Metabolic pathologies mainly originate from adipose tissue (AT) dysfunctions. AT differences are associated with fat-depot anatomic distribution in subcutaneous (SAT) and visceral omental (VAT) pads. We address the question whether the functional differences between the two compartments may be present early in the adipose stem cell (ASC) instead of being restricted to the mature adipocytes. Using a specific human ASC model, we evaluated proliferation/differentiation of ASC from abdominal SAT-(S-ASC) and VAT-(V-ASC) paired biopsies in parallel as well as the electrophysiological properties and functional activity of ASC and their in vitro-derived adipocytes. A dramatic difference in proliferation and adipogenic potential was observed between the two ASC populations, S-ASC having a growth rate and adipogenic potential significantly higher than V-ASC and giving rise to more functional and better organized adipocytes. To our knowledge, this is the first comprehensive electrophysiological analysis of ASC and derived-adipocytes, showing electrophysiological properties, such as membrane potential, capacitance and K+-current parameters which confirm the better functionality of S-ASC and their derived adipocytes. We document the greater ability of S-ASC-derived adipocytes to secrete adiponectin and their reduced susceptibility to lipolysis. These features may account for the metabolic differences observed between the SAT and VAT. Our findings suggest that VAT and SAT functional differences originate at the level of the adult ASC which maintains a memory of its fat pad of origin. Such stem cell differences may account for differential adipose depot susceptibility to the development of metabolic dysfunction and may represent a suitable target for specific therapeutic approaches.

No abstract

The purpose of this study was to determine whether long-term modulation of inflammatory activity by tumor necrosis factor (TNF)-α inhibitors has some influence on insulin resistance (IR). 16 active rheumatoid arthritis (RA) patients without CV risk factors treated with anti-TNF-α agents were included in this study. RA activity by disease activity score 28, IR by HOMA2-IR, body composition by impedance analysis, physical activity by accelerometry, abdominal fat distribution by magnetic resonance imaging, and serum level of key adipokines by ELISA were measured at baseline and during a 1-year follow-up period. Patient body mass index increased significantly (26.94 ± 3.88 vs. 28.06 ± 4.57 kg/m2, p=0.02) after 1 year of treatment. Body composition, in terms of fat and fat-free mass, remained unchanged except for a significant elevation in body cell mass (25.50 ± 4.60 vs. 26.60 ± 3.17 kg, p=0.02). Basal levels of IR in the RA patients included in this study were significantly higher than healthy controls (1.6 ± 0.8 vs. 1.11 ± 0.56, p=0.011) but did not change during the follow-up. Nor did basal concentrations of adiponectin, visfatin, leptin, ghrelin, resistin, and apelin in response to anti-TNF-α treatment; only retinol-binding protein 4, showed a significant increase (51.7 ± 32.7 vs. 64.9 ± 28.4 μg/ml, p=0.03) at the end of the study. IR, adiposity distribution, and serum levels of most adipokines are not significantly affected by long-term inhibition of TNF-α in RA patients. Our data suggest that although systemic blockade of TNF-α exerts an anticachectic effect in RA patients, it does not seem to play a major role in IR.

The massive weight loss obtained with bariatric surgery was associated with an improvement in some semen parameters. The correlations found between weight loss and semen parameter variations after surgery suggest that these might occur early downstream of the testis and more slowly than the changes in the sex hormones.

Carnation Italian ringspot tombusvirus encodes a protein, referred to as 36K, that possesses a mitochondrial targeting signal and two transmembrane segments which are thought to anchor this protein to the outer membrane of the mitochondrial envelope of infected plant cells. To determine the topology of the virus protein inserted in the cell membrane, as well as the sequence requirements for targeting and insertion, an in vivo system was set up in which this could be analysed in the absence of productive virus infection. The 36K protein was expressed in the yeast Saccharomyces cerevisiae in native form or fused to the green fluorescent protein. Using a fluorescence microscope, large green-fluorescing cytoplasmic aggregates were visible which stained red when cells were treated with the vital stain MitoTracker, which is specific for mitochondria. These aggregates were shown by electron microscopy to be composed of either mitochondria or membranes. The latter type was particularly abundant for the construct in which the green fluorescent protein was fused at the N terminus of the 36K protein. Immunoelectron microscopy demonstrated that the viral protein is present in the anomalous aggregates and Western blot analysis of protein extracts showed 36K to be resistant to alkaline, urea or salt extraction, a property of integral membrane proteins.