Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation

The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9-39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B

The molecular logic of endocannabinoid signalling

The endocannabinoids are a family of lipid messengers that engage the cell surface receptors that are targeted by Δ9-tetrahydrocannabinol, the active principle in marijuana (Cannabis). They are made on demand through cleavage of membrane precursors and are involved in various short-range signalling processes. In the brain, they combine with CB1 cannabinoid receptors on axon terminals to regulate ion channel activity and neurotransmitter release. Their ability to modulate synaptic efficacy has a wide range of functional consequences and provides unique therapeutic possibilities. © 2003, Nature Publishing Group. All rights reserved

Value of risk scores in the decision to palliate patients with ruptured abdominal aortic aneurysm

Background: The aim of this study was to develop a 48-h mortality risk score, which included morphology data, for patients with ruptured abdominal aortic aneurysm presenting to an emergency department, and to assess its predictive accuracy and clinical effectiveness in triaging patients to immediate aneurysm repair, transfer or palliative care. Methods: Data from patients in the IMPROVE (Immediate Management of the Patient With Ruptured Aneurysm: Open Versus Endovascular Repair) randomized trial were used to develop the risk score. Variables considered included age, sex, haemodynamic markers and aortic morphology. Backwards selection was used to identify relevant predictors. Predictive performance was assessed using calibration plots and the C-statistic. Validation of the newly developed and other previously published scores was conducted in four external populations. The net benefit of treating patients based on a risk threshold compared with treating none was quantified. Results: Data from 536 patients in the IMPROVE trial were included. The final variables retained were age, sex, haemoglobin level, serum creatinine level, systolic BP, aortic neck length and angle, and acute myocardial ischaemia. The discrimination of the score for 48-h mortality in the IMPROVE data was reasonable (C-statistic 0·710, 95 per cent c.i. 0·659 to 0·760), but varied in external populations (from 0·652 to 0·761). The new score outperformed other published risk scores in some, but not all, populations. An 8 (95 per cent c.i. 5 to 11) per cent improvement in the C-statistic was estimated compared with using age alone. Conclusion: The assessed risk scores did not have sufficient accuracy to enable potentially life-saving decisions to be made regarding intervention. Focus should therefore shift to offering repair to more patients and reducing non-intervention rates, while respecting the wishes of the patient and family

Emergency endovascular treatment for ruptured abdominal aortic aneurysm and the risk of spinal cord ischemia

BackgroundSpinal cord ischemia is a rare complication after open surgical repair for ruptured abdominal aortic aneurysms (rAAA). The use of emergency endovascular aortic aneurysm repair (eEVAR) is increasing, and paraplegia has been observed in a few patients. The objective of this study was to assess the incidence and pathogenesis of spinal cord ischemia after eEVAR in greater detail.MethodsThis was a retrospective analysis of patients who had eEVAR for rAAA in three hospitals in The Netherlands and Belgium during a 3-year study period that ended in February 2004. The use of aortouniiliac devices combined with a femorofemoral crossover bypass was the preferred technique. Patients with postoperative symptoms of spinal cord ischemia were identified and the influence of potential risk factors was assessed. These factors included the presence of common iliac artery aneurysms necessitating device limb extension to the external iliac artery with associated overlapping the hypogastric artery, the prolonged interruption of bilateral hypogastric artery arterial inflow during the procedure (defined “functional aortic occlusion time” >30 minutes), and the occurrence of preoperative hemodynamic shock.ResultsThirty-five patients were treated by EVAR and they constituted the study group. The first-month mortality in the study group with EVAR was 23%. Four patients (11.5%) with EVAR developed paraplegia postoperatively; the unilateral or bilateral hypogastric artery in all four patients became occluded during the procedure. In the other 31 patients who did not have paraplegia, the unilateral or bilateral hypogastric arteries became occluded in 14 patients (45%). This constituted a significant difference in the prevalence of hypogastric artery occlusion in patients with or without paraplegia (P = .04). The functional aortic occlusion time was prolonged in all four patients with paraplegia and in five without spinal cord ischemia (P = .0003). All four patients with spinal cord ischemia presented with hemodynamic shock. This factor did not reach a significant difference from nonparaplegic patients.ConclusionEmergency EVAR continues to be a promising approach to reduce the high mortality of rAAA, but the incidence of spinal cord ischemia after endovascular treatment of rAAA was worrisome. Although the pathogenesis is most likely multifactorial, interruption of the hypogastric artery inflow appeared to have significant influence. In patients with aneurysmatic common iliac arteries, any effort should be made to minimize hypogastric occlusion time during the procedure and to maintain hypogastric artery inflow afterwards, either by the use of a bell-bottom iliac extension or by electing open repair

Risk factors for premature atherosclerosis

Objectives: to investigate the prevalence of risk factors in patients with premature atherosclerosis. Design: retrospective controlled study. Materials: 135 consecutive patients with premature atherosclerosis less than or equal to 55 years (group I) were investigated. A control group comprised 107 consecutive patients greater than or equal to 65 years (group II) with atherosclerosis. Statistical analysis was performed with Chi-squared test and logistic regression analysis. Results: group I versus group II: diabetes 11% vs. 27% (p=0.001), smoking 84% vs. 67% (p=0.002), hypertension 36% vs. 58% (p=0.001), hypercholesterolaemia 47% vs. 34% (p =0.04), family history of cardiovascular disease 53% vs. 42 % (p = 0.08). In group I hyperhomocysteinaemia was present in 24 of the 108 patients tested, anticardiolipin antibodies were present in four of the 34 tested and coagulation abnormalities were found in four of the 22 patients tested. Conclusion: the difference in the prevalence of the different risk factors between the two groups suggests that either certain risk factors are more likely to cause premature atherosclerosis, or that other risk factors must be present in addition to the known risk factors in order to induce premature atherosclerosis