Dietary polyphenols are components of many foods such as tea, fruit, and vegetables and are associated with several beneficial health effects although, so far, largely based on epidemiological studies. The intact forms of complex dietary polyphenols have limited bioavailability, with low circulating levels in plasma. A major part of the polyphenols persists in the colon, where the resident microbiota produce metabolites that can undergo further metabolism upon entering systemic circulation. Unraveling the complex metabolic fate of polyphenols in this human superorganism requires joint deployment of in vitro and humanized mouse models and human intervention trials. Within these systems, the variation in diversity and functionality of the colonic microbiota can increasingly be captured by rapidly developing microbiomics and metabolomics technologies. Furthermore, metabolomics is coming to grips with the large biological variation superimposed on relatively subtle effects of dietary interventions. In particular when metabolomics is deployed in conjunction with a longitudinal study design, quantitative nutrikinetic signatures can be obtained. These signatures can be used to define nutritional phenotypes with different kinetic characteristics for the bioconversion capacity for polyphenols. Bottom-up as well as top-down approaches need to be pursued to link gut microbial diversity to functionality in nutritional phenotypes and, ultimately, to bioactivity of polyphenols. This approach will pave the way for personalization of nutrition based on gut microbial functionality of individuals or populations.polyphenol bioconversion | gut microbiota | metabolomics | metagenomics | microbiomics

No abstract

Current research increasingly recognizes the human gut microbiome as a metabolically versatile biological 'digester' that plays an essential role in regulating the host metabolome. Gut microbiota recover energy and biologically active molecules from food that would otherwise be washed out of the intestinal tract without benefit. In this study, a protocol for NMR-based metabolite profiling has been developed to access the activity of the microbiome. The physicochemical properties of fecal metabolites have been found to strongly affect the reproducibility and coverage of the profiles obtained. Metabolite profiles generated by water and methanol extraction of lyophilized feces are reproducible and comprise a variety of different compounds including, among others, short-chain fatty acids (e.g. acetate, propionate, butyrate, isobutyrate, isovalerate, malate), organic acids (e.g. succinate, pyruvate, fumarate, lactate), amino acids, uracil, trimethylamine, ethanol, glycerol, glucose, phenolic acids, cholate, and lipid components. The NMR profiling approach was validated on fecal samples from a double-blinded, placebo-controlled, randomized cross-over study, in which healthy human subjects consumed a placebo and either a grape juice extract or a mix of grape juice and wine extract over a period of 4 weeks, each. The considerable inter- and intra-individual variability observed originates in the first instance from variable metabolite concentrations rather than from variable metabolite compositions, suggesting that different colonic flora share general biochemical characteristics metabolizing different substrates to specific metabolic patterns. Whereas the grape juice extract did not induce changes in the metabolite profiles as compared with the placebo, the mixture of grape juice and wine extract induced a reduction in isobutyrate, which may indicate that polyphenols are able to modulate the microbial ecology of the gut.

Pin1 is a peptidyl-prolyl cis/trans isomerase (PPIase) essential for cell cycle regulation. Pin1-catalyzed peptidyl-prolyl isomerization provides a key conformational switch to activate phosphorylation sites with the common phospho-Ser/Thr-Pro sequence motif. This motif is ubiquitously exploited in cellular response to a variety of signals. Pin1 is able to bind phospho-Ser/Thr-Procontaining sequences at two different sites that compete for the same substrate. One binding site is located within the N-terminal WW domain, which is essential for protein targeting and localization. The other binding site is located in the C-terminal catalytic domain, which is structural homologous to the FK506-binding protein (FKBP) class of PPIases. A flexible linker of 12 residues connects the WW and catalytic domain. To characterize the structure and dynamics of full-length Pin1 in solution, high resolution NMR methods have been used to map the nature of interactions between the two domains of Pin1. In addition, the influence of target peptides on domain interactions has been investigated. The studies reveal a dynamic picture of the domain interactions.15 N spin relaxation data, differential chemical shift mapping, and residual dipolar coupling data indicate that Pin1 can either behave as two independent domains connected by the flexible linker or as a single intact domain with some amount of hinge bending motion depending on the sequence of the bound peptide. The functional importance of the modulation of relative domain flexibility in light of the multitude of interaction partners of Pin1 is discussed. Most peptidyl-prolyl cis/trans isomerases (PPIase)1 play an important role during protein folding by catalyzing the cis/ trans isomerization of peptidyl-prolyl imide bonds (1-4). Recently, with the discovery of the parvulin class of PPIases, peptidyl-prolyl isomerization has been identified as a key step in cell cycle regulation, oncogenesis, signal transduction, and a multitude of other cellular processes. Pin1 is the best-characterized PPIase of the parvulins and selectively catalyzes cis/ trans isomerization of peptide sequences containing the phospho-Ser/Pro or phospho-Thr/Pro motif (pS/T-P) (5-7). Lu et al.(5) have proposed that, in the presence of certain kinases, Pin1 participates in a "tag and twist" mechanism to activate its substrate: the kinase phosphorylates the serine or threonine side chain (tagging), and Pin1 subsequently cis/trans isomerizes (twists) the peptide bond preceding proline in a di-peptide pS/T-P, thus introducing a marked kink in the backbone of the peptide chain.Substrates of Pin1 include the mitotic regulators (Cdc25 phosphatase (8) and NIMA (9), PLK I, Wee, and Myt1 kinases); several transcription factors like ␤-catenin, c-Jun, and the tumor suppressor protein p53 (10 -12); and some specific proteins like the RNA polymerase II, the cytoskeleton protein tau, and the G 1 /S protein cyclin D1 (13, 14).Pin1 is a two-domain protein of 18.4 kDa consisting of an N-terminal WW domain (Pin1 WW ) important for...