Development of new screening techniques to assess bioavailability of soy isoflavones: use of a hamster model and genomic techniques to identify human fecal microorganisms associated with isoflavone disappearance

Isoflavones are found almost exclusively in soybeans and soy products. They have been extensively studied for improving health. Better understanding isoflavones bioavailability is also essential compared to their metabolism. Two aspects of isoflavone bioavailability were investigated in this project;Golden Syrian hamsters were investigated to attempt validating this model as relevant to humans for isoflavones bioavailability and their cholesterol lowering effect. Differences between sex (females\u3emales) and isoflavone (genistein\u3edaidzein), similar patterns of urinary excretion between females and women and clustering of animals as high excreters/low degraders and low excreters/high degraders for daidzein and genistein were features shared with humans that may validate hamsters as a model to study isoflavones bioavailability. Cecal but not fecal in vitro daidzein and genistein degradation rates were correlated with urinary excretion levels. Finally, high daidzein, genistein and total isoflavone urinary excretion was associated with lower levels of total cholesterol compared to low excretion;To identify human fecal bacterial species influencing isoflavone disappearance, polymerase chain reaction and denaturing gradient gel electrophoresis allowed qualitative and significantly quantitative profiling of fecal microbial profiles based on each strain\u27s 16S DNA. When comparing gut microbial profiles to in vitro fecal isoflavones disappearance, 7 bands of interest were identified when focusing on intra-individual variability of fecal glycitein degradation over a one month interval. Screening of 33 subjects gave 5 bands of greater intensity in the 4 highest compared to the 4 lowest glycitein degraders, 5 bands for genistein and no bands for daidzein. Sequencing and identification of microorganisms using Basic Local Alignment Search Tool gave matches to Bacteroides, Prevotella and Clostridium species. These strains were investigated using a fecal suspension matrix where nutrient availability was rich (attempting to mimic rapid gut transit time and low degradation rate) or poor (long gut transit time; high degradation rate). Species increasing significantly isoflavones disappearance in both media were B. acidifaciens, T. forsythensis, P. pallens, B. uniformis, E. ramulus and C. orbiscindens. These species were hypothesized to be present all individuals with greater proportions of these strains in high versus low degraders, as reflected by DGGE analysis

Lesser in vitro anaerobic cecal isoflavone disappearance was associated with greater apparent absorption of daidzein and genistein in Golden Syrian hamsters

Our hypothesis in this study was that in vitro disappearance of isoflavones from fecal or cecal contents of Golden Syrian hamsters paralleled the apparent absorption of these compounds, comparable with previous findings from in vitro human fecal incubations. Two studies were conducted to test this idea: one on in vitro fecal (study 1, n = 20/sex) and the other on in vitrocecal contents (study 2, n = 10/sex) ability to degrade isoflavones. According to HPLC analysis, urinary isoflavone excretion was significantly less by 2–4 fold in males compared with females in both studies. Fecal isoflavone excretion was not significantly different between sexes orisoflavones (study 1) and was In vitro anaerobic fecal isoflavonedegradation rate constants from study 1 were minimal with no significant correlation between urinary and fecal isoflavone excretion. However, in vitro anaerobic cecal isoflavone degradation rate constants (study 2) were greater and significantly correlated with urinary excretion ofdaidzein (R = 0.90; p = 0.01) and genistein (R = 0.93; p = 0.004), but not glycitein (R = 0.50; p = 0.3). Both male and female hamsters showed a pattern of urinary isoflavone excretion similar to that found in humans (daidzein \u3e genistein). Hamster in vitro cecal isoflavone degradation rate constants seemed to be analogous to human in vitro fecal isoflavone degradation rate constants for genistein and daidzein. The sex difference in isoflavone excretion in hamsters and the instability in glycitein excretion across studies coupled with the paucity of human data on thisisoflavone deserve further investigation

Conjugate gradient type algorithms for frictional multi-contact problems: applications to granular materials

International audienceThis paper presents gradient type algorithms to solve frictional multi contact problems written as quasi optimization problems. A single loop scheme formally close to the classical conjugate gradient method is proposed with some adap tations of the iterate corrections and gradient projections. Since the convergence is difficult to prove, various tests in the field of granular media are performed with comparison with the non linear Gauss Seidel scheme

On inconsistency in frictional granular systems

International audienceNumerical simulation of granular systems is often based on a discrete element method. The nonsmooth contact dynamics approach can be used to solve a broad range of granular problems, especially involving rigid bodies. However, difficulties could be encountered and hamper successful completion of some simulations. The slow convergence of the nonsmooth solver may sometimes be attributed to an ill-conditioned system, but the convergence may also fail. The prime aim of the present study was to identify situations that hamper the consistency of the mathematical problem to solve. Some simple granular systems were investigated in detail while reviewing and applying the related theoretical results. A practical alternative is briefly analyzed and tested

Numerical investigations of fault propagation and forced-fold using a non smooth discrete element method

Geophysical problems as forced-fold evolution and fault propagation induce large deformations and many localisation. The continuum mechanics does not seem the more appropriate for their description and it appears more interesting to represent the media as initially discontinuous. To face both phenomena, a non smooth Discrete Element Method is used. Geophysical structures are considered as collection of rigid disks which interact by cohesive frictional contact laws. Numerical geophysical formations are correlated to mechanical properties of structures through observation and mechanical analysis.Les problèmes géophysiques tels que l’évolution des plis et la propagation de failles induisent de grandes déformations et de nombreuses localisations. Il apparaît donc difficile de décrire le problème avec les outils de la mécanique des milieux continus, et il est donc preferable de représenter la structure comme initialement divisée. Ces deux phénomènes sont étudiés via une approche non régulière par éléments discrets. Les structures géologiques sont considérées comme des collections de particules dont les interactions répondent à des lois de contact cohésif frottant. Les observations des structures géophysiques numériques sont corrélées aux propriétés des structures au travers d’une analyse mécanique

A parallel version of the non smooth contact dynamics algorithm applied to the simulation of granular media

AbstractThe NSCD method has shown its efficiency in the simulation of granular media. Since the number of particles and contact increases, the shape of the discrete elements becomes more complicated and the simulated problems becomes more complex, the numerical tools need to be improved in order to preserve reasonable elapsed CPU time. In this paper we present a parallelization approach of the NSCD algorithm and we investigate its influence on the numerical behaviour of the method. We illustrate the efficiency on an example made of hard disks: a free surface compaction

A local multi-physical approach to model braking materials

International audienceLocal investigations are managed to understand the multi-physical complexity of braking materials. After a determination of the Representative Elementary Volume, measures of friction, damage and temperature are related to global solicitations and the deceleration. The impact of wear on the different equilibrium is also presented

Euler-like modelling of dense granular flows: application to a rotating drum

General conservation equations are derived for 2D dense granular flows from the Euler equation within the Boussinesq approximation. In steady flows, the 2D fields of granular temperature, vorticity and stream function are shown to be encoded in two scalar functions only. We checked such prediction on steady surface flows in a rotating drum simulated through the Non-Smooth Contact Dynamics method. This result is non trivial because granular flows are dissipative and therefore not necessarily compatible with Euler equation. Finally, we briefly discuss some possible ways to predict theoretically these two functions using statistical mechanics

Tribological Analysis of Bolted Joints Submitted to Vibrations

International audienceAn experimental approach was adopted to understand service damages such as crack initiation and surface degradation of bolted joints used in the junction technology of aircraft air bleed valve systems. A vibratory testing stage combined to Digital Image Correlation (DIC) focus on an experimental model device of valve body/actuator body junction. DIC coupled with in situ tribological observations and a Finite Element Model (FEM) has been used to identify more clearly local contact conditions. This approach has enlightened peeling-off and micro-slips instabilities under vibratory loadings, leading to third body formation in bolted joints contacts. The morphology of such third body is placed at the focus of damages observed in involved air bleed valve systems

Space grease lubrication modeling: A discrete element approach

International audienceThe tribological behavior of space grease is investigated with the Discrete Element Method. In the first step, the grease is described as a collection of particles of two kinds (oil and PTFE) in interaction. The development of the Grease Discrete Element Model (GDEM) used here, is based on rheometer-like characterizations. In the second step, the GDEM is subjected to tribometer-like conditions to investigate grease flow mechanisms and the role of the thickener (PTFE) in lubrication. The tribological behavior of grease seems to be controlled by the coupled influence of both granulometric (thickener particle sizes) and physico-chemical (interaction law) parameters. These results provide the starting point for identifying the parameters on which to act to reformulate greases