Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 18 1 2019 02 24 48 61 EN Hassan Ghobadi Department of Internal Medicine, Pulmonary Division, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran Mohammad Reza Alipour Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Rana Keyhanmanesh Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Mohammad Hossein Boskabady Neurogenetic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Mohammad Reza Aslani Ardabil Imam Khomeini Educational and Clinical Hospital, Ardabil University of Medical Sciences, Ardabil, Iran 2018 02 15 2018 07 18 Epidemiological and clinical studies have demonstrated a close association between obesity and asthma. The current study investigated the effect of high-fat diet on tracheal responsiveness to methacholine and insulin resistance in ovalbumin (OVA) sensitized male and female rats. The rats were divided into eight groups (n=6 per group): female with the normal diet (F+ND), male with the normal diet (M+ND), female OVA-sensitized with the normal diet (F+SND), male OVA-sensitized with the normal diet (M+SND), female with high-fat diet (F+HFD), male with high-fat diet (M+HFD), female OVA-sensitized with high-fat diet (F+SHFD), and male OVA-sensitized with high-fat diet (M+SHFD). All rats were fed for 8 weeks with high-fat diet or standard pelts, and for another 4 weeks, they were sensitized with OVA or saline. At the end of the study, the tracheal responsiveness to methacholine, serum insulin, and blood glucose levels was measured. Also, insulin resistance indexes were determined. OVA-sensitization and diet-induced obesity caused the curve of methacholine concentration response to shifting to the left. In addition, results indicated that the EC50 (the effective concentration of methacholine generating 50% of peak response) in F+SHFD rats was statistically lower than M+SHFD group (p<0.05). Moreover, insulin resistance was higher in the F+SHFD than the M+SHFD group (p<0.001). These results suggest that insulin resistance and metabolic syndrome may be involved in the pathogenesis of obesity associated with OVA-sensitized rats condition, especially in female animals.   https://ijaai.tums.ac.ir/index.php/ijaai/article/view/1874 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/1874/1394