The farnesoid X receptor modulates adiposity and peripheral insulin sensitivity in mice

The farnesoid X receptor (FXR) is a bile acid (BA)-activated nuclear receptor that plays a major role in the regulation of BA and lipid metabolism. Recently, several studies have suggested a potential role of FXR in the control of hepatic carbohydrate metabolism, but its contribution to the maintenance of peripheral glucose homeostasis remains to be established. FXR-deficient mice display decreased adipose tissue mass, lower serum leptin concentrations, and elevated plasma free fatty acid levels. Glucose and insulin tolerance tests revealed that FXR deficiency is associated with impaired glucose tolerance and insulin resistance. Moreover, whole-body glucose disposal during a hyperinsulinemic euglycemic clamp is decreased in FXR-deficient mice. In parallel, FXR deficiency alters distal insulin signaling, as reflected by decreased insulin-dependent Akt phosphorylation in both white adipose tissue and skeletal muscle. Whereas FXR is not expressed in skeletal muscle, it was detected at a low level in white adipose tissue in vivo and induced during adipocyte differentiation in vitro. Moreover, mouse embryonic fibroblasts derived from FXR-deficient mice displayed impaired adipocyte differentiation, identifying a direct role for FXR in adipocyte function. Treatment of differentiated 3T3-L1 adipocytes with the FXR-specific synthetic agonist GW4064 enhanced insulin signaling and insulin-stimulated glucose uptake. Finally, treatment with GW4064 improved insulin resistance in genetically obese ob/ob mice in vivo. Although the underlying molecular mechanisms remain to be unraveled, these results clearly identify a novel role of FXR in the regulation of peripheral insulin sensitivity and adipocyte function. This unexpected function of FXR opens new perspectives for the treatment of type 2 diabetes.     

Gamma-interferon inhibits extracellular matrix synthesis and remodeling in collagen lattice cultures of normal and scleroderma skin fibroblasts.

Three-dimensional collagen lattice cultures of fibroblasts mimic the in vivo situation better than monolayer cultures. Here, skin fibroblasts from scleroderma patients and healthy controls were cultivated in collagen lattices, and the effects of recombinant human gamma-interferon (IFN-gamma) on these cultures investigated. IFN-gamma inhibited collagen lattice retraction in a dose-dependent way at concentrations ranging from 10 to 10,000 U/ml. This effect was independent of any alteration to the cell proliferation within the lattices. The inhibition was of the same order of magnitude in normal and pathological fibroblasts. The synthesis of collagen and non-collagen proteins, particularly fibronectin, was increased in scleroderma cultures. It was inhibited in both normal and scleroderma fibroblasts by IFN-gamma, with a maximal effect at the concentration 1000 U/ml, but the inhibition of protein synthesis was far more intense in scleroderma than in normal cells. In situ hybridization, Northern blot and dot blot analyses showed that mRNA coding for pro alpha 1(I) collagen was decreased in IFN-gamma-treated cells, indicating an effect at the pretranslational level. IFN-gamma also inhibited glycosaminoglycan synthesis, but in scleroderma cells only. This study shows that IFN-gamma regulates cell behavior in three-dimensional collagen matrices: (i) it decreases protein and specifically glycosaminoglycan synthesis in scleroderma fibroblasts, (ii) it modulates the interactions between cells and matrix that lead to the retraction of the lattice. Whereas collagen synthesis is largely decreased in lattice cultures like in vivo, it remains increased in the case of scleroderma compared to normal fibroblasts and may be down-regulated by IFN-gamma. Similar conclusions may be drawn for fibronectin and glycosaminoglycans. The inhibitory effect of IFN-gamma on the retraction capacity of fibroblasts and on their ability to synthesize increased amounts of extracellular matrix macromolecules may be of potential interest for therapeutic use of IFN-gamma in scleroderma patients.     

First evidence for diploidy and genetic recombination in free-living amoebae of the genus naegleria on the basis of electrophoretic variation

Electrophoretic variation for 15 enzyme-coding genes was studied in various Naegleria (Rhizopoda, Vahlkampfiidae) species. The occurrence of complex banding patterns provided the first evidence of a diploid structure of the genome of these amoebae. The putative loci identified were found not to be linked and the genotypic distribution suggested chromosomal recombination for one species (Naegleria lovaniensis).     

A Reanalysis of Protein Polymorphism in Drosophila Melanogaster, D. Simulans, D. Sechellia and D. Mauritiana: Effects of Population Size and Selection

Comparison of synonymous and nonsynonymous variation/substitution within and between species at individual genes has become a widely used general approach to detect the effect of selection versus drift. The sibling species group comprised of two cosmopolitan (Drosophila melanogaster and Drosophila simulans) and two island (Drosophila mauritiana and Drosophila sechellia) species has become a model system for such studies. In the present study we reanalyzed the pattern of protein variation in these species, and the results were compared against the patterns of nucleotide variation obtained from the literature, mostly available for melanogaster and simulans. We have mainly focused on the contrasting patterns of variation between the cosmopolitan pair. The results can be summarized as follows: (1) As expected the island species D. mauritiana and D. sechellia showed much less variation than the cosmopolitan species D. melanogaster and D. simulans. (2) The chromosome 2 showed significantly less variation than chromosome 3 and X in all four species which may indicate effects of past selective sweeps. (3) In contrast to its overall low variation, D. mauritiana showed highest variation for X-linked loci which may indicate introgression from its sibling, D. simulans. (4) An average population of D. simulans was as heterozygous as that of D. melanogaster (14.4% v.s. 13.9%) but the difference was large and significant when considering only polymorphic loci (37.2% v.s. 26.1%). (5) The species-wise pooled populations of these two species showed similar results (all loci = 18.3% v.s. 20.0%, polymorphic loci = 47.2% v.s. 37.6%). (6) An average population of D. simulans had more low-frequency alleles than D. melanogaster, and the D. simulans alleles were found widely distributed in all populations whereas the D. melanogaster alleles were limited to local populations. As a results of this, pooled populations of D. melanogaster showed more polymorphic loci than those of D. simulans (48.0% v.s. 32.0%) but the difference was reduced when the comparison was made on the basis of an average population (29.1% v.s. 21.4%). (7) While the allele frequency distributions within populations were nonsignificant in both D. melanogaster and D. simulans, melanogaster had fewer than simulans, but more than expected from the neutral theory, low frequency alleles. (8) Diallelic loci with the second allele with a frequency less than 20% had similar frequencies in all four species but those with the second allele with a frequency higher than 20% were limited to only melanogaster the latter group of loci have clinal (latitudinal) patterns of variation indicative of balancing selection. (9) The comparison of D. simulans/D. melanogaster protein variation gave a ratio of 1.04 for all loci and 1.42 for polymorphic loci, against a ratio of approximately 2-fold difference for silent nucleotide sites. This suggests that the species ratios of protein and silent nucleotide polymorphism are too close to call for selective difference between silent and allozyme variation in D. simulans. In conclusion, the contrasting levels of allozyme polymorphism, distribution of rare alleles, number of diallelic loci and the patterns of geographic differentiation between the two species suggest the role of natural selection in D. melanogaster, and of possibly ancient population structure and recent worldwide migration in D. simulans. Population size differences alone are insufficient as an explanation for the patterns of variation between these two species.     

Dunnigan lipodystrophy syndrome: French National Diagnosis and Care Protocol (PNDS; Protocole National de Diagnostic et de Soins)

Phenylketonuria (PKU) is an inherited metabolic disease characterized by a defective conversion of phenylalanine (Phe) to tyrosine, potentially leading to Phe accumulation in the brain. Dietary restriction since birth has led to normal cognitive development. However, PKU patients can still develop cognitive or behavioral abnormalities and subtle neurological deficits. Despite the increasing evidence in the field, the assessment of neurocognitive, psychopathological, and neurological follow-up of PKU patients at different ages is still debated. The high interindividual variability in the cognitive outcome of PKU patients makes the specificity of the neurocognitive and behavioral assessment extremely challenging. In the present paper, a multidisciplinary panel of Italian PKU experts discussed different tools available for cognitive, psychopathological, and neurological assessment at different ages based on the existing literature and daily clinical practice. This study aims to provide evidence and a real-life-based framework for a specific clinical assessment of pediatric, adolescent, and adult patients affected by PKU.

     

Microsatellite variation suggests a recent fine-scale population structure of <Emphasis Type="Italic">Drosophila sechellia</Emphasis>, a species endemic of the Seychelles archipelago

Drosophila sechellia is closely related to the cosmopolitan and widespread model species, D. simulans. This species, endemic to the Seychelles archipelago, is specialized on the fruits of Morinda citrifolia, and harbours the lowest overall genetic diversity compared to other species of Drosophila. This low diversity is associated with a small population size. In addition, no obvious population structure has been evidenced so far across islands of the Seychelles archipelago. Here, a microsatellite panel of 17 loci in ten populations from nine islands of the Seychelles was used to assess the effect of the D. sechellia’s fragmented distribution on the fine-scale population genetic structure, the migration pattern, as well as on the demography of the species. Contrary to previous results, also based on microsatellites, no evidence for population contraction in D. sechellia was found. The results confirm previous studies based on gene sequence polymorphism that showed a long-term stable population size for this species. Interestingly, a pattern of Isolation By Distance which had not been described yet in D. sechellia was found, with evidence of first-generation migrants between some neighbouring islands. Bayesian structuring algorithm results were consistent with a split of D. sechellia into two main groups of populations: Silhouette/Mahé versus all the other islands. Thus, microsatellites suggest that variability in D. sechellia is most likely explained by local genetic exchanges between neighbouring islands that have recently resulted in slight differentiation of the two largest island populations from all the others.     

Hierarchical classification of microorganisms based on high‐dimensional phenotypic data

The classification of microorganisms by high‐dimensional phenotyping methods such as FTIR spectroscopy is often a complicated process due to the complexity of microbial phylogenetic taxonomy. A hierarchical structure developed for such data can often facilitate the classification analysis. The hierarchical tree structure can either be imposed to a given set of phenotypic data by integrating the phylogenetic taxonomic structure or set up by revealing the inherent clusters in the phenotypic data. In this study, we wanted to compare different approaches to hierarchical classification of microorganisms based on high‐dimensional phenotypic data. A set of 19 different species of molds (filamentous fungi) obtained from the mycological strain collection of the Norwegian Veterinary Institute (Oslo, Norway) is used for the study. Hierarchical cluster analysis is performed for setting up the classification trees. Classification algorithms such as artificial neural networks (ANN), partial least‐squared discriminant analysis and random forest (RF) are used and compared. The 2 methods ANN and RF outperformed all the other approaches even though they did not utilize predefined hierarchical structure. To our knowledge, the RF approach is used here for the first time to classify microorganisms by FTIR spectroscopy.      

Genetic population structure of the German cockroach, Blattella germanica: Absence of geographical variation

The genetic structure of 31 populations of the German cockroach, Blattella germanica (L.), located in two French cities 900 km apart, was estimated by enzyme gel electrophoresis. A set of 41 loci was analysed. Eight loci (4 Est, 3 Lap and 1 Got) were polymorphic. Diversity was estimated at different geographical levels: the overall population, between cities and within a city. Hierarchical F-statistics indicated significant genetic differentiation between all populations and among populations within each city, but no differentiation between cities. F_ST values for populations within each city and for the overall sample were substantially dissimilar. In addition, a cluster analysis did not separate populations according to their geographical origin but according to the predominance of either of the two alternative Est-4 alleles. The results of this analysis point to the absence of genetic differentiation on a large geographical scale: no large-scale geographical distance effect was detected. However, we evidenced strong genetic substructuring on a local scale, within cities.     

Circulating lupus-type anticoagulant, a risk factor for thrombosis by inhibition of protein C activation

The lupus anticoagulant is a risk factor of thrombosis. The non thrombogenic endothelial surface could be a target for the lupus anticoagulant. We have investigated the effect of purified immunoglobulins G of five patients with LA on the thrombomodulin activity of cultured human endothelial cells from umbilical cord vein. The rate of activation of purified protein C (PC) (30 nM) by the endothelial cells in the presence of thrombin (0.1 U/dish) has been measured by hydrolysis of substrate S 2366. Activated PC has been 7.37 +/- 0.78 pmoles X ml-1 X h-1 in the presence of buffer and 7.2 +/- 0.78 pmoles X ml-1 X h-1 in the presence of control IgG (2 mg/dish). Heat aggregated IgG did not induce any significant change. Patient's IgG lowered significantly the rate of PC activation (4.86 +/- 1.04 pmoles X ml-1 X h-1, p less than 0.001). Fab fragment from two of these patient's IgG displayed the same inhibition. Moreover neutralization of this effect was obtained by addition of phospholipids (70% phosphatidylcholine, 30% phosphatidylserine) in excess to patient's IgG. Activation of PC has been also performed using purified rabbit thrombomodulin and a similar inhibition by patient's IgG was found. These results seem to indicate that antibodies present in the IgG fractions containing LA could be directed against phospholipids associated to thrombomodulin activity. Reduction of PC activation if present in the patients with LA could play a role in the occurrence of thrombosis.