Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 378

Age‐associated increases in the production and/or effect of satiating cytokines may contribute to the anorexia of ageing⁶⁷. Cytokines are secreted in response to significant stress, often because of malignancy or infection. Circulating concentrations of the cytokines interleukin 1 (IL‐1), interleukin 6 (IL‐6), and TNF‐α are increased in cachectic patients with cancer or AIDS. They act to decrease food intake and reduce body weight via a number of central and peripheral pathways. Blockade of these cytokines – for example, of TNF‐α in mice with TNF‐producing sarcomas – significantly attenuates weight loss in high‐stress conditions associated with cachexia. Ageing itself may be a form of stress. It is associated with stress‐like changes in circulating hormonal patterns, increased cortisol and catecholamines, and decreased sex hormones and growth hormone. Increased cortisol and catecholamine levels, in turn, stimulate the release of IL‐6 and TNF‐α, whereas sex hormones inhibit IL‐6. Interleukin 1 and IL‐6 levels are elevated in older people with cachexia, whereas plasma IL‐6 concentrations apparently increase as a function of normal ageing and correlate inversely with levels of functional ability in elderly people. Higher circulating levels of CRP and cytokine receptors also appear to be associated independently with physical dysfunction and disability.⁶⁸ Increased cytokine levels due to the stress of ageing per se or the amplified stressful effects of other pathologies may explain some of the declines in appetite and body weight that occur in many older people.³⁰