No description available.

No description available.

This study investigated the effects of potassium gluconate (K), calcium carbonate (Ca) and zinc gluconate (Zn) on glycaemic response (GR), energy expenditure (EE) and glycaemic index (GI). At the current time, gastric emptying rate is attributed to GI value alterations - the faster the gastric release compared to the reference food, the higher the blood glucose concentration and therefore the higher the GI of the food. The purpose of this study was to investigate whether faster blood glucose removal from the systemic circulation influences the GR or the GI.

The aims of the present study were 1) to re-assess two existent methods and to increase consistency of kef-estimates, defined as the half maximal constant of the relative rate of carbohydrate oxidation (relCHOox) approximated as a function of blood lactate concentration (BLC) (relCHOox = 100/(l+kelIBLC2), 2) to identificate the fitting models, which adequately described oxygen uptake (V02), carbon dioxide (VC02) and BLC during incremental exercise tests, which allowed 3) to examine the relationship between kef and given indicators of maximal and sub-maximal performance, and 4) to analyse the effect of gender on kel. To address aims 1 to 3, 104 subjects performed an incremental power test with V02, VC02 and BLC measurements. 59 tests provided four or more power increments before the respiratory exchange ratio (RER) reached 1.0. Main findings: 1) kef-approximations excluding stages with RER higher than 1.0 and/or evidence of hyperventilation provided highest kel-estimates (p < 0.01).2) BLC during progressive exercise was more appropriately described as a continuous mono-exponential function whereas V02 and VC02 provided a better fit when a multiple linear threshold responses model was applied. 3) kel was independent of peak performance or intensity at lactate threshold at 2 and 4 mmol•rl or at maximum rate of fat oxidation. However, kel was interrelated (p < 0.01) with cross-over point (equal energy derived from carbohydrate and fat oxidation). To address aim 4, 14 males and 11 females were tested with incremental power tests providing increasing relCHOox at four or more subsequently increasing power stages with an RER< 1.0, kel was independent of gender. Highest kel-approximates after exclusion of stages with RER > 1.0 and/or evidence of hyperventilation suggests underestimation of kef in previous studies. Interrelation between kel and cross-over point intensity supports kel as an indicator of CHO management during exercise, which is independent of peak performance, lactate threshold concepts, maximum fat oxidation and gender.

Dietary intake of a glucosinolate-rich Daikon extract (glucoraphasatin and glucoraphenin) elevated rat hepatic dealkylations of methoxy-, ethoxy-, pentoxyresorufin and benzyloxyquinoline, accompanied by increased expression of CYPl and CYP3A2 apoprotein levels. A marked induction of glutathione S- transferase and quinone reductase activities in liver was evident, as well as of glucuronosyl transferase and epoxide hydrolase activities and expression, but only at higher doses. Lung enzymes were not altered by the same treatment. In precision-cut rat liver slices glucoraphasatin caused a marked increase in epoxide hydrolase activity. Addition of myrosinase to form the isothiocyanate led to a marked rise in glutathione S-transferase, quinone reductase and epoxide hydrolase activities and expression. Incubation of precision-cut rat liver slices with intact glucosinolates (glucoerucin and glucoraphanin) enhanced the O-dealkylations of methoxy- and ethoxyresorufin and elevated CYPl apoprotein levels; similar effects were observed in lung slices. Both glucosinolates increased hepatic epoxide hydrolase, glutathione S-transferase and quinone reductase activities. Studies on the temporal induction of carcinogen-metabolising enzyme systems by glucosinolates and isothiocyanates in precision-cut rat liver slices indicated that a six- hour tissue exposure was required for induction of all enzymes to be manifested. The potential of the naturally-occurring R-sulforaphane to up-regulate carcinogen- metabolising enzyme in precision-cut rat liver slices and FAO cells was compared to that of S-sulforaphane; R -sulforaphane was superior in modulating these enzyme systems in both systems. Using the CALUX assay it was established that phenethyl isothiocyanate, erucin and sulforaphane were poor ligands to the Ah receptor. However, they effectively antagonised, III a non-competitive manner, the activation of the receptor by benzo[a]pyrene. Further studies revealed that sulforaphane could prevent and reverse the activation of the Ah receptor by benzo[a]pyrene.

No description available.

No description available.

Starch digestion begins in the mouth where it is hydrolysed into smaller polysaccharides by the enzyme salivary amylase. Three salivary amylase genes (AMY1A, B & C) and a pseudogene (AMYP1) have been described and are located in tandem on chromosome 1. Polymorphic variation has been demonstrated in Caucasians in the form of the number of repeats of the AMY1 genes, as follows: (lA-lB-Pl)n-lC. This variation has been reported to result in differing levels salivary amylase enzyme production and, as a result, differences in the efficiency of starch digestion in the mouth. It is proposed in this thesis that an increase in salivary gene copy number may be an adaptation to high starch diets as a result of the adoption of agriculture. Reliable high-throughput multiplex PCR based methods have been designed to quantify AMY1 gene copy number and to also to type 6 microsatellite markers closely linked to the AMY gene cluster. Data have been collected for 14 human populations, with different histories of cereal agriculture and ancestral levels of starch in the diet. Data have also been collected on AMY1 gene copy number in 5 chimpanzees (Pan troglodytes). The AMY1 allele frequency difference (measured using FST) between the two most extreme populations, the Mongolians and Saami, was not an outlier on a distribution of FST based on presumed neutral 11,024 SNPs from the human genome. The chimpanzee data suggest that the most frequent allele (AMY1*H1) in humans may not be the ancestral allele, as all chimpanzee chromosomes tested carried the AMY1*H0 allele (containing only one copy of the AMY1 gene). A more sensitive selection test, the analysis of the intra-allelic variability of the AMY1 repeat alleles using closely linked microsatellites, showed no compelling evidence for recent positive selection at the AMY1 locus in humans. As a result, genetic drift could not be ruled out as an explanation for the observed AMY1 allele frequency differences among populations. Alanine:glyoxylate aminotransferase (AGT) is an intermediary metabolic enzyme that is targeted to different organelles in different species. Previous studies have shown that there is a clear relationship between the organellar distribution of AGT and diet. Non-human primates show the herbivorous peroxisomal distribution of AGT. In humans a point mutation and insertion deletion polymorphism have been associated with peroxisome-to-mitochondria AGT mis-targeting. Data have been collected using a PCR/RFLP based method, in 11 human populations. In a comparison with FST values from 11.024 SNP loci, 94.5% of SNPs had a lower FST than a comparison of AGT allele frequencies for Saami and Chinese. This unusually high allele frequency difference between Chinese and Saami is consistent with the signature of recent positive selection driven by the unusually high meat content in the Saami diet.

No description available.

Nous passons plus des trois quarts de notre vie dans l'état postprandial. Pourtant, une plus grande attention a été accordée à l'étude du métabolisme à jeun qu'à l'impact de l'état postprandial sur la santé.Il est prouvé scientifiquement qu'une alimentation optimale pour la santé passe par la prise en compte de l'impact glycémique des aliments au-delà de leur simple teneur en glucides. Un déterminant important de l'impact glycémique de notre alimentation est l'amidon, qui joue un rôle clé dans la nutrition humaine en fournissant jusqu'à 50% de l'apport énergétique total. S'il est établi que la cinétique de digestion des aliments riches en amidon est un élément essentiel de leur impact glycémique, les contributions de chaque étape digestive à ce processus restent un sujet de débats. Afin de mieux comprendre les facteurs qui peuvent influencer la réponse glycémique aux aliments riches en amidon, et d’identifier de nouvelles stratégies pour atténuer leur impact glycémique, il est essentiel d'élargir notre compréhension du processus digestif de l'amidon. Cette thèse visait à étudier la digestion de repasriches en amidon (pain et pâtes), à réévaluer la contribution l’amylase salivaire à l'aide de digestions semi-dynamiques in vitro, et à mener une étude chez l'Homme pour déterminer l'effet de boissons (jus de citron et thé) sur : la réponse glycémique au pain, l'apport ad libitum, et la digestion gastrique étudiée par imagerie par résonance magnétique (IRM). Nos résultats apportent une base scientifique à l'élaboration d'une stratégie simple et efficace pour réduire la réponse glycémique aux aliments riches en amidon dans des repas de tous les jours. / All of us spend over three quarters of our lives in the postprandial state. Still, more attention has been dedicated to the study of the fasting metabolism than to the impact of the postprandial state on health.Scientific evidence supports that an optimum diet for health requires consideration of the glycaemic impact of foods in preference to consideration of carbohydrate content alone. An important determinant of the glycaemic impactof our diets is starch, which plays a key role in human nutrition, supplying up to 50% of the total energy intake. If it is clear that the digestion rate of starch-rich foods is an important determinant of their glycaemic impact, the contribution of each digestive stage to this process remains controversy. To better understand the factors that can influence the glycaemic response to starch-rich foods, and to identify new strategies to attenuate the glycaemic impact of starch-rich diets, it is essential to expand our understanding of thedigestive process of starch. The aims of this PhD were to study the digestionof starch-rich meals (bread and pasta), to reevaluate the contribution of salivary amylase using semi-dynamic in vitro digestions, and to conduct a human study to determine the effect of drinks (lemon juice and tea) on: the glycaemic response to bread, ad libitum intake, and gastric digestion assessed by magnetic resonance imaging (MRI). Our results provide scientific rationale for the development of a simple and effective strategy to reduce the glycaemicresponse to starch-rich foods in everyday-life meals.