Dietary Fish Oil Reduces Survival and Impairs Bacterial Clearance in C3H/Hen Mice Challenged with Listeria Monocytogenes

Abstract

1. To investigate the effect of dietary fat source on host resistance to intracellular pathogens, weanling female C3H/Hen mice were fed one of three experimental diets containing, 20% by weight, lard, soybean oil or 17% menhaden fish oil plus 3% corn oil. After 4 weeks, survival of mice (n = 12/treatment group) injected intraperitoneally with 2 x 10(6) colony forming units of live Listeria monocytogenes was determined. In a second study, bacterial clearance from the liver and spleen at 2, 4 and 7 days post-challenge was determined (n = 8/treatment group). 2. We found that the survival of mice fed the diets with soybean oil or menhaden fish oil was significantly lower than those fed lard (P < 0.05). Survival rates were 58% (7/12), 33% (4/12) and 100% (12/12), respectively, for mice fed soybean oil, menhaden fish oil and lard. In the second study, mice fed menhaden fish oil had approximately 1 log10 greater bacteria in their spleens at day 4 than mice fed lard or soybean oil (P < 0.001). There were no significant treatment differences in the number of bacteria recovered from liver samples. 3. In summary, dietary fat source significantly affects murine resistance to Listeria, with diets rich in n-3 polyunsaturated fatty acids, such as from fish oil, having the most detrimental effect.

Relevance of Dietary Lipids as Modulators of Immune Functions in Cells Infected with Listeria monocytogenes

“…Nevertheless, cytotoxicity associated with L. monocytogenes growth was increased in the groups fed OO (which consists of monounsaturated fatty acids) or FO, whereas a significant reduction of cytotoxic effects was observed in the groups fed LF and HCO after 6 h of incubation in the presence of L. monocytogenes. These data suggest that the potential effects of an FO diet on lymphocyte proliferation or cytotoxicity could be related to the previously described reduction in the survival of mice after experimental infection with L. monocytogenes or to the reduction of the resistance of mice and their capacity to eliminate this microorganism from the liver or spleen (13,16). Similarly, the effects produced by an HCO diet on lymphocyte proliferation or the cytotoxicity of L. monocytogenes may be associated with the beneficial action of this diet on the survival of mice as well as on the recovery of bacteria from the spleen (13).…”

“…Nevertheless, for obvious reasons, very little information is currently available on the clinical relevance of dietary lipids in the resistance of the human immune system to infectious agents, but numerous studies have described the effects of unsaturated fatty acids on the impairment of immunological functions in animals (14). Thus, diets supplemented with n-3 polyunsaturated fatty acids significantly reduce the survival of mice after experimental infection with Listeria monocytogenes (13,16), as well as the clearance of bacteria from the liver (16) or spleen (13,16) during the course of infection. Experimental infections with this bacterium induce the production of different cytokines, such as gamma interferon, tumor necrosis factor alpha, and interleukin-6, which play an essential role in antilisterial resistance (26).…”

Differential Modulation of Nods Signaling Pathways by Fatty Acids in Human Colonic Epithelial HCT116 Cells

“…It has been demonstrated that the survival of mice fed with fish oil, whose major fatty acids are n-3 PUFAs, was diminished after bacterial infection as compared with mice fed with diet rich in saturated fatty acids or n-6 PUFA (18,19). Moreover, n-3 PUFAs have been suggested to be beneficial in ameliorating various chronic inflammatory diseases including Crohn disease because of their anti-inflammatory properties (20).…”

Biological and Clinical Significance of Lipids as Modulators of Immune System Functions

“…Bacterial clearance from liver or spleen was increased in these animals (25,31), bactericidal activity of peritoneal cells was significantly reduced (62), and cytotoxic effects due to bacterial infection were increased (63), whereas the susceptibility of cells to adhesion or invasion by L. monocytogenes infection was substantially modified (63). These observations indicate the loss of capacity of the immune system from animals fed a diet containing fish oil to destroy and eliminate the infectious agents (25,31,62,63). A recent investigation has contributed to explaining in part the reasons for which n-3 polyunsaturated fatty acids reduce host defense against L. monocytogenes: consumption of EPA or DHA (both contained in fish oil) impairs the production of IL-12 and IFN-␥, cytokines that play an essential role in the innate and adaptive responses of host immune system (32).…”

“…Different reports have described the clinical consequences of dietary supplementation rich in n-3 fatty acids that suppress the immune system functions. Thus, a significant reduction of survival percentage after feeding experimental mice with a diet containing fish oil has been determined (25,31) whereas an increase of survival percentage was observed after challenge with L. monocytogenes in animals fed diets containing either lard oil, hydrogenated coconut oil, or palm oil (15,25,31). These mice were inoculated with a lethal dose of a virulent L. monocytogenes strain, a facultative intracellularly growing bacterium that has been used as a model of infectious and pathogenic processes.…”