SNARE proteins mediate fusion between cytosolic lipid droplets and are implicated in insulin sensitivity

The accumulation of cytosolic lipid droplets in muscle and liver cells has been linked to the development of insulin resistance and type 2 diabetes. Such droplets are formed as small structures that increase in size through fusion, a process that is dependent on intact microtubules and the motor protein dynein. Approximately 15% of all droplets are involved in fusion processes at a given time. Here, we show that lipid droplets are associated with proteins involved in fusion processes in the cell: NSF (N-ethylmaleimide-sensitive-factor), alpha-SNAP (soluble NSF attachment protein) and the SNAREs (SNAP receptors), SNAP23 (synaptosomal-associated protein of 23 kDa), syntaxin-5 and VAMP4 (vesicle-associated membrane protein 4). Knockdown of the genes for SNAP23, syntaxin-5 or VAMP4, or microinjection of a dominant-negative mutant of alpha-SNAP, decreases the rate of fusion and the size of the lipid droplets. Thus, the SNARE system seems to have an important role in lipid droplet fusion. We also show that oleic acid treatment decreases the insulin sensitivity of heart muscle cells, and this sensitivity is completely restored by transfection with SNAP23. Thus, SNAP23 might be a link between insulin sensitivity and the inflow of fatty acids to the cell.     

Some highlights of research on aging with invertebrates, 2006-2007

The invertebrate model organisms continue to be engines of discovery in aging research. Recent work with Drosophila stem cells has thrown light on their human equivalents, and on the role of stem cells and their niches in the decline in fecundity with age. Inspired by observations of aging in bacteria and yeast, a new theoretical study has revealed evolutionary forces that could favour asymmetry in the distribution of damaged cell constituents at division, and hence pave the way for the evolution of aging and selective maintenance of integrity of the germ line. Mechanisms of nutrient sensing and cell signalling in the response of lifespan to dietary restriction have been elucidated. Powerful invertebrate models of human aging-related disease have been produced, and used to start to understand how the aging process acts as a risk factor for disease. In the near future, studies of invertebrate aging are likely to move away from an exclusive reliance on genetic manipulation towards a more biochemical and physiological understanding of these systems.     

The phosphofructokinase-B (MJ0406) from <Emphasis Type="Italic">Methanocaldococcus jannaschii</Emphasis> represents a nucleoside kinase with a broad substrate specificity

Recently, unusual non-regulated ATP-dependent 6-phosphofructokinases (PFK) that belong to the PFK-B family have been described for the hyperthermophilic archaea Desulfurococcus amylolyticus and Aeropyrum pernix. Putative homologues were found in genomes of several archaea including the hyperthermophilic archaeon Methanocaldococcus jannaschii. In this organism, open reading frame MJ0406 had been annotated as a PFK-B sugar kinase. The gene encoding MJ0406 was cloned and functionally expressed in Escherichia coli. The purified recombinant enzyme is a homodimer with an apparent molecular mass of 68 kDa composed of 34 kDa subunits. With a temperature optimum of 85°C and a melting temperature of 90°C, the M. jannaschii nucleotide kinase represents one of the most thermoactive and thermostable members of the PFK-B family described so far. The recombinant enzyme was characterized as a functional nucleoside kinase rather than a 6-PFK. Inosine, guanosine, and cytidine were the most effective phosphoryl acceptors. Besides, adenosine, thymidine, uridin and xanthosine were less efficient. Extremely low activity was found with fructose-6-phosphate. Further, the substrate specificity of closely related PFK-Bs from D. amylolyticus and A. pernix were reanalysed.     

A long-term "memory" of HIF induction in response to chronic mild decreased oxygen after oxygen normalization

Background

Cardiovascular diseases (CVD) are the leading cause of death and the third cause of disability in Europe. Prevention programmes should include interventions aimed at a reduction of medical risk factors (hypertension, hypercholesterol, hyperglycemia, overweight and obesity) as well as behavioural risk factors (sedentary lifestyle, high fat intake and low fruit and vegetable intake, smoking). The aim of this study is to investigate the effects of a multifaceted, multidisciplinary electronic prevention programme on cardiovascular risk factors.

Methods/Design

In a randomized controlled trial, one group will receive a maximal intervention (= intervention group). The intervention group will be compared to the control group receiving a minimal intervention. An inclusion of 350 patients in total, with a follow-up of 3 years is foreseen. The inclusion criteria are age between 25–65 and insured by the Onderlinge Ziekenkas, insuring for guaranteed income in case of illness for self-employed. The maximal intervention group receives several prevention consultations by their general practitioner (GP) using a new type of cardiovascular risk calculator with personalised feedback on behavioural risk factors. These patients receive a follow-up with intensive support of health behaviour change via different methods, i.e. a tailored website and personal advice of a multidisciplinary team (psychologist, physiotherapist and dietician). The aim of this strategy is to reduce cardiovascular risk factors according to the guidelines. The primary outcome measures will be cardiovascular risk factors. The secondary outcome measures are cardiovascular events, quality of life, costs and incremental cost effectiveness ratios. The control group receives prevention consultations using a new type of cardiovascular risk calculator and general feedback.

Discussion

This trial incorporates interventions by GPs and other health professionals aiming at a reduction of medical and behavioural cardiovascular risk factors. An assessment of clinical, psychological and economical outcome measures will be performed.

Trial registration

ISRCTN23940498     

Multi‐scale habitat modification by coexisting ecosystem engineers drives spatial separation of macrobenthic functional groups

By changing habitat conditions, ecosystem engineers increase niche diversity and have profound effects on the distribution and abundances of other organisms. Although many ecosystems contain several engineering species, it is still unclear how the coexistence of multiple engineers affects the physical habitat and the structure of the community on a landscape scale. Here, we investigated through a large‐scale field manipulation how three coexisting engineers on intertidal flats (cockles Cerastoderma edule; lugworms Arenicola marina; blue mussels Mytilus edulis) influence the functional composition of the local macrobenthic community and what the consequences are at the landscape level. By using biological trait analysis (BTA), we show that on the local scale biogenic changes in sediment accumulation and organic matter content translated into specific shifts in the distribution of functional traits within the community. At a landscape scale, the co‐occurrence of multiple ecosystem engineers resulted in the spatial separation of different functional groups, i.e. different functional groups dominated unique complementary habitats. Our results emphasize the role of co‐occurring multiple engineers in shaping natural communities, thus contributing to a better knowledge of community assembly rules. This understanding can profitably be used to improve ecosystem‐based management and conservation actions.     

Indirect Immunodetection of Fungal Fragments by Field Emission Scanning Electron Microscopy

Submicronic fungal fragments have been observed in in vitro aerosolization experiments. The occurrence of these particles has therefore been suggested to contribute to respiratory health problems observed in mold-contaminated indoor environments. However, the role of submicronic fragments in exacerbating adverse health effects has remained unclear due to limitations associated with detection methods. In the present study, we report the development of an indirect immunodetection assay that utilizes chicken polyclonal antibodies developed against spores from Aspergillus versicolor and high-resolution field emission scanning electron microscopy (FESEM). Immunolabeling was performed with A. versicolor fragments immobilized and fixed onto poly-l-lysine-coated polycarbonate filters. Ninety percent of submicronic fragments and 1- to 2-μm fragments, compared to 100% of >2-μm fragments generated from pure freeze-dried mycelial fragments of A. versicolor, were positively labeled. In proof-of-concept experiments, air samples collected from moldy indoor environments were evaluated using the immunolabeling technique. Our results indicated that 13% of the total collected particles were derived from fungi. This fraction comprises 79% of the fragments that were detected by immunolabeling and 21% of the spore particles that were morphologically identified. The methods reported in this study enable the enumeration of fungal particles, including submicronic fragments, in a complex heterogeneous environmental sample.