Effect of a high-fat diet on resistance to Listeria monocytogenes.

Effects of a high-fat diet on macrophage (M phi) functions were investigated. Eight-week-old ddN mice were fed a high-fat diet and carbon clearance was tested. Remarkable suppression of phagocytic activity (K16) was observed in mice fed such a diet for 1 or 2 weeks. Resistance against Listeria monocytogenes inoculated intravenously (iv) with a lethal, a sublethal, or a non-pathogenic dose was observed in the liver of mice fed a high-fat diet. When mice were infected with a lethal dose of bacteria, the number of listeria increased progressively in the liver to kill both control and a high-fat diet fed mice by day 4. The number of listeria revealed no significant difference between the group in the case of low dose inoculation. High-fat diet fed mice given a sublethal dose of bacteria showed a rise in the number of viable bacteria during the first 3 days after infection while a decline in the number of bacteria was observed in control mice during such a period. Suppression of M phi activity induced by a high-fat diet may account for the reduced resistance.