Intrinsic Dynamics of a Human Gene Reveal the Basis of Expression Heterogeneity.

Transcriptional regulation in metazoans occurs through long-range genomic contacts between enhancers and promoters, and most genes are transcribed in episodic "bursts" of RNA synthesis. To understand the relationship between these two phenomena and the dynamic regulation of genes in response to upstream signals, we describe the use of live-cell RNA imaging coupled with Hi-C measurements and dissect the endogenous regulation of the estrogen-responsive TFF1 gene. Although TFF1 is highly induced, we observe short active periods and variable inactive periods ranging from minutes to days. The heterogeneity in inactive times gives rise to the widely observed "noise" in human gene expression and explains the distribution of protein levels in human tissue. We derive a mathematical model of regulation that relates transcription, chromosome structure, and the cell's ability to sense changes in estrogen and predicts that hypervariability is largely dynamic and does not reflect a stable biological state.

Regulation of T helper cell differentiation by the interplay between histone modification and chromatin interaction.

The development and function of the immune system are controlled by temporospatial gene expression programs, which are regulated by cis-regulatory elements, chromatin structure, and trans-acting factors. In this study, we cataloged the dynamic histone modifications and chromatin interactions at regulatory regions during T helper (Th) cell differentiation. Our data revealed that the H3K4me1 landscape established by MLL4 in naive CD4+ T cells is critical for restructuring the regulatory interaction network and orchestrating gene expression during the early phase of Th differentiation. GATA3 plays a crucial role in further configuring H3K4me1 modification and the chromatin interaction network during Th2 differentiation. Furthermore, we demonstrated that HSS3-anchored chromatin loops function to restrict the activity of the Th2 locus control region (LCR), thus coordinating the expression of Th2 cytokines. Our results provide insights into the mechanisms of how the interplay between histone modifications, chromatin looping, and trans-acting factors contributes to the differentiation of Th cells.

Restraint of IFN-γ expression through a distal silencer CNS-28 for tissue homeostasis.

Interferon-γ (IFN-γ) is a key cytokine in response to viral or intracellular bacterial infection in mammals. While a number of enhancers are described to promote IFN-γ responses, to the best of our knowledge, no silencers for the Ifng gene have been identified. By examining H3K4me1 histone modification in naive CD4+ T cells within Ifng locus, we identified a silencer (CNS-28) that restrains Ifng expression. Mechanistically, CNS-28 maintains Ifng silence by diminishing enhancer-promoter interactions within Ifng locus in a GATA3-dependent but T-bet-independent manner. Functionally, CNS-28 restrains Ifng transcription in NK cells, CD4+ cells, and CD8+ T cells during both innate and adaptive immune responses. Moreover, CNS-28 deficiency resulted in repressed type 2 responses due to elevated IFN-γ expression, shifting Th1 and Th2 paradigm. Thus, CNS-28 activity ensures immune cell quiescence by cooperating with other regulatory cis elements within the Ifng gene locus to minimize autoimmunity.

The transcription factor TCF-1 enforces commitment to the innate lymphoid cell lineage.

Innate lymphoid cells (ILCs) play important functions in immunity and tissue homeostasis, but their development is poorly understood. Through the use of single-cell approaches, we examined the transcriptional and functional heterogeneity of ILC progenitors, and studied the precursor-product relationships that link the subsets identified. This analysis identified two successive stages of ILC development within T cell factor 1-positive (TCF-1+) early innate lymphoid progenitors (EILPs), which we named 'specified EILPs' and 'committed EILPs'. Specified EILPs generated dendritic cells, whereas this potential was greatly decreased in committed EILPs. TCF-1 was dispensable for the generation of specified EILPs, but required for the generation of committed EILPs. TCF-1 used a pre-existing regulatory landscape established in upstream lymphoid precursors to bind chromatin in EILPs. Our results provide insight into the mechanisms by which TCF-1 promotes developmental progression of ILC precursors, while constraining their dendritic cell lineage potential and enforcing commitment to ILC fate.

Transcription factors TCF-1 and GATA3 are key factors for the epigenetic priming of early innate lymphoid progenitors toward distinct cell fates.

The differentiation of innate lymphoid cells (ILCs) from hematopoietic stem cells needs to go through several multipotent progenitor stages. However, it remains unclear whether the fates of multipotent progenitors are predefined by epigenetic states. Here, we report the identification of distinct accessible chromatin regions in all lymphoid progenitors (ALPs), EILPs, and ILC precursors (ILCPs). Single-cell MNase-seq analyses revealed that EILPs contained distinct subpopulations epigenetically primed toward either dendritic cell lineages or ILC lineages. We found that TCF-1 and GATA3 co-bound to the lineage-defining sites for ILCs (LDS-Is), whereas PU.1 binding was enriched in the LDSs for alternative dendritic cells (LDS-As). TCF-1 and GATA3 were indispensable for the epigenetic priming of LDSs at the EILP stage. Our results suggest that the multipotency of progenitor cells is defined by the existence of a heterogeneous population of cells epigenetically primed for distinct downstream lineages, which are regulated by key transcription factors.

Molecular organization of the early stages of nucleosome phase separation visualized by cryo-electron tomography.

It has been proposed that the intrinsic property of nucleosome arrays to undergo liquid-liquid phase separation (LLPS) in vitro is responsible for chromatin domain organization in vivo. However, understanding nucleosomal LLPS has been hindered by the challenge to characterize the structure of the resulting heterogeneous condensates. We used cryo-electron tomography and deep-learning-based 3D reconstruction/segmentation to determine the molecular organization of condensates at various stages of LLPS. We show that nucleosomal LLPS involves a two-step process: a spinodal decomposition process yielding irregular condensates, followed by their unfavorable conversion into more compact, spherical nuclei that grow into larger spherical aggregates through accretion of spinodal materials or by fusion with other spherical condensates. Histone H1 catalyzes more than 10-fold the spinodal-to-spherical conversion. We propose that this transition involves exposure of nucleosome hydrophobic surfaces causing modified inter-nucleosome interactions. These results suggest a physical mechanism by which chromatin may transition from interphase to metaphase structures.

Control of cell identity genes occurs in insulated neighborhoods in mammalian chromosomes.

The pluripotent state of embryonic stem cells (ESCs) is produced by active transcription of genes that control cell identity and repression of genes encoding lineage-specifying developmental regulators. Here, we use ESC cohesin ChIA-PET data to identify the local chromosomal structures at both active and repressed genes across the genome. The results produce a map of enhancer-promoter interactions and reveal that super-enhancer-driven genes generally occur within chromosome structures that are formed by the looping of two interacting CTCF sites co-occupied by cohesin. These looped structures form insulated neighborhoods whose integrity is important for proper expression of local genes. We also find that repressed genes encoding lineage-specifying developmental regulators occur within insulated neighborhoods. These results provide insights into the relationship between transcriptional control of cell identity genes and control of local chromosome structure.

Subgenome phasing for complex allopolyploidy: case-based benchmarking and recommendations.

Accurate subgenome phasing is crucial for understanding the origin, evolution and adaptive potential of polyploid genomes. SubPhaser and WGDI software are two common methodologies for subgenome phasing in allopolyploids, particularly in scenarios lacking known diploid progenitors. Triggered by a recent debate over the subgenomic origins of the cultivated octoploid strawberry, we examined four well-documented complex allopolyploidy cases as benchmarks, to evaluate and compare the accuracy of the two software. Our analysis demonstrates that the subgenomic structure phased by both software is in line with prior research, effectively tracing complex allopolyploid evolutionary trajectories despite the limitations of each software. Furthermore, using these validated methodologies, we revisited the controversial issue regarding the progenitors of the octoploid strawberry. The results of both methodologies reaffirm Fragaria vesca and Fragaria iinumae as progenitors of the octoploid strawberry. Finally, we propose recommendations for enhancing the accuracy of subgenome phasing in future studies, recognizing the potential of integrated tools for advanced complex allopolyploidy research and offering a new roadmap for robust subgenome-based phylogenetic analysis.

High-quality genome assembly enables prediction of allele-specific gene expression in hybrid poplar.

Poplar (Populus) is a well-established model system for tree genomics and molecular breeding, and hybrid poplar is widely used in forest plantations. However, distinguishing its diploid homologous chromosomes is difficult, complicating advanced functional studies on specific alleles. In this study, we applied a trio-binning design and PacBio high-fidelity long-read sequencing to obtain haplotype-phased telomere-to-telomere genome assemblies for the 2 parents of the well-studied F1 hybrid "84K" (Populus alba × Populus tremula var. glandulosa). Almost all chromosomes, including the telomeres and centromeres, were completely assembled for each haplotype subgenome apart from 2 small gaps on one chromosome. By incorporating information from these haplotype assemblies and extensive RNA-seq data, we analyzed gene expression patterns between the 2 subgenomes and alleles. Transcription bias at the subgenome level was not uncovered, but extensive-expression differences were detected between alleles. We developed machine-learning (ML) models to predict allele-specific expression (ASE) with high accuracy and identified underlying genome features most highly influencing ASE. One of our models with 15 predictor variables achieved 77% accuracy on the training set and 74% accuracy on the testing set. ML models identified gene body CHG methylation, sequence divergence, and transposon occupancy both upstream and downstream of alleles as important factors for ASE. Our haplotype-phased genome assemblies and ML strategy highlight an avenue for functional studies in Populus and provide additional tools for studying ASE and heterosis in hybrids.

CTCF-Mediated Enhancer-Promoter Interaction Is a Critical Regulator of Cell-to-Cell Variation of Gene Expression.

Recent studies indicate that even a homogeneous population of cells display heterogeneity in gene expression and response to environmental stimuli. Although promoter structure critically influences the cell-to-cell variation of gene expression in bacteria and lower eukaryotes, it remains unclear what controls the gene expression noise in mammals. Here we report that CTCF decreases cell-to-cell variation of expression by stabilizing enhancer-promoter interaction. We show that CTCF binding sites are interwoven with enhancers within topologically associated domains (TADs) and a positive correlation is found between CTCF binding and the activity of the associated enhancers. Deletion of CTCF sites compromises enhancer-promoter interactions. Using single-cell flow cytometry and single-molecule RNA-FISH assays, we demonstrate that knocking down of CTCF or deletion of a CTCF binding site results in increased cell-to-cell variation of gene expression, indicating that long-range promoter-enhancer interaction mediated by CTCF plays important roles in controlling the cell-to-cell variation of gene expression in mammalian cells.

Designer molecules of the synaptic organizer MDGA1 reveal 3D conformational control of biological function.

MDGAs (MAM domain-containing glycosylphosphatidylinositol anchors) are synaptic cell surface molecules that regulate the formation of trans-synaptic bridges between neurexins (NRXNs) and neuroligins (NLGNs), which promote synaptic development. Mutations in MDGAs are implicated in various neuropsychiatric diseases. MDGAs bind NLGNs in cis on the postsynaptic membrane and physically block NLGNs from binding to NRXNs. In crystal structures, the six immunoglobulin (Ig) and single fibronectin III domains of MDGA1 reveal a striking compact, triangular shape, both alone and in complex with NLGNs. Whether this unusual domain arrangement is required for biological function or other arrangements occur with different functional outcomes is unknown. Here, we show that WT MDGA1 can adopt both compact and extended 3D conformations that bind NLGN2. Designer mutants targeting strategic molecular elbows in MDGA1 alter the distribution of 3D conformations while leaving the binding affinity between soluble ectodomains of MDGA1 and NLGN2 intact. In contrast, in a cellular context, these mutants result in unique combinations of functional consequences, including altered binding to NLGN2, decreased capacity to conceal NLGN2 from NRXN1ß, and/or suppressed NLGN2-mediated inhibitory presynaptic differentiation, despite the mutations being located far from the MDGA1-NLGN2 interaction site. Thus, the 3D conformation of the entire MDGA1 ectodomain appears critical for its function, and its NLGN-binding site on Ig1-Ig2 is not independent of the rest of the molecule. As a result, global 3D conformational changes to the MDGA1 ectodomain via strategic elbows may form a molecular mechanism to regulate MDGA1 action within the synaptic cleft.

circUBE3C modulates myoblast development by binding to miR-191 and upregulating the expression of p27.

Noncoding RNAs, including miRNAs (microRNAs) and circRNAs (circular RNA), are crucial regulators of myoblast proliferation and differentiation during muscle development. However, the specific roles and molecular mechanisms of circRNAs in muscle development remain poorly understood. Based on the existing circRNA-miRNA-mRNA network, our study focuses on circUBE3C, exploring its differential expression in fetal and adult muscle tissue of the cattle and investigating its impact on myoblast proliferation, apoptosis, and differentiation. The functional analysis of overexpression plasmids and siRNAs (small interfering RNAs) targeting circUBE3C was comprehensively evaluated by employing an array of advanced assays, encompassing CCK-8 (cell counting kit-8), EdU (5-ethynyl-20-deoxyuridine), flow cytometry, western blot analysis, and RT-qPCR. In vivo investigations indicated that overexpression of circUBE3C impedes the process of skeletal muscle regeneration. Mechanistically, we demonstrated that circUBE3C interacts with miR-191 and alleviates the suppression of p27 through cytoplasmic separation, bioinformatics prediction, dual-luciferase reporter assay, and RIP (RNA immunoprecipitation). Our findings indicate that the novel circRNA circUBE3C competitively binds to miR-191, thereby inhibiting proliferation and promoting apoptosis in bovine primary myoblasts and unveiling a regulatory pathway in bovine skeletal muscle development. These findings expand our understanding of circRNA functions in mammals and provide a basis for further exploration of their role in myogenesis and muscle diseases.

Gap-free X and Y chromosome assemblies of Salix arbutifolia reveal an evolutionary change from male to female heterogamety in willows, without a change in the position of the sex-determining locus.

In the Vetrix clade of Salix, a genus of woody flowering plants, sex determination involves chromosome 15, but an XY system has changed to a ZW system. We studied the detailed genetic changes involved. We used genome sequencing, with chromosome conformation capture (Hi-C) and PacBio HiFi reads to assemble chromosome level gap-free X and Y of Salix arbutifolia, and distinguished the haplotypes in the 15X- and 15Y-linked regions, to study the evolutionary history of the sex-linked regions (SLRs). Our sequencing revealed heteromorphism of the X and Y haplotypes of the SLR, with the X-linked region being considerably larger than the corresponding Y region, mainly due to accumulated repetitive sequences and gene duplications. The phylogenies of single-copy orthogroups within the SLRs indicate that S. arbutifolia and Salix purpurea share an ancestral SLR within a repeat-rich region near the chromosome 15 centromere. During the change in heterogamety, the X-linked region changed to a W-linked one, while the Z was derived from the Y.

Fibronectin-Targeting Dual-Modal MR/NIRF Imaging Contrast Agents for Diagnosis of Gastric Cancer and Peritoneal Metastasis.

The prevalence and fatality rates of gastric cancer (GC) remain elevated, with advanced stages presenting a grim prognosis. Noninvasive diagnosis of GC cancer often proves challenging until the disease has progressed to an advanced stage or metastasized. Initially, the level of fibronectin (FN) in cancer-associated fibroblasts (CAFs) of GC was at least 3.7 times higher than that in normal fibroblasts. Herein, two FN-targeting magnetic resonance/near-infrared fluorescence (MR/NIRF) imaging contrast agents were developed to detect GC and peritoneal metastasis noninvasively. The probes CREKA-Cy7-(Gd-DOTA) and CREKA-Cy7-(Gd-DOTA)3 demonstrated significant FN-targeting capability (with dissociation constants of 1.0 and 2.1 mM) and effective MR imaging performance (with proton relaxivity values of 9.66 and 27.44 mM-1 s-1 at 9.4 T, 37 °C). In vivo imaging revealed a high signal-to-noise ratio and successful visualization of GC metastasis using NIRF imaging as well as successful tumor detection in MR imaging. Therefore, this study highlights the potential of FN-targeting probes for GC diagnosis and aids in the advancement of new diagnostic strategies for the clinical detection of GC.

cLoops2: a full-stack comprehensive analytical tool for chromatin interactions.

Investigating chromatin interactions between regulatory regions such as enhancer and promoter elements is vital for understanding the regulation of gene expression. Compared to Hi-C and its variants, the emerging 3D mapping technologies focusing on enriched signals, such as TrAC-looping, reduce the sequencing cost and provide higher interaction resolution for cis-regulatory elements. A robust pipeline is needed for the comprehensive interpretation of these data, especially for loop-centric analysis. Therefore, we have developed a new versatile tool named cLoops2 for the full-stack analysis of these 3D chromatin interaction data. cLoops2 consists of core modules for peak-calling, loop-calling, differentially enriched loops calling and loops annotation. It also contains multiple modules for interaction resolution estimation, data similarity estimation, features quantification, feature aggregation analysis, and visualization. cLoops2 with documentation and example data are open source and freely available at GitHub: https://github.com/KejiZhaoLab/cLoops2.

Mortality and morbidity following initiation of anticoagulant or antiplatelet treatment for blunt cerebrovascular injury.

OBJECTIVE: Cerebrovascular accidents (CVA) are potential sequelae of blunt cerebrovascular injuries (BCVI). To minimize their risk, medical therapy is used commonly. It is unclear if anticoagulant or antiplatelet medications are superior for decreasing CVA risk. It is also unclear as to which confer fewer undesirable side effects specifically in patients with BCVI. The aim of this study was to compare outcomes between nonsurgical patients with BCVI with hospital admission records who were treated with anticoagulant medications and those who were treated with antiplatelet medications. METHODS: We performed a 5-year (2016-2020) analysis of the Nationwide Readmission Database. We identified all adult trauma patients who were diagnosed with BCVI and treated with either anticoagulant or antiplatelet agents. Patients who were diagnosed with index admission CVA, intracranial injury, hypercoagulable states, atrial fibrillation, and or moderate to severe liver disease were excluded. Those who underwent vascular procedures (open and/or endovascular approaches) and or neurosurgical treatment were also excluded. Propensity score matching (1:2 ratio) was performed to control for demographics, injury parameters, and comorbidities. Index admission and 6-month readmission outcomes were examined. RESULTS: We identified 2133 patients with BCVI who were treated with medical therapy; 1091 patients remained after applying the exclusion criteria. A matched cohort of 461 patients (anticoagulant, 159; antiplatelet, 302) was obtained. The median patient age was 72 years (interquartile range [IQR], 56-82 years), 46.2% of patients were female, falls were the mechanism of injury in 57.2% of cases, and the median New Injury Severity Scale score was 21 (IQR, 9-34). Index outcomes with respect to (1) anticoagulant treatments followed by (2) antiplatelet treatments and (3) P values are as follows: mortality (1.3%, 2.6%, 0.51), median length of stay (6 days, 5 days; P < .001), and median total charge (109,736 USD, 80,280 USD, 0.12). The 6-month readmission outcomes are as follows: readmission (25.8%, 16.2%, <0.05), mortality (4.4%, 4.6%, 0.91), ischemic CVA (4.9%, 4.1%, P = not significant [NS]), gastrointestinal hemorrhage (4.9%, 10.2%, 0.45), hemorrhagic CVA (0%, 0.41%, P = NS), and blood loss anemia (19.5%, 12.2%, P = NS). CONCLUSIONS: Anticoagulants are associated with a significantly increased readmission rate within 6 months. Neither medical therapy is superior to one another in the reduction of the following: index mortality, 6-month mortality, and 6-month readmission with CVA. Notably, antiplatelet agents seem to be associated with increased hemorrhagic CVA and gastrointestinal hemorrhage on readmission, although neither association is statistically significant. Still, these associations underscore the need for further prospective studies of large sample sizes to investigate the optimal medical therapy for nonsurgical patients with BCVI with hospital admission records.

Structure-based mechanism and inhibition of cholesteryl ester transfer protein.

PURPOSE OF REVIEW: Cholesteryl ester transfer proteins (CETP) regulate plasma cholesterol levels by transferring cholesteryl esters (CEs) among lipoproteins. Lipoprotein cholesterol levels correlate with the risk factors for atherosclerotic cardiovascular disease (ASCVD). This article reviews recent research on CETP structure, lipid transfer mechanism, and its inhibition. RECENT FINDINGS: Genetic deficiency in CETP is associated with a low plasma level of low-density lipoprotein cholesterol (LDL-C) and a profoundly elevated plasma level of high-density lipoprotein cholesterol (HDL-C), which correlates with a lower risk of atherosclerotic cardiovascular disease (ASCVD). However, a very high concentration of HDL-C also correlates with increased ASCVD mortality. Considering that the elevated CETP activity is a major determinant of the atherogenic dyslipidemia, i.e., pro-atherogenic reductions in HDL and LDL particle size, inhibition of CETP emerged as a promising pharmacological target during the past two decades. CETP inhibitors, including torcetrapib, dalcetrapib, evacetrapib, anacetrapib and obicetrapib, were designed and evaluated in phase III clinical trials for the treatment of ASCVD or dyslipidemia. Although these inhibitors increase in plasma HDL-C levels and/or reduce LDL-C levels, the poor efficacy against ASCVD ended interest in CETP as an anti-ASCVD target. Nevertheless, interest in CETP and the molecular mechanism by which it inhibits CE transfer among lipoproteins persisted. Insights into the structural-based CETP-lipoprotein interactions can unravel CETP inhibition machinery, which can hopefully guide the design of more effective CETP inhibitors that combat ASCVD. Individual-molecule 3D structures of CETP bound to lipoproteins provide a model for understanding the mechanism by which CETP mediates lipid transfer and which in turn, guide the rational design of new anti-ASCVD therapeutics.

Tirofiban for Acute Ischemic Stroke Patients Receiving Intravenous Thrombolysis: A Systematic Review and Meta-Analysis.

INTRODUCTION: Tirofiban has been used as a rescue when thrombectomy is not successful in endovascular therapy (EVT) for acute ischemic stroke (AIS), but the use of tirofiban after intravenous thrombolysis (IVT) is controversial. The purpose of this meta-analysis was to evaluate the safety and efficacy of tirofiban combined with IVT in AIS compared with not receiving tirofiban. METHODS: The PubMed and Embase databases were searched for all relevant studies published up to August 31, 2021. The safety endpoints included symptomatic intracranial hemorrhage (sICH), any intracranial hemorrhage (ICH), and mortality. The efficacy endpoint was the modified Rankin Scale (mRS) score at the 3-month follow-up. RESULTS: Seven articles (1,036 patients) were included. Of these, 444 patients received tirofiban, and 592 patients did not. Meta-analysis showed that tirofiban did not increase the risk of sICH (OR 0.98; 95% CI 0.50-1.93; p = 0.96), any ICH (OR 0.94; 95% CI 0.63-1.39; p = 0.75) or mortality (OR 0.67; 95% CI 0.39-1.15; p = 0.15) and tended to be associated with a favorable functional outcome (OR 1.33; 95% CI 0.99-1.78; p = 0.06) in patients with AIS. Subgroup analysis showed that bridging therapy combined with tirofiban could reduce mortality (OR 0.47; 95% CI 0.23-0.98; p = 0.04). Tirofiban significantly improved the favorable functional outcome in patients with IVT only (non-EVT) (OR 1.98; 95% CI 1.30-3.02; p = 0.002). CONCLUSION: Intravenous tirofiban could be safe for patients with AIS undergoing IVT, regardless of receiving EVT. Intravenous tirofiban may reduce mortality rates for patients undergoing bridging therapy. It also could increase the likelihood of a favorable functional outcome, especially for patients receiving IVT only.

Risk factors for readmission after open abdominal aortic aneurysms repair and its outcome in chronic kidney disease patients.

OBJECTIVE: Readmission after vascular procedures is a burden to hospitals and the Medicare system. Therefore, identifying risk factors leading to readmission is vital. We examined the frequency of and risk factors for 30-day readmission after open aneurysm repair (OAR) and explored post-operative outcomes with special attention for those with preexisting chronic kidney disease (CKD). METHODS: Patients who underwent OAR were identified in the National Readmission Database (2016-2018). Demographic information and comorbidities were collected. Patients readmitted within 30 days after their index hospitalization were identified and compared to patients without readmission records. RESULTS: A total of 5090 patients underwent OAR during the study timeframe with 488 patients (9.6%) were readmitted within 30 days. Females were more readmitted than males (F = 11.1% vs M = 9.0%, P < 0.001). Readmitted patients had more comorbidities (median ECI 12, P < 0.05), were on Medicare (73.7%, P < 0.001), had higher surgery admission cost ($146,844, P < 0.001), longer length of stay (8 days, P < 0.001), and were discharged to a lower level care facility (62.7%, P < 0.001). Comorbidities that predisposed patients for readmission include: peripheral arterial disease (OR 2.15, P < 0.01), asthma (OR 1.87, P < 0.01), chronic heart failure (OR 1.74, P < 0.05). On readmission visit, acute renal failure (23.8%) was the most common diagnosis, while intestinal surgery (13.7%) was the most common procedure. Patients with CKD (n = 968, 18.9% of total population) had double the mortality rate compared to non-CKD patients on surgery admission (10.4%, P < 0.001) and readmission (10.1%, P < 0.001). CONCLUSION: Certain factors were noted to increase readmission rate, special attention need to be paid when dealing with such group of patients requiring OAR. Vascular surgeons should meticulously weigh benefits and risks when considering OAR in patients with CKD who are not a candidate for endovascular repair, and optimize their kidney function before considering such approach.

The relationship between lower extremity amputation and body mass index.

OBJECTIVES: Non-traumatic lower extremity amputation (LEA) is associated with significant morbidity and mortality. Diabetes mellitus (DM) and peripheral vascular disease (PVD) are associated with increased risk for LEA. As such, DM and PVD account for 54% of all LEA's, performed in the United States annually. As obesity is highly associated with both DM and PVD, our study sought to explore the relationship between LEA and obesity defined by BMI. METHODS: Using the National Inpatient Sample (NIS) database, a retrospective review of patients who underwent non-traumatic LEA (LEA) between 2008 and 2014 was performed. The International Classification of Diseases 9th edition (ICD-9) codes were utilized to determine the diagnoses, comorbidities, and procedures. Patient BMIs were classified as follows: Non-obese [BMI <30], Obesity class I [BMI 30-34.9], Obesity class II [BMI 35-39.9], and Obesity class III [BMI ≥40]. Predictors for LEA were compared between groups using chi-square test and binary logistic regression to identify possible underlying factors associated with LEA. We also conducted a multivariate analysis to measure the effect of multiple variables on LEA. RESULTS: We identified 16,259 patients with non-traumatic LEA and a mean age of 59.9 years. Rate of amputation in females was lower than males at 0.35% vs 0.87% respectively (p < 0.001). Of patients that underwent amputation there was a V-shape trend based on BMI, with 30.4% in non-obese patients, 18.2% in obesity class I, 17.3% in obesity class II, and 34.1% in obesity class III. The incidence of diabetes increased with obesity class, while the incidence of PVD decreased. Interestingly, of those with DM there was an inverse relationship between amputation rate and BMI class, with LEA rates in non-obese versus obesity class III patients were 1.63% vs 0.98% respectively (p < 0.001). Similarly, patients who had both diabetes and PVD showed a downward trend in LEA rate as obesity class increased; non-obese patients had a LEA rate of 8.01%, while obesity class III had 4.65% (p < 0.001). Patients in higher income bracket have lower odds of LEA (OR 0.77, p < 0.001) compared to the lowest income patients. Also, patients with comorbidities such as PVD (OR 10.78), diabetes (OR 5.02), renal failure (OR 1.41), and hypertension (OR 1.36) had higher odds to get an LEA (p < 0.001). Individuals with obesity class III are almost at half the odds (OR 0.52) to get an LEA compared to non-obese (p < 0.001). CONCLUSIONS: Higher BMI and female gender are protective factors against lower extremity amputation. Factors that predisposing to LEA include lower household income and certain comorbidities such as PVD, diabetes, renal failure, and hypertension. These findings warrant further research to identify patients at high risk for LEA and help develop management guidelines for targeted populations.