Obese adipose tissue modulates proinflammatory responses of mouse airway epithelial cells

Abstract

Although recognized as an important endocrine organ, little is known about the mechanisms through which adipose tissue can regulate inflammatory responses in distant tissues, such as lung that are affected by obesity. To explore potential mechanisms, male C57BL/6J mice were provided either high-fat diet, low-fat diet, or were provided a high-fat diet then switched to the low-fat diet to promote weight loss. Visceral adipocytes were then cultured in vitro to generate conditioned media (CM) that was used to treat both primary (mouse tracheal epithelial cells; MTECs) and immortalized (mouse-transformed club cells; MTCCs) airway epithelial cells. Adiponectin levels were greatly depressed in the CM from both obese and diet-switched adipocytes relative to mice continually fed the low-fat diet. MTECs from mice with obesity secreted higher baseline levels of inflammatory cytokines than MTECs from lean or diet-switched mice. MTECs treated with obese adipocyte CM increased their secretion of these cytokines compared with MTECs treated with lean CM. Diet-switched CM modestly decreased the production of cytokines compared with obese CM, and these effects were recapitulated when the CM was used to treat MTCCs. Adipose stromal vascular cells from mice with obesity expressed genes consistent with an M1 macrophage phenotype and decreased eosinophil abundance compared with lean stromal vascular fraction, a profile that persisted in the lean diet-switched mice despite substantial weight loss. Soluble factors secreted from obese adipocytes exert a proinflammatory effect on airway epithelial cells, and these alterations are attenuated by diet-induced weight loss, which could have implications for the airway dysfunction related to obese asthma and its mitigation by weight loss.