Glucocorticoid-induced androgen inactivation by aldo-keto reductase 1C2 promotes adipogenesis in human preadipocytes

Adipogenesis and lipid storage in human adipose tissue are inhibited by androgens such as DHT. Inactivation of DHT to 3α-diol is stimulated by glucocorticoids in human preadipocytes. We sought to characterize glucocorticoid-induced androgen inactivation in human preadipocytes and to establish its role in the antiadipogenic action of DHT. Subcutaneous and omental primary preadipocyte cultures were established from fat samples obtained in subjects undergoing abdominal surgeries. Inactivation of DHT to 3α/β-diol for 24 h was measured in dexamethasone- or vehicle-treated cells. Specific downregulation of aldo-keto reductase 1C (AKR1C) enzymes in human preadipocytes was achieved using RNA interference. In whole adipose tissue sample, cortisol production was positively correlated with androgen inactivation in both subcutaneous and omental adipose tissue (P < 0.05). Maximal dexamethasone (1 μM) stimulation of DHT inactivation was higher in omental compared with subcutaneous fat from men as well as subcutaneous and omental fat from women (P < 0.05). A significant positive correlation was observed between BMI and maximal dexamethasone-induced DHT inactivation rates in subcutaneous and omental adipose tissue of men and women (r = 0.24, n = 26, P < 0.01). siRNA-induced downregulation of AKR1C2, but not AKR1C1 or AKR1C3, significantly reduced basal and glucocorticoid-induced androgen inactivation rates (P < 0.05). The inhibitory action of DHT on preadipocyte differentiation was potentiated following AKR1C2 but not AKR1C1 or AKR1C3 downregulation. Specifically, lipid accumulation, G3PDH activity, and FABP4 mRNA expression in differentiated preadipocytes exposed to DHT were reduced further upon AKR1C2 siRNA transfection. We conclude that glucocorticoid-induced androgen inactivation is mediated by AKR1C2 and is particularly effective in omental preadipocytes of obese men. The interplay between glucocorticoids and AKR1C2-dependent androgen inactivation may locally modulate adipogenesis and lipid accumulation in a depot-specific manner.     

Deleterious impact of elaidic fatty acid on ABCA1-mediated cholesterol efflux from mouse and human macrophages

Consumption of trans fatty acids (TFA) increase cardiovascular risk more than do saturated FA, but the mechanisms explaining their atherogenicity are still unclear. We investigated the impact of membrane incorporation of TFA on cholesterol efflux by exposing J774 mouse macrophages or human monocyte-derived macrophages (HMDM) to media enriched or not (standard medium) with industrially produced elaidic (trans-9 18:1) acid, naturally produced vaccenic (trans-11 18:1) acid (34 h, 70 μM) or palmitic acid. In J774 macrophages, elaidic and palmitic acid, but not vaccenic acid, reduced ABCA1-mediated efflux by ~23% without affecting aqueous diffusion, SR-BI or ABCG1-mediated pathways, and this effect was maintained in cholesterol-loaded cells. The impact of elaidic acid on the ABCA1 pathway was weaker in cholesterol-normal HMDM, but elaidic acid induced a strong reduction of ABCA1-mediated efflux in cholesterol-loaded cells (-36%). In J774 cells, the FA supplies had no impact on cellular free cholesterol or cholesteryl ester masses, the abundance of ABCA1 mRNA or the total and plasma membrane ABCA1 protein content. Conversely, TFA or palmitic acid incorporation induced strong modifications of the membrane FA composition with a decrease in the ratio of (cis-monounsaturated FA+polyunsaturated FA):(saturated FA+TFA), with elaidic and vaccenic acids representing each 20% and 13% of the total FA composition, respectively. Moreover, we demonstrated that cellular ATP was required for the effect of elaidic acid, suggesting that it contributes to atherogenesis by impairing ABCA1-mediated cholesterol efflux in macrophages, likely by decreasing the membrane fluidity, which could thereby reduce ATPase activity and the function of the transporter.     

Gene expression profiling of 3T3-L1 adipocytes exposed to phloretin

Adipocyte dysfunction plays a major role in the outcome of obesity, insulin resistance and related cardiovascular complications. Thus, considerable efforts are underway in the pharmaceutical industry to find molecules that target the now well-documented pleiotropic functions of adipocyte. We previously reported that the dietary flavonoid phloretin enhances 3T3-L1 adipocyte differentiation and adiponectin expression at least in part through PPARγ activation. The present study was designed to further characterize the molecular mechanisms underlying the phloretin-mediated effects on 3T3-L1 adipocytes using microarray technology. We show that phloretin positively regulates the expression of numerous genes involved in lipogenesis and triglyceride storage, including GLUT4, ACSL1, PEPCK1, lipin-1 and perilipin (more than twofold). The expression of several genes encoding adipokines, in addition to adiponectin and its receptor, is positively or negatively regulated in a way that suggests a possible reduction in systemic insulin resistance and obesity-associated inflammation. Improvement of insulin sensitivity is also suggested by the overexpression of genes associated with insulin signal transduction, such as CAP, PDK1 and Akt2. Many of these genes are PPARγ targets, confirming the involvement of PPARγ pathway in the phloretin effects on adipocytes. In light of these microarray data, it is reasonable to assume that phloretin may be beneficial for reducing insulin resistance, in a similar way to the thiazolidinedione class of antidiabetic drugs.     

A simple method for measurement of maximal downstroke power on friction-loaded cycle ergometer

The aim of this study was to propose and validate a post-hoc correction method to obtain maximal power values taking into account inertia of the flywheel during sprints on friction-loaded cycle ergometers. This correction method was obtained from a basic postulate of linear deceleration-time evolution during the initial phase (until maximal power) of a sprint and included simple parameters as flywheel inertia, maximal velocity, time to reach maximal velocity and friction force. The validity of this model was tested by comparing measured and calculated maximal power values for 19 sprint bouts performed by five subjects against 0.6-1 N kg(-1) friction loads. Non-significant differences between measured and calculated maximal power (1151+/-169 vs. 1148+/-170 W) and a mean error index of 1.31+/-1.20% (ranging from 0.09% to 4.20%) showed the validity of this method. Furthermore, the differences between measured maximal power and power neglecting inertia (20.4+/-7.6%, ranging from 9.5% to 33.2%) emphasized the usefulness of power correcting in studies about anaerobic power which do not include inertia, and also the interest of this simple post-hoc method.     

Synthesis and cytotoxic activity of benzo[c][1,7] and [1,8]phenanthrolines analogues of nitidine and fagaronine

Fagaronine and nitidine are natural benzo[c] phenanthridinium alkaloids, which display antileukemic activity. Both act as topoisomerase I and topoisomerase II inhibitors. The objective of the present study was to prepare noncharged isosters of these compounds, with replacement of the aromatic A ring by a pyridine ring, present in other topoisomerase I inhibitors. Various 7,8- and 8,9-dimethoxy and metylenedioxy benzo[c][1,7] and [1,8]phenanthrolines were readily synthesized by benzyne-mediated cyclization of the corresponding substituted N-(2-halobenzyl)-5-quinolinamines or 5-isoquinolinamines. In both series, compounds bearing oxygenated substituents at positions 8 and 9 exhibited cytotoxic properties towards L1210 murine leukemia cells, which may result from their capacities to intercalate into DNA. Topoisomerase I inhibition was observed for all active compounds.     

Tree Climbing Strategies for Primate Ecological Studies

Primate ecological studies can benefit from accessing the canopy to estimate intra-tree and inter-tree variation in food availability and nutrient value, patch and subpatch depletion, foraging efficiency, as well as nest structure and nesting behaviors, parasitic transmission and predator detectability. We compare several ways to access the canopy and examine their suitability for studies of primates. Two of them—the Single Rope Technique and the Climbing Spur Method—allow people to safely access almost all kinds of trees, regardless of their size, height or shape. Modern climbing gear and contemporaneous safety protocols, derived from rock climbers, speleologists, and industrial arborists, are reliable and appropriate for primate ecological studies. Climbing gear is specialized and still expensive for students, but tree climbing can be dangerous during specific maneuvres. Consequently, formal training and preliminary experience are essential before attempting to collect data. We discuss the physics of falling, risk assessment associated with a fall, knots, gear and safety precautions. Finally, we propose a Tree Climbing Safety Protocol adapted for 2 climbing methods and primate field ecology. Researchers should be aware that climbing safety depends on their own judgment, which must be based on competent instruction, experience, and a realistic assessment of climbing ability. Therefore, the information we provide should be used only to supplement competent personal instruction and training in situ. Although most primate observations have been and will mostly be done from the ground in the future, canopy information complements the observations. Canopy data will add a significant new dimension to our knowledge of primates by providing strategic information otherwise unavailable.     

Early steps in microbial colonization processes at deep-sea hydrothermal vents

A pluri-disciplinary in situ colonization experiment was performed to study early stages of colonization in deep-sea vent Alvinella spp. worm habitats. Four colonization devices were deployed onto Alvinella spp. colonies of different chimneys of the East-Pacific Rise (EPR 13 degrees N), for two different periods: a short (less than a week) and a longer one (3 weeks). Video imagery and monitoring of the thermal and physico-chemical conditions were performed during the colonization experiments. Numerous microorganisms bearing specialized adhesion-appendages and/or high amounts of polymeric extracellular matrix were observed on devices, which may efficiently contribute to the colonization of new surfaces. The microbial cohorts preceding and accompanying Alvinella spp. settlement were identified. In all cases, Archaea could not be detected and the microbial mats were essentially composed of e-Proteobacteria. Within this group, one phylotype (AlviH2) was found to dominate the libraries of three colonization devices. Dominance of e-Proteobacteria in the libraries may reflect the wide physiological variety encountered within this group or an adaptability of these microorganisms towards their changing environment. Bacteria affiliated to the Cytophaga-Flavobacterium-Bacteroides group or to the e-Proteobacteria, that grow either chemo-organoheterotrophically by fermentation or chemolithoautotrophically with H2 as an electron donor and S degrees /S2O32- or NO3- as a terminal electron acceptor, were isolated from one of the microbial mat formed in 20 days.     

Pharmacokinetic investigation of a 14C-labelled beta 3/alpha tetrapeptide in rats

The solid-phase synthesis and an ADME investigation with albino and pigmented male rats of the doubly 14C-labelled beta/alpha-tetrapeptide derivative Ac-beta3 hTyr-(D)Trp-beta3 hLys-beta3 hThr-lactone (3; Fig. 3) are described. After intravenous (i.v.) and peroral (p.o.) administration of the peptide, its concentration in blood and plasma, its tissue distribution, and the metabolism and the excretion of the peptide were analyzed over a period of up to 7 days post dose. The tetrapeptide in its ring opened form, 5, has a bioavailability of ca. 25%; radioactivity is distributed in the animals in an organ-specific way, and the compound appears to pass the blood-brain barrier to a very small extent, if at all (Tables 1-3 and Figs. 2-6). Excretion (37% renal, 44% fecal, including biliary) of the tetrapeptide 4 days after i.v. administration is almost complete, with only 4.3% remaining in the carcass; 4 days after p.o. administration 97% of the dose has been excreted in the feces. Radiochromatograms taken of plasma (0.5 and 24 h after i.v. dosing) and of urine and feces extracts (0-48 h collected) reveal the presence of lactone 3 and/or the corresponding hydroxy acid 5 with essentially no or very minor other peaks, respectively, representing possible metabolites (Tables 4-6, and Fig. 7 and 8). A comparison with a previous ADME investigation of a beta-nonapeptide show that--except for the lack of metabolism--all aspects of exposure, distribution, and elimination are different (structure-specific properties). The investigated tetrapeptide 3 is a potent and highly specific agonist of the somatostatin receptor hsst4, rendering the results described herein promising for diagnostic and therapeutic applications of beta-peptides.