Comprehensive molecular characterization of human adipocytes reveals a transient brown phenotype.

Background: Functional brown adipose tissue (BAT), involved in energy expenditure, has recently been detected in substantial amounts in adults. Formerly overlooked BAT has now become an attractive anti-obesity target.

Methods And Results: Molecular characterization of human brown and white adipocytes, using a myriad of techniques including high-throughput RNA sequencing and functional assays, showed that PAZ6 and SW872 cells exhibit classical molecular and phenotypic markers of brown and white adipocytes, respectively.

PAZ6 cells constitute a representative model for human brown pre-adipocytes.

The role of brown adipose tissue (BAT) in human metabolism and its potential as an anti-obesity target organ have recently received much renewed attention. Following radiological detection of substantial amounts of BAT in adults by several independent research groups, an increasing number of studies are now dedicated to uncover BAT's genetic, developmental, and environmental determinants. In contrast to murine BAT, human BAT is not present as a single major fat depot in a well-defined location.

A new highly efficient substrate-trapping mutant of protein tyrosine phosphatase 1B (PTP1B) reveals full autoactivation of the insulin receptor precursor.

PTP1B is a protein tyrosine-phosphatase located on the cytosolic side of the endoplasmic reticulum that plays an important role in the regulation of the insulin receptor (IR). Replacement of the conserved Asp-181 by alanine is known to convert PTP1B into a substrate-trapping protein that binds to but cannot dephosphorylate its substrates. In this work, we have studied the effect of an additional mutation (Y46F) on the substrate-trapping efficiency of PTP1B-D181A.

O-GlcNAc modification of FoxO1 increases its transcriptional activity: a role in the glucotoxicity phenomenon?

O-GlcNAc glycosylations on serines or threonines are reversible post-translational modifications that control the localisation, the activity or the stability of cytosolic and nuclear proteins. These dynamic modifications are tightly dependent on the availability of glucose and on its flux through the hexosamine biosynthetic pathway. We recently showed that treatments that increase protein O-GlcNAc glycosylation (high-glucose concentrations, glucosamine) or inhibit their deglycosylation (PUGNAc), induced O-GlcNAc modification of FoxO1 in HEK293 cells.

O-glycosylation of FoxO1 increases its transcriptional activity towards the glucose 6-phosphatase gene.

Mono-O-glycosylations post-translationally regulate the activity of nucleocytoplasmic proteins. We showed that glucosamine and an inhibitor of deglycosylation (PUGNAc) induced O-glycosylation of FoxO1, resulting in increased expression of a glucose-6-phosphatase reporter gene. This effect was independent of FoxO1 re-localisation, since it was also observed with constitutively nuclear FoxO1-AAA mutant.

Effects of intranasal administration of a leptin-secreting Lactococcus lactis recombinant on food intake, body weight, and immune response of mice.

Leptin is an adipocyte-derived pleiotropic hormone that modulates a large number of physiological functions, including control of body weight and regulation of the immune system. In this work, we show that a recombinant strain of the food-grade lactic acid bacterium Lactococcus lactis (LL-lep) can produce and efficiently secrete human leptin. The secreted leptin is a fully biologically active hormone, as demonstrated by its capacity to stimulate a STAT3 reporter gene in HEK293 cells transfected with the Ob-Rb leptin receptor.

Interaction between the insulin receptor and Grb14: a dynamic study in living cells using BRET.

Grb14 is a molecular adaptor that binds to the activated insulin receptor (IR) and negatively regulates insulin signaling. We have studied the dynamics of interaction of the IR with Grb14, in real time, in living HEK cells, using bioluminescence resonance energy transfer (BRET). Insulin rapidly and dose-dependently stimulated this interaction.

Interaction with Grb14 results in site-specific regulation of tyrosine phosphorylation of the insulin receptor.

The dynamics of interaction of the insulin receptor (IR) with Grb14 was monitored, in real time, in living human embryonic kidney cells, using bioluminescence resonance energy transfer (BRET). We observed that insulin rapidly and dose-dependently stimulated this interaction. We also observed that insulin-induced BRET between the IR and protein tyrosine phosphatase 1B (PTP1B) was markedly reduced by Grb14, suggesting that Grb14 regulated this interaction in living cells.

The influence of dietary fish-oil supplementation on cutaneous Leishmania amazonensis infection in mice.

Dietary fish-oil (FO) supplementation has been shown to inhibit inflammation in various clinical disease states and to be beneficial in experimental models of inflammation and bacterial and plasmodial infection. In mice, FO increases macrophage production of tumour necrosis factor alpha (TNF). Production of TNF has been reported to be important in the resistance of mice against various Leishmania spp.