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

OBJECTIVE: Obesity 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. METHODS: Diet‐induced obesity (DIO) and lean control mice received intranasal instillations of 10(9) or 10(10) CFUs of E. coli. The immune responses were examined at 0 h (uninfected), 24 h, and 96 h postinfection. RESULTS: Following 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 10(10) 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 10(9) 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. CONCLUSIONS: The 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.