Medical Insight（November 22^nd, 2007）

Self-made Audio Programme 21 (本人原声)

you can download this audio material at http://www.zshare.net/audio/5083625e034e9f/

Welcome to Medical Insight November 22nd, 2007,I’m Dr. Alex Roy. A Chitinases, a family of hydrolases, have been associated with animal models of asthma. In this cross-sectional study, circulating levels of YKL-40, a human chitinase-like protein, were examined in three cohorts of patients with asthma.

Although there was some overlap between controls and patients with asthma, on average, circulating YKL-40 levels were higher in patients with asthma. In all three cohorts, serum YKL-40 levels correlated positively with the severity of asthma and inversely with the Forced Expiratory Volume in 1 second. Patients with elevated levels of YKL-40 had significantly more frequent rescue-inhaler use, greater oral corticosteroid use, and a greater rate of hospitalization than patients with lower levels. YKL-40 is found in increased quantities in the serum and lungs in a subgroup of patients with asthma, in whom expression of chitinase in both compartments correlates with the severity of asthma. The recovery of YKL-40 from these patients indicates either a causative or a sentinel哨兵 role for this molecule in asthma.

Burton Dickey from the University of Texas M.D. Anderson Cancer Center, in Houston explains at an editorial that Chitin can be introduced into the airway by the inhalation of fragments from the exoskeletons of insects such as dust mites and cockroaches, or by the inhalation of fungi such as alternaria支链孢属and aspergillus曲霉菌. Chitin may also be introduced into the lungs by helminths蠕虫exiting the pulmonary circulation and ascending the airways to reenter the gastrointestinal tract.

Dickey discusses the role of Chitin in allergic inflammation in the airway, and writes that a system honed through evolution to protect us against serious parasites may now be contributing to widespread asthma and allergies because of the harmless chitin-encased insects that have followed us into our homes.