NUTRITIONAL AND CONTRACTILE REGULATION OF HUMAN MUSCLE PROTEIN SYNTHESIS: ROLE OF LEUCINE AND CITRULLINE

Amino acids are key nutritional stimuli that are both substrate for muscle protein synthesis (MPS), and signaling molecules that regulate the translational machinery. There is a dose-dependent relationship between protein intake and MPS that differs between young and elderly subjects. The current thesis contains results from three separate studies that were conducted to examine to potential to enhance smaller doses of protein, known to be suboptimal in their capacity to stimulate MPS, through supplementation with specific amino acids, namely leucine and citrulline. The first two studies examined the potential to enhance the muscle protein synthetic capacity of a smaller, suboptimal dose of whey protein with leucine. In study one, we concluded that leucine supplementation of a suboptimal dose of protein could render it as effective at enhancing rates of MPS as ~four times as much protein (25 g) under resting conditions, but not following resistance exercise. In study two, we examined the potential of leucine and branched-chain amino acids to enhance the MPS response of a suboptimal dose of protein within the context of mixed macronutrient ingestion. We concluded that supplementation with a relatively high dose of leucine could render it as effective at enhancing MPS rates as ~four times as much protein (25 g) under both resting and post-exercise conditions. In study three, we examined the potential of citrulline supplementation to enhance blood flow, microvascular circulation, and MPS in response to a suboptimal dose of whey protein in elderly subjects. We concluded that supplementation of a suboptimal dose of protein with citrulline did not augment bulk blood flow or muscle microvascular circulation. The major findings from the works presented in this thesis is that smaller doses of protein that normally elicit a suboptimal increase in MPS can be made more anabolic when supplemented with specific amino acids.Doctor of Philosophy (PhD

Conservation physiology can inform threat assessment and recovery planning processes for threatened species

Conservation physiology has emerged as a discipline with many success stories. Yet, it is unclear how it is currently integrated into the activities of the IUCN and other bodies which undertake international, national, or regional species threat assessments and work with partners to develop recovery plans. Here we argue that conservation physiology has much to offer for the threat assessment process and we outline the ways in which this can be operationalized. For instance, conservation physiology is effective in revealing causal relationships and mechanisms that explain observed patterns, such as population declines. Identifying the causes of population declines is a necessary precursor to the design of actions to reverse or mitigate such threats. Conservation physiology can also identify complex interactions and support modeling activities that consider emerging threats. When a population or species is deemed threatened and recovery plans are needed, physiology can be used to predict how organisms will respond to the conservation intervention and future threats. For example, if a recovery plan was focused on translocation, understanding how to safely translocate organisms would be necessary, as would ensuring that the recipient habitat provides the necessary environmental characteristics to meet the fundamental physiological needs/tolerances of that organism. Our hope is that this paper will clarify ways in which physiological data can make an important contribution to the conservation activities of bodies like the IUCN that are engaged in threat assess

The potential of fractional diagonal chromatography strategies for the enrichment of post-translational modifications

More than 450 post-translational modifications (PTMs) are known, however, currently only some of those can be enriched and analyzed from complex samples such as cell lysates. Therefore, we need additional methods and concepts to improve our understanding about the dynamic crosstalk of PTMs and the highly context-dependent regulation of protein function by so-called ‘PTM codes’. The mere focus on affinity-based enrichment techniques may not be sufficient to achieve this ambitious goal. However, the complementary use of two-dimensional chromatography-based strategies such as COFRADIC and ChaFRADIC might open new avenues for enriching a variety of so far inaccessible PTMs for large-scale proteome studies

Irregular meal pattern-effects on energy expenditure, metabolism and appetite regulation: a randomized controlled trial in healthy normal-weight women

Background: Obesity is increasing in parallel with greater all-day food availability. The latter may promote meal irregularity, dysregulation of the energy balance, and poor metabolic health. Objective: We investigated the effect of meal irregularity on the thermic effect of food (TEF), lipid concentrations, carbohydrate metabolism, subjective appetite, and gut hormones in healthy women. Design: Eleven normal-weight women (18–40 y of age) were recruited in a randomized crossover trial with two 14-d isoenergetic diet periods (identical foods provided and free living) that were separated by a 14-d habitual diet washout period. In period 1, participants followed a regular meal pattern (6 meals/d) or an irregular meal pattern (3–9 meals/d), and in period 2, the alternative meal pattern was followed. Before and after each period, when participants were fasting and for 3 h after intake of a test drink, measurements were taken of energy expenditure, circulating glucose, lipids (fasting only), insulin, glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin. An ad libitum test meal was offered. Subjective appetite ratings were assessed while fasting, after the test drink, after the ad libitum meal, and during the intervention. Continuous interstitial glucose monitoring was undertaken for 3 consecutive days during each intervention, and the ambulatory activity pattern was recorded (ambulatory energy expenditure estimation). Results: Regularity was associated with a greater TEF (P , 0.05) and a lower incremental area under the curve (iAUC) for glucose after intake of the test drink (over 3 h) and, for some identical meals, during the 2 interventions (over 90 min) (day 7: after breakfast; day 9: after lunch and dinner). There was no difference between treatments for the test-drink gut hormone response. A time effect was noted for fasting GLP-1, fasting PYY, PYY responses, and hunger-rating responses to the test drink (P ˂ 0.05). Lower hunger and higher fullness ratings were seen premeal and postmeal during the regular period while subjects were free living. Conclusion: Meal regularity appears to be associated with greater TEF and lower glucose responses, which may favor weight management and metabolic health. This trial was registered at clinical trials.gov as NCT02052076

The Impact of Compressed Workweek on Absenteeism: The Case of Ontario Prison Guards on a Twelve-hour Shift

Depuis quelques décennies, on remet en question la semaine normale de travail par une série d'innovations dans les horaires de travail, notamment la semaine de travail comprimée (STC). L'horaire d'une STC reflète une relation d'arbitrage entre des jours de travail plus longs et moins de jours travaillés par semaine. La version la moins populaire de la STC (impliquant un peu plus de 3 % de la main-d’œuvre canadienne) est celle du quart de travail de 12 heures qu'on retrouve d'habitude pour des opérations continues.Nous inventorions d'abord les recherches pertinentes qui ont été publiées. Les premières recherches sur la STC, au début des années 70 étaient truffées d'un certain nombre de problèmes que les recherches ultérieures ont tenté de résoudre (v.g. petite taille des échantillons, manque de preuves empiriques, manque de données longitudinales et absence de groupe contrôle).Une recherche typique de ces années impliquait des perceptions ex post facto sans groupe contrôle. Ici, nous utilisons une méthodologie qui vise à mesurer l'impact d'un horaire de STC de 12 heures sur l'absentéisme au moyen d'un ensemble de données longitudinales et d'un groupe de comparaison dans un contexte d'avant et d'après. Contrairement aux recherches précédentes, nous utilisons une mesure empirique de performance avec un plan de recherche solide. Cette étude s'attarde sur les expériences d'un centre de détention provincial qui a mis sur pied une STC pour ses gardiens syndiqués durant la fin des années 80. Le syndicat local recherchait activement un horaire de STC permettant la prise de plus de fins de semaines complètes par année. Un comité patronal-syndical fut instauré pour examiner la journée de travail de 12 heures. Vu qu'un centre de détention est caractérisé par une haute intensité de main-d’œuvre, on a porté une attention particulière à l'absentéisme surtout avant et après l'implantation du nouvel horaire de travail.Pour ces gardiens, on a colligé des données sur l'absentéisme un an avant et deux ans après l'instauration de la STC. Les autres gardiens, exclus de cette expérience, ont servi de groupe de comparaison. Nous avons ensuite exploré différents modèles. Le développement de cadres de références permettant des prédictions en ce domaine est encore à l'étape de balbutiement. Le plus développé de ces cadres préliminaires prédit l'absence de forts effets sur l'absentéisme. Ici nous utilisons des modèles d'analyse transversale, diachronique et de comparaison de groupes pour examiner l'impact de la STC sur l'absentéisme des gardiens. Les études avec des données pour une seule période de STC (ex post seulement) utiliserait un modèle d'analyse transversale. Dans le modèle diachronique, la valeur de l'absentéisme dans la période pré-STC est utilisée pour évaluer ce que l'absentéisme des gardiens dans la période STC aurait été si un tel horaire n'avait pas été instauré. Le modèle de comparaison des groupes rend variable dépendante le changement dans l'absentéisme entre les périodes pré-STC et STC. Avec le modèle d'analyse transversale, la variable STC a un grand impact positif sur l'absentéisme. Pour le modèle diachronique, ce même impact est la moitié du précédent. Et pour le modèle de comparaison des groupes, la variable STC a relativement peu d'impact. Considérant que l'absentéisme de base des gardiens est d'environ 9 jours, l'impact de STC sur cet absentéisme est approximativement de 5 jours, 2,5 jours et 1 jour pour chacun des trois modèles.Donc, ces trois modèles produisent des résultats substantiellement différents. La variable STC perd de sa puissance à mesure que le modèle est mieux spécifié. Ces modèles démontrent l'importance d'utiliser une recherche méthodologique solide. En termes pratiques, nos résultats sont similaires à ceux des recherches précédentes et les prédictions faites à partir du cadre utilisé sont vérifiées. C'est donc dire qu'en utilisant différents modèles pour l'étude d'une même question, on en arrive à des conclusions différentes.The study consists of absenteeism measures for a group of prison guards who switched from an 8-hour work day to a 12- hour day compressed workweek (CWW) schedule with absenteeism measures for one year prior to the onset of the schedule and two years on the new schedule. Absenteeism data were compared between the CWW group and a comparison group of regular schedule guards and between the pre-CWW and CWW periods. Absenteeism leuels were higher for the CWW group compared to the comparison group, and were higher over the CWW period when compared to the pre-CWWperiod. In the best specified models, those guards on the CWW had higher absenteeism than the comparison group, though the latter difference was not statistically significant.El estudio consiste en la medida del ausentismo de un grupo de guardias de prisiòn que cambiaron de un horario de 8 horas por dìa a un horario comprimido de 12 horas por dìa. El estudio se extiende a partir de un ano antes del cambio de horario e incluye los dos anos subsecuentes al cambio de horario. Los porcentajes de ausentismo fueron comparados entre el grupo de guardias en el horario comprimido y un grupo de guardias en un horario regular asì como entre el mismo grupo de guardias antes de y después del cambio de horario. El porcentaje de ausentismo fue mas elevado para el grupo en el horario comprimido en comparaciòn con el grupo en el horario normal, el porcentaje de ausentismo fue también mas elevado en el grupo con horario comprimido después del cambio de horario que antes de este. En el mejor de los modelos especificados los guardias en el grupo con horario comprimido tuvieron un porcentaje mas elevado de ausentismo que el grupo de guardias en el horario normal aun y cuando la diferencia no es estadìsticamente importante

The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults

Background: Popular beliefs that breakfast is the most important meal of the day are grounded in cross-sectional observations that link breakfast to health, the causal nature of which remains to be explored under real-life conditions. Objective: The aim was to conduct a randomized controlled trial examining causal links between breakfast habits and all components of energy balance in free-living humans. Design: The Bath Breakfast Project is a randomized controlled trial with repeated-measures at baseline and follow-up in a cohort in southwest England aged 21–60 y with dual-energy X-ray absorptiometry–derived fat mass indexes #11 kg/m2 in women (n = 21) and #7.5 kg/m2 in men (n = 12). Components of energy balance (resting metabolic rate, physical activity thermogenesis, energy intake) and 24-h glycemic responses were measured under free-living conditions with random allocation to daily breakfast ($700 kcal before 1100) or extended fasting (0 kcal until 1200) for 6 wk, with baseline and follow-up measures of health markers (eg, hematology/biopsies). Results: Contrary to popular belief, there was no metabolic adaptation to breakfast (eg, resting metabolic rate stable within 11 kcal/d), with limited subsequent suppression of appetite (energy intake remained 539 kcal/d greater than after fasting; 95% CI: 157, 920 kcal/d). Rather, physical activity thermogenesis was markedly higher with breakfast than with fasting (442 kcal/d; 95% CI: 34, 851 kcal/d). Body mass and adiposity did not differ between treatments at baseline or follow-up and neither did adipose tissue glucose uptake or systemic indexes of cardiovascular health. Continuously measured glycemia was more variable during the afternoon and evening with fasting than with breakfast by the final week of the intervention (CV: 3.9%; 95% CI: 0.1%, 7.8%). Conclusions: Daily breakfast is causally linked to higher physical activity thermogenesis in lean adults, with greater overall dietary energy intake but no change in resting metabolism. Cardiovascular health indexes were unaffected by either of the treatments, but breakfast maintained more stable afternoon and evening glycemia than did fasting

Identification of cleavage sites and substrate proteins for two mitochondrial intermediate peptidases in Arabidopsis thaliana

Most mitochondrial proteins contain an N-terminal targeting signal that is removed by specific proteases following import. In plant mitochondria, only mitochondrial processing peptidase (MPP) has been characterized to date. Therefore, we sought to determine the substrates and cleavage sites of the Arabidopsis thaliana homologues to the yeast Icp55 and Oct1 proteins, using the newly developed ChaFRADIC method for N-terminal protein sequencing. We identified 88 and seven putative substrates for Arabidopsis ICP55 and OCT1, respectively. It was determined that the Arabidopsis ICP55 contains an almost identical cleavage site to that of Icp55 from yeast. However, it can also remove a far greater range of amino acids. The OCT1 substrates from Arabidopsis displayed no consensus cleavage motif, and do not contain the classical –10R motif identified in other eukaryotes. Arabidopsis OCT1 can also cleave presequences independently, without the prior cleavage of MPP. It was concluded that while both OCT1 and ICP55 were probably acquired early on in the evolution of mitochondria, their substrate profiles and cleavage sites have either remained very similar or diverged completely