with exercise.
Those who have a genetic predisposition to muscle diseases should see a genetic counsellor to identify their risk of having the condition.
- Vinciguerra M, Musaro A, Rosenthal N. Regulation of muscle atrophy in aging and disease. Adv Exp Med Biol. 2010;694:211-33.
- Naomi E. Brooks and Kathryn H. Myburgh (2012). Prevention of Skeletal Muscle Wasting: Disuse Atrophy and Sarcopenia, Skeletal Muscle - From Myogenesis to Clinical Relations, Dr. Julianna Cseri (Ed.), InTech, DOI: 10.5772/47856.
- Jackman RW, Kandarian SC. The molecular basis of skeletal muscle atrophy. American Journal of Physiology - Cell Physiology. 2004;287(4):C834-C843.
- Bonaldo P, Sandri M. Cellular and molecular mechanisms of muscle atrophy. Disease Models & Mechanisms. 2013;6(1):25-39.
- Brooks N, Myburgh K. Skeletal muscle wasting with disuse atrophy ismulti-dimensional: the response and interaction of myonuclei, satellite cells and is signaling pathways. Frontiers in Physiology. 2014;5(99).
- Theodorou DJ, Theodorou SJ, Kakitsubata Y. Skeletal muscle disease: patterns of MRI appearances. The British Journal of Radiology. 2012;85(1020):e1298-e1308. doi:10.1259/bjr/14063641.
- Wadman RI, Bosboom WMJ, van der Pol WL, van den Berg LH, Wokke JHJ, Iannaccone ST, Vrancken AFJE. Drug treatment for spinal muscular atrophy type I. Cochrane Database of Systematic Reviews 2012, Issue 4. Art. No.: CD006281. DOI: 10.1002/14651858.CD006281.pub4.
- Wadman RI, Bosboom WMJ, van der Pol WL, van den Berg LH, Wokke JHJ, Iannaccone ST, Vrancken AFJE. Drug treatment for spinal muscular atrophy types II and III. Cochrane Database of Systematic Reviews 2012, Issue 4. Art. No.: CD006282. DOI: 10.1002/14651858.CD006282.pub4
- van Alfen N, van Engelen BGM, Hughes RAC. Treatment for idiopathic and hereditary neuralgic amyotrophy (brachial neuritis). Cochrane Database of Systematic Reviews 2009, Issue 3. Art. No.: CD006976. DOI: 10.1002/14651858.CD006976.pub2.
- Voet NBM, van der Kooi EL, Riphagen II, Lindeman E, van Engelen BGM, Geurts ACH. Strength training and aerobic exercise training for muscle disease. Cochrane Database of Systematic Reviews 2013, Issue 7. Art. No.: CD003907. DOI: 10.1002/14651858.CD003907.pub4.
- Marimuthu, K., Murton, A. J., and Greenhaff, P. L. (2011). Mechanisms regulating muscle mass during disuse atrophy and rehabilitation in humans. J. Appl. Physiol. 110, 555–560. doi: 10.1152/japplphysiol.00962.2010
- Resistance Training (Strength Training) - (https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022361/)
- Atrophy - (https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024970/)
- What is Muscle atrophy? - (https://medlineplus.gov/ency/article/003188.htm)
- Muscle Atrophy (Muscle Wasting) - (https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0024971/)
- Muscular dystrophy - (https://medlineplus.gov/ency/article/001190.htm)
- Amyotrophic lateral sclerosis (ALS) - (https://medlineplus.gov/ency/article/000688.htm)
Latest Publications and Research on Muscle Atrophy
- Revised Recommendations for the Treatment of Infants Diagnosed with Spinal Muscular Atrophy Via Newborn Screening Who have 4 Copies of SMN2. - Published by PubMed
- Inflammatory biomarkers of frailty. - Published by PubMed
- Functional supramolecular bioactivated electrospun mesh improves tissue ingrowth in experimental abdominal wall reconstruction in rats. - Published by PubMed
- Age-related degeneration of the lumbar paravertebral muscles: Systematic review and three-level meta-regression. - Published by PubMed
- Controllable Forces for Reproducible Chronic Constriction Injury Mimicking Compressive Neuropathy in Rat Sciatic Nerve. - Published by PubMed