Hao Q.,CAS Beijing Institute of Genomics |
Hao Q.,University of Southern Denmark |
Hansen J.B.,Copenhagen University |
Petersen R.K.,University of Southern Denmark |
And 13 more authors.
Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids | Year: 2010
Cold adaptation elicits a paradoxical simultaneous induction of fatty acid synthesis and β-oxidation in brown adipose tissue. We show here that cold exposure coordinately induced liver X receptor α (LXRα), adipocyte determination and differentiation-dependent factor 1 (ADD1)/sterol regulatory element-binding protein-1c (SREBP1c) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) in brown and inguinal white adipose tissues, but not in epididymal white adipose tissue. Using in vitro models of white and brown adipocytes we demonstrate that β-adrenergic stimulation induced expression of LXRα, ADD1/SREBP1c and PGC1α in cells with a brown-like adipose phenotype. We demonstrate that ADD1/SREBP1c is a powerful inducer of PGC1α expression via a conserved E box in the proximal promoter and that β-adrenergic stimulation led to recruitment of ADD1/SREBP1c to this E box. The ability of ADD1/SREBP1c to activate the PGC1α promoter exhibited a striking cell type dependency, suggesting that additional cell type-restricted factors contribute to ADD1/SREBP1c-mediated activation. In conclusion, our data demonstrate a novel role of ADD1/SREBP1c as a regulator of PGC1α expression in brown adipose tissue. © 2009 Elsevier B.V. All rights reserved. Source
Vrang N.,Rheoscience |
Meyre D.,French National Center for Scientific Research |
Froguel P.,French National Center for Scientific Research |
Froguel P.,Imperial College London |
And 15 more authors.
Obesity | Year: 2010
Using restriction fragment differential display (RFDD) technology, we have identified the imprinted gene neuronatin (Nnat) as a hypothalamic target under the influence of leptin. Nnat mRNA expression is decreased in several key appetite regulatory hypothalamic nuclei in rodents with impaired leptin signaling and during fasting conditions. Furthermore, peripheral administration of leptin to ob/ob mice normalizes hypothalamic Nnat expression. Comparative immunohistochemical analysis of human and rat hypothalami demonstrates that NNAT protein is present in anatomically equivalent nuclei, suggesting human physiological relevance of the gene product(s). A putative role of Nnat in human energy homeostasis is further emphasized by a consistent association between single nucleotide polymorphisms (SNPs) in the human Nnat gene and severe childhood and adult obesity. © 2009 The Obesity Society. Source
Fosgerau K.,Rheoscience |
Hansen T.,Steno Diabetes Center |
Albrechtsen A.,Steno Diabetes Center |
Larsen L.K.,Rheoscience |
And 3 more authors.
Journal of Endocrinology | Year: 2010
Interleukin-6 (IL6) is critically involved in inflammation and metabolism. About 1% of people produce IL6 autoantibodies (aAb-IL6) that impair IL6 signaling in vivo. We tested the hypothesis that the prevalence of such aAb-IL6 is increased in type 2 diabetic patients and that aAb-IL6 plays a direct role in causing hyperglycemia. In humans, the prevalence of circulating high-affinity neutralizing aAb-IL6 was 2.5% in the type 2 diabetic patients and 1% in the controls (odds ratio 2.5, 95% confidence interval 1.2 - 4.9, P=0.01). To test for the role of aAb-IL6 in causing hyperglycemia, such aAb-IL6 were induced in mice by a validated vaccination procedure. Mice with plasma levels of aAb-IL6 similar to the 2.5% type 2 diabetic patients developed obesity and impaired glucose tolerance (area under the curve (AUC) glucose, 2056±62 vs 1793±62, P=0.05) as compared with sham-vaccinated mice, when challenged with a high-fat diet. Mice with very high plasma levels of aAb-IL6 developed elevated fasting plasma glucose (mM, 4.8±0.4 vs 3.3±0.1, P<0.001) and impaired glucose tolerance (AUC glucose, 1340±38 vs 916±25, P<0.001) as compared with sham-control mice on normal chow. In conclusion, the prevalence of plasma aAb-IL6 at levels known to impair IL6 signaling in vivo is increased 2.5-fold in people with type 2 diabetes. In mice, matching levels of aAb-IL6 cause obesity and hyperglycemia. These data suggest that a small subset of type 2 diabetes may in part evolve from an autoimmune attack against IL6. © 2010 Society for Endocrinology. Source