Resveratrol has inhibitory effects on the hypoxia-induced inflammation and angiogenesis in human adipose tissue in vitro.

Hypoxia modulates the production of proteins involved in e.g. inflammation, angiogenesis and glucose utilization and hypoxia may therefore be an important factor underlying adipose tissue dysfunction in obesity. Resveratrol (RSV) is a natural polyphenolic compound and has been shown to have powerful anti-inflammatory effects and beneficial effects on several obesity-related complications. Thus, in the present study we investigated whether RSV has effects on hypoxic markers (GLUT-1, VEGF), hypoxia-induced key markers of inflammation (IL8, IL6), and leptin in human adipose tissue in vitro. Hypoxia was induced by incubating human adipose tissue fragments with 1% O2 for 24h as compared to 21% O2 The gene expressions were investigated by RT-PCR and protein release by Elisa. Hypoxia increases the expression of glucose transporter-1 (GLUT-1) (19-fold, p<0.001), vascular endothelial growth factor (VEGF) (10-fold, p<0.05), interleukin-8 (IL8) (8-fold, p<0.05), interleukin-6 (IL6) (5-fold, p<0.05) and leptin (9-fold). The protein levels of VEGF released to the medium was increased (8-fold, p<0.01) by hypoxia. RSV dose-dependently inhibited several of these hypoxia-induced expressions and at a concentration of 50 µM RSV almost completely inhibited the hypoxic responses at the above mentioned gene expression levels (p<0.05-p<0.001) and significantly attenuated the hypoxia-induced protein releases by 50-60%. These results demonstrate that hypoxia induces extensive changes in human adipose tissue in the expression and release of inflammation and angiogenesis-related adipokines. In addition the inhibition of hypoxia-mediated inflammation and angiogenesis might represent a novel mechanism of RSV in preventing obesity-related pathologies.

The imprinted gene neuronatin is regulated by metabolic status and associated with obesity.

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.

Overlapping binding site for the endogenous agonist, small-molecule agonists, and ago-allosteric modulators on the ghrelin receptor.

A library of robust ghrelin receptor mutants with single substitutions at 22 positions in the main ligand-binding pocket was employed to map binding sites for six different agonists: two peptides (the 28-amino-acid octanoylated endogenous ligand ghrelin and the hexapeptide growth hormone secretagogue GHRP-6) plus four nonpeptide agonists-the original benzolactam L-692,429 [3-amino-3-methyl-N-(2,3,4,5-tetrahydro-2-oxo-1-([2'-(1H-tetrazol-5-yl) (1,1'-biphenyl)-4-yl]methyl)-1H-1-benzazepin-3(R)-yl)-butanamide], the spiroindoline sulfonamide MK-677 [N-[1(R)-1, 2-dihydro-1-ethanesulfonylspiro-3H-indole-3,4'-piperidin)-1'-yl]carbonyl-2-(phenylmethoxy)-ethyl-2-amino-2-methylpropanamide], and two novel oxindole derivatives, SM-130686 [(+)-6-carbamoyl-3-(2-chlorophenyl)-(2-diethylaminoethyl)-4-trifluoromethyloxindole] and SM-157740 [(+/-)-6-carbamoyl-3-(2, 4-dichlorophenyl)-(2-diethylaminoethyl)-4-trifluoromethyloxindole)]. The strongest mutational effect with respect to decrease in potency for stimulation of inositol phosphate turnover was for all six agonists the GluIII:09-to-Gln substitution in the extracellular segment of TM-III. Likewise, all six agonists were affected by substitutions of PheVI:16, ArgVI:20, and PheVI:23 on the opposing face of transmembrane domain (TM) VI. Each of the agonists was also affected selectively by specific mutations. The mutational map of the ability of L-692,429 and GHRP-6 to act as allosteric modulators by increasing ghrelin's maximal efficacy overlapped with the common mutational map for agonism but it was not identical with the map for the agonist property of these small-molecule ligands. In molecular models, built over the inactive conformation of rhodopsin, low energy conformations of the nonpeptide agonists could be docked to satisfy many of their mutational hits. It is concluded that although each of the ligands in addition exploits other parts of the receptor, a large, common binding site for both small-molecule agonists--including ago-allosteric modulators--and the endogenous agonist is found on the opposing faces of TM-III and -VI of the ghrelin receptor.