Revascularisation of type 2 diabetics with coronary artery disease: Insights and therapeutic targeting of O-GlcNAcylation

AIM

Coronary artery bypass graft (CABG) using autologous saphenous vein continues to be a gold standard procedure to restore the supply of oxygen-rich blood to the heart muscles in coronary artery disease (CAD) patients with or without type 2 diabetes mellitus (T2DM). However, CAD patients with T2DM are at higher risk of graft failure. While failure rates have been reduced through improvements in procedure-related factors, much less is known about the molecular and cellular mechanisms by which T2DM initiates vein graft failure. This review gives novel insights into these cellular and molecular mechanisms and identifies potential therapeutic targets for development of new medicines to improve vein graft patency.

DATA SYNTHESIS

One important cellular process that has been implicated in the pathogenesis of T2DM is protein O-GlcNAcylation, a dynamic, reversible post-translational modification of serine and threonine residues on target proteins that is controlled by two enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Protein O-GlcNAcylation impacts a range of cellular processes, including trafficking, metabolism, inflammation and cytoskeletal organisation. Altered O-GlcNAcylation homeostasis have, therefore, been linked to a range of human pathologies with a metabolic component, including T2DM.

CONCLUSION

We propose that protein O-GlcNAcylation alters vascular smooth muscle and endothelial cell function through modification of specific protein targets which contribute to the vascular re-modelling responsible for saphenous vein graft failure in T2DM.

Emerging roles of protein O-GlcNAcylation in cardiovascular diseases: Insights and novel therapeutic targets

Cardiovascular diseases (CVDs) are the leading cause of death globally. While the major focus of pharmacological and non-pharmacological interventions has been on targeting disease pathophysiology and limiting predisposing factors, our understanding of the cellular and molecular mechanisms underlying the pathogenesis of CVDs remains incomplete. One mechanism that has recently emerged is protein O-GlcNAcylation. This is a dynamic, site-specific reversible post-translational modification of serine and threonine residues on target proteins and is controlled by two enzymes: O-linked β-N-acetylglucosamine transferase (OGT) and O-linked β-N-acetylglucosaminidase (OGA). Protein O-GlcNAcylation alters the cellular functions of these target proteins which play vital roles in pathways that modulate vascular homeostasis and cardiac function. Through this review, we aim to give insights on the role of protein O-GlcNAcylation in cardiovascular diseases and identify potential therapeutic targets in this pathway for development of more effective medicines to improve patient outcomes.

Loss of CRMP2 O-GlcNAcylation leads to reduced novel object recognition performance in mice

O-GlcNAcylation is an abundant post-translational modification in the nervous system, linked to both neurodevelopmental and neurodegenerative disease. However, the mechanistic links between these phenotypes and site-specific O-GlcNAcylation remain largely unexplored. Here, we show that Ser517 O-GlcNAcylation of the microtubule-binding protein Collapsin Response Mediator Protein-2 (CRMP2) increases with age. By generating and characterizing a Crmp2S517A knock-in mouse model, we demonstrate that loss of O-GlcNAcylation leads to a small decrease in body weight and mild memory impairment, suggesting that Ser517 O-GlcNAcylation has a small but detectable impact on mouse physiology and cognitive function.

Local Hemodynamic Conditions Associated with Focal Changes in the Intracranial Aneurysm Wall

BACKGROUND AND PURPOSE

Aneurysm hemodynamics has been associated with wall histology and inflammation. We investigated associations between local hemodynamics and focal wall changes visible intraoperatively.

MATERIALS AND METHODS

Computational fluid dynamics models were constructed from 3D images of 65 aneurysms treated surgically. Aneurysm regions with different visual appearances were identified in intraoperative videos: 1) "atherosclerotic" (yellow), 2) "hyperplastic" (white), 3) "thin" (red), 4) rupture site, and 5) "normal" (similar to parent artery), They were marked on 3D reconstructions. Regional hemodynamics was characterized by the following: wall shear stress, oscillatory shear index, relative residence time, wall shear stress gradient and divergence, gradient oscillatory number, and dynamic pressure; these were compared using the Mann-Whitney test.

RESULTS

Hyperplastic regions had lower average wall shear stress (P = .005) and pressure (P = .009) than normal regions. Flow conditions in atherosclerotic and hyperplastic regions were similar but had higher average relative residence time (P = .03) and oscillatory shear index (P = .04) than thin regions. Hyperplastic regions also had a higher average gradient oscillatory number (P = .002) than thin regions. Thin regions had lower average relative residence time (P < .001), oscillatory shear index (P = .006), and gradient oscillatory number (P < .001) than normal regions, and higher average wall shear stress (P = .006) and pressure (P = .009) than hyperplastic regions. Thin regions tended to be aligned with the flow stream, while atherosclerotic and hyperplastic regions tended to be aligned with recirculation zones.

CONCLUSIONS

Local hemodynamics is associated with visible focal wall changes. Slow swirling flow with low and oscillatory wall shear stress was associated with atherosclerotic and hyperplastic changes. High flow conditions prevalent in regions near the flow impingement site characterized by higher and less oscillatory wall shear stress were associated with local "thinning" of the wall.

Basal fatty acid oxidation increases after recurrent low glucose in human primary astrocytes

AIMS/HYPOTHESIS

Hypoglycaemia is a major barrier to good glucose control in type 1 diabetes. Frequent hypoglycaemic episodes impair awareness of subsequent hypoglycaemic bouts. Neural changes underpinning awareness of hypoglycaemia are poorly defined and molecular mechanisms by which glial cells contribute to hypoglycaemia sensing and glucose counterregulation require further investigation. The aim of the current study was to examine whether, and by what mechanism, human primary astrocyte (HPA) function was altered by acute and recurrent low glucose (RLG).

METHODS

To test whether glia, specifically astrocytes, could detect changes in glucose, we utilised HPA and U373 astrocytoma cells and exposed them to RLG in vitro. This allowed measurement, with high specificity and sensitivity, of RLG-associated changes in cellular metabolism. We examined changes in protein phosphorylation/expression using western blotting. Metabolic function was assessed using a Seahorse extracellular flux analyser. Immunofluorescent imaging was used to examine cell morphology and enzymatic assays were used to measure lactate release, glycogen content, intracellular ATP and nucleotide ratios.

RESULTS

AMP-activated protein kinase (AMPK) was activated over a pathophysiologically relevant glucose concentration range. RLG produced an increased dependency on fatty acid oxidation for basal mitochondrial metabolism and exhibited hallmarks of mitochondrial stress, including increased proton leak and reduced coupling efficiency. Relative to glucose availability, lactate release increased during low glucose but this was not modified by RLG. Basal glucose uptake was not modified by RLG and glycogen levels were similar in control and RLG-treated cells. Mitochondrial adaptations to RLG were partially recovered by maintaining euglycaemic levels of glucose following RLG exposure.

CONCLUSIONS/INTERPRETATION

Taken together, these data indicate that HPA mitochondria are altered following RLG, with a metabolic switch towards increased fatty acid oxidation, suggesting glial adaptations to RLG involve altered mitochondrial metabolism that could contribute to defective glucose counterregulation to hypoglycaemia in diabetes.

Responsiveness to oral prednisolone in severe asthma is related to the degree of eosinophilic airway inflammation

BACKGROUND

Patients with severe asthma appear relatively corticosteroid resistant. Corticosteroid responsiveness is closely related to the degree of eosinophilic airway inflammation. The extent to which eosinophilic airway inflammation in severe asthma responds to treatment with systemic corticosteroids is not clear.

OBJECTIVE

To relate the physiological and inflammatory response to systemic corticosteroids in asthma to disease severity and the baseline extent of eosinophilic inflammation.

METHODS

Patients with mild/moderate and severe asthma were investigated before and after 2 weeks of oral prednisolone (Clintrials.gov NCT00331058 and NCT00327197). We pooled the results from two studies with common protocols. The US study contained two independent centres and the UK one independent centre. The effect of oral corticosteroids on FEV₁ , Pc20, airway inflammation and serum cytokines was investigated. Baseline measurements were compared with healthy subjects.

RESULTS

Thirty-two mild/moderate asthmatics, 50 severe asthmatics and 35 healthy subjects took part. At baseline, both groups of asthmatics had a lower FEV₁ and Pc20 and increased eosinophilic inflammation compared to healthy subjects. The severe group had a lower FEV₁ and more eosinophilic inflammation compared to mild/moderate asthmatics. Oral prednisolone caused a similar degree of suppression of eosinophilic inflammation in all compartments in both groups of asthmatics. There were small improvements in FEV₁ and Pc20 for both mild/ moderate and severe asthmatics with a correlation between the baseline eosinophilic inflammation and the change in FEV₁ . There was a ~50% reduction in the serum concentration of CXCL10 (IP-10), CCL22 (MDC), CCL17 (TARC), CCL-2 (MCP-1) and CCL-13 (MCP-4) in both asthma groups after oral corticosteroids.

CONCLUSIONS AND CLINICAL RELEVANCE

Disease severity does not influence the response to systemic corticosteroids. The study does not therefore support the concept that severe asthma is associated with corticosteroid resistance. Only baseline eosinophilic inflammation was associated with the physiological response to corticosteroids, confirming the importance of measuring eosinophilic inflammation to guide corticosteroid use.

A mutant O-GlcNAcase enriches Drosophila developmental regulators

Protein O-GlcNAcylation is a reversible post-translational modification of serines and threonines on nucleocytoplasmic proteins. It is cycled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (O-GlcNAcase or OGA). Genetic approaches in model organisms have revealed that protein O-GlcNAcylation is essential for early embryogenesis. The Drosophila melanogaster gene supersex combs (sxc), which encodes OGT, is a polycomb gene, whose null mutants display homeotic transformations and die at the pharate adult stage. However, the identities of the O-GlcNAcylated proteins involved and the underlying mechanisms linking these phenotypes to embryonic development are poorly understood. Identification of O-GlcNAcylated proteins from biological samples is hampered by the low stoichiometry of this modification and by limited enrichment tools. Using a catalytically inactive bacterial O-GlcNAcase mutant as a substrate trap, we have enriched the O-GlcNAc proteome of the developing Drosophila embryo, identifying, among others, known regulators of Hox genes as candidate conveyors of OGT function during embryonic development.

Clinical characteristics and airway inflammation profile of COPD persistent sputum producers

BACKGROUND

COPD patients with chronic bronchitis include a subgroup with persistent sputum production on most or every day. We hypothesized that COPD patients with persistent sputum production have a different profile of airway inflammation, and more severe clinical characteristics.

OBJECTIVE

To compare the airway inflammation profile and clinical characteristics of COPD persistent and non-persistent sputum producers.

METHODS

COPD persistent sputum producers (n = 26) and non-persistent sputum producers (n = 26) underwent sputum induction and pulmonary function tests. Exacerbation history was recorded; the St. George's Respiratory Questionnaire, Modified Medical Research Council Dyspnoea scale and COPD Assessment Tool were completed. 33 COPD patients provided sputum for bacteriology.

RESULTS

Persistent sputum producers had lower post-bronchodilator FEV1% predicted (p = 0.01), diffusion capacity (p = 0.04), 6 min walk test distance (p = 0.05), and higher closing volume (p = 0.01), BODE index (p = 0.01), rate of bacterial colonization (p = 0.004) and exacerbations (p = 0.03) compared to non-persistent sputum producers. The mean SGRQ and CAT scores were higher in persistent sputum producers (p = 0.01 and 0.03 respectively). Sputum neutrophil and eosinophil total cell counts were higher in persistent sputum producers (p = 0.02 and 0.05 respectively). Sputum levels of eotaxin (p = 0.02), MCP-1 (p = 0.02), TNF-α (p = 0.03) and IL-6 (p = 0.05) were higher in persistent sputum producers.

CONCLUSION

COPD persistent sputum producers have more severe clinical characteristics and increased concentrations of some inflammatory mediators in the airways.

Radiological predictors of cytoreductive outcomes in patients with advanced ovarian cancer

OBJECTIVE

To assess site of disease on preoperative computed tomography (CT) to predict surgical debulking in patients with ovarian cancer.

DESIGN

Two-phase retrospective cohort study.

SETTING

West London Gynaecological Cancer Centre, UK.

POPULATION

Women with stage 3 or 4, ovarian, fallopian or primary peritoneal cancer undergoing cytoreductive surgery.

METHODS

Preoperative CT images were reviewed by experienced radiologists to assess the presence or absence of disease at predetermined sites. Multivariable stepwise logistic regression models determined sites of disease which were significantly associated with surgical outcomes in the test (n = 111) and validation (n = 70) sets.

MAIN OUTCOME MEASURES

Sensitivity and specificity of CT in predicting surgical outcome.

RESULTS

Stepwise logistic regression identified that the presence of lung metastasis, pleural effusion, deposits on the large-bowel mesentery and small-bowel mesentery, and infrarenal para-aortic nodes were associated with debulking status. Logistic regression determined a surgical predictive score which was able to significantly predict suboptimal debulking (n = 94, P = 0.0001) with an area under the curve (AUC) of 0.749 (95% confidence interval [95% CI]: 0.652, 0.846) and a sensitivity of 69.2%, specificity of 71.4%, positive predictive value of 75.0% and negative predictive value of 65.2%. These results remained significant in a recent validation set. There was a significant difference in residual disease volume in the test and validation sets (P < 0.001) in keeping with improved optimal debulking rates.

CONCLUSIONS

The presence of disease at some sites on preoperative CT scan is significantly associated with suboptimal debulking and may be an indication for a change in surgical planning.

MRI appearances of benign uterine disease

Benign uterine disease is a common entity affecting women of all ages. Ultrasound has historically been the predominant imaging method used in the evaluation of benign gynaecological disease, magnetic resonance imaging (MRI) being reserved for use in the staging of malignant uterine and cervical disease. MRI is now increasingly used in the diagnosis of benign uterine disease as well as a tool for problem-solving in cases of diagnostic dilemma. It allows detailed assessment of benign conditions, such as endometrial lesions, leiomyomas, and adenomyosis, and can be helpful in the stratification of patients to different treatment modalities, including surgical resection, uterine artery embolization, and medical therapies. In this article, we review the MRI findings in the common benign uterine diseases.

A high-fat-diet-induced cognitive deficit in rats that is not prevented by improving insulin sensitivity with metformin

AIMS/HYPOTHESIS

We previously demonstrated that animals fed a high-fat (HF) diet for 10 weeks developed insulin resistance and behavioural inflexibility. We hypothesised that intervention with metformin would diminish the HF-feeding-evoked cognitive deficit by improving insulin sensitivity.

METHODS

Rats were trained in an operant-based matching and non-matching to position task (MTP/NMTP). Animals received an HF (45% of kJ as lard; n = 24), standard chow (SC; n = 16), HF + metformin (144 mg/kg in diet; n = 20) or SC + metformin (144 mg/kg in diet; n = 16) diet for 10 weeks before retesting. Body weight and plasma glucose, insulin and leptin were measured. Protein lysates from various brain areas were analysed for alterations in intracellular signalling or production of synaptic proteins.

RESULTS

HF-fed animals developed insulin resistance and an impairment in switching task contingency from matching to non-matching paradigm. Metformin attenuated the insulin resistance and weight gain associated with HF feeding, but had no effect on performance in either MTP or NMTP tasks. No major alteration in proteins associated with insulin signalling or synaptic function was detected in response to HF diet in the hypothalamus, hippocampus, striatum or cortex.

CONCLUSIONS/INTERPRETATION

Metformin prevented the metabolic but not cognitive alterations associated with HF feeding. The HF diet protocol did not change basal insulin signalling in the brain, suggesting that the brain did not develop insulin resistance. These findings indicate that HF diet has deleterious effects on neuronal function over and above those related to insulin resistance and suggest that weight loss may not be sufficient to reverse some damaging effects of poor diet.

Perioperative heparin-therapy inhibits late death from metastatic cancer

Low-dose heparin prophylaxis reduces postoperative death from fatal pulmonary embolism and its long-term anti-cancer effect has now been assessed in a retrospective study of 1250 patients, 336 of whom (30%) underwent operation for cancer. There was a striking reduction in three year mortality amongst those patients who received low dose heparin compared to unteated controls (7.6% vs. 12.5%, P=0.005). Death from disseminated malignancy was halved (9.2% vs. 21.4%). The mechanism remains unclear, but may reflect either the antithrombotic actions of heparin or a direct antitumour cell effect.

Localization of expression of fibroblast growth-factors and their receptors in pancreatic adenocarcinoma by in-situ hybridization

Growth factors may play a role in autocrine or paracrine growth control of tumour cells. We have now examined the expression pattern in vivo by in situ hybridization (ISH) on a series of 13 ductal adenocarcinomas of the pancreas using the non-radioactive digoxigenin system to generate specific antisense orientated riboprobes for FGF-1 and FGF-2, and the four FGFRs (FGFR-1, -2, -3 and -4). We confirmed the expression of both FGF/FGFR by tumour cells, with the potential of a potential autocrine loops in 46% of the cases studied. FGF-2 and FGFR-3 were the most commonly expressed ligand and receptor (46% and 76% respectively). Endothelial cells lining vessels within an around invasive tumours were frequently positive for expression of FGFR-1 and/or FGFR-3. In the normal pancreas remote from the tumour, the acinar cells were found to have a heterogeneous expression pattern for FGFRs while duct cells, islet cells and stromal components including nerves and vascular endothelium were negative. The data suggest a role for FGFs and their high affinity receptors in the control of growth of human pancreatic adenocarcinoma and its supporting stroma.

CRMP2 hyperphosphorylation is characteristic of Alzheimer's disease and not a feature common to other neurodegenerative diseases

Collapsin response mediator protein 2 (CRMP2) is an abundant brain-enriched protein that regulates neurite outgrowth. It is phosphorylated by Cdk5 and GSK3, and these modifications are abnormally high in the brains of Alzheimer's disease (AD) patients. Increased phosphorylation of CRMP2 is also apparent in mouse models of AD that express mutated AβPP and PSEN1, but not AβPP or tau alone, where it is detectable before the appearance of amyloid plaques and neurofibrillary tangles, suggesting it is an early event in AD pathogenesis. Here, we have extended these observations by showing that CRMP2 is not hyperphosphorylated in mice overexpressing mutated PSEN1 alone, or in cultured neurons treated with soluble, oligomeric Aβ42 peptide. Similarly, CRMP2 phosphorylation was not increased in a mouse model of severe neurodegeneration (PMSC-1 knockout) or in cultured neurons subjected to neurotoxic concentrations of NMDA or staurosporine. Most interestingly, CRMP2 phosphorylation was not increased in frontal cortex from patients with frontotemporal lobar degeneration associated with mutations in MAPT or with Pick bodies. Together, these observations are consistent with the hypothesis that abnormal phosphorylation of CRMP2 is specific to AD and occurs downstream of excessive processing of AβPP, but that neither excessive Aβ42 peptide nor neurotoxicity alone are sufficient to promote hyperphosphorylation.

Frequency multiplexed superconducting quantum interference device readout of large bolometer arrays for cosmic microwave background measurements

A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.

Insulin resistance in the brain: an old-age or new-age problem?

Life expectancy is rising however with more people living longer there is a concomitant rise in the incidence of dementia. In addition to age-related cognitive decline there is a higher risk of going on to develop vascular dementia and Alzheimer's disease associated with aspects of modern lifestyle. Most worryingly, recent data reports accelerated cognitive decline in adolescents associated with poor diet (high fat and calorie intake). Thus the increase in dementia in 'old-age' may have as much to do with 'new-age' lifestyle as it does with normal ageing. It would seem wise therefore to investigate the molecular connections between lifestyle and cognitive decline in more detail. Epidemiological evidence suggests an increased risk of developing dementia (including Alzheimer's disease) in individuals with obesity and type 2 diabetes but also in those with poor insulin sensitivity without diabetes, implicating a mechanistic link between adiposity, insulin sensitivity and dementia. Insulin receptors are expressed in the brain and physiological roles for insulin in the CNS are starting to be delineated. Indeed disrupted neuronal insulin action may underlie the link between diabetes and neurodegenerative disorders. This review discusses the difficulties in quantifying insulin sensitivity of the brain and why it is vital that we develop technology for this purpose so that we can establish its role in this 'new-age' dementia. This has particular relevance to the design and interpretation of clinical trials in progress to assess potential benefits of insulin and insulin sensitisers on prevention of cognitive decline.

Neuronal membranes are key to the pathogenesis of Alzheimer's disease: the role of both raft and non-raft membrane domains

Membrane rafts are sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts isolated from post-mortem AD brain are enriched in both β-amyloid and phosphorylated tau. Proteolytic processing of APP to generate β-amyloid, the principle component of amyloid plaques, can occur in membrane rafts, implicating them in the pathogenesis of Alzheimer's disease (AD). Secondary to their role in β-amyloid generation, membrane rafts have more recently been implicated in the accumulation, aggregation and degradation of β-amyloid, with evidence supporting a specific role for membrane raft gangliosides in the binding and aggregation of β-amyloid. In addition, membrane domain composition has a direct impact on both the generation of β-amyloid and its subsequent toxic actions and as such is a key target for the development of therapeutic strategies. This mini-review will focus on recent advances in our understanding of the relevance of membrane composition, of both raft and non-raft domains, to AD progression in models and in human disease. We will discuss how manipulation of membrane composition can alter both the proteolytic processing of APP and the subsequent binding and aggregation of β-amyloid peptide.

Tyrosine phosphorylation of tau regulates its interactions with Fyn SH2 domains, but not SH3 domains, altering the cellular localization of tau

Recent reports have demonstrated that interactions between the microtubule-associated protein tau and the nonreceptor tyrosine kinase Fyn play a critical role in mediating synaptic toxicity and neuronal loss in response to β-amyloid (Aβ) in models of Alzheimer's disease. Disruption of interactions between Fyn and tau may thus have the potential to protect neurons from Aβ-induced neurotoxicity. Here, we investigated tau and Fyn interactions and the potential implications for positioning of these proteins in membrane microdomains. Tau is known to bind to Fyn via its Src-homology (SH)3 domain, an association regulated by phosphorylation of PXXP motifs in tau. Here, we show that Pro216 within the PXXP(213-216) motif in tau plays an important role in mediating the interaction of tau with Fyn-SH3. We also show that tau interacts with the SH2 domain of Fyn, and that this association, unlike that of Fyn-SH3, is influenced by Fyn-mediated tyrosine phosphorylation of tau. In particular, phosphorylation of tau at Tyr18, a reported target of Fyn, is important for mediating Fyn-SH2-tau interactions. Finally, we show that tyrosine phosphorylation influences the localization of tau to detergent-resistant membrane microdomains in primary cortical neurons, and that this trafficking is Fyn-dependent. These findings may have implications for the development of novel therapeutic strategies aimed at disrupting the tau/Fyn-mediated synaptic dysfunction that occurs in response to elevated Aβ levels in neurodegenerative disease.

Tyrosine phosphorylation of tau by the SRC family kinases lck and fyn

Background

Tau protein is the principal component of the neurofibrillary tangles found in Alzheimer's disease, where it is hyperphosphorylated on serine and threonine residues, and recently phosphotyrosine has been demonstrated. The Src-family kinase Fyn has been linked circumstantially to the pathology of Alzheimer's disease, and shown to phosphorylate Tyr18. Recently another Src-family kinase, Lck, has been identified as a genetic risk factor for this disease.

Results

In this study we show that Lck is a tau kinase. In vitro, comparison of Lck and Fyn showed that while both kinases phosphorylated Tyr18 preferentially, Lck phosphorylated other tyrosines somewhat better than Fyn. In co-transfected COS-7 cells, mutating any one of the five tyrosines in tau to phenylalanine reduced the apparent level of tau tyrosine phosphorylation to 25-40% of that given by wild-type tau. Consistent with this, tau mutants with only one remaining tyrosine gave poor phosphorylation; however, Tyr18 was phosphorylated better than the others.

Conclusions

Fyn and Lck have subtle differences in their properties as tau kinases, and the phosphorylation of tau is one mechanism by which the genetic risk associated with Lck might be expressed pathogenically.

Hysterosalpingogram: an essential examination following Essure hysteroscopic sterilisation

OBJECTIVES

The aim of this study was to describe our experience of imaging following hysteroscopic sterilisation with the Essure (Conceptus Inc., Mountain View, San Carlos, CA) microinsert, and to underline the importance of a carefully performed follow-up hysterosalpingogram (HSG) in the management of these patients.

METHODS

18 women underwent the procedure and all returned for follow-up HSG. A standard HSG technique was used and views were acquired to establish microinsert position and tubal occlusion.

RESULTS

In 16 of the 18 women, adequate microinsert positioning and bilateral tubal occlusion was present. In one woman, a unilateral microinsert occluded the fallopian tube, whereas the other fallopian tube was ligated with a clip. The final patient underwent two studies; both showed well-positioned microinserts but unilateral free spill from the right fallopian tube. There are no reported pregnancies thus far.

CONCLUSION

Essure sterilisation coils have a unique appearance when radiographed and are an effective means of permanently occluding the fallopian tubes. HSG is a rapid and safe method of confirming satisfactory placement and tubal occlusion. Non-HSG imaging techniques are suboptimal at detecting patent fallopian tubes and expose patients to the risk of an unwanted and potentially complicated pregnancy.

High fat feeding promotes simultaneous decline in insulin sensitivity and cognitive performance in a delayed matching and non-matching to position task

Obesity is the single greatest risk factor for the development of Type 2 diabetes mellitus (T2DM), with the prevalence of both dramatically increasing in recent years. These conditions are associated with medical complications such as hypertension, neuropathy and cardiovascular disease. Recent evidence also suggests a greater risk of developing dementia including Alzheimer's disease. The molecular mechanisms governing these changes remain obscure, although epidemiological evidence suggests that reduced insulin sensitivity (a characteristic of T2DM) is an independent risk factor for Alzheimer's disease. Here we examine the effects of diet-induced insulin resistance on cognitive ability in an animal model not predisposed to develop Alzheimer's pathology. Following 12 weeks on a high fat diet (45% of calories as crude fat) male Wistar rats were overweight and insulin resistant but not frankly diabetic. High fat fed animals were consistently poorer in all aspects of an operant based delayed matching to position task, yet were not impaired in spatial working memory as judged by the open field watermaze test. The cognitive deficit of the HF fed animals was most apparent when the task was switched from matching to non-matching to position, suggestive of an inability to change contingency. Performance in this task was negatively correlated with whole body insulin sensitivity but not weight gain. In conclusion this study has shown that insulin resistant animals exhibit impairments in an operant measure of behavioural flexibility which precede the development of diabetes.