<p> </p><p>In a time when the amount of biological data present in the public domain is becoming increasingly vast, the need for good classification systems has never been greater. In the field of glycoscience the necessity of a good classification for the enzymes involved in the biosynthesis, modification and degradation of polysaccharides is even more pronounced than in other fields. This is due to the complexity of the substrates, the polysaccharides, as the theoretical number of possible hexa-oligosaccharides from only hexoses exceeds 10¹² isomers! </p><p>An initiative to classify enzymes acting on carbohydrates began around 1990 by the French scientist Bernard Henrissat. The resulting database, the Carbohydrate Active enzymes database (CAZy), classifies enzymes by sequence similarity into families allowing the inference of structure and catalytic mechanism. What CAZy <em>does not </em>provide however, are means to understand how members of a family are related, and in what way they differ from each other. The top-down approach used in this thesis, combining phylogenetic analysis of whole CAZy families, or sub-families, with structural determinations and detailed kinetic analysis allows for exactly that.  </p><p>Finding determinants for transglycosylation <em>versus </em>hydrolysis within the <em>xth </em>gene product family of GH16 as well as restricting the hydrolytic enzymes to a well defined clade are integral parts of paper I. In paper II a new bacterial sub-clade within CE8 was discovered. The structural determination of the<em>Escherichia coli </em>outer membrane lipoprotein YbhC from from the new sub-clade explained the difference in specificity. The information provided in the two papers of this thesis gives a better understanding of the development of different specificities of diverse CAZY families as well as it aids in future gene product annotations. Furthermore this work has begun to fill the white spots uncovered in the phylogenetic trees.</p><p> </p><p> </p>

The degradation of carbohydrates is essential to many biological processes such as cell wall remodelling, host-pathogen defense, and energy synthesis in the form of ATP. Several of these processes utilize carbohydrate-active enzymes to accomplish these goals. Studying the degradation of polysaccharides by carbohydrate-active enzymes synthesized by microbes has allowed us to further understand biomass conversion. A portion of these polysaccharides consists of β-1,3-linked glucose (i.e. β-1,3-glucan), which is found in plants, fungi, and brown macroalgae. The hydrolysis of β-1,3-glycosidic linkages is catalyzed by β-1,3-glucanases, which are present in six different glycoside hydrolase (GH) families: 16, 17, 55, 64, 81, and 128. These enzymes play important biological roles including carbon utilization, cell wall modeling, and pathogen defense. This study focuses on a gene from Bacillus halodurans encoding for a multi-modular protein (BhLam81) consisting of a glycoside hydrolase from family 81 (BhGH81), a carbohydrate-binding module (CBM) from family 6 (BhCBM6), and a CBM from family 56 (BhCBM56). Previously, thorough structural and substrate-specific characterization has been carried out on BhCBM6. This CBM binds the non-reducing end of β-1,3-glucan. A member of CBM family 56 has been shown to recognize and bind the insoluble β-1,3-glucan, pachyman, however it is structurally uncharacterized. A glycoside hydrolase belonging to family 81 from Saccharomyces cerevisiae has been previously shown to degrade the β-1,3-glucans, laminarin and pachyman, however the structure of this enzyme was not determined. Recently, a member of GH family 81 has been structurally characterized; however, substrate-specificity was not determined in that study. Therefore, this study concentrated on two goals: Determining the substrate-specificity of BhGH81 and BhCBM56, and solving the structure of BhGH81 and BhCBM56 in order to gain insight into the molecular details of how they recognize and act on their substrate(s). The deoxyribonucleic acid (DNA) encoding for these modules were dissected by restriction digest from B. halodurans genomic DNA and recombinantly expressed in Escherichia coli (E. coli) as separate constructs. Both BhGH81 and BhCBM56 were purified and their crystal structures obtained. BhGH81 and BhCBM56 were solved to 2.5 Å resolution by single-wavelength anomalous dispersion (SAD) and to 1.7 Å resolution by multi-wavelength anomalous dispersion (MAD), respectively. In order to determine the substrate-specificity of BhGH81 and BhCBM56 and speculate on the molecular details of how they recognize and act on their substrate(s), substrate-specificity tests were combined with structural analysis for both of these modules. By using qualitative depletion assays, quantitative depletion assays, and affinity electrophoresis, it was revealed that BhCBM56 binds both insoluble and soluble β-1,3-glucan. The crystal structure of BhCBM56 revealed that it is a β-sandwich composed of two antiparallel β-sheets consisting of five β-strands each. By comparing BhCBM56 to a β-1,3-glucan binding protein from Plodia interpunctella (βGRP) a putative substrate-binding cleft on the concave side of the β-sandwich created by a platform of hydrophobic residues surrounded by several polar and charged residues was revealed. This comparison also allowed for speculation of the amino acids (W1015, H965, and D963) that are potentially essential for recognition of β-1,3-glucan substrates by BhCBM56. Activity of BhGH81 on β-1,3-glucans was confirmed by both thin-layer chromatography and product analysis using high performance anion exchange chromatography. The high performance anion exchange chromatography of BhGH81 hydrolysis suggested it has both exo and endo modes of action. The crystal structure of BhGH81 revealed that it consists of domains A, B, and C: A β-sandwich domain (A), a linker domain (B), and an (α/α)6-barrel domain (C). This structure revealed a putative substrate-binding cleft on one side of the (α/α)6-barrel with a blind canyon active site topology. It also revealed two putative catalytic residues, E542 and E546. All GHs from family 81 characterized so far, hydrolyze β-1,3-glucan in an endo acting manner. By comparing the structure of BhGH81 acquired in this study to a cellulase from Thermobifida fusca, which has an endo-processive mode of action, we can speculate that BhGH81 also has an endo-processive mode of action. The structural and biochemical analysis of BhGH81 and BhCBM56 in this study has aided in further understanding the molecular details both GH family 81 and CBM family 56 proteins, as well as the degradation of β-1,3-glucan by multimodular enzymes. Understanding these molecular details could be important for industrial applications such as, engineering a microbial platform for more efficient biofuel production. / Graduate

Ingesting carbohydrate (CHO) before and during prolonged steady-state exercise can significantly improve the endurance capacity (time to exhaustion) of adolescents. This knowledge, combined with current understanding of the physiological and metabolic responses of young people to prolonged steadystate exercise, as well as awareness of youth team games participation statistics, suggests CHO ingestion before and during team games exercise may be beneficial for adolescent team games players. However, research in this area has not been conducted, presenting a notable gap in the paediatric exercise science literature. This thesis described three studies with the aim of investigating the influence of CHO ingestion immediately before, and during, prolonged intermittent, high-intensity exercise on the endurance capacity, sprint performance, and physiological responses of adolescent team games players. The studies investigated a CHO-electrolyte (CHO-E) solution, solutions of differing CHO concentration ([CHO]), and CHO in the form of a gel in trained 12-14 year old soccer, rugby, and field hockey players during a modified Loughborough Intermittent Shuttle Test (LIST). Study 1 (n = 15) reported a significant 24.4% enhancement of intermittent endurance capacity with ingestion of a 6% CHO-E solution compared with a placebo (PLA, 5.1 ± 1.8 vs. 4.1 ± 1.6 min, P < 0.05, r = 0.51), with distance covered also significantly greater in the CHO trial (851 ± 365 vs. 694 ± 278 m, P < 0.05, r = 0.52). No significant influence of CHO was found for mean sprint times (P = 0.35, r = 0.27) or physiological response except at exhaustion, where peak heart rate was significantly greater in the CHO trial (P < 0.05, r = 0.55). Study two (n = 7) found a significant influence of [CHO] on intermittent endurance capacity, with a 6% solution increasing intermittent endurance capacity by 34.1% compared with a 10% solution (5.5 ± 0.8 vs. 4.1 ± 1.5 min, P < 0.05, r = 0.76). No significant difference was observed between the 2% (4.8 ± 1.2 min) and the 6% (P = 0.10, r = 0.63), or the 2% and the 10% (P = 0.09, r = 0.63) solution. Distance covered was significantly greater with the 6% solution compared with the 10% solution (931 ± 172 vs. 706 ± 272 m, P < 0.05, r = 0.76), but was not significantly different compared with the 2% solution (811 ± 230 m, P = 0.09, r = 0.63) or between the 2% and 10% solutions (P = 0.11, r = 0.61). Carbohydrate concentration did not significantly influence mean sprint times (P = 0.38, r = 0.42) or physiological response. Study three (n = 11) reported a significant 21.1% enhancement in intermittent endurance capacity with ingestion of a CHO gel, isoenergetic to the 6% CHO-E solution used in studies 1 and 2, compared with a PLA gel (4.6 ± 2.0 vs. 3.8 ± 2.4 min, P < 0.05, r = 0.67). Distance covered was also significantly greater in the CHO trial (787 ± 319 vs. 669 ± 424 m, P < 0.05, r = 0.57). No influence of the CHO gel was observed on mean sprint times (P = 0.33, r = 0.31) or physiological response. This thesis reports a significant positive influence of CHO ingestion on the intermittent endurance capacity of adolescent team games players during prolonged intermittent, high-intensity exercise. Ingestion of a 6% CHO-E solution was more beneficial than a PLA solution and a 10% CHO-E solution. When compared to a PLA gel, CHO gel ingestion was analogous in efficacy to a 6% CHO-E solution. Carbohydrate ingestion did not significantly influence sprint performance. The influence of CHO on the physiological responses of adolescent team games players to prolonged intermittent, high-intensity exercise was minimal, with the only reported effect being a significantly greater HR at exhaustion in study 1. This thesis has provided evidence to support the use of CHO before and during team games in adolescent team games players, begun to formulate guidelines for CHO ingestion by adolescent team games players, and provided a robust foundation for further study in this field.

Background/Objective: Several studies have shown that a low carbohydrate diet (LCHOD) can improve glycaemic control in type 2 diabetes (T2DM). The objective of the current study was to compare two ways of administration of a LCHOD: self-prepared meals versus ready-made meals, and their effects on weight loss, glycaemic control, body composition, cardiovascular risk and resting metabolic rate over 12 months. Research design and methods: Forty-one volunteers with the mean body mass index of 38.8 kg/m2 and poorly controlled T2DM (glycosylated haemoglobin, HbA1c > 7.5%) were randomized to either protein sparing modified fast (< 40g of carbohydrate daily, self-cooked; PSMF) or Go Lower (readymade meals; GL) diet. Both groups received multivitamin supplementation and attended monthly visits. The main outcome was weight loss and its composition. Results: Fourteen (34 %) participants completed 12 months of the intervention. There were no differences in the weight or any other changes between the diet groups at 12 months. Overall, body mass and fat mass decreased (-5.5 ± 7.3 kg, P < 0.001 and -5.1 ± 6.7 kg, P < 0.001 respectively) but fat free mass did not change. There was an overall reduction in HbA1c (-0.4 ± 1.1 %, P < 0.001), increase in HDL-cholesterol (+0.07 ± 0.18 mmol/L, P < 0.001) and decrease in triacylglycerol (-0.6 ± 2.4 mmol/L, P = 0.014). Resting metabolic rate significantly decreased (-137 ± 265 kcal/d, P < 0.001). Conclusion: LCHOD, independently of the approach taken, led to weight loss and improvements in glycaemic control in obese volunteers with poorly controlled T2DM. The results confirm that lifestyle modification using LCHOD is effective for improving T2DM and suggest that the type of approach to the diet can be matched to an individual’s preferences.

Glucose is the primary fuel for the brain and also important for exercising muscle. The purpose of the thesis was to investigate the effects of the glycaemic index (GI) of mixed meals on appetite, cognitive performances and metabolic responses during intermittent exercise in recreationally active adults. Study one investigated whether a low GI (LGI) breakfast (GI = 42.5) could suppress appetite and reduce energy intake (EI) of 12 recreationally active females (28.2 ± 8.0 years) more than a high GI (HGI) breakfast (GI = 73.5). Area under the curve of the appetite score (AS AUC) following LGI breakfast was significantly greater than the HGI trial during the 60-min postprandial (pp) period (2568 ± 1027 vs. 2198 ± 821 mm∙min, p = 0.025). The HGI breakfast facilitated a stronger appetite suppressing effect up to eight hours post breakfast than the LGI trial (18834 ± 3906 vs. 21278 ± 3610 mm∙min, p = 0.028). The EI on the LGI trial day was significantly higher than on the pre-trial day (2,215 ± 576 vs. 1,748 ± 464 kcal, corrected p = 0.008). Fourteen recreationally active males (34.5 ± 8.9 years) in study two consumed the LGI (GI = 41.3) and HGI (GI = 74.3) breakfasts in the laboratory and then prescribed LGI and HGI meals in the free living environment. In line with study one, the AS AUC was significantly smaller following HGI than LGI breakfast over the 60-min pp period (2,989 ± 1,390 vs. 3,758 ± 1,290 mm∙min, p = 0.027). The HGI meals (GI = 76.9) suppressed appetite more than the LGI meals (GI = 39.6) over 12 hours on the trial day (35,454 ± 9,730 vs. 41,244 ± 8,829 mm∙min, p = 0.009) although energy balance was not different between trials. Study three investigated whether following a LGI breakfast (GI = 42.2) providing 1 g CHO kg-1 BM could result in a better vigilance and attention than a HGI breakfast (GI = 72.4), and reduced lunch EI in 16 recreationally active males (24.4 ± 3.6 years). A significant trial x time effect in the interference time of the Stroop Colour Word Task (SCWT) (p = 0.039) showed that the LGI breakfast maintained the attentional performance up to 90-min pp. Both high pre-task glucose concentration ([Glucose]) at 15-min pp and low pre-task [Glucose] at 105-min pp in the HGI trial were associated with unfavourable outcomes in vigilance in the Rapid Information Processing Task (RIPT). The LGI pre-task [Glucose] returning back to fasting level at 60-min pp was associated positively with the response time. The pre-lunch AS was a significant predictor of the lunch EI per fat free mass which explained 21% and 26% of variance in the LGI and HGI trials respectively. No significant difference was found in the ad libitum lunch EI between trials. Sixteen recreationally active males (27.8 ± 7.7 years) in study four consumed a LGI (GI = 42) and a HGI breakfast (GI = 72.8) providing 1.2 g CHO kg-1 BM consumed 60 minutes prior to intermittent running on two separate mornings. Better attentional performance at 150-min pp was found following LGI than HGI breakfast. The significant trial x time interaction in the SCWT (p = 0.045) showed the shortest interference time performed after the last exercise session in the LGI trial. The amounts of CHO and fat being oxidized were comparable between trials during three sessions of 16-min intermittent running with an average intensity of 65% V̇O2max. In conclusion, the pre-meal appetite sensation is more predictive of the subsequent meal EI than the pre-meal [Glucose]. The meal strategy for weight management in recreationally active adults may focus on greater appetite suppression by selecting HGI foods whilst maintaining healthy eating guidelines. Recreationally active males performing sports requiring high levels of vigilance and selective attention with low physical activity levels can benefit up to 60–90 min pp from the LGI breakfast. Their attentional performance can benefit from the LGI breakfast with moderate to high intermittent intensities in the late exercise period at 150–min pp. Recreationally active adults should consider the timing of meal consumption in relation to performing intermittent exercise, in order to maximize the advantages from the LGI or HGI breakfasts for cognitive performance or appetite suppression. They may be more liberal in pre-exercise food choices if substrate oxidation during intermittent running is only of their concern.

An estimated 86 million Americans in the United States age 20 and older are classified as prediabetic. Prediabetes is defined as an individual having a higher blood sugar than normal increasing the risk for developing type 2 diabetes (T2DM). T2DM is among the top ten leading causes of death in the United States and costs an estimated 245 billion dollars annually. Interventions need to take place among patients with prediabetes in order to prevent the T2DM epidemic from compounding. This study examined the effects of a six-week low carbohydrate diet on A1C values, weight and BMI, and cardiovascular markers among patients with prediabetes. A retrospective chart review examined 1,169 patients with prediabetes that met inclusion criteria from July 2013 to April 2016. Patients had completed a six-week low carbohydrate diet program with weekly clinic visits with a nurse practitioner and followed the prescribed low carbohydrate diet. A significant difference in means was found when comparing pre A1C values (M= 5.93, SD= 0.20) and post A1C values (M= 5.57, SD= 0.25); (t (1142) = 49.3, p = 0.00), pre intervention weight (M= 227.0, SD= 52.0) and post intervention weight (M = 209.5, SD = 48.0); (t (1168) = 79.3, p = 0.00), and pre BMI (M = 36.8, SD = 7.0) and post BMI (M = 34.0, SD = 6.6); (t (1168) = 77.8, p = 0.00). Additionally, statistical significance was found for cardiovascular markers including systolic and diastolic blood pressures, total cholesterol, LDL, HDL and triglycerides. These findings suggest that a low carbohydrate diet is effective at improving metabolic risk factors for prediabetes and preventing the progression to T2DM. Low carbohydrate diets should be further examined for long term effectiveness and could be recommended to patients with prediabetes in order to reverse the epidemic of T2DM.

Les glycanes présents à la surface des cellules cancéreuses sont souvent modifiés par rapport à ceux d’une cellule saine. Or ces antigènes glucidiques n’induisent pas de réponse immune efficace. La GalNAc est le premier sucre fixé lors de la O-glycosylation de type mucine et ainsi ce sucre entre dans la composition de nombreux antigènes tumoraux. Le but de notre travail était de préparer des analogues synthétiques de la GalNAc susceptibles d’être incorporés à la surface de cellules cancéreuses et dans les mucines synthétisées par les tumeurs, afin d’augmenter la réponse immune vis-à-vis des glycanes tumoraux. Nous avons synthétisé chimiquement des analogues de la GalNAc afin de les tester in vitro en tant que substrats de la voie de « sauvetage » de la GalNAc chez les mammifères et donc d’enzymes impliquées dans cette voie : une kinase (GK2) et une UDP-pyrophosphorylase (AGX1) humaines. Les meilleurs candidats ont permis la synthèse de différents UDP-sucres et une GalNAc-transférase (ppGalNAc T1) bovine a pu être utilisée in vitro pour transférer certains de ces analogues, à partir de leur forme activée en UDP-sucre, sur des peptides. Nous avons donc pu montrer que certains des analogues synthétisés étaient capables de s’intégrer dans la voie de sauvetage et d’être incorporés dans des peptides. Le pouvoir immunologique des glycoconjugués de type mucine ainsi formés a été étudié chez la souris après couplage de ces glycoprotéines à une protéine immunostimulante (KLH). D’autre part, des cellules de mammifères ont également été cultivées en présence de ces analogues afin de vérifier leur incorporation au niveau des glycoconjugués de la surface des cellules. / Glycans are often present at the cancerous cell surface in a modified form compared to healthy cells. However, these carbohydrate antigens don’t lead to an effective immune response. GalNAc is the first sugar attached to mucin type O-glycans and is thus a component of numerous tumor antigens. The aim of our work was to prepare synthetic GalNAc analogs able to be incorporated at the surface of cancer cell and into mucins synthesized by tumors in order to increase the immune response toward tumor glycans. We chemically synthesized GalNAc analogs to test them in vitro as substrates of enzymes involved in the mammalian GalNAc salvage pathway: a human galactokinase (GK2) and a human UDP-pyrophosphorylase (AGX1). The best candidates allowed the synthesis of the corresponding UDP-sugars further used to test the transfer of those analogs onto peptides using a bovine GalNAc transferase (ppGalNAc T1). We have shown that some synthetic analogs could be integrated in the GalNAc salvage pathway and O-linked to peptides. Immunological properties of the glycoconjugates thus formed were studied in mice after coupling to an immunostimulant protein (KLH). Moreover, mammalian cells were cultivated in the presence of these analogs in order to check their incorporation into glycoconjugates at the cell surface.

Low molecular weight gelators (LMWGs) are interesting materials whose applications are as diverse and wide ranging as their molecular structures. These materials self-assemble through the formation of non-covelent intermolecular forces and interactions to form supramolecular assemblies that trap solvent within their matrices. Because of the non-covalent nature of the forces of self-assembly, the gelation process is typically thermally reversible. In addition, low molecular weight gelators can also be modified to respond to various stimuli, such as change in pH, presence of enzymes or metal cations, or exposure to light. The design of low molecular weight gelators is often difficult, and most new classes of low molecular weight gelators are discovered by serendipity. As such, it is often useful to use structural templates in the design of LMWGs. Biomolecules, such as steroids, amino acids and peptides, and carbohydrates make excellent templates due to their inherent propensity to self assemble. A review of the current literature regarding the use of biomolecules as templates for the design and synthesis of LMWGs will be presented in chapter 1. Our research group has been active in the research of carbohydrate-based LMWGs for several years, and these results are also briefly reviewed in the related chapters. The synthesis and characterization of ester derivatives of D-galactose, D-glucose, and amide derivatives of D-glucosamine will be discussed in chapters 2-4, along with their evaluation for gelation in aqueous and organic solvents, such as hexane, ethanol, water, and aqueous DMSO or ethanol mixtures.

Foram sintetizadas duas novas séries de tensoativos de açúcar derivados da 2-D-glucosamina: os metil 2-acilamido-2-deóxi-6-O-sulfonato-D-glucopiranosídeos de sódio (aniônicos) e os cloretos de metil 2-acilamido-2,6-dideóxi-6-trimetilamônio-D-glucopiranosídeos (catiônicos). Os tensoativos aniônicos foram obtidos pela acilação da 2-D-glucosamina com cloretos de acila (com 8, 12 e 16 carbonos), seguida pela metilação desses derivados com metanol em meio ácido, e posterior sulfatação dos metil glucosídeos com complexo trióxido de enxofre-piridina. Os tensoativos catiônicos foram obtidos pela tosilação dos metil glucosídeos, seguida pela quaternização com trimetilamina e troca do contra-íon tosilato por cloreto com resina de troca-iônica. Esses tensoativos apresentaram c.m.c. similares a de outros tensoativos iônicos de cadeia hidrofóbica de igual comprimento, mas energias livres de transferência do grupo polar para a micela muito mais favoráveis. Esse fato foi atribuído à formação de ligações de hidrogênio entre os grupos polares do tensoativo na micela, e à hidrofobicidade do açúcar. As micelas formadas apresentaram números de agregação maiores que os obtidos para outros tensoativos, provavelmente devido às interações atrativas entre os grupos polares. / Two new sugar-based surfactant series were synthesized from 2-D-glucosamine: sodium methyl 2-acylamido-2-deoxi-6-O-sulfonate-D-glucopyranosides (anionic) and methyl 2-acylamido-2,6-dideoxi-6-trimethylamonium-D-glucopyranoside chlorides (cationic). The anionic surfactants were obtained by the acylation of 2-D-glucosamine with acyl chlorides (with 8, 12 and 16 carbons), followed by the methylation of these derivatives with methanol in acidic media, and the sulfation of the methyl glucosides with sulfur trioxide-pyridine complex. The cationic surfactants were obtained by the tosylation of methyl glucosides followed by the quaternization with trimethylamine and exchange of the tosylate contra-ion with chloride ions on an ion exchange resin. These surfactants showed c.m.c. similar to other ionic surfactants with equal hydrophobic chain lengths, but more favorable free energies of transfer of the polar head to the micelle. This fact is attributed to hydrogen bonding between the head groups of the surfactant in the micelle, and the hydrophobicity of the sugar moiety. The micelles of these surfactants showed aggregation numbers larger than those obtained for other surfactants, problably because of head-group attractive interactions.

Mammals and fish rely on hormones to regulate blood glucose levels. The two major glucose regulating hormones are insulin and glucagon. Literature on mammalian insulin and glucagon is quite extensive, however, there is limited information on how these hormones regulate blood glucose levels in fish. The material available for fish mostly pertains to changes in glucose concentration and gene expression of enzymes, but there is no information on the direct influence they have on glucose kinetics. Therefore, the main goal of my thesis is to measure the change in hepatic glucose production and glucose disposal when rainbow trout are administered insulin or glucagon. The beginning of my research focused on insulin. I hypothesized that rainbow trout respond to insulin by decreasing hepatic glucose production and increase glucose disposal, just like mammals. To test this, I infused insulin for 4 hours at 1.5 g insulin kg 1 min-1. I measured glucose disposal (Rd glucose), hepatic glucose production (Ra glucose), and blood glucose concentration. Following insulin administration the glucose fluxes decreased steadily (Rd glucose -37% and Ra glucose -43%). The decline in blood glucose levels follows the difference between Rd and Ra. These results explain why rainbow trout are unable to clear a glucose load to the same degree as mammals. The second major glucose hormone (glucagon) is what interested me for the second part of the research. The limited information on fish glucagon is even less than that of fish insulin. I speculated that trout respond to glucagon the same way mammals do (increase hepatic glucose production and show no affect on glucose disposal). To study the effects of glucagon on glucose fluxes, I tracked the changes in Ra and Rd glucose. The results showed glucose fluxes showed no siginificant difference from baseline in the first few hours, then steadily decreasing until the final time point reached values below baseline. Therefore, these experiments revealed that glucagon follows a similar pattern of effects in trout as mammals. However, the strength of the response to glucagon is different between trout and mammals. This thesis is the first to investigate the effects of insulin and glucagon on glucose kinetics in rainbow trout. I have concluded that rainbow trout have different responses to insulin and glucagon when compared to mammals. Furthermore, fish showing limited glucoregulatory capacity can be partially explained by their responses to insulin and glucagon.