Description, Causes and Risk Factors:
The loss of muscle mass during aging has been termed as sarcopenia. There is growing evidence linking sarcopenia to functional disability, falls, decreased bone density, glucose intolerance, and decreased heat and cold tolerance in older adults.
Although most often seen in physically inactive people, sarcopenia is also common in those who remain physically active throughout their lives. Inactivity is not the only contributing factor to this condition. Like osteoporosis, sarcopenia is a multifactorial disease process that may result from inadequate dietary protein, suboptimal hormone levels, other nutritional imbalances, lack of exercise, oxidative stress, and inflammation.
Today, however, sarcopenia is increasingly recognized as a serious health problem that afflicts millions of aging adults and places an ever-greater strain on our health care system. Age-related loss of muscle mass and strength not only robs elderly people of the ability to perform even the most basic tasks of daily living, but also vastly heightens their risk of suffering devastating injuries and even death from sudden falls and other accidents.
Major dietary factors that contribute to sarcopenia are inadequate protein intake, insufficient calorie intake, and chronic, low-level metabolic acidosis (or an abnormally increased acidity in the body's fluids).
Aging is accompanied by declining levels of many essential hormones in the body, particularly tissue-building (anabolic) hormones such as growth hormone, DHEA (dehydroepiandrosterone), and testosterone.
Researchers have recently focused on insulin-like growth factor 1 (IGF-1) and mechano growth factor (MGF) as critical hormones in maintaining muscle and bone mass. Without adequate levels of these hormones, it may be impossible for anyone to maintain lean body mass, regardless of how they eat or exercise.
Testosterone is also critical to maintaining lean body mass. Especially when given to testosterone-deficient men, this essential hormone can have a broad range of positive effects. One study noted that in healthy older men with low-normal to mildly decreased testosterone levels, testosterone supplementation increased lean body mass and decreased fat mass. Additionally, testosterone improved upper and lower body strength, functional performance, sexual function, and mood in some individuals. Although women produce less of this hormone than men do, adequate testosterone is just as essential to their health and well-being.
Because hormonal factors can significantly affect muscle mass, all adults over the age of 40 should undergo annual blood testing to track their hormone levels. If necessary, hormone deficiencies can be addressed using bioidentical hormone replacement therapy. Since hormone replacement therapy requires regular monitoring and is contraindicated in some individuals, you should consult a medical professional about your specific hormone replacement needs.
Fat cells produce inflammatory cytokines (tumor necrosis factor [TNF-?] & interleukin-6 [IL-6]), so circulating levels of these inflammatory cytokines are in part related to the ratio of lean body mass to total mass ratio. In the elderly this increased level of inflammatory cytokines stimulates an immune system that is already primed by years of response to environmental activation. The combination produces chronic low-grade inflammatory damage to multiple organs, & this explains in part the rapid deterioration of so many organ systems in obese elderly patients.
Another etiologically important consideration is the age-related exposure of the body's DNA to damage by reactive oxygen species (ROS). This damage produces somatic mutations in the synthesis of proteins. The proteolytic enzymes of the respiratory chain are not immune from such mutations & as they occur, aerobic energy production becomes less efficient. This increases ROS production & eventually exhausts cellular antioxidant defenses, allowing tissue accumulation of ROS & reducing protein synthesis. This depletes the pool of satellite cells that are usually recruited to replace damaged fibers & promote their regeneration, so muscle atrophy ensues & with it weakness. A selective loss of fast-twitch fibers occurs as a result of slower regeneration of fast-twitch fiber units because of the loss of spinal cord motor neurons that occurs with aging. After denervation, many of the fast twitch fiber units become reinervated by slow twitch fibers that sprout from adjacent slow twitch motor units. This slows muscle unit firing rates & thereby slows muscle contraction.
Age related sarcopenia is not a benign condition. The decreased metabolicrate produces musculoskeletal weakness, early fatigability & loss of stamina, which in turn tends tofurther reduce physical activity. This initiates a viscous cycle by further reducing muscle mass.
Netoutcomes include decreasing the incidence & prevalence of insulin resistance, diabetes mellitus type2 (DM2), hypertension & dyslipidemia, that lead in turn to cardiovascular disease, increased fall risk& other comorbidities that impair quality of life, increase health care costs & reduce life expectancy.
Although there is no generally accepted test or specific level of muscle mass for sarcopenia diagnosis, any loss of muscle mass is of consequence because loss of muscle means loss of strength and mobility. Sarcopenia accelerates around age 75 and is a factor in the occurrence of frailty and the likelihood of falls and fractures in the elderly.
Older adults should strive to ensure an adequate intake of high-quality protein, abundant consumption of fruits and vegetables, and a reduced intake of cereal grain foods.
Several nutrients, including creatine, vitamin D, and whey protein, have shown great promise in combating sarcopenia. Other nutrients such as omega-3 fatty acids, carnitine compounds, and the amino acid glutamine have biological effects that may be beneficial in promoting healthy muscle mass.
Regular exercise, particularly weight training, is essential for preserving and increasing muscle mass. In addition to building muscle, strength training promotes mobility, enhances fitness, and improves bone health.
Preventing and treating sarcopenia requires an integrated approach that incorporates dietary strategies, hormone replacement, nutritional supplementation, and exercise.
Although drug therapy is not the preferred treatment for sarcopenia, a few medications are under investigation. They include:
Urocortin II: This peptide has been shown to stimulate the release of a hormone called adrenocoticotropic hormone (ACTH) from the pituitary gland. Intravenous urocortin II has been shown to prevent muscle atrophy from being in a cast or taking certain medications; it has also been shown to cause muscle growth in healthy rats. But its use for building muscle mass in humans has not been studied is and is not recommended.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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