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Bone density, body composition, and inflammatory status in Cystic Fibrosis

Ionescu, Alina A., Nixon, Lisette S., Evans, William D., Stone, Michael D., Lewis-Jenkins, Vanessa, Chatham, Ken and Shale, Dennis J. 2000. Bone density, body composition, and inflammatory status in Cystic Fibrosis. American Journal of Respiratory and Critical Care Medicine 162 (3) , pp. 789-794. 10.1164/ajrccm.162.3.9910118

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Low body weight and loss of bone mass are major problems in adults with cystic fibrosis (CF) and chronic pulmonary infection. Although these complications probably have a multifactorial origin, we hypothesized that the continuous acute-phase inflammatory and catabolic state may contribute. We determined body composition, bone turnover, physical activity, and circulating interleukin-6 (IL-6), tumor necrosis factor- α (TNF- α ), and their soluble receptors in 22 adults with CF and 22 age- and sex-matched healthy subjects. Comparisons were also made within patients before and after treatment of an exacerbation of respiratory symptoms. The patients had a lower mean (95% confidence interval [CI]) fat-free mass (FFM) 39.9 (36.3, 43.6) kg than healthy subjects, 49.4 (45.1, 53.7) kg, p < 0.05. The patients were in negative nitrogen balance and 20 had bone mineral density (BMD) Z scores ⩽ 2.5 SD (n = 13) or ⩽ 1 SD (n = 7) at least at one site. They had increased bone collagen breakdown, greatest in those with a reduced FFM. BMD was related to FEV1 (r = 0.44), IL-6 (r = − 0.60), and TNF- α -soluble receptors (r = − 0.42, r = − 0.50). Patients with a low FFM had greater concentrations of IL-6, which suppressed less after antibiotic treatment than in those with a normal FFM. Those with a low FFM were more catabolic and less active than those with a normal FFM. The association between altered body composition, catabolic status, and circulating inflammatory mediators suggests that chronic pulmonary infection in adults with CF may be a contributory factor in the long-term complications of low weight and bone disease. Attainment of adulthood is now common in cystic fibrosis (CF) and survival continues to increase. Such patients experience chronic pulmonary infection from very early in life, which is a major determinant of survival because of its association with lung destruction (1). Additionally, failure to maintain body weight is an indicator of a poor prognosis. The major complications emerging with longer survival are failure to maintain body mass, osteoporosis, and diabetes mellitus (1-10). These metabolic complications have an impact on morbidity as well as mortality. Loss of fat-free mass (FFM) impairs skeletal muscle function including the inspiratory muscles and adds to the severity of pulmonary compromise (11, 12). Reduction in both bone mineral density (BMD) and FFM may be linked by physical inactivity, possible malabsorption, corticosteroid therapy, reduced sex hormone levels, increased resting energy expenditure (REE), and hypoinsulinemia associated with diabetes mellitus. An additional metabolic possibility is a generalized loss of body protein secondary to an association between chronic lung disease and a catabolic intermediary metabolism. Chronic pulmonary infection with associated continuous inflammatory and catabolic responses present in patients even when clinically stable may affect body composition (13). This catabolic state as part of the stress response to infection and inflammation could be mediated by the combined effects of catecholamines, proinflammatory cytokines such as interleukins 1β and 6 (IL-1β, IL-6) and tumor necrosis factor-α (TNF-α), and stress-response hormones such as cortisol, and induce protein breakdown in muscle and bone (13, 14). Supporting a link between the lung disease in CF and body composition is the effect of antibiotic treatment of an exacerbation of respiratory symptoms, which partially reduces the inflammatory response with a modest weight gain (15, 16). We hypothesized that the normally host-protective, acute-phase inflammatory and catabolic responses are sustained in patients with CF and chronic pulmonary infection, and add to other mechanisms of weight loss and bone demineralization. Such links have been suggested to occur in human immunodeficiency virus (HIV) infection, cancer, and cardiac failure where cachexia is associated with excess procatabolic hormones and increased circulating inflammatory mediators (17– 20). To test these ideas, we studied adult patients with CF and chronic pulmonary infection during an exacerbation of respiratory symptoms and its treatment to determine relationships between the host inflammatory response, body composition, bone protein turnover, and catabolic status.

Item Type: Article
Date Type: Publication
Schools: Medicine
ISSN: 1073-449X
Last Modified: 23 Aug 2021 14:45

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