Influence of obesity on the tone of bronchial smooth muscles in rats

Background. Overweight and obesity are key factors for the occurrence of many morphofunctional disorders in organs and tissues, including bronchopulmonary system.

The aim. To study the influence of metabolic disorders that occur against the background of obesity on the state of the airways tone in rats.

Materials and methods. Obesity in male Wistar rats was induced using a high-fat and high-carbohydrate diet. In animals, body weight and fat mass were measured, and the heart-lung complex was extracted. In blood serum, the levels of glucose, insulin, leptin, triglycerides, and cholesterol were assessed. Bronchoalveolar lavage fluid was obtained by an open method, in which the concentration of protein, interleukin (IL) 6 and IL-10 was determined. The contractile activity of the isolated bronchial smooth muscle segments was studied using mechanographic method. The effect of acetylcholine (10–7–10–4 M), indomethacin (10–5 M), and forskolin (10–7–10–5 M) on the changes in the tone of airway smooth muscles was assessed.

Results. High-fat and high-carbohydrate diet caused an increase in body weight, visceral obesity, hyperglycemia, insulin resistance, leptinemia, dyslipidemia in rats of the experimental group. In the bronchoalveolar lavage fluid of experimental animals, an increase in the content of protein and IL-6 was found, which positively correlated with the level of leptin and the fat mass. In obese rats, the contractile responses of bronchial smooth muscle segments increased in response to the effect of the cholinergic agent acetylcholine. The bronchoconstrictor effect of acetylcholine was reduced by the cyclooxygenase inhibitor indomethacin. In turn, the adenylate cyclase activator forskolin caused relaxation of the airway segments smooth muscles in rats of both groups, which was more pronounced in the experimental group.

Conclusion. The obtained results indicate that the change in the reactivity of the respiratory tract can be the cause of  bronchospastic conditions in obesity and of the inflammatory reaction in the respiratory system induced by obesity.

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