Previous studies suggest that ether-a-go-go related gene (ERG) KCNH2 potassium channels contribute to the control of motility patterns in the gastrointestinal tract of animal models. The present ...study examines whether these results can be translated into a role in human gastrointestinal muscles. Messages for two different variants of the KCNH2 gene were detected: KCNH2 V1 human ERG (HERG) (28) and KCNH2 V2 (HERG(USO)) (13). The amount of V2 message was greater than V1 in both human jejunum and brain. The base-pair sequence that gives rise to domains S3-S5 of the channel was identical to that previously published for human KCNH2 V1 and V2. KCNH2 protein was detected immunohistochemically in circular and longitudinal smooth muscle and enteric neurons but not in interstitial cells of Cajal. In the presence of TTX (10(-6) M), atropine (10(-6) M). and l-nitroarginine (10(-4) M) human jejunal circular muscle strips contracted phasically (9 cycles/min) and generated slow waves with superimposed spikes. Low concentrations of the KCNH2 blockers E-4031 (10(-8) M) and MK-499 (3 x 10(-8) M) increased phasic contractile amplitude and the number of spikes per slow wave. The highest concentration of E-4031 (10(-6) M) produced a 10-20 mV depolarization, eliminated slow waves, and replaced phasic contractions with a small tonic contracture. E-4031 (10(-6) M) did not affect (14)CACh release from enteric neurons. We conclude that KCNH2 channels play a fundamental role in the control of motility patterns in human jejunum through their ability to modulate the electrical behavior of smooth muscle cells.
There are two types of diabetes. Type 1 diabetes affects younger people and needs treatment with insulin injections. Type 2 diabetes affects older people and can usually be treated by diet and oral ...drugs. Diabetic neuropathy affects 10% of patients with diabetes mellitus at diagnosis and 40% to 50% after 10 years. Enhanced glucose control is the best studied intervention for the prevention of this disabling condition but there have been no systematic reviews of the evidence.
To examine the evidence for enhanced glucose control in the prevention of distal symmetric polyneuropathy in people with type 1 and type 2 diabetes.
We searched the Cochrane Neuromuscular Disease Group Specialized Register (30 January 2012), CENTRAL (2012, Issue 1), MEDLINE (1966 to January 2012) and EMBASE (1980 to January 2012) for randomized controlled trials of enhanced glucose control in diabetes mellitus.
We included all randomized, controlled studies investigating enhanced glycemic control that reported neuropathy outcomes after at least one year of intervention. Our primary outcome measure was annual development of clinical neuropathy defined by a clinical scale. Secondary outcomes included motor nerve conduction velocity and quantitative vibration testing.
Two authors independently reviewed all titles and abstracts identified by the database searches for inclusion. Two authors abstracted data from all included studies with a standardized form. A third author mediated conflicts. We analyzed the presence of clinical neuropathy with annualized risk differences (RDs), and conduction velocity and quantitative velocity measurements with mean differences per year.
This review identified 17 randomized studies that addressed whether enhanced glucose control prevents the development of neuropathy. Seven of these studies were conducted in people with type 1 diabetes, eight in type 2 diabetes, and two in both types. A meta-analysis of the two studies that reported the primary outcome (incidence of clinical neuropathy) with a total of 1228 participants with type 1 diabetes revealed a significantly reduced risk of developing clinical neuropathy in those with enhanced glucose control, an annualized RD of -1.84% (95% confidence interval (CI) -1.11 to -2.56). In a similar analysis of four studies that reported the primary outcome, involving 6669 participants with type 2 diabetes, the annualized RD of developing clinical neuropathy was -0.58% (95% CI 0.01 to -1.17). Most secondary outcomes were significantly in favor of intensive treatment in both populations. However, both types of diabetic participants also had a significant increase in severe adverse events including hypoglycemic events.
According to high-quality evidence, enhanced glucose control significantly prevents the development of clinical neuropathy and reduces nerve conduction and vibration threshold abnormalities in type 1 diabetes mellitus. In type 2 diabetes mellitus, enhanced glucose control reduces the incidence of clinical neuropathy, although this was not formally statistically significant (P = 0.06). However, enhanced glucose control does significantly reduce nerve conduction and vibration threshold abnormalities. Importantly, enhanced glucose control significantly increases the risk of severe hypoglycemic episodes, which needs to be taken into account when evaluating its risk/benefit ratio.
SYNGAP1 is a neuronal Ras and Rap GTPase-activating protein with important roles in regulating excitatory synaptic plasticity. While many SYNGAP1 missense and nonsense mutations have been associated ...with intellectual disability, epilepsy, schizophrenia, and autism spectrum disorder (ASD), whether and how they contribute to individual disease phenotypes is often unknown. Here, we characterize 57 variants in seven assays that examine multiple aspects of SYNGAP1 function. Specifically, we used multiplex phospho-flow cytometry to measure variant impact on protein stability, pERK, pGSK3β, pp38, pCREB, and high-content imaging to examine subcellular localization. We find variants ranging from complete loss-of-function (LoF) to wild-type (WT)-like in their regulation of pERK and pGSK3β, while all variants retain at least partial ability to dephosphorylate pCREB. Interestingly, our assays reveal that a larger proportion of variants located within the disordered domain of unknown function (DUF) comprising the C-terminal half of SYNGAP1 exhibited higher LoF, compared to variants within the better studied catalytic domain. Moreover, we find protein instability to be a major contributor to dysfunction for only two missense variants, both located within the catalytic domain. Using high-content imaging, we find variants located within the C2 domain known to mediate membrane lipid interactions exhibit significantly larger cytoplasmic speckles than WT SYNGAP1. Moreover, this subcellular phenotype shows both correlation with altered catalytic activity and unique deviation from signaling assay results, highlighting multiple independent molecular mechanisms underlying variant dysfunction. Our multidimensional dataset allows clustering of variants based on functional phenotypes and provides high-confidence, multi-functional measures for making pathogenicity predictions.
To compare and contrast the evidence for the effect of glucose control on the prevention of neuropathy in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).
In T1DM, multiple ...clinical trials have demonstrated a large benefit from enhanced glucose control, whereas the benefit in T2DM is much more modest. Epidemiologic and laboratory evidence exists to support factors other than hyperglycemia in the development of neuropathy including obesity, hypertension, dyslipidemia, inflammation, and insulin resistance.
T1DM neuropathy and T2DM neuropathy are fundamentally different. In T1DM, glucose control has a large effect on the prevention of neuropathy; therefore, future efforts should continue to concentrate on this avenue of treatment. In contrast, in T2DM, glucose control has a small effect on the prevention of neuropathy; as a result, more research is needed to define the underlying mechanisms for the development of neuropathy. Understanding these mechanisms may lead to novel therapeutic approaches to prevent or treat diabetic neuropathy.
Background: The incidence of cystic fibrosis (CF) in Asians is rare. How these patients fare in terms of morbidity and mortality in the UK compared to their non-Asian peers is not well documented. ...Aims: To retrospectively study annual reviews of 31 Asian CF patients from three London paediatric CF centres. Methods: Disease severity was assessed by lung function, age at first infection with Pseudomonas aeruginosa, and body mass index (BMI). The Asian children were compared with 143 matched non-Asian patients with CF. Matching criteria used were same sex and treatment centre as the Asian index patient. In addition, the controls were matched so that their date of birth, date of diagnosis, and date at annual review were within 12 months of the index patient. Results: There was no significant difference in age at diagnosis or age at annual review between the Asian and non-Asian children. Mean Z-scores for FEV1 and FVC were significantly lower for the Asian girls. There was no significant difference in Z-scores for BMI between the Asian children and their controls. Age at first isolation of Pseudomonas aeruginosa in Asian girls was significantly later than for their controls (8.3 years compared to 5.6 years for non-Asian girls). Conclusions: While the Asian boys’ lung function seems comparable with that of their non-Asian peers, the Asian girls emerge as a potentially vulnerable group and more work is required to discover why this is the case.
Background Mutations in RYR1 are the most common overall cause of congenital myopathy. Dominant mutations are most often associated with central core disease and malignant hyperthermia. Several ...genotype–phenotype correlations have been identified for these mutations, while less is known about recessive mutations. Thus far, no systematic examinations on recessive mutations have been performed. Methods A large cohort of 106 recessive RYR1 cases was analyzed in this study. Cases were ascertained in the literature ( n = 92) and among clinicians ( n = 14). We also report several new cases identified in Canada. Results Among this cohort, almost 50% of cases were non-core myopathies. Of note, we found enrichment of hypomorphic mutations (mutations expected to diminish RyR1 expression) in patients with severe clinical phenotypes. In addition, hypomorphic mutations were more likely among non-central core myopathies. Analysis of non-hypomorphic mutation location revealed an enrichment of missense mutations in the MH/CCD hotspots and specifically in the selectivity filter of the channel pore. Conclusions This study represents the first comprehensive analysis of genotype–phenotype correlations in recessive RYR1 -myopathies. These results help in better understanding disease pathogenesis and prognosis. Specifically, the study supports that loss of protein function is predictive of disease severity. In addition, the results suggest that decreased RyR1 expression may dictate non-core related pathology; though, confirmation in a larger cohort should be performed since data on protein expression was limited. Lastly, the results implicate abnormal ion conductance through the channel pore in the pathogenesis of recessive core myopathies.
This study investigated regulation of L-type calcium channels (Cav1.2b) by acetylcholine (ACh) in rabbit portal vein myocytes. Whole-cell currents were recorded using 5 mmol/L barium as charge ...carrier. ACh (10 micromol/L) increased peak currents by 40%. This effect was not reversed by the selective muscarinic M3 receptor antagonist 4-DAMP (100 nmol/L) but was blocked by the M2 receptor antagonist methoctramine (5 micromol/L). The classical and novel protein kinase C (PKC) antagonist calphostin C (50 nmol/L) abolished ACh responses, whereas the classical PKC antagonist Gö6976 (200 nmol/L) had no effect. ACh responses were also abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (20 micromol/L), by the c-Src inhibitor PP2 (10 micromol/L) (but not the inactive analogue PP3), and by dialyzing cells with an antibody to the G-protein subunit Gbetagamma. Cells dialyzed with c-Src had significantly greater currents than control cells. Current enhancement persisted in the presence of LY294002, suggesting that c-Src is downstream of PI3K. Phorbol 12,13-dibutyrate (PDBu, 0.1 micromol/L) increased currents by 74%. This effect was abolished by calphostin C and reduced by Gö6976. The PDBu response was also reduced by PP2, and the PP2-insensitive component was blocked by Gö6976. In summary, these data suggest that ACh enhances Cav1.2b currents via M2 receptors that couple sequentially to Gbetagamma, PI3K, a novel PKC, and c-Src. PDBu stimulates the novel PKC/c-Src pathway along with a second pathway that is independent of c-Src and involves a classical PKC.
Familial amniotic band sequence (ABS) is rare but has been reported in the offspring of mothers with connective tissue disorders. We present a family of two half‐siblings with ABS who share the same ...biological father. Following a serious vascular event a de novo pathogenic variant in COL3A1 was detected in the father, confirming a diagnosis of vascular Ehlers–Danlos syndrome (vEDS). The same variant was found in both his ABS‐affected children but not in his unaffected child. The amniotic membrane is derived from fetal tissue, type III collagen being a component. As the affected children are paternal half‐siblings, ABS was less likely due to maternal factors. Rather, the amniotic bands may have resulted from decreased type III collagen production as seen in people with vEDS, causing fragility of the amniotic membrane. Consequently, it is important to consider vEDS in patients with ABS.
Objective: To adapt the Patient Generated Index (PGI) quality of life measure for use with lower limb amputees and to conduct a test–retest reliability and construct validity study on the adapted ...measure.
Design: Repeat questionnaire interviews with a four-week interval administered by trained peers.
Setting: Participants' homes.
Subjects: Forty-two unilateral lower limb transfemoral amputees, 16 years of age or older and fluent in English, fitted with a prosthesis and discharged into the community for at least one year following postoperative rehabilitation therapy.
Main results: An intraclass correlation coefficient of 0.48 (p < 0.001) was achieved for the index reliability analyses. Intraclass correlation (ICC) values for the seven most commonly mentioned areas of life affected by the amputation and its treatment ranged from 0.40 to 0.92. Comparing the PGI with the SF-12 Health Survey physical and mental component summaries gave Pearson's correlation coefficients of 0.12 (p < 0.5) and 0.56 (p < 0.001) respectively. Multiple linear regression analysis showed the SF-12 physical and mental component scores explained 31.5% of the variability in PGI scores, however, the mental component scores alone explained 31.2%.
Conclusions: The PGI was adapted and found to be moderately reliable in terms of repeatability during successive follow-up interviews. Testing its construct validity supported a stronger relationship between mental health and quality of life than between physical health and quality of life.
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