[Impact of transcatheter aortic valve replacement on renal function in patients with severe aortic stenosis]

Objective: To explore the impact of transcatheter aortic valve replacement (TAVR) on renal function in patients with severe aortic stenosis. Methods: This is a single-center retrospective study. Consecutive patients with severe aortic valve stenosis and received TAVR in Zhongshan Hospital from December 2014 to December 2019 were included. The patients were divided into four groups according to the estimate glomerular filtration rate (eGFR) measured at one day before TAVR, namely eGFR>90 ml·min-1·1.73m-2 group, 6090 ml·min-1·1.73m-2 group, 60 Collapse

Key Words

• Acute kidney recovery
• Aortic valve stenosis
• Renal function
• Transcatheter aortic valve implantation

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[Association between lifestyle-related factors and colorectal adenoma]

Objective: To explore the association between lifestyle-related factors and colorectal adenoma. Methods: Based on the Screening Project of Early Diagnosis and Treatment of Colorectal Cancer in Jiashan county Zhejiang province, from August 2012 to March 2018, information gathered through records on questionnaire and colonoscopic diagnosis were collected from participants with positive results during the primary screening stage. According to the findings of colonoscopy, 11 232 controls without any colorectal diseases and 3 895 cases with colorectal adenoma were included in the study. Multivariate logistic regression models were used to analyze the association between lifestyle-related factors and colorectal adenoma. Results: After adjusting for possible confounding factors, results from multivariate logistic regression analysis showed that smoking, alcohol drinking and obesity were positively related to the risk of colorectal adenoma, with ORs (95%CIs) as 1.38 (1.24-1.54), 1.37 (1.24-1.51) and 1.38 (1.20-1.59) respectively. However, regular aspirin intake was negatively related with the risk of colorectal adenoma (OR=0.65, 95%CI: 0.53-0.80). After stratified by sex and age, data showed that the associations between smoking, alcohol drinking and colorectal adenoma were statistically significant in males, and the association between regular aspirin intake and colorectal adenoma was also statistically significant in older participants (aged 60 years and older). Conclusion: Smoking, alcohol drinking, regular aspirin intake and obesity were associated with colorectal adenoma.

Cryo-electron microscopy structure of human ABCB6 transporter

Human ATP-binding cassette transporter 6 of subfamily B (ABCB6) is an ABC transporter involved in the translocation toxic metals and anti-cancer drugs. Using cryo-electron microscopy, we determined the molecular structure of full-length ABCB6 in an apo state. The structure of ABCB6 unravels the architecture of a full-length ABCB transporter that harbors two N-terminal transmembrane domains which is indispensable for its ATPase activity in our in vitro assay. A slit-like substrate binding pocket of ABCB6 may accommodate the planar shape of porphyrins, and the existence of a secondary cavity near the mitochondrial intermembrane space side would further facilitate substrate release. Furthermore, the ATPase activity of ABCB6 stimulated with a variety of porphyrin substrates showed different profiles in the presence of glutathione (GSH), suggesting the action of a distinct substrate translocation mechanism depending on the use of GSH as a cofactor.

Cryo-electron microscopy structure of CLHM1 ion channel from Caenorhabditis elegans

Calcium homeostasis modulators (CALHMs/CLHMs) comprise a family of pore-forming protein complexes assembling into voltage-gated, Ca2+ -sensitive, nonselective channels. These complexes contain an ion-conduction pore sufficiently wide to permit the passing of ATP molecules serving as neurotransmitters. While their function and structure information is accumulating, the precise mechanisms of these channel complexes remain to be full understood. Here, we present the structure of the Caenorhabditis elegans CLHM1 channel in its open state solved through single-particle cryo-electron microscopy at 3.7-Å resolution. The transmembrane region of the channel structure of the dominant class shows an assembly of 10-fold rotational symmetry in one layer, and its cytoplasmic region is involved in additional twofold symmetrical packing in a tail-to-tail manner. Furthermore, we identified a series of amino acid residues critical for the regulation of CeCLHM1 channel using functional assays, electrophysiological analyses as well as structural-based analysis. Our structure and function analyses provide new insights into the mechanisms of CALHM channels.

Biological background of the genomic variations of cf-DNA in healthy individuals

BACKGROUND

Cell-free DNA (cf-DNA)-based liquid biopsy is emerging as a revolutionary new method in individualized cancer treatment and prognosis monitoring, although detecting early-stage cancers using cf-DNA remains challenging, partially because of the undefined biological background of cf-DNA.

MATERIALS AND METHODS

We investigated somatic mutations in the cf-DNA of 259 cancer-free individuals with a median age of 47 years using an endogenous barcoding duplex method with an ultralow base error rate (2 × 10-7) and compared the variant allele frequencies (VAFs) of these mutations between the cf-DNA and the corresponding blood cell DNA.

RESULTS

Sixty percent (155/259) of the samples showed at least one nonsynonymous mutation on either of two similar target panels covering 508 and 559 cancer-related genes. For individuals older than 50 years of age, the positive rate increased to 76%. Most cf-DNA mutations were also present at similar VAFs in the paired blood cell DNA. The most frequently mutated genes were driver genes of hematologic malignancies, including DNMT3A, TET2, AXSL1, and JAK2. However, the other 58.4% (192/329) of the mutations were likely 'passenger mutations' of clonal hematopoiesis, including mutations in NOTCH2, FAT3, EXT2, ERBB4, and ARID2, which are driver genes of solid tumors.

CONCLUSION

Hematopoietic clone-derived mutations, including 'driver mutations' and 'passenger mutations', are prevalent in the cf-DNA of both healthy individuals and cancer patients and may be a potential source of false positives in the liquid biopsy. Our results also suggest the ineffectiveness for distinguishing clonal hematopoietic mutations of low VAF (≤0.1%) from tumor-derived mutations using conventional next-generation sequencing of blood cell DNA. However, an error correction model with an ultralow error rate and high coverage depth is required for blood cell DNA sequencing, which is difficult and costly to achieve with current technologies.

Unique genetic profiles from cerebrospinal fluid cell-free DNA in leptomeningeal metastases of EGFR-mutant non-small-cell lung cancer: a new medium of liquid biopsy

Background

Leptomeningeal metastases (LM) are more frequent in non-small-cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. Due to limited access to leptomeningeal lesions, the purpose of this study was to explore the potential role of cerebrospinal fluid (CSF) as a source of liquid biopsy in patients with LM.

Patients and methods

Primary tumor, CSF, and plasma in NSCLC with LM were tested by next-generation sequencing. In total, 45 patients with suspected LM underwent lumbar puncture, and those with EGFR mutations diagnosed with LM were enrolled.

Results

A total of 28 patients were enrolled in this cohort; CSF and plasma were available in 26 patients, respectively. Driver genes were detected in 100% (26/26), 84.6% (22/26), and 73.1% (19/26) of samples comprising CSF cell-free DNA (cfDNA), CSF precipitates, and plasma, respectively; 92.3% (24/26) of patients had much higher allele fractions in CSF cfDNA than the other two media. Unique genetic profiles were captured in CSF cfDNA compared with those in plasma and primary tissue. Multiple copy number variations (CNVs) were mainly identified in CSF cfDNA, and MET copy number gain identified in 47.8% (11/23) of patients was the most frequent one, while other CNVs included ERBB2, KRAS, ALK, and MYC. Moreover, loss of heterozygosity (LOH) of TP53 was identified in 73.1% (19/26) CSF cfDNA, which was much higher than that in plasma (2/26, 7.7%; P < 0.001). There was a trend towards a higher frequency of concomitant resistance mutations in patients with TP53 LOH than those without (70.6% versus 33.3%; P = 0.162). EGFR T790M was identified in CSF cfDNA of 30.4% (7/23) of patients who experienced TKI progression.

Conclusion

CSF cfDNA could reveal the unique genetic profiles of LM and should be considered as the most representative liquid biopsy medium for LM in EGFR-mutant NSCLC.

[Effects of transcatheter aortic valve replacement in patients with severe aortic valve stenosis]

Objective: To investigate the effects of transcatheter aortic valve replacement (TAVR) in patients with severe aortic valve stenosis. Methods: The clinical data of 130 patients with severe aortic valve stenosis, who underwent TAVR in our hospital with self-expanding valve between January 1,2010 and October 30, 2016, were analyzed retrospectively. The patients were divided into calcific aortic valve stenosis (CAS) group (112 cases) and non-calcific aortic valve stenosis (NCAS) group (18 cases) according to 3D volume-rendering reconstruction under multiple detector computed tomography before TAVR. The baseline clinical features, imageology results, procedural details, and clinical prognosis were compared between the 2 groups. Results: (1) Compared with CAS group, the patients in NCAS group were younger, had higher proportion of rheumatic heart disease, and less proportion of bicuspid aortic valve morphology (P<0.01 or 0.05). Except for minimum value of sinotubular junction (P=0.017), there were no significant differences in multiple detector computed tomography measurements of aortic valve annulus and aortic root structure between the 2 groups (all P>0.05). (2) Compared with CAS group, the proportions of valve release under rapid pacing and oversized valve release were larger than pre-procedural evaluation, and the proportion of post-dilation was lower in NCAS group (P<0.01 or 0.05). (3) Post-procedural transthoracic echocardiography revealed that left ventricular ejection fraction was higher than baseline level in CAS group (P<0.001), while which was similar in NCAS group (P=0.552). Compared with before TAVR, mean pressure gradient and maximum transvalvular velocity were significantly reduced, aortic valve orifice area was significantly increased, and proportion of moderate to severe aortic regurgitation was significantly reduced after the procedure in both groups (all P<0.01). There were no significant differences in left ventricular ejection fraction, mean pressure gradient, maximum transvalvular velocity, aortic valve orifice area, and proportion of moderate to severe aortic regurgitation after TAVR between the 2 groups (all P>0.05). (4) There were no significant differences in successful rate of device placement and cardiovascular related death within 30 days after TAVR between the 2 groups (105/112 vs. 17/18, P=0.909; 3/112 vs. 1/18, P=0.453, respectively). Conclusion: TAVR is safe and effective for patients with severe aortic valve stenosis.

[Application and evaluation of urine measurement at different times methods for estimating salt intake]

Salt reduction is the most cost-effective population strategy to prevent and control hypertension and cardiovascular disease. Accurate measurement of salt intake is an important basis for implementing salt reduction interventions, while the urine sodium measurement is the most objective method to evaluate salt intake. According to different time spans, it is mainly divided into 24-h urine, overnight urine and spot urine collection methods. This article reviewed the application and evaluation of these three urine measurement methods, and compared their advantages and disadvantages. According to the accuracy and feasibility of different urine measurement methods, it is suggested that the 24-h urine collection method can be applied to the correlation study with small sample size, and the overnight urine method and the spot urine method can be applied to the daily population salt reduction interventions and monitoring activities.

Interplay between the electrostatic membrane potential and conformational changes in membrane proteins

Transmembrane electrostatic membrane potential is a major energy source of the cell. Importantly, it determines the structure as well as function of charge-carrying membrane proteins. Here, we discuss the relationship between membrane potential and membrane proteins, in particular whether the conformation of these proteins is integrally connected to the membrane potential. Together, these concepts provide a framework for rationalizing the types of conformational changes that have been observed in membrane proteins and for better understanding the electrostatic effects of the membrane potential on both reversible as well as unidirectional dynamic processes of membrane proteins.

[HBV genotyping based on key epitopes of PreS1 antigen and its correlation with genotyping by full-length PreS1 sequencing]

Objective: The aim was to investigate the genotype distribution of two major epitopes of large surface protein (PreS1) of hepatitis B in Chinese patients and to explore the association between the genotypes of these two epitopes, and to determine whether PreS1 full-length genotype could be revealed according to the polypeptide sequence of key epitopes. Methods: HBV DNA was extracted from the serum of patients for PCR amplification. 278 samples amplified successfully were sequenced and compared with the known HBV sequences in Genbank to determine the two key epitopes of HBV PreS1 genotype (amino acid epitope 21-47 and 94-117, abbreviated as P21 and P94) and PreS1 full-length genotypes. The correlation among three genotyping approaches was analyzed by Cohen's kappa coefficient to verify the consistency between the key-epitope genotyping and the full-length preS1 genotyping. Results: 232 samples were successfully sequenced. The genotyping based on the kind of P21 epitope protein sequence, 201 cases for genotype C, 23 cases for genotype B and 8 cases for uncertain genotypes and genotyping based on the form of P94 epitope protein sequence, 199 cases for genotype C, 25 cases for genotype B and 8 cases for indeterminate genotypes. Lastly, the genotyping based on sequence of the full-length PreS1 sequence, 207 and 25 cases for genotype C and B. P21 or P94 epitope genotyping and PreS1 full length genotyping were highly consistent, respectively, 96.55% and 96.12%, and the two epitopes (P21and P94) genotyping have parallel consistency (93.10%). Conclusion: In this study, an innovatively genotyping method based on the amino acid sequence of key epitopes was proposed. The genotypes of HBV in china were mainly B and C genotypes, and the genotypes of key conserved epitopes of HBV PreS1 were highly consistent with the full-length genotyping ( > 96%). Moreover, genotyping with one or two key epitopes can be used in place of the full-length genotyping.

[Safety and efficacy of transcatheter aortic valve replacement through transcarotid approach for patients with severe aortic valve stenosis]

Objective: To investigate the safety and efficacy of transcatheter aortic valve replacement(TAVR) through transcarotid approach for patients with severe aortic valve stenosis. Methods: The clinical data of 9 symptomatic severe aortic valve stenosis patients who had high or prohibitive risk for surgery and not suitable for TAVR through femoral artery access,and thus received TAVR through transcarotid approach in our hospital from November 2015 to February 2017 were retrospectively analyzed.The patients were followed up to observe the safety and efficacy of the procedure. Results: There were 4 male and 5 female patients in this cohort, and age was (75.7±8.7) years old. The Society of Thoracic Surgery (STS) scores were (7.9±1.6)%. All patients were treated by left carotid artery approach. One patient experienced valve dislodgement during the procedure and received surgery, and TAVR procedure was successful in the rest 8 patients. Two patients were implanted with permanent pacemaker because of third degree atrioventricular block during the procedure.One patient had cardiac arrest during the procedure and recovered after external chest compression.One patient developed severe carotid stenosis,and there was no clinical manifestation of nerve function deficit after the procedure. All patients were followed up at (30±3) days after the procedure, and there were no adverse events. The modified Rankin scale score was 0. Echocardiography examination showed that the tranvalvular mean gradient was reduced from (63.0±19.2)mmHg(1 mmHg=0.133 kPa) on baseline to (18.1±4.9)mmHg(P<0.001), 4 cases had mild paravalvular leakage, and there was no moderate or severe paravalvular leakage.The NYHA classes was significantly improved at 30 days when compared with before the procedure(2 cases class Ⅱ, 4 cases class Ⅲ,3 cases class Ⅳ before the procedure,and 5 cases classⅠ, 4 cases class Ⅱ after the procedure, P=0.006) , and left ventricular ejection fraction increased from (55.9±13.1)% to (60.4±10.0)% (P=0.030). Conclusion: Our initial experience indicates that transcarotid TAVR is safe and effective for patients with severe aortic valve stenosis.

[Percutaneous renal access for percutaneous nephrolithotomy guided by contrast enhanced ultrasound: a single-center preliminary experience in China]

OBJECTIVE

Contrast enhanced ultrasound (CEUS) is an innovative technique that employs microbubble contrast agents to demonstrate parenchymal perfusion. Ultrasound contrast agent was reported to be directly used in human internal lumen to improve the observation capacity of ultrasound. However, CEUS has never been reported to be used in the guidance of percutaneous renal access in percutaneous nephrolithotomy (PCNL). This study aimed to assess the efficacy of CEUS-guided renal access in PCNL.

METHODS

In this retrospective study, percutaneous renal access was performed under real-time monitoring of CEUS during PCNL in a cohort of 20 patients with renal stones at Peking University First Hospital. Data regarding patients' demographic and clinical characteristics, therapeutic regimens, and postoperative information were collected from a comprehensive database containing comprehensive medical records of the patients undergoing PCNL. Briefly, the procedure was as follows. With the patient under general anesthesia, renal access was established by the guidance of CEUS. Afterwords, holmium laser, pneumatic or ultrasonic lithotripsy was used by the same urologist. The patient demographics, stone characteristics and procedure details were noted. Finally, appropriate statistical analyses were performed to evaluate the effectiveness and safety of the CEUS-guided percutaneous renal access in PCNL.

RESULTS

All the 20 patients underwent PCNL successfully with the help of CEUS guidance for tract creation. The collecting system was successfully accessed in all the patients, and only one patient underwent re-puncture. All the patients approached through a middle-pole percutaneous access. The median puncture time was 3.9 (2.9-4.6) min, and the median operating time was 112 (98.5-134.5) min. The preliminary stone-free rate of PCNL was 95.0% (19/20) as shown by the kidney, ureter, and bladder (KUB) radiographs 48 h postoperation, and the median decline in hemoglobin level was 10 (5.5-14.5) g/L. Two patients had transient postoperative fever and responded well to antibiotics. In addition, no other major complications were observed.

CONCLUSION

CEUS is a safe and effective alternative way of guidance for percuta-neous renal access for PCNL beginners. It makes this procedure more visualized and simpler, and produces clearer images than common ultrasonic ones. PCNL beginners might benefit from this method to shorten the learning curve of PCNL, while it warrants further comparative studies to clarify.

Thermodynamic secrets of multidrug resistance: A new take on transport mechanisms of secondary active antiporters

Multidrug resistance (MDR) presents a growing challenge to global public health. Drug extrusion transporters play a critical part in MDR; thus, their mechanisms of substrate recognition are being studied in great detail. In this work, we review common structural features of key transporters involved in MDR. Based on our membrane potential-driving hypothesis, we propose a general energy-coupling mechanism for secondary-active antiporters. This putative mechanism provides a common framework for understanding poly-specificity of most-if not all-MDR transporters.

Energy coupling mechanisms of AcrB-like RND transporters

Prokaryotic AcrB-like proteins belong to a family of transporters of the RND superfamily, and as main contributing factor to multidrug resistance pose a tremendous threat to future human health. A unique feature of AcrB transporters is the presence of two separate domains responsible for carrying substrate and generating energy. Significant progress has been made in elucidating the three-dimensional structures of the homo-trimer complexes of AcrB-like transporters, and a three-step functional rotation was identified for this class of transporters. However, the detailed mechanisms for the transduction of the substrate binding signal, as well as the energy coupling processes between the functionally distinct domains remain to be established. Here, we propose a model for the interdomain communication in AcrB that explains how the substrate binding signal from the substrate-carrier domain triggers protonation in the transmembrane domain. Our model further provides a plausible mechanism that explains how protonation induces conformational changes in the substrate-carrier domain. We summarize the thermodynamic principles that govern the functional cycle of the AcrB trimer complex.

Structural dynamics of Giα protein revealed by single molecule FRET

The heterotrimeric G proteins (Gαβγ) act as molecular switches to mediate signal transduction from G protein-coupled receptors to downstream effectors. Upon interaction with an activated receptor, G protein exchanges its bound GDP with GTP, stimulating downstream signal transmission. Release of GDP requires a structural rearrangement between the GTPase domain and helical domain of the Gα subunit. Here, we used single molecule fluorescence resonance energy transfer (smFRET) technique to study the conformational dynamics of these two domains in the apo state and in the binding of different ligands. Direct imaging of individual molecules showed that the G_iα subunit is highly dynamic, and at least three major conformations of G_iα could be observed in the apo state. Upon binding of GDP, G_iα becomes dramatically less dynamic, resulting in a closed conformation between the two domains. We postulate that changes between the three conformations are sequential, and the three conformations appear to have distinct affinities toward GDP.

Crystal structure of E. coli apolipoprotein N-acyl transferase

In Gram-negative bacteria, lipid modification of proteins is catalysed in a three-step pathway. Apolipoprotein N-acyl transferase (Lnt) catalyses the third step in this pathway, whereby it transfers an acyl chain from a phospholipid to the amine group of the N-terminal cysteine residue of the apolipoprotein. Here, we report the 2.6-Å crystal structure of Escherichia coli Lnt. This enzyme contains an exo-membrane nitrilase domain fused to a transmembrane (TM) domain. The TM domain of Lnt contains eight TM helices which form a membrane-embedded cavity with a lateral opening and a periplasmic exit. The nitrilase domain is located on the periplasmic side of the membrane, with its catalytic cavity connected to the periplasmic exit of the TM domain. An amphipathic lid loop from the nitrilase domain interacts with the periplasmic lipid leaflet, forming an interfacial entrance from the lipid bilayer to the catalytic centre for both the lipid donor and acceptor substrates.