Pancreatic β-cell K<Subscript>ATP</Subscript> channels: Hypoglycaemia and hyperglycaemia

The pancreatic β-cell ATP-sensitive K⁺ channel (K_ATP channel) plays a critical role in glucose homeostasis by linking glucose metabolism to electrical excitability and insulin secretion. Changes in the intracellular ratio of ATP/ADP mediate the metabolic regulation of channel activity. The β-cell K_ATP channel is a hetero-octameric complex composed of two types of subunits: four inward-rectifying potassium channel pore-forming (Kir6.2) subunits and four high-affinity sulfonylurea receptor 1 (SUR1) subunits. Kir6.2 and SUR1 are encoded by the genes KCNJ11 and ABCC8, respectively. Mutations in these genes can result in congenital hyperinsulinism and permanent neonatal diabetes. This review highlights the important role of the β-cell K_ATP channel in glucose physiology and provides an introduction to some of the other review articles in this special edition of the Reviews in Endocrine and Metabolic Disorders.     

Val/Leu<Superscript>247</Superscript> and Trp/Ser<Superscript>316</Superscript> polymorphisms in β<Subscript>2</Subscript> glycoprotein I and their association with thrombosis in unselected Chilean patients

It is known that polymorphisms of β ₂-glycoprotein I (β ₂GPI) in exon 7 affect interaction between the phospholipid binding site and the antibodies, and that other polymorphisms in exon 8 increase the generation of antibodies. In this study, we analyzed genetic polymorphisms of β ₂GPI in unselected Chilean patients to determine the prevalence of β ₂GPI polymorphisms in the phospholipid domain in patients with venous and arterial thrombosis and the clinical correlation with thromboembolic complications. This study comprised 149 patients with venous and arterial thrombosis (62 with venous thrombosis and 87 with arterial thrombosis) and 160 healthy controls with no previous history of thrombosis. Polymorphisms of exons 7 and 8 of β ₂GPI, which encode for its fifth domain, were determined by PCR-RFLP. The presence of aPL or anti-β ₂GPI in the patients was detected by ELISA. Anti-β ₂GPI were present in 8/149 patients (5.4%); of these, five had aCL antibodies of low titer. The allele containing Val/Leu²⁴⁷ and Trp/Ser³¹⁶ was significantly more frequent in patients with thrombosis than in the control group (OR=3.1, CI 1.6–6.0, p=0.0003; OR=2.9, CI 1.1–8.6, p=0.027, respectively). These polymorphisms did not correlate with aPL or anti-β ₂GPI but significant differences were observed with venous thrombosis (p=<0.0001) and arterial thrombosis (p=0.026). In conclusion, the β ₂GPI polymorphisms Val/Leu²⁴⁷ and Trp/Ser³¹⁶ are not related to the presence of anti-β ₂GPI antibodies in unselected Chilean patients with venous and arterial thrombosis, but they are significantly associated with venous and arterial thrombosis.     

Inhaled Glucocorticosteroid and Long-Acting β<Subscript>2</Subscript>-Adrenoceptor Agonist Single-Inhaler Combination for Both Maintenance and Rescue Therapy

Despite aggressive fixed-dose (FD) combination therapy with inhaled glucocorticosteroids (ICS) and long acting beta(2)-adrenoceptor agonists (LABA), many patients with asthma remain suboptimally controlled, based on the need for rescue therapy and rates of severe exacerbations. The strategy of adjustable maintenance dosing (AMD) involves adjustment of the maintenance dose, (using a single combination [budesonide/formoterol] inhaler, Symbicort((R))) in response to variability of asthma control over time. The AMD strategy, like the FD approach, involves the use of a short-acting beta(2)-adrenoceptor agonist (SABA) for rapid relief of bronchospasm. The dose-response characteristics of budesonide/formoterol make the AMD strategy a feasible option that cannot be exploited with the combination of salmeterol/fluticasone propionate (Advair((R))). Several studies suggest that the AMD strategy is superior to a FD approach in terms of overall asthma control.Budesonide/formoterol in a single inhaler is as effective as albuterol (salbutamol) for relief of acute asthma episodes, a feature that makes it possible to use this combination for both maintenance and reliever therapy without the need for the use of a SABA. The single-inhaler strategy has been shown to be safe and more efficacious than FD therapy. In particular, the COSMOS study has demonstrated that exacerbation burden is reduced more effectively when the combination (budesonide/formoterol) single inhaler is used for both maintenance and relief compared with FD therapy with salmeterol/fluticasone and albuterol for rescue in patients with moderate-to-severe asthma. These findings suggest that we will have to reconsider our definition of reliever therapy for patients that require long-term therapy with combination ICS and LABA.The concept of single-inhaler therapy represents a paradigm shift in asthma management that has been validated in several large studies involving thousands of patients. The single-inhaler strategy represents one of the most significant advances in asthma management in many years, and one that appears ideal for adoption in primary care.     

HbE Level and Red Cell Parameters in Heterozygous HbE With and Without α<Superscript>0</Superscript>-Thalassemia Trait

We compared hemoglobin (Hb) E levels and red cell parameters between heterozygous HbE with and without α⁰-thalassemia trait and also determine their appropriated cut-off points for differentiating these two groups. High performance liquid chromatography analysis results and mean levels of red blood cell (RBC) parameters, including RBC count, total Hb, hematocrit, MCV, MCH and MCHC of heterozygous HbE with α⁰-thalassemia trait (n?=?183) and without α⁰-thalassemia trait (n?=?1437) were reviewed and compared. The α⁰-thalassemia status in these samples was detected by real-time PCR with SYBR Green1 and high resolution melting analysis. Mean levels of HbE, total Hb, MCV, MCH and MCHC of heterozygous HbE with α⁰-thalassemia trait were significantly lower than those of heterozygous HbE without α⁰-thalassemia trait (P?<?0.001). In addition, HbE level at a cut-off value of?<?24% was superior to MCV (<?80 fL) and MCH (<?27 pg) for differentiating the heterozygous HbE with and without α⁰-thalassemia trait with 100% sensitivity and 87.2% specificity. Despite certain limitations of this study like missing RDW and reticulocyte counts, and not testing for α⁺-thalassemia and Hb Constant Spring, we conclude that the HbE level at a cut-off point of?<?24% is a useful marker for initial discrimination between heterozygous HbE with and without α⁰-thalassemia trait.     

IgG antibodies to plasminogen and their relationship to IgG anti-β<Subscript>2</Subscript>-glycoprotein 1 antibodies and thrombosis

Reduced fibrinolytic activity has been described in primary antiphospholipid syndrome (PAPS) and may be responsible for thrombotic events. Some evidence supports a relationship between anti-plasminogen (PLG) antibodies, anti-β₂-glycoprotein 1 (β₂GP1) antibodies, and fibrinolysis, but their relationship is still unclear. The aim of study is to evaluate the association between IgG anti-β₂GP1 and IgG anti-PLG antibodies and thrombosis. Two groups of consecutive patients with PAPS and systemic lupus erythematosus (SLE): 32 patients with lupus anticoagulant (LAC), 32 patients without LAC, and 40 healthy controls were included. IgG against β₂GP1 and PLG antibodies were measured by enzyme-linked immunosorbent assay, and a value above the 99th percentile of the normal healthy control was considered as positive, and their interrelationship with thrombosis was evaluated by Pearson Chi-squared test. Cross-reactive antibodies binding to PLG and β₂GP1 were determined in a competitive and cross-inhibition assay. Levels of fibrinolytic activity in the presence of IgG fractions from patients and healthy controls were examined using a plasmin fluorogenic substrate assay. A high frequency of IgG anti-PLG antibodies (35.9%) was found in 64 patients, and its presence was associated with thrombosis (p = 0.001), which may be due to its ability to inhibit exogenous fibrinolysis. Coexistence of IgG anti-PLG and IgG anti-β₂GP1 antibodies was found in 11 of 64 patients and was related with thrombosis (p = 0.001). Cross-reactive antibody binding to PLG and β₂GP1 was found in IgG fractions from three patients and a monoclonal anti-β₂GP1 antibody BD4, and one of these three patients had thrombotic history. However, no significant association was found between IgG anti-PLG and IgG anti-β₂GP1 antibodies in patients. In conclusion, the prevalence of IgG anti-PLG was high in patients with PAPS and SLE and might relate with thrombosis. Cross-reactivity of IgG anti-β₂GP1 antibodies with PLG may occur in the sera of patients.     

β-Cell failure in diabetes: Common susceptibility and mechanisms shared between type 1 and type 2 diabetes

Diabetes mellitus is etiologically classified into type 1, type 2 and other types of diabetes. Despite distinct etiologies and pathogenesis of these subtypes, many studies have suggested the presence of shared susceptibilities and underlying mechanisms in β-cell failure among different types of diabetes. Understanding these susceptibilities and mechanisms can help in the development of therapeutic strategies regardless of the diabetes subtype. In this review, we discuss recent evidence indicating the shared genetic susceptibilities and common molecular mechanisms between type 1, type 2 and other types of diabetes, and highlight the future prospects as well.     

Heterophilic interactions between cell adhesion molecule L1 and α<Subscript>v</Subscript> β<Subscript>3</Subscript>-integrin induce HUVEC process extension <Emphasis Type="Italic">in vitro</Emphasis> and angiogenesis <Emphasis Type="Italic">in vivo</Emphasis>

Cell adhesion molecule L1 was implicated in angiogenic processes, tumor formation and metastasis. Here, we provide evidence that the sixth Ig-like domain of L1 (L1Ig6) interacts with _{v 3} to induce process extension of human umbilical vein endothelial cells (HUVECs) in vitro and angiogenesis in vivo. HUVECs formed network-like structures on full-length L1 or L1Ig6 substrates comparable to structures found on matrigel. In the presence of mab _{v 3} or cyclic RGD, apoptosis was induced. In fibrin matrices where L1Ig6 was covalently incorporated, HUVECs formed multicellular and hollow processes through interactions between cell-surface _{v 3} and RGD-sites of matrix-immobilized L1Ig6. No such processes were induced by L1Ig6 having non-functional RDG-sites, or in the presence of mab _{v 3} or cyclic RGD. In those matrices, increased apoptosis was found. Co-immunoprecipitation of L1 or L1Ig6 with _{v 3} suggests close interactions. Furthermore, L1Ig6 stimulated HUVECs showed increased tyrosine phosphorylation of _{v 3} and phosphorylation of MAP kinases (ERK1 and ERK2) but not AKT indicating specific activation of _v and _{v 3} followed by activation of downstream kinases. Application of L1Ig6-modified fibrin matrices on CAMs induced 50–60% increased _v and _v3 protein expression and in vivo angiogenesis indicated by ~50% increased mean vascular length density. The results demonstrate angiogenic potential of L1Ig6 involving ligation and activation of _v3     

Low Ambient [Cl<Superscript>−</Superscript>] Increases Ca<Superscript>2+</Superscript> Mobilization and Stimulates Nitric Oxide and Prostaglandin E<Subscript>2</Subscript> Production in Human Bronchial Epithelial Cells

Changes in ionic composition of airway surface fluid may modulate airway epithelial functions. We tested the hypothesis that fluctuations of ambient ionic composition could affect airway epithelial Ca²⁺ dynamics and Ca²⁺-dependent cellular functions, including NO release and PGE₂ production in vitro. The responses of intracellular Ca²⁺ concentration ([Ca²⁺]_i) to changes in extracellular Cl⁻ and Na⁺ concentrations ([Cl⁻]_e, [Na⁺]_e) in the human bronchial epithelial cell line, 16HBE cells, were measured by the fura-2 method. The NO release to the medium after lowering [Cl⁻]_e was measured by an amperometric NO sensor. PGE₂ production was measured by radioimmunoassay. Changing to isotonic low [Cl⁻]_e solution by substitution with gluconate caused a sustained increase in [Ca²⁺]_i in a concentration-dependent manner, with the maximal [Ca²⁺]_i increase from the baseline level being 243 ± 110 nM with Cl-free solution. The effect was not altered by thapsigargin but abolished by EGTA and by Cl channel blockers, including diphenylamine-2-carboxylate, disodium 4,4′-diisothiocyanatostilbene-2,2′-disulfonate, and disodium cromoglycate. In contrast, the effect of reduction of [Na⁺]_e by substitution with N-methyl-D-glucamine⁺ on [Ca²⁺]_i was less than that of reduction of [Cl⁻]_e. The reduction of [Cl⁻]_e caused a concentration-dependent rise in NO contents in the medium and PGE₂ production. This release of NO was inhibited by EGTA but not by dexamethasone pretreatment. These results suggest that the decrease in ambient [Cl⁻] induces Ca²⁺ mobilization probably through Ca²⁺ influx, followed by the release of NO and PGE₂, thereby modulating various cellular functions.     

The association between drinking motives and alcohol‐related consequences – room for biases and measurement issues?

Aims To investigate whether the predominant finding of generalized positive associations between self‐rated motives for drinking alcohol and negative consequences of drinking alcohol are influenced by (i) using raw scores of motives that may weight inter‐individual response behaviours too strongly, and (ii) predictor‐criterion contamination by using consequence items where respondents attribute alcohol use as the cause. Design Cross‐sectional study within the European School Survey Project on Alcohol and other Drugs (ESPAD). Setting School classes. Participants Students, aged 13–16 (n = 5633). Measurements Raw, rank and mean‐variance standardized scores of the Drinking Motives Questionnaire—Revised (DMQ‐R); four consequences: serious problems with friends, sexual intercourse regretted the next day, physical fights and troubles with the police, each itemized with attribution (‘because of your alcohol use’) and without. Findings As found previously in the literature, raw scores for all drinking motives had positive associations with negative consequences of drinking, while transformed (rank or Z) scores showed a more specific pattern: external reinforcing motives (social, conformity) had negative and internal reinforcing motives (enhancement, coping) had non‐significant or positive associations with negative consequences. Attributed consequences showed stronger associations with motives than non‐attributed ones. Conclusion Standard scoring of the Drinking Motives Questionnaire (Revised) fails to capture motives in a way that permits specific associations with different negative consequences to be identified, whereas use of rank or Z‐scores does permit this. Use of attributed consequences overestimates the association with drinking motives.     

Catecholaminergic nerve fibers and <Emphasis Type="Bold">β</Emphasis>-adrenergic receptors in the human heart and coronary vessels

The relationship between catecholaminergic nerve fibers and beta-adrenergic receptors in the heart and in the coronary vessels was studied in humans. Only living tissues, harvested from brain-dead heart donors, were used in this experiment. Morphological observations and histochemical staining for norepinephrine and other catecholamines were carried out and beta-adrenergic receptors were stained by means of a beta-blocking fluorescent drug. All morphological data underwent quantitative analysis of images and statistical evaluation. This study provided direct evidence for the distribution of catecholaminergic nerve fibers and of beta-adrenergic receptors in the myocardium and in the coronary arteries. Catecholaminergic nerve fibers are located in the periadventitial tissue, in the adventitia and in the transitional zone between the intima and media. The beta-adrenergic receptors are mainly located in the more innervated part of the heart and coronary arteries but there is a major, although incomplete, overlap with related catecholaminergic nerve fibers. Moreover, using specific substrates and/or inhibitors, two types of beta-adrenergic receptors, beta(1) and beta(2), were demonstrated. Owing to the scarcity of available material (we used only four hearts), and objective difficulties in enrolling other patients, we are at this moment unable to draw general conclusions.