Short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate are secondary metabolites produced by anaerobic fermentation of dietary fibers in the intestine. Intestinal SCFAs exert various beneficial effects on intestinal homeostasis, including energy metabolism, autophagy, cell proliferation, immune reaction, and inflammation, whereas contradictory roles of SCFAs in the oral cavity have been reported. Herein, we found that low and high concentrations of SCFAs induce differential regulation of intracellular Ca2+ mobilization and expression of pro-inflammatory cytokines, such as interleukin (IL)-6 and IL-8, respectively, in gingival fibroblast cells. Additionally, cell viability was found to be differentially regulated in response to low and high concentrations of SCFAs. These findings demonstrate that the physiological functions of SCFAs in various cellular responses are more likely dependent on their local concentration.

The effects of dietary β-glucan, obtained from bacterial fermentation, on the intestinal mass, short chain fatty acids, lactate production and pH in Sprague-Dawley (SD) rats were evaluated. SD rats fed with 0% (control group), 1% or 5% β-glucan supplemented diets (w/w) for 3 weeks. The presence of β-glucan in the diets resulted in a significant increase in colonic contents in a dose dependent manner. The amount of short chain fatty acids increased in rats fed β-glucan diets. Rats fed the 5% β-glucan diets had higher levels of acetate, propionate and butyrate by 1.8, 1.7 and 3.0 fold of the control group in the cecum, and 2.2, 2.9 and 3.1 fold of the control group in the colon, respectively. The β-glucan diets also significantly increased the levels of cecal and colonic lactate by 1.4~3.4 fold, when compared to the control diet, indicating that dietary β-glucan stimulated the growth of lactic acid bacteria within the intestine. These results suggest that dietary β-glucan, by providing short chain fatty acids and reducing the cecal and colonic pH, may be beneficial in improving gut health, and provide evidence for the use of β-glucan as a dietary supplement for human consumption.

Macrophages play an important role in both the innate and adaptive immune responses. These include phagocytosis, killing of microorganisms, antigen presentation, and induction of immune cytokines and antimicrobial genes. Macrophage activity is reported to be controlled by diverse exogenous antigenic or endogenous metabolic molecules, and the underlying mechanisms are well documented in human and mouse macrophage cells. Bacterial lipopolysaccharide (LPS) is known to be one of the most potent stimuli activating macrophages through the toll like receptor 4 (TLR4) signaling pathway. There are other antigenic molecules, such as muramyl dipeptide (MDP) and outer membrane protein A (OmpA), that are also known to activate immune cells. On the other hand, short chain fatty acids (SCFAs) such as acetate and butyrate are produced by gut microbiota and control host energy metabolism and signal transduction through GPR receptors. However, there are few studies demonstrating the effects of these molecules in macrophages from domestic animals, including domestic pigs. In this study, we attempted to characterize gene expression regulation in porcine macrophages (PoM2, Pig Monocytes clone 2) following treatment with LPS, MDP, OmpA, and two short chain fatty acids using porcine genome microarray and RT-PCR techniques. A number of novel porcine genes, including anti-microbial peptides and others, appeared to be regulated at the transcriptional level. Our study reports novel biomarkers such as SLC37A2, TMEN184C, and LEAP2 that are involved in the porcine immune response to bacterial antigen LPS and two short chain fatty acids.