Growth hormone (GH) is a poly-peptide hormone produced by the anterior pituitary. Growth hormone not only stimulates body and muscle growth but also inhibits adipose tissue growth. The overall objective of this study was to determine the mechanisms by which GH inhibits adipose tissue growth. Three studies were conducted to achieve this objective. The first study was conducted to determine if GH inhibits fat tissue growth by stimulating lipolysis. In this study, adipose tissue weight and adipocyte size were compared between GH-deficient growth hormone releasing hormone receptor (Ghrhr) homozygous mutant mice (i.e., lit/lit mice), lit/+ mice, and lit/lit mice injected with GH. lit/lit mice had less body weight but more subcutaneous fat and larger adipocytes compared to lit/+ mice at the same ages. GH treatment to lit/lit mice for four weeks partially reversed these differences. These data suggest that GH inhibits adipose tissue growth in mice at least in part by stimulating lipolysis. Additional data from this study suggest that GH indirectly stimulates lipolysis in vivo and this indirect mechanism is independent of " adrenergic receptors in the adipose tissue. The second study was conducted to investigate if GH inhibits fat tissue growth also by inhibiting adipogenesis. In this study, stromal vascular fraction (SVF) cells were isolated from subcutaneous fat of lit/+ and lit/lit mice and were induced to differentiate into adipocytes in vitro. Oil Red O staining and gene expression analysis revealed that the SVF cells from lit/lit mice had greater adipogenic potential than from lit/+ mice. This suggests that GH inhibits adipose tissue growth also through inhibition of adipogenesis. Additional data from this study suggest that GH may inhibit adipogenesis by inhibiting the formation of adipogenic precursor cells in adipose tissue in mice. The third study was conducted to determine the role of the central component of GH receptor signaling, STAT5, in GH inhibition of differentiation of bovine preadipocytes. In this study, preadipocytes were isolated from subcutaneous fat of adult cattle and were induced to differentiate with or without GH. Based on Oil Red O staining, gene expression, glycerol-3-phosphate dehydrogenase (G3PDH) activity and acetate incorporation assays, GH inhibited differentiation of bovine preadipocytes into adipocytes. GH induced phosphorylation of STAT5 in differentiating bovine preadipocytes. Overexpression of constitutively active STAT5 through adenovirus mimicked the effect of GH on differentiation of bovine preadipocytes. These data support a role of STAT5 in mediating the inhibitory effect of GH on differentiation of bovine preadipocytes into adipocytes. Overall, GH inhibits adipose tissue by both stimulating lipolysis and inhibiting adipogenesis; GH stimulates lipolysis through an indirect mechanism that is independent of the " adrenergic receptors; GH inhibits adipogenesis through a direct mechanism that may involve the transcription factor STAT5. / Ph. D.

In consideration of the rising prevalence of obesity and its effect on metabolic health and disease, this study was conducted to examine mechanisms involved in adipose tissue function following an acute bout of exercise in abdominal subcutaneous adipose tissue. Sedentary, overweight/obese women (n=10, BMI=30.6±6.0 kg∙m-2, VO2peak=30.3±5.4 mL•kg-1•min-1) completed 2 visits to the lab in which they either exercised for 1 hour or a rested in bed for the equivalent time (control). Experiments were executed randomly using a randomized cross-over study design. Gas exchange measures were measured at three time points before biopsies and subcutaneous adipose biopsies were obtained pre-condition, immediately after condition (0hr), two hours post (2hr), and four hours post (4hr). Acute exercise had significant effects whole body fat oxidation and phosphorylation of insulin signalling proteins, but had no effect on the phosphorylation of proteins regulating the expression of glyceroneogenic genes. In combination, these results suggest that acute exercise can transiently decrease insulin signalling although the mechanism by which this occurs is unclear. Additionally, acute exercise had no effect on the phosphorylation of proteins that are thought to regulate glyceroneogenic gene expression, suggesting that there are either alternative mechanisms involved or that time since the consumption of a meal is a greater stimulus for the activation/upregulation of glyceroneogenesis. Our findings suggest that acute exercise may acutely alter function of adipose tissue such that it contributes to elevations in whole body fatty acid metabolism, however, whether or not chronic adaptations are induced remains an important area for future study. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2013-09-25 20:39:11.506

The endocannabinoid (EC) system has a role in metabolic homeostasis. The purpose of this study was to determine the effect of ECs and the fatty acids they are derived from on lipid metabolism and mitochondrial function in adipocytes. 3T3-L1 adipocytes on day 8 of differentiation were treated with ECs and fatty acids for 48 hours in the absence or presence of insulin and various inhibitors. Lysates were analyzed via Western immunoblotting, a lipolysis assay and Seahorse XF Analyzer for changes in protein levels, phosphorylation state, lipolysis, and oxygen consumption rate. Results showed that ECs (2-arachidonoyl glycerol) stimulated lipolysis via a novel AMPK-dependent pathway, while fatty acids had varying effects on insulin signaling and mitochondrial function . These data suggest adipose tissue EC receptors may be a suitable target for anti-obesity therapy. Further research is needed to understand how the dietary fatty acid profile may influence synthesis of ECs. / May 2016

CDK4 est une sérine/thréonine kinase qui est largement décrite pour son implication dans le contrôle du cycle cellulaire. Notre laboratoire et d'autres ont montré qu'elle jouait également un rôle majeur dans le contrôle de l'homéostasie du glucose (croissance des cellules β du pancréas et sécrétion d'insuline) et des lipides (adipogenèse). Nous avons montré au cours de cette thèse, par le biais de deux modèles de souris, invalidés pour CDK4 (Cdk4-/- ;cre/cre) ou exprimant un mutant hyperactif de la kinase (Cdk4R24C/R24C), qu'elle est un médiateur important de la voie de l'insuline et régule la lipogenèse et la lipolyse. Les souris Cdk4-/- ;cre/cre ont une diminution significative de la taille des adipocytes et du poids du WAT ou l'inverse est observé sur les souris Cdk4R24C/R24C. CDK4 est activée par l'insuline et va ainsi promouvoir le transport de glucose, la synthèse des lipides de novo et réprimer la lipolyse dans les adipocytes. De plus, nous avons démontré que dans l'adipocyte, cellule non proliférative, CDK4 et son partenaire la cycline D3 sont préférentiellement localisés dans le cytoplasme suggérant un rôle indépendant de leurs fonctions nucléaires. Nous avons identifié deux nouveaux substrats de CDK4 : IRS1 et IRS2. CDK4 phosphoryle IRS1 et IRS2 activant un rétrocontrôle positif permettant le maintien de l'action de l'insuline sur les adipocytes. Nos résultats prouvent un nouveau rôle de CDK4 sur la signalisation de l'insuline et sa fonction dans l'adipocyte. Par conséquent, la modulation de son activité pourrait avoir des conséquences majeures sur le mécanisme de résistance à l'insuline, une complication fréquente dans le développement de pathologies comme le diabète et l'obésité. / CDK4 is a serine/threonine kinase mainly known by its involvement in the control of cell cycle progression. Our laboratory and other laboratories have previously shown a major role for CDK4 in the control of glucose homeostasis (pancreatic β-cell growth) and lipid homeostasis (adipogenesis). In this thesis, we showed that CDK4 is an insulin effector that controls lipogenesis and lipolysis in mature adipocytes. We used Cdk4-/- ;cre/cre mice and Cdk4R24C/R24C mice, carrying a hyperactive mutant Cdk4 allele, for this study. Cdk4-/ - ;cre/cre mice have a manifest adipose tissue phenotype with a significant decrease in body weight and WAT mass. On the other hand, Cdk4R24C/R24C mice show increased body weight and increased adiposity. Furthermore, we demonstrate that CDK4 is activated by insulin to promote glucose transport, lipogenesis and repress lipolysis in adipocytes. Interestingly, we showed that in mature quiescent adipocytes CDK4 and its partner, Cyclin D3, are preferentially localized in the cytoplasm, suggesting a role independent from their nuclear functions. We identified two novel substrates of CDK4: IRS1 and IRS2. CDK4 phosphorylates both IRS1 and IRS2 in order to sustain insulin signaling in adipocytes via a positive feed-back loop. To sum up, our results identify a new function of CDK4 on insulin signaling in adipocyte metabolism. Thus, the modulation of its activity could have consequences on insulin resistance, a common complication of obesity and diabetes.

<p>Zadatak ove doktorske disertacije bio je da se utvrdi tok i intenzitet lipolitičkih i oksidativnih promena u tradicionalnoj fermentisanoj kobasici (<em>Petrovačka kobasica</em>) tokom procesa razvoja tehnologije i standardizacije bezbednosti i kvaliteta ovog proizvoda, u cilju dobijanja bezbednog proizvoda, standardnog, vrhunskog kvaliteta, koji bi se kontinuirano mogao proizvoditi i plasirati, na na&scaron;e i trži&scaron;te Evropske Unije.<br />U cilju realizacije postavljenog zadatka tokom tri proizvodne sezone izrađeno je trinaest modela<em> Petrovačke kobasice</em> kako bi se ispitao uticaj vi&scaron;e varijabilnih faktora (proizvodna sezona, vreme otko&scaron;tavanja, način pripreme nadeva, vrsta omotača, su&scaron;enje i zrenje u tradicionalnim i kontrolisanim uslovima, dodatak starter kulture, način pakovanja i dužina skladi&scaron;tenja) na kvantitativne promene na lipidima, kao i na tok i intenzitet lipolitičkih i oksidativnih promena, te posledično i na profil mirisa i ukusa, kao važne karakteristike senzornog kvaliteta. Kvantitativne promene na lipidima tokom procesa proizvodnje <em>Petrovačke kobasice</em> utvrđene su određivanjem vi&scaron;e parametara, kao &scaron;to su sadržaj ukupnih lipida, masnokiselinski sastav i sadržaj ukupnog holesterola. Lipolitičke promene tokom procesa dimljenja, fermentacije, su&scaron;enja, zrenja i skladi&scaron;tenja praćene su određivanjem sadržaja slobodnih masnih kiselina, dok su oksidativne promene kvantifikovane preko sadržaja sekundarnih produkata<br />oksidacije lipida, malondialdehida i zasićenih alifatičnih aldehida. Na osnovu prikazanih rezultata može se zaključiti da u kobasicama izrađenim od ohlađenog mesa u uslovima su&scaron;enja i zrenja na nižim temperaturama (prosečna temperatura oko 10 ⁰C), koje<br />prati i sporiji pad vrednosti pH (60. dan pH&ge;5,3) dolazi do manjih lipolitičkih i oksidativnih promena na lipidima (kobasice B1 i B2 grupe). Ovaj model tradicionalne proizvodnje dovodi i do neznatnih oksidativnih promena i očuvanja poželjnih senzornih<br />svojstava mirisa i ukusa tokom dužeg vremena skladi&scaron;tenja (9 meseci od dana proizvodnje), te se može smatrati optimalnim modelom koji se mora preneti i u kontrolisane uslove proizvodnje. Takođe, zaključeno je da pakovanje u vakuumu i u modifikovanoj atmosferi, te upotreba komercijalne starter kulture, dovodi do smanjenja<br />intenziteta oksidativnih promena na lipidima, tokom skladi&scaron;tenja, odnosno celokupnog procesa proizvodnje<em> Petrovačke kobasice</em>. Dovodeći u vezu nastale produkte oksidacije<br />lipida sa senzornim profilom mirisa i ukusa može se zaključiti da vrednosti malondialdehida do 1,3 mg/kg ne utiču na značajnije naru&scaron;avanje senzornih svojstava<br />mirisa i ukusa <em>Petrovačke kobasice</em>.</p> / <p>The aim of this PhD thesis was to determine the course and intensity of the lipolytic and oxidative changes in traditional fermented sausage (Petrovac sausage) throughout the process of technology development, as well as the standardization of safety and quality of this product in order to obtain safe product of standard, superior quality, which could be continuously produced and placed on the market of our country as well as the market of European Union.</p><p>In order to realize the aim, during three seasons of production thirteen models of Petrovac sausage were produced with the aim to investigate multiple variable factors (season of production, time of deboning, filling preparation method, type of casings, drying and ripening in traditional and controled conditions, starter culture addition, packaging and storage period) on lipid quality changes, as well as on the course and intensity of lipolytic and oxidative changes and, consequently, the odor and flavor profile as important characteristics of sensory quality.</p><p>Quality changes on lipids during production of Petrovac sausage were determined using multiple parameters, such as the content of total lipids, fatty acids composition and content of total cholesterol. The lipolytic changes throughout the process of smoking, fermentation, drying, ripening and storage were monitored through the content of free fatty acids, while the oxidative changes were quantified based on the content of secondary products of lipid peroxidation, malondialdehyde and saturated aliphatic aldehydes. Based on the presented results it could be concluded that in the sausages made of cooled meat in the conditions of drying and ripening in lower temperatures (average temperature about 10 0C), which are followed by the slower drop of pH values (60. day pH &ge;5.3) comes to a lesser lipolytic and oxidative changes in lipids (sausages of B1 and B2 groups). This model of production results in<br />slight oxidative changes and the preservation of favourable sensory properties of odor and flavor during longer storage period (9 months since the date of production), so it could be considered as the optimal model, that should also be applied in the controled conditions of production.</p><p>It was also concluded that vacuum packaging and modified atmosphere packaging, as well as the usage of starter culture results in the decrease of intensity of oxidative changes on lipids throughout the entire production process of Petrovac sausage. Correlating the created products of lipid peroxidation with the sensory profile of odor and flavor, it could be concluded that the content of malondialdehyde up to 1.3<br />mg/kg has no significant effect on the deterioration of sensory properties of odor and flavor of Petrovac sausage.</p>

<p>Insulin as well as glucagon are important hormones in maintaining glucose homeostasis and regulating the metabolism in the body. Insulin receptors (IR) are transmembrane receptors that promote a signal transduction when activated by insulin. This can for example cause an increased influx of glucose into the cell performed by so called glucose transporters (GLUTs). These membrane proteins facilitate the transport of glucose from the blood into the cells, so the cell always has a constant supply of energy. Peroxisome proliferator-activated receptors (PPAR) are nuclear fatty acid receptors. They are activated by lipids and regulate fatty acid transcription. PPARδ/β is located in skeletal muscle and can promote fatty acid catabolism as well as cause a switch in fuel preference from glucose to fatty acids. It has been suggested that ligands for PPARδ could act as insulin sensitizers. The PPARγ coactivator-1α can increase mitochondrial content in skeletal muscle if over expressed. The same is true for endurance exercise.</p><p>Hormones released from adipose tissue can cause hyperphagia<strong> </strong>and obesity if over- or under expressed. They can also work in the opposite way by decreasing appetite with weight loss as an effect. Impaired signalling or dysfunctional receptor can cause insulin resistance, obesity and diabetes. Lipolysis occurs in adipose tissues and is conducted by three enzymes, namely adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL). There are some factors that can increase lipolysis such as caffeine, a low glycemic index, high protein intake and training.</p><p>The enzyme PEPCK is involved in the gluconeogensis in the liver and kidney cortex, and also in the glyceroneogenesis in the liver, as well as in brown and white adipose tissue. When overexpressed in skeletal muscle the enzyme increases the muscle activity. The overexpression of the enzyme did promote the β-oxidation as energy source for the muscles during exercise, instead of muscle glycogen as fuel.</p><p>The processes of protein synthesis and breakdown are together called protein turnover. Muscle grows when synthesis is greater than breakdown, and withers if breakdown exceeds the level of synthesis. Acute effects of training is catabolic, but long time exercise causes however an increased protein synthesis. Leucine, an essential amino acid, has an important role in the initiation phase of translation. Glutamine is probably important in the regulation of muscle protein synthesis and breakdown. Together with glutamate, aspartate and asparagine, these are responsible for the amino acid metabolism that occurs in the muscles. Protein synthesis reaches its maximum in the recovery phase after intense training.</p>

Insulin as well as glucagon are important hormones in maintaining glucose homeostasis and regulating the metabolism in the body. Insulin receptors (IR) are transmembrane receptors that promote a signal transduction when activated by insulin. This can for example cause an increased influx of glucose into the cell performed by so called glucose transporters (GLUTs). These membrane proteins facilitate the transport of glucose from the blood into the cells, so the cell always has a constant supply of energy. Peroxisome proliferator-activated receptors (PPAR) are nuclear fatty acid receptors. They are activated by lipids and regulate fatty acid transcription. PPARδ/β is located in skeletal muscle and can promote fatty acid catabolism as well as cause a switch in fuel preference from glucose to fatty acids. It has been suggested that ligands for PPARδ could act as insulin sensitizers. The PPARγ coactivator-1α can increase mitochondrial content in skeletal muscle if over expressed. The same is true for endurance exercise. Hormones released from adipose tissue can cause hyperphagia and obesity if over- or under expressed. They can also work in the opposite way by decreasing appetite with weight loss as an effect. Impaired signalling or dysfunctional receptor can cause insulin resistance, obesity and diabetes. Lipolysis occurs in adipose tissues and is conducted by three enzymes, namely adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL). There are some factors that can increase lipolysis such as caffeine, a low glycemic index, high protein intake and training. The enzyme PEPCK is involved in the gluconeogensis in the liver and kidney cortex, and also in the glyceroneogenesis in the liver, as well as in brown and white adipose tissue. When overexpressed in skeletal muscle the enzyme increases the muscle activity. The overexpression of the enzyme did promote the β-oxidation as energy source for the muscles during exercise, instead of muscle glycogen as fuel. The processes of protein synthesis and breakdown are together called protein turnover. Muscle grows when synthesis is greater than breakdown, and withers if breakdown exceeds the level of synthesis. Acute effects of training is catabolic, but long time exercise causes however an increased protein synthesis. Leucine, an essential amino acid, has an important role in the initiation phase of translation. Glutamine is probably important in the regulation of muscle protein synthesis and breakdown. Together with glutamate, aspartate and asparagine, these are responsible for the amino acid metabolism that occurs in the muscles. Protein synthesis reaches its maximum in the recovery phase after intense training.

Temperature dependent optical properties of lipid tissue verify critical information of tissue dynamics which can be applied to tissue treatment and diagnosis of various pathological features. Current methods of treating lipid rich tissues via heating are associated with post operation complications. Recent studies shows potential of lipid rich tissue removal by cooling. For monitoring cooling procedure and physical and chemical changes in lipid tissue, temperature dependent optical properties in subzero cooling need to be verified. This study designed heat transfer system estimating heat flux by cooling and programmed codes for image and data processing to obtain refractive indices of rodent subcutaneous lipid tissue. Phase transition of lipid tissue was observed and finally verified temperature dependent refractive index coefficient of lipid tissue from 24°C to -10°C. / text

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences