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1.
Am J Physiol Heart Circ Physiol ; 326(3): H670-H688, 2024 Mar 01.
Article in English | MEDLINE | ID: mdl-38133623

ABSTRACT

Modulation of the renin-angiotensin-aldosterone system is a foundation of therapy for cardiovascular and kidney diseases. Excess aldosterone plays an important role in cardiovascular disease, contributing to inflammation, fibrosis, and dysfunction in the heart, kidneys, and vasculature through both genomic and mineralocorticoid receptor (MR)-mediated as well as nongenomic mechanisms. MR antagonists have been a key therapy for attenuating the pathologic effects of aldosterone but are associated with some side effects and may not always adequately attenuate the nongenomic effects of aldosterone. Aldosterone is primarily synthesized by the CYP11B2 aldosterone synthase enzyme, which is very similar in structure to other enzymes involved in steroid biosynthesis including CYP11B1, a key enzyme involved in glucocorticoid production. Lack of specificity for CYP11B2, off-target effects on the hypothalamic-pituitary-adrenal axis, and counterproductive increased levels of bioactive steroid intermediates such as 11-deoxycorticosterone have posed challenges in the development of early aldosterone synthase inhibitors such as osilodrostat. In early-phase clinical trials, newer aldosterone synthase inhibitors demonstrated promise in lowering blood pressure in patients with treatment-resistant and uncontrolled hypertension. It is therefore plausible that these agents offer protection in other disease states including heart failure or chronic kidney disease. Further clinical evaluation will be needed to clarify the role of aldosterone synthase inhibitors, a promising class of agents that represent a potentially major therapeutic advance.


Subject(s)
Heart Diseases , Hypertension, Renal , Nephritis , Humans , Cytochrome P-450 CYP11B2/genetics , Cytochrome P-450 CYP11B2/metabolism , Aldosterone/pharmacology , Hypothalamo-Hypophyseal System/metabolism , Pituitary-Adrenal System/metabolism , Hypertension, Renal/drug therapy , Renin-Angiotensin System , Mineralocorticoid Receptor Antagonists/therapeutic use , Mineralocorticoid Receptor Antagonists/pharmacology , Heart Diseases/drug therapy
2.
Eur Heart J ; 44(37): 3640-3651, 2023 10 01.
Article in English | MEDLINE | ID: mdl-37674356

ABSTRACT

For decades, heart failure with preserved ejection fraction (HFpEF) proved an elusive entity to treat. Sodium-glucose cotransporter 2 (SGLT2) inhibitors have recently been shown to reduce the composite of heart failure hospitalization or cardiovascular death in patients with HFpEF in the landmark DELIVER and EMPEROR-Preserved trials. While improvements in blood sugar, blood pressure, and attenuation of kidney disease progression all may play some role, preclinical and translational research have identified additional mechanisms of these agents. The SGLT2 inhibitors have intriguingly been shown to induce a nutrient-deprivation and hypoxic-like transcriptional paradigm, with increased ketosis, erythropoietin, and autophagic flux in addition to altering iron homeostasis, which may contribute to improved cardiac energetics and function. These agents also reduce epicardial adipose tissue and alter adipokine signalling, which may play a role in the reductions in inflammation and oxidative stress observed with SGLT2 inhibition. Emerging evidence also indicates that these drugs impact cardiomyocyte ionic homeostasis although whether this is through indirect mechanisms or via direct, off-target effects on other ion channels has yet to be clearly characterized. Finally, SGLT2 inhibitors have been shown to reduce myofilament stiffness as well as extracellular matrix remodelling/fibrosis in the heart, improving diastolic function. The SGLT2 inhibitors have established themselves as robust, disease-modifying therapies and as recent trial results are incorporated into clinical guidelines, will likely become foundational in the therapy of HFpEF.


Subject(s)
Diabetes Mellitus, Type 2 , Heart Failure , Sodium-Glucose Transporter 2 Inhibitors , Humans , Diabetes Mellitus, Type 2/drug therapy , Heart Failure/drug therapy , Pericardium , Sodium-Glucose Transporter 2 Inhibitors/therapeutic use , Sodium-Glucose Transporter 2 Inhibitors/pharmacology , Stroke Volume/physiology
3.
Cardiovasc Diabetol ; 22(1): 152, 2023 06 28.
Article in English | MEDLINE | ID: mdl-37380983

ABSTRACT

BACKGROUND: The cardiovascular (CV) benefits of sodium-glucose transport protein 2 inhibitors have been attributed, in part, to cardiac reverse remodelling. The EMPA-HEART CardioLink-6 study reported that sodium-glucose cotransporter-2 inhibition for 6 months with empagliflozin was associated with a significant reduction in left ventricular mass indexed to body surface area (LVMi). In this sub-analysis, we evaluated whether baseline LVMi may influence how empagliflozin affects cardiac reverse remodelling. METHODS: A total of 97 patients with type 2 diabetes and coronary artery disease were randomized to empagliflozin (10 mg/d) or matching placebo for 6 months. The study cohort was divided into those whose baseline LVMi was ≤ 60 g/m2 and those who had a baseline LVMi > 60 g/m2. Subgroup comparisons were conducted using a linear regression model adjusted for baseline values (ANCOVA) that included an interaction term between LVMi subgroup and treatment. RESULTS: Baseline LVMi was 53.3 g/m2 (49.2-57.2) and 69.7 g/m2 (64.2-76.1) for those with baseline ≤ 60 g/m2 (n = 54) and LVMi > 60 g/m2 (n = 43) respectively. The adjusted difference of LVMi regression between those randomized to empagliflozin and placebo were - 0.46 g/m2 (95% CI: -3.44, 2.52, p = 0.76) in the baseline LVMi ≤ 60 g/m2 subgroup and - 7.26 g/m2 (95% CI: -11.40, -3.12, p = 0.0011) in the baseline LVMi > 60 g/m2 subgroup (p-for-interaction = 0.007). No significant associations were found between baseline LVMi and 6-month change in LV end systolic volume-indexed (p-for-interaction = 0.086), LV end diastolic volume-indexed (p-for-interaction = 0.34), or LV ejection fraction (p-for-interaction = 0.15). CONCLUSIONS: Patients with higher LVMi at baseline experienced greater LVM regression with empagliflozin.


Subject(s)
Coronary Artery Disease , Diabetes Mellitus, Type 2 , Humans , Diabetes Mellitus, Type 2/diagnosis , Diabetes Mellitus, Type 2/drug therapy , Heart , Benzhydryl Compounds/adverse effects
4.
Curr Opin Cardiol ; 38(2): 88-93, 2023 03 01.
Article in English | MEDLINE | ID: mdl-36718618

ABSTRACT

PURPOSE OF REVIEW: Factor XI (FXI) inhibitors were developed to address unmet needs and limitations of current anticoagulants and are currently being studied in several indications. In this paper, we review the rationale for the development of these agents and summarize what clinicians should know about drugs that target FXI. RECENT FINDINGS: Patients with FXI deficiency may have a lower risk of venous thromboembolism and cardiovascular events and have a variable but generally mild bleeding diathesis. FXI has been proposed as a target for anticoagulants due to the potential for reduction in thrombosis with a lower risk of bleeding than current anticoagulant agents. Several classes of drugs that target FXI are under development, of which three classes (small molecule inhibitors, antisense oligonucleotides and monoclonal antibodies) have been studied in Phase II trials. At least three large Phase III trial programs are planned or are underway, and will study the efficacy and safety of FXI inhibitors in tens of thousands of patients across a variety of indications including atrial fibrillation, stroke and cancer-associated venous thromboembolism. SUMMARY: FXI inhibitors were developed with the hope of attenuating thrombosis with reduced bleeding/impairment of haemostasis. These agents have shown promise in preliminary trials with a low rate of bleeding. Ongoing Phase III investigations will inform the utility of these agents in clinical practice.


Subject(s)
Thrombosis , Venous Thromboembolism , Humans , Factor XI , Venous Thromboembolism/drug therapy , Venous Thromboembolism/prevention & control , Anticoagulants/adverse effects , Hemorrhage/chemically induced , Hemorrhage/prevention & control
5.
Malar J ; 22(1): 278, 2023 Sep 19.
Article in English | MEDLINE | ID: mdl-37726804

ABSTRACT

After a period of unprecedented progress against malaria in the 2000s, halving the global disease burden by 2015, gains overall in sub-Saharan Africa have slowed and even reversed in some places, beginning well before the COVID-19 pandemic. The highly effective drugs, treated nets, and diagnostics that fueled the initial progress all face some threats to their effectiveness, and global funding to maintain and increase their use over the long term is not guaranteed. Malaria vaccines are among the most promising new interventions that could accelerate the elimination of malaria. Vaccines are still in early stages of rollout in children, the age group (along with pregnant women) that has been the focus of malaria strategies for a century. At the same time, over the past decade, a case has been made, based largely on evidence from verbal autopsies in at least a few high-transmission areas, that the malaria death rate among adults has been greatly underestimated. Could vaccinating adults help to bring down the adult malaria mortality rate, contribute to reduced transmission, or both? A randomized trial of a malaria vaccine is proposed in Sierra Leone, a highly endemic setting, to shed light on this proposition.


Subject(s)
COVID-19 , Malaria Vaccines , Malaria , Pregnancy , Child , Humans , Adult , Female , Pandemics , COVID-19/prevention & control , Malaria/prevention & control , Autopsy
6.
Eur Heart J ; 43(31): 2931-2945, 2022 08 14.
Article in English | MEDLINE | ID: mdl-35713973

ABSTRACT

Despite existing treatments, patients with heart failure and chronic kidney disease (CKD) remain at high risk for adverse outcomes and progression to end-stage disease. Steroidal mineralocorticoid receptor antagonists (MRAs) such as spironolactone and eplerenone reduce mortality but remain under-prescribed due to the perceived risk of hyperkalaemia and hormonal side effects. The discovery of non-steroidal MRAs represents a major new dimension in cardiorenal disease therapy. Non-steroidal MRAs have high affinity and specificity for the mineralocorticoid receptor (MR) and differ from both steroidal agents and each other with respect to important physiochemical, pharmacodynamic, and pharmacokinetic parameters. Similar to their steroidal counterparts, they have beneficial anti-inflammatory, anti-remodelling, and anti-fibrotic properties in the kidneys, heart, and vasculature. There are several non-steroidal MRAs under development and clinical assessment; of these, only esaxerenone and finerenone are approved for treatment globally. In Japan, esaxerenone is approved for essential hypertension and has been studied in diabetic nephropathy. Compared with steroidal MRAs, finerenone more potently inhibits MR co-regulator recruitment and fibrosis and distributes more evenly between the heart and kidneys. The landmark Phase III trials FIGARO-DKD and FIDELIO-DKD demonstrated that finerenone-reduced major kidney and cardiovascular events on top of maximally tolerated renin-angiotensin-aldosterone system inhibition in patients with CKD associated with Type 2 diabetes. Non-steroidal MRAs are currently under evaluation in heart failure and for synergistic treatment with sodium-glucose contransporter 2 inhibitors. These ground-breaking agents could become an important therapy across the spectrum of cardiorenal disease.


Subject(s)
Diabetes Mellitus, Type 2 , Heart Failure , Renal Insufficiency, Chronic , Diabetes Mellitus, Type 2/drug therapy , Humans , Hypertension, Renal , Mineralocorticoid Receptor Antagonists/therapeutic use , Mineralocorticoids/therapeutic use , Naphthyridines/pharmacology , Naphthyridines/therapeutic use , Nephritis , Receptors, Mineralocorticoid/therapeutic use , Renal Insufficiency, Chronic/complications , Renal Insufficiency, Chronic/drug therapy
7.
Am J Physiol Endocrinol Metab ; 323(3): E254-E266, 2022 09 01.
Article in English | MEDLINE | ID: mdl-35830687

ABSTRACT

Sex differences in the prevalence and development of diabetes and associated cardiometabolic complications are well established. The objective of this study was to analyze the effects of estrogen on the maintenance of ß-cell health/function and atherosclerosis progression, using a mouse model of hyperglycemia-induced atherosclerosis, the ApoE-/-:Ins2+/Akita mouse. ApoE-/-:Ins2+/Akita mice exhibit sexual dimorphism in the control of blood glucose levels. Male ApoE-/-:Ins2+/Akita mice are chronically hyperglycemic due to a significant reduction in pancreatic ß-cell mass. Female mice are only transiently hyperglycemic, maintain ß-cell mass, and blood glucose levels normalize at 35 ± 1 days of age. To determine the effects of estrogen on pancreatic ß-cell health and function, ovariectomies and estrogen supplementation experiments were performed, and pancreatic health and atherosclerosis were assessed at various time points. Ovariectomized ApoE-/-:Ins2+/Akita mice developed chronic hyperglycemia with significantly reduced ß-cell mass. To determine whether the observed effects on ovariectomized ApoE-/-:Ins2+/Akita mice were due to a lack of estrogens, slow-releasing estradiol pellets were inserted subcutaneously. Ovariectomized ApoE-/-:Ins2+/Akita mice treated with exogenous estradiol showed normalized blood glucose levels and maintained ß-cell mass. Exogenous estradiol significantly reduced atherosclerosis in both ovariectomized female and male ApoE-/-:Ins2+/Akita mice relative to controls. Together, these findings suggest that estradiol confers significant protection to pancreatic ß-cell health and can directly and indirectly slow the progression of atherosclerosis.NEW & NOTEWORTHY This study examines the effect(s) of estrogen on ß cell and cardiometabolic health/function in a novel mouse model of hyperglycemia-induced atherosclerosis (ApoE-/-:Ins2+/Akita). Using a combination of estrogen deprivation (ovariectomy) and supplementation strategies, we quantify effects on glucose homeostasis and atherogenesis. Our results clearly show a protective role for estrogen on pancreatic ß-cell health and function and glucose homeostasis. Furthermore, estrogen supplementation dramatically reduces atherosclerosis progression in both male and female mice.


Subject(s)
Atherosclerosis , Estrogens , Hyperglycemia , Animals , Atherosclerosis/diagnosis , Atherosclerosis/etiology , Blood Glucose , Disease Models, Animal , Estradiol/pharmacology , Estrogens/pharmacology , Female , Hyperglycemia/complications , Insulin/pharmacology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout, ApoE
8.
J Thromb Thrombolysis ; 53(3): 697-707, 2022 Apr.
Article in English | MEDLINE | ID: mdl-34622377

ABSTRACT

The optimal INR target in patients with mechanical heart valves is unclear. Higher INR targets are often used in Western compared with East Asian countries. The objective of this systematic review and meta-analysis was to summarize the evidence for the efficacy and safety of lower versus higher INR targets in Western and East Asian left-sided mechanical heart valve patients. We searched Western databases including Cochrane CENTRAL, Medline, and Embase as well as Chinese databases including SinoMed, CNKI, and Wanfang Data in addition to grey literature for Randomized Controlled Trials (RCTs) and observational studies. We pooled risk ratios (RRs) using random-effects model. Low and high INR targets were defined by the individual studies. We identified nine RCTs, including six Western (n = 5496) and three East Asian (n = 209) trials, and 17 observational studies, including two Western (n = 3199) and 15 East Asian (n = 5485) studies. In the RCTs, lower compared with higher targets were associated with similar rates of thromboembolism (2.4 vs. 2.3%; RR: 1.14, 95% CI 0.82, 1.60, I2 = 0%) and lower rates of both total bleeding (21.9 vs. 40.9%, RR: 0.46, 95% CI 0.28, 0.78, I2 = 88%) and major bleeding. RCT data showed no statistical heterogeneity by region. These effects were consistent in the observational data. We downgraded the quality of evidence due to serious risk of bias and imprecision. In patients with left-sided contemporary mechanical heart valves, low quality evidence suggests lower INR targets are associated with similar rates of thromboembolism and moderate quality evidence suggests lower rates of bleeding.


Subject(s)
Anticoagulants , Thromboembolism , Anticoagulants/adverse effects , Fibrinolytic Agents , Heart Valves , Hemorrhage/chemically induced , Humans , Vitamin K
9.
J Card Surg ; 37(11): 3543-3549, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35998278

ABSTRACT

BACKGROUND: Sutureless aortic valve replacement (SuAVR) is gaining popularity for the treatment of aortic stenosis. We aimed to describe Canadian cardiac surgeons' practice patterns and perceptions regarding SuAVR. METHODS: Content experts (clinicians and methodologists) developed the survey. Domains in the questionnaire include: respondent characteristics, factors influencing the decision to implant a SuAVR, barriers to SuAVR use, and interest in participating in a trial. RESULTS: A total of 66 cardiac surgeons (median duration of practice: 15 years; range 8-20 years) from 18 hospitals across Canada responded to the survey for a response rate of 84%. Surgeons reported that the following patient characteristics increased the likelihood they would choose SuAVR: hostile root (73%), small annular size (55%), high Society of Thoracic Surgery risk score (42%), older age (40%), to support minimally invasive surgery (25%) and redo-operation (23%). The following patient characteristics made surgeons less likely to pursue SuAVR: young age (73%), low STS score (40%), and large annular size (30%). Reported barriers to SuAVR use included: cost (33%), permanent pacemaker risk (27%) and uncertain durability (12%). Of respondents, 73% were interested in participating in a randomized controlled trial comparing SuAVR with transcatheter aortic valve replacement. CONCLUSIONS: The primary reasons for surgeons selecting SuAVR were high surgical risk and anatomical challenges. Cost is a primary factor limiting SuAVR use.


Subject(s)
Aortic Valve Stenosis , Heart Valve Prosthesis Implantation , Heart Valve Prosthesis , Surgeons , Transcatheter Aortic Valve Replacement , Aortic Valve/surgery , Aortic Valve Stenosis/surgery , Canada , Humans , Risk Factors , Surveys and Questionnaires , Treatment Outcome
10.
Can J Surg ; 65(4): E450-E459, 2022.
Article in English | MEDLINE | ID: mdl-35820696

ABSTRACT

BACKGROUND: Many patients with end-stage kidney disease (ESKD) have valvular heart disease requiring surgery. The optimal prosthetic valve is not established in this population. We performed a systematic review and meta-analysis to assess outcomes of patients with dialysis-dependent ESKD who received mechanical or bioprosthetic valves. METHODS: We searched Cochrane Central, Medline and Embase from inception to January 2020. We performed screening, full-text assessment, risk of bias and data collection, independently and in duplicate. Data were pooled using a random-effects model. RESULTS: We identified 28 observational studies (n = 9857 patients, including 6680 with mechanical valves and 3717 with bioprosthetic valves) with a median follow-up of 3.45 years. Twenty-two studies were at high risk of bias and 1 was at critical risk of bias from confounding. Certainty in evidence was very low for all outcomes except bleeding. Mechanical valves were associated with reduced mortality at 30 days (relative risk [RR] 0.79, 95% confidence interval [CI] 0.65-0.97, I 2 = 0, absolute effect 27 fewer deaths per 1000) and at 6 or more years (mean 9.7 yr, RR 0.83, 95% CI 0.72-0.96, I 2 = 79%, absolute effect 145 fewer deaths per 1000), but increased bleeding (incidence rate ratio [IRR] 2.46, 95% CI 1.41-4.27, I 2 = 59%, absolute effect 91 more events per 1000) and stroke (IRR 1.63, 95% CI 1.21-2.20, I 2 = 0%, absolute effect 25 more events per 1000). CONCLUSION: Mechanical valves were associated with reduced mortality, but increased rate of bleeding and stroke. Given very low certainty for evidence of mortality and stroke outcomes, patients and clinicians may choose prosthetic valves based on factors such as bleeding risk and valve longevity. STUDY REGISTRATION: PROSPERO no. CRD42017081863.


Subject(s)
Bioprosthesis , Heart Valve Diseases , Heart Valve Prosthesis , Stroke , Bioprosthesis/adverse effects , Heart Valve Diseases/surgery , Hemorrhage/etiology , Humans , Renal Dialysis/adverse effects , Stroke/complications
11.
J Card Surg ; 36(12): 4734-4742, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34617322

ABSTRACT

BACKGROUND: Sutureless aortic valve replacement (SuAVR) is an alternative to surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR). This study compares the effectiveness of SuAVR to SAVR and TAVR. METHODS: We searched MEDLINE and EMBASE from inception to July 2021 for studies evaluating SuAVR, SAVR, and TAVR in adults with aortic stenosis. We performed screening, full-text assessment, data collection, and risk of bias evaluation independently and in duplicate. We evaluated risk of bias using by Cochrane and CLARITY's tools, and certainty in evidence using the GRADE framework. Data were pooled using a random-effects model. RESULTS: We identified one randomized and 78 observational studies (n = 60,689; SuAVR vs. SAVR = 39,171, vs. TAVR = 21,518). All studies were at high or unclear risk of bias, with very-low certainty in effect estimates. Compared to TAVR, SuAVR demonstrates no significant difference in mortality at 30-days (odds ratio [OR]: 0.52, 95% confidence interval [CI: 0.85, 1.16], I2 = 0%), but decreased odds at 2-years (OR: 0.39, 95% CI [0.17, 0.88], I2 = 0%). SuAVR also reduced odds of mild paravalvular regurgitation (OR: 0.11, 95% CI [0.06, 0.21], I2 = 50%). Compared to SAVR, SuAVR was associated with a similar mortality at 30-days (OR: 0.99, 95% CI [0.85, 1.16], I2 = 0%) and 2-years (OR: 0.99, 95% CI [0.43-2.30], I2 = 7%). SuAVR significantly increased odds of permanent pacemaker implantation (OR: 2.5, 95% CI [2.25, 2.77], I2 = 0%). Pooled effect estimates were consistent with results from the randomized trial comparing SuAVR and SAVR. CONCLUSION: Based on very-low quality evidence, SuAVR is associated with similar short- and midterm outcomes compared to TAVR and SAVR. Comparative randomized data with long-term follow-up are required to clarify the role of SuAVR.


Subject(s)
Aortic Valve Stenosis , Heart Valve Prosthesis Implantation , Heart Valve Prosthesis , Transcatheter Aortic Valve Replacement , Aortic Valve/surgery , Aortic Valve Stenosis/surgery , Humans , Risk Factors , Treatment Outcome
12.
Cardiovasc Drugs Ther ; 33(3): 339-352, 2019 06.
Article in English | MEDLINE | ID: mdl-31011880

ABSTRACT

BACKGROUND: Clinical guidelines recommend peri-cardioversion anticoagulation in patients with atrial fibrillation (AF). We performed a systematic review and meta-analysis to compare the safety and efficacy of direct oral anticoagulants (DOACs) versus vitamin K antagonists (VKAs) in patients with AF undergoing cardioversion. METHODS: We searched CENTRAL, MEDLINE, and EMBASE for randomized controlled trials (RCTs) and observational studies comparing DOACs to VKAs in patients undergoing cardioversion for AF. We performed title, abstract, and full-text screening, data extraction, and risk of bias evaluation independently and in duplicate. We pooled data using a random effects model and evaluated the overall quality of evidence using Grading of Recommendations Assessment, Development and Evaluation. RESULTS: We identified three eligible RCTs (n = 5203) and 21 observational studies (n = 11,855). The three RCTs and four observational studies were at low risk of bias. In RCTs (mean follow-up, 30 days), thromboembolic events occurred in 0.18% of patients receiving DOACs, as compared with 0.55% receiving VKAs (relative risk [RR] 0.40, 95% CI [0.13, 1.24], moderate quality). Major bleeding occurred in 0.42% of patients receiving DOACs as compared with 0.64% receiving VKAs (RR 0.62, 95% CI [0.28, 1.35], moderate quality), and death occurred in 0.28% of patients receiving DOACs as compared with 0.38% receiving VKAs (RR 0.70, 95% CI [0.23, 2.10], low quality). Confidence in the estimates of effect for observational studies was very low. CONCLUSION: DOACs peri-cardioversion in patients with AF appears safe from both a bleeding and thromboembolic risk perspective. Available evidence supports the use of DOACs as standard of care peri-cardioversion in patients with AF.


Subject(s)
Anticoagulants/administration & dosage , Antithrombins/administration & dosage , Atrial Fibrillation/therapy , Electric Countershock , Stroke/prevention & control , Vitamin K/antagonists & inhibitors , Warfarin/administration & dosage , Administration, Oral , Anticoagulants/adverse effects , Antithrombins/adverse effects , Atrial Fibrillation/diagnosis , Atrial Fibrillation/mortality , Electric Countershock/adverse effects , Hemorrhage/chemically induced , Humans , Observational Studies as Topic , Randomized Controlled Trials as Topic , Risk Assessment , Risk Factors , Stroke/diagnosis , Stroke/mortality , Treatment Outcome , Warfarin/adverse effects
14.
Appl Environ Microbiol ; 84(17)2018 09 01.
Article in English | MEDLINE | ID: mdl-29934331

ABSTRACT

Dissimilatory nitrate reduction to ammonium (DNRA), denitrification, anaerobic ammonium oxidation (anammox), and biological N2 fixation (BNF) can influence the nitrogen (N) use efficiency of rice production. While the effect of N application on BNF is known, little is known about its effect on NO3- partitioning between DNRA, denitrification, and anammox. Here, we investigated the effect of N application on DNRA, denitrification, anammox, and BNF and on the abundance of relevant genes in three paddy soils in Australia. Rice was grown in a glasshouse with N fertilizer (150 kg N ha-1) and without N fertilizer for 75 days, and the rhizosphere and bulk soils were collected separately for laboratory incubation and quantitative PCR analysis. Nitrogen application reduced DNRA rates by >16% in all the soils regardless of the rhizospheric zone, but it did not affect the nrfA gene abundance. Without N, the amount and proportion of NO3- reduced by DNRA (0.42 to 0.52 µg g-1 soil day-1 and 45 to 55%, respectively) were similar to or higher than the amount and proportion reduced by denitrification. However, with N the amount of NO3- reduced by DNRA (0.32 to 0.40 µg g-1 soil day-1) was 40 to 50% lower than the amount of NO3- reduced by denitrification. Denitrification loss increased by >20% with N addition and was affected by the rhizospheric zones. Nitrogen loss was minimal through anammox, while BNF added 0.02 to 0.25 µg N g-1 soil day-1 We found that DNRA plays a significant positive role in paddy soil N retention, as it accounts for up to 55% of the total NO3- reduction, but this is reduced by N application.IMPORTANCE This study provides evidence that nitrogen addition reduces nitrogen retention through DNRA and increases nitrogen loss via denitrification in a paddy soil ecosystem. DNRA is one of the major NO3- reduction processes, and it can outcompete denitrification in NO3- consumption when rice paddies are low in nitrogen. A significant level of DNRA activity in paddy soils indicates that DNRA plays an important role in retaining nitrogen by reducing NO3- availability for denitrification and leaching. Our study shows that by reducing N addition to rice paddies, there is a positive effect from reduced nitrogen loss but, more importantly, from the conversion of NO3- to NH4+, which is the favored form of mineral nitrogen for plant uptake.


Subject(s)
Denitrification/physiology , Nitrates/metabolism , Nitrogen Fixation/physiology , Nitrogen Oxides/metabolism , Nitrogen/metabolism , Australia , Cytochrome c Group/genetics , Fertilizers/analysis , Oryza , Rhizosphere , Soil Microbiology
18.
Sci Rep ; 14(1): 14537, 2024 Jun 24.
Article in English | MEDLINE | ID: mdl-38914592

ABSTRACT

Whether the Main Himalayan Thrust can host a single surface-rupturing event in the Himalaya with a rupture length of > 700 km remains controversial. Previous paleoseismological studies in the Darjeeling-Sikkim Himalaya (DSH) suggested medieval surface-rupturing earthquakes, correlating them with the eleventh-thirteenth century events from Nepal and Bhutan and extending the coseismic rupture length > 700 km. Conversely, there is no rupture evidence of the 1714 Bhutan and 1934 Bihar-Nepal earthquakes in the DSH, resulting in a discrepancy in the rupture extent of the great earthquakes. Consequently, we conducted a paleoseismological investigation across a ~ 10 m-high fault scarp on the Himalayan Frontal Thrust at Chenga village, DSH, revealing a surface-faulting event during 1313-395 BCE. We suggest that the DSH is a 150 km-long independent segment bounded by a transverse ridge and fault and has a recurrence interval of ~ 949-1963 years, which is significantly larger than Nepal (~ 700-900 years) and Bhutan Himalaya (~ 339-761 years).

19.
J Am Coll Cardiol ; 83(7): 755-769, 2024 02 20.
Article in English | MEDLINE | ID: mdl-38355246

ABSTRACT

BACKGROUND: South Asian individuals shoulder a disproportionate burden of cardiometabolic diseases. OBJECTIVES: The purpose of this study was to determine if vascular regenerative cell content varies significantly between South Asian and White European people. METHODS: Between January 2022 and January 2023, 60 South Asian and 60 White European adults with either documented cardiovascular disease or established diabetes with ≥1 other cardiovascular risk factor were prospectively enrolled. Vascular regenerative cell content in venous blood was enumerated using a flow cytometry assay that is based on high aldehyde dehydrogenase (ALDHhi) activity and cell surface marker phenotyping. The primary outcome was the difference in frequency of circulating ALDHhi progenitor cells, monocytes, and granulocytes between the 2 groups. RESULTS: Compared with White European participants, those of South Asian ethnicity were younger (69 ± 10 years vs 66 ± 9 years; P < 0.05), had lower weight (88 ± 19 kg vs 75 ± 13 kg; P < 0.001), and exhibited a greater prevalence of type 2 diabetes (62% vs 92%). South Asian individuals had markedly lower circulating frequencies of pro-angiogenic ALDHhiSSClowCD133+ progenitor cells (P < 0.001) and ALDHhiSSCmidCD14+CD163+ monocytes with vessel-reparative capacity (P < 0.001), as well as proportionally more ALDHhi progenitor cells with high reactive oxygen species content (P < 0.05). After correction for sex, age, body mass index, and glycated hemoglobin, South Asian ethnicity was independently associated with lower ALDHhiSSClowCD133+ cell count. CONCLUSIONS: South Asian people with cardiometabolic disease had less vascular regenerative and reparative cells suggesting compromised vessel repair capabilities that may contribute to the excess vascular risk in this population. (The Role of South Asian vs European Origins on Circulating Regenerative Cell Exhaustion [ORIGINS-RCE]; NCT05253521).


Subject(s)
Diabetes Mellitus, Type 2 , Humans
20.
J Org Chem ; 78(8): 3676-87, 2013 Apr 19.
Article in English | MEDLINE | ID: mdl-23534335

ABSTRACT

A high-yielding stereospecific route to the synthesis of single geometric isomers of diaryl oxime ethers through Suzuki coupling of N-alkoxyimidoyl iodides is described. This reaction occurs with complete retention of the imidoyl halide geometry to give single E- or Z-isomers of diaryl oxime ethers. The Sonogashira coupling of N-alkoxyimidoyl iodides and bromides with a wide variety of terminal alkynes to afford single geometric isomers of aryl alkynyl oxime ethers has also been developed. Several of these reactions proceed through copper-free conditions. The Negishi coupling of N-alkoxyimidoyl halides is introduced. The E and Z configurations of nine Suzuki-coupling products and two Sonogashira-coupling products were confirmed by X-ray crystallography.

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