The influence of oxygen on the metabolites of phenolic blueberry extract and the mouse microflora during in vitro fermentation.

The elevated intestinal oxygen in certain unhealthy conditions (e.g., mucosa injury) enhances the expansion of aerobic/facultative anaerobic bacteria (mainly Proteobacteria) in gut microbiota (GM) and is strongly linked to various diseases. The alteration of GM, influenced by oxygen, may affect the bioavailability of dietary polyphenols. In vitro digestion, dialysis and fermentation of phenolic blueberry extract (BE) were performed here using the GM of mice under different oxygen conditions. Oxygen delayed the degradation of the main phenolic components, including quercetin, kaempferol and their rutinose-conjugates, in BE during in vitro fermentation. In addition, the metabolites of BE were also influenced by oxygen. Oxygen skewed the production of 3-hydroxyphenylacetatic acid to 4-hydroxyphenylacetatic acid. Moreover, oxygen also blunted hippuric, 3-phenylpropionic, and 3-hydroxycinnamic acids production. Furthermore, oxygen enhanced the expansion of Salmonella and Escherichia belonging to phylum Proteobacteria and suppressed the proliferation of the anaerobic bacteria Clostridium and Bacteroides belonging to phyla Firmicutes and Bacteroidetes, respectively, which was reversed by BE supplementation.

Grape Extract Activates Brown Adipose Tissue Through Pathway Involving the Regulation of Gut Microbiota and Bile Acid.

SCOPE: Although the physiological function of grape extract (GE) has long been recognized, the precise mechanism remains obscure. This study is designed to investigate the effects of GE on metabolism and the association between GE activation of brown adipose tissue (BAT) and the restoration of gut microbiota (GM). METHODS AND RESULTS: Diet-induced obese mice are used to investigate the function of GE. GE administration increases energy metabolism and prevents obesity. Also, GE restores the dysbiosis of GM by augmenting the observed species, enhancing the Firmicutes-to-Bacteroidetes ratio and increasing the abundance of the Bifidobacteria, Akkermansia, and Clostridia genera. This restoration of GM alters the bile acid (BA) pool in the serum. The abundance of Akkermansia, Clostridium, and Bifidobacterium is negatively correlated with the concentrations of TαMCA, TßMCA, and TCA but is positively correlated with DCA. The changes in BA promoted TGR5 in BAT, which contributed to thermogenesis. The metabolites of GE in blood do not stimulate TGR5 in vitro. CONCLUSION: GE stimulates the thermogenesis of BAT through a pathway involving the regulation of GM and BA in diet-induced obese mice. This study reveals the mechanism by which dietary polyphenols promote thermogenesis by regulating BA, which is altered by GM.

A fast and accurate way to determine short chain fatty acids in mouse feces based on GC-MS.

Short-chain fatty acids (SCFAs) in the gut are mainly produced by the anaerobic microbial fermentation of unabsorbed dietary carbohydrates in the large bowel. Quantitative determinations of SCFAs in feces and colonic contents are necessary when studying the impact of fiber-rich food (such as fruits and vegetables) on health. We made the following crucial improvements to the method currently widely used: optimized the lyophilization period from 12 h to 3.5 h; disposed of the procedure for precise weight control; lowered the extraction temperature from 25 °C to 4 °C; shortened the extraction time from 45 min to 15 min; and significantly improved the extraction efficiency of acetic acid, propionic acid and butyric acid by 12.91%, 19.95% and 13.08%, respectively. Furthermore, to evaluate the applicability of this novel approach, we applied our method to determine the SCFAs in the feces and colonic contents of mice fed on different diets, and observed distinct results.

Vanillic acid activates thermogenesis in brown and white adipose tissue.

Anthocyanins have a positive effect on resistant obesity; however they cannot usually be absorbed directly but, instead, are metabolized by gut microbiota. This study will examine the effects and the mechanism of vanillic acid on the prevention of obesity induced by diet, which is one of the anthocyanin metabolites. We fed C57BL/6J mice vanillic acid supplements in a high fat and high fructose diet for 16 weeks. Body weight, fat pat weight, and food and water intake were monitored. Glucose homeostasis was assessed with a glucose or insulin tolerance test. The sizes of adipose cells and lipid droplets were analyzed by histology staining, while the expression of genes and proteins was analyzed by quantitative real-time PCR, western blot and tissue-blot immunoassay. The results demonstrated that vanillic acid contributed to the reduction of body weight gain, improved glucose tolerance and insulin resistance, and maintained body temperature. Furthermore, vanillic acid was found to promote thermogenesis and mitochondrial synthesis of brown adipose tissue and inguinal white adipose tissue. This study demonstrated that vanillic acid could prevent obesity by activating BAT thermogenesis and the promotion of inguinal WAT browning.