Dietary psyllium fiber increases intestinal heat shock protein 25 expression in mice

Heat shock proteins (HSPs) protect intestinal epithelial cell function, integrity and viability against many forms of stress. We hypothesized that dietary fibers (DFs) in the diet may increase HSP expression, since DFs are known to exhibit beneficial effects on intestinal health. The present study investigated the regulation of intestinal HSP expression by DFs, particularly psyllium fiber. Feeding psyllium fiber for 5 d increased HSP25 expression, but not HSP32 and HSP70 expression in the jejunum, ileum, and colon of mice at both the protein and mRNA levels. The increases in HSP25 expression did not correlate with cecal organic acid production by microbial fermentation. The water-insoluble fraction of psyllium fiber largely contributed to the induction of HSP25 expression, but feeding with other water-insoluble DFs from beet, wheat, and oats failed to induce intestinal HSP25 expression. Although the water-holding capacity of psyllium fiber was much higher than those of the other water-insoluble DFs examined, the increase in HSP25 expression induced by feeding polycarbophil, which possesses a high water-holding capacity similar to that of psyllium fiber, was much lower than that induced by psyllium fiber. Finally, induction of malondialdehyde production by hydrogen peroxide, an oxidant, in the colon of mice fed psyllium fiber was lower than that in mice fed with the control diets. Taken together, feeding psyllium fiber, especially the water-insoluble fraction, increases intestinal HSP25 expression and suppresses oxidant-induced malondialdehyde production.