Catabolic Wasting - Cachexia and Sarcopenia
Loss of muscle and fat tissue due to chronic illness is called cachexia. The general loss of weight and muscle mass that occurs with advancing age is called sarcopenia. In both cachexia and sarcopenia, muscle loss can lead to frailty and adversely affect a variety of clinical outcomes (Rolland 2011; Fearon 2013; Muscaritoli 2013).
Individuals with cachexia and/or sarcopenia have an increased risk of death, infection, and falls; slower wound healing; significantly lower exercise and breathing capacity; and overall diminished quality of life (Sirola 2011; Paddon-Jones 2009; Janssen 2004; Zacker 2006; Thomas 2007; Cosqueric 2006; Cawthon 2007).
Cachexia and sarcopenia share some pathological mechanisms, including excess levels of systemic inflammation, oxidative damage, and reduced levels of anabolic hormones like testosterone, and may occur simultaneously (Rolland 2011; Fearon 2013; Muscaritoli 2013). The term “catabolic wasting” encompasses both sarcopenia and cachexia. (“Catabolic” refers to the breakdown of tissue; it is the opposite of “anabolic,” which means tissue-building.)
Cachexia usually causes more rapid and pronounced weight reduction than sarcopenia and is generally characterized as loss of muscle and fat tissue totaling more than 5% of body weight, but losses of more than 20% of body weight are common (Rolland 2011; Nicolini 2013; Siddiqui 2006; Muscaritoli 2013; Gordon 2004; Gullett 2011). In many cases, a person with cachexia continues losing weight even if they are getting enough calories (Siddiqui 2006; Muscaritoli 2013).
Severe, chronic illnesses such as cancer, AIDS, and chronic obstructive pulmonary disease (COPD) are known causes of cachexia (Sididqui 2006; Fearon 2013). Between 50% and 80% of all cancer patients experience cachexia, and it is estimated that cachexia is the main cause of over 20% of all cancer-related deaths (Nicolini 2013; von Haehling 2010; Suzuki 2013). Cachexia in HIV/AIDS patients is common and occurred almost universally before the advent of antiviral HIV drugs (Guillory 2013).
Sarcopenia (from the Greek meaning "poverty of flesh") generally refers to age-related loss of muscle mass and function (Iannuzzi-Sucich 2002). Approximately 50% of people over age 80 experience sarcopenia (Baumgartner 1998; Janssen 2004).
Sarcopenia can also occur as a result of physical inactivity, poor nutrition, or illness. Some researchers refer to age-related muscle loss not associated with an underlying cause as “primary sarcopenia,” and that which occurs as a consequence of one or more other causes as “secondary sarcopenia” (Rolland 2011; Muscaritoli 2013). Also, sarcopenia can sometimes occur in a person who still has significant fat stores, a condition known as “sarcopenic obesity” (Zamboni 2008). Sarcopenia is associated with increased risk of insulin resistance and type 2 diabetes in non-obese adults over age 60 years (Moon 2013).
The conventional medical establishment often fails to provide early, aggressive intervention for cachexia, resulting in poor clinical outcomes, including premature death and disability. Standard medical treatments for cachexia include encouraging consumption of liquids and food and use of certain drugs. However, many standard medical therapies to treat sarcopenia and cachexia present the risk of adverse effects such as nausea, edema, and fatigue, and some of them have not been adequately tested in clinical trials (Gullett 2010; Fox 2009; Fearon 2013). Early recognition and treatment of cachexia is even more important, considering that losing as little as 5% of body weight in cancer patients may increase the risk of adverse effects from chemotherapy drugs (Brotto 2012; Fearon 2013).
A number of nutritional, lifestyle, and innovative pharmacological interventions may be useful to prevent and treat catabolic wasting. Whey protein, creatine, and the amino acids glutamine, arginine, leucine, and hydoxy-methylbutyrate or HMB (a leucine derivative) are especially important for building and maintaining lean muscle mass (Thomas 2007; Casperson 2012; Katsanos 2008; Kim 2010; Clark 2000; Hayes 2008; Kim 2010). Omega-3 fatty acids, conjugated linoleic acid, and vitamin D also fight lean tissue loss (Siddiqui 2006; Rahman 2009; Drey 2011; Kim 2011).
Many interventions can often produce dramatic improvements in muscle mass/strength and overall health of people with muscle wasting. This protocol will describe catabolic wasting conditions and report on some common interventions to prevent and treat lean tissue loss. Research on novel and emerging strategies for the prevention of muscle wasting will be reviewed as well.