Postprandial but not fasting insulin resistance is an early identifier of dysmetabolism in overweight subjects

The dynamic response to insulin is highly potentiated after meal ingestion, and this meal-induced insulin sensitization (MIS) in healthy subjects is dependent on cholinergic mechanisms. The main objective of this study was to test the hypothesis that the reduced response to insulin observed in moderately overweight subjects, in comparison with control lean subjects, is due to MIS impairment and not to a reduction in the direct hypoglycemic action of insulin. Both lean and overweight male subjects were recruited. Insulin sensitivity (IS) was assessed by the rapid insulin sensitivity test (RIST) performed after a 24 h fast, as well as after a standardized meal. Fasting glucose disposal was similar between lean and overweight subjects. Following the meal, glucose disposal increased more extensively in lean than overweight subjects. The insulin profiles, in both fasted and fed states, were superimposable, suggesting that the absence of a factor other than insulin is responsible for the decreased postprandial insulin sensitivity observed in overweight subjects. Our data suggest that in overweight subjects, MIS contribution is decreased, which is responsible for the postprandial impaired IS observed and is suggested to be the cause, not effect, of mild adiposity.     

Insertional inactivation of the WT1 gene in tumour cells from a patient with WAGR syndrome

The WT1 gene was analysed using DNA from a Wilms' tumour derived from a patient with the WAGR syndrome using single strand conformation polymorphism analysis and polymerase chain reaction sequencing. A 14-bp insertion was found in the intron part of the splice donor site of exon 7 and was a tandem duplication of an upstream exon sequence. This mutation would be expected to disrupt the correct processing of the WT1 mRNA and is predicted to result in a non-functional protein. This observation further supports the role of WT1 in Wilms' tumorigenesis in patients with constitutional 11p13 deletions.     

Changes in ubiquitin and ubiquitin-protein conjugates during seed formation and germination

Changes in both free ubiquitin and ubiquitin-protein conjugateswere followed in cotyledons of lupin (Lupinus albus L.) duringthe course of seed formation, from the flower to the dry seed,and during germination and seedling growth, from the dry seedto the senescing cotyledons. The observed levels of ubiquitinconjugates, detected by immunoblotting using antiubiquitin antibodiesand by autoradiography using ¹²⁵I-labelled ubiquitin, suggestan intense involvement of the ubiquitin-mediated proteolyticpathway during the highly regulated phases of seed formationand germination. High amounts of free ubiquitin are presentat all stages in all tissues examined. With the exception ofthe dry seed, the high molecular mass ubiquitin-protein conjugatesare also present at all stages. Higher amounts of these conjugateswere found during the initial stages of pod development andseed germination and during the most active phases of storageprotein deposition and degradation. Germination and seedlinggrowth in total darkness not only delays the degradation ofthe storage proteins, but also extends the period characterizedby the presence of a high amount of these conjugates. No suchconjugates were detected in the dry seeds, probably reflectingthe extremely low metabolic activity observed in these organs.A number of smaller molecular mass polypeptides were also detectedat different stages of seed development, germination and seedlinggrowth. Of particular interest is the abrupt accumulation ofan abundant 20 kDa polypeptide in the cotyledons during the4th day after imbibition, which is maintained in high amountsin these organs, rapidly declining after about 12–14 d.The pattern of accumulation of the 20 kDa polypeptide is controlledneither by light nor by the embryo axes, and large variationsin its concentration are observed during heat shock. Key words: Ubiquitin, ubiquitin-protein conjugates, seed storage proteins, protein synthesis, protein degradation     

Respiratory allergy to Blomia tropicalis: Immune response in four syngeneic mouse strains and assessment of a low allergen-dose,short-term experimental model

Background

The dust mite Blomia tropicalis is an important source of aeroallergens in tropical areas. Although a mouse model for B. tropicalis extract (BtE)-induced asthma has been described, no study comparing different mouse strains in this asthma model has been reported. The relevance and reproducibility of experimental animal models of allergy depends on the genetic background of the animal, the molecular composition of the allergen and the experimental protocol.

Objectives

This work had two objectives. The first was to study the anti-B. tropicalis allergic responses in different mouse strains using a short-term model of respiratory allergy to BtE. This study included the comparison of the allergic responses elicited by BtE with those elicited by ovalbumin in mice of the strain that responded better to BtE sensitization. The second objective was to investigate whether the best responder mouse strain could be used in an experimental model of allergy employing relatively low BtE doses.

Methods

Groups of mice of four different syngeneic strains were sensitized subcutaneously with 100 μg of BtE on days 0 and 7 and challenged four times intranasally, at days 8, 10, 12, and 14, with 10 μg of BtE. A/J mice, that were the best responders to BtE sensitization, were used to compare the B. tropicalis-specific asthma experimental model with the conventional experimental model of ovalbumin (OVA)-specific asthma. A/J mice were also sensitized with a lower dose of BtE.

Results

Mice of all strains had lung inflammatory-cell infiltration and increased levels of anti-BtE IgE antibodies, but these responses were significantly more intense in A/J mice than in CBA/J, BALB/c or C57BL/6J mice. Immunization of A/J mice with BtE induced a more intense airway eosinophil influx, higher levels of total IgE, similar airway hyperreactivity to methacholine but less intense mucous production, and lower levels of specific IgE, IgG1 and IgG2 antibodies than sensitization with OVA. Finally, immunization with a relatively low BtE dose (10 μg per subcutaneous injection per mouse) was able to sensitize A/J mice, which were the best responders to high-dose BtE immunization, for the development of allergy-associated immune and lung inflammatory responses.

Conclusions

The described short-term model of BtE-induced allergic lung disease is reproducible in different syngeneic mouse strains, and mice of the A/J strain was the most responsive to it. In addition, it was shown that OVA and BtE induce quantitatively different immune responses in A/J mice and that the experimental model can be set up with low amounts of BtE.     

Rats go genomic

A report on the meeting 'Rat Genomics and Models', Cold Spring Harbor, USA, 8-11 December 2005.