Role of angiotensin receptor-neprilysin inhibitor in diabetic complications.

Diabetes mellitus is a prevalent disorder with multi-system manifestations, causing a significant burden in terms of disability and deaths globally. Angio-tensin receptor-neprilysin inhibitor (ARNI) belongs to a class of medications for treating heart failure, with the benefits of reducing hospitalization rates and mortality. This review mainly focuses on the clinical and basic investigations related to ARNI and diabetic complications, discussing possible physiological and molecular mechanisms, with insights for future applications.

Empagliflozin Induces Vascular Relaxation in Rat Coronary Artery Due to Activation of BK Channels.

Purpose: The aim of this study was to investigate the effects and mechanisms of SGLT2 inhibitor empagliflozin on diabetic coronary function. Methods: A rat diabetic model was established by injection of streptozotocin. Rats in the treated group were administered empagliflozin by gavage and rat coronary vascular tensions were measured after eight weeks. Large conductance calcium activated K+ channel currents were recorded using a patch clamp technique, while human coronary artery smooth muscle cells were used to explore the underlying mechanisms. Results: After incubation with empagliflozin (10, 30, 100, 300, 1000 µmol/L), the Δ relaxation % of rat coronary arteries were 2.459 ± 1.304, 3.251 ± 1.119, 6.946 ± 3.407, 28.36 ± 11.47, 86.90 ± 3.868, respectively. Without and with empagliflozin in the bath solution, BK channel opening probabilities at a membrane potential of +60 mV were 0.0458 ± 0.0517 and 0.3413 ± 0.2047, respectively (p < 0.05, n = 4 cells). After incubation with iberiotoxin, the Δ tensions of rat coronary arteries in the control (Ctrl), untreated (DM), low empagliflozin (10 mg/kg/d)-treated (DM+L-EMPA) and high empagliflozin (30mg/kg/d)-treated (DM+H-EMPA) group were 103.20 ± 5.85, 40.37 ± 22.12, 99.47 ± 28.51, 78.06 ± 40.98, respectively (p < 0.01 vs Ctrl, n = 3-7; p < 0.001 vs DM+L-EMPA, n = 5-7). Empagliflozin restored high glucose-induced downregulation of Sirt1, Nrf2, and BK-ß1, while the effect of empagliflozin disappeared in the presence of EX-527, a Sirt1 selective inhibitor. Conclusion: Empagliflozin has a vasodilation effect on the coronary arteries in a concentration-dependent manner and can activate BK channels via the Sirt1-Nrf2 mechanism.

Glucose fluctuations aggravated the late sodium current induced ventricular arrhythmias via the activation of ROS/CaMKII pathway.

BACKGROUND: Recent evidence revealed that glucose fluctuation might be more likely to cause arrhythmia than persistent hyperglycemia, whereas its mechanisms were elusive. We aimed to investigate the effect of glucose fluctuation on the occurrence of ventricular arrhythmia and its mechanism. METHODS: Streptozotocin (STZ) induced diabetic rats were randomized to five groups: the controlled blood glucose (C-STZ) group, uncontrolled blood glucose (U-STZ) group, fluctuated blood glucose (GF-STZ) group, and GF-STZ rats with 100 mg/kg Tempol (GF-STZ + Tempol) group or with 5 mg/kg KN93 (GF-STZ + KN93) group. Six weeks later, the susceptibility of ventricular arrhythmias and the electrophysiological dysfunctions of ventricular myocytes were evaluated using electrocardiogram and patch-clamp technique, respectively. The levels of reactive oxygen species (ROS) and oxidized CaMKII (ox-CaMKII) were determined by fluorescence assay and Western blot, respectively. Neonatal rat cardiomyocytes and H9C2 cells in vitro were used to explore the underlying mechanisms. RESULTS: The induction rate of ventricular arrhythmias was 10%, 55%, and 90% in C-STZ group, U-STZ group, and GF-STZ group, respectively (P < 0.05). The electrophysiological dysfunctions of ventricular myocytes, including action potential duration at repolarization of 90% (APD90), APD90 short-term variability (APD90-STV), late sodium current (INa-L), early after depolarization (EAD) and delayed after depolarizations (DAD), as well as the levels of ROS and ox-CaMKII, were significantly increased in GF-STZ group. In vivo and ex vivo, inhibition of ROS or ox-CaMKII reversed these effects. Inhibition of INa-L also significantly alleviated the electrophysiological dysfunctions. In vitro, inhibition of ROS increase could significantly decrease the ox-CaMKII activation induced by glucose fluctuations. CONCLUSIONS: Glucose fluctuations aggravated the INa-L induced ventricular arrhythmias though the activation of ROS/CaMKII pathway.

Radiofrequency ablation of premature ventricular contractions guided by robotic magnetic navigation combined with pattern matching filter.

BACKGROUND: This study's intent is to evaluate the usefulness of pattern matching filter (PMF) function combined with robotic magnetic navigation (RMN) in guiding the ablation of premature ventricular contractions (PVCs). HYPOTHESIS: Assume that PMF can improve the outcomes of PVCs ablation using RMN. METHODS: A retrospective analysis was completed consisting of 118 consecutive patients with PVCs who underwent radiofrequency ablation guided by RMN. According to the application of PMF, patients were divided into two groups: 20 patients underwent ablation without PMF (group A), and another 98 patients received ablation incorporating PMF (group B). RESULTS: Compared with group A, the procedure time (135.0 ± 28.3 min vs. 106.3 ± 37.9 min, p = 0.02) in group B was significantly decreased, while the X-ray exposure time (6.0 ± 2.6 min vs. 6.5 ± 3.6 min, p = 0.705) and dose (3.2 ± 2.4 gycm2 vs. 3.9 ± 2.7 gycm2 ，p = 0.208) had no significant difference. Group B had a more than twofold number of points acquired (66.9 ± 23.0 vs. 143.9 ± 68.3, p < 0.001) and required a shorter radiofrequency ablation time (13.2 ± 3.5 min vs. 8.1 ± 2.9 min, p < 0.001). There were no serious complications in either group. The acute success rate was similar [90.0% (18/20) vs. 87.8% (86/98), p = 1.000] in two groups, and the success rate was also similar in the long-term follow-up [83.3% (15/18) vs. 87.2% (75/86), p = 0.776]. CONCLUSIONS: The ablation of PVCs guided by RMN is safe and effective. Combined with the functional capability of PMF, both procedure time and radiofrequency ablation time were significantly decreased.

Atrial Fibrillation Ablation Using Robotic Magnetic Navigation Reduces the Incidence of Silent Cerebral Embolism.

Background: The incidence of silent cerebral embolisms (SCEs) has been documented after pulmonary vein isolation using different ablation technologies; however, it is unreported in patients undergoing with atrial fibrillation (AF) ablation using Robotic Magnetic Navigation (RMN). The purpose of this prospective study was to investigate the incidence, risk predictors and probable mechanisms of SCEs in patients with AF ablation and the potential impact of RMN on SCE rates. Methods and Results: We performed a prospective study of 166 patients with paroxysmal or persistent AF who underwent pulmonary vein isolation. Patients were divided into RMN group (n = 104) and manual control (MC) group (n = 62), and analyzed for their demographic, medical, echocardiographic, and risk predictors of SCEs. All patients underwent cerebral magnetic resonance imaging within 48 h before and after the ablation procedure to assess cerebral embolism. The incidence and potential risk factors of SCEs were compared between the two groups. There were 26 total cases of SCEs in this study, including 6 cases in the RMN group and 20 cases in the MC group. The incidences of SCEs in the RMN group and the MC group were 5.77 and 32.26%, respectively (X2 = 20.63 P < 0.05). Univariate logistic regression analysis demonstrated that ablation technology, CHA2DS2-VASc score, history of cerebrovascular accident/transient ischemic attack, and low ejection fraction were significantly associated with SCEs, and multivariate logistic regression analysis showed that MC ablation was the only independent risk factor of SCEs after an AF ablation procedure. Conclusions: Ablation technology, CHA2DS2-VASc score, history of cerebrovascular accident/transient ischemic attack, and low ejection fraction are associated with SCEs. However, ablation technology is the only independent risk factor of SCEs and RMN can significantly reduce the incidence of SCEs resulting from AF ablation. Clinical Trial Registration: ChiCTR2100046505.

Association between CRT(D)/ICD and renal insufficiency: A systematic review and meta-analysis.

Cardiac resynchronization therapy with or without a defibrillator (CRT(D)) and implantable cardioverter defibrillator (ICD) may reduce the risk of arrhythmia or heart failure-specific mortality and improves the prognosis of patients with chronic kidney disease (CKD) or dialysis. The aim of this study was to perform a meta-analysis investigating the relationship between CRT(D)/ICD and renal insufficiency. Cochrane Library, Web of Science, Embase, and Pubmed were systematically searched from inception to 29 October 2019. We included studies that report all-cause mortality of patients with renal insufficiency who received CRT(D)/ICD therapy. Twenty-six studies (n = 119,263) were included, exploring the relationship between CRT(D)/ICD and renal insufficiency from two aspects: (1) Compared with ICD-only, CRT(D) was associated with lower risk of all-cause mortality in CKD patients (odds ratios (OR) = 0.67; 95% confidence interval (CI), 0.60 to 0.75). For non-primary prevention (secondary prevention or both), the analysis revealed a lower risk of all-cause mortality in the ICD group than in the no-ICD group (OR = 0.47; 95% CI, 0.40 to 0.55). (2) CKD increased all-cause mortality in comparison with control group (OR = 2.12; 95% CI, 1.85 to 2.44), and so did dialysis (OR = 2.53; 95% CI, 2.34 to 2.73). Furthermore, compared with CKD3 (eGFR: 30-59 ml/min/1.73 m2 ), CKD4/5 (eGFR <30 ml/min/1.73 m2 ) was observed to have a significantly higher risk of all-cause mortality (OR = 2.70; 95% CI, 1.93 to 3.80). This review shows a clear association between CRT(D)/ICD and renal insufficiency in the aspect of all-cause mortality, and may provide a reference for the clinical application of CRT(D)/ICD.

Blockade of ß-adrenergic signaling suppresses inflammasome and alleviates cardiac fibrosis.

BACKGROUND: Heart failure (HF) is an end-stage syndrome of all structural heart diseases which accompanies the loss of myocardium and cardiac fibrosis. Although the role of inflammasome in cardiac fibrosis has recently been a point of focus, the mechanism of inflammasome activation in HF has not yet been elucidated. METHODS: In this study, we investigated the expression of inflammasome proteins in a rat thoracic aorta constriction (TAC) model and cultured cardiac fibroblasts with stimulation of norepinephrine (NE). RESULTS: Our results showed that levels of inflammasome proteins in the myocardial of TAC rats were elevated. By blocking ß-adrenergic signaling in the rats, inflammasome activation was suppressed and heart function was improved. The stimulation of cultured cardiac fibroblasts with NE activated inflammasome in vitro, which was abrogated by the inhibition of the calcium channels and reactive oxygen species (ROS). The activation of inflammasome by NE promoted cardiac fibrosis, whereas the inhibition of the calcium channels, ROS, and inflammasome reduced this effect. CONCLUSIONS: The present study indicated that activation of inflammasome by ß-adrenergic signaling promotes cardiac fibrosis. Therefore, modulation of inflammasome during HF might provide a novel strategy to treat this disease.

Comparisons of efficacy, safety, and recurrence risk factors of paroxysmal and persistent atrial fibrillation catheter ablation using robotic magnetic navigation system.

BACKGROUND: No data exist on comparisons of efficacy, safety, and recurrence risk factors of paroxysmal and persistent atrial fibrillation (AF) ablation using robotic magnetic navigation system (MNS), respectively. METHODS: About 151 AF patients were prospectively enrolled and divided into paroxysmal AF group (n = 102) and persistent AF group (n = 49). Circumferential pulmonary vein antrum isolation (CPVI) was performed in all patients. Linear ablation at the left atrial roof and mitral isthmus was performed in patients with persistent AF in addition to CPVI. The procedural time, X-ray exposure time, acute and long-term success rates of CPVI, and procedure-related complications were analyzed. The AF recurrence rates in the two groups were compared during 1 year, and Cox regression was used to analyze the recurrence risk factors. RESULTS: The acute success rates of CPVI in the two groups were 98.04% and 97.96%, respectively. There were no significant differences in the procedural time, X-ray exposure time, and ablation time between the two groups (P > 0.05). No serious complications appeared in either group. The AF ablation success rates were 70.6% and 57.1% for the paroxysmal and persistent groups respectively at 12-month follow-up (P = 0.102). AF duration and coronary heart disease prior to ablation were associated with the higher AF recurrence in patients with persistent AF. CONCLUSION: Ablation using MNS is effective and safe both in patients with paroxysmal and persistent AF. AF duration and coronary heart disease prior to ablation are two independent risk factors of AF recurrence in patients with persistent AF postoperatively.

The Impact of Left Atrial Size in Catheter Ablation of Atrial Fibrillation Using Remote Magnetic Navigation.

OBJECTIVE: The objective of this study was to investigate the impact of left atrial (LA) size for the ablation of atrial fibrillation (AF) using remote magnetic navigation (RMN). METHODS: A total of 165 patients with AF who underwent catheter ablation using RMN were included. The patients were divided into two groups based on LA diameter. Eighty-three patients had small LA (diameter <40 mm; Group A), and 82 patients had a large LA (diameter ≥40 mm; Group B). RESULTS: During mapping and ablation, X-ray time (37.0 (99.0) s vs. 12 (30.1) s, P < 0.001) and X-ray dose (1.4 (2.7) gy·cm2 vs. 0.7 (2.1) gy·cm2, P=0.013) were significantly higher in Group A. No serious complications occurred in any of the patients. There was no statistical difference in the rate of first anatomical attempt of pulmonary vein isolation between the two groups (71.1% vs. 57.3%, P=0.065). However, compared with Group B, the rate of sinus rhythm was higher (77.1% vs. 58.5%, P < 0.001) during the follow-up period. More patients in Group A required a sheath adjustment (47/83 vs. 21/82, P < 0.001), presumably due to less magnets positioned outside of the sheath. In vitro experiments with the RMN catheter demonstrated that only one magnet exposed created the sheath affects which influenced the flexibility of the catheter. CONCLUSIONS: AF ablation using RMN is safe and effective in both small and large LA patients. Patients with small LA may pose a greater difficulty when using RMN which may be attributed to the fewer magnets beyond the sheath. As a result, the exposure of radiation was increased. This study found that having at least two magnets of the catheter positioned outside of the sheath can ensure an appropriate flexibility of the catheter.

Autophagy promotes apoptosis of mesenchymal stem cells under inflammatory microenvironment.

BACKGROUND: Mesenchymal stem cells (MSCs) have been widely applied to treat various inflammatory diseases. Inflammatory cytokines can induce both apoptosis and autophagy in MSCs. However, whether autophagy plays a pro- or con-apoptosis effect on MSCs in an inflammatory microenvironment has not been clarified. METHODS: We inhibited autophagy by constructing MSCs with lentivirus containing small hairpin RNA to knockdown Beclin-1 and applied these MSCs to a model of sepsis to evaluate therapeutic effect of MSCs. RESULTS: Here we show that inhibition of autophagy in MSCs increases the survival rate of septic mice more than control MSCs, and autophagy promotes apoptosis of MSCs during application to septic mice. Further study demonstrated that autophagy aggravated tumor necrosis factor alpha plus interferon gamma-induced apoptosis of MSCs. Mechanically, autophagy inhibits the expression of the pro-survival gene Bcl-2 via suppressing reactive oxygen species/mitogen-activated protein kinase 1/3 pathway. CONCLUSIONS: Our findings indicate that an inflammatory microenvironment-induced autophagy promotes apoptosis of MSCs. Therefore, modulation of autophagy in MSCs would provide a novel approach to improve MSC survival during immunotherapy.

Antihypertensive treatment improves left ventricular diastolic function in patients with chronic kidney disease.

In patients with chronic kidney disease (CKD), hypertension (HP) is associated with the development of left ventricular (LV) diastolic dysfunction. However, the impact of antihypertensive treatment on LV diastolic function has not been well studied in CKD patients. Recently, two-dimensional speckle-tracking echocardiography (2DSTE) has emerged as a sensitive and quantitative assessment of LV diastolic function. The present study used 2DSTE to investigate the effects of antihypertensive treatment on LV diastolic function in patients with CKD and untreated HP. The study comprised 134 patients with CKD and untreated HP. The patients received blood pressure (BP)-lowering therapy for six months. The patients were clinically and echocardiographically evaluated at baseline and after 6 months of therapy. It was found that the mean systolic BP (SBP) and diastolic BP (DBP) at baseline were 154.0±7.0 and 92.6±10.2 mmHg, respectively, decreasing to 121.2±7.3 and 74.6±10.4 mmHg, respectively (P<0.05 for both) after the 6-month treatment period. Moreover, the mean peak LV strain rate during the isovolumetric relaxation period (SRIVR) and early diastole (SRE) improved following treatment (from 0.23±0.10 to 0.42±0.10 sec-1 and from 0.58±0.25 to 1.07±0.24 sec-1, respectively; P<0.05 for both). Notably, the patients with CKD stage ≥3 were more likely to demonstrate an improvement in diastolic speckle-tracking parameters than those with CKD stage 1 or 2. For the entire population, the change (Δ) in B-type natriuretic peptide (BNP) level correlated with changes in echocardiographic parameters between baseline and follow-up, among which ΔSRIVR presented the highest correlation coefficient (r=-0.73, P<0.01). On multivariate analysis, the independent predictors of ΔSRIVR were found to include baseline CKD stage, SBP and SRIVR. This study demonstrated that LV diastolic function was improved in CKD patients following antihypertensive treatment, particularly in patients with CKD stage ≥3, higher baseline SBP and worse LV diastolic function. These results highlight the importance of BP reduction in the treatment of CKD.

[Changes of open probability of large conductance Ca(2+)-activated K(+) channels in diabetic coronary smooth muscle cells of rats].

OBJECTIVE: To investigate the changes of open probability (Po) of large conductance Ca(2+)-activated K(+) channel (BK channel) in diabetic coronary smooth muscle cells and elucidate the underlying cellular electrophysiology mechanisms of coronary dysfunction. METHODS: Rat coronary smooth muscle cells were isolated from control group and diabetic group. BK single channel currents were recorded by patch clamp technique in inside-out configuration. Open probabilities were calculated and compared between two groups. After exposure to DHS-1, a specific BK channel activator, Po at 0.2 and 1 µmol/L free Ca(2+) were compared between control and diabetic groups. RESULTS: In the presence of 0.2 µmol/L free Ca(2+), the Po at baseline was significantly lower in diabetic rats than in control rats (0.0032 ± 0.0012 vs. 0.095 ± 0.036, P < 0.05). Cytoplasmic application of DSH-1 significantly increased the Po to 0.335 ± 0.096 (P < 0.05 vs. baseline) in control rats, whereas DSH-1 had no effect in diabetic rats (Po = 0.022 ± 0.018, P > 0.05 vs. baseline). In the presence of 1 µmol/L free Ca(2+), the Po at baseline was also significantly lower in diabetic rats than in control rats (0.210 ± 0.055 vs. 0.458 ± 0.077, P < 0.05). Cytoplasmic application of DHS-1 further robustly enhanced Po to 0.823 ± 0.019 (P < 0.05 vs. baseline) in control rats and to 0.446 ± 0.098 in diabetic rats (P < 0.05 vs. baseline of diabetic rats; P < 0.05 vs. control rats with DHS-1). CONCLUSION: The decrease of Po of BK single channel in coronary smooth muscle cells may be a potential cause for coronary dysfunction in diabetic rats.

Molecular mechanisms of diabetic coronary dysfunction due to large conductance Ca2⁺-activated K⁺ channel impairment.

BACKGROUND: Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus. The purpose of this study is to determine the role of vascular large conductance Ca(2+)-activated K(+) (BK) channel activities in coronary dysfunction in streptozotocin-induced diabetic rats. METHODS: Using videomicroscopy, immunoblotting, fluorescent assay and patch clamp techniques, we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats. RESULTS: BK currents (defined as the iberiotoxin-sensitive K(+) component) contribute (65 ± 4)% of the total K(+) currents in freshly isolated coronary smooth muscle cells and > 50% of the contraction of the inner diameter of coronary arteries from normal rats. However, BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats, leading to an increase in coronary artery tension. BK channel activity in response to free Ca(2+) is impaired in diabetic rats. Moreover, cytoplasmic application of DHS-1 (a specific BK channel b(1) subunit activator) robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats. In diabetic rats, the DHS-1 effect was diminished in the presence of 200 nmol/L Ca(2+) and was significantly attenuated in the presence of high free calcium concentration, i.e., 1 mmol/L Ca(2+). Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-b(1) protein expression in diabetic vessels, without altering the BK channel α-subunit expression. Although the cytosolic Ca(2+) concentration of coronary arterial smooth muscle cells was increased from (103 ± 23) nmol/L (n = 5) of control rats to (193 ± 22) nmol/L (n = 6, P < 0.05) of STZ-induced diabetic rats, reduced BK-b(1) expression made these channels less sensitive to intracellular Ca(2+), which in turn led to enhanced smooth muscle contraction. CONCLUSIONS: Our results indicated that BK channels are the key determinant of coronary arterial tone. Impaired BK channel function in diabetes mellitus is associated with down-regulation of BK-b(1) expression and reduction of the b(1)-mediated BK channel activation in diabetic vessels.

[Evaluation of left ventricular function and twist in patients with diabetic cardiovascular autonomic neuropathy by speckle tracking imaging].

OBJECTIVE: To evaluate left ventricular (LV) function and twist in patients with diabetic cardiovascular autonomic neuropathy (CAN) by two-dimensional speckle tracking imaging (STI). METHODS: STI was performed in 56 subjects with type 2 diabetes mellitus (DM) (35 with DM only: group A, 21 with CAN: group B) and 34 normal subjects (Control) from LV short-axis view. LV peak systolic, peak early (E') and peak late (A') diastolic circumferential strain in 18 myocardial segments were measured at the levels of mitral annulus, papillary muscle and apex and the rotation at mitral annulus and apex levels were also measured. LV peak systolic and the ratio of E' and A' of global and three levels, twist, untwisting rate and untwisting half-time were calculated. RESULTS: In group A, compared with control group, LV peak systolic radial circumferential strain has no significant difference (P > 0.05), E'/A' was reduced (P < 0.05), twist at aortic valve closure and twist at mitral valve opening were significantly increased (P < 0.05), untwisting rate reduced, and untwisting half time delayed. In group B, compared with control group and group A, circumferential strain parameters [(-12.64 ± 6.49)% vs. (-19.11 ± 9.98)% and (-21.14 ± 10.13)%, P < 0.05] and E'/A' [(0.90 ± 0.35) vs. (1.24 ± 0.47) and (1.98 ± 0.63), P < 0.05] were significantly decreased, twist at aortic valve closure [(19.08 ± 5.62)° vs. (16.57 ± 2.84)° and (14.36 ± 4.06)°, P < 0.05] and twist at mitral valve opening [(13.99 ± 2.31)° vs. (11.36 ± 2.63)° and (9.04 ± 5.63)°, P < 0.05] were significantly increased, untwisting rate [(0.40 ± 0.28)%/ms vs. (0.46 ± 0.14)%/ms and (0.53 ± 0.21)%/ms, P < 0.05] reduced, and untwisting half time [(489.61 ± 97.14) ms vs. (445.21 ± 54.53) ms and (410.60 ± 50.23) ms, P < 0.05] delayed. CONCLUSION: Speckle tracking imaging could be used to evaluate early changes on LV twist deformation and LV systolic function in patients with type 2 diabetes mellitus.

[Mechanism related to docosahexaenoic acid induced large conductance calcium-activated potassium channel currents increase in coronary smooth muscle cells].

OBJECTIVE: To investigate the mechanism of enhanced large conductance calcium-activated potassium channel currents (BK) in coronary smooth muscle cells (SMCs) by docosahexaenoic acid (DHA). METHODS: Coronary SMCs were isolated by enzyme digestion. Potassium channels in coronary SMCs were identified by applications of different potassium blockers. Effects of DHA and its metabolite 16, 17-epoxydocosapentaenoic acid (16, 17-EDP) on BK channels in the absence and presence of cytochrome P450 epoxygenase inhibitor SKF525A were studied by patch clamp in whole-cell configuration. RESULTS: BK channels were widely distributed in SMCs, and BK currents in normal SMCs accounted for (64.2 ± 2.7)% of total potassium currents (n = 20). DHA could activate BK channels, and its 50% effective concentration (EC(50)) was (0.23 ± 0.03) µmol/L, however, the effect of DHA on BK channels was abolished after SMCs were incubated with cytochrome P450 epoxygenase inhibitor SKF525A. 16, 17-EDP, a metabolite of DHA, could reproduce the effects of DHA on BK channels, and its EC(50) was (19.7 ± 2.8) nmol/L. CONCLUSION: DHA and metabolites can activate BK channels and dilate coronary arteries through activating cytochrome P450 epoxygenase pathway.

[Regulation of vascular tension in diabetic coronary artery by large conductance Ca(2+)-activated K(+) channel in rats].

OBJECTIVE: to investigate the regulation in vascular tension of diabetic coronary artery by large conductance Ca(2+)-activated K(+) channel (BK channel) and to elucidate the mechanisms of coronary dysfunctions due to diabetes. METHODS: regulation of vascular tension in normal coronary artery was evaluated by videomicroscopy system. Streptozotocin-induced rat diabetic animal model was established successfully by intraperitoneal injection. Coronary smooth muscle cells were isolated by enzyme digestion. The BK currents in control and diabetic groups were recorded by patch clamp technique in whole cell configuration. Changes of vascular tension in normal and diabetic coronary arteries were assayed by multi-wire myograph system. RESULTS: more than 50% was contracted in inner diameters of coronary arteries when 100 nmol/L IBTX, a specific BK channel blocker, was applied. In comparison with normal group, the BK current densities in diabetic group significantly decreased when test potentials were more than 60 mV (P < 0.05). The BK current densities at 150 mV in normal group and diabetic group were (275 ± 40) pA/pF and (70 ± 10) pA/pF respectively. When 100 mmol/L KCl was washed out, vascular tensions of normal and diabetic coronary artery were (398 ± 38) mg and (390 ± 35) mg respectively (P > 0.05); however, when 100 nmol/L IBTX was added, the vascular tensions of normal and diabetic coronary artery were (395 ± 40) mg and (50 ± 7) mg (P < 0.05). CONCLUSION: BK channels play an important role in the regulation of coronary vascular tension, whereas BK channels in diabetic coronary artery are dysfunction, BK currents decrease and vascular tensions increase.

[Changes of large conductance Ca(2+)-activated K(+) channels on coronary smooth muscle cells from diabetic rats].

OBJECTIVE: To investigate the changes of large conductance Ca(2+)-activated K(+) channel (BK channel) on coronary smooth muscle cells from diabetic rats. METHODS: Streptozotocin-induced rat diabetic animal model was used. Coronary smooth muscle cells were isolated by enzyme digestion. BK currents in control and diabetic groups were recorded by patch clamp technique in whole cell configuration, and BK channel protein expression was detected by Western blot. Calcium concentration was measured by fluorescence assay. RESULTS: Compared with control group, BK current densities in diabetic group were significantly decreased when test potentials > 100 mV (P < 0.05). BK current densities were (275 ± 40) pA/pF in control group (n = 8) and (70 ± 10) pA/pF in diabetic group (n = 6) at 150 mV test potentials. α-subunit protein expression was similar between the groups (P > 0.05), however, ß1-subunit protein expression was significantly reduced in diabetic group than in control group (P < 0.05). Calcium concentrations were significantly increased in diabetic group control group (151 ± 18) nmol/L (n = 6) than in control group (92 ± 7) nmol/L (n = 5, P < 0.05). CONCLUSION: Observed ß1-subunit downregulation, BK current density decrease and cytosolic calcium concentration increase in smooth muscle cells of diabetic coronary arteries may be associated with coronary dysfunction in diabetic rats.

[Clinical characteristics of severe chronic heart failure patients with normal blood B-type natriuretic peptide].

OBJECTIVE: To investigate the clinical features of severe chronic heart failure patients with normal B-type natriuretic peptide (BNP). METHODS: A total of 57 patients with severe chronic heart failure (New York Heart Association class III and IV) were included in this prospective control study from Dec. 2002 to Oct. 2009. Group A included 13 patients with normal BNP (< 100 ng/L) and group B included 44 patients with increased BNP (> 100 ng/L). Group A patients were followup for (19.6 ± 14.7) months and group B patients for (72.5 ± 17.1) months. RESULTS: The baseline clinical characteristics of two groups were comparable. Left ventricular end diastolic diameter (LVEDd) of group A was larger than group B [(70.56 ± 4.33) mm vs.(63.73 ± 3.75) mm, P < 0.05], the left ventricular ejection fraction (LVEF) of group A was lower than group B [(24.16 ± 2.50)% vs. (28.49 ± 2.63)%, P < 0.05]. The number of patents tolerating metoprolol in group A is lower than in group B (7/13 vs. 39/44, P < 0.05), and the tolerant dose of metoprolol in group A is lower than in group B [(12.5 ± 6.25) mg/d vs. (24.20 ± 11.22) mg/d, P < 0.05]. The level of BNP in group B were significantly higher at acute stages than at remission stages [(962.73 ± 165.00) ng/L vs. (876.24 ± 167.70) ng/L, P < 0.05], but remained unchanged in group A [(74.03 ± 11.18) ng/L vs. (71.38 ± 11.68) ng/L, P > 0.05]. The mortality of group A was higher than group B (11/12 vs. 6/44, P < 0.05). The binary logistic regression analysis (backward) showed that normal B-type natriuretic peptide was an independent predictor of cardiovascular mortality in patients with severe chronic heart failure (OR = 45.488, 95%CI = 5.322 - 388.791). CONCLUSION: Normal BNP in patients with severe chronic heart failure suggests the exhaustion of BNP secretion and associated poor prognosis.

[Time distribution of ventricular arrhythmias in patients with Brugada syndrome].

OBJECTIVE: To study the characterization of time distribution of ventricular arrhythmias in patients with Brugada syndrome (BrS) using Holter monitoring and ICD follow-up. METHODS: Patients with BrS [all male, mean age (41.07 +/- 11.49) years], were divided into ventricular fibrillation (VF) group (n = 7) and no ventricular fibrillation (N-VF) group (n = 7). Premature ventricular capture (PVC) and VF episodes were detected by Holter monitoring and ICD recording. RESULTS: The 24 hours total number of PVCs ranged from 0 to 74 (mean 9.61 +/- 17.23) in most of the patients and were similar between VF group and N-VF group. The percentage of PVC episodes in VF group was significantly higher than that in N-VF group from nocturnal time to early morning (22:00 to 7:00, 98.67% vs. 44.14%, P < 0.01). There were total 75 VF episodes during (23.18 +/- 17.96) months' follow-up in 5 patients with BrS, 93.3% of which occurred from nocturnal time to early morning (22:00 to 7:00). CONCLUSIONS: The episodes of PVC were enriched from nocturnal time to early morning in BrS patients, this time distribution could be a new noninvasive risk stratification factor for BrS. The episodes of VF in BrS patients were also enriched from nocturnal time to early morning and this time characteristic of episodes of VF could be used to guide drug therapy.

[The electrophysiological study and implantable cardioverter defibrillator therapy for the patients with Brugada syndrome].

OBJECTIVE: Clinical observation of electrophysiological study and implantable cardioverter defibrillator (ICD) therapy in patients with Brugada syndrome. METHODS: Ten patients (all male) with Brugada wave (spontaneous or propafenone test positive in ECG) underwent electrophysiological study (EPS). The mean age was (41 +/- 10) years. They had no structural heart disease with echocardiogram and the angiogram work-up. The ICD implanted in the patients with EPS-induced ventricular fibrillation in those who were available. RESULTS: Three patients had the history of familial sudden cardiac death (SCD). Four patients had repeated syncope episodes, two of them had documented ventricular fibrillation during syncope episodes. The AH and HV intervals were 50 - 124 (86 +/- 21) ms and 41 - 84 (58 +/- 15) ms. The ventricular fibrillation was induced in four patients with syncope and atrioventricular reentry tachycardia in one patient with palpitation. Three patients had spontaneous or inducible atrial fibrillation. The ICD implanted in three patients with inducible ventricular fibrillation. Due to economic issue, one patient without ICD implantation had got SCD during follow-up. The patient with atrioventricular reentry tachycardia underwent a successful left atrioventricular accessory pathway ablation. CONCLUSION: The Brugada patients with syncope and high rate of inducible ventricular fibrillation in EPS are the high risk population for SCD, in whom ICD should implant promptly to prevent SCD.