Attenuation of diet-induced obesity and induction of white fat browning with a chemical inhibitor of histone deacetylases.

BACKGROUND/OBJECTIVES: In the last decade, a strict link between epigenetics and metabolism has been demonstrated. Histone deacetylases (HDACs) have emerged as key epigenetic regulators involved in metabolic homeostasis in normal and pathologic conditions. Here we investigated the effect of the class I HDAC inhibitor MS-275 in a model of obesity induced by a high-fat diet (HFD). METHODS: C57BL6/J male mice were fed HFD for 17 weeks and then randomized in two groups, treated intraperitoneally with vehicle dimethylsulfoxide (DMSO) or with the class I selective HDAC inhibitor MS-275 every other day for 22 days. Glucose tolerance test and measurement of body temperature during cold exposure were performed. Adipose tissues and liver were phenotypically characterized through histological analysis. Gene and protein expression analysis of brown and white adipose tissues (WATs) were performed. RESULTS: MS-275 treated mice showed 10% reduction of body weight, lower adipocyte size and improved glucose tolerance. Inhibition of class I HDAC determined reduction of adipocyte size and of fat mass, paralleled by higher expression of adipose functionality markers and by increased rate of lipolysis and fatty acid ß-oxidation. MS-275 also promoted thermogenic capacity, related to 'browning' of visceral and subcutaneous WAT, showing increased expression of uncoupling protein 1. In brown adipose tissue, we observed limited effects on gene expression and only reduction of brown adipocyte size. CONCLUSIONS: This study provides evidence that class I HDAC inhibition stimulated functionality and oxidative potential of adipose tissue, improving glucose tolerance and ameliorating the metabolic profile in diet-induced obese mice.

Densovirus crosses the insect midgut by transcytosis and disturbs the epithelial barrier function.

Densoviruses are parvoviruses that can be lethal for insects of different orders at larval stages. Although the horizontal transmission mechanisms are poorly known, densoviral pathogenesis usually starts with the ingestion of contaminated food by the host. Depending on the virus, this leads to replication restricted to the midgut or excluding it. In both cases the success of infection depends on the virus capacity to enter the intestinal epithelium. Using the Junonia coenia densovirus (JcDNV) as the prototype virus and the lepidopteran host Spodoptera frugiperda as an interaction model, we focused on the early mechanisms of infection during which JcDNV crosses the intestinal epithelium to reach and replicate in underlying target tissues. We studied the kinetics of interaction of JcDNV with the midgut epithelium and the transport mechanisms involved. Using several approaches, in vivo, ex vivo, and in vitro, at molecular and cellular levels, we show that JcDNV is specifically internalized by endocytosis in absorptive cells and then crosses the epithelium by transcytosis. As a consequence, viral entry disturbs the midgut function. Finally, we showed that four mutations on the capsid of JcDNV affect specific recognition by the epithelial cells but not their binding.

Liver X receptors, nervous system, and lipid metabolism.

Lipids in the nervous system are represented by cholesterol and phospholipids as constituents of cell membranes and, in particular, of myelin. Therefore, lipids are finely regulated to guarantee physiological functions. In the central nervous system, cholesterol is locally synthesized due to the presence of the blood brain barrier. In the peripheral nervous system cholesterol is either up-taken by lipoproteins and/or produced by de novo biosynthesis. Defects in lipid homeostasis in these tissues lead to structural and functional changes that often result in different pathological conditions depending on the affected pathways (i.e. cholesterol biosynthesis, cholesterol efflux, fatty acid biosynthesis etc.). Alterations in cholesterol metabolism in the central nervous system are linked to several disorders such as Alzheimer's disease, Huntington disease, Parkinson disease, Multiple sclerosis, Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and glioblastoma. In the peripheral nervous system changes in lipid metabolism are associated with the development of peripheral neuropathy that may be caused by metabolic disorders, injuries, therapeutics, and autoimmune diseases. Transcription factors, such as the Liver X receptors (LXR), regulate both cholesterol and fatty acid metabolism in several tissues including the nervous system. In the last few years several studies elucidated the biology of LXR in the nervous system due to the availability of knock-out mice and the development of synthetic ligands. Here, we review a survey of the literature focused on the central and peripheral nervous system and in physiological and pathological settings with particular attention to the roles played by LXR in both districts.

The intestinal barrier in lepidopteran larvae: permeability of the peritrophic membrane and of the midgut epithelium to two biologically active peptides.

Endogenous peptide regulators of insect physiology and development are presently being considered as potential biopesticides, but their efficacy by oral delivery cannot be easily anticipated because of the limited information on how the insect gut barrier handles these kind of molecules. We investigated, in Bombyx mori larvae, the permeability properties of the two components of the intestinal barrier, the peritrophic membrane (PM) and the midgut epithelium, separately isolated and perfused in conventional Ussing chambers. The PM discriminated compounds of different dimensions but was easily crossed by two small peptides recently proposed as bioinsecticides, the neuropeptide proctolin and Aedes aegypti Trypsin Modulating Oostatic Factor (Aea-TMOF), although their flux values indicated that the permeability was highly affected by their steric conformation. To date, there is very little functional data available on how peptides cross the insect intestinal epithelium, but it has been speculated that peptides could reach the haemocoel through the paracellular pathway. We characterized the permeability properties of this route to a number of organic molecules, showing that B. mori septate junction was highly selective to both the dimension and the charge of the permeant compound. Confocal images of whole-mount midguts incubated with rhodamine(rh)-proctolin or fluorescein isothiocyanate (FITC)-Aea-TMOF added to the mucosal side of the epithelium, revealed that rh-proctolin did not enter the cell and crossed the midgut only by the paracellular pathway, while FITC-Aea-TMOF did cross the cell apical membrane, permeating also through the transcellular route.

A megalin-like receptor is involved in protein endocytosis in the midgut of an insect (Bombyx mori, Lepidoptera).

The mechanism responsible for fluorescein isothiocyanate (FITC)-albumin internalization by columnar cells in culture obtained from the midgut of Bombyx mori larvae was examined by confocal laser scanning microscopy. Protein uptake changed over time, and it appeared to be energy dependent, since it was strongly reduced by both low temperatures and metabolic inhibitors. Labeled albumin uptake as a function of increasing protein concentration showed a saturation kinetics with a Michaelis constant value of 2.0 +/- 0.6 microM. These data are compatible with the occurrence of receptor-mediated endocytosis. RT-PCR analysis and colocalization experiments with an anti-megalin primary antibody indicated that the receptor involved was a putative homolog of megalin, the multiligand endocytic receptor belonging to the low-density lipoprotein receptor family, responsible for the uptake of various molecules, albumin included, in many epithelial cells of mammals. This insect receptor, like the mammalian counterpart, required Ca(2+) for albumin internalization and was inhibited by gentamicin. FITC-albumin internalization was clathrin mediated, since two inhibitors of this process caused a significant reduction of the uptake, and clathrin and albumin colocalized in the intermicrovillar areas of the apical plasma membrane. The integrity of actin and microtubule organization was essential for the correct functioning of the endocytic machinery.