Adipocytes as a Link Between Gut Microbiota-Derived Flagellin and Hepatocyte Fat Accumulation

While the role of both elevated levels of circulating bacterial cell wall components and adipose tissue in hepatic fat accumulation has been recognized, it has not been considered that the bacterial components-recognizing adipose tissue receptors contribute to the hepatic fat content. In this study we found that the expression of adipose tissue bacterial flagellin (FLG)-recognizing Toll-like receptor (TLR) 5 associated with liver fat content (r = 0.699, p = 0.003) and insulin sensitivity (r = -0.529, p = 0.016) in humans (n = 23). No such associations were found for lipopolysaccharides (LPS)-recognizing TLR4. To study the underlying molecular mechanisms of these associations, human HepG2 hepatoma cells were exposed in vitro to the conditioned culture media derived from FLG or LPS-challenged human adipocytes. The adipocyte-mediated effects were also compared to the effects of direct HepG2 exposure to FLG and LPS. We found that the media derived from FLG-treated adipocytes stimulated fat accumulation in HepG2 cells, whereas either media derived from LPS-treated adipocytes or direct FLG or LPS exposure did not. This is likely due to that FLG-treatment of adipocytes increased lipolysis and secretion of glycerol, which is known to serve a substrate for triglyceride synthesis in hepatocytes. Similarly, only FLG-media significantly decreased insulin signaling-related Akt phosphorylation, IRS1 expression and mitochondrial respiratory chain ATP5A. In conclusion, our results suggest that the FLG-induced TLR5 activation in adipocytes increases glycerol secretion from adipocytes and decreases insulin signaling and mitochondrial functions, and increases fat accumulation in hepatocytes. These mechanisms could, at least partly, explain the adipose tissue TLR5 expression associated with liver fat content in humans.     

Assessment of the efficiency of different control programs to reduce Trioza apicalis Först. (Triozidae: Hemiptera) feeding damage and the spread of “Candidatus Liberibacter solanacearum” on carrots (Daucus carota ssp. sativus L.)

The control of carrot psyllid Trioza apicalis Förster largely relies on chemical measures, and the current integrated pest management (IPM) strategy is based on pest scouting. The number of active ingredients available for psyllid control will further decline in the coming years. The need for alternative control measures is therefore urgent. In this work the efficiency of different control programs including a kaolin particle film and plant-derived, crude saponin extract, chemical control, insect net and IPM (kaolin in combination with insecticides) programs to reduce psyllid feeding damage, reproduction and the spread of “Candidatus Liberibacter solanacearum” (CLso) in carrots was studied. Each year in 2016–2018, four replicates of each treatment were randomised in a row-column design on a commercial carrot farm. After the treatments were executed, the psyllid nymphs and eggs were counted. At the harvest, the carrot roots and shoots were weighed, damages assessed, and samples were taken for CLso detection from 50 plants at each replicate. Kaolin treatment alone and in combination with insecticides effectively reduced the number of psyllid nymphs and eggs in all the years studied. Saponin was applied only on the first year, since it significantly increased the number of T. apicalis eggs compared to other treatments. The insect net was superior to other treatments in all the studied aspects in all the years. Under normal weather conditions, the highest root weight was harvested under the insect net, followed by the chemical control program consisting of pyrethroids, kaolin treatment, untreated control and saponin treatment. During extreme weather conditions, chemical control programs were not effective at protecting the carrots from psyllid feeding, which was reflected as low root yield. In all years, the carrot leaf damage percent negatively correlated with the root weight. Similarly, the shoot:root ratio increased as the leaf-curling percentage rose, which was even pronounced under drought stress. The effect of climatic stress should be considered when developing IPM strategies.     

Systematic screening for genetic polymorphism in human platelet glycoprotein Ibalpha

 Glycoprotein Ib_alpha (GP Ibα; CD 42b; hereafter GPIBA) is a component of the cell surface receptor for the von Willebrand factor (vWf) on platelets. Immunizations against various platelet surface antigens play a major role in neonatal alloimmune thrombocytopenia and in post-transfusion purpura. Only one antigenic polymorphism in GPIBA has thus far been established: the HPA-2 (Ko) alloantigen system. To screen other polymorphisms in GPIBA systematically, we analyzed the whole coding sequence of the GPIBA gene in 50 Finnish blood donors using the single-strand conformation polymorphism method. In addition to the known polymorphisms, we detected three others. Sequencing of the gene segments carrying the new polymorphisms revealed that none of them changed the predicted amino acid sequence. Polymorphism designated RS was located five base pairs upstream from the initiation codon at position 3064 and had the gene frequency of 16% for R and 84% for S, respectively, in the Finnish population, and it was detectable by the restriction enzyme Hae III. The EF polymorphism was at position 3842 (Asn242) and the gene frequencies were 97% for E and 3% for F. The KL polymorphism was at position 4142 (Arg342) and the gene frequencies were 98% for K and 2% for L. The five polymorphic positions in GPIBA formed altogether six different alleles of the gene. The data suggest that there are only a few variable amino acids in GPIBA. Received: 16 January 1996 / Revised: 21 March 1996     

The invasive herb Lupinus polyphyllus can reduce plant species richness independently of local invasion age

Biological Invasions - The ecological impacts of invasive species may change or accumulate with time since local invasion, potentially inducing further changes in communities and the abiotic...     

Acquisition of complement factor H is important for pathogenesis of Streptococcus pyogenes infections: evidence from bacterial in vitro survival and human genetic association

Streptococcus pyogenes (or group A streptococcus [GAS]) is a major human pathogen causing infections, such as tonsillitis, erysipelas, and sepsis. Several GAS strains bind host complement regulator factor H (CFH) via its domain 7 and, thereby, evade complement attack and C3b-mediated opsonophagocytosis. Importance of CFH binding for survival of GAS has been poorly studied because removal of CFH from plasma or blood causes vigorous complement activation, and specific inhibitors of the interaction have not been available. In this study, we found that activation of human complement by different GAS strains (n = 38) correlated negatively with binding of CFH via its domains 5-7. The importance of acquisition of host CFH for survival of GAS in vitro was studied next by blocking the binding with recombinant CFH5-7 lacking the regulatory domains 1-4. Using this fragment in full human blood resulted in death or radically reduced multiplication of all of the studied CFH-binding GAS strains. To study the importance of CFH binding in vivo (i.e., for pathogenesis of streptococcal infections), we used our recent finding that GAS binding to CFH is diminished in vitro by polymorphism 402H, which is also associated with age-related macular degeneration. We showed that allele 402H is suggested to be associated with protection from erysipelas (n = 278) and streptococcal tonsillitis (n = 209) compared with controls (n = 455) (p < 0.05). Taken together, the bacterial in vitro survival data and human genetic association revealed that binding of CFH is important for pathogenesis of GAS infections and suggested that inhibition of CFH binding can be a novel therapeutic approach in GAS infections.     

Soluble polyamines in Salix myrsinifolia and S. myrsinites × S. myrsinifolia plantlets exposed to increased UV-B irradiation and decreased watering

Hybridisation between certain willow species is a common feature leading to novel genotypes varying in growth rate and stress tolerance. The objective of this 4-week study was to investigate the effects of decreased watering, enhanced ultraviolet-B irradiation (UV-B_BE, 280–315 nm, 7.2 kJ m⁻² day⁻¹) and combined decreased watering and enhanced UV-B irradiation on di- and polyamines in the leaves of Salix myrsinifolia and its hybrid with S. myrsinites. Control plantlets were well-watered and exposed to ambient UV-B irradiation (UV-B_BE, 3.6 kJ m⁻² day⁻¹). HPLC analyses showed that the constitutive concentrations of soluble di- and polyamines varied markedly between S. myrsinifolia and its hybrids. The degree of responses to treatments also varied: in S. myrsinifolia, concentrations of free putrescine were clearly increased by reduced watering, while in the hybrid willow, change in putrescine was less pronounced and not significant. Results also showed that the increase in putrescine in S. myrsinifolia by reduced watering was mitigated by concurrent enhancement of UV-B irradiation. There were no direct UV-B effects on the soluble polyamines.     

L-galactonate dehydratase is part of the fungal path for D-galacturonic acid catabolism

An L-galactonate dehydratase and the corresponding gene were identified from the mould Hypocrea jecorina (Trichoderma reesei). This novel enzyme converts L-galactonate to L-threo-3-deoxy-hexulosonate (2-keto-3-deoxy-L-galactonate). The enzyme is part of the fungal pathway for D-galacturonic acid catabolism, a pathway which is only partly known. It is the second enzyme of this pathway after the D-galacturonic acid reductase. L-galactonate dehydratase activity is present in H. jecorina cells grown on D-galacturonic acid but absent when other carbon sources are used for growth. A deletion of the L-galactonate dehydratase gene in H. jecorina results in a strain with no growth on D-galacturonic acid. The active enzyme was produced in the heterologous host Saccharomyces cerevisiae and characterized. It exhibited activity with L-galactonate and D-arabonate where the hydroxyl group of the C2 is in L- and the hydroxyl group of the C3 is in D-configuration in the Fischer projection. However, it did not exhibit activity with D-galactonate, D-gluconate, L-gulonate or D-xylonate where the hydroxyl groups of the C2 and C3 are in different configuration.     

Characterization of a Novel Flavivirus from Mosquitoes in Northern Europe That Is Related to Mosquito-Borne Flaviviruses of the Tropics

A novel flavivirus was isolated from mosquitoes in Finland, representing the first mosquito-borne flavivirus from Northern Europe. The isolate, designated Lammi virus (LAMV), was antigenically cross-reactive with other flaviviruses and exhibited typical flavivirus morphology as determined by electron microscopy. The genomic sequence of LAMV was highly divergent from the recognized flaviviruses, and yet the polyprotein properties resembled those of mosquito-borne flaviviruses. Phylogenetic analysis of the complete coding sequence showed that LAMV represented a distinct lineage related to the Aedes sp.-transmitted human pathogenic flaviviruses, similarly to the newly described Nounané virus (NOUV), a flavivirus from Africa (S. Junglen et al., J. Virol. 83:4462-4468, 2009). Despite the low sequence homology, LAMV and NOUV were phylogenetically grouped closely, likely representing separate species of a novel group of flaviviruses. Despite the biological properties preferring replication in mosquito cells, the genetic relatedness of LAMV to viruses associated with vertebrate hosts warrants a search for disease associations.The genus Flavivirus in the family Flaviviridae consists of 53 recognized virus species that are enveloped, positive-sense single-stranded RNA viruses. The virion consists of three structural proteins: capsid (C), membrane (M), and envelope (E). In addition, seven nonstructural proteins are present in infected cells (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5). Based on their antigenic properties and vector associations, flaviviruses have been grouped into mosquito-borne, tick-borne, and no-known-vector viruses and have been isolated from vertebrates, bats, and rodents (15, 25). The grouping of flaviviruses according to their transmission mode is strongly supported by phylogenetic analyses of their genomic sequences (9, 18, 31).Mosquito-borne flaviviruses are a large and divergent group of viruses that can be differentiated phylogenetically into those associated either with encephalitic disease and transmission by Culex spp. mosquitoes or with diseases with hemorrhagic complications and transmission by Aedes spp. (18). Seven groups of mosquito-borne flaviviruses, namely, the Aroa, dengue, Japanese encephalitis, Kokobera, Ntaya, Spondweni, and yellow fever virus groups are recognized (15, 25). These groups include important animal and human pathogens such as dengue virus (DENV), West Nile virus (WNV), Japanese encephalitis virus (JEV), and yellow fever virus (YFV).Unclassified insect flaviviruses that have no recognized association with vertebrates have been isolated from a variety of mosquito species and also from mosquito cell lines. These insect flaviviruses do not appear to infect vertebrate cells and are not associated with human or animal disease. The cell fusing agent virus (CFAV), a tentative species in the genus Flavivirus, was the first of these insect viruses to be characterized (5, 40), Although CFAV was originally identified in cultured mosquito cells, it was later isolated from mosquitoes collected in Puerto Rico (7). This as-yet-unclassified insect flavivirus group now also includes Kamiti river virus (KRV) isolated in Kenya (10, 38) and a virus isolated from Culex spp. in Japan, designated culex flavivirus (22). In addition, related viral sequences or isolates have been recently reported from mosquitoes in Spain (1), the United States and Trinidad (26), and Mexico (14). Moreover, the identification of flaviviruslike sequences integrated within the genomes of Aedes mosquitoes further complicates the evolutionary history of the flaviviruses. These sequences, currently referred to as cell silent agent are genetically most closely related to CFAV and possibly share common evolutionary origin (11). Phylogenetically, the insect viruses form a divergent outgroup that may represent a primordial flavivirus lineage. Apart from the insect flaviviruses, the other recently discovered novel flaviviruses represent highly divergent lineages, such as Tamana bat virus (13), and Ngoye virus (20). Recently, a novel flavivirus, Nounané virus (NOUV) was isolated from a novel mosquito vector species, Uranotaenia mashonaensis in Côte d''Ivoire (23), and was shown to be phylogenetically related to the human pathogenic mosquito-borne flaviviruses.Several arboviruses have been reported from Northern Europe including the flavivirus tick-borne encephalitis virus (24, 36) but, to date, no mosquito-borne flaviviruses have been isolated. Our aim was to screen for arboviruses in Finland by studying mosquitoes using virus isolation and subsequent arbovirus antigen detection, which resulted in the identification of a novel flavivirus. We present here the isolation and characterization of this isolate, designated Lammi virus (LAMV), and discuss the implications of our findings.