Ellen Lai Ping Chan. / Thesis (Ph.D)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 238-272. / Chapter CHAPTER I --- LITERATURE REVIEW / Chapter 1. --- History --- p.1 / Chapter 2. --- Species Distribution of BAT --- p.3 / Chapter 3. --- Distribution of BAT --- p.4 / Chapter 4. --- Structure of BAT --- p.4 / Chapter 4.1. --- Macroscopic Appearance --- p.4 / Chapter 4.1.1. --- Innervation --- p.4 / Chapter 4.1.2. --- Blood supply --- p.5 / Chapter 4.2. --- Microscopic Structure of BAT --- p.6 / Chapter 4.3. --- Difference Between Brown Fat and White Fat --- p.9 / Chapter 5. --- Composition of BAT --- p.11 / Chapter 6. --- The Mechanisms of Brown Adipose Tissue Thermogenesis --- p.12 / Chapter 6.1. --- Factors Influencing Proton Transport by UCP --- p.16 / Chapter 6.2. --- Postulated Sequence of Events during Thermogenesis --- p.18 / Chapter 7. --- Measurements of thermogenic Capacity of BAT --- p.21 / Chapter 8. --- Age-related Differences in BAT --- p.28 / Chapter 9. --- Non-shivering Thermogenesis and BAT --- p.32 / Chapter 9.1. --- Changes In BAT During Cold Acclimation --- p.35 / Chapter 9.1.1. --- GDP Binding --- p.35 / Chapter 9.1.2. --- Concentration of UCP --- p.37 / Chapter 9.1.3. --- Metabolic changes in BAT during Cold Acclimation --- p.39 / Chapter 10. --- Diet-induced Thermogenesis and BAT --- p.41 / Chapter 10.1. --- Mechanism of DIT --- p.42 / Chapter 10.2. --- Controversies in DIT --- p.44 / Chapter 10.3. --- Nutritional Factors Inducing DIT --- p.46 / Chapter 10.4. --- DIT in Man --- p.47 / Chapter 10.5. --- Neuroendocrine Control of BAT in DIT --- p.48 / Chapter 10.6. --- Effects of Fasting in BAT --- p.51 / Chapter 11. --- Obesity and BAT --- p.53 / Chapter 11.1. --- NST and DIT in Obese Animals --- p.58 / Chapter 11.2. --- Regulation of BAT in Obese Animals --- p.59 / Chapter 11.2.1. --- Sympathetic Nervous System in Obese Animals --- p.59 / Chapter 11.2.2. --- Corticosteriods in Obese Animals --- p.61 / Chapter 11.2.3. --- Adrenergic Receptors in Obese Animals --- p.63 / Chapter 11.2.4. --- Insulin in Obese Animals --- p.64 / Chapter 12. --- Pregnancy and Lactation and BAT --- p.67 / Chapter 12.1. --- Energy Balance During Pregnancy and Lactation --- p.67 / Chapter 12.2. --- Some Metabolic Changes During X Pregnancy and Lactation --- p.68 / Chapter 12.3. --- Role of BAT in Pregnancy and Lactation --- p.70 / Chapter 12.4. --- Mechanism of Regulation of Thermogenesis during Pregnancy and Lactation --- p.71 / Chapter 13. --- Factors Controlling the Thermogenesis --- p.75 / Chapter 13.1. --- Sympathetic Nervous Control --- p.75 / Chapter 13.1.1. --- Studies of Administration of Noradrenaline --- p.75 / Chapter 13.1.2. --- Control of the Fuel Supply to BAT by Sympathetic Nervous System --- p.77 / Chapter 13.1.3. --- Sympathetic denervation --- p.78 / Chapter 13.2. --- Hormonal Control --- p.79 / Chapter 13.2.1. --- Thyroid Hormone --- p.79 / Chapter 13.2.2. --- Insulin --- p.81 / Chapter 13.2.3. --- Pituitary Hormones --- p.83 / Chapter 13.2.4. --- Glucocorticoids --- p.83 / Chapter 13.2.5. --- Corticotropin-Releasing Factor --- p.85 / Chapter 14. --- Aims of the Study --- p.87 / Chapter CHAPTER II --- ISOLATION AND PURIFICATION OF UCP AND DEVELOPMENT OF AN ENZYME LINKED IMMUNOSORBENT ASSAY FOR UCP / Chapter 1. --- INTRODUCTION --- p.88 / Chapter 2. --- MATERIALS AND METHODS --- p.89 / Chapter 2.1. --- Animals --- p.89 / Chapter 2.2. --- Collection of BAT --- p.89 / Chapter 2.3. --- Isolation of Mitochondria --- p.90 / Chapter 2.4. --- Electron Microscopy (EM) of Isolated BAT Mitochondria --- p.92 / Chapter 2.5. --- Measurement of Protein and Cytochrome C Oxidase Activity --- p.94 / Chapter 2.5.1. --- Measurement of Protein Concentration --- p.94 / Chapter 2.5.2. --- Measurement of Cytochrome C Oxidase Activity --- p.99 / Chapter 2.6. --- GDP Binding Assay of BAT Mitochondria --- p.101 / Chapter 2.6.1. --- GDP Binding Assay of Mitochondria by Centrifugation Method --- p.103 / Chapter 2.6.2. --- GDP: Binding Activity by Equilibrium Dialysis --- p.106 / Chapter 2.6.3. --- GDP Binding by Microfiltration Method --- p.108 / Chapter 2.7. --- Experiments Designed for Validation of GDP Binding Assay --- p.109 / Chapter 2.7.1. --- GDP Binding Activity in BAT Mitochondria after Noradrenaline Treatment --- p.109 / Chapter 2.7.2. --- GDP Binding Activity in BAT Mitochondria after Cold Acclimation and Noradrenaline Treatment --- p.110 / Chapter 2.7.3. --- Effect of Food Restriction on Cold Acclimated Rats --- p.110 / Chapter 2.7.4. --- GDP Binding Activity of BAT Mitochondria of Rats of Different Ages --- p.111 / Chapter 2.8. --- Isolation and Purification of UCP --- p.111 / Chapter 2.9. --- Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) --- p.115 / Chapter 2.10. --- Methods for Raising Anti-Rat-UCP Antibody and the Characterization of Antiserum --- p.120 / Chapter 2.10.1. --- Raising Rabbit Anti-Rat-UCP Antibody --- p.120 / Chapter 2.10.2. --- Western Blot Analysis For Cross Reactivity Study --- p.120 / Chapter 2.10.3. --- Immuno-Autoradiographic Method for Detection of Specificity of Rabbit Anti-Rat UCP Antiserum --- p.121 / Chapter 2.11. --- Enzyme Linked Immunosorbent Assay For UCP --- p.124 / Chapter 2.12. --- Experiment Designed to Validate the ELISA --- p.129 / Chapter 2.13. --- Statistical Analysis --- p.129 / Chapter 3. --- RESULTS --- p.130 / Chapter 3.1. --- Electron Microscopy of Isolated BAT Mitochondria --- p.130 / Chapter 3.2. --- GDP Binding Assay of BAT Mitochondria --- p.130 / Chapter 3.3. --- Experiments Designed for Validation of GDP Binding Assay --- p.133 / Chapter 3.3.1. --- GDP Binding Activity of BAT Mitochondria after Noradrenaline Injection --- p.133 / Chapter 3.3.2. --- GDP Binding Activity of BAT Mitochondria after Cold Acclimation and Noradrenaline Treatment --- p.136 / Chapter 3.3.3. --- Effects of Food Restriction on Cold Acclimated Rats --- p.136 / Chapter 3.3.4. --- GDP Binding Activity of BAT Mitochondria from Rats of Different Ages --- p.140 / Chapter 3.4. --- Isolation and Purification of UCP --- p.140 / Chapter 3.4.1. --- Results of SDS-PAGE --- p.143 / Chapter 3.4.2. --- Results of GDP Binding Activity --- p.149 / Chapter 3.5. --- Rabbit Anti-rat-UCP Antibody and the Characterization of Antiserum --- p.151 / Chapter 3.5.1. --- Immuno-autoradiography for Specificity of Rabbit Anti-rat-UCP Antiserum --- p.153 / Chapter 3.5.1.1. --- Cross-reactivity of the Rabbit Anti-rat-UCP Antiserum to Mitochondrial Proteins of BAT and from other Tissues --- p.153 / Chapter 3.5.1.2. --- Cross-reactivity of the Rabbit Anti-rat-UCP Antiserum to BAT Mitochondrial Protein from Different Rodent Species --- p.156 / Chapter 3.5.1.3. --- Dose Response of Rabbit Anti-rat-UCP Antiserum to UCP --- p.159 / Chapter 3.6. --- ELISA of UCP --- p.161 / Chapter 3.6.1. --- Determination of Maximum Amount of UCP Binding on Microtitre Plate --- p.161 / Chapter 3.6.2. --- Antibody Dilution Curve --- p.161 / Chapter 3.6.3. --- Incubation Time for Enzyme-Substrate Reaction --- p.163 / Chapter 3.6.4. --- Competitive ELISA --- p.163 / Chapter 3.6.5. --- Precision of ELISA --- p.167 / Chapter 3.7. --- Experiment Designed for Validation of ELISA by Measuring UCP in Cold Acclimated Rats --- p.170 / Chapter 4. --- DISCUSSION --- p.172 / Chapter 4.1. --- GDP Binding Assay of BAT Mitochondria --- p.172 / Chapter 4.2. --- Isolation and Purification of UCP --- p.176 / Chapter 4.3. --- Development and Evaluation of ELISA --- p.178 / Chapter CHAPTER III --- CHANGES IN BAT DURING PREGNANCY AND LACTATION AND ROLE OF PROLACTIN / Chapter 1. --- INTRODUCTION --- p.184 / Chapter 2. --- MATERIALS AND METHODS --- p.187 / Chapter 2.1. --- Animal --- p.187 / Chapter 2.2. --- Experimental Designs --- p.187 / Chapter 2.2.1. --- "Effects of Pregnancy, Lactation and Post Weaning on BAT" --- p.187 / Chapter 2.2.2. --- Effect of Metoclopramide on BAT --- p.188 / Chapter 2.2.3. --- Effect of Metoclopramide and Bromocriptine on BAT --- p.188 / Chapter 2.2.4. --- Effect of PRL Injection on BAT --- p.189 / Chapter 2.2.5. --- Continuous infusion of PRL --- p.189 / Chapter 2.6.6. --- Measurements of BAT Parameters --- p.191 / Chapter 2.2.7. --- RIA of serrum PRL --- p.191 / Chapter 2.2.8. --- PRL Receptors in BAT --- p.197 / Chapter 2.4. --- Statistical Analysis --- p.201 / Chapter 3. --- RESULTS --- p.202 / Chapter 3.1. --- Effects of Pregnancy and Lactation --- p.202 / Chapter 3.1.1. --- Food Consumption and Body Weight --- p.202 / Chapter 3.1.2. --- BAT --- p.205 / Chapter 3.1.3. --- Serum PRL level --- p.209 / Chapter 3.2. --- Effects of PRL njection --- p.213 / Chapter 3.3. --- Effects of Continuous Infusion of PRL on BAT --- p.213 / Chapter 3.4. --- Effects of Metoclopramide on BAT --- p.216 / Chapter 3.5. --- Effects of Bromocriptine and Metoclopramide on BAT --- p.216 / Chapter 3.6. --- PRL Receptor in BAT --- p.219 / Chapter 4. --- DISCUSSION --- p.223 / GENERAL CONCLUSION --- p.236

Thesis (Ph. D.)--Ohio State University, 2007. / Includes bibliographical references (p. 139-160).

No description available.

Chronic exposure of humans or rodents to high calorie diets leads to hypertriglyceridemia and ectopic lipid deposition throughout the body, resulting in metabolic disease. Cellular lipids are stored in organelles termed lipid droplets (LDs) that are regulated by tissue-specific LD proteins. These proteins are critical for lipid homeostasis, as humans with LD protein mutations manifest metabolic dysfunction. Identification of novel components of the LD machinery could shed light on human disease mechanisms and suggest potential therapeutics for Type 2 Diabetes. Microarray analyses pinpointed the largely unstudied Hypoxia-Inducible Gene 2 (Hig2) as a gene that was highly expressed in obese human adipocytes. Imaging studies demonstrated that Hig2 localized to LDs in mouse hepatocytes and the human SGBS adipocyte cell line. Thus, this work examined the role of Hig2 as a LD protein in liver and adipose tissue. Hig2 deficiency reduced triglyceride deposition in hepatocytes; conversely, ectopic Hig2 expression promoted lipid deposition. Furthermore, liver-specific Hig2-deficient mice displayed improved glucose tolerance and reduced liver triglyceride content. Hig2 deficiency increased lipolysis and -oxidation, accounting for the reduced triglyceride accumulation. Similarly, adipocyte-specific Hig2-deficient mice displayed improved glucose tolerance, reduced adipose tissue weight and brown adipose tissue that was largely cleared of lipids. These improvements were abrogated when the animals were placed in thermoneutral housing and brown adipocyte-specific Hig2-deficient mice also displayed improved glucose tolerance, suggesting that active brown fat largely mediates the metabolic phenotype of Hig2 deletion. Thus, this work demonstrates that Hig2 localizes to LDs in liver and adipose tissue and promotes glucose intolerance.

Adipose tissue is one of the most dynamic tissues in the body and is vital for metabolic homeostasis. In the case of excess nutrient uptake, adipose tissue expands to store excess energy in the form of lipids, and in the case of reduced nutrient intake, adipose tissue can shrink and release this energy. Adipocytes are most functional when the balance between these two processes is intact. To understand the molecular mechanisms that drive insulin resistance or conversely preserve the metabolically healthy state in obese individuals, our laboratory performed a screen for differentially regulated adipocyte genes in insulin resistant versus insulin sensitive subjects who had been matched for BMI. From this screen, we identified the type II transmembrane protein tenomodulin (TNMD), which had been previously implicated in glucose tolerance in gene association studies. TNMD was upregulated in omental fat samples isolated from the insulin resistant patient group compared to insulin sensitive individuals. TNMD was predominantly expressed in primary adipocytes compared to the stromal vascular fraction from this adipose tissue. Furthermore, TNMD expression was greatly increased in human preadipocytes by differentiation, and silencing TNMD blocked adipogenic gene induction and adipogenesis, suggesting its role in adipose tissue expansion. Upon high fat diet feeding, transgenic mice overexpressing Tnmd specifically in adipose tissue developed increased epididymal adipose tissue (eWAT) mass without a difference in mean cell size, consistent with elevated in vitro adipogenesis. Moreover, preadipocytes isolated from transgenic epididymal adipose tissue demonstrated higher BrdU incorporation than control littermates, suggesting elevated preadipocyte proliferation. In TNMD overexpressing mice, lipogenic genes PPARG, FASN, SREBP1c and ACLY were upregulated in eWAT as was UCP-1 in brown fat, while liver triglyceride content was reduced. Transgenic animals displayed improved systemic insulin sensitivity, as demonstrated by decreased inflammation and collagen accumulation and increased Akt phosphorylation in eWAT. Thus, the data we present here suggest that TNMD plays a protective role during visceral adipose tissue expansion by promoting adipogenesis and inhibiting inflammation and tissue fibrosis.

O tecido adiposo marrom (TAM), caracterizado pela presença da proteína termogênica UCP-1, é conhecido há muitas décadas como um tecido termogênico em mamíferos, porém sua significância clínica em humanos era considerada pequena, com exceção de neonatos, até que o desenvolvimento e uso de métodos de PET-FDG terem demonstrado que humanos adultos também possuem TAM ativo, especialmente após exposição ao frio. Essa descoberta levou a um enorme aumento nas pesquisas sobre o assunto, já que sua ativação, levando a um aumento do gasto energético, poderia, pelo menos na teoria, ser uma possível arma no tratamento da obesidade e diabetes tipo 2 e sua redução ou ausência ser uma causa de ganho de peso. Muitos compostos vêm sendo estudados como possíveis recrutadores e ativdadores desse tecido. A melatonina é um deles, embora nenhum estudo tenha sido feito em humanos. A melatonina, um hormônio pineal sintetizado à noite com um papel crítico na sincronização do ritmo circadiano, é estudado há várias décadas como um regulador chave do metabolismo energético em diversas espécies animais. Ratos pinealectomizados ganham peso e tem distúrbios metabólicos durante sua vida, e a suplementação noturna de melatonina, reverte estas alterações, sem redução da ingesta alimentar. Devido a isso, uma hipótese é que o papel central da melatonina no metabolismo energético inclui sua função no gasto energético, possivelmente relacionado à ativação do TAM. Muitos modelos experimentais, a maioria em animais hibernantes, demonstraram o papel da melatonina no recrutamento do TAM. Nesse estudo, o objetivo é determinar se a suplementação de melatonina para indivíduos e animais de experimentação (ratos Wistar) deficientes de melatonina aumenta sua ativação. Foi encontrado que, em ratos Wistar, animais pinelaectomizados possuem uma capacidade termogênica do TAM reduzida após exposição ao frio comparado com a temperatura ambiente, e a suplementação de melatonina normaliza essa capacidade termogênica. Esse dado sugere um papel da melatonina na resposta máxima de ativação do TAM após um desafio ao frio agudo. Também foi observado um aumento de expressão de UCP-1 (RNA) em animais repostos com melatonina, tanto em controles como em pinealectomizados, e animais pinealectomizados não repostos apresentam uma expressão de UCP-1 menor que um grupo controle. Em humanos, a suplementação de melatonina aumenta o volume e atividade do TAM em quatro indivíduos pinealectomizados (por tumores pineais) com baixo nível de melatonina no basal, analisado por tomografia de emissão de prótons acoplada a ressonância magnética (PET-RM). Embora a análise do TAM em ambos os protocolos tenha sido distinta, seus resultados apontam para a mesma regulação positiva do TAM pela melatonina. A termografia infravermelha (TIV) foi também realizada em humanos, com aumento de atividade de TAM após exposição ao frio, poréma correlação entre as respostas com a TIV e o PET-RM foi moderada e não significativa. Diferenças entre o protocolo frio e limitação da TIV em indivíduos mais obesos podem ter contribuído para esses resultados. Uma relação positiva da suplementação de melatonina nos lípides (principalmente colesterol e triglicérides) também foi encontrada, porém sem impacto na gordura hepática / Brown adipose tissue (BAT), characterized by the presence of the thermogenic protein UCP-1 have long been known as a thermogenic tissue in mammals, however its significance in humans was considered minor, with the exception of newborns, until FDG-PET exams demonstrated that human adults still have active BAT, especially after cold exposure. This prompted to an incredible increase in research on the field, since its activation, leading to increased energy expenditure could, at least theoretically, be a possible tool for the treatment of obesity and type 2 diabetes and its reduction or absence be a cause of weight gain. Many compounds aiming to recruit and activate BAT have been studied. Melatonin has been one of them, although no study has been performed in humans. Melatonin, a pineal hormone synthetized at night with a critical role in the synchronization of circadian rhythms, has long been studied as a key regulator of energy metabolism in many animal species. Pinealectomized rats gain weight and have metabolic disturbances during life, and the circadian supplementation of melatonin, at night, reverts these alterations, without decrease in energy intake. Due to that, it is hypothesized that a main role of melatonin in energy metabolism includes its action on energy expenditure, possibly related to activation of BAT. Many experimental models, mainly in hibernating animals, have shown a role of melatonin on BAT recruitment. In the present study, we ought to determine if the supplementation of melatonin for melatonin deficient subjects and experimental animals (Wistar rats) increases BAT activation. We found, in Wistar rats, that pinealectomized animals have a reduced BAT thermogenic capacity after acute cold exposure compared with ambient temperature, and melatonin supplementation in this animals leads to normalization of BAT thermogenic capacity. This data suggests a role of melatonin in improving the maximal response of BAT after an acute challenge. We also found that melatonin supplementation increases UCP-1 RNA expression both in control and pinealectomized rats, and pinealectomized rats without supplementation have a reduced UCP-1 expression compared with controls. In humans, we found that melatonin supplementation increased BAT volume and activity in four pinealectomized (due to pineal tumors) individuals with low melatonin at baseline, analyzed by Positron Emission Tomography associated with magnetic resonance (PET-MR). Although the analysis of BAT in both studies was different, their results point to the same positive regulation of BAT by melatonin. We also performed infrared termography (IRT) in humans, but the results were not conclusive since although we also found an increase in BAT activity measured in Watts, the correlation between the methods was moderate. The difference may be due to different protocols of cold exposure between methods, probably inadequate in IRT, as well as maybe to a limitation of IRT in more obese individuals. We also found that melatonin supplementation in melatonin deficient humans may have a positive impact on blood lipid concentrations, (mainly total cholesterol and triglycerides) but, at least for the time studied, does not appear to have an impact on liver fat

O tecido adiposo marrom (TAM), caracterizado pela presença da proteína termogênica UCP-1, é conhecido há muitas décadas como um tecido termogênico em mamíferos, porém sua significância clínica em humanos era considerada pequena, com exceção de neonatos, até que o desenvolvimento e uso de métodos de PET-FDG terem demonstrado que humanos adultos também possuem TAM ativo, especialmente após exposição ao frio. Essa descoberta levou a um enorme aumento nas pesquisas sobre o assunto, já que sua ativação, levando a um aumento do gasto energético, poderia, pelo menos na teoria, ser uma possível arma no tratamento da obesidade e diabetes tipo 2 e sua redução ou ausência ser uma causa de ganho de peso. Muitos compostos vêm sendo estudados como possíveis recrutadores e ativdadores desse tecido. A melatonina é um deles, embora nenhum estudo tenha sido feito em humanos. A melatonina, um hormônio pineal sintetizado à noite com um papel crítico na sincronização do ritmo circadiano, é estudado há várias décadas como um regulador chave do metabolismo energético em diversas espécies animais. Ratos pinealectomizados ganham peso e tem distúrbios metabólicos durante sua vida, e a suplementação noturna de melatonina, reverte estas alterações, sem redução da ingesta alimentar. Devido a isso, uma hipótese é que o papel central da melatonina no metabolismo energético inclui sua função no gasto energético, possivelmente relacionado à ativação do TAM. Muitos modelos experimentais, a maioria em animais hibernantes, demonstraram o papel da melatonina no recrutamento do TAM. Nesse estudo, o objetivo é determinar se a suplementação de melatonina para indivíduos e animais de experimentação (ratos Wistar) deficientes de melatonina aumenta sua ativação. Foi encontrado que, em ratos Wistar, animais pinelaectomizados possuem uma capacidade termogênica do TAM reduzida após exposição ao frio comparado com a temperatura ambiente, e a suplementação de melatonina normaliza essa capacidade termogênica. Esse dado sugere um papel da melatonina na resposta máxima de ativação do TAM após um desafio ao frio agudo. Também foi observado um aumento de expressão de UCP-1 (RNA) em animais repostos com melatonina, tanto em controles como em pinealectomizados, e animais pinealectomizados não repostos apresentam uma expressão de UCP-1 menor que um grupo controle. Em humanos, a suplementação de melatonina aumenta o volume e atividade do TAM em quatro indivíduos pinealectomizados (por tumores pineais) com baixo nível de melatonina no basal, analisado por tomografia de emissão de prótons acoplada a ressonância magnética (PET-RM). Embora a análise do TAM em ambos os protocolos tenha sido distinta, seus resultados apontam para a mesma regulação positiva do TAM pela melatonina. A termografia infravermelha (TIV) foi também realizada em humanos, com aumento de atividade de TAM após exposição ao frio, poréma correlação entre as respostas com a TIV e o PET-RM foi moderada e não significativa. Diferenças entre o protocolo frio e limitação da TIV em indivíduos mais obesos podem ter contribuído para esses resultados. Uma relação positiva da suplementação de melatonina nos lípides (principalmente colesterol e triglicérides) também foi encontrada, porém sem impacto na gordura hepática / Brown adipose tissue (BAT), characterized by the presence of the thermogenic protein UCP-1 have long been known as a thermogenic tissue in mammals, however its significance in humans was considered minor, with the exception of newborns, until FDG-PET exams demonstrated that human adults still have active BAT, especially after cold exposure. This prompted to an incredible increase in research on the field, since its activation, leading to increased energy expenditure could, at least theoretically, be a possible tool for the treatment of obesity and type 2 diabetes and its reduction or absence be a cause of weight gain. Many compounds aiming to recruit and activate BAT have been studied. Melatonin has been one of them, although no study has been performed in humans. Melatonin, a pineal hormone synthetized at night with a critical role in the synchronization of circadian rhythms, has long been studied as a key regulator of energy metabolism in many animal species. Pinealectomized rats gain weight and have metabolic disturbances during life, and the circadian supplementation of melatonin, at night, reverts these alterations, without decrease in energy intake. Due to that, it is hypothesized that a main role of melatonin in energy metabolism includes its action on energy expenditure, possibly related to activation of BAT. Many experimental models, mainly in hibernating animals, have shown a role of melatonin on BAT recruitment. In the present study, we ought to determine if the supplementation of melatonin for melatonin deficient subjects and experimental animals (Wistar rats) increases BAT activation. We found, in Wistar rats, that pinealectomized animals have a reduced BAT thermogenic capacity after acute cold exposure compared with ambient temperature, and melatonin supplementation in this animals leads to normalization of BAT thermogenic capacity. This data suggests a role of melatonin in improving the maximal response of BAT after an acute challenge. We also found that melatonin supplementation increases UCP-1 RNA expression both in control and pinealectomized rats, and pinealectomized rats without supplementation have a reduced UCP-1 expression compared with controls. In humans, we found that melatonin supplementation increased BAT volume and activity in four pinealectomized (due to pineal tumors) individuals with low melatonin at baseline, analyzed by Positron Emission Tomography associated with magnetic resonance (PET-MR). Although the analysis of BAT in both studies was different, their results point to the same positive regulation of BAT by melatonin. We also performed infrared termography (IRT) in humans, but the results were not conclusive since although we also found an increase in BAT activity measured in Watts, the correlation between the methods was moderate. The difference may be due to different protocols of cold exposure between methods, probably inadequate in IRT, as well as maybe to a limitation of IRT in more obese individuals. We also found that melatonin supplementation in melatonin deficient humans may have a positive impact on blood lipid concentrations, (mainly total cholesterol and triglycerides) but, at least for the time studied, does not appear to have an impact on liver fat

Recent studies suggest adipose tissue plays a critical role in regulating whole body energy homeostasis in both animals and humans. In particular, activating brown adipose tissue (BAT) activity is now appreciated as a potential therapeutic strategy against obesity and metabolic disease. However, the signaling circuits that coordinate nutrient uptake and BAT function are poorly understood. Here, I investigated the role of the nutrient-sensing mTOR signaling pathway in BAT by conditionally deleting Rictor, which encodes an essential component of mTOR Complex 2 (mTORC2) either in brown adipocyte precursors or mature brown adipocytes. In general, inhibiting BAT mTORC2 reduces glucose uptake and de novo lipogenesis pathways while increases lipid uptake and oxidation pathways indicating a switch in fuel utilization. Moreover, several key thermogenic factors (Ucp1, Pgc1α, and Irf4) are elevated in Rictor-deficient BAT, resulting in enhanced thermogenesis. Accordingly, mice with mTORC2 loss in BAT are protected from HFD-induced obesity and metabolic disease at thermoneutrality. In vitro culture experiments further suggest that mTORC2 cell-autonomously regulates the BAT thermogenic program, especially Ucp1 expression, which depends on FoxO1 activity. Mechanistically, mTORC2 appears to inhibit FoxO1 by facilitating its lysine-acetylation but not through the canonical AKT-mediated phosphorylation pathway. Finally, I also provide evidence that β-adrenergic signaling which normally triggers thermogenesis also induces FoxO1 deacetylation in BAT. Based on these data, I propose a model in which mTORC2 functions in BAT as a critical signaling hub for coordinating nutrient uptake, fuel utilization, and thermogenic gene expression. These data provide a foundation for future studies into the mTORC2-FoxO1 signaling axis in different metabolic tissues and physiological conditions.

No description available.