Effect of Bean-Derived Soluble Dietary Fibers on Macrophage Function In Vitro

Studies have shown that dietary fibers have many health benefits. Soluble dietary fibers (SDF) extracted from wheat, corn, rice, or several herbaceous plants have been shown to have either pro- or anti-inflammatory effects depending on the mode of preparation of the fibers, the fibers' structures and the biological or cellular context. However, much less is known regarding the immunomodulatory properties of dry bean-derived SDF. The goal of this study was to fill this gap in knowledge. Using RAW 264.7 macrophages, we show that dry bean-derived SDF stimulated the production of nitric oxide (NO), tumor necrosis factor (TNF) α, interleukin (IL)-1β and IL-6. We show that these changes were partly dependent on toll-like receptor TLR-4 signaling. More importantly, we observed that the levels of NO, TNF-α, IL-1β and IL-6 were significantly lower when the SDF were extracted from heat-processed bean flour. Overall, our results demonstrate that dry bean-derived SDF-rich fractions modulate macrophage activation in vitro, promoting a pro-inflammatory response that is partially mediated by TLR-4 signaling.