Ventricular pacemaker lead in the left hemithorax: Mechanisms and evidence‐based management of a late‐onset hazardous complication

Late‐onset migration of pacing leads in the left hemithorax is a rare but potentially life‐threatening complication. Radiological examinations are required to detect any involvement of either left ventricle or lung parenchyma, prompting immediate surgical extraction in this setting. Identification of high‐risk patients is mandatory to prevent this complex iatrogenic complication.     

Achieved systolic blood pressure in older people: a systematic review and meta-analysis

Background

It remains unclear into which level the systolic blood pressure (SBP) should be lowered in order to provide the best cardiovascular protection among older people. Hypertension guidelines recommendation on attaining SBP levels <150 mmHg in this population is currently based on experts’ opinion. To clarify this issue, we systematically reviewed and quantified available evidence on the impact of achieving different SBP levels <150 mmHg on various adverse outcomes in subjects aged ≥60 years old receiving antihypertensive drug treatment.

Methods

We searched 8 databases to identify randomized controlled trials (RCTs) and post-hoc analyses or subanalyses of RCTs reporting the effects of attaining different SBP levels <150 mmHg on the risk of stroke, acute myocardial infarction, heart failure, cardiovascular mortality and all-cause mortality in participants aged ≥60 years. We performed random-effects meta-analyses stratified by study design.

Results

Eleven studies (> 33,600 participants) were included. Compared with attaining SBP levels ≥140 mmHg, levels of 130 to <140 mmHg were not associated with lower risk of outcomes in the meta-analysis of RCTs, whereas there was an associated reduction of cardiovascular mortality (RR 0.72, 95% CI 0.59–0.88) and all-cause mortality (RR 0.86, 95% CI 0.75–0.99) in the meta-analysis of post-hoc analyses or subanalyses of RCTs. Limited and conflicting data were available for the SBP levels of <130 mmHg and 140 to <150 mmHg.

Conclusions

Among older people, there is suggestive evidence that achieving SBP levels of 130 to <140 mmHg is associated with lower risks of cardiovascular and all-cause mortality. Future trials are required to confirm these findings and to provide additional evidence regarding the <130 and 140 to <150 mmHg SBP levels.

     

Synaptotagmin-7 phosphorylation mediates GLP-1–dependent potentiation of insulin secretion from β-cells

Glucose stimulates insulin secretion from β-cells by increasing intracellular Ca²⁺. Ca²⁺ then binds to synaptotagmin-7 as a major Ca²⁺ sensor for exocytosis, triggering secretory granule fusion and insulin secretion. In type-2 diabetes, insulin secretion is impaired; this impairment is ameliorated by glucagon-like peptide-1 (GLP-1) or by GLP-1 receptor agonists, which improve glucose homeostasis. However, the mechanism by which GLP-1 receptor agonists boost insulin secretion remains unclear. Here, we report that GLP-1 stimulates protein kinase A (PKA)-dependent phosphorylation of synaptotagmin-7 at serine-103, which enhances glucose- and Ca²⁺-stimulated insulin secretion and accounts for the improvement of glucose homeostasis by GLP-1. A phospho-mimetic synaptotagmin-7 mutant enhances Ca²⁺-triggered exocytosis, whereas a phospho-inactive synaptotagmin-7 mutant disrupts GLP-1 potentiation of insulin secretion. Our findings thus suggest that synaptotagmin-7 is directly activated by GLP-1 signaling and may serve as a drug target for boosting insulin secretion. Moreover, our data reveal, to our knowledge, the first physiological modulation of Ca²⁺-triggered exocytosis by direct phosphorylation of a synaptotagmin.Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells follows a biphasic time course consisting of an initial, transient first phase lasting 5–10 min followed by a slowly developing, sustained second phase (1). Type 2 diabetes (T2D) is associated with partial or complete loss of the first insulin secretion phase and a reduction in the second insulin secretion phase (2, 3). Incretins, especially GLP-1, boost GSIS in T2D patients, thereby improving glucose homeostasis (4). GLP-1 exerts its action by activating GLP-1R, a G-protein–coupled receptor expressed on the surface of β-cells, which leads to an increase of adenylate cyclase activity and production of cAMP. Elevated cAMP levels in β-cells enhance GSIS through PKA-dependent and -independent (mediated by Epac2) mechanisms (5, 6). Mouse models with constitutively increased PKA activity have established PKA’s predominant role in the GLP-1–induced potentiation of β-cell GSIS (7, 8), but the downstream effectors remain unidentified.Insulin is secreted in response to glucose by regulated exocytosis of insulin-containing secretory granules. Electrical activity leads to opening of plasmalemmal voltage-gated Ca²⁺ channels (VGCCs) on the β-cell plasma membrane; the resulting increase in [Ca²⁺]_i then triggers Ca²⁺-dependent exocytosis (9). Insulin granule exocytosis is mediated by a multiprotein complex composed of soluble SNAP-receptor (SNARE) proteins (SNAP-25, Syntaxin, and synaptobrevin-2) and Sec1/Munc18-like (SM) proteins (Munc18-1) by a process that shares similarities with synaptic vesicle exocytosis in neurons (10). To date, numerous SNARE isoforms have been implicated in GSIS (11, 12), including Syntaxin-1, Syntaxin-4, SNAP-25 or SNAP-23, and synaptobrevin-2/3 (or VAMP2/3), whereas VAMP8, a nonessential SNARE for GSIS, may be involved in the regulation of GLP-1 potentiation of insulin secretion (13).In addition to SNARE and SM proteins, a Ca²⁺ sensor is required to initiate membrane fusion during exocytosis. Synaptotagmins, expressed mainly in neurons and endocrine cells, share a similar domain structure: a short N-terminal domain, followed by a transmembrane domain, a linker region with variable length, and two tandem Ca²⁺-binding C₂ domains (C₂A and C₂B) at the C terminus (14, 15). Some synaptotagmins bind to phospholipids in a Ca²⁺-dependent manner and have been identified as major Ca²⁺ sensors for regulated exocytosis (14, 16). Synaptotagmin-1, -2, -7, and -9 function as Ca²⁺ sensors for neurotransmitter release, whereas synaptotagmin-1, -7 (Syt7), and -10 regulate hormone secretion and neuropeptide release (9, 17, 18). Specifically, Syt7 regulates insulin granule exocytosis in insulin-secreting cell lines (19, 20). Syt7 is highly expressed in human pancreatic β-cells, and Syt7 KO mice exhibit reduced insulin secretion and consequently impaired glucose tolerance following glucose stimulation (21–23). Collectively, these studies demonstrate that Syt7 is a major Ca²⁺ sensor mediating GSIS in β-cells.Given that GLP-1 potentiates insulin secretion in a glucose-dependent manner, it is highly likely that its insulinotropic action is exerted distally to the initiation of electrical activity, possibly at the level of Ca²⁺ sensing and membrane fusion. Here we report that Syt7 is a stoichiometric substrate for PKA and functions as a downstream target of PKA activated by GLP-1 signaling. Compared with wild-type mice, Syt7 KO mice showed reduced insulin secretion ex vivo and in vivo in response to treatment with the GLP-1 analog exendin-4 in a manner that depended on Syt7 phosphorylation at serine-103. Our data not only provide a mechanism by which GLP-1 stimulates insulin secretion, but also report the physiological regulation of a synaptotagmin by phosphorylation.     

Seroprevalence of group B Coxsackieviruses: Retrospective study in an Italian population

Group B Coxsackieviruses (CVB) include six serotypes (B1-6) responsible for a wide range of clinical diseases. Since no recent seroepidemiologic data are available in Italy, the study aim was to investigate CVB seroprevalence in a wide Italian population. The study retrospectively included 2459 subjects referring to a large academic hospital in Rome (Italy) in the period 2004-2016. Seroprevalence rates and neutralizing antibodies (nAb) titers were evaluated in relation to years of observation and subjects’ characteristics. Positivity for at least one serotype was detected in 69.1% of individuals. Overall, the prevalent serotype was B4, followed by B3 (33.3%), B5 (26.2%), B1 (12.7%), B2 (11.0%), and B6 (1.7%). For B2, a significant decrease in seroprevalence over years was observed. Positivity to at least one virus was 25.2% in children aged 0 to 2 years, but significantly increased in preschool (3-5 years) (50.3%) and school (6-10 years) children (70.4%). Higher nAb responses for B3 and B4 were observed in children aged 3 to 5 years. A high overall CVB prevalence was found. Type-specific variations in prevalence over time probably reflect the fluctuations in circulation typical of Enteroviruses. Children are at greater risk for CVB infection given the high number of seronegative subjects aged 0 to 10 years.     

Lifestyle factors,cardiovascular disease and all-cause mortality in middle-aged and elderly women: a systematic review and meta-analysis

Cardiovascular disease (CVD) risk factors, incidence and death increases from around the time of menopause comparing to women in reproductive age. A healthy lifestyle can prevent CVD, but it is unclear which lifestyle factors may help maintain and improve cardiovascular health for women after menopausal transition. We conducted a systematic review and meta-analysis of prospective cohort studies to evaluate the association between modifiable lifestyle factors (specifically smoking, physical activity, alcohol intake, and obesity), with CVD and mortality in middle-aged and elderly women. Pubmed, Embase, among other databases and reference lists were searched until February 29th, 2016. Study specific relative risks (RR) were meta-analyzed using random effect models. We included 59 studies involving 5,358,902 women. Comparing current versus never smokers, pooled RR were 3.12 (95% CI 2.15–4.52) for CHD incidence, 2.09 (95% CI 1.51–2.89) for stroke incidence, 2.76 (95% CI 1.62–4.71) for CVD mortality and 2.22 (95% CI 1.92–2.57) for all-cause mortality. Physical activity was associated with a decreased risk of 0.74 (95% CI 0.67–0.80) for overall CVD, 0.71 (95% CI 0.67–0.75) for CHD, 0.77 (95% CI 0.70–0.85) for stroke, 0.70 (95% CI 0.58–0.84) for CVD mortality and 0.71 (95% CI 0.65–0.78) for all-cause mortality. Comparing moderate drinkers versus non-drinkers, the RR was 0.72 (95% CI 0.56–0.91) for CHD, 0.63 (95% CI 0.57–0.71) for CVD mortality and 0.80 (95% CI 0.76–0.84) for all-cause mortality. For women with BMI 30–35 kg/m² the risk was 1.67 (95% CI 1.24–2.25) for CHD and 2.3 (95% CI 1.56–3.40) for CVD mortality, compared to normal weight. Each 5 kg/m² increase in BMI was associated with 24% (95% CI 16–33%) higher risk for all-cause mortality. This meta-analysis suggests that physical activity and moderate alcohol intake were associated with a reduced risk for CVD and mortality. Smoking and higher BMI were associated with an increased risk of these endpoints. Adherence to a healthy lifestyle may substantially lower the burden of CVD and reduce the risk of mortality among middle-aged and elderly women. However, this review highlights important gaps, as lack of standardized methods in assessing lifestyle factors and lack of accurate information on menopause status, which should be addressed by future studies in order to understand the role of menopause on the association between lifestyle factors and cardiovascular events.     

Age at natural menopause and risk of type 2 diabetes: a prospective cohort study

Aims/hypothesis

In this study, we aimed to examine the association between age at natural menopause and risk of type 2 diabetes, and to assess whether this association is independent of potential mediators.

Methods

We included 3639 postmenopausal women from the prospective, population-based Rotterdam Study. Age at natural menopause was self-reported retrospectively and was treated as a continuous variable and in categories (premature, <40 years; early, 40–44 years; normal, 45–55 years; and late menopause, >55 years [reference]). Type 2 diabetes events were diagnosed on the basis of medical records and glucose measurements from Rotterdam Study visits. HRs and 95% CIs were calculated using Cox proportional hazards models, adjusted for confounding factors; in another model, they were additionally adjusted for potential mediators, including obesity, C-reactive protein, glucose and insulin, as well as for levels of total oestradiol and androgens.

Results

During a median follow-up of 9.2 years, we identified 348 individuals with incident type 2 diabetes. After adjustment for confounders, HRs for type 2 diabetes were 3.7 (95% CI 1.8, 7.5), 2.4 (95% CI 1.3, 4.3) and 1.60 (95% CI 1.0, 2.8) for women with premature, early and normal menopause, respectively, relative to those with late menopause (p _trend <0.001). The HR for type 2 diabetes per 1 year older at menopause was 0.96 (95% CI 0.94, 0.98). Further adjustment for BMI, glycaemic traits, metabolic risk factors, C-reactive protein, endogenous sex hormone levels or shared genetic factors did not affect this association.

Conclusions/interpretation

Early onset of natural menopause is an independent marker for type 2 diabetes in postmenopausal women.

     

Inositol hexakisphosphate suppresses excitatory neurotransmission via synaptotagmin-1 C2B domain in the hippocampal neuron

Inositol hexakisphosphate (InsP(6)) levels rise and fall with neuronal excitation and silence, respectively, in the hippocampus, suggesting potential signaling functions of this inositol polyphosphate in hippocampal neurons. We now demonstrate that intracellular application of InsP(6) caused a concentration-dependent inhibition of autaptic excitatory postsynaptic currents (EPSCs) in cultured hippocampal neurons. The treatment did not alter the size and replenishment rate of the readily releasable pool in autaptic neurons. Intracellular exposure to InsP(6) did not affect spontaneous EPSCs or excitatory amino acid-activated currents in neurons lacking autapses. The InsP(6)-induced inhibition of autaptic EPSCs was effectively abolished by coapplication of an antibody to synaptotagmin-1 C2B domain. Importantly, preabsorption of the antibody with a GST-WT synaptotagmin-1 C2B domain fragment but not with a GST-mutant synaptotagmin-1 C2B domain fragment that poorly reacted with the antibody impaired the activity of the antibody on the InsP(6)-induced inhibition of autaptic EPSCs. Furthermore, K(+) depolarization significantly elevated endogenous levels of InsP(6) and occluded the inhibition of autaptic EPSCs by exogenous InsP(6). These data reveal that InsP(6) suppresses excitatory neurotransmission via inhibition of the presynaptic synaptotagmin-1 C2B domain-mediated fusion via an interaction with the synaptotagmin Ca(2+)-binding sites rather than via interference with presynaptic Ca(2+) levels, synaptic vesicle trafficking, or inactivation of postsynaptic ionotropic glutamate receptors. Therefore, elevated InsP(6) in activated neurons serves as a unique negative feedback signal to control hippocampal excitatory neurotransmission.