Louise Cantlay

Major phenylpropanoid‐derived metabolites in the human gut can arise from microbial fermentation of protein

SCOPE Plant secondary metabolites, such as phenolic acids are commonly associated with benefits for human health. Two of the most abundant phenylpropanoid-derived compounds detected in human faecal samples are phenylacetic acid (PAA) and 4-hydroxylphenylacetic acid (4-hydroxyPAA). Although they have the potential to be derived from diets rich in plant-based foods, evidence suggests that these compounds can be derived from the microbial fermentation of aromatic amino acids (AAAs) in the colon. METHODS AND RESULTS To identify the bacteria responsible, 26 strains representing 25 of the dominant human colonic species were screened for phenyl metabolite formation. Seven strains produced significant amounts of both PAA and 4-hydroxyPAA. These included five out of seven Bacteroidetes (Bacteroides thetaiotaomicron, Bacteroides eggerthii, Bacteroides ovatus, Bacteroides fragilis, Parabacteroides distasonis), and two out of 17 Firmicutes (Eubacterium hallii and Clostridium bartlettii). These species also produced indole-3-acetic acid (IAA), the corresponding tryptophan metabolite, but C. bartlettii showed 100 times higher IAA production than the other six strains. Four strains were further tested and PAA formation was substantially increased by phenylalanine, 4-hydroxyPAA by tyrosine and IAA by tryptophan. CONCLUSION This study demonstrates that certain microbial species have the ability to ferment all three AAAs and that protein fermentation is the likely source of major phenylpropanoid-derived metabolites in the colon.

Alperujo extract, hydroxytyrosol, and 3,4‐dihydroxyphenylglycol are bioavailable and have antioxidant properties in vitamin E‐deficient rats—a proteomics and network analysis approach

SCOPE Olive products are rich in phenolic compounds, which are natural antioxidants in vitro. We tested the in vivo effects of alperujo, an olive production by-product, as well as hydroxytyrosol and 3,4-dihydroxyphenylglycol (DHPG) isolated from alperujo, on indices and pathways of oxidative and metabolic stress in a vitamin E-deficient rat model. METHODS AND RESULTS Rats were fed a vitamin E-deficient diet for 10 weeks, followed by this diet supplemented with either 100 mg/kg diet dα-tocopherol, alperujo extract, hydroxytyrosol, or 10 mg/kg diet DHPG, for a further 2 weeks. We detected alperujo phenolics in tissues and blood, indicating they are bioavailable. Alperujo extract partially ameliorated elevated plasma levels of thiobarbituric acid reactive substances and also lowered plasma cholesterol levels, whereas hydroxytyrosol increased plasma triglyceride levels. Proteomics and subsequent network analysis revealed that hepatic mitochondrial aldehyde dehydrogenase (ALDH2), of which protein and activity levels were regulated by dα-tocopherol and olive phenolics, represents a novel central regulatory protein hub affected by the dietary interventions. CONCLUSION The in vivo free radical scavenging properties of olive phenolics appear relatively modest in our model. But alternative mechanisms, including regulation of ALDH2, may represent relevant antioxidant mechanisms by which dietary olive phenolics could have beneficial impact on cardiovascular health.

Expression of Cellulosome Components and Type IV Pili within the Extracellular Proteome of Ruminococcus flavefaciens 007

Background Ruminococcus flavefaciens is an important fibre-degrading bacterium found in the mammalian gut. Cellulolytic strains from the bovine rumen have been shown to produce complex cellulosome structures that are associated with the cell surface. R. flavefaciens 007 is a highly cellulolytic strain whose ability to degrade dewaxed cotton, but not Avicel cellulose, was lost following initial isolation in the variant 007S. The ability was recovered after serial subculture to give the cotton-degrading strain 007C. This has allowed us to investigate the factors required for degradation of this particularly recalcitrant form of cellulose. Methodology/Principal Findings The major proteins associated with the bacterial cell surface and with the culture supernatant were analyzed for R. flavefaciens 007S and 007C grown with cellobiose, xylan or Avicel cellulose as energy sources. Identification of the proteins was enabled by a draft genome sequence obtained for 007C. Among supernatant proteins a cellulosomal GH48 hydrolase, a rubrerthyrin-like protein and a protein with type IV pili N-terminal domain were the most strongly up-regulated in 007C cultures grown on Avicel compared with cellobiose. Strain 007S also showed substrate-related changes, but supernatant expression of the Pil protein and rubrerythrin in particular were markedly lower in 007S than in 007C during growth on Avicel. Conclusions/Significance This study provides new information on the extracellular proteome of R. flavefaciens and its regulation in response to different growth substrates. Furthermore it suggests that the cotton cellulose non-degrading strain (007S) has altered regulation of multiple proteins that may be required for breakdown of cotton cellulose. One of these, the type IV pilus was previously shown to play a role in adhesion to cellulose in R. albus, and a related pilin protein was identified here for the first time as a major extracellular protein in R. flavefaciens.

Ginger phytochemicals mitigate the obesogenic effects of a high‐fat diet in mice: A proteomic and biomarker network analysis

SCOPE Natural dietary anti-obesogenic phytochemicals may help combat the rising global incidence of obesity. We aimed to identify key hepatic pathways targeted by anti-obsogenic ginger phytochemicals fed to mice. METHODS AND RESULTS Weaning mice were fed a high-fat diet containing 6-gingerol (HFG), zerumbone (HFZ), a characterized rhizome extract of the ginger-related plant Alpinia officinarum Hance (high fat goryankang, HFGK) or no phytochemicals (high-fat control, HFC) for 6 wks and were compared with mice on a low-fat control diet (LFC). Increased adiposity in the HFC group, compared with the LFC group, was significantly (p<0.05) reduced in the HFG and HFGK groups without food intake being affected. Correlation network analysis, including a novel residuals analysis, was utilized to investigate relationships between liver proteomic data, lipid and cholesterol biomarkers and physiological indicators of adiposity. 6-Gingerol significantly increased plasma cholesterol but hepatic farnesyl diphosphate synthetase, which is involved in cholesterol biosynthesis was decreased, possibly by negative feedback. Acetyl-coenzyme A acyltransferase 1 and enoyl CoA hydratase, which participate in the β-oxidation of fatty acids were significantly (p<0.05) increased by consumption of phytochemical-supplemented diets. CONCLUSION Dietary ginger phytochemicals target cholesterol metabolism and fatty acid oxidation in mice, with anti-obesogenic but also hypercholesterolemic consequences.

Availability and dose response of phytophenols from a wheat bran-rich cereal product in healthy human volunteers

Scope: Phytophenols present in cereals are metabolised to compounds that could be partly responsible for the reduced risk of chronic diseases and all‐cause mortality associated with fibre‐rich diets. The bioavailability, form and in vivo concentrations of these metabolites require to be established. Materials and methods: Eight healthy volunteers consumed a test meal containing a recommended dose (40 g) and high dose (120 g) of ready‐to‐eat wheat bran cereal and the systemic and colonic metabolites determined quantitatively by LC‐MS. Conclusion: Analysis of the systemic metabolomes demonstrated that a wide range of phytophenols were absorbed/excreted (43 metabolites) within 5 h of consumption. These included 16 of the 21 major parent compounds identified in the intervention product and several of these were also found to be significantly increased in the colon. Not all of the metabolites were increased with the higher dose, suggesting some limitation in absorption due to intrinsic factors and/or the food matrix. Many compounds identified (e.g. ferulic acid and major metabolites) exhibit anti‐inflammatory activity and impact on redox pathways. The combination of postprandial absorption and delivery to the colon, as well as hepatic recycling of the metabolites at these concentrations, is likely to be beneficial to both systemic and gut health.

Identification of damaged proteins in human serum using modified Ehrlich's reagent to target protein-bound pyrroles

Protein-bound pyrroles are a sign of oxidative damage. Here we report a specific method for detecting pyrrole-containing proteins using biotin-labeled Ehrlichs reagent (ER-B). After treatment of either human serum or isolated human serum proteins with various oxidizing agents, damaged, biotin-labeled components could be detected by blotting. Combining the use of ER-B with proteomic techniques allowed human serum proteins susceptible to oxidative damage to be detected and then identified by LC/MS/MS. Identification of such proteins in different human conditions such as obesity, diabetes, and cardiovascular disease should lead to the discovery of new biomarkers and the development of specific assays to monitor health status.