Objective: Human obesity is closely associated with a state of chronic low-grade inflammation, which also involves the adipose tissue with enhanced production of bioactive substances (adipokines). Calorie restriction (CR) reduces adipocytokine production and improves metabolic profile in rodents. Some of these effects are mediated through activation of the sirtuin 1 (Sirt1) enzyme, and in this study, we investigate whether the natural phytoalexin, resveratrol (RSV), which is a potent Sirt1 activator, has anti-inflammatory effects in human adipose tissue explants. Design: The effect of RSV on interleukin 1b (IL1b)-induced change of adipokine mRNA gene expression and secretion were measured in human adipose tissue explants. Results: Exposure of human adipose tissue in vitro to IL1b for 24 h increased secretion of the proinflammatory adipokines IL6, IL8 and monocyte chemoattractant protein 1 (MCP-1) 3-7.7-fold (Po0.05) and increased IL6, IL8, MCP-1, IL1b and PAI-1 mRNA expression 1.3-7.2-fold (Po0.05) accordingly. Concomitant incubations with RSV reversed the IL1b-stimulated secretion (16-36%) and gene expression (25-48%) of these adipokines. IL1b reduced adiponectin mRNA expression (40%), a decrement that was reversed by RSV treatment. Similar effects were observed in differentiated human preadipocytes in primary culture, indicating that human adipocytes are a potential target for RSV effects. Finally, the effects were neutralized by sirtinol, a Sirt1 inhibitor. Conclusion: This study is the first to show anti-inflammatory effects of RSV on adipokine expression and secretion in human adipose tissue in vitro through the SIRT1 pathway. Thus, RSV is hypothesized to possess beneficial effects and might improve the metabolic profile in human 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.

Background:High levels of free fatty acids (FFA) have been suggested to be one of the underlying mechanisms for adipose tissue (AT) inflammation and dysfunction in obesity. Human AT produces several adipokines including monocyte chemoattractant protein-1 (MCP-1), which are involved in the pathogenesis of obesity-mediated inflammation.Objective:In this study, we investigated the effects of lipopolysaccharide (LPS) and a panel of dietary FFA on MCP-1 gene and protein expression in adipocytes and macrophages. Furthermore, we investigated whether the effect of LPS and FFA were mediated through the toll-like receptor 4 (TLR4).Methods:3T3-L1 adipocytes and THP-1 macrophages were incubated for 24 h with the following FFA: monounsaturated fatty acid (oleic acid), saturated fatty acid (palmitic acid) and trans fatty acid (elaidic acid; 500 μM) with and without LPS (2 ng ml−1), and MCP-1 and TLR4 mRNA expression and MCP-1 protein secretion was determined.Results:The results showed that LPS significantly increased MCP-1 and TLR4 expression and MCP-1 secretion in 3T3-L1 adipocytes, and that the MCP-1 expression was blocked by a TLR4 inhibitor (CLI095). The effects of the various FFA on MCP-1 mRNA expression and protein secretion in the adipocytes showed no significant changes either alone or in combination with LPS. In macrophages, palmitic acid increased MCP-1 mRNA expression by 1.8-fold (P<0.05), but oleic acid and elaidic acid had no effects.Conclusions:In conclusion, in 3T3-L1 adipocyte, the TLR4-agonist, LPS, stimulates the proinflammatory chemokine MCP-1. The different classes of FFA did not induce MCP-1 mRNA expression or protein secretion in the adipocytes, but the saturated FFA, palmitic acid, induced MCP-1 mRNA expression in macrophages, possibly because of the higher expression level of TLR4 in the macrophages than the adipocytes. Our results indicate that FFA may induce AT inflammation through proinflammatory stimulation of macrophages.

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-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.The gastrointestinal peptide hormone ghrelin is an important regulator of appetite, energy expenditure, and acute growth hormone secretion through interaction with the ghrelin receptors located mainly in the central nervous system (Tschöp et al., 2000). From a drug discovery point of view, these functions of ghrelin qualify ghrelin receptor agonists as anabolic compounds with potentials for treatment of, for example, cachexia.The initial agonists synthesized for the ghrelin receptor were peptides, sharing common structural features, including a central hydrophobic motif and a positive charge in the amidated C-terminal end. Despite relatively poor bioavailability and low therapeutic index/window, these peptides efficiently induced GH secretion in vitro as well as in vivo both in animal and human models (Bowers et al., 1984). GHRP-6 is a prototype for these peptides (Fig. 1). In an attempt to increase oral bioavailability, a series of nonpeptide compounds was subsequently developed. They were