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Identification and Characterisation of Lipid Droplet-Localised ProteinsKrawczyk, Hannah Elisa 12 January 2022 (has links)
No description available.
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Incorporation of the Paternò–Büchi reaction into mass spectrometry-based systems for lipid structural characterizationElissia T Franklin (8087996) 10 December 2019 (has links)
<p>Lipids are important cellular
biomolecules that perform essential functional and biological roles. For
instance, lipids in the cell are the compartmentalizer for the cytoplasm and an
energy storage unit. The knowledge surrounding lipids is abundant, yet there is
still so much to uncover. There are many categories of lipids and within each
category the structural composition is extremely diverse. In turn, the dramatic
structural complexity of lipids demands analytical methods capable of providing
in-depth structural characterization of individual molecular structures. However,
lipid structural elucidation has remained challenging, namely due to the
presence of isomeric and isobaric species with a complex mixture. In
particular, isomeric/isobaric lipid structures arise from variations in class,
headgroup, fatty acyl chain, <i>sn</i>-position,
and/or carbon-carbon double bond (C=C) position(s). Recently, recent research
suggests C=C composition impacts lipid physical properties, metabolic fate, and
intermolecular interactions. Thus, analytical strategies capable of localizing
sites of unsaturation are of interest in the lipidomics community.</p>
<p>Mass spectrometry (MS) is a
leading tool for lipid analysis. Electrospray ionization (ESI), a soft
ionization method, is the most commonly used method for lipid ionization as a
means of taking the ions from liquid-phase to gas-phase without extensive decomposition
of the species. Utilizing ESI-MS, lipids can be identified at a sum
compositional level via accurate mass measurements. . With tandem mass
spectrometers, lipid ions can be further probed, utilizing tandem-MS (MS/MS) to
generate structurally informative product ion spectra that facilitate the
assignment of lipid molecular structure. More so, gas-phase ion/ion reactions
represent a unique MS-based technique that has improved the analysis of lipids
structures. Gas-phase ion/ion reactions allow for lipid species to be charge
inverted from one polarity to the opposite polarity. This reaction enables
lipids to be ionized in a polarity that is optimal for class identification and
further investigated in the opposite polarity where more structural information
is obtained. All the information provided is captured without the requirement
of multiple solution conditions which is necessary when analyzing in both
polarities. In the case of charge inverted lipids from positive ion mode to
negative ion mode, fatty acyl composition can be obtained; however, C=C
information is lacking.</p>
<p>MS can also be paired with other
analytically technologies to assist with lipid analysis. One of those
technologies is liquid chromatography (LC), which allows for the separation of
lipids based on different characteristic depending on the column type being
used. Reverse-phase LC (RPLC) allows for the separation of lipid molecular
species based on structural composition. RPLC-MS/MS benefits from the ability
to separate lipids and determine their fatty acyl chain composition but it is
difficult to specify C=C location with the use of a synthetic standard that is
identical to each molecular species being analyzed.</p>
<p>Commonality between the
gas-phase ion/ion reactions for charge inversion of lipids and RPLC-MS/MS
approaches is the inability to provide C=C coverage. In-solution and unique ion
activation techniques have been developed for seeking such information. The
Paternò–Büchi reaction is a UV-initiated [2 + 2]-cycloaddition of an excited carbonyl
containing compound onto an olefin group. This reaction can be initiated onto
the alkene group within an unsaturated lipid aliphatic chain to form an oxetane
ring modification. There are two product ions that can be formed upon each
unsaturation site due to a lack of regioselectivity the reagent can attach at
either side of the C=C. The modified lipids can be taken into gas-phase and
collisionally activated via low-energy collision induced dissociation,
generating product ions indictive of C=C position(s). The work herein shows the
incorporation of the PB reaction into the gas-phases ion/ion reaction and
RPLC-MS/MS apparatuses for C=C localization. The methods have been applied to
the lipid extracts of bovine liver and human plasma for confident molecule
species determination.</p>
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Lipogenic Proteins in Plants: Functional Homologues and ApplicationsCai, Yingqi 12 1900 (has links)
Although cytoplasmic lipid droplets (LDs) are the major reserves for energy-dense neutral lipids in plants, the cellular mechanisms for packaging neutral lipids into LDs remain poorly understood. To gain insights into the cellular processes of neutral lipid accumulation and compartmentalization, a necessary step forward would be to characterize functional roles of lipogenic proteins that participate in the compartmentalization of neutral lipids in plant cells. In this study, the lipogenic proteins, Arabidopsis thaliana SEIPIN homologues and mouse (Mus Musculus) fat storage-inducing transmembrane protein 2 (FIT2), were characterized for their functional roles in the biogenesis of cytoplasmic LDs in various plant tissues. Both Arabidopsis SEIPINs and mouse FIT2 supported the accumulation of neutral lipids and cytoplasmic LDs in plants. The three Arabidopsis SEIPIN isoforms play distinct roles in compartmentalizing neutral lipids by enhancing the numbers and sizes of LDs in various plant tissues and developmental stages. Further, the potential applications of Arabidopsis SEIPINs and mouse FIT2 in engineering neutral lipids and terpenes in plant vegetative tissues were evaluated by co-expressing these and other lipogenic proteins in Nicotiana benthamiana leaves. Arabidopsis SEIPINs and mouse FIT2 represent effective tools that may complement ongoing strategies to enhance the accumulation of desired neutral lipids and terpenes in plant vegetative tissues. Collectively, our findings in this study expand our knowledge of the broader cellular mechanisms of LD biogenesis that are partially conserved in eukaryotes and distinct in plants and suggest novel targets that can be introduced into plants to collaborate with other factors in lipid metabolism and elevate oil content in plant tissues.
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Comparative Mapping of QTLs Affecting Oil Content, Oil Composition, and other Agronomically Important Traits in Oat (Avena sativa L.)Hizbai, Biniam T. 01 November 2012 (has links)
Groat oil content and composition are important quality traits in oats (Avena sativa L). These traits are controlled by many genes with additive effects. The chromosomal regions containing these genes, known as quantitative trait loci (QTL), can be discovered through their close association with markers. This study investigated total oil content and fatty acid components in an oat breeding population derived from a cross between high oil ('Dal') and low oil ('Exeter') parents. A genetic map consisting of 475 DArT (Diversity Array Technology) markers spanning 1271.8 cM across 40 linkage groups was constructed. QTL analysis for groat oil content and composition was conducted using grain samples grown at Aberdeen, ID in 1997. QTL analysis for multiple agronomic traits was also conducted using data collected from hill plots and field plots in Ottawa, ON in 2010. QTLs for oil content, palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3) were identified. Two of the QTLs associated with oil content were also associated with all of the fatty acids examined in this study, and most oil-related QTL showed similar patterns of effect on the fatty acid profile. These results suggest the presence of pleiotropic effects on oil-related traits through influences at specific nodes of the oil synthesis pathway. In addition, 12 QTL-associated markers (likely representing nine unique regions) were associated with plant height, heading date, lodging, and protein content. The results of this study will provide information for molecular breeding as well as insight into the genetic mechanisms controlling oil biosynthesis in oat.
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Conception des triacylglycérides à propriétés contrôlées : formulation et modélisation / Desenvolvimento de ferramentas computacionais de auxílio ao projeto de produtos utilizando óleos vegetais : equilíbrio de fases sólido-líquidoTeles dos Santos, Moisés 18 November 2010 (has links)
Issues de ressources renouvelables, les huiles végétales (mélanges de triacylglycérols) sont des matières premières aux multiples applications dans divers secteurs, tels que l’industrie alimentaire, les lubrifiants, les solvants, les cosmétiques, la pharmacie, parmi autres. Pour faciliter le développement de produits utilisant de telles matières premières, le travail de thèse s’intéresse à la modélisation de l'équilibre de phases pour mélanges de triacylglycérols et la conception d’un logiciel prédictif de leurs propriétés. Les modèles employés sont totalement prédictifs et tiennent compte des polymorphes. La phase liquide et le polymorphe a sont supposés idéaux à l’inverse des polymorphes b et b’ dont les coefficients d’activités sont calculés à l’aide du modèle de Margules où les coefficients d’interactions binaires sont prédits à partir de la similarité des chaines d’acide gras sur le squelette glycérol. L'optimisation directe de l'énergie libre de Gibbs permet de calculer la quantité de solide dans les graisses ; propriété fondamentale corrélée à de nombreuses fonctionnalités de produits basés sur des huiles végétales. Le calcul de l'équilibre solide - liquide à plusieurs températures permet de simuler des courbes de fusion et des courbes de calorimétrie différentielle à balayage. L’influence sur ces courbes de modifications dans la structure moléculaire et de la composition des mélanges est étudier pour plusieurs systèmes et comparés avec des données expérimentales: triacylglycérols purs, mélanges binaires et ternaires de triacylglycérols, huiles végétales naturelles et mélanges d'huiles végétales impliquant des centaines de triacylglycérols. Des réactions d'interestérification chimique, largement utilisées pour modifier la composition et propriétés d'huiles et graisses, sont simulées et comparés avec des données expérimentales. Le bon accord avec les données expérimentales permet de valider l'outil informatique et son caractère prédictif permet d’envisager son utilisation pour des mélanges, températures et compositions encore non évaluées de façon à orienter les efforts expérimentaux vers les mélanges les plus prometteurs. / The search for sustainable development is an incentive for renewable resources usage in chemical industry. Vegetable oils (triacylglycerol-based mixtures) are raw-materials that match this criterion and they are currently and potentially used in a wide range of sectors, such as: food industry, lubricants, solvents, cosmetics, pharmaceutical, among others. Aiming to aid product design using such raw-materials, this work deals with phase equilibrium modeling and the development of a computational tool for properties prediction. The models used are totally predictive and they deal with the existence of solid polymorphism. The liquid state and the crystals are treated as ideal phases. The activity coefficients of phases ’ and (notideal) are estimated using Margules model, for which the binary molecular interaction parameters are calculated in a predictive manner by means of correlations with the similarity degree between fatty acids chains in the glycerol. By direct optimization of Gibbs Free Energy, the Solid Fat Content is computed, a fundamental property for vegetable oils–based products functionality. The results of phase equilibrium in different temperatures allow simulating melting curves and Differential Scanning Calorimetry curves, allowing a computational evaluation of how molecular structure and composition changes affect desired properties. The calculated results were applied and compared with experimental data in a wide range of systems: pure systems, binary and ternary triacylglycerol mixtures, natural vegetable oils and mixture of vegetable oils (hundreds of components). Chemical interesterification reaction, widely applied to change fats and oils composition and properties, were also simulated and the results compared with experimental data in different compositions and temperatures. The good agreement between computational results and experimental data enables the computational tool validation and its predictive nature makes it suitable for the study of mixtures in temperatures and compositions not yet evaluated. Consequently, the experimental efforts (cost and time) can be concentrated on the most promised molecules/mixtures. / A busca pelo desenvolvimento sustentável é um incentivo para o uso de recursos renováveis na indústria química. Óleos vegetais (misturas de triacilgliceróis) são matérias-primas que atendem a este critério e apresentam aplicações atuais e potenciais em diversos setores, tais como indústria de alimentos, lubrificantes, solventes, cosméticos, farmacêutica, dentre outros. Com o objetivo de auxiliar no desenvolvimento de produtos utilizando tais matérias-primas, o presente trabalho trata da modelagem do equilíbrio de fases em misturas de triacilgliceróis e do desenvolvimento de uma ferramenta computacional preditiva de propriedades. Os modelos usados são totalmente preditivos e consideram a existência de polimorfismo na fase sólida. O estado líquido e o polimorfo são considerados ideais. Os coeficientes de atividade das fases e (não-ideais) são estimados através do modelo de Margules, no qual os coeficientes de interação molecular binária são calculados de forma preditiva através de correlações com o grau de similaridade entre as cadeias de ácidos graxos no glicerol. Através da otimização direta da Energia Livre de Gibbs, é calculado o Conteúdo de Gordura Sólida, uma propriedade fundamental para funcionalidade de produtos baseados em óleos vegetais. Através do cálculo do equilíbrio de fases em diversas temperaturas são simuladas curvas de fusão e curvas de Calorimetria Exploratória Diferencial, permitindo uma avaliação computacional do efeito que alterações na estrutura molecular e composição apresentam nas propriedades de interesse. Os resultados calculados foram aplicados e comparados com dados experimentais em diversos sistemas: triacilgliceróis puros, misturas binárias e ternárias de triacilgliceróis, óleos vegetais naturais e misturas de diversos óleos vegetais (centenas de triacilgliceróis). Reações de interesterificação química, amplamente utilizadas para alterar a composição e propriedades de óleos e gorduras, foram igualmente simuladas e os resultados comparados com dados experimentais em diversas composições e temperaturas. A boa concordância entre os dados simulados e experimentais permite validar a ferramenta computacional e seu caráter preditivo a torna útil no estudo de misturas em temperaturas e composições ainda não avaliadas, de forma que os esforços experimentais (custo e tempo) possam ser direcionados às misturas mais promissoras.
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Carbohydrate-Rich Foods in the Treatment of the Insulin Resistance Syndrome : Studies of the Importance of the Glycaemic Index and Dietary FibreJärvi, Anette January 2001 (has links)
<p>The glycaemic responses to various carbohydrate-rich foods are partly dependent on the rate at which the carbohydrate is digested and absorbed. The glycaemic index (GI) is a way of ranking foods according to their glycaemic response and is recommended as a useful tool in identifying starch-rich foods that give the most favourable glycaemic response. This investigation was undertaken to determine whether carbohydrate-rich foods with a low GI and a high content of dietary fibre (DF) could have beneficial metabolic effects in the insulin resistance syndrome. This question was addressed both in single-meal studies and in randomised controlled clinical trials. Starch-rich foods with low GI values incorporated into composite meals resulted in lower postprandial responses of both glucose and insulin than foods with a high GI in meals with an identical macronutrient and DF composition, in subjects with type 2 diabetes. After three weeks on a diet including low GI starchy foods metabolic profile was improved in subjects with type 2 diabetes, compared with a corresponding high GI diet. The glucose and insulin responses throughout the day were lower, the total and low density lipoprotein cholesterol was decreased, and the fibrinolytic activity was normalised. In subjects with impaired insulin sensitivity and diabetes low GI foods rich in soluble DF for breakfast gave a more favourable metabolic profile, with smaller glucose fluctuations from baseline during the day, than a breakfast with high GI foods low in DF. A low GI breakfast high in DF also resulted in lower responses of insulin and C-peptide after breakfast and a lower triacylglycerol response after a standardised lunch. However, none of the tested breakfasts improved the glucose and insulin responses after lunch. Similar results were obtained in obese subjects after including a breakfast with a low GI high in soluble DF for a period of four weeks in comparison with a breakfast with a high GI and low content of DF.</p><p>These results support the therapeutic potential of a diet with a low GI in the treatment of diabetes and also in the treatment of several of the metabolic disturbances related to the insulin resistance syndrome.</p>
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Carbohydrate-Rich Foods in the Treatment of the Insulin Resistance Syndrome : Studies of the Importance of the Glycaemic Index and Dietary FibreJärvi, Anette January 2001 (has links)
The glycaemic responses to various carbohydrate-rich foods are partly dependent on the rate at which the carbohydrate is digested and absorbed. The glycaemic index (GI) is a way of ranking foods according to their glycaemic response and is recommended as a useful tool in identifying starch-rich foods that give the most favourable glycaemic response. This investigation was undertaken to determine whether carbohydrate-rich foods with a low GI and a high content of dietary fibre (DF) could have beneficial metabolic effects in the insulin resistance syndrome. This question was addressed both in single-meal studies and in randomised controlled clinical trials. Starch-rich foods with low GI values incorporated into composite meals resulted in lower postprandial responses of both glucose and insulin than foods with a high GI in meals with an identical macronutrient and DF composition, in subjects with type 2 diabetes. After three weeks on a diet including low GI starchy foods metabolic profile was improved in subjects with type 2 diabetes, compared with a corresponding high GI diet. The glucose and insulin responses throughout the day were lower, the total and low density lipoprotein cholesterol was decreased, and the fibrinolytic activity was normalised. In subjects with impaired insulin sensitivity and diabetes low GI foods rich in soluble DF for breakfast gave a more favourable metabolic profile, with smaller glucose fluctuations from baseline during the day, than a breakfast with high GI foods low in DF. A low GI breakfast high in DF also resulted in lower responses of insulin and C-peptide after breakfast and a lower triacylglycerol response after a standardised lunch. However, none of the tested breakfasts improved the glucose and insulin responses after lunch. Similar results were obtained in obese subjects after including a breakfast with a low GI high in soluble DF for a period of four weeks in comparison with a breakfast with a high GI and low content of DF. These results support the therapeutic potential of a diet with a low GI in the treatment of diabetes and also in the treatment of several of the metabolic disturbances related to the insulin resistance syndrome.
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Comparative Mapping of QTLs Affecting Oil Content, Oil Composition, and other Agronomically Important Traits in Oat (Avena sativa L.)Hizbai, Biniam T. 01 November 2012 (has links)
Groat oil content and composition are important quality traits in oats (Avena sativa L). These traits are controlled by many genes with additive effects. The chromosomal regions containing these genes, known as quantitative trait loci (QTL), can be discovered through their close association with markers. This study investigated total oil content and fatty acid components in an oat breeding population derived from a cross between high oil ('Dal') and low oil ('Exeter') parents. A genetic map consisting of 475 DArT (Diversity Array Technology) markers spanning 1271.8 cM across 40 linkage groups was constructed. QTL analysis for groat oil content and composition was conducted using grain samples grown at Aberdeen, ID in 1997. QTL analysis for multiple agronomic traits was also conducted using data collected from hill plots and field plots in Ottawa, ON in 2010. QTLs for oil content, palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3) were identified. Two of the QTLs associated with oil content were also associated with all of the fatty acids examined in this study, and most oil-related QTL showed similar patterns of effect on the fatty acid profile. These results suggest the presence of pleiotropic effects on oil-related traits through influences at specific nodes of the oil synthesis pathway. In addition, 12 QTL-associated markers (likely representing nine unique regions) were associated with plant height, heading date, lodging, and protein content. The results of this study will provide information for molecular breeding as well as insight into the genetic mechanisms controlling oil biosynthesis in oat.
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Meta-analysis and systematic review of the benefits expected when the glycaemic index is used in planning diets / Anna Margaretha OppermanOpperman, Anna Margaretha January 2004 (has links)
Motivation: The prevalence of non-communicable diseases such as diabetes mellitus (DM)
and cardiovascular disease (CVD) is rapidly increasing in industrialized societies. Experts
believe that lifestyle, and in particular its nutritional aspects, plays a decisive role in
increasing the burden of these chronic conditions. Dietary habits would, therefore, be
modified to exert a positive impact on the prevention and treatment of chronic diseases of
lifestyle. It is believed that the state of hyperglycaemia that is observed following food intake
under certain dietary regimes contributes to the development of various metabolic conditions.
This is not only true for individuals with poor glycaemic control such as some diabetics, but
could also be true for healthy individuals. It would, therefore, be helpful to be able to reduce
the amplitude and duration of postprandial hyperglycaemia. Selecting the correct type of
carbohydrate (CHO) foods may produce less postprandial hyperglycaemia, representing a
possible strategy in the prevention and treatment of chronic metabolic diseases. At the same
time, a key focus of sport nutrition is the optimal amount of CHO that an athlete should
consume and the optimal timing of consumption. The most important nutritional goals of the
athlete are to prepare body CHO stores pre-exercise, provide energy during prolonged
exercise and restore glycogen stores during the recovery period. The ultimate aim of these
strategies is to maintain CHO availability to the muscle and central nervous system during
prolonged moderate to high intensity exercise, since these are important factors in exercise
capacity and performance. However, the type of CHO has been studied less often and with
less attention to practical concerns than the amount of CHO.
The glycaemic index (GI) refers to the blood glucose raising potential of CHO foods and,
therefore, influences secretion of insulin. In several metabolic disorders, secretion of insulin
is inadequate or impossible, leading to poor glycaemic control. It has been suggested that
low GI diets could potentially contribute to a significant improvement of the conditions
associated with poor glycaemic control. Insulin secretion is also important to athletes since
the rate of glycogen synthesis depends on insulin due to it stimulatory effect on the activity of
glycogen synthase.
Objectives: Three main objectives were identified for this study. The first was to conduct a
meta-analysis of the effects of the GI on markers for CHO and lipid metabolism with the
emphasis on randomised controlled trials (RCT's). Secondly, a systematic review was
performed to determine the strength of the body of scientific evidence from epidemiological
studies combined with RCT's to encourage dieticians to incorporate the GI concept in meal
planning. Finally, a systematic review of the effect of the GI in sport performance was
conducted on all available literature up to date to investigate whether the application of the
GI in an athlete's diet can enhance physical performance.
Methodology: For the meta-analysis, the search was for randomised controlled trials with a
cross-over or parallel design published in English between 1981 and 2003, investigating the
effect of low GI vs high GI diets on markers of carbohydrate and lipid metabolism. The main
outcomes were serum fructosamine, glycosylated haemoglobin (HbA1c), high-density
lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), total cholesterol
(TC) and triacylglycerols (TG). For the systematic review, epidemiological studies as well as
RCT's investigating the effect of LGI vs HGI diets on markers for carbohydrate and lipid
metabolism were used. For the systematic review on the effect of the GI on sport
performance, RCT's with either a cross-over or parallel design that were published in English
between January 1981 and September 2004 were used. All relevant manuscripts for the
systematic reviews as well as meta-analysis were obtained through a literature search on
relevant databases such as the Cochrane Central Register of Controlled Trials, MEDLINE
(1981 to present), EMBASE, LILACS, SPORTDiscus, ScienceDirect and PubMed. This
thesis is presented in the article format.
Results and conclusions of the individual manuscripts:
For the meta-analysis, literature searches identified 16 studies that met the strict
inclusion criteria. Low GI diets significantly reduced fructosamine (p<0.05), HbA1c,
(p<0.03), TC(p<0.0001) and tended to reduce LDL-c (p=0.06) compared to high GI diets.
No changes were observed in HDL-c and TG concentrations. Results from this meta analysis,
therefore, support the use of the GI concept in choosing CHO-containing foods
to reduce TC and improve blood glucose control in diabetics.
The systematic review combined the results of the preceding meta-analysis and results
from epidemiological studies. Prospective epidemiological studies showed improvements
in HDL-c concentrations over longer time periods with low GI diets vs. high GI diets, while
the RCT's failed to show an improvement in HDL-c over the short-term. This could be
attributed to the short intervention period during which the RCT's were conducted.
Furthermore, epidemiological studies failed to show positive relationships between LDL-c
and TC and low GI diets, while RCT's reported positive results on both these lipids with
low GI diets. However, the epidemiological studies, as well as the RCT's showed positive
results with low GI diets on markers of CHO metabolism. Taken together, convincing
evidence from RCT's as well as epidemiological studies exists to recommend the use of
low GI diets to improve markers of CHO as well as of lipid metabolism.
3 From the systematic review regarding the GI and sport performance it does not seem that
low GI pre-exercise meals provide any advantages over high GI pre-exercise meals.
Although low GI pre-exercise meals may better maintain CHO availability during exercise,
low GI pre-exercise meals offer no added advantage over high GI meals regarding
performance. Furthermore, the exaggerated metabolic responses from high GI compared
to low GI CHO seems not be detrimental to exercise performance. However, athletes
who experience hypoglycaemia when consuming CHO-rich feedings in the hour prior to
exercise are advised to rather consume low GI pre-exercise meals. No studies have
been reported on the GI during exercise. Current evidence suggests a combination of
CHO with differing Gl's such as glucose (high GI), sucrose (moderate GI) and fructose
(low GI) will deliver the best results in terms of exogenous CHO oxidation due to different
transport mechanisms. Although no studies are conducted on the effect of the GI on
short-term recovery it is speculated that high GI CHO is most effective when the recovery
period is between 0-8 hours, however, evidence suggests that when the recovery period
is longer (20-24 hours), the total amount of CHO is more important than the type of CHO.
Conclusion: There is an important body of evidence in support of a therapeutic and
preventative potential of low GI diets to improve markers for CHO and lipid metabolism. By
substituting high GI CHO-rich with low GI CHO-rich foods improved overall metabolic control.
In addition, these diets reduced TC, tended to improve LDL-c and might have a positive
effect over the long term on HDL-c. This confirms the place for low GI diets in disease
prevention and management, particularly in populations characterised by already high
incidences of insulin resistance, glucose intolerance and abnormal lipid levels. For athletes it
seems that low GI pre-exercise meals do not provide any advantage regarding performance
over high GI pre-exercise meals. However, low GI meals can be recommended to athletes
who are prone to develop hypoglycaemia after a CHO-rich meal in the hour prior to exercise.
No studies have been reported on the effect of the GI during exercise. However, it has been
speculated that a combination of CHO with varying Gl's deliver the best results in terms of
exogenous CHO oxidation. No studies exist investigating the effect of the GI on short-term
recovery, however, it is speculated that high GI CHO-rich foods are suitable when the
recovery period is short (0-8 h), while the total amount rather than the type of CHO is
important when the recovery period is longer (20-24 h). Therefore, the GI is a scientifically
based tool to enable the selection of CHO-containing foods to improve markers for CHO and
lipid metabolism as well as to help athletes to prepare optimally for competitions.
Recommendations: Although a step nearer has been taken to confirm a place for the GI in
human health, additional randomised, controlled, medium and long-term studies as well as
more epidemiological studies are needed to investigate further the effect of low GI diets on
LDL-c. HDL-c and TG. These studies are essential to investigate the effect of low GI diets
on endpoints such as CVD and DM. This will also show whether low GI diets can reduce the
risk of diabetic complications such as neuropathy and nephropathy. Furthermore, the public
at large must be educated about the usefulness and application of the GI in meal planning.
For sport nutrition, randomised controlled trials should be performed to investigate the role of
the GI during exercise as well as in sports of longer duration such as cricket and tennis.
More studies are needed to elucidate the short-term effect of the GI post-exercise as well as
to determine the mechanism of lower glycogen storage with LGI meals post-exercise. / Thesis (Ph.D. (Dietetics))--North-West University, Potchefstroom Campus, 2005.
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Evaluation of Genes Encoding the Enzymes of the Kennedy Pathway in Soybeans with Altered Fatty Acid ProfilesMcNaughton, Amy J. M. 28 June 2012 (has links)
Soybean (Glycine max (L.) Merr) is the largest oil and protein crop in the world and it is grown for both oil and protein. To address the needs of both the edible oil market and industrial applications of soybean oil, fatty acid modification has been a focus of soybean breeding programs. Natural variation, mutagenesis and genetic engineering have been used to alter the fatty acid profile. Several genes, mostly desaturases, have been associated with altered fatty acid profiles but enzymes in the Kennedy Pathway have yet to be studied as another source of genetic variation for altering the fatty acid profiles. The Kennedy Pathway is also known as the oil producing pathway and consists of four enzymes: glycerol-3-phosphate acyltransferase (G3PAT); lysophosphatidic acid acyltransferase (LPAAT); phosphatidic acid phosphatase (PAP); and diacylglycerol acyltransferase 1 (DGAT1). The starting material for this pathway is glycerol-3-phosphate, which is produced from glycerol by glycerol kinase (GK), and the product of this pathway is triacylglycerol (TAG). The overall objective of this study was to elucidate the role that the Kennedy Pathway plays in determining the fatty acid profile in two ways: (1) sequencing the transcribed region of the genomic genes encoding the enzymes of GK, G3PAT, LPAAT, and DGAT1 in soybean genotypes with altered fatty acid profiles; and (2) studying their expression over seed development, across three growing temperatures. The genetic material for the study consisted of four soybean genotypes with altered fatty acid profile: RG2, RG7, RG10, and SV64-53. Results from sequencing showed that the mutations identified in G3PAT, LPAAT, and DGAT1 in the four soybean genotypes did not explain the differences in the fatty acid profiles. The expression of G3PAT, LPAAT, and DGAT1 over seed development showed that G3PAT had the lowest levels, followed by LPAAT, then DGAT1, across the growing temperatures. The differences in expression among genotypes corresponded to differences in fatty acid accumulation, suggesting that expression rather than genetic mutations in the transcribed region of the genes influenced the fatty acid profile of the genotypes in this study. In conclusion, the enzymes of the Kennedy Pathway appear to contribute to the altered fatty acid profiles observed in the soybean mutant genotypes. / Ontario Ministry of Economic Development and Innovation (formerly Ontario Ministry of Research and Innovation), BioCar Initiative, Grain Farmers of Ontario, SeCan
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