INTRODUÇÃO: A leishmaniose visceral (LV), pertence ao grupo de endemias consideradas prioritárias no mundo. É uma doença grave e com poucas opções de tratamento e, mesmo quando adequadamente tratada, possui um nível de letalidade de 5 a 7%. Apesar da expansão da doença, o tratamento para leishmaniose visceral não obteve avanços. O tratamento da leishmaniose possui apenas dois grupos de medicamentos utilizados: os antimonoiais e os não-antimoniais. Os compostos nitroheterocíclicos foram utilizados pois acredita-se que a eficácia desta classe de compostos está na habilidade desses compostos inibirem a tripanotiona redutase. Os compostos foram obtidos por via sintética e refinados pelo método QSAR por remodelagem molecular. Foram obtidos séries de compostos nitroheterocíclicos, onde a série BSF (derivados 5-nitro-2-furfurilideno - azometínicos) foi utilizada para avaliar a bioatividade in vitro destes compostos frente à Leishmania. Para avaliação da atividade anti-Leishmania foram usadas formas promastigotas de Leishmania (Leishmania) infantum. Os métodos utilizados para determinar a atividade anti-Leishmania dos compostos da série BSF foram os métodos colorimétrico 3-[4,5-dimetiltiazol-2-il] 2,5 brometo de difeniltetrazólio (MTT), apoptose por Anexina V e reação de Griess (dosagem de NO). Ao comparar os resultados com os respectivos controles positivos e com a Anfotericina B, foi observado que a atividade anti-Leishmania em formas promastigotas de L. L. infantum dos compostos foi menos significativa quando comparado com anfotericina B. Porém, ao comparar os resultados de macrófagos infectados e citotoxicidade com a anfotericina B, os compostos mostraram resultados expressivos, ao apresentarem baixa taxa de citotoxicidade e significativa diminuição da proliferação intracelular. A expressiva produção de nitrito pelos macrófagos infectados tratados com os compostos da série BSF sugere-se que estes compostos possuam uma ação indireta de potencialização de produção de NO nas células hospedeiras. Os resultados in vitro utilizando derivados nitroheterocíclicos mostraram atividade destes sobre formas promastigotas e amastigotas intracelulares, e são compostos em potencial para avaliação de efeito in vivo contra leishmaniose visceral / INTRODUCTION: Visceral leishmaniasis (VL) belongs to the group of endemics prioritized worldwide. It is a serious disease with few treatment options, and even when adequately treated, it has a lethality level of 5 to 7%. Despite the expansion of the disease, treatment for visceral leishmaniasis has not made progress. Treatment of leishmaniasis has used only two groups of drugs: antimonial and non-antimonial. Nitro-heterocyclic compounds were used in this study because it is believed that the effectiveness of this class of compounds is the ability to inhibit trypanothione reductase. The compounds were obtained synthetically and refined by QSAR method molecular remodeling. Nitro-heterocyclic series of compounds were obtained, where the BSF series (derived from 5-nitro-2-furfurylidene - azometínicos) was used to evaluate the in vitro bioactivity of these compounds against the Leishmania. To evaluate the anti-Leishmania activity, promastigotes of Leishmania (Leishmania) infantum were used. The methods used to determine the anti-Leishmania activity of the BSF series compounds were colorimetric methods 3-[4,5-dimethylthiazol-2-yl] 2,5-diphenyltetrazolium bromide (MTT), apoptosis by Annexin V, and Griess reaction (IN dosage). By comparing the results with the respective positive controls and with amphotericin B, it was observed that the anti-Leishmania activity of L. L. infantum promastigotes of the compounds was less significant when compared with amphotericin B. However, comparing the results of infected macrophages and cytotoxicity with amphotericin B, compounds showed significant results, presenting low cytotoxicity rate and significant decrease in intracellular proliferation. The significant nitrite production by infected macrophages treated with the BSF series compounds suggested that these compounds have an indirect potentiation action in the NO production in the host cells. In vitro results using nitro-heterocyclic derivatives showed their activity on these promastigotes and intracellular amastigotes, and presented them as potential compounds for in vivo effect evaluation against visceral leishmaniasis

La membrane plasmique est un assemblage supramoléculaire qui délimite la cellule. C’est une structure fine, complexe et dynamique assurant des fonctions multiples et vitales pour la cellule. Sa rupture est un évènement physiologique pour les cellules soumises à des stress mécaniques fréquents et/ou importants, comme les cellules épithéliales, les cellules endothéliales ou les cellules musculaires. Dans des conditions physiopathologiques, la membrane plasmique peut également être endommagée par l’insertion de toxines bactériennes formant des pores (PFTs, pour « pore forming toxins »). Le processus de réparation membranaire et la machinerie protéique associée sont encore mal connus. Connaître les partenaires protéiques et comprendre les mécanismes mis en jeu durant le processus de réparation de la membrane plasmique sont deux enjeux fondamentaux majeurs. En effet, il a été établi qu’une défaillance du processus de réparation membranaire pour les fibres musculaires est la cause principale de certaines dystrophies musculaires. La machinerie protéique de réparation comprend des protéines comme la dysferline, la cavéoline-3 et certaines Annexines (Anx). Les Anx appartiennent à une superfamille de protéines répandue chez la plupart des eucaryotes, qui ont la propriété commune de se lier aux membranes biologiques en présence de calcium (Ca2+). Certaines Anx, comme l’AnxA5, une fois liées aux membranes biologiques s’auto-assemblent spontanément en réseau-2D. Lors de ce travail de thèse, nous avons étudié le rôle de l’AnxA5 dans la réparation membranaire des trophoblastes placentaires et des cellules du muscle squelettique humain. Pour les deux types cellulaires, nous avons montré que l’AnxA5 est un acteur indispensable du processus de réparation membranaire dans le cas de ruptures mécaniques. En associant des approches de microscopie de fluorescence et de microscopie électronique à transmission (MET), nous avons mis en évidence que dans ces cellules, le mécanisme de réparation est principalement basé sur la formation d’un « patch » lipidique. Dans les cellules musculaires, les expériences de MET ont mis en évidence qu’un pool d’AnxA5 endogène se lie aux bords du site de rupture quelques secondes après la lésion du sarcolemme. Ceci suggère qu’après rupture de la membrane plasmique, l’augmentation locale de la concentration calcique intracellulaire provoque la liaison de l’AnxA5 spécifiquement aux bords de la région membranaire lésée où elle forme un réseau-2D. Le réseau-2D stabiliserait localement la membrane et préviendrait sa déchirure, induite par les forces de tensions exercées par le cytosquelette cortical. Nous avons également montré que l’AnxA5 ne semble pas impliquée dans la réparation de la membrane plasmique après insertion de PFTs. Ceci suggère que différents mécanismes de réparation existent et que leur mise en place dépend probablement du type ou de l’importance des dommages. Finalement nous avons étendu notre étude à des lignées cellulaires établies à partir de patients diagnostiqués comme souffrant de dystrophies des ceintures de type 2B (déficience en dysferline) et 1C (déficience en cavéoline-3), respectivement. Nous avons montré, pour ces lignées, que la déficience en dysferline ou cavéoline-3 provoque un défaut de réparation dans le cas des ruptures mécaniques de la membrane plasmique. Dans ces cellules musculaires pathologiques intactes ou endommagées, l’AnxA5 a le même comportement, ce qui suggère que l’action de l’AnxA5 est indépendante de ces protéines. A la différence des cellules déficientes en dysferline, nous avons observé que les cellules déficientes en cavéoline-3 sont capables de réparer efficacement des lésions créées par l’insertion de PFTs dans le sarcolemme. Ce résultat supporte l’hypothèse de l’existence de plusieurs mécanismes de réparation. En conclusion, ce travail montre que l’AnxA5 est un composant clé de la machinerie de réparation dans le cas des ruptures mécaniques. / Plasma membrane is the supramolecular assembly that delimits the cell. It is a thin, dynamic and complex structure, ensuring multiple and vital cell functions. Its disruption is a physiological event occurring in cells submitted to frequent mechanical stresses, such as endothelial cells, epithelial cells and muscle cells. It is also a physiological event for cells exposed to pore forming bacterial toxins (PFTs). Membrane repair mechanisms and associated protein machinery are still poorly understood. This knowledge is, however, essential for obvious physiopathological issues. Indeed, a defect of membrane repair in muscle cells leads to some muscular dystrophies. Membrane repair machinery includes proteins such as dysferlin, MG-53, caveolin-3 and some Annexins (Anx). Anx belong to a superfamily of proteins widely spread in most of eukaryotes, which share the property of binding to biological membranes in the presence of calcium (Ca2+). Here, we investigated the role of AnxA5 in cell membrane repair of human trophoblastic and skeletal muscle cells. We showed that AnxA5 is required for membrane repair of mechanical damages in the two cell types. By combining fluorescence and transmission electron microscopy approaches, we evidenced that membrane repair mechanism in these cells is based on the formation of a lipid “patch”. In human muscle cells, TEM experiments revealed that a pool of endogenous AnxA5 binds to the edges of the torn sarcolemma as soon as a few seconds after membrane disruption. Our results suggest the following mechanism: triggered by the local increase in Ca2+ concentration, AnxA5 molecules bind to PS exposed at the edges of the torn membrane, where they self-assemble into 2D arrays. The formation of 2D arrays strengthens the damaged sarcolemma, counteracts the tensions exerted by the cortical cytoskeleton and thus prevents the expansion of the tear. We showed also that a pool of endogenous AnxA5 binds to intracellular vesicles that obstruct the wounding site. It is likely these vesicles, once associated one to each other, ensure membrane resealing. Our results suggest that sarcolemma repair of damages caused by PFTs is independent of AnxA5. Therefore, different membrane repair mechanisms may exist, their occurrence probably depending on the type and/or the size of damages. Finally, we performed studies on muscle cells established from patients diagnosed with limb girdle muscular dystrophies type 2B (dysferlin-deficient) and 1C (caveolin-3-deficient), respectively. We found that dysferlin or caveolin-3 deficiency leads to a defect of membrane repair, in the case of mechanical damages. AnxA5 behaved similarly in these damaged cells and wild-type cells, suggesting that its function is independent of dysferlin or caveolin-3. Unlike dysferlin-deficient cells, damages created by PFTs are efficiently repaired in caveolin- 3-deficient cells. This result supports the hypothesis that different mechanisms occur in muscle cells, depending on the type of damage. In conclusion, this work indicates that AnxA5 is a key component of the membrane repair machinery, in the case of mechanical disruptions. Our results enable to propose a detailed mode of action for AnxA5.

INTRODUÇÃO: A leishmaniose visceral (LV), pertence ao grupo de endemias consideradas prioritárias no mundo. É uma doença grave e com poucas opções de tratamento e, mesmo quando adequadamente tratada, possui um nível de letalidade de 5 a 7%. Apesar da expansão da doença, o tratamento para leishmaniose visceral não obteve avanços. O tratamento da leishmaniose possui apenas dois grupos de medicamentos utilizados: os antimonoiais e os não-antimoniais. Os compostos nitroheterocíclicos foram utilizados pois acredita-se que a eficácia desta classe de compostos está na habilidade desses compostos inibirem a tripanotiona redutase. Os compostos foram obtidos por via sintética e refinados pelo método QSAR por remodelagem molecular. Foram obtidos séries de compostos nitroheterocíclicos, onde a série BSF (derivados 5-nitro-2-furfurilideno - azometínicos) foi utilizada para avaliar a bioatividade in vitro destes compostos frente à Leishmania. Para avaliação da atividade anti-Leishmania foram usadas formas promastigotas de Leishmania (Leishmania) infantum. Os métodos utilizados para determinar a atividade anti-Leishmania dos compostos da série BSF foram os métodos colorimétrico 3-[4,5-dimetiltiazol-2-il] 2,5 brometo de difeniltetrazólio (MTT), apoptose por Anexina V e reação de Griess (dosagem de NO). Ao comparar os resultados com os respectivos controles positivos e com a Anfotericina B, foi observado que a atividade anti-Leishmania em formas promastigotas de L. L. infantum dos compostos foi menos significativa quando comparado com anfotericina B. Porém, ao comparar os resultados de macrófagos infectados e citotoxicidade com a anfotericina B, os compostos mostraram resultados expressivos, ao apresentarem baixa taxa de citotoxicidade e significativa diminuição da proliferação intracelular. A expressiva produção de nitrito pelos macrófagos infectados tratados com os compostos da série BSF sugere-se que estes compostos possuam uma ação indireta de potencialização de produção de NO nas células hospedeiras. Os resultados in vitro utilizando derivados nitroheterocíclicos mostraram atividade destes sobre formas promastigotas e amastigotas intracelulares, e são compostos em potencial para avaliação de efeito in vivo contra leishmaniose visceral / INTRODUCTION: Visceral leishmaniasis (VL) belongs to the group of endemics prioritized worldwide. It is a serious disease with few treatment options, and even when adequately treated, it has a lethality level of 5 to 7%. Despite the expansion of the disease, treatment for visceral leishmaniasis has not made progress. Treatment of leishmaniasis has used only two groups of drugs: antimonial and non-antimonial. Nitro-heterocyclic compounds were used in this study because it is believed that the effectiveness of this class of compounds is the ability to inhibit trypanothione reductase. The compounds were obtained synthetically and refined by QSAR method molecular remodeling. Nitro-heterocyclic series of compounds were obtained, where the BSF series (derived from 5-nitro-2-furfurylidene - azometínicos) was used to evaluate the in vitro bioactivity of these compounds against the Leishmania. To evaluate the anti-Leishmania activity, promastigotes of Leishmania (Leishmania) infantum were used. The methods used to determine the anti-Leishmania activity of the BSF series compounds were colorimetric methods 3-[4,5-dimethylthiazol-2-yl] 2,5-diphenyltetrazolium bromide (MTT), apoptosis by Annexin V, and Griess reaction (IN dosage). By comparing the results with the respective positive controls and with amphotericin B, it was observed that the anti-Leishmania activity of L. L. infantum promastigotes of the compounds was less significant when compared with amphotericin B. However, comparing the results of infected macrophages and cytotoxicity with amphotericin B, compounds showed significant results, presenting low cytotoxicity rate and significant decrease in intracellular proliferation. The significant nitrite production by infected macrophages treated with the BSF series compounds suggested that these compounds have an indirect potentiation action in the NO production in the host cells. In vitro results using nitro-heterocyclic derivatives showed their activity on these promastigotes and intracellular amastigotes, and presented them as potential compounds for in vivo effect evaluation against visceral leishmaniasis

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Made available in DSpace on 2015-06-17T19:33:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-25. Added 1 bitstream(s) on 2015-06-18T12:48:22Z : No. of bitstreams: 1 000829908_20160901.pdf: 53511 bytes, checksum: c4a534029afcd0c7fbcf17b554cea70b (MD5) Bitstreams deleted on 2016-09-01T14:08:39Z: 000829908_20160901.pdf,. Added 1 bitstream(s) on 2016-09-01T14:09:17Z : No. of bitstreams: 1 000829908.pdf: 1790690 bytes, checksum: 03ab0efe7f9d02d0ac648b9cdd412a18 (MD5) / O laser de baixa potência (LBP) é muito utilizado em diferentes ramos da medicina regenerativa e odontologia, onde é aplicado para melhorar o processo de cura e é benéfico em uma variedade de processos patológicos, no qual pode aumentar a taxa de proliferação de várias linhagens celulares. No entanto, poucos são os trabalhos que avaliaram os efeitos do LBP em células-tronco mesenquimais (CTM) caninas. Desta forma, os objetivos do presente trabalho são: caracterizar as células-tronco mesenquimais do tecido adiposo (CTM-TA) e da medula óssea (CTM-MO) caninas, estudar o efeito do laser de baixa potência fosfeto de índio-gálio-alumínio nas densidades de 1,1 e 8,7 J/cm2 sobre o cultivo das mesmas quanto à proliferação e viabilidade celular, à imunogenicidade por meio da expressão do MHC-II e avaliar o cariótipo das células irradiadas e não irradiadas a fim de comprovar a ausência de alterações cromossômicas com a utilização do LBP. O estudo revelou que o LBP não alterou a viabilidade, proliferação celular, expressão de MHC-II e o cariótipo das amostras analisadas entre os grupos. Desta forma, pode-se concluir que o LBP não causa efeitos biológicos às CTM-TA e CTM-MO caninas nas dosagens utilizadas de 1,1 e 8,7 J/cm2. Portanto, outras dosagens devem ser investigadas para estimular a proliferação das CTM caninas sem causar alterações celulares deletérias / Low power laser (LPL) is widely used in different fields of regenerative medicine and dentistry, where it is used to improve the healing process and is beneficial in a variety of disease processes, which can increase the rate of proliferation of various cell lineages. However, there are few studies evaluating the effects of LPL on canine mesenchymal stem cells (MSC). Thus, the aims of this study are: to characterize canine mesenchymal stem cells derived from adipose tissue (AT-MSC) and bone marrow (BM-MSC), to investigate the effect of low power laser aluminium gallium indium phosphide at densities of 1.1 and 8.7 J/cm2 on cellular viability and proliferation, immunogenicity by MHC-II expression and evaluate the karyotype of the irradiated and non-irradiated cells in order to identify the absence of chromosomal abnormalities with the use of LPL. The study revealed that LPL did not affect cell viability and proliferation, MHC-II expression and karyotype of the samples analyzed between groups. Thus, we can conclude that LPL cause no biological effects to canine AT-MSC and BM-MSC with the 1.1 and 8.7 J/cm2 dosages used. Therefore, other dosages to stimulate proliferation without causing deleterious cellular changes of canine MSC must be investigated

Orientador: Rogério Martins Amorim / Coorientador: Fernanda da Cruz Landim / Banca: Marimélia Porcionatto / Banca: Patrícia Fidelis de Oliveira Gregolini / Banca: Marjorie de Assis Golim / Banca: Regina Kiomi Takahira / Resumo: O laser de baixa potência (LBP) é muito utilizado em diferentes ramos da medicina regenerativa e odontologia, onde é aplicado para melhorar o processo de cura e é benéfico em uma variedade de processos patológicos, no qual pode aumentar a taxa de proliferação de várias linhagens celulares. No entanto, poucos são os trabalhos que avaliaram os efeitos do LBP em células-tronco mesenquimais (CTM) caninas. Desta forma, os objetivos do presente trabalho são: caracterizar as células-tronco mesenquimais do tecido adiposo (CTM-TA) e da medula óssea (CTM-MO) caninas, estudar o efeito do laser de baixa potência fosfeto de índio-gálio-alumínio nas densidades de 1,1 e 8,7 J/cm2 sobre o cultivo das mesmas quanto à proliferação e viabilidade celular, à imunogenicidade por meio da expressão do MHC-II e avaliar o cariótipo das células irradiadas e não irradiadas a fim de comprovar a ausência de alterações cromossômicas com a utilização do LBP. O estudo revelou que o LBP não alterou a viabilidade, proliferação celular, expressão de MHC-II e o cariótipo das amostras analisadas entre os grupos. Desta forma, pode-se concluir que o LBP não causa efeitos biológicos às CTM-TA e CTM-MO caninas nas dosagens utilizadas de 1,1 e 8,7 J/cm2. Portanto, outras dosagens devem ser investigadas para estimular a proliferação das CTM caninas sem causar alterações celulares deletérias / Abstract: Low power laser (LPL) is widely used in different fields of regenerative medicine and dentistry, where it is used to improve the healing process and is beneficial in a variety of disease processes, which can increase the rate of proliferation of various cell lineages. However, there are few studies evaluating the effects of LPL on canine mesenchymal stem cells (MSC). Thus, the aims of this study are: to characterize canine mesenchymal stem cells derived from adipose tissue (AT-MSC) and bone marrow (BM-MSC), to investigate the effect of low power laser aluminium gallium indium phosphide at densities of 1.1 and 8.7 J/cm2 on cellular viability and proliferation, immunogenicity by MHC-II expression and evaluate the karyotype of the irradiated and non-irradiated cells in order to identify the absence of chromosomal abnormalities with the use of LPL. The study revealed that LPL did not affect cell viability and proliferation, MHC-II expression and karyotype of the samples analyzed between groups. Thus, we can conclude that LPL cause no biological effects to canine AT-MSC and BM-MSC with the 1.1 and 8.7 J/cm2 dosages used. Therefore, other dosages to stimulate proliferation without causing deleterious cellular changes of canine MSC must be investigated / Doutor

La macroautofagia y la endocitosis son dos procesos catabólicos conservados evolutivamente en los que, mediante un tráfico vesicular, se degrada el material secuestrado, cuyo origen es intra- y extracelular, respectivamente. Ambos procesos comienzan de manera diferente: mediante la formación de un nuevo orgánulo, el autofagosoma, que secuestra material citoplásmico (macroautofagia), o mediante la internalización de material extracelular y de algunos componentes de la membrana plasmática a través de vesículas endocíticas (endocitosis). Sin embargo, los dos terminan en el mismo compartimiento: el lisosoma. En un análisis proteómico de membranas lisosomales, purificadas a partir de fibroblastos de ratón, identificamos tres proteínas, que se unen a fosfolípidos de una manera dependiente de calcio, y cuyos niveles en la membrana lisosomal aumentaban en ausencia de aminoácidos, una condición que activa la macroautofagia. Basándonos en esos resultados iniciales, y teniendo en cuenta que el calcio es un segundo mensajero muy importante, decidimos: en primer lugar, abordar el papel del calcio en la activación de la autofagia producida por el ayuno de aminoácidos, y, en segundo lugar, investigar el papel de esas tres proteínas en el mecanismo autofágico. Como resultado de estos estudios, describimos en primer lugar una nueva vía de señalización dependiente de calcio que activa la formación de autofagosomas por los aminoácidos. Concretamente, hemos encontrado que el ayuno de aminoácidos esenciales produce un aumento en el calcio citosólico, procedente tanto del medio extracelular como de almacenes intracelulares. Como consecuencia de esto, la calmodulina quinasa quinasa- ß activa a AMPK y a mTORC1. En la última etapa de esta vía, ULK1, una quinasa responsable de la iniciación de la autofagia, se activa para contribuir a la formación de los autofagosomas. Las tres proteínas identificadas en el estudio proteómico y cuyos niveles en las membranas lisosomales aumentan en ausencia de aminoácidos son la anexina A1, la anexina A5 y la copina 1. Empleando métodos bioquímicos y de inmunofluorescencia observamos que el ayuno de aminoácidos causa la translocación de la anexina A5 desde el complejo de Golgi hasta las membranas lisosomales, donde también se acumulan la anexina A1 y la copina 1. Asimismo, demostramos por sobre-expresión y silenciamiento de esas tres proteínas, que las tres inducen la fusión de autofagosomas con lisosomas y que la copina 1, y en menor medida la anexina A1, aumentan el efecto individual de la anexina A5. Finalmente, la anexina A5 inhibe la endocitosis mientras que copina 1 la induce. En resumen, nuestros resultados ponen de manifiesto que la activación de la formación de autofagosomas por el ayuno de aminoácidos es debida, al menos en parte, a una vía de señalización dependiente de Ca2+ y que esta condición también conlleva la aceleración de la maduración de los autofagosomas a autolisosomas a través de proteínas que unen el Ca2+ como las anexinas A1 y A5 y la copina 1. / Ghislat Cherfaoui, G. (2013). Regulation of Lysosomal Degradation by CA2+And CA2+-Binding Proteins [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/29690 / TESIS

The effects of stimulation of the A5 cell group of the caudal ventrolateral pons electrically or with L-glutamate on heart rate and blood pressure were determined in rabbits. Electrical stimulation caused blood pressure increases and reflex bradycardia. L-glutamate caused decreases in blood pressure and heart rate which were blocked by the L-glutamate antagonist aminophosphoheptanoic acid. Transection of the brainstem at the level of the midbrain did not alter the effects of either electrical or chemical stimulation. Lesions of the nucleus and tractus solitarius (NTS) attenuated the effects of L-glutamate, but did not change the effectiveness electrical stimulation. Injections of 6-hydroxydopamine three to four weeks before the experiments blocked the effects of electrical stimulation but only reduced the effects of L-glutamate injection. The A5 group may have two functional subdivisions. Some A5 cells may produce blood pressure depressor and bradycardiac effects by means of projections to the NTS and the spinal cord. Other A5 cells may produce blood pressure presser effects by means of projections to the spinal cord.

Indiana University-Purdue University Indianapolis (IUPUI) / The incidence of Metabolic Syndrome (MetS) is increasing worldwide and accompanied by elevated risks for cardiovascular disease (CVD) and other subsequent comorbidities. MetS is associated with increased circulating triglycerides. A key enzyme involved in triglyceride (TG) clearance is lipoprotein lipase (LPL) whose activity is modulated by a variety of factors. Recent literature has identified the importance of angiopoietin-like proteins (ANGPTL) as regulators of LPL activity and has hypothesized a model in which three of these proteins interact with LPL to regulate the partitioning of TG metabolism from adipose to skeletal muscle. The work detailed in this dissertation adds to the model of ANGPTL regulation of LPL by establishing how ANGPTL8 modulates the ability of ANGPTL3 and ANGPTL4 to inhibit LPL activity in the bloodstream and localized environments, respectively. In the updated model, elevated insulin concentrations result in increased hepatic ANGPTL3/8 secretion and increased ANGPTL4/8 in adipose tissue. ANGPTL3/8 works as an endocrine molecule to inhibit skeletal muscle LPL from hydrolyzing circulating TG. Simultaneously, ANGPTL4/8 works in a paracrine mechanism to bind LPL on the endothelial vasculature adjacent to adipose tissue to alleviate ANGPTL4-mediated LPL inhibition and also prevent ANGPTL3/8 inhibition of localized LPL. Thus, in the postprandial state free fatty acids (FFA) from the hydrolysis of TG are directed into adipocytes for storage. Under fasting conditions, ANGPTL8 production is decreased in adipocytes and hepatocytes. This decreased production results in diminished ANGPTL4/8 and ANGPTL3/8 secretion from their respective tissues. As a result, ANGPTL4 inhibits adipocyte localized LPL activity while ANGPTL3 at physiological concentrations has minimal effect on LPL activity. Furthermore, any ANGPTL3/8 which is produced has its LPL-inhibitory ability diminished by the circulating apolipoprotein ApoA5. LPL is more active in skeletal muscle compared to adipose tissue where energy is shunted towards utilization in the muscle and away from storage in adipose tissue. A complete understanding of LPL regulation by ANGPTL proteins can potentially provide therapeutics targets for MetS.