The peroxisome proliferator-activated receptors (PPARs) are dietary lipid sensors that regulate fatty acid and carbohydrate metabolism. The hypolipidemic effects of fibrate drugs and the therapeutic benefits of the thiazolidinedione drugs are due to their activation of PPAR␣ and -␥, respectively. In this study, isohumulones, the bitter compounds derived from hops that are present in beer, were found to activate PPAR␣ and -␥ in transient co-transfection studies. Among the three major isohumulone homologs, isohumulone and isocohumulone were found to activate PPAR␣ and -␥. Diabetic KK-A y mice that were treated with isohumulones (isohumulone and isocohumulone) showed reduced plasma glucose, triglyceride, and free fatty acid levels (65.3, 62.6, and 73.1%, respectively, for isohumulone); similar reductions were found following treatment with the thiazolidinedione drug, pioglitazone. Isohumulone treatment did not result in significant body weight gain, although pioglitazone treatment did increase body weight (10.6% increase versus control group). C57BL/6N mice fed a high fat diet that were treated with isohumulones showed improved glucose tolerance and reduced insulin resistance. Furthermore, these animals showed increased liver fatty acid oxidation and a decrease in size and an increase in apoptosis of their hypertrophic adipocytes. A double-blind, placebo-controlled pilot study for studying the effect of isohumulones on diabetes suggested that isohumulones significantly decreased blood glucose and hemoglobin A1c levels after 8 weeks (by 10.1 and 6.4%, respectively, versus week 0). These results suggest that isohumulones can improve insulin sensitivity in high fat diet-fed mice with insulin resistance and in patients with type 2 diabetes.

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The simian virus 40 capsid is composed of 72 pentamers of VP1 protein. Although the capsid is known to dissociate to pentamers in vitro following simultaneous treatment with reducing and chelating agents, the functional roles of disulfide linkage and calcium ion-mediated interactions are not clear. To elucidate the roles of these interactions, we introduced amino acid substitutions in VP1 at cysteine residues and at residues involved in calcium binding. We expressed the mutant proteins in a baculovirus system and analyzed both their assembly into virus-like particles (VLPs) in insect cells and the disassembly of those VLPs in vitro. We found that disulfide linkages at both Cys-9 and Cys-104 conferred resistance to proteinase K digestion on VLPs, although neither linkage was essential for the formation of VLPs in insect cells. In particular, reduction of the disulfide linkage at Cys-9 was found to be critical for VLP dissociation to VP1 pentamers in the absence of calcium ions, indicating that disulfide linkage at Cys-9 prevents VLP dissociation, probably by increasing the stability of calcium ion binding. We found that amino acid substitutions at carboxy-terminal calcium ion binding sites (Glu-329, Glu-330, and Asp-345) resulted in the frequent formation of unusual tubular particles as well as VLPs in insect cells, indicating that these residues affect the accuracy of capsid assembly. In addition, unexpectedly, amino acid substitutions at any of the calcium ion binding sites tested, especially at Glu-157, resulted in increased stability of VLPs in the absence of calcium ions in vitro. These results suggest that appropriate affinities of calcium ion binding are responsible for both assembly and disassembly of the capsid.Simian virus 40 (SV40), a member of the Papovaviridae, is a small, nonenveloped tumorigenic virus. Its genome consists of double-stranded circular DNA of 5,243 bp, which encodes three structural proteins (VP1, VP2, and VP3) and two nonstructural proteins (large T antigen and small T antigen). The structural proteins are expressed in late infection, and viral capsids are formed in the nucleus of infected susceptible host cells (32). The SV40 capsid is about 45 to 50 nm in diameter, and its major component is VP1. The capsid is formed by the arrangement of 72 VP1 pentamers in a Tϭ7d icosahedral lattice. The three-dimensional structure of the SV40 virion has been elucidated by X-ray crystallography, which showed that the capsid is formed from three nonequivalent types of interactions between pentameric capsomeres (␣-␣Ј, ␤-␤Ј, and ␥-␥) (20, 30).SV40 capsids, as well as those of the closely related murine polyomavirus, dissociate to VP1 pentamers following treatment with dithiothreitol (DTT) and EGTA in vitro (2-4, 7), indicating that disulfide linkage and calcium ion-mediated interactions between pentamers are important for capsid formation in these viruses. Consistent with these observations, crystallographic analysis of SV40 virions has identified disulfide linkage between Cys-104 and Cys-104 in ␤-␤...

Nelumbo nucifera Gaertn. (Nymphaceae) has been used for various medicinal purposes as in Chinese herbal medicine. In particular, the leaves are known for diuretic and astringent properties, and are used to treat obesity. During our search for a plant-derived anti-obesity agent from natural products, we have found that a 50% ethanol (EtOH) extract prepared from the leaves of N. nucifera (NN) stimulated lipolysis in the white adipose tissue (WAT) of mice and that the beta-adrenergic receptor (beta-AR) pathway was involved in this effect. In subsequent experiments, dietary supplementation of NN resulted in a significant suppression of body weight gain in A/J mice fed a high-fat diet. Bioassay-guided fractionation and repeated chromatography of NN has led to the isolation and identification of quercetin 3-O-alpha-arabinopyranosyl-(1-->2)-beta-galactopyranoside (1), rutin (2), (+)-catechin (3), hyperoside (4), isoquercitrin (5), quercetin (6) and astragalin (7). Of these, compounds 1, 3, 4, 5 and 7 exhibited lipolytic activity, especially in visceral adipose tissue. Our results indicate that the effects of NN in preventing diet-induced obesity appear to be due to various flavonoids and that the activation of beta-AR pathway was involved, at least in part.

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OBJECTIVE: Isomerized hop extract (IHE), which consists mainly of isohumulones and is required in the beer brewing process, was investigated for its effects on diet-induced obesity in two strains of mice. DESIGN: C57BL/6N and KK-A y mice were fed a standard or high-fat diet containing IHE and their body and tissue weights were measured at various time points. Oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were carried out in high-fat diet-fed C57BL/6N mice. The effects of IHE on intestinal lipid absorption were examined in Wistar rats using a plasma triacylglycerol assay after oral administration of a lipid emulsion. Fecal lipid levels were also measured in these animals after they were fed a high-fat diet containing IHE for 15 days. The effects of IHE on pancreatic lipase activity and the expression of genes involved in hepatic lipid metabolism were also examined using an in vitro assay and quantitative RT-PCR, respectively. RESULTS: Supplementation of high-fat-containing chow with IHE reduced body weight gain and improved glucose tolerance in our experimental mice. A reduction in body weight gain was also observed in C57BL/6N mice fed a standard diet containing IHE. Wistar rats fed a high-fat diet containing IHE showed reduced plasma triacylglycerol levels and an increase in their fecal lipid excretion. Similarly, their pancreatic lipase activity was inhibited and their elevation in plasma triacylglycerol levels seen after the oral administration of lipid emulsion was significantly suppressed. IHE-fed mice showed an increased expression in their lipid oxidation genes and a decreased expression in genes involved in triacylglycerol biosynthesis. CONCLUSION: The inhibition of intestinal dietary fat absorption may be the mechanism by which IHE induces its weightlowering effects in high-fat diet-fed mice. The modulatory effect of IHE on lipid metabolism may also, at least partly, be responsible for its beneficial effects on body weight gain. These results suggest that IHE may be helpful in humans in preventing diet-induced obesity and perhaps even metabolic syndrome, the latter of which is known to be associated with obesity.

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