Experimental Determination of the Threshold Dose for Bifidogenic Activity of Dietary 1-Kestose in Rats

Targeting gut microbiota-derived butyrate improves hepatic gluconeogenesis through the cAMP-PKA-GCN5 pathway in late pregnant sows

Short chain fatty acids (SCFAs) produced by gut microbiota affected hepatic glucose metabolism via the gut-liver axis. The present study aimed to investigate the effects of butyrate produced by gut microbiota on hepatic gluconeogenesis in late-pregnancy sows. A total of 240 primiparous sows in late pregnancy were tested for blood glucose using a glucose meter before feeding and grouped according to their blood glucose level as follows: 0-3.0 mmol L^-1 (low blood glucose group, LG group) and 3.1-5.0 mmol L^-1 (normal blood glucose group, NG group). Colonic SCFAs and microbiota, SCFAs in the portal vein and liver, and acetylation and phosphorylation levels in the liver samples were analyzed. Hepatocytes from pregnant sows were examined for the effect of butyrate on hepatic glucose gluconeogenesis. In vivo experiments showed that the reproductive performance, serum glucose metabolism index, colonic butyrate and butyrate-producing bacteria decreased in the LG group compared with the NG group. Correlation analysis found a positive correlation among colonic butyrate, butyrate-producing bacteria and the serum glucose metabolism index. Moreover, the hepatic cAMP concentration, PKA activity, GCN5 phosphorylation, and the expression of G6P and PEPCK were decreased and PGC1-α acetylation was increased in the LG group compared with the NG group. In vitro, sodium butyrate significantly stimulated the cAMP concentration, PKA activity, GCN5 phosphorylation, and the expression of G6P and PEPCK and inhibited PGC-1α acetylation in the LG group of hepatocytes from late-pregnancy sows. Interestingly, another in vivo experiment showed that dietary 1-kestose, a natural regulator of gut bacteria, significantly increased butyrate and butyrate-producing bacteria, and improved the reproductive performance and serum glucose metabolism index in late-pregnancy sows. Taken together, we found that targeting gut microbiota-derived butyrate could improve hepatic gluconeogenesis through the cAMP-PKA-GCN5 pathway in late-pregnancy sows.

Consumption of indigestible saccharides and administration of Bifidobacterium pseudolongum reduce mucosal serotonin in murine colonic mucosa

SCFA increase serotonin (5-hydroxytryptamine, 5-HT) synthesis and content in the colon in vitro and ex vivo, but little is known in vivo. We tested whether dietary indigestible saccharides, utilised as a substrate to produce SCFA by gut microbiota, would increase colonic 5-HT content in mice. Male C57BL/6J mice were fed a purified diet and water supplemented with 4 % (w/v) 1-kestose (KES) for 2 weeks. Colonic 5-HT content and enterochromaffin (EC) cell numbers were lower in mice supplemented with KES than those without supplementation, while monoamine oxidase A activity and mRNA levels of tryptophan hydroxylase 1 (Tph1), chromogranin A (Chga), Slc6a4 and monoamine oxidase A (Maoa) genes in the colonic mucosa, serum 5-HT concentration and total 5-HT content in the colonic contents did not differ between groups. Caecal acetate concentration and Bifidobacterium pseudolongum population were higher in KES-supplemented mice. Similar trends were observed in mice supplemented with other indigestible saccharides, that is, fructo-oligosaccharides, inulin and raffinose. Intragastric administration of live B. pseudolongum (108 colony-forming units/d) for 2 weeks reduced colonic 5-HT content and EC cell numbers. These results suggest that changes in synthesis, reuptake, catabolism and overflow of 5-HT in the colonic mucosa are not involved in the reduction of colonic 5-HT content by dietary indigestible saccharides in mice. We propose that gut microbes including B. pseudolongum could contribute to the reduction of 5-HT content in the colonic mucosa via diminishing EC cells.

Insight into the effects and biotechnological production of kestoses, the smallest fructooligosaccharides

Kestoses, the smallest fructooligosaccharides, are trisaccharides composed of a fructose molecule and a sucrose molecule linked by either β-(2,1) or β-(2,6) linkage. 1-kestose, 6-kestose and neokestose are the three types of kestoses occurring in nature. As the main kind of fructooligosaccharide, kestoses share similar physiological effects with other fructooligosaccharides, and they have recently been determined to show more notable effects in promoting the growth of probiotics including Faecalibacterium prausnitzii and Bifidobacterium than those of other fructooligosaccharides. Kestoses exist in many plants, but the relatively low content and the isolation and purification are the main barriers limiting their industrial application. The production of kestoses by enzymatic biosynthesis and microbial fermentation has the potential to facilitate its production and industrial use. In this article, the recent advances in the research of kestoses were overviewed, including those studying their functions and production. Kestose-producing enzymes were introduced in detail, and microbial production and fermentation optimization techniques for enhancing the yield of kestoses were addressed. β-Fructofuranosidase is the main one used to produce kestoses because of the extensive range of microbial sources. Therefore, the production of kestoses by microorganisms containing β-fructofuranosidase has also been reviewed. However, few molecular modification studies have attempted to change the production profile of some enzymes and improve the yield of kestoses, which is a topic that should garner more attention. Additionally, the production of kestoses using food-grade microorganisms may be beneficial to their application in the food industry.

Intestinal microbiota transplantation reveals the role of microbiota in dietary regulation of RegIIIβ and RegIIIγ expression in mouse intestine

RegIIIβ and RegIIIγ are antimicrobial peptides expressed in intestinal epithelial cells. Expression of these peptides is reportedly decreased by high-fat diet (HFD) and increased by indigestible oligosaccharides in mice. Clearly, these dietary regimens change the structure of intestinal microbiota. We employed an intestinal microbiota transplantation (IMT) to test whether diet-induced changes in the expression of these peptides are mediated by gut microbiota. C57BL/6J mice were fed either a normal-fat diet (NFD), a HFD, or a NFD supplemented with or without 1-kestose (KES), an indigestible oligosaccharide. Ileal RegIIIβ and RegIIIγ mRNA levels were lower in mice receiving IMT from HFD-fed mice than in those receiving NFD-fed mice and higher in mice receiving IMT from KES-supplemented mice than in those receiving the mice without KES supplementation. Western blot analysis showed that serum RegIIIβ levels changed in parallel with the ileal mRNA levels. We propose that HFD- and KES-induced changes in the ileal RegIIIβ and RegIIIγ expression and in the circulating RegIIIβ levels are mediated, at least in part, by intestinal microbiota.

Comment on Experimental Determination of the Threshold Dose for Bifidogenic Activity of Dietary 1-Kestose in Rats. Foods 2020, 9, 4

Currently, our group is undertaking a program trying to evaluate the bifidogenic effect/activity of different prebiotics and their dose-effect relationships [...]