Tryptamine, a Microbial Metabolite in Fermented Rice Bran Suppressed Lipopolysaccharide-Induced Inflammation in a Murine Macrophage Model

Abstract

Fermentation is thought to alter the composition and bioavailability of bioactive compounds in rice bran. However, how this process affects the anti-inflammatory effects of rice bran and the bioactive compounds that might participate in this function is yet to be elucidated. This study aimed to isolate bioactive compounds in fermented rice bran that play a key role in its anti-inflammatory function. The fermented rice bran was fractionated using a succession of solvent and solid-phase extractions. The fermented rice bran fractions were then applied to lipopolysaccharide (LPS)-activated murine macrophages to evaluate their anti-inflammatory activity. The hot water fractions (FRBA), 50% ethanol fractions (FRBB), and n-hexane fractions (FRBC) were all shown to be able to suppress the pro-inflammatory cytokine expression from LPS-stimulated RAW 264.7 cells. Subsequent fractions from the hot water fraction (FRBF and FRBE) were also able to reduce the inflammatory response of these cells to LPS. Further investigation revealed that tryptamine, a bacterial metabolite of tryptophan, was abundantly present in these extracts. These results indicate that tryptamine may play an important role in the anti-inflammatory effects of fermented rice bran. Furthermore, the anti-inflammatory effects of FRBE and tryptamine may depend on the activity of the aryl hydrocarbon receptor.

Fermented Rice Bran Supplementation Inhibits LPS-Induced Osteoclast Formation and Bone Resorption in Mice

“…It has been reported that feeding FRBs increased the amount of short-chain fatty acids in the intestine and suppressed enteritis in a colitis model via GRP43 [33]. It has also been reported that tryptophan, which is relatively abundant in FRB, is metabolized by intestinal bacteria to tryptamine and other indole compounds, which act as ligands for aryl hydrocarbon receptors (AHRs) and exhibit anti-inflammatory effects [38,49]. Thus, there is a possibility that FRB ingestion may have a postbiotic effect, in which metabolites by intestinal bacteria have a beneficial effect on the host.…”

“…Double fermentation increases the microbial tryptophan metabolites and the concentration of tryptophan in RB [33]. In recent years, it has been reported that tryptamine, one of FRB's components, inhibited LPS-induced inflammation in a mouse macrophage model [38]. This change in nutritional status may contribute to the anti-inflammatory effects of FRB.…”

Modulation of immunity by tryptophan microbial metabolites

“…Similarly, indole-3-methanol suppressed the generation of LPS-mediated inflammatory cytokines such as IL-6 in bone marrow-derived macrophages (BMM) of mice (180). Tryptamine decreased the mRNA expression levels of IL-7 and IL-6 in LPS-stimulated RAW 6.264 cells via AHR (175,181). Microbial Trp metabolite ligands of AhR affect the metabolic and immunomodulatory processes of nonspecific immune cells.…”

Bioactive amines in non-conventional edible plants from Brazil: health benefits and concerns

“…2-Phenylethylamine (PHM) induces pleasurable sensations, improving mood and protecting against neurodegenerative diseases and depression [23]. Tryptamine (TRM) acts as a neurotransmitter and exhibits antioxidant properties [24] and anti-in ammatory effects by suppressing lipopolysaccharide-induced in ammation in a murine macrophage model [25].…”