Fiber-rich diets alter rat intestinal leukocytes metabolism

This study addressed the following question: What is the effect of fermentable and nonfermentable fiber-rich diets on intestinal immune cells' function and metabolism? For this purpose, weaning rats received, for 8 weeks, two types of fiber-enriched (30%) diets with different fermentable/nonfermentable fiber ratios, that is, oat bran (0.3) and wheat bran (0.14). The results of these two experimental groups were compared with those of the low-fiber control group having a 0.22 fermentable/nonfermentable fiber ratio. The total number and proportion of leukocytes in plasma, total number of cells in the lymphoid organs, lymphocyte proliferative activity and capacity of phagocytosis, hydrogen peroxide production, and adherence of macrophages were investigated. The activities of key enzymes of glycolysis and glutaminolysis, and of the Krebs cycle of lymphocytes from the mesenteric lymph nodes and macrophages from the intraperitoneal cavity were determined. The metabolic response of lymphocytes and macrophages from rats fed the three diets to Bacillus Calmette-Guérin-stimulus was also investigated. The number of lymphocytes in the mesenteric lymph nodes was lower in both fiber-rich diets than in the control but did not have any difference in the remaining lymphoid organs. Wheat bran caused a significant reduction in the phagocytosis capacity and adherence index of macrophages, whereas oat bran did not have a significant effect. The response of glucose and glutamine metabolism to Bacillus Calmette-Guérin-stimulus was not altered by the diets in lymphocytes, whereas in macrophages, the increase in glutaminase and hexokinase activities was abolished.