Poor food quality can have large negative effects on zooplankton growth and this can also affect food web interactions. The main aims of this thesis were to study the importance of different food quality aspects in Daphnia, to identify potentially important differences among zooplankton taxa, and to put food quality research into a natural context by identifying the importance of food quality and quantity in lakes of different nutrient content. In the first experiment, the RNA:DNA ratio was positively related to the somatic growth rate of Daphnia, supporting a connection between P content, RNA content, and growth rate. The second experiment showed that EPA was important for Daphnia somatic growth, and 0.9 µg EPA mg C-1 was identified as the threshold below which negative effects on Daphnia growth occurred. A field survey identified patterns in the PUFA content of zooplankton that could be explained by taxonomy and trophic position. Cladocera enriched EPA and ARA relative to seston, and Copepoda primarily enriched DHA. In a whole-lake experiment, gentle fertilization of an oligotrophicated reservoir increased the seston P content and the biomass of high quality phytoplankton (Cryptophyceae, high EPA content). This was followed by increases in zooplankton and fish biomasses. An empirical model based on data from a literature survey predicted that food quantity is most important for zooplankton growth in oligotrophic lakes, and that food quality factors are more important in eutrophic lakes. Thus, zooplankton growth, and energy transfer efficiency in the food web, is predicted to be highest in mesotrophic lakes. The results predict that the strength and nature of food quantity and quality limitation of Daphnia growth varies with lake trophic state, and that some combination of food quantity and/or quality limitation should be expected in nearly all lakes.

Obesity is widely considered a primary risk factor for type 2 diabetes (T2D). However, less is known about the early adaptive responses to short-term periods of high-fat energy excess (HFEE). Previous reports detailing whole-body adaptation to fat and energy oversupply are equivocal, perhaps, in part, owing to use of different experimental protocols, varying durations of dietary manipulation and participant cohorts with individuals of varying characteristics. In addition to use of different dietary protocols between studies, alterations in functional end-point measures due to the type of dietary fat consumed warrants consideration. Daily n-3 PUFA intake, commonly obtained from pelagic fish oil (FO) consumption, has been shown to positively associate with insulin sensitivity in epidemiological studies and thus may be a useful dietary strategy for slowing insulin resistance development. Chapter 2 of this thesis extends previous literature by demonstrating that 6 d HFEE (150 % habitual energy intake; 60 % of energy from fat) does not clearly alter whole- body insulin sensitivity, irrespective of FO consumption. However, investigation of metabolism at the tissue level, as presented in Chapter 3 of this thesis, offers insight into a potential tissue-specific level of regulation that precedes whole-body regulation. Skeletal muscle insulin signalling protein (e.g. protein kinase B (PKB)) activity, levels of certain ceramide species, and AMPK α2 activity were altered following HFEE and may explain the early maladaptive responses to short-term HFEE. Moreover, FO intake as 10 % of total fats mediated some of these molecular responses, including PKB and AMPK α2 activity, reflecting possible functional effects of FO at the subcellular level. Regulation of these metabolic / molecular responses at both the tissue and whole- body level can be explained, in part, by genetic predisposition, environmental influence and more recently epigenetics, including microRNAs (miRNAs). In Chapter 4, we characterised the plasma and skeletal muscle miRNA responses to HFEE and oral glucose ingestion. We demonstrate transient changes in levels of certain miRNAs following oral glucose ingestion in both tissue types and in response to HFEE in skeletal muscle. However, no significant correlations between basal plasma and skeletal muscle miRNA levels were observed, suggesting that our candidate plasma miRNAs may be co-ordinating functional changes in other tissue types. Plasma miR- 145-5p and skeletal muscle miR-204-5p predicted a significant proportion of the variance in mean whole-body insulin sensitivity change in response to HFEE. These data indicate that these miRNAs may be useful biomarkers of insulin resistance development following HFEE. A constraint of this thesis is that all conclusions are made within the context of statistically unaltered insulin sensitivity. Therefore, future investigations of diet-induced maladaptation should consider establishing a time course of insulin resistance development in response to HFEE, or use different study populations. Populations that are more susceptible to T2D development, e.g., overweight, sedentary individuals would be of particular interest. These data would aid development of a working model of diet-induced insulin resistance that has more direct application to T2D progression and extends the data presented herein.

O objetivo deste trabalho foi avaliar os efeitos de dois modificadores metabólicos, a sesamina, presente no óleo de gergelim, e ácido alfa-lipoico (na forma pura), sobre desempenho zootécnico, perfil de ácidos graxos, composição química dos filés de pacus e alterações histológicas no fígado. Foram utilizados 480 juvenis de pacu (3,35±0,78 g), distribuídos em 24 caixas de polietileno com volume de 50 litros, sendo estocados 20 peixes em cada unidade. Durante o período experimental de 90 dias, a temperatura média da água permaneceu em 26 °C e os demais parâmetros (amônia, nitrito, pH e oxigênio dissolvido) apresentaram-se dentro dos níveis adequados para o desenvolvimento desta espécie. O delineamento experimental foi inteiramente casualizado, no qual foram avaliados seis tratamentos em esquema fatorial 3x2, sendo três níveis do fator óleo (OS: óleo de soja; OG: óleo de gergelim; OL: óleo de linhaça) e dois níveis do fator ácido alfa-lipoico (AAL) (sem e com), resultando em seis tratamentos: T1: OS (controle); T2: OG+OL; T3: OL; T4: OS+AAL; T5: OG+OL+AAL e T6: OL+AAL. Os dados obtidos foram analisados estatisticamente por análise de variância (ANOVA) e diferenças significativas foram verificadas pelo teste de Tukey (5%). As dietas contendo OL como única fonte lipídica (T3 e T6) proporcionaram melhores índices de peso médio (PM) e ganho de peso individual (GPI) nos juvenis de pacu. Além disso, proporcionaram maiores (P<0,05) teores de ácidos graxos poli-insaturados (AGPI) da família n-3 nos filés, especialmente do ácido eicosapentaenoico (EPA, 20:5n-3). A única variável da composição química dos filés dos juvenis de pacu que apresentou diferença (P<0,05) foi o teor de proteína bruta, sendo maior nos filés dos peixes alimentados com as dietas sem ácido alfa-lipoico (T4, T5 e T6). Os óleos utilizados nas dietas experimentais não causaram alterações nas células dos fígados de juvenis de pacu. Conclui-se que a sesamina, fornecida por meio de óleo de gergelim, não promoveu alterações no desempenho zootécnico dos pacus, nem na composição química e metabolismo de ácidos graxos poli-insaturados (AGPI) dos filés de juvenis de pacu. A presença do ácido alfa-lipoico não afetou o desempenho zootécnico dos animais e sua ausência promoveu maiores teores de proteína bruta e ácidos graxos poli-insaturados nos filés dos pacus. / The objective of this work was to evaluate the effects of two metabolic modifiers, sesamin, present in sesame oil, and alpha lipoic acid (in pure form), on pacus growth performance, fatty acid profile, chemical composition of pacus fillets and histological alterations in the liver. We used 480 pacu juveniles (3.35±0.78 g), distributed in 24 boxes of polyethylene with volume of 50 liters, being stored 20 fish in each unit. During the experimental period of 90 days, the mean water temperature remained at 26 °C and the other parameters (ammonia, nitrite, pH and dissolved oxygen) were in the appropriate levels for the development of this species. The experimental design was completely randomized, in which six treatments were evaluated in a 3x2 factorial scheme, being three levels of the factor oil (OS: soybean oil, OG: sesame oil, OL: linseed oil) and two levels of the alpha acid factor -lipoic acid (AAL) (without and with), resulting in six treatments: T1: OS (control); T2: OG+OL; T3: OL; T4: OS+AAL; T5: OG+OL+AAL and T6: OL+AAL. Data were analyzed statistically by analysis of variance (ANOVA) and significant differences were verified by the Tukey test (5%). Diets containing OL as the only lipid source (T3 and T6) provided better average weight (PM) and individual weight gain (GPI) in pacu juveniles. In addition, they provided higher (P <0.05) levels of polyunsaturated fatty acids (PUFA) of the n-3 family in fillets, especially eicosapentaenoic acid (EPA, 20:5n-3). The only variable of the chemical composition of pacu juvenile fillets that presented a difference (P <0.05) was the crude protein content, being higher in the fish fillets fed the diets without alpha-lipoic acid (T4, T5 and T6). The oils used in the experimental diets did not cause changes in the livers cells of pacu juveniles. It was concluded that sesamin, provided by sesame oil, did not promote changes in the growth performance of pacus, nor in the chemical composition and metabolism of polyunsaturated fatty acids (PUFA) of pacu juvenile fillets. The presence of alpha-lipoic acid did not affect the animals growth performance and its absence promoted higher levels of crude protein and polyunsaturated fatty acids in pacus fillets.

Os óleos vegetais constituem-se uma das fontes mais acessíveis da vitamina E pela população, sendo que o Brasil ocupa posição de destaque na América Latina como produtor e consumidor de óleos vegetais. Atualmente, dentre os óleos de maior consumo estão soja, palma, canola e girassol. As isoformas de vitamina E compreendem uma classe de oito compostos distintos denominados tocoferóis e tocotrienóis, sendo o α-tocoferol a isoforma de maior notoriedade, por sua conhecida ação antioxidante em sistemas biológicos e também como antioxidante natural na indústria de alimentos. A eficiência nutricional de um composto pode estar relacionada com a bioacessibilidade. Bioacessibilidade é a fração do nutriente que é liberada da matriz alimentar para a região gastrointestinal e está passível de absorção, podendo ser afetada por diversos fatores relacionados à própria matriz alimentar. Dessa forma, o objetivo desse estudo foi inicialmente quantificar as isoformas de vitamina E em quatro óleos refinados (girassol, canola, palma e milho) e avaliar a bioacessibilidade da vitamina E nesses óleos antes e após tratamento térmico. O tratamento térmico utilizado foi a fritura contínua em batatas (1 h a 180°C). Foi realizada a caracterização físico-química dos óleos vegetais refinados, antes e após o processo de fritura e verificado parâmetros de qualidade dos óleos. Para isso foram realizadas as análises de umidade da batata, teor de ácidos graxos livres, índice de peróxidos, composição em ácidos graxos e estabilidade oxidativa. A quantificação das isoformas de vitamina E foi realizada por CLAE acoplada ao detector de fluorescência, e para a determinação da bioacessibilidade da vitamina E, foi utilizado um modelo in vitro com cultivo de células Caco-2. O óleo de palma apresentou bioacessibilidade superior aos demais óleos estudados, seguido do óleo de milho, canola e girassol. A fritura contínua por 1 hora reduziu significativamente os teores totais de tocoferóis e tocotrienóis, e influenciou positivamente sobre a vitamina E na fração bioacessível. / The vegetable oils are one of the most acessible sources of vitamin E by the population, and Brazil occupies the leading position in Latin America as a producer and consumer of vegetable oils. Currently, soybean, palm, canola and sunflower oils are among the most consumed oils. The vitamin E isomers comprise the class of eight distinct components called tocopherols and tocotrienols, with α-tocopherol being the most notorious isomer, due to its known antioxidant action in biological systems and also as a natural antioxidant in the food industry. The nutritional efficiency of compounds may be related to bioaccessibility. Bioaccessibility is the fraction of the nutrient that is released from the food matrix into the gastrointestinal region and is passible toabsortion, which can be affected by several factors related to the food matrix. Thus the objective of this study was to quantify vitamin E isomers in four refined oils (sunflower, canola, palm and corn) and to evaluate the its bioaccessibility in these oils before and after heat treatment. The heat treatment used was the continuous frying of potatoes (1 h at 180 °C). The physico-chemical characterization of refined vegetable oils before and after the frying process was carried out, and the quality parameters of the oils were verified. For this, the potato moisture and the content of free fatty acids, peroxide index, fatty acid profile of the oils were carried out. Quantification of vitamin E isomers was performed by HPLC coupled to a fluorescence detector, and an in vitro model of Caco-2 cell culture was used to determine the bioacessibility of vitamin E. Palm oil had higher bioaccessibility than corn, canola and sunflower oil. Continuous frying for 1 hour significantly reduced the total contents of tocopherols and tocotrienols, and positively influenced by the vitamin E in the bioaccessible fraction.

O objetivo deste trabalho foi avaliar os efeitos de dois modificadores metabólicos, a sesamina, presente no óleo de gergelim, e ácido alfa-lipoico (na forma pura), sobre desempenho zootécnico, perfil de ácidos graxos, composição química dos filés de pacus e alterações histológicas no fígado. Foram utilizados 480 juvenis de pacu (3,35±0,78 g), distribuídos em 24 caixas de polietileno com volume de 50 litros, sendo estocados 20 peixes em cada unidade. Durante o período experimental de 90 dias, a temperatura média da água permaneceu em 26 °C e os demais parâmetros (amônia, nitrito, pH e oxigênio dissolvido) apresentaram-se dentro dos níveis adequados para o desenvolvimento desta espécie. O delineamento experimental foi inteiramente casualizado, no qual foram avaliados seis tratamentos em esquema fatorial 3x2, sendo três níveis do fator óleo (OS: óleo de soja; OG: óleo de gergelim; OL: óleo de linhaça) e dois níveis do fator ácido alfa-lipoico (AAL) (sem e com), resultando em seis tratamentos: T1: OS (controle); T2: OG+OL; T3: OL; T4: OS+AAL; T5: OG+OL+AAL e T6: OL+AAL. Os dados obtidos foram analisados estatisticamente por análise de variância (ANOVA) e diferenças significativas foram verificadas pelo teste de Tukey (5%). As dietas contendo OL como única fonte lipídica (T3 e T6) proporcionaram melhores índices de peso médio (PM) e ganho de peso individual (GPI) nos juvenis de pacu. Além disso, proporcionaram maiores (P<0,05) teores de ácidos graxos poli-insaturados (AGPI) da família n-3 nos filés, especialmente do ácido eicosapentaenoico (EPA, 20:5n-3). A única variável da composição química dos filés dos juvenis de pacu que apresentou diferença (P<0,05) foi o teor de proteína bruta, sendo maior nos filés dos peixes alimentados com as dietas sem ácido alfa-lipoico (T4, T5 e T6). Os óleos utilizados nas dietas experimentais não causaram alterações nas células dos fígados de juvenis de pacu. Conclui-se que a sesamina, fornecida por meio de óleo de gergelim, não promoveu alterações no desempenho zootécnico dos pacus, nem na composição química e metabolismo de ácidos graxos poli-insaturados (AGPI) dos filés de juvenis de pacu. A presença do ácido alfa-lipoico não afetou o desempenho zootécnico dos animais e sua ausência promoveu maiores teores de proteína bruta e ácidos graxos poli-insaturados nos filés dos pacus. / The objective of this work was to evaluate the effects of two metabolic modifiers, sesamin, present in sesame oil, and alpha lipoic acid (in pure form), on pacus growth performance, fatty acid profile, chemical composition of pacus fillets and histological alterations in the liver. We used 480 pacu juveniles (3.35±0.78 g), distributed in 24 boxes of polyethylene with volume of 50 liters, being stored 20 fish in each unit. During the experimental period of 90 days, the mean water temperature remained at 26 °C and the other parameters (ammonia, nitrite, pH and dissolved oxygen) were in the appropriate levels for the development of this species. The experimental design was completely randomized, in which six treatments were evaluated in a 3x2 factorial scheme, being three levels of the factor oil (OS: soybean oil, OG: sesame oil, OL: linseed oil) and two levels of the alpha acid factor -lipoic acid (AAL) (without and with), resulting in six treatments: T1: OS (control); T2: OG+OL; T3: OL; T4: OS+AAL; T5: OG+OL+AAL and T6: OL+AAL. Data were analyzed statistically by analysis of variance (ANOVA) and significant differences were verified by the Tukey test (5%). Diets containing OL as the only lipid source (T3 and T6) provided better average weight (PM) and individual weight gain (GPI) in pacu juveniles. In addition, they provided higher (P <0.05) levels of polyunsaturated fatty acids (PUFA) of the n-3 family in fillets, especially eicosapentaenoic acid (EPA, 20:5n-3). The only variable of the chemical composition of pacu juvenile fillets that presented a difference (P <0.05) was the crude protein content, being higher in the fish fillets fed the diets without alpha-lipoic acid (T4, T5 and T6). The oils used in the experimental diets did not cause changes in the livers cells of pacu juveniles. It was concluded that sesamin, provided by sesame oil, did not promote changes in the growth performance of pacus, nor in the chemical composition and metabolism of polyunsaturated fatty acids (PUFA) of pacu juvenile fillets. The presence of alpha-lipoic acid did not affect the animals growth performance and its absence promoted higher levels of crude protein and polyunsaturated fatty acids in pacus fillets.

Intake of polyunsaturated fatty acids (PUFA) has changed drastically in the past century in the American diet has received attention due to potential effects on chronic inflammation-related metabolic diseases. In this project, the effects of dietary PUFA content and the n-6 to n-3 ratio on inflammatory responses in the acute and chronic inflammation models were evaluated. The PUFA content was modified on a Western diet background to deliver both n-6 and n-3 intakes at the 10th and 90th percentile of the population in the United States, and models of acute and chronic inflammation were tested in mice model. The experimental PUFA diets had a modest effect on the response to lipopolysaccharide (LPS) in the acute inflammation model. A high n-6 to n-3 ratio promoted lipogenesis. In addition, high n-6 PUFA enhanced the inflammatory responses via the NF-κB pathway. In chronic inflammation model, low-grade inflammatory stress was induced by osmotic mini-pump delivery of LPS. A high n-6 intake increased glucose intolerance. On the other hand, high n-6 intake promotes cholesterol ester accumulation in both acute and chronic inflammation models.

The role of dietary fatty acids and their subsequent effects on metabolism has received considerable attention in mammalian species. It is becoming increasingly clear that fatty acids have metabolic roles over and above their influence on energy density of the diet. Recent studies have linked changes in the fatty acyl composition of the plasma membrane, induced by the dietary fat profile, to alterations in both lipid and glucose metabolism. These dietary induced changes have profound effects on insulin action, glucose transport and enzyme activity that regulate triglyceride and fatty acid synthesis, factors that ultimately influence protein and lipid deposition of animals. Because of their high growth rate, broiler chickens have a high requirement for energy and the use of triglycerides as a major energy source has resulted in a fat carcass. A change in the glucose-insulin balance has been suggested as being the main reason for differences in adiposity between broilers selected for fatness or leanness. The hypotheses of this thesis is based on the finding that dietary polyunsaturated fatty acids (PUFA�s) increase the sensitivity of muscle tissue to insulin and this would presumably augment insulin-stimulated glucose uptake into muscle cells. Therefore, increasing the capacity of broiler muscle tissue to utilise glucose as its principal energy substrate would reduce the bird�s reliance on triglycerides and this inturn would result in a leaner carcass. The aims of this study are firstly to explore the role that dietary PUFA�s from the n-3 and n-6 series have on the growth and body composition of broiler chickens and secondly to determine the relationships between dietary fatty acid profile, tissue insulin sensitivity and lipid deposition. Because dietary fatty acids have been implicated in the modulation of hormones important for the growth and development of animals, a third aim of this thesis is to determine the effects of dietary n-3 and n-6 polyunsaturated fatty acids on pituitary and adrenal sensitivity. Since the modulation of metabolism by dietary fatty acids has been attributed to changes in the fatty acyl composition of the plasma membrane, the final aim of this study will be to investigate and characterise the molecular species of the breast muscle choline and ethanolamine phospholipids. Feeding either fish oil a source of n-3 PUFA�s or sunflower oil a source of n-6 PUFA�s fatty acids to broiler chickens resulted in a significant (P<0.01) reduction in the abdominal fat pad mass and a modest increase in breast muscle mass when compared to broilers fed edible tallow. Associated with the changes in carcass composition was an alteration in energy substrate utilisation. This was reflected by lower respiratory quotients and reduced triglyceride and insulin concentrations for the chickens fed the two PUFA diets. Coupled to the shift in energy metabolism was a significant (P<0.05) increase in the proportion of PUFA�s incorporated into the abdominal fat pad and breast muscle. The dietary fat supplements resulted in the incorporation of specific fatty acid subtypes. Feeding fish oil significantly increased the proportion of long-chain n-3 PUFA�s whereas feeding sunflower oil significantly increased the proportion of long-chain n-6 PUFA�s compared to tallow feeding whose tissues were dominated by a higher proportion of saturated fatty acids. It was further shown that dietary n-3 and n-6 PUFA�s enhanced glucose /insulin action. Feeding either fish oil or sunflower oil to broiler chickens increased insulin action when examined by an intravenous glucose tolerance test. The maximal insulin release in response to the glucose infusion was higher in the tallow fed group compared to either the sunflower oil or fish oil groups. To estimate the disappearance rate of glucose from the plasma and its incorporation into tissues, 2-deoxy-D-3H glucose was infused into each chicken. There were no significant differences in the clearance rate of 2-deoxy-D-3H glucose from the plasma. However, when measured under steady state conditions, the labelled glucose incorporation into the breast muscle was greater in birds fed fish oil compared to either tallow or sunflower oil feeding. The dietary fatty acid induced increase in insulin action suggests that the sensitivity of muscle cells to insulin was enhanced. This modulation of tissue sensitivity by dietary fatty acids was also shown to occur at the level of the pituitary. To provide an estimate of pituitary sensitivity, bolus GnRH and GHRH infusions were given on different days to chickens fed the three dietary treatments. Feeding sunflower oil (n-6 PUFA�s) increased the level of GH that was released in response to the GHRH infusion when compared to birds fed either tallow or fish oil (n-3 PUFA�s). This dietary fatty acid modulation appears to be specific to certain pituitary cell types as there was no effect on LH secretion following the GnRH infusion. Dietary fatty acid modulation of endocrine gland sensitivity is particular to the gland type. Although the dietary treatments mediated a distinct pattern in pituitary sensitivity to GHRH infusion, these same three diets did not influence adrenal sensitivity, as there was no difference in the corticosterone profile following either ACTH or CRF infusion. The previously observed physiological changes for the three dietary groups was expected to be positively correlated to an alteration of the plasma membrane phospholipids induced by the dietary fatty acids. Supplementation with fish oil (n-3 PUFA�s) significantly increased levels of both eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) into the choline (PC) and ethanolamine (PE) breast muscle phospholipids compared to either sunflower oil (n-6 PUFA�s) or tallow supplementation. The increase in n-3 PUFA incorporation was associated with a corresponding decrease in the proportion of arachidonic acid (AA; 20:4n-6) an event that would presumably alter substrate availability for the 1- and 2-series eicosanoids. However, feeding sunflower oil or tallow gave a molecular species profile that was remarkably similar in both fatty acid subtype and proportion. This suggests that the plasma membrane dynamics would be similar for these two dietary groups. Therefore, it is appears that factors other than a change in the fatty acyl- composition of the plasma membrane may be responsible for modifying the physiology of the broiler.

<p>Poor food quality can have large negative effects on zooplankton growth and this can also affect food web interactions. The main aims of this thesis were to study the importance of different food quality aspects in <i>Daphnia</i>, to identify potentially important differences among zooplankton taxa, and to put food quality research into a natural context by identifying the importance of food quality and quantity in lakes of different nutrient content.</p><p>In the first experiment, the RNA:DNA ratio was positively related to the somatic growth rate of <i>Daphnia</i>, supporting a connection between P content, RNA content, and growth rate. The second experiment showed that EPA was important for <i>Daphnia</i> somatic growth, and 0.9 µg EPA mg C^-1 was identified as the threshold below which negative effects on <i>Daphnia</i> growth occurred.</p><p>A field survey identified patterns in the PUFA content of zooplankton that could be explained by taxonomy and trophic position. <i>Cladocera</i> enriched EPA and ARA relative to seston, and <i>Copepoda</i> primarily enriched DHA. In a whole-lake experiment, gentle fertilization of an oligotrophicated reservoir increased the seston P content and the biomass of high quality phytoplankton (<i>Cryptophyceae</i>, high EPA content). This was followed by increases in zooplankton and fish biomasses.</p><p>An empirical model based on data from a literature survey predicted that food quantity is most important for zooplankton growth in oligotrophic lakes, and that food quality factors are more important in eutrophic lakes. Thus, zooplankton growth, and energy transfer efficiency in the food web, is predicted to be highest in mesotrophic lakes. The results predict that the strength and nature of food quantity and quality limitation of <i>Daphnia</i> growth varies with lake trophic state, and that some combination of food quantity and/or quality limitation should be expected in nearly all lakes.</p>

Omega-3 polyunsaturated fatty acids (n-3 PUFA) enriched eggs are an increasingly important contributor to the egg industry due to the health benefits of n-3 PUFA. During storage and cooking, n-3 PUFA could undergo oxidation and further cause cholesterol oxidation. This study examined stability of n-3 PUFA enriched eggs fortified with antioxidants (vitamin E or organic Selenium [Sel-Plex] or both) following storage and cooking. Total n-3 PUFA was not affected by cooking and storage, although long chain n-3 PUFA concentration decreased. Overall, both vitamin E and Sel-Plex decreased oxidation of yolk lipids and cholesterol. Cooking increased the lipid and cholesterol oxidation. Four weeks of storage did not affect the cholesterol oxidation products (COPs) content, but increased lipid oxidation. It is possible to make the n-3 PUFA in enriched eggs more stable with dietary antioxidants. / Food Science and Technology

Adipose tissue is well-recognized as an endocrine organ which secretes a variety of bioactive molecules, including angiotensin II and its precursor angiotensinogen (Agt). There is mounting evidence linking the adipose renin-angiotensin system (RAS) and diet to obesity and obesity-related disorders. However, research addressing dietary regulation and function of adipose RAS is limited, and the specific mechanisms by which PUFAs modulate the endocrine function of adipose tissue remain largely unclear. There are several potential mechanisms that may mediate PUFA effects on Agt, including toll-like receptor signalling, prostaglandins or PPAR-gamma. Thus, we propose to investigate whether PUFAs differentially modulate Agt expression and secretion and to examine possible mechanisms by which PUFA alter Agt expression using the 3T3-L1 cell line. Differentiated 3T3-L1 adipocytes were treated with arachidonic acid (AA), eicosapentaenoic acid (EPA), AA + EPA, or vehicle (C) for 48 hours. Results showed a significant increase in intracellular Agt protein following treatment with PUFAs. Agt secretion, however, was only increased by AA. Interestingly, there is a dose-dependent decrease in Agt protein levels by EPA suggesting that a minimum concentration of n-3 PUFAs is required to elicit an Agt response. Agt mRNA levels were measured by RT-PCR and results showed a significant increase in Agt mRNA in response to treatment with AA but not EPA. These findings suggest that Agt regulation by PUFAs is complex and occurs both post-transcriptionally and post-translationally. Changes in mRNA stability may account for the observed effects of PUFAs. Adipocytes were treated with the transcriptional inhibitor actinomycin D (Act D) and Agt mRNA expression was measured over time. Total RNA was also measured at each time point to ensure that Act D treatment was effectively decreasing transcription. Agt mRNA expression was not significantly altered by treatment with EPA while treatment with AA increased Agt mRNA levels. These results suggest that Agt mRNA stability is differentially increased by n-6 but not n-3 PUFAs. Although there are clear effects of AA on Agt secretion and mRNA stability, the signaling pathways mediating this response remain to be determined, and additional studies are necessary to further dissect the underlying mechanisms of this regulation.