High-Fat Diet Triggers Inflammation-Induced Cleavage of SIRT1 in Adipose Tissue To Promote Metabolic Dysfunction

Adipose tissue plays an important role in storing excess nutrients and preventing ectopic lipid accumulation in other organs. Obesity leads to excess lipid storage in adipocytes, resulting in the generation of stress signals and the derangement of metabolic functions. SIRT1 is an important regulatory sensor of nutrient availability in many metabolic tissues. Here we report that SIRT1 functions in adipose tissue to protect from inflammation and obesity under normal feeding conditions, and to forestall the progression to metabolic dysfunction under dietary stress and aging. Genetic ablation of SIRT1 in adipose tissue leads to gene expression changes that highly overlap with changes induced by high-fat diet in wild-type mice, suggesting that dietary stress signals inhibit the activity of SIRT1. Indeed, we show that high-fat diet induces the cleavage of SIRT1 protein in adipose tissue by the inflammation-activated caspase-1, providing a link between dietary stress and predisposition to metabolic dysfunction.     

Epigenetic Activity of Peroxisome Proliferator-Activated Receptor Gamma Agonists Increases the Anticancer Effect of Histone Deacetylase Inhibitors on Multiple Myeloma Cells

Epigenetic modifications play a major role in the development of multiple myeloma. We have previously reported that the PPARγ agonist pioglitazone (PIO) enhances, in-vitro, the cytotoxic effect of the Histone deacetylase inhibitor (HDACi), valproic acid (VPA), on multiple myeloma cells. Here, we described the development of a new multiple myeloma mouse model using MOLP8 cells, in order to evaluate the effect of VPA/PIO combination on the progression of myeloma cells, by analyzing the proliferation of bone marrow plasma cells. We showed that VPA/PIO delays the progression of the disease and the invasion of myeloma cells in the bone marrow. Mechanistically, we demonstrated that VPA/PIO increases the cleavage of caspase 3 and PARP, and induces the acetylation of Histone 3 (H3). Furthermore, we provided evidence that PPARγ agonist is able to enhance the action of other HDACi such as Vorinostat or Mocetinostat. Using PPARγ antagonist or siPPARγ, we strongly suggest that, as described during adipogenesis, PIO behaves as an epigenetic regulator by improving the activity of HDACi. This study highlights the therapeutic benefit of PIO/VPA combination, compared to VPA treatment as a single-arm therapy on multiple myeloma and further highlights that such combination may constitute a new promising treatment strategy which should be supported by clinical trials.     

Synthesis of carba vasopressin analogues by solid-phase cyclization

A method is described for the solid-phase cyclization of analogues of arginine vasopressin (AVP) in which one of the sulfur atoms of the disulfide bridge is formally replaced by a methylene group and in which the terminal amino group is formally replaced by a hydrogen atom. The linear precursors of these vasopressin analogues were assembled by a standard Merrifield solid-phase procedure and were cyclized by intramolecular peptide bond formation while the peptide was still attached to the resin support; then the final products were simultaneously deprotected and released from the polymeric support by treatment with liquid hydrogen fluoride. The products of this synthetic procedure were isolated by chromatography and exhibited high biological activities. This method for cyclization of resin-bound peptide is being applied in the synthesis of many other cyclopeptides for conformation and biological studies.     

The internal sequence of the peptide-substrate determines its N-terminus trimming by ERAP1

Background

Endoplasmic reticulum aminopeptidase 1 (ERAP1) trims N-terminally extended antigenic peptide precursors down to mature antigenic peptides for presentation by major histocompatibility complex (MHC) class I molecules. ERAP1 has unique properties for an aminopeptidase being able to trim peptides in vitro based on their length and the nature of their C-termini.

Methodology/Principal Findings

In an effort to better understand the molecular mechanism that ERAP1 uses to trim peptides, we systematically analyzed the enzyme''s substrate preferences using collections of peptide substrates. We discovered strong internal sequence preferences of peptide N-terminus trimming by ERAP1. Preferences were only found for positively charged or hydrophobic residues resulting to trimming rate changes by up to 100 fold for single residue substitutions and more than 40,000 fold for multiple residue substitutions for peptides with identical N-termini. Molecular modelling of ERAP1 revealed a large internal cavity that carries a strong negative electrostatic potential and is large enough to accommodate peptides adjacent to the enzyme''s active site. This model can readily account for the strong preference for positively charged side chains.

Conclusions/Significance

To our knowledge no other aminopeptidase has been described to have such strong preferences for internal residues so distal to the N-terminus. Overall, our findings indicate that the internal sequence of the peptide can affect its trimming by ERAP1 as much as the peptide''s length and C-terminus. We therefore propose that ERAP1 recognizes the full length of its peptide-substrate and not just the N- and C- termini. It is possible that ERAP1 trimming preferences influence the rate of generation and the composition of antigenic peptides in vivo.     

Pathogenic potential of environmental Klebsiella pneumoniae isolates

Klebsiella pneumoniae is an important opportunistic pathogen and a frequent cause of nosocomial infections. K. pneumoniae infections can occur at nearly any body site; however, urinary tract infections and infections of the respiratory tract predominate. Infections are frequently preceded by gastrointestinal colonization, and the gastrointestinal tract is believed to be the most important reservoir for transmission of the bacteria. In contrast to many other bacterial pathogens, K. pneumoniae is ubiquitous in nature. Several studies have described Klebsiella isolates of environmental origin to be nearly identical to clinical isolates with respect to several phenotypic properties. However, the pathogenic potential of environmental K. pneumoniae isolates is essentially unknown. We have evaluated the virulence of K. pneumoniae strains of environmental and clinical origin directly in animal models, i.e. in urinary tract infection and intestinal colonization models. Furthermore, the ability to adhere to and invade human epithelial cell lines was examined. Although strain-to-strain differences were observed in the individual infection models, overall, strains of environmental origin were found to be as virulent as strains of clinical origin. The ubiquity of K. pneumoniae in nature and the general ability of K. pneumoniae strains to infect susceptible hosts might explain the high frequency of opportunistic infections caused by this species.     

Synthesis and pharmacological evaluation of amide conjugates of NSAIDs with L-cysteine ethyl ester, combining potent antiinflammatory and antioxidant properties with significantly reduced gastrointestinal toxicity

The synthesis and pharmacological evaluation of a series of amide derivatives of NSAIDs with L-cysteine ethyl ester is described. The novel derivatives are potent antiinflammatory, antioxidant and hypocholesterolemic-hypolipidemic agents, while they demonstrate considerably reduced gastrointestinal toxicity. This molecular modification may offer a general route to safer antiinflammatory agents, potentially suitable for chronic use in conditions such as neurodegenerative disorders.     

Age-related differentiations of Th1/Th2 cytokines in newborn infants

OBJECTIVE: To evaluate age-related differentiation of immune response in newborns by measuring serum concentrations of interleukin-2 (IL-2), interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) during the perinatal period. SUBJECTS AND METHODS: Fifty-seven healthy term neonates, their mothers and 25 healthy adults (controls) age-matched to the mothers were included in the study. Cytokine concentrations were measured in the umbilical cord (UC), and in first-day (1N) and fifth-day (5N) neonatal samples, compared with those in maternal serum (MS) and control serum samples. RESULTS: Serum IL-2 concentrations in the UC were markedly elevated compared with those in MS and controls (p < 0.0001), decreasing significantly thereafter up to 5N (p < 0.001). IL-4 serum concentrations did not differ significantly between the UC, 1N and 5N samples; they were, however, markedly elevated compared with those in MS (p < 0.001, p < 0.0007 and p < 0.0001, respectively) and controls (p < 0.05, p < 0.01 and p < 0.006, respectively). IFN-gamma serum concentrations were significantly lower in the UC compared with those in controls (p < 0.04), increasing significantly up to 5N (p < 0.03). Both IFN-gamma/IL-2 and IFN-gamma/IL-4 ratios increased significantly in 5N, compared with those in the UC (p < 0.001 and p < 0.03). CONCLUSION: Our findings indicate a differential cytokine balance at birth with enhanced expression of IL-2 and IL-4 against IFN-gamma. However, a regularization of immune response seems to proceed quickly during the early neonatal life.