RESUMO
Increasing brown adipose tissue (BAT) thermogenesis in mice and humans improves metabolic health and understanding BAT function is of interest for novel approaches to counteract obesity. The role of long noncoding RNAs (lncRNAs) in these processes remains elusive. We observed maternally expressed, imprinted lncRNA H19 increased upon cold-activation and decreased in obesity in BAT. Inverse correlations of H19 with BMI were also observed in humans. H19 overexpression promoted, while silencing of H19 impaired adipogenesis, oxidative metabolism and mitochondrial respiration in brown but not white adipocytes. In vivo, H19 overexpression protected against DIO, improved insulin sensitivity and mitochondrial biogenesis, whereas fat H19 loss sensitized towards HFD weight gains. Strikingly, paternally expressed genes (PEG) were largely absent from BAT and we demonstrated that H19 recruits PEG-inactivating H19-MBD1 complexes and acts as BAT-selective PEG gatekeeper. This has implications for our understanding how monoallelic gene expression affects metabolism in rodents and, potentially, humans.
Assuntos
Tecido Adiposo Marrom/fisiologia , Impressão Genômica , Obesidade/genética , RNA Longo não Codificante/genética , Tecido Adiposo Marrom/patologia , Tecido Adiposo Branco/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Dieta Hiperlipídica/efeitos adversos , Metabolismo Energético/genética , Feminino , Regulação da Expressão Gênica , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Obesidade/etiologiaRESUMO
Increased visceral fat is associated with a high risk of diabetes and metabolic syndrome and is in part caused by excessive glucocorticoids (GCs). However, the molecular mechanisms remain undefined. We now identify the GC-dependent gene LIM domain only 3 (LMO3) as being selectively upregulated in a depot-specific manner in human obese visceral adipose tissue, localizing primarily in the adipocyte fraction. Visceral LMO3 levels were tightly correlated with expression of 11ß-hydroxysteroid dehydrogenase type-1 (HSD11B1), the enzyme responsible for local activation of GCs. In early human adipose stromal cell differentiation, GCs induced LMO3 via the GC receptor and a positive feedback mechanism involving 11ßHSD1. No such induction was observed in murine adipogenesis. LMO3 overexpression promoted, while silencing of LMO3 suppressed, adipogenesis via regulation of the proadipogenic PPARγ axis. These results establish LMO3 as a regulator of human adipogenesis and could contribute a mechanism resulting in visceral-fat accumulation in obesity due to excess glucocorticoids.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Adipogenia/fisiologia , Gordura Intra-Abdominal/fisiologia , Proteínas com Domínio LIM/fisiologia , Obesidade/fisiopatologia , Regulação para Cima/fisiologia , 11-beta-Hidroxiesteroide Desidrogenase Tipo 1/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Adipócitos/patologia , Adipogenia/genética , Adulto , Animais , Estudos de Casos e Controles , Diferenciação Celular/fisiologia , Células Cultivadas , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Experimental/fisiopatologia , Modelos Animais de Doenças , Feminino , Glucocorticoides/fisiologia , Humanos , Gordura Intra-Abdominal/patologia , Proteínas com Domínio LIM/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Camundongos SCID , Pessoa de Meia-Idade , Obesidade/patologia , PPAR gama/fisiologia , Regulação para Cima/genéticaRESUMO
OBJECTIVE: Regional citrate anticoagulation has emerged as a promising method in critically ill patients at high risk of bleeding. However, in patients with liver failure, citrate accumulation may lead to acid-base and electrolyte imbalances, notably of calcium. The aim of this study was to evaluate the feasibility and safety of regional citrate anticoagulation during liver support using a molecular adsorbent recirculating system as well as its effects on electrolyte and acid-base balance in patients with liver failure. DESIGN: Prospective observational study. SETTING: University hospital. PATIENTS: Twenty critically ill patients supported by molecular adsorbent recirculating system resulting from liver failure between January 2007 and May 2009. MEASUREMENTS AND MAIN RESULTS: The median duration of molecular adsorbent recirculating system treatment was 20 hrs (interquartile range, 18-22 hrs). Two of 77 molecular adsorbent recirculating system treatments (2%) were prematurely discontinued as a result of filter clotting and bleeding, respectively. The median citrate infusion rate, necessary to maintain the postfilter ionized calcium between 0.2 and 0.4 mmol/L, was 3.1 mmol/L (interquartile range, 2.3-4 mmol/L) blood flow. The median calcium chloride substitution rate was 0.9 mmol/L (0.3-1.7 mmol/L) dialysate. Total serum calcium remained stable during molecular adsorbent recirculating system treatments. There was a statistically significant increase of the ratio of total calcium to systemic ionized calcium (2.04 ± 0.32 mmol/L to 2.17 ± 0.35; p = .01), which reflected citrate accumulation resulting from liver failure. Under close monitoring, no clinically relevant electrolytes or acid-base disorders were observed. CONCLUSIONS: Our results suggest that regional citrate anticoagulation is a safe and feasible method to maintain adequate circuit lifespan without increasing the risk of hemorrhagic complications while maintaining a normal acid-base as well as electrolyte balance in patients with liver failure supported by molecular adsorbent recirculating system.