Adrenal glucocorticoids regulate adipsin gene expression in genetically obese mice

Adipsin expression at the protein and mRNA levels is greatly reduced in several distinct syndromes of obesity in the mouse: genetic obesity due to the db/db and ob/ob genes, and a chemically induced model secondary to neonatal exposure to monosodium glutamate. We considered first the possibility that the adipsin gene might be identical to the db or ob locus and the lowered expression of this protein might result from a mutation in this gene. We show here that the adipsin structural gene is located on chromosome 10 and hence is physically distinct from any obesity genes so far identified in the mouse. A major role for the adrenal gland and adrenal glucocorticoids in the aberrant regulation of adipsin in these models of obesity is indicated by several experiments. Adrenalectomy of the ob/ob mouse raises the circulating levels of adipsin protein and the amount of this mRNA in epididymal fat pads (5-fold), although neither is increased to the levels seen in lean controls. Exogenous administration of corticosterone completely blocks the effects of adrenalectomy on adipsin, suggesting that the effect of this endocrine ablation is through reduction of adrenal glucocorticoids. Corticosterone administration also causes suppression in the levels of adipsin mRNA and protein in lean mice, although this decrease is never as severe as that seen in obese mice. The effect of exogenous corticosterone in lean mice occurs within 2 days and hence is not secondary to the obesity which these hormones eventually elicit. These results indicate that glucocorticoids can regulate adipsin expression in vivo and strongly suggest that the hyperglucocorticoid state seen in certain obese models plays a significant role in lowering adipsin mRNA and protein levels. Quantitative analysis of these experiments suggests that other as yet unknown neuroendocrine factors also function to suppress adipsin in obesity.     

beta-Internexin, a ubiquitous intermediate filament-associated protein

In this article we show a Triton-insoluble, intermediate filament-associated protein of approximately 70 kD to be expressed ubiquitously in diverse mammalian cell types. This protein, assigned the name beta-internexin, exhibits extreme homology in each of the various cell lines as demonstrated by identical limited peptide maps, similar mobilities on two-dimensional gels, and detection in Triton-soluble and -insoluble extracts. beta-Internexin also shares some degree of homology with alpha-internexin, an intermediate filament-associated protein isolated and purified from rat spinal cord, which accounts for the immunologic cross-reactivity displayed by these polypeptides. Light microscopic immunolocalization of beta-internexin with a monoclonal antibody (mAb-IN30) reveals it to be closely associated with the vimentin network in fibroblasts. The antigen is also observed to collapse with the vimentin reticulum during the formation of a juxtanuclear cap induced by colchicine treatment. Ultrastructural localization, using colloidal gold, substantiates the affinity of beta-internexin for cytoplasmic filaments and, in addition, demonstrates its apparent exclusion from the intranuclear filament network. We examine also the resemblance of beta-internexin to a microtubule-associated polypeptide and the constitutively synthesized mammalian heat shock protein (HSP 68/70).     

Excision dynamics of <Emphasis Type="Italic">Vibrio</Emphasis> pathogenicity island-2 from <Emphasis Type="Italic">Vibrio cholerae:</Emphasis> role of a recombination directionality factor VefA

Background  

Vibrio Pathogenicity Island-2 (VPI-2) is a 57 kb region present in choleragenic V. cholerae isolates that is required for growth on sialic acid as a sole carbon source. V. cholerae non-O1/O139 pathogenic strains also contain VPI-2, which in addition to sialic acid catabolism genes also encodes a type 3 secretion system in these strains. VPI-2 integrates into chromosome 1 at a tRNA-serine site and encodes an integrase intV2 (VC1758) that belongs to the tyrosine recombinase family. IntV2 is required for VPI-2 excision from chromosome 1, which occurs at very low levels, and formation of a non-replicative circular intermediate.     

Novel Gut-Based Pharmacology of Metformin in Patients with Type 2 Diabetes Mellitus

Metformin, a biguanide derivate, has pleiotropic effects beyond glucose reduction, including improvement of lipid profiles and lowering microvascular and macrovascular complications associated with type 2 diabetes mellitus (T2DM). These effects have been ascribed to adenosine monophosphate-activated protein kinase (AMPK) activation in the liver and skeletal muscle. However, metformin effects are not attenuated when AMPK is knocked out and intravenous metformin is less effective than oral medication, raising the possibility of important gut pharmacology. We hypothesized that the pharmacology of metformin includes alteration of bile acid recirculation and gut microbiota resulting in enhanced enteroendocrine hormone secretion. In this study we evaluated T2DM subjects on and off metformin monotherapy to characterize the gut-based mechanisms of metformin. Subjects were studied at 4 time points: (i) at baseline on metformin, (ii) 7 days after stopping metformin, (iii) when fasting blood glucose (FBG) had risen by 25% after stopping metformin, and (iv) when FBG returned to baseline levels after restarting the metformin. At these timepoints we profiled glucose, insulin, gut hormones (glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY) and glucose-dependent insulinotropic peptide (GIP) and bile acids in blood, as well as duodenal and faecal bile acids and gut microbiota. We found that metformin withdrawal was associated with a reduction of active and total GLP-1 and elevation of serum bile acids, especially cholic acid and its conjugates. These effects reversed when metformin was restarted. Effects on circulating PYY were more modest, while GIP changes were negligible. Microbiota abundance of the phylum Firmicutes was positively correlated with changes in cholic acid and conjugates, while Bacteroidetes abundance was negatively correlated. Firmicutes and Bacteroidetes representation were also correlated with levels of serum PYY. Our study suggests that metformin has complex effects due to gut-based pharmacology which might provide insights into novel therapeutic approaches to treat T2DM and associated metabolic diseases.

Trial Registration:

www.ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01357876","term_id":"NCT01357876"}}NCT01357876     

Pivaloylcodeine,a new codeine derivative,for the inhibition of morphine glucuronidation. An in vitro study in the rat

We have previously found that phenanthrenic opioids, including codeine, modulate morphine glucuronidation in the rat. Here codeine and five of its derivatives were compared in their effects on the synthesis of morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) from morphine by rat liver microsomal preparations, and by primary cultures of rat hepatocytes previously incubated for 72 h with either codeine or its derivatives. Acetylcodeine and pivaloylcodeine shared the capability of the parent compound of inhibiting the synthesis of M3G by liver microsomes through a noncompetitive mechanism of action. Their IC₅₀ were 3.25, 2.27, and 4.32 μM, respectively. Dihydrocodeine, acetyldihydrocodeine, and lauroylcodeine were ineffective. In all the experimental circumstances M6G was undetectable in the incubation medium. In primary hepatocyte cultures codeine only inhibited M3G formation, but with a lower efficacy than that observed with microsomes (IC₅₀ 20.91 vs 4.32 μM). Preliminary results show that at micromolar concentrations codeine derivatives exhibit a low rate of affinity for μ opiate receptors. In conclusion, acetyl and pivaloyl derivatives of codeine noncompetitively inhibit liver glucuronidation of morphine interacting with microsomes. This study further strengths the notion that phenanthrenic opioids can modulate morphine glucuronidation independently from their effects on μ opiate receptors.     

Recombinant protein purification by self-cleaving aggregation tag

A simple technique is presented for non-chromatographic purification of recombinant proteins expressed in Escherichia coli. This method is based on a reversibly precipitating, self-cleaving purification tag. The tag is made up of two components: an elastin-like polypeptide (ELP), which reversibly self-associates in high-salt buffers at temperatures above 30 degrees C; and an intein, which causes the ELP tag to self-cleave in response to a mild pH shift. Thus, a tripartite ELP-intein-target protein precursor can be purified by cycles of salt addition, heating and centrifugation. Once purified, intein-mediated self-cleavage, followed by precipitation of the cleaved ELP tag, allows easy and effective isolation of the pure, native target protein without the need for chromatographic separations. Recoveries of 50-100 mg of cleaved, native target protein per liter of shake-flask culture have been achieved for over a dozen proteins, typically in 8-24 h depending on specific process parameters.     

HIV-1 Tat regulates endothelial cell cycle progression via activation of the Ras/ERK MAPK signaling pathway

Tat, the transactivator of HIV-1 gene expression, is released by acutely HIV-1-infected T-cells and promotes adhesion, migration, and growth of inflammatory cytokine-activated endothelial and Kaposi's sarcoma cells. It has been previously demonstrated that these effects of Tat are due to its ability to bind through its arginine-glycine-aspartic (RGD) region to the alpha5beta1 and alphavbeta3 integrins. However, the signaling pathways linking Tat to the regulation of cellular functions are incompletely understood. Here, we report that Tat ligation on human endothelial cells results in the activation of the small GTPases Ras and Rac and the mitogen-activated protein kinase ERK, specifically through its RGD region. In addition, we demonstrated that Tat activation of Ras, but not of Rac, induces ERK phosphorylation. We also found that the receptor proximal events accompanying Tat-induced Ras activation are mediated by tyrosine phosphorylation of Shc and recruitment of Grb2. Moreover, Tat enabled endothelial cells to progress through the G1 phase in response to bFGF, and the process is linked to ERK activation. Taken together, these data provide novel evidence about the ability of Tat to activate the Ras-ERK cascade which may be relevant for endothelial cell proliferation and for Kaposi's sarcoma progression.     

Synthesis of structurally simplified analogues of aplidinone A,a pro-apoptotic marine thiazinoquinone

The synthesis of analogues of aplidinone A (7), a prenylated quinone isolated from the Mediterranean ascidian Aplidium conicum, has been performed. This work not only allowed confirming the structural assignment of aplidinone A, previously made with the support of GIAO shielding calculations, but, above all, made a series of structurally related quinone derivatives (compounds 8–13 and the natural metabolite) available for a screening in vitro for cytotoxic and pro-apoptotic activity and for SAR studies. The study evidenced one of the synthetic analogues (11) as a potent cytotoxic and pro-apoptotic agent against several tumor cell lines which also inhibits the TNFα-induced NF-κB activation in a human leukemia T cell line. This exemplifies the potential of a natural product to qualify as lead structure for medicinal chemistry campaigns, affording simplified analogues with better bioactivity and easier to synthesize.