Perilipin regulates the thermogenic actions of norepinephrine in brown adipose tissue

In response to cold, norepinephrine (NE)-induced triacylglycerol hydrolysis (lipolysis) in adipocytes of brown adipose tissue (BAT) provides fatty acid substrates to mitochondria for heat generation (adaptive thermogenesis). NE-induced lipolysis is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin, a lipid droplet-associated protein that is the major regulator of lipolysis. We investigated the role of perilipin PKA phosphorylation in BAT NE-stimulated thermogenesis using a novel mouse model in which a mutant form of perilipin, lacking all six PKA phosphorylation sites, is expressed in adipocytes of perilipin knockout (Peri KO) mice. Here, we show that despite a normal mitochondrial respiratory capacity, NE-induced lipolysis is abrogated in the interscapular brown adipose tissue (IBAT) of these mice. This lipolytic constraint is accompanied by a dramatic blunting (∼70%) of the in vivo thermal response to NE. Thus, in the presence of perilipin, PKA-mediated perilipin phosphorylation is essential for NE-dependent lipolysis and full adaptive thermogenesis in BAT. In IBAT of Peri KO mice, increased basal lipolysis attributable to the absence of perilipin is sufficient to support a rapid NE-stimulated temperature increase (∼3.0°C) comparable to that in wild-type mice. This observation suggests that one or more NE-dependent mechanism downstream of perilipin phosphorylation is required to initiate and/or sustain the IBAT thermal response

Combined treatment with caffeic and ferulic acid from Baccharis uncinella C. DC. (Asteraceae) protects against metabolic syndrome in mice

Fractionation of the EtOH extract from aerial parts of Baccharis uncinella C. DC. (Asteraceae) led to isolation of caffeic and ferulic acids, which were identified from spectroscopic and spectrometric evidence. These compounds exhibit antioxidant and anti-inflammatory properties and have been shown to be effective in the prevention/treatment of metabolic syndrome. This study investigated whether the combined treatment of caffeic and ferulic acids exhibits a more significant beneficial effect in a mouse model with metabolic syndrome. The combination treatment with caffeic and ferulic acids was tested for 60 days in C57 mice kept on a high-fat (40%) diet. The data obtained indicated that treatment with caffeic and ferulic acids prevented gain in body weight induced by the high-fat diet and improved hyperglycemia, hypercholesterolemia and hypertriglyceridemia. The expression of a number of metabolically relevant genes was affected in the liver of these animals, showing that caffeic and ferulic acid treatment results in increased cholesterol uptake and reduced hepatic triglyceride synthesis in the liver, which is a likely explanation for the prevention of hepatic steatosis. In conclusion, the combined treatment of caffeic and ferulic acids displayed major positive effects towards prevention of multiple aspects of the metabolic syndrome and liver steatosis in an obese mouse model.CAPESFAPESPMackPesquisaUniv Presbiteriana Mackenzie, Programa Posgrad Disturbios Desenvolvimento, Ctr Ciencias Biol & Saude, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Med Translac, Escola Paulista Med, Sao Paulo, SP, BrazilUniv Fed ABC, Ctr Ciencias Nat & Humanas, Sao Paulo, SP, BrazilEscola Ciencias Med, Dept Ciencias Patol, Sao Paulo, SP, BrazilUniv Presbiteriana Mackenzie, Escola Engn, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Sao Paulo, SP, BrazilRush Univ & Med Ctr, Dept Internal Med, Div Endocrinol & Metab, Chicago, IL 60612 USAUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Sao Paulo, SP, BrazilFAPESP: 2011/21847-6Web of Scienc

A low-protein, high-carbohydrate diet increases browning in perirenal adipose tissue but not in inguinal adipose tissue

Objective The aim of this study was to evaluate the browning and origin of fatty acids (FAs) in the maintenance of triacylglycerol (TG) storage and/or as fuel for thermogenesis in perirenal adipose tissue (periWAT) and inguinal adipose tissue (ingWAT) of rats fed a low-protein, high-carbohydrate (LPHC) diet. Methods LPHC (6% protein, 74% carbohydrate) or control (C; 17% protein, 63% carbohydrate) diets were administered to rats for 15 d. The tissues were stained with hematoxylin and eosin for histologic analysis. The content of uncoupling protein 1 (UCP1) was determined by immunofluorescence. Levels of T-box transcription factor (TBX1), PR domain containing 16 (PRDM16), adipose triacylglycerol lipase (ATGL), hormone-sensitive lipase, lipoprotein lipase (LPL), glycerokinase, phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 4, β3-adrenergic receptor (AR), β1-AR, protein kinase A (PKA), adenosine-monophosphate-activated protein kinase (AMPK), and phospho-AMPK were determined by immunoblotting. Serum fibroblast growth factor 21 (FGF21) was measured using a commercial kit (Student's t tests, P < 0.05). Results The LPHC diet increased FGF21 levels by 150-fold. The presence of multilocular adipocytes, combined with the increased contents of UCP1, TBX1, and PRDM16 in periWAT of LPHC-fed rats, suggested the occurrence of browning. The contents of β1-AR and LPL were increased in the periWAT. The ingWAT showed higher ATGL and PEPCK levels, phospho-AMPK/AMPK ratio, and reduced β3-AR and PKA levels. Conclusion These findings suggest that browning occurred only in the periWAT and that higher utilization of FAs from blood lipoproteins acted as fuel for thermogenesis. Increased glycerol 3-phosphate generation by glyceroneogenesis increased FAs reesterification from lipolysis, explaining the increased TG storage in the ingWAT.IRSES FP

Functional Evolution of Leptin of Ochotona curzoniae in Adaptive Thermogenesis Driven by Cold Environmental Stress

BACKGROUND: Environmental stress can accelerate the directional selection and evolutionary rate of specific stress-response proteins to bring about new or altered functions, enhancing an organism's fitness to challenging environments. Plateau pika (Ochotona curzoniae), an endemic and keystone species on Qinghai-Tibetan Plateau, is a high hypoxia and low temperature tolerant mammal with high resting metabolic rate and non-shivering thermogenesis to cope in this harsh plateau environment. Leptin is a key hormone related to how these animals regulate energy homeostasis. Previous molecular evolutionary analysis helped to generate the hypothesis that adaptive evolution of plateau pika leptin may be driven by cold stress. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis, recombinant pika leptin was first purified. The thermogenic characteristics of C57BL/6J mice injected with pika leptin under warm (23±1°C) and cold (5±1°C) acclimation is investigated. Expression levels of genes regulating adaptive thermogenesis in brown adipose tissue and the hypothalamus are compared between pika leptin and human leptin treatment, suggesting that pika leptin has adaptively and functionally evolved. Our results show that pika leptin regulates energy homeostasis via reduced food intake and increased energy expenditure under both warm and cold conditions. Compared with human leptin, pika leptin demonstrates a superior induced capacity for adaptive thermogenesis, which is reflected in a more enhanced β-oxidation, mitochondrial biogenesis and heat production. Moreover, leptin treatment combined with cold stimulation has a significant synergistic effect on adaptive thermogenesis, more so than is observed with a single cold exposure or single leptin treatment. CONCLUSIONS/SIGNIFICANCE: These findings support the hypothesis that cold stress has driven the functional evolution of plateau pika leptin as an ecological adaptation to the Qinghai-Tibetan Plateau

Substrate cycling between de novo lipogenesis and lipid oxidation: a thermogenic mechanism against skeletal muscle lipotoxicity and glucolipotoxicity

Life is a combustion, but how the major fuel substrates that sustain human life compete and interact with each other for combustion has been at the epicenter of research into the pathogenesis of insulin resistance ever since Randle proposed a 'glucose-fatty acid cycle' in 1963. Since then, several features of a mutual interaction that is characterized by both reciprocality and dependency between glucose and lipid metabolism have been unravelled, namely: 1. the inhibitory effects of elevated concentrations of fatty acids on glucose oxidation (via inactivation of mitochondrial pyruvate dehydrogenase or via desensitization of insulin-mediated glucose transport), 2. the inhibitory effects of elevated concentrations of glucose on fatty acid oxidation (via malonyl-CoA regulation of fatty acid entry into the mitochondria), and more recently 3. the stimulatory effects of elevated concentrations of glucose on de novo lipogenesis, that is, synthesis of lipids from glucose (via SREBP1c regulation of glycolytic and lipogenic enzymes). This paper first revisits the physiological significance of these mutual interactions between glucose and lipids in skeletal muscle pertaining to both blood glucose and intramyocellular lipid homeostasis. It then concentrates upon emerging evidence, from calorimetric studies investigating the direct effect of leptin on thermogenesis in intact skeletal muscle, of yet another feature of the mutual interaction between glucose and lipid oxidation: that of substrate cycling between de novo lipogenesis and lipid oxidation. It is proposed that this energy-dissipating substrate cycling that links glucose and lipid metabolism to thermogenesis could function as a 'fine-tuning' mechanism that regulates intramyocellular lipid homeostasis, and hence contributes to the protection of skeletal muscle against lipotoxicity

Iodothyronine deiodinases: relevance to thyroid hormone homeostasis and brown adipose tissue

As três desiodases de iodotironina catalizam a iniciação (D1, D2) e o término (D3) dos efeitos dos hormônios tireoideanos nos vertebrados. Enquanto D1 e D3 são proteínas de meia-vida longa localizadas na membrana plasmática, a D2 é uma proteína residente do retículo endoplasmático com meia-vida de apenas 20 min. Nesta série de estudos, foram investigados: (1) os efeitos causados pela combinação da disrupção do gene da D2 (Dio2-/-) com a deficiência familiar de D1 (camundongos C3H) na homeostase do hormônio tiroideano e apesar da múltipla deficiência de D1 e D2, animais C3H-D2KO apresentam T3 sérico na faixa eutiroidea, sugerindo mecanismos compensatórios, que promovem (i) aumento de aproximadamente 2 vezes nos níveis de T4 sérico, comparando com camundongos da linhagem C57/BL6 (C57) e, (ii) aumento da atividade de D1 hepática e renal, 8,4 e 2,0 vezes, respectivamente, em comparação com animais C3H. E ainda, este mecanismo compensatório não depende de aumento da atividade da glândula tiróide ou diminuição do “clearance” de T3 mediado pela D3; (2) o papel da D2 no sistema de retroalimentação negativa do TSH mediado pelo T4 na pituitária, o qual se revelou fundamental neste sistema e que, apesar de sofrer degradação induzida pelo substrato como em qualquer outro tecido que expressa D2, a alta taxa de síntese da enzima assegura atividade e, conseqüentemente, produção constante de T3, mesmo na vigência de doses de T4 muito acima do fisiológico; (3) a importância da geração de T3 adaptativa mediada pela D2 para a resposta termogênica do BAT, a qual não está limitada a mediar a responsividade à catecolaminas, mas também promover lipogênese no tecido, essencial para fornecer substrato para oxidação mitocondrial e, conseqüentemente, desacoplamento e geração de calor; (4) o papel da D2 na conversão da célula pré-adiposa marrom em célula madura, que confirmou in vitro a importância da D2 para a capacidade termogênica deste tipo celular e seu papel chave no recrutamento do programa de diferenciação, o qual, na ausência de D2, apresenta um déficit de ~25%.The three iodothyronine deiodinases catalyze the initiation (D1,D2) and termination (D3) of thyroid hormone effects in vertebrates. While D1 and D3 are long-lived plasma membrane proteins, D2 is an endoplasmic reticulum resident protein with a half-life of only 20 min. In these series of studies, we investigated: (1) the effects in thyroid hormone homeostasis caused by the combined targeted disruption of D2 gene (Dio2-/-) and inbred D1 deficiency (C3H mice), and despite the multiple D1 and D2 deficiency, C3H-D2KO animals present serum T3 in the euthyroid range, suggesting compensatory mechanisms that promote (i) ~2 fold increase in serum T4, when compared to C57/BL6 (C57) mice and (ii) increase in hepatic and renal D1 activity of 8.4 and 2.0 fold, respectively, when comparing to C3H animals. Furthermore, this compensatory mechanism does not depend on increased thyroidal activity or decreased in D3-mediated T3 clearance.; (2) D2 role in the T4-mediated TSH feedback in the pituitary, which place D2 in a pivotal role in this system, and despite being target to the substrate induced degradation as in any other D2-expressing tissue, the high rate of D2 synthesis assure activity, and consequently, constant T3 production, even at high doses of T4, well above the physiological levels; (3) the importance of adaptive D2-mediated T3 generation to the BAT thermogenic response, which is not limited to mediate responsiveness to catecholamines, but also promote lipogenesis in the tissue, essential to make available substrate for mitochondrial oxidation and, consequently, uncoupling and heat generation; (4) D2 role in brown pre-adipocyte to mature cell conversion, confirming in vitro the importance of D2 to this cell type thermogenic capacity, and its key role in the differentiation program recruitment, which in D2 absence, presents a ~25% déficit.BV UNIFESP: Teses e dissertaçõe

Hypercaloric cafeteria-like diet induced UCP3 gene expression in skeletal muscle is impaired by hypothyroidism

The uncoupling protein UCP3 belongs to a family of mitochondrial carriers located in the inner mitochondrial membrane of certain cell types. It is expressed almost exclusively at high levels in skeletal muscle and its physiological role has not been fully determined in this tissue. In the present study we have addressed the possible interaction between a hypercaloric diet and thyroid hormone (T3), which are strong stimulators of UCP3 gene expression in skeletal muscle. Male Wistar rats weighing 180 ± 20 g were rendered hypothyroid by thyroidectomy and the addition of methimazole (0.05%; w/v) to drinking water after surgery. The rats were fed a hypercaloric cafeteria diet (68% carbohydrates, 13% protein and 18% lipids) for 10 days and sacrificed by decapitation. Subsequently, the gastrocnemius muscle was dissected, total RNA was isolated with Trizol? and UCP3 gene expression was determined by Northern blotting using a specific probe. Statistical analysis was performed by one-way analysis of variance (ANOVA) followed by the Student-Newman-Keuls post-test. Skeletal muscle UCP3 gene expression was decreased by 60% in hypothyroid rats and UCP3 mRNA expression was increased 70% in euthyroid cafeteria-fed rats compared to euthyroid chow-fed animals, confirming previous studies. Interestingly, the cafeteria diet was unable to stimulate UCP3 gene expression in hypothyroid animals (40% lower as compared to euthyroid cafeteria-fed animals). The results show that a hypercaloric diet is a strong stimulator of UCP3 gene expression in skeletal muscle and requires T3 for an adequate action