New mutations in acetylcholine receptor subunit genes reveal heterogeneity in the slow-channel congenital myasthenic syndrome

Mutations in genes encoding the epsilon, delta, beta and alpha subunits of the end plate acetylcholine (ACh) receptor (AChR) are described and functionally characterized in three slow-channel congenital myasthenic syndrome patients. All three had prolonged end plate currents and AChR channel opening episodes and an end plate myopathy with loss of AChR from degenerating junctional folds. Genetic analysis revealed heterozygous mutations: epsilon L269F and delta Q267E in Patient 1, beta V266M in Patient 2, and alpha N217K in Patient 3 that were not detected in 100 normal controls. Patients 1 and 2 have no similarly affected relatives; in Patient 3, the mutation cosegregates with the disease in three generations. epsilon L269F, delta Q267E and beta V266M occur in the second and alpha N217K in the first transmembrane domain of AChR subunits; all have been postulated to contribute to the lining of the upper half of the channel lumen and all but delta Q267E are positioned toward the channel lumen, and introduce an enlarged side chain. Expression studies in HEK cells indicate that all of the mutations express normal amounts of AChR. epsilon L269F, beta V266M, and alpha N217K slow the rate of channel closure in the presence of ACh and increase apparent affinity for ACh; epsilon L269F and alpha N217K enhance desensitization, and epsilon L269F and beta V266M cause pathologic channel openings in the absence of ACh, rendering the channel leaky, delta Q267E has none of these effects and is therefore a rare polymorphism or a benign mutation. The end plate myopathy stems from cationic overloading of the postsynaptic region. The safety margin of neuromuscular transmission is compromised by AChR loss from the junctional folds and by a depolarization block owing to temporal summation of prolonged end plate potentials at physiologic rates of stimulation.      

Congenital myasthenic syndromes: A diverse array of molecular targets

The neuromuscular junction (NMJ) has served as a prototype for understanding mechanisms underlying synaptic transmission over the past 50 years. More recently, analysis of congenital myasthenic syndromes (CMS) revealed a diverse array of molecular targets and delineated their contributions to synaptic function. Clinical, electrophysiologic and morphologic studies have paved the way for detecting CMS-related mutations in proteins such as choline acetyltransferase acetylcholinesterase, the acetylcholine receptor, rapsyn, and the voltage-gated sodium channel of the Na(v)1.4 type. Further studies of the mutant proteins have allowed us to correlate the effects of the mutations with predicted alterations in protein structure. In this review, we focus on the symptomatology of the CMS, consider the factors that impair neuromuscular transmission, survey the mutations that have been uncovered in the different synaptic proteins, and consider the functional implications of the identified mutations.     

Association between HLA-G genotype and risk of pre-eclampsia: a case-control study using family triads

Pre-eclampsia affects 2-7% of all pregnancies with varying severity and is a leading cause of maternal and fetal mortality and morbidity. The aetiology involves almost certainly a combination of genetic predisposition with maternal and fetal contributions and environmental factors. Research points towards pathologies in the placenta as the triggering factor which leads to systemic endothelial dysfunction in the mother, probably as the result of interaction with released placental factors circulating in the maternal blood. One prominent hypothesis regarding the aetiology of pre-eclampsia suggests that it is caused by immune- maladaptation. The MHC class Ib gene, HLA-G, is expressed in the placenta and seems to have immunomodulatory functions. Aberrant HLA-G mRNA and protein expression in pre-eclamptic placentas have been reported. Here, we have investigated detailed HLA-G genotypes in a case-control study of 155 family triads of mother, father and newborn. Among primiparas, an overrepresentation of a homozygous HLA-G genotype was detected in the 40 pre-eclamptic offspring compared to the 70 controls [P = 0.002, Fisher's exact test; odds ratio 5.57 (95% CI 1.79-17.31)]. Further analyses suggested that the differences between pre-eclamptic cases and controls primarily were accomplished by a different transmission from the father of a 14 bp deletion/insertion polymorphism in exon 8 (P = 0.006, Fisher's exact test), which previously has been linked to differences in the levels of HLA-G expression and in HLA-G mRNA splicing. The results may also indicate that combined mother-child HLA-G genotypes could influence the risk of developing pre-eclampsia. Overall, the study suggests that HLA-G genotypes and expression might have a significant influence on development of pre-eclampsia.     

Impact of type 1 diabetes on maternal long-term risk of hospitalisation and mortality: a nationwide combined clinical and register-based cohort study (The EPICOM study)

Aims/hypothesis

The aims of this study were to examine long-term mortality and morbidity rates in mothers with type 1 diabetes, both overall and according to the level of albuminuria prior to pregnancy, the presence of hypertension, pre-eclampsia and periconceptional HbA_1c.

Methods

This study was a part of the EPICOM (Environmental Versus Genetic and Epigenetic Influences on Growth, Metabolism and Cognitive Function in Offspring of Mothers with Type 1 Diabetes) study, which is a prospective follow-up study focusing on pregnancies complicated by maternal type 1 diabetes. We carried out a nationwide combined clinical and register-based cohort study of mortality rates and hospital admissions in mothers with diabetes (n?=?986) who gave birth between 1992 and 2000. Control mothers (n?=?91,441) were women from the background population, matched according to age and year of childbirth. Age at follow-up was 32–66 years.

Results

Mortality rate was increased threefold in mothers with diabetes compared with control mothers (HR 3.41 [95% CI 2.42, 4.81]; p?<?0.0001), and was also increased with pre-gestational kidney dysfunction (normoalbuminuria, HR 2.17 [95% CI 1.28, 3.68]; microalbuminuria, HR 3.36 [95% CI 0.82, 13.8]; macroalbuminuria, HR 12.9 [95% CI 5.45, 30.7]). Moreover, the presence of hypertension prior to or at any time during pregnancy and of pre-eclampsia also increased mortality rate (hypertension, HR 4.34 [95% CI 2.13, 8.84]; pre-eclampsia, HR 5.55 [95% CI 2.71, 11.4]). Mortality rate also increased with higher levels of HbA_1c in early pregnancy (HbA_1c ≤75 mmol/mol [≤9%], HR 2.15 [95% CI 1.31, 3.53]; HbA_1c >75 mmol/mol [>9%], HR 6.10 [95% CI 2.67, 14.0]). However, in mothers with diabetes and HbA_1c <64 mmol/mol (<8%) in the first trimester and normal pre-gestational urinary albumin excretion rate (n?=?517), mortality rate was comparable with that of control mothers. Among mothers with diabetes, mortality rate was associated with HbA_1c level: per 11 mmol/mol (1 percentage point) increase in HbA_1c, HR was 1.52 (95% CI 1.19, 1.94; p?=?0.001). In mothers with diabetes, the overall incidence of hospital admissions was more than double (incidence rate ratio [IRR] 2.69 [95% CI 2.59, 2.80]; p?<?0.0001) that of control mothers, as were admissions with various diagnoses from 14 out of 19 ICD-10 chapters. Among mothers with diabetes, the IRR for hospital admissions increased with the level of HbA_1c: per 11 mmol/mol (1 percentage point) increase in HbA_1c, HR was 1.07 (95% CI 1.04, 1.10; p?<?0.0001).

Conclusions/interpretation

Overall, mothers with type 1 diabetes have a two- to threefold increase in mortality and morbidity rates. HbA_1c levels, level of albuminuria around the time of conception, and the presence of hypertension and pre-eclampsia are important risk factors for mortality/morbidity in this cohort. However, it is reassuring that mothers with type 1 diabetes without kidney complications and with HbA_1c <64 mmol/mol (<8%) in early pregnancy have a similar survival potential during the period where they are raising their children to that of control mothers from the background population.

     

Four commercial urease reagents and a laboratory-prepared reagent compared for analysis of blood urea nitrogen with the Beckman analyzer.

Three laboratory-prepared urease reagents were compared with a commercial preparation supplied for routine use on the Beckman Blood Urea Nitrogen Analyzer. There were discrepancies in results for urea nitrogen among the four urease reagents when matching serum and the corresponding oxalate/fluoride treated plasma were compared as measured with the Beckman Analyzer and continuous-flow (AutoAnalyzer) method. All four urease preparations were affected by fluoride, but to different extents. We believe that an effective laboratory reagent can be prepared in the laboratory at significantly lower cost.     

Conditioned Pain Modulation and Pressure Pain Sensitivity in the Adult Danish General Population: The DanFunD Study

Increased pressure pain sensitivity and impaired descending pain control have been associated with chronic pain, but knowledge on the variability in the adult general population is lacking. Pressure pain thresholds (PPTs) and descending pain control assessed using conditioned pain modulation (CPM) were recorded in a randomly selected sample (n = 2,199, 53% female) of the Danish adult general population aged 18 to 70 years. PPTs were recorded over the tibialis anterior muscle and the upper trapezius muscle. CPM was defined as the difference between PPT assessments before and during conditioning with cold pressor pain (hand) for 2 minutes. Conditioning pain intensity was assessed using a visual analog scale and questionnaire data were collected. Female sex (P < .001) and younger age (P ≤ .02) was associated with lower PPTs at both body sites. For the trapezius muscle, high perceived stress was associated with lower PPTs (P < .02), whereas an interaction was found between body mass index and sex. CPM potency was lower in female compared with male participants (P ≤ .003), whereas no association with age was found. Higher level of education (P ≤ .05), premature withdrawal from the cold pressor test (P ≤ .02), and high visual analog scale score (P ≤ .02) were associated with a larger CPM response.

Macrophages and scavenger receptors in obesity-associated non-alcoholic liver fatty disease (NAFLD)

With an increase in sedentary lifestyle and dietary over nutrition, obesity has become one of the major public health problems worldwide and is a prevalent predisposing risk factor to non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in Western developed countries. NAFLD represents a series of diseased states ranging from non-alcoholic fatty liver (NAFL) to steatohepatitis (NASH), which can lead to fibrosis and eventually to cirrhosis and hepatocellular carcinoma. Currently, the only effective treatment to cure end-stage liver disease is liver transplantation. Macrophages have been reported to play a crucial role in the progression of NAFLD, thereby are a potential target for therapy. In this review, we discuss the current knowledge on the role of macrophages and inflammatory signalling pathways associated with obesity and chronic liver inflammation, and their contribution to NAFLD development and progression.