Resveratrol is a plant polyphenol capable of exerting beneficial metabolic effects which are thought to be mediated in large by the activation of the NAD + -dependent protein deacetylase SIRT1. Although resveratrol has been claimed to be a bona fide SIRT1 activator using a peptide substrate (Fluor de Lys-SIRT1 peptide substrate), recent reports indicate that this finding might be an experimental artifact and need to be clarified. Here, we show that: (i) the Fluor de Lys-SIRT1 peptide is an artificial SIRT1 substrate because in the absence of the covalently linked fluorophore the peptide itself is not a substrate of the enzyme, (ii) resveratrol does not activate SIRT1 in vitro in the presence of either a p53-derived peptide substrate or acetylated PGC1a isolated from cells, and (iii) although SIRT1 deacetylates PGC-1a in both in vitro and cell-based assays, resveratrol did not activate SIRT1 under these conditions. Based on these observations, we conclude that the pharmacological effects of resveratrol in various models are unlikely to be mediated by a direct enhancement of the catalytic activity of the SIRT1 enzyme. In consequence, our data challenge the overall utility of resveratrol as a pharmacological tool to directly activate SIRT1. Key words: Fluor de Lys, resveratrol, SIRT1Abbreviations: AMPK, AMP-activated protein kinase; HPLC, high performance liquid chromatography; NAM, nicotinamide; PGC-1a, peroxisome proliferator-activated receptor-c coactivator-1a; Sir2, silence information regulator 2; SIRTs, sirtuins. Sirtuins constitute the unique family of NAD + -dependent protein deacetylases. Silent information regulator 2 (Sir2) is a sirtuin in budding yeast Saccharomyces cerevisiae and its activity mediates lifespan extension induced by calorie restriction (1). The mammalian Sir2 ortholog, SIRT1, is also induced by calorie restriction and promotes cell survival (2), triggers lipolysis and loss of fat (3), and controls glucose homeostasis (4). The biological effects of SIRT1 are mediated by its ability to deacetylate several important transcriptional factors such as Peroxisome proliferator-activated receptor-c coactivator 1alpha (PGC-1a), p53, and FOXO proteins and consequently regulate their activities (5). PGC-1a, which is activated upon deacetylation by SIRT1, plays an important role in the regulation of mitochondrial function and fatty acid oxidation (4). In contrast, p53 is inactivated once deacetylated by SIRT1 (5), suggesting that SIRT1 may protect cells from apoptosis under conditions of nutrient restriction. Taken together, these findings demonstrate that SIRT1 activity stimulates energy metabolism, improves mitochondrial function and promotes cell survival. Therefore, pharmacological activation of SIRT1 in vivo may provide a new avenue to maintain metabolic homeostasis.Molecular screening of SIRT1 activators led to the identification of plant polyphenols as SIRT1 activators, among which is resveratrol (6). The notion that resveratrol is a SIRT1 activator is consistent with two later pharmacological ...

Recombinant fibroblast growth factor (FGF)21 has antihyperglycemic, antihyperlipidemic, and antiobesity effects in diabetic rodent and monkey models. Previous studies were confined to measuring steady-state effects of FGF21 following subchronic or chronic administration. The present study focuses on the kinetics of biological actions of FGF21 following a single injection and on the associated physiological and cellular mechanisms underlying FGF21 actions. We show that FGF21 resulted in rapid decline of blood glucose levels and immediate improvement of glucose tolerance and insulin sensitivity in two animal models of insulin resistance (ob/ob and DIO mice). In ob/ob mice, FGF21 led to a 40-60% decrease in blood glucose, insulin, and amylin levels within 1 h after injection, and the maximal effects were sustained for more than 6 h despite the 1- to 2-h half-life of FGF21. In DIO mice, FGF21 reduced fasting blood glucose and insulin levels and improved glucose tolerance and insulin sensitivity within 3 h of treatment. The acute improvement of glucose metabolism was associated with a 30% reduction of hepatic glucose production and an increase in peripheral glucose turnover. FGF21 appeared to have no direct effect on ex vivo pancreatic islet insulin or glucagon secretion. However, it rapidly induced typical FGF signaling in liver and adipose tissues and in several hepatoma-derived cell lines and differentiated adipocytes. FGF21 was able to inhibit glucose release from H4IIE hepatoma cells and stimulate glucose uptake in 3T3-L1 adipocytes. We conclude that the acute glucose-lowering and insulin-sensitizing effects of FGF21 are potentially associated with its metabolic actions in liver and adipose tissues.

Glucose-dependent insulinotropic polypeptide receptor (GIPR) is associated with obesity in human genome-wide association studies. Similarly, mouse genetic studies indicate that loss of function alleles and glucose-dependent insulinotropic polypeptide overexpression both protect from high-fat diet–induced weight gain. Together, these data provide compelling evidence to develop therapies targeting GIPR for the treatment of obesity. Further, both antagonists and agonists alone prevent weight gain, but result in remarkable weight loss when codosed or molecularly combined with glucagon-like peptide-1 analogs preclinically. Here, we review the current literature on GIPR, including biology, human and mouse genetics, and pharmacology of both agonists and antagonists, discussing the similarities and differences between the 2 approaches. Despite opposite approaches being investigated preclinically and clinically, there may be viability of both agonists and antagonists for the treatment of obesity, and we expect this area to continue to evolve with new clinical data and molecular and pharmacological analyses of GIPR function.

Ghrelin is a 28-amino acid peptide secreted mainly by the stomach. Acyl-ghrelin, which binds to and activates the growth hormone secretagogue receptor type 1a (GHS-R1a), is considered to be the active form for its orexigenic effects. It has been demonstrated that peripheral administration of ghrelin stimulates food intake and adiposity in rodents and humans. Accordingly, different approaches to antagonize ghrelin/GHS-R1a signaling have been pursued for the treatment of obesity. In the present study, we generated and characterized high-affinity anti-acyl ghrelin-specific monoclonal antibodies (mAbs). In vitro, the lead mAb (33A) displayed specific binding to acyl-ghrelin, with an estimated K d value Ͻ 100 pM. In recombinant receptor cell-based assays, 33A dose-dependently inhibited the ghrelin-mediated calcium signal, with an IC 50 of ϳ3.5 nM. In vivo, ghrelin dose-dependently stimulated food intake in mice, and this effect was fully blocked by a single injection of 33A. In a 4-week chronic study, 33A was shown to effectively bind to endogenous acyl-ghrelin; however, long-term administration of 33A did not affect food intake or body weight gain in a mouse model of diet-induced obesity. Our results indicate that peripheral neutralization of ghrelin can suppress appetite stimulated by a transient surge in ghrelin levels. The lack of longterm effects on body weight control by 33A suggests that compensatory mechanisms may contribute to the regulation of energy balance.

Lu et al. show that tackling obesity with bispecific molecules that antagonize/ agonize GIPR/GLP-1R pathways decreases body weight and metabolic parameters in obese mice and monkeys. Mechanistic studies suggest that such molecules bind to GIPR and GLP-1R simultaneously and trigger receptor internalization, amplifying endosomal cAMP signaling in cells expressing both receptors.

Computed tomography (CT) as a routine follow-up has been a standard practice for patients with non-Hodgkin lymphoma although it is not recommended in most guidelines. We aimed to describe the value of surveillance CT in detection of disease relapse in patients with diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma grade 3 (FL3) and to evaluate whether relapse detected by different methods influenced outcome. In this retrospective review of consecutive 341 patients with DLBCL or FL3 diagnosed between 2003 and 2009 in complete response (CR) or unconfirmed CR, 113 patients experienced relapses. We found that routine surveillance CT detected asymptomatic relapse in 25 patients (22.1%; group 1), including 22 of 100 patients with DLBCL and three of 13 with FL3. The first presentation of relapse of the other 88 patients (group 2) included patient-reported symptoms (60.2%), physical examination (13.3%), or abnormal laboratory data (4.4%). For 72 patients received chemotherapy after relapse, the overall survival after relapse was not different between groups 1 and 2 (p = 0.569). The results of our study suggested that routine surveillance CT only has a limited role in the early detection of relapse and the relapse detected by surveillance CT or not has no impact on survival after relapse for patients with DLBCL or FL3.

considered to be important for its biological function in cholesterol effl ux ( 7,8 ). Recently, several small amphipathic peptides including 18A, 37pA, and 4F have been reported ( 9, 10 ). Although these apoA-I mimetics have been shown to promote cholesterol effl ux in cell culture systems, no evidence has demonstrated that the peptides can indeed mimic apoA-I to form HDL particles. One of the peptides, D4F, synthesized with D-amino acids has been shown to reduce atherosclerosis in apoE-null mice ( 11,12 ). In these studies, D4F increased pre-␤ HDL level. However, direct formation of HDL-like particles by D4F was not demonstrated. Moreover, in these studies HDL particles were identifi ed using anti-apoA-I antibody for detection; there was no evidence that the 4F peptide was defi nitively within the HDL particles. One of the diffi culties in demonstrating that these peptide mimetics directly form HDL particles is the lack of detection antibodies against these peptides. Although Wool et al. ( 13 ) and Meriwether et al. ( 14 ) attempted to use biotinylation of 4F peptide and [ 14 C]4F, respectively, to track the profi le of peptide/lipoprotein association, no direct evidence is available to show that the peptide and apoA-I are in the same HDL particle.In this study, we generated a peptibody by fusing 4F peptide to the Fc fragment of mouse IgG (mFc-2X4F). The rationale of using Fc is to generate a multivalent structure containing multiple amphipathic helices to examine whether multiple helices are superior for effl ux compared with a monomeric helix. We also studied whether the peptibody is capable of forming HDL-like particle, inasmuch as apoA-I also contains multiple helices. Moreover, using an antibody against mouse Fc (mFc) as detection antibody, we were able to determine and track the size and distribution of HDL-like particles generated by mFc-2X4F in vitro and in vivo. HDL has been identifi ed as a potential target for the treatment of atherosclerotic vascular disease. Nascent HDL is formed by the interaction of apoA-I and ABCA1, which triggers the cholesterol and phospholipid effl ux from cells, the fi rst step of reverse cholesterol transport ( 1, 2 ). ApoA-I has also been shown in animal models and humans to have the therapeutic potential of reversing atherosclerosis ( 3-5 ). ApoA-I is a 243 amino acid protein with amphipathic ␣ -helices ( 6 ).

Glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) is associated with obesity in human genome-wide association studies (GWAS). Similarly, mouse genetic studies indicate that loss of function alleles and GIP overexpression both protect from high-fat diet (HFD)-induced weight gain. Together, these data provide compelling evidence to develop therapies targeting GIPR for the treatment of obesity. Further, both antagonists and agonists alone prevent weight gain, but result in remarkable weight loss when co-dosed or molecularly combined with glucagon-like peptide-1 (GLP-1) analogs preclinically. Here, we review the current literature on GIPR, including biology, human and mouse genetics, and pharmacology of both agonists and antagonists, discussing the similarities and differences between the two approaches. Despite opposite approaches being investigated preclinically and clinically, there may be viability of both agonists and antagonists for the treatment of obesity and we expect this area to continue to evolve with new clinical data and molecular and pharmacological analyses of GIPR function.