Accumulation of cholesterol precursors and plant sterols in human stenotic aortic valves

The pathogenesis of aortic valve stenosis (AS) is characterized by the accumulation of LDL-derived cholesterol in the diseased valves. Since LDL particles also contain plant sterols, we investigated whether plant sterols accumulate in aortic valve lesions. Serum samples were collected from 82 patients with severe AS and from 12 control subjects. Aortic valves were obtained from a subpopulation of 21 AS patients undergoing valve surgery and from 10 controls. Serum and valvular total cholesterol and noncholesterol sterols were measured by gas-liquid chromatography. Noncholesterol sterols, including both cholesterol precursors and sterols reflecting cholesterol absorption, were detected in serum samples and aortic valves. The higher the ratios to cholesterol of the cholesterol precursors and absorption markers in serum, the higher their ratios in the stenotic aortic valves (r=0.74, P<0.001 for lathosterol and r=0.88, P<0.001 for campesterol). The valvular ratio to cholesterol of lathosterol correlated negatively with the aortic valve area (r= -0.47, P=0.045), suggesting attenuation of cholesterol synthesis with increasing severity of AS. The higher the absorption of cholesterol, the higher the plant sterol contents in stenotic aortic valves. These findings suggest that local accumulation of plant sterols and cholesterol precursors may participate in the pathobiology of aortic valve disease.     

Serum lipidomics meets cardiac magnetic resonance imaging: profiling of subjects at risk of dilated cardiomyopathy

Dilated cardiomyopathy (DCM), characterized by left ventricular dilatation and systolic dysfunction, constitutes a significant cause for heart failure, sudden cardiac death or need for heart transplantation. Lamin A/C gene (LMNA) on chromosome 1p12 is the most significant disease gene causing DCM and has been reported to cause 7-9% of DCM leading to cardiac transplantation. We have previously performed cardiac magnetic resonance imaging (MRI) to LMNA carriers to describe the early phenotype. Clinically, early recognition of subjects at risk of developing DCM would be important but is often difficult. Thus we have earlier used the MRI findings of these LMNA carriers for creating a model by which LMNA carriers could be identified from the controls at an asymptomatic stage. Some LMNA mutations may cause lipodystrophy. To characterize possible effects of LMNA mutations on lipid profile, we set out to apply global serum lipidomics using Ultra Performance Liquid Chromatography coupled to mass spectrometry in the same LMNA carriers, DCM patients without LMNA mutation and controls. All DCM patients, with or without LMNA mutation, differed from controls in regard to distinct serum lipidomic profile dominated by diminished odd-chain triglycerides and lipid ratios related to desaturation. Furthermore, we introduce a novel approach to identify associations between the molecular lipids from serum and the MR images from the LMNA carriers. The association analysis using dependency network and regression approaches also helped us to obtain novel insights into how the affected lipids might relate to cardiac shape and volume changes. Our study provides a framework for linking serum derived molecular markers not only with clinical endpoints, but also with the more subtle intermediate phenotypes, as derived from medical imaging, of potential pathophysiological relevance.     

The invasive herb <Emphasis Type="Italic">Lupinus polyphyllus</Emphasis> attracts bumblebees but reduces total arthropod abundance

Invasive plant species generally reduce the abundance and diversity of local plant species, which may translate into alterations at higher tropic levels, such as arthropods. Due to the diverse functional roles of arthropods in the ecosystems, it is critical to understand how arthropod communities are affected by plant invasions. Here, we investigated the impact of the invasive ornamental herb Lupinus polyphyllus (Lindl.) on arthropod communities during its main flowering period in southwestern Finland over two years. The total number of arthropods was about 46% smaller at the invaded sites than at the uninvaded sites in both study years, and this difference was mainly due to a lower abundance of beetles, Diptera, Lepidoptera, and ants. However, the number of bumblebees (particularly Bombus lucorum) was about twice as high at invaded sites compared with uninvaded sites, even though bumblebee richness did not differ between sites. There was no statistically significant difference between invaded and uninvaded sites in the abundances of the other arthropod groups considered (Hymenoptera (excluding bumblebees and ants), Hemiptera, and Arachnida). In addition, L. polyphyllus affected the relative abundance of four arthropod groups, with the order Lepidoptera being less common at invaded sites than at uninvaded sites, while the opposite was true for bumblebees, Hemiptera, and Arachnida. Overall, these results demonstrate that the negative impact of L. polyphyllus on biodiversity goes beyond its own trophic level, suggesting that this species has the potential to alter the abundance of different arthropod groups and, consequently, the structure of arthropod communities at a large scale.     

Engineering Filamentous Fungi for Conversion of d-Galacturonic Acid to l-Galactonic Acid

d-Galacturonic acid, the main monomer of pectin, is an attractive substrate for bioconversions, since pectin-rich biomass is abundantly available and pectin is easily hydrolyzed. l-Galactonic acid is an intermediate in the eukaryotic pathway for d-galacturonic acid catabolism, but extracellular accumulation of l-galactonic acid has not been reported. By deleting the gene encoding l-galactonic acid dehydratase (lgd1 or gaaB) in two filamentous fungi, strains were obtained that converted d-galacturonic acid to l-galactonic acid. Both Trichoderma reesei Δlgd1 and Aspergillus niger ΔgaaB strains produced l-galactonate at yields of 0.6 to 0.9 g per g of substrate consumed. Although T. reesei Δlgd1 could produce l-galactonate at pH 5.5, a lower pH was necessary for A. niger ΔgaaB. Provision of a cosubstrate improved the production rate and titer in both strains. Intracellular accumulation of l-galactonate (40 to 70 mg g biomass⁻¹) suggested that export may be limiting. Deletion of the l-galactonate dehydratase from A. niger was found to delay induction of d-galacturonate reductase and overexpression of the reductase improved initial production rates. Deletion of the l-galactonate dehydratase from A. niger also delayed or prevented induction of the putative d-galacturonate transporter An14g04280. In addition, A. niger ΔgaaB produced l-galactonate from polygalacturonate as efficiently as from the monomer.     

Multiple life stages with multiple replicated density levels are required to estimate density dependence for plants

Negative density dependence resulting from intraspecific competition can regulate plant populations by limiting demographic rates (survival, growth, fecundity). However, the strength of intraspecific competition can vary within and among populations due to spatial or temporal environmental heterogeneity, or genetic differences. Quantification of variation under a relatively constant environment is needed to assess the inherent potential for density dependence to vary. This knowledge will help adjust data collection effort required for parameterisation of density dependence. Our review of published plant demographic studies revealed that only half of the studies included the whole life‐cycle in the analysis of density dependence. Approximately half of the studies manipulated density, while the rest examined density dependence from observed densities in the field. Regardless of the design used, density dependence was estimated from a small number of replicates. To investigate inherent variation in density dependence during the life‐cycle, and the effect of low replication on density dependence estimates, we combined an experimental approach with simulations for an invasive herb Senecio madagascariensis. We found significant negative density dependence for five out of six examined demographic rates in a constant environment, with the strength of density dependence increasing during the life‐cycle. An exception was plant growth, in which the direction of density dependence varied from positive to negative depending on the life stage. Simulations showed substantial deviation for density dependence parameterised from a small number of replicates even when environmental variation was minimal. This suggests that data collection procedures currently used to assess the effect of density on plant demographic rates may produce inaccurate estimates, increasing uncertainty in demographic models. Due to variation in the direction and strength of density dependence during the life‐cycle, multiple life stages with multiple replicated density levels are required to parameterise density dependence for demographic rates.     

Small-scale spatial and temporal variation in the demographic processes underlying the large-scale decline of eiders in the Baltic Sea

The application of uniform conservation schemes often fails to account for small-scale spatial variation in the drivers of population decline. Demographic comparisons of imperilled populations across locations are therefore crucial for successful conservation, but progress is hampered by lack of long-term data from more than a single population. The recent large-scale decline of eider ducks (Somateria mollissima) in the Baltic Sea is ideal for determining to what extent mechanisms underlying population decline can be extrapolated over larger areas. We utilized stochastic demographic methods incorporating both environmental and sampling variation to assess small-scale spatial and temporal variation in the population dynamics of eiders at Söderskär (eastern range-margin) and Tvärminne (core breeding area), situated 130 km apart. The stochastic growth rate models accurately predicted the observed differences in the rate of decline between sites and time periods. At Söderskär, established breeder survival had by far the greatest elasticity, whereas elasticity was more evenly distributed among vital rates at Tvärminne. Although the study sites showed the single largest difference in fecundity, stochastic life table response experiment analyses revealed that reduced adult female survival at Tvärminne mainly determined the observed difference in growth rates between sites. In contrast, reduced fecundity primarily differentiated the past population increase from the present population decline at Söderskär. Our results demonstrate that different mechanisms may be associated with population decline across adjacent geographic locations, and indicate that dispersal of first-time breeders may be important for population dynamics. Safeguarding adult female survival and/or fecundity should be prioritized in management efforts.     

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.     

Crosstalk between Jagged1 and GDNF/Ret/GFRalpha1 signalling regulates ureteric budding and branching

Glial-Cell-Line-Derived Neurotrophic Factor (GDNF) is the major mesenchyme-derived regulator of ureteric budding and branching during nephrogenesis. The ligand activates on the ureteric bud epithelium a receptor complex composed of Ret and GFRalpha1. The upstream regulators of the GDNF receptors are poorly known. A Notch ligand, Jagged1 (Jag1), co-localises with GDNF and its receptors during early kidney morphogenesis. In this study we utilized both in vitro and in vivo models to study the possible regulatory relationship of Ret and Notch pathways. Urogenital blocks were exposed to exogenous GDNF, which promotes supernumerary ureteric budding from the Wolffian duct. GDNF-induced ectopic buds expressed Jag1, which suggests that GDNF can, directly or indirectly, up-regulate Jag1 through Ret/GFRalpha1 signalling. We then studied the role of Jag1 in nephrogenesis by transgenic mice constitutively expressing human Jag1 in Wolffian duct and its derivatives under HoxB7 promoter. Jag1 transgenic mice showed a spectrum of renal defects ranging from aplasia to hypoplasia. Ret and GFRalpha1 are normally downregulated in the Wolffian duct, but they were persistently expressed in the entire transgenic duct. Simultaneously, GDNF expression remained unexpectedly low in the metanephric mesenchyme. In vitro, exogenous GDNF restored the budding and branching defects in transgenic urogenital blocks. Renal differentiation apparently failed because of perturbed stimulation of primary ureteric budding and subsequent branching. Thus, the data provide evidence for a novel crosstalk between Notch and Ret/GFRalpha1 signalling during early nephrogenesis.