Diet‐induced obese mice exhibit altered immune responses to acute lung injury induced by Escherichia coli

Abstract

ObjectiveObesity has been associated with impaired immunity and increased susceptibility to bacterial infection. It also exerts protective effects against mortality secondary to acute lung injury. The effects of obesity on immune responses to acute lung injury induced by Escherichia coli were investigated to determine if the above‐mentioned differences in its effects were related to infection severity.MethodsDiet‐induced obesity (DIO) and lean control mice received intranasal instillations of 109 or 1010 CFUs of E. coli. The immune responses were examined at 0 h (uninfected), 24 h, and 96 h postinfection.ResultsFollowing infection, the DIO mice exhibited higher leukocyte, interleukin (IL)−10, IL‐6, and tumor necrosis factor‐α levels and more severe lung injury than the lean mice. Following inoculation with 1010 CFUs of E. coli, the DIO mice exhibited higher mortality and more severe inflammation‐induced injury than the lean mice, but no differences in E. coli counts were noted between the two groups. However, inoculated with 109 CFUs of E. coli, the DIO mice exhibited smaller E. coli burdens at 24 h and 96 h after infection, as well as lower concentrations of IL‐10 and tumor necrosis factor‐α and less severe lung injury at 96 h after infection.ConclusionsThe results support the emerging view that obesity may be beneficial in the setting of milder infection but detrimental in the setting of more severe infection.

Obesity Enhances Antioxidant Capacity and Reduces Cytokine Levels of the Spleen in Mice to Resist Splenic Injury Challenged by Escherichia coli

“…The mice receiving high-fat diet exhibited higher body weight, Lee's index, and levels of TC and TG than those receiving normal diet, which indicated that the DIO mouse model was established as previously described by Wan et al [4]. Altunkaynak et al [8] found that high-fat diet induced 6 Journal of Immunology Research 7 Journal of Immunology Research splenomegaly in female SD rats fed with high-fat diet for a 3-month duration.…”

“…Obesity is growing rapidly around the world, and the diseases associated with obesity have been highlighted in recent years, especially pulmonary disease. Recently, studies suggested that obesity plays a beneficial role in E. coli pneumonia, manifesting that clinically significant changes in pulmonary inflammatory response may be associated with immune status in obesity [4,5]. The spleen is the center of cellular immunity and humoral immunity.…”

“…After one week of adaptation to the environment, all mice were primarily divided into two groups: one is the normal (N) group (n = 128) and the other is the diet-induced obesity (DIO) group (n = 128). The body weight of the mice in each feeding group was measured weekly, and DIO mice could be obtained after feeding the commercial feed diets for 8 weeks from the Dashuo Animal Center (Chengdu, China) as described previously [4,14]. During the experiment, all mice were kept in constant temperature environment at 24°C.…”

“…Obesity was recognized as a significant risk factor for pneumonia with increased incidence and severity of disease [3]. Fascinatingly, Wan et al [4] have reported that the obese mice exhibited more lymphocytes in the bronchoalveolar lavage fluid and milder lung injury than normal mice under the case of nonfatal pneumonia caused by E. coli, suggesting that obesity can improve immune responses against bacterial pneumonia. The DIO mice also presented a delayed pulmonary inflammatory response and oxidative stress in pneumonia induced by E. coli infection [5].…”

“…Additionally, serum triglyceride and total cholesterol contents (A110-1 and A111-1, Nanjing Jiancheng Bioengineering Institute, China) were examined. The mice in N-E. coli and DIO-E. coli were anesthetized with ether and challenged intranasally with 40 μL of bacterial suspension containing approximately 10 9 CFUs of E. coli which was provided by the Veterinary Medical Laboratory of Sichuan Agricultural University (Chengdu, China) as described previously [4,5]. And the same dose of PBS was given to the mice in N-PBS and DIO-PBS by the same method.…”