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Figure 81.2 A loss of muscle strength accompanies sarcopenia. Maximal voluntary isometric contractile force of the dominant knee extensor in healthy community-dwelling Australian women aged 20-87 years. A linear trend accounts for 96% of the systematic variation with age. Reproduced from Hunter (1998) with permission of the publisher.

inflammatory cytokines and lower strength and muscle mass. Animal studies have demonstrated that inflammatory cytokines, like TNFa, act on muscles to promote muscle atrophy through the activation of the transcription factor NF-kB (McKinnell and Rudnicki, 2004). NF-kB produces muscle atrophy at least in part through the activation of specific ubiquitin ligases that degrade muscle proteins. It remains to be determined if the losses of muscle mass due to sarcopenia are secondary to the direct actions of inflammatory cytokines on muscle with the activation of NF-kB.

In people, body weight increases until the late 50s to early 60s before declining in later life (Roubenoff, 2003a; Volpi et al., 2004). Much of the weight loss is due to a reduction in caloric intake, which occurs at a time in life when the daily protein requirement may be increased compared to younger adults. Consequently, weight loss in late life has a significant impact on muscle mass through mild protein calorie malnutrition (Roubenoff, 2003a; Volpi et al., 2004). Clinical studies have demonstrated that supplements containing essential amino acids can have a beneficial effect on muscle protein synthesis (Volpi et al., 2004). Unfortunately, many commercially available supplements obtain most of their calories from either carbohydrate or nonessential amino acids, and as a result these supplements have shown minimal effects in clinical studies (Fiatarone et al., 1994; Volpi et al., 2004).

As the proportion of older people is expected to increase dramatically in both developed and developing countries in the coming decades, the medical, social, and financial impact of sarcopenia and its effect on function are of growing importance. There is a pressing need to better understand the biologic mechanisms involved in sarcopenia to promote the development of new therapeutic approaches. This chapter will provide an introduction to the basic biology of sarcopenia and to the study of sarcopenia in clinical research, experimental animals, and cell-based systems.

Biology of Aging Muscle

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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