<p> Dietary fat provides essential nutrients, contributes to energy intake and regulates blood lipid levels. These functions are important to health; however, when dysregulated they contribute to dyslipidemia and increase risk for development of obesity, diabetes and cardiovascular disease. </p><p> Dietary fat absorption is efficiently mediated by the small intestine. The digested products of dietary fat in the gut lumen are taken up by enterocytes, the absorptive cells of the intestine, where they are re-synthesized to triacylglycerol (TAG). The resulting TAG is packaged onto chylomicrons (CMs) for secretion into the circulation, contributing to postprandial blood lipid levels. When levels of dietary fat are high, TAG is also packaged into cytoplasmic lipid droplets (CLDs) for temporary storage within enterocytes. The CLDs increase and then decrease overtime in response to fat consumption, indicating that the stored TAG is mobilized for secretion or to the other fates at later time points. The intestinal metabolism of CMs and CLDs together regulate the rate and the amount of TAG secreted into the circulation. The objective of this dissertation work is to explore the mechanisms through which the TAG is partitioned or mobilized to certain metabolic fates in enterocytes. </p><p> First, we investigated the effect of endurance exercise on genes of intestinal lipid metabolism using Otsuka Long-Evans Tokushima Fatty (OLETF), an obese and diabetic rat model. We found that exercise training in these animals resulted in parallel upregulations of genes involved in TAG anabolic and catabolic processes and promoted mitochondrial biosynthesis in enterocytes compared to sedentary rats. We proposed that these changes lead to a more efficient fatty acid oxidation in the intestine and a consequent reduction of intestinal TAG secretion in this model. Overall, this work highlights that endurance exercise training programs intestinal lipid metabolism, contributing to the beneficial effect of endurance exercise on improving obesity and metabolic disease. </p><p> Nest, we investigated the differential roles of acyl CoA: diacylglycerol acyltransferase 1 (Dgat1) and Dgat2, in regulating dietary fat absorption. Mice with intestine-specific overexpression of Dgat1 (<i>Dgat1</i>^Int) or Dgat2 (<i>Dgat2</i>^Int), or lack of Dgat1 (<i>Dgat1</i>^{&ndash;/&ndash;}) were previously reported to have different intestinal phenotypes in response to fat consumption and altered susceptibilities to obesity and hepatic steatosis; the underlying mechanism(s) is unknown. By conducting an ultrastructural analysis on enterocytes from these Dgat mouse models in response to fat consumption, we found that Dgat1 and Dgat2 altered intracellular TAG distribution for CM and CLD synthesis. Based on the observations in the study, Dgat1 is proposed to preferentially synthesize TAG for the subcellular pool that promotes CM expansion in the ER lumen and thus limits TAG storage in CLDs. In addition, Dgat2 is proposed to preferentially synthesize TAG for the subcellular pool that determines the number of CMs generated in the ER lumen and for storage in CLDs. In this study, we provide the mechanism of how intestinal Dgat1 and Dgat2 exert regulatory effects on postprandial blood lipid levels and whole-body physiology. Overall, this work demonstrates non-redundant cellular roles of Dgat1 and Dgat2 in dietary fat absorption. </p><p> Lastly, we investigated the regulation of lipophagy, where CLDs are targeted by autophagy and catabolized in acidic lysosomes, in enterocytes of <i> Dgat1</i>^{&ndash;/&ndash;} mice. We found an increased number of autophagic vesicle (AV) and abnormal TAG accumulation within AVs in enterocytes of <i>Dgat1</i>^{&ndash;/&ndash;} compared to WT mice, suggesting an impaired AV turnover and an inefficient lipophagy by Dgat1 deficiency. In addition, we identified that this impaired lipophagy process was due to a lysosome dysfunction, as indicated by the decreased mRNA levels of genes involved in lysosome acidification and higher lysosome pH in enterocytes of <i>Dgat1</i>^{&ndash;/&ndash;} compared to WT mice. Furthermore, we found alterations in cellular lipid composition and levels of reactive oxygen species (ROS) in enterocytes of <i>Dgat1 </i>^{&ndash;/&ndash;} compared to WT mice. These changes may possibly contribute to the lysosome dysfunction seen in <i>Dgat1 </i>^{&ndash;/&ndash;} mice. Based on the results in the study, we propose that the lysosome dysfunction limits lipid supply from the storage pool for secretion, resulting in a greater intestinal TAG storage and a reduced rate of intestinal TAG secretion seen in <i>Dgat1</i>^{&ndash;/&ndash;} mice. Together, this study highlights that lysosome function plays a critical role in lipophagy and that lipophagy may serve as a potential target for treating postprandial hyperlipidemia and its related diseases. </p><p> The findings presented in this dissertation expand the current knowledge of regulation of dietary fat absorption. The proposed models generated from these studies provide novel therapeutic strategies for managing postprandial blood lipid levels and preventing obesity and its related diseases.</p><p>

The carotenoid tradeoff hypothesis states that diet-derived carotenoids are traded-off among competing physiological demands, but this statement is rarely tested in ornamented females. The following dissertation tests the carotenoid tradeoff hypothesis in reverse sexually dimorphic convict cichlids (Amantitlania siquia) using carotenoid-supplemented diet treatments and a field-based study of carotenoid intake. Spectral, microscopic, and chemical analysis determined how females allocated the pigments to tissues and how those decisions affected their ventral patch coloration. The results presented in the current study show that carotenoids enhance offspring growth and survival, lower oxidative stress, and reduce the time to clear a parasite. The two final chapters suggest that carotenoid limitation and absorption may not explain carotenoid allocation dynamics in A. siquia. The final chapter proposes an alternative to the carotenoid tradeoff hypothesis as a mechanism to explain the relationship among color, parasites, and oxidative stress.

Orientadores: Bayardo Baptista Torres, Eduardo Galembeck / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-05T12:48:31Z (GMT). No. of bitstreams: 1 Yokaichiya_DanielaKiyoko_D.pdf: 3705670 bytes, checksum: 354ac01fec4579915cc806d0ea872315 (MD5) Previous issue date: 2005 / Resumo: Após a realização de uma pesquisa de interesse, o curso a distância Bioquímica da Nutrição foi elaborado e oferecido em 2000, para alunos de graduação da Universidade de São Paulo (USP) e Universidade Estadual de Campinas (Unicamp) que contemplam disciplina de Bioquímica Básica na grade curricular. Os resultados da pesquisa mostraram que o interesse não se limita a alunos das duas instituições citadas, mas estende-se a estudantes e profissionais de todo país. Esta observação despertou o interesse em reestruturar o curso para ser oferecido a um público maior e mais diversificado. Em se tratando de uma iniciativa inédita, fez-se necessária a análise do uso de novas tecnologias de comunicação para o ensino e a realização de avaliações do processo de ensino-aprendizagem para verificar a eficiência de cursos a distância. Assim, através deste trabalho pretendeu-se: (1) estruturar o curso a distância Bioquímica da Nutrição baseando-se nos resultados das avaliações feitas pelos alunos; (2) oferecer o curso reestruturado a um público mais amplo e diversificado; (3) avaliar e analisar os resultados, procurando verificar quais foram as consequências das mudanças e se as estratégias de ação utilizadas são adequadas para o ensino de bioquímica. Sempre enfocando o estabelecimento do Aprendizado Colaborativo, foram analisados neste trabalho: (1) a avaliação do curso e as críticas de alunos e monitores; (2) o nível da Distância Transacional do curso, que relaciona a rigidez/flexibilidade da estrutura com a forma de interação/diálogo estabelecida; (3) a percepção da Presença Social pelos alunos na interação estabelecida nas ferramentas de comunicação, e a sua relação com a satisfação gerada; (4) a ocorrência da construção de conhecimento no curso; (5) a importância do papel dos monitores em cursos a distância. Conclui-se da triangulação das análises quantitativas e qualitativas desenvolvidas durante este trabalho que o oferecimento de ferramentas de comunicação para o desenvolvimento de cursos a distância, o uso adequado dessas e outras tecnologias educacionais para promover interação e discussões produtivas, e, principalmente, a maneira como os monitores/professores interagem com os alunos são os alicerces para o estabelecimento da construção do conhecimento pelo Aprendizado Colaborativo / Abstract: The Biochemistry of Nutrition distance education course was designed and implemented based on data collected in a survey concerning the target public interests. Students from different undergraduate courses of Universidade de São Paulo (USP) and Universidade Estadual de Campinas (Unicamp) (both brazilian universities), that had already taken Biochemistry classes were enroled in this course. From the survey results, we could realize that not only those students, but people from all over the country were also interested in this kind of biochemistry course. Concerning this observation, we proposed to re-design the Biochemistry of Nutrition distance education course to assist a wider and diversified public. Since this is a new iniciative, it was necessary to analyze the use of new information and technology communication tools in education and to evaluate the teaching-learning process aiming the determination of distance education courses efficience. In this research we proposed: (1) to design the Biochemistry of Nutrition distance education course base don evaluation results; (2) assist a wider and diversified public; (3) evaluate and analyze the results to verify if the changes were efficient and if the strategies were adequated to biochemical education. Always focusing the Collaborative Learning process, we analyzed: (1) students¿ course evaluation; (2) Transacional Distance related to course design flexibility and course participants¿ interaction; (3) students¿ Social Presence perception in the course communication tools, and the students¿ satisfaction; (4) occurrence of knowledge construction; (5) teaching assistants¿ role and their importance to distance education courses. Triangulation of the qualitative and quantitative data analysis led us to conclude that the disponibility of communication tools to develop distance education courses, the adequate use of educational technology to promote interaction and worthy discussion, and above all, the valuable interaction among students and teaching assistants are the main basis to promote knowledge construction through Collaborative Learning / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular