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How to Fix Spotlight Search Issues on MacOS Sequoia

A fair number of Mac users have discovered that Spotlight Search is not working well in MacOS Sequoia, either missing files, apps, and sometimes not working at all to find any local file. For some users the issues with Spotlight happens right after they update to MacOS Seqouia, and for others it may happen later ... Read More




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How Animal Research Can Inspire Elementary Students’ Writing

Teachers can assess young students’ literacy skills and knowledge by encouraging them to produce books based on animal facts.




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Nuclear-powered aircraft carriers would give China's growing navy new reach, and researchers say it's working on the reactor to power one

A nuclear-powered aircraft carrier, like American carriers, would be a major jump for China, giving its navy a global reach.




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The biggest risk to stocks after Trump's victory is China's reaction to a trade war, research firm says

If Trump's proposed 60% tariff against China is enacted and the country responds aggressively, it could pressure some of America's largest companies.





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Beyond Labels and Agendas: Research Teachers need to Know about Phonics and Phonological Awareness

This article describes the current findings on phonics and phonological awareness instruction. It uses a question & answer format to explore 10 common questions that teachers ask about teaching phonics and phonemic awareness. Here are a few key questions addressed in the article: What are phonics and phonemic awareness? Should phonemic awareness be paired with print and taught together? Should phonological awareness be coordinated with phonics instruction? What is the best sequence for teaching phonics?




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AI labs – a club for #AI research and a chance to gain hands-on experience with AI

  We have been working on this idea over the summer and have now launched the next stage of the AI labs in London Here are some more details. Think of AI labs – as a club for AI research AI labs addresses three problems a)  Today, even if you are working on Machine Learning [...]





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News24 Business | Internet Archive, Wayback Machine hit by 'catastrophic' cyberattack, data breach

The Internet Archive, an online repository of web pages, was offline Thursday after its founder confirmed a major cyberattack that exposed the data of millions of users and left the site defaced.




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Software Architecture in an AI World

Like almost any question about AI, “How does AI impact software architecture?” has two sides to it: how AI changes the practice of software architecture and how AI changes the things we architect. These questions are coupled; one can’t really be discussed without the other. But to jump to the conclusion, we can say that […]




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March Madness in High Def

Ryan Lawler notes in his Contentinople blog that CBS's high definition stream of the NCAA men's basketball tournament has been a great success.

CBS Sports reported that traffic to its NCAA March Madness on Demand site on the first day of the tourney increased 56 percent year-over-year, to 2.7 million unique users yesterday from 1.75 million uniques a year ago.


If there is a conclusion to be drawn, I do not think it is that internet video can or should compete with television. In this case, I believe the draw is a combination of the fact that watching television on Thursday afternoon is not an option for people with a day job, and that there are many games going on simultaneously and CBS television does not always cut to the game that the individual user wants to see.

I think the focus should be on the success of delivering a high quality video experience to a large audience, many of whom were at work. This is just another step in the direction of enterprise video becoming an essential element of the workplace experience.




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What’s SearchGPT Really About? Moving Past the Training Data Dilemma.

This morning we awoke to one story dominating the tech news landscape: OpenAI is “expanding into search,” launching SearchGPT, a prototype that appears to be a direct competitor to Google (and Bing and Perplexity, not that they really matter). But despite the voluminous coverage, my initial take is that once the hype cycle passes – … Continue reading "What’s SearchGPT Really About? Moving Past the Training Data Dilemma."




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From the Archive: Tech Must Get Over Its Superman Complex, Or We’re All Screwed

Five years ago I was posting a lot to a publication called NewCo Shift, which is now offline. I got ahold of the archives, and found this review, which hasn’t lost any of its relevance – in fact, it kind of reads like it was written last week.  Everyone in tech loves Yuval Noah Harari. … Continue reading "From the Archive: Tech Must Get Over Its Superman Complex, Or We’re All Screwed"




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Trump to Pick Senator Marco Rubio for Crucial Cabinet Position: Report

President-elect Donald Trump is expected to nominate Florida Sen. Marco Rubio as his secretary of state, reports late Monday indicate. According to The Wall Street Journal, while the nomination isn’t […]

The post Trump to Pick Senator Marco Rubio for Crucial Cabinet Position: Report appeared first on The Western Journal.




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Sport | Marco Jansen hopes for better showing against spin as T20 series takes Highveld turn

Proteas all-rounder Marco Jansen, while acknowledging that spin has been a challenge for them in the ongoing T20 series against India, reckons things could be a bit different for Wednesday's third T20 in Centurion.




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Russia and China in Antarctica: Implications for the Five Eyes

Russia and China in Antarctica: Implications for the Five Eyes 15 December 2022 — 11:00AM TO 12:00PM Anonymous (not verified) 2 December 2022 Online

This event explores Russia’s and China’s postions on the Antarctic and offers a critical assessment of their actions in the region.

Ever since the 1959 Antarctic Treaty System (ATS), signed at the height of Cold War, Antarctica has remained a demilitarized continent.

Today, even though the ATS is not in immediate danger of collapse, Antarctica and the Southern Ocean are no longer insulated from wider geopolitical tension, with China and Russia posing challenges to regional governance. 
 
This event also discusses key recommendations for the Five Eyes regarding Russian and Chinese current and future efforts at undermining the ATS and Antarctic governance. 

The discussion is informed by Mathieu Boulègue’s paper ‘Russia and China in Antarctica and the Southern Ocean: Implications for the Five Eyes’ published by the Sea Power Centre of the Royal Australian Navy.




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Discordant Protein and mRNA Expression in Lung Adenocarcinomas

Guoan Chen
Apr 1, 2002; 1:304-313
Research




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GPS 2.0, a Tool to Predict Kinase-specific Phosphorylation Sites in Hierarchy

Yu Xue
Sep 1, 2008; 7:1598-1608
Research




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The Paragon Algorithm, a Next Generation Search Engine That Uses Sequence Temperature Values and Feature Probabilities to Identify Peptides from Tandem Mass Spectra

Ignat V. Shilov
Sep 1, 2007; 6:1638-1655
Technology




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In conversation with James Manyika, Senior Vice President of Research, Technology and Society at Google

In conversation with James Manyika, Senior Vice President of Research, Technology and Society at Google 12 December 2024 — 11:15AM TO 12:45PM Anonymous (not verified) Chatham House and Online

A conversation on AI’s global, societal and economic impacts.

2024 has been a landmark year for Artificial Intelligence (AI) development, deployment and use, with significant progress in AI-driven science, governance and cooperation. Looking ahead, AI continues to demonstrate economic promise and potential to expand on scientific breakthroughs in areas such as climate and health. This wave of innovation is occurring against a backdrop of geopolitical uncertainty and not all countries are fully able to participate. Heading into 2025, there are urgent questions about how best to maximise shared opportunities when it comes to AI and to advance global cooperation.

James Manyika, Senior Vice President of Research, Technology & Society at Google, will unpack what 2025 will bring for AI in science, economics, global governance and international cooperation. 

Key questions include:

  • What will be AI’s global societal and economic impact in 2025 and beyond? 
  • What are the ways AI could help increase economic growth and economy-wide productivity? What factors must be in place for this to happen?
  • How best can we maximise shared opportunities and advance global cooperation when it comes to AI? Where can public-private partnerships unlock scientific breakthroughs for societal progress, combatting shared global challenges such as climate change and global health issues?  
  • What are the principles of safe, responsible AI, and how should companies remain responsive to their evolution and integrate them into technology design and implementation? 
  • What is the current – and ideal – role of technology companies in emerging mechanisms for global cooperation and national governance on AI?

This event is being held in partnership with Google.

You will receive notice by 13:00 on Wednesday 11 December if you have been successful in securing an in-person place.

The institute occupies a position of respect and trust, and is committed to fostering inclusive dialogue at all events. Event attendees are expected to uphold this by adhering to our code of conduct.




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Brexit: In Search of A Solution - The Common Market 2.0 Option




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Our Shared Humanity: Welcome and Panel One - The Arc of Intervention




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Undercurrents: Episode 43 - The UK Election, and Svyatoslav Vakarchuk on the Future of Ukraine




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Design in an Age of Crisis: The Search for Radical Solutions




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Chatham House awarded major centenary grant to establish Stavros Niarchos Foundation Wing

Chatham House awarded major centenary grant to establish Stavros Niarchos Foundation Wing News Release sysadmin 16 April 2019

Chatham House has been awarded a transformational £10m grant ahead of its upcoming 2020 centenary.




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Chatham House appoints Tim Benton as Research Director for Energy, Environment and Resources

Chatham House appoints Tim Benton as Research Director for Energy, Environment and Resources News Release sysadmin 30 May 2019

Chatham House is pleased to announce that Professor Tim Benton has been appointed as research director of the Energy, Environment and Resources Department.





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An abstract approach to Marcinkiewicz-Zygmund inequalities for approximation and quadrature in modulation spaces

Martin Ehler and Karlheinz Gröchenig
Math. Comp. 93 (), 2885-2919.
Abstract, references and article information




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Using Math to Support Cancer Research

Stacey Finley from University of Southern California discusses how mathematical models support the research of cancer biology. Cancer research is a crucial job, but a difficult one. Tumors growing inside the human body are affected by all kinds of factors. These conditions are difficult (if not impossible) to recreate in the lab, and using real patients as subjects can be painful and invasive. Mathematical models give cancer researchers the ability to run experiments virtually, testing the effects of any number of factors on tumor growth and other processes — all with far less money and time than an experiment on human subjects or in the lab would use.





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46 Receive AMS-Simons Research Enhancement Grants for PUI Faculty

Forty-six mathematical scientists have been named recipients of AMS-Simons Research Enhancement Grants for Primarily Undergraduate Institution (PUI) Faculty. Each awardee will receive $3,000 per year for three years. 

The grants foster and support research collaboration by full-time mid-career mathematicians at US institutions that do not offer a mathematics doctoral degree.

This year’s grant recipients hail from 42 institutions across 21 US states. The grants will support their research in several different areas, from number theory to applied mathematics.

This is the grant program’s second cohort, said Sarah Bryant, associate vice president of programs. “Over the first two years, we’ve worked with faculty from 75 different institutions, including 19 minority-serving institutions, which shows just how much this program is expanding and making an impact,” Bryant said. She noted that “in the first year, the grants supported 87 trips, helped produce 70 publications and preprints, and gave awardees the resources needed to collaborate and advance their work.”

The grant allows for any activities that will further the awardee’s research program. Expenses include but are not limited to conference participation, institute visits, collaboration travel (awardee or collaborator), computer equipment or software, family-care expenses, and teaching assistants.

Administration of the award by the grantee’s institution is required; annual discretionary funds for a grantee’s department and administrative funds for a grantee's institution will be available at the end of each grant year.

The grants are made possible through funding from the Simons Foundation and the American Mathematical Society (AMS), as well as Eve, Kirsten, Lenore, and Ada of the Menger family.

Applications for the next cohort are anticipated to open on MathPrograms.org on January 9, 2025. Visit the AMS website to view an informational PowerPoint or sign up to receive email updates about the program. Faculty who applied for but did not receive the 2023 or 2024 awards are encouraged to reapply if they are still eligible for the grant. 




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Apple to announce AI wall tablet as soon as March, Bloomberg News reports




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Molecular architecture and domain arrangement of the placental malaria protein VAR2CSA suggests a model for carbohydrate binding [Glycobiology and Extracellular Matrices]

VAR2CSA is the placental-malaria–specific member of the antigenically variant Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family. It is expressed on the surface of Plasmodium falciparum-infected host red blood cells and binds to specific chondroitin-4-sulfate chains of the placental proteoglycan receptor. The functional ∼310 kDa ectodomain of VAR2CSA is a multidomain protein that requires a minimum 12-mer chondroitin-4-sulfate molecule for specific, high affinity receptor binding. However, it is not known how the individual domains are organized and interact to create the receptor-binding surface, limiting efforts to exploit its potential as an effective vaccine or drug target. Using small angle X-ray scattering and single particle reconstruction from negative-stained electron micrographs of the ectodomain and multidomain constructs, we have determined the structural architecture of VAR2CSA. The relative locations of the domains creates two distinct pores that can each accommodate the 12-mer of chondroitin-4-sulfate, suggesting a model for receptor binding. This model has important implications for understanding cytoadherence of infected red blood cells and potentially provides a starting point for developing novel strategies to prevent and/or treat placental malaria.




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Polydisperse molecular architecture of connexin 26/30 heteromeric hemichannels revealed by atomic force microscopy imaging [Protein Structure and Folding]

Connexin (Cx) protein forms hemichannels and gap junctional channels, which play diverse and profound roles in human physiology and diseases. Gap junctions are arrays of intercellular channels formed by the docking of two hemichannels from adjacent cells. Each hexameric hemichannel contains the same or different Cx isoform. Although homomeric Cxs forms have been largely described functionally and structurally, the stoichiometry and arrangement of heteromeric Cx channels remain unknown. The latter, however, are widely expressed in human tissues and variation might have important implications on channel function. Investigating properties of heteromeric Cx channels is challenging considering the high number of potential subunit arrangements and stoichiometries, even when only combining two Cx isoforms. To tackle this problem, we engineered an HA tag onto Cx26 or Cx30 subunits and imaged hemichannels that were liganded by Fab-epitope antibody fragments via atomic force microscopy. For Cx26-HA/Cx30 or Cx30-HA/Cx26 heteromeric channels, the Fab-HA binding distribution was binomial with a maximum of three Fab-HA bound. Furthermore, imaged Cx26/Cx30-HA triple liganded by Fab-HA showed multiple arrangements that can be derived from the law of total probabilities. Atomic force microscopy imaging of ringlike structures of Cx26/Cx30-HA hemichannels confirmed these findings and also detected a polydisperse distribution of stoichiometries. Our results indicate a dominant subunit stoichiometry of 3Cx26:3Cx30 with the most abundant subunit arrangement of Cx26-Cx26-Cx30-Cx26-Cx30-Cx30. To our knowledge, this is the first time that the molecular architecture of heteromeric Cx channels has been revealed, thus providing the basis to explore the functional effect of these channels in biology.




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CD70-Targeted Immuno-PET/CT Imaging of Clear Cell Renal Cell Carcinoma: A Translational Study

Visual Abstract




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Proteomic analyses identify differentially expressed proteins and pathways between low-risk and high-risk subtypes of early-stage lung adenocarcinoma and their prognostic impacts

Juntuo Zhou
Nov 30, 2020; 0:RA120.002384v1-mcp.RA120.002384
Research




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PTM-Shepherd: analysis and summarization of post-translational and chemical modifications from open search results

Daniel J. Geiszler
Dec 1, 2020; 0:TIR120.002216v1-mcp.TIR120.002216
Technological Innovation and Resources




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Problem Notes for SAS®9 - 48028: Custom Time Frame-based data versions do not aggregate correctly when referenced in worksheets with standard hierarchy levels

In SAS Merchandise Financial Planning, custom time frame-based data versions do not aggregate correctly when referenced in worksheets with standard hierarchy levels. The data does not aggregate correctly from l




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WITHDRAWN: Structural and mechanistic studies of hydroperoxide conversions catalyzed by a CYP74 clan epoxy alcohol synthase from amphioxus (Branchiostoma floridae) [Research Articles]

This manuscript has been withdrawn by the Author.




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Dietary sphinganine is selectively assimilated by members of the mammalian gut microbiome [Research Articles]

Functions of the gut microbiome have a growing number of implications for host metabolic health, with diet being one of the most significant influences on microbiome composition. Compelling links between diet and the gut microbiome suggest key roles for various macronutrients, including lipids, yet how individual classes of dietary lipids interact with the microbiome remains largely unknown. Sphingolipids are bioactive components of most foods and are also produced by prominent gut microbes. This makes sphingolipids intriguing candidates for shaping diet–microbiome interactions. Here, we used a click chemistry–based approach to track the incorporation of bioorthogonal dietary omega-alkynyl sphinganine (sphinganine alkyne [SAA]) into the murine gut microbial community (Bioorthogonal labeling). We identified microbial and SAA-specific metabolic products through fluorescence-based sorting of SAA-containing microbes (Sort), 16S rRNA gene sequencing to identify the sphingolipid-interacting microbes (Seq), and comparative metabolomics to identify products of SAA assimilation by the microbiome (Spec). Together, this approach, termed Bioorthogonal labeling-Sort-Seq-Spec (BOSSS), revealed that SAA assimilation is nearly exclusively performed by gut Bacteroides, indicating that sphingolipid-producing bacteria play a major role in processing dietary sphinganine. Comparative metabolomics of cecal microbiota from SAA-treated mice revealed conversion of SAA to a suite of dihydroceramides, consistent with metabolic activities of Bacteroides and Bifidobacterium. Additionally, other sphingolipid-interacting microbes were identified with a focus on an uncharacterized ability of Bacteroides and Bifidobacterium to metabolize dietary sphingolipids. We conclude that BOSSS provides a platform to study the flux of virtually any alkyne-labeled metabolite in diet–microbiome interactions.




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Hepatic Deletion of Mboat7 (Lpiat1) Causes Activation of SREBP-1c and Fatty Liver [Research Articles]

Genetic variants that increase the risk of fatty liver disease (FLD) and cirrhosis have recently been identified in the proximity of membrane bound O-acyltransferase domain-containing 7 (MBOAT7).  To elucidate the link between these variants and FLD we characterized Mboat7 liver-specific knock-out mice (Mboat7-LSKO).  Chow-fed Mboat7-LSKO mice developed fatty livers and associated liver injury.  Lipidomic analysis of liver using mass spectrometry revealed a pronounced reduction in 20-carbon polyunsaturated fatty acid content in phosphatidylinositols (PIs), but not in other phospholipids. The change in fatty acid composition of PIs in these mice was associated with a marked increase in de novo lipogenesis due to activation of SREBP-1c, a transcription factor that coordinates the activation of genes encoding enzymes in the fatty acid biosynthesis pathway. Hepatic removal of both SREBP cleavage activating protein (Scap) and Mboat7 normalized hepatic triglycerides relative to Scap only hepatic knock-out showing increased SREBP-1c processing is required for Mboat7 induced steatosis.  This study reveals a clear relationship between PI fatty acid composition and regulation of hepatic fat synthesis and delineates the mechanism by which mutations in MBOAT7 cause hepatic steatosis.




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Lipid and Metabolic Syndrome Traits in Coronary Artery Disease: A Mendelian Randomization Study [Patient-Oriented and Epidemiological Research]

Mendelian randomization (MR) of lipid traits in coronary artery disease (CAD) has provided evidence for causal associations of low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) in CAD, but many lipid trait genetic variants have pleiotropic effects on other cardiovascular risk factors that may bias MR associations. The goal of this study was to evaluate pleiotropic effects of lipid trait genetic variants and to account for these effects in MR of lipid traits in CAD. We performed multivariable MR using inverse variance-weighted (IVW) and MR-Egger methods in large (n ≥ 300,000) GWAS datasets. We found that 30% of lipid trait genetic variants have effects on metabolic syndrome traits, including body mass index (BMI), type 2 diabetes (T2D), and systolic blood pressure (SBP). Nonetheless, in multivariable MR analysis, LDL-C, high-density lipoprotein cholesterol (HDL-C), TG, BMI, T2D, and SBP are independently associated with CAD, and each of these associations is robust to adjustment for directional pleiotropy. MR at loci linked to direct effects on HDL-C and TG suggests locus- and mechanism-specific causal effects of these factors on CAD.




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High-density lipoprotein-associated miRNA is increased following Roux-en-Y gastric bypass surgery for severe obesity [Research Articles]

Roux-en-Y gastric bypass (RYGB) is one of the most commonly performed weight-loss procedures, but how severe obesity and RYGB affects circulating HDL-associated microRNAs (miRNAs) remains unclear. Here, we aim to investigate how HDL-associated miRNAs are regulated in severe obesity and how weight loss after RYGB surgery affects HDL-miRNAs. Plasma HDL were isolated from patients with severe obesity (n=53) before, 6 and 12 months after RYGB by immunoprecipitation using goat anti-human apoA-I microbeads. HDL were also isolated from 18 healthy participants. miRNAs were extracted from isolated HDL and levels of miR-24, miR-126, miR-222 and miR-223 were determined by TaqMan miRNA assays. We found that HDL-associated miR-126, miR-222 and miR-223 levels, but not miR-24 levels, were significantly higher in patients with severe obesity when compared with healthy controls. There were significant increases in HDL-associated miR-24, miR-222 and miR-223 at 12 months after RYGB. Additionally, cholesterol efflux capacity and paraoxonase (PON1) activity were increased and intracellular adhesion molecule-1 (ICAM-1) levels decreased. The increases in HDL-associated miR-24 and miR-223 were positively correlated with increase in cholesterol efflux capacity (r=0.326, P=0.027 and r=0.349, P=0.017 respectively). An inverse correlation was observed between HDL-associated miR-223 and ICAM-1 at baseline. Together, these findings show that HDL-associated miRNAs are differentially regulated in healthy versus patients with severe obesity and are altered after RYGB. These findings provide insights into how miRNAs are regulated in obesity before and after weight reduction, and may lead to the development of novel treatment strategies for obesity and related metabolic disorders.




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Adiponectin forms a complex with atherogenic LDL and inhibits its downstream effects [Research Articles]

Adiponectin, an adipocyte-derived protein, has anti-atherogenic and anti-diabetic effects, but how it confers the anti-atherogenic effects is not well understood. To study the anti-atherogenic mechanisms of adiponectin, we examined whether it interacts with atherogenic low-density lipoprotein (LDL) to attenuate LDL’s atherogenicity. L5, the most electronegative subfraction of LDL, induces atherogenic responses similarly to copper-oxidized LDL (oxLDL). Unlike native LDL endocytosed via the LDL receptor, L5 and oxLDL are internalized by cells via the lectin-like oxidized LDL receptor-1 (LOX-1). Using enzyme-linked immunosorbent assays (ELISAs), we showed that adiponectin preferentially bound oxLDL but not native LDL. In Chinese hamster ovary (CHO) cells transfected with LOX-1 or LDL receptor, adiponectin selectively inhibited the uptake of oxLDL but not of native LDL, respectively. Furthermore, adiponectin suppressed the internalization of oxLDL in human coronary artery endothelial cells (HCAECs) and THP-1–derived macrophages. Western blot analysis of human plasma showed that adiponectin was abundant in L5 but not in L1, the least electronegative subfraction of LDL. Sandwich ELISAs with anti-adiponectin and anti–apolipoprotein B antibodies confirmed the binding of adiponectin to L5 and oxLDL. In LOX-1–expressing CHO cells, adiponectin inhibited cellular responses to oxLDL and L5, including nuclear factor-B activation and ERK phosphorylation. In HCAECs, adiponectin inhibited oxLDL-induced endothelin-1 secretion and ERK phosphorylation. Conversely, oxLDL suppressed the adiponectin-induced activation of adenosine monophosphate–activated protein kinase in COS-7 cells expressing adiponectin receptor AdipoR1. Our findings suggest that adiponectin binds and inactivates atherogenic LDL, providing novel insight into the anti-atherogenic mechanisms of adiponectin.




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Structure dynamics of ApoA-I amyloidogenic variants in small HDL increase their ability to mediate cholesterol efflux [Research Articles]

Apolipoprotein A-I (ApoA-I) of high-density lipoprotein (HDL) is essential for the transportation of cholesterol between peripheral tissues and the liver. However, specific mutations in Apolipoprotein A-I (ApoA-I) of high-density lipoprotein (HDL) are responsible for a late-onset systemic amyloidosis, the pathological accumulation of protein fibrils in tissues and organs. Carriers of these mutations do not exhibit increased cardiovascular disease risk despite displaying reduced levels of ApoA-I/ HDL-cholesterol. To explain this paradox, we show that the HDL particle profile of patients carrying either L75P or L174S ApoA-I amyloidogenic variants a higher relative abundance of the 8.4 nm vs 9.6 nm particles, and that serum from patients, as well as reconstituted 8.4 and 9.6 nm HDL particles (rHDL), possess increased capacity to catalyze cholesterol efflux from macrophages. Synchrotron radiation circular dichroism and hydrogen-deuterium exchange revealed that the variants in 8.4 nm rHDL have altered secondary structure composition and display a more flexible binding to lipids compared to their native counterpart. The reduced HDL-cholesterol levels of patients carrying ApoA-I amyloidogenic variants are thus balanced by higher proportion of small, dense HDL particles and better cholesterol efflux due to altered, region-specific protein structure dynamics.




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Insights on the kinetics and dynamics of the furin-cleaved form of PCSK9 [Research Articles]

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol metabolism by inducing the degradation of hepatic low-density lipoprotein receptor (LDLR). Plasma PCSK9 has two main molecular forms: a 62-kDa mature form (PCSK9_62) and a 55-kDa, furin-cleaved form (PCSK9_55). PCSK9_55 is considered less active than PCSK9_62 in degrading LDLR. We aimed to identify the site of PCSK9_55 formation (intra- vs. extracellular) and to further characterize the LDLR-degradative function of PCSK9_55 relative to PCSK9_62. Co-expressing PCSK9_62 with furin in cell culture induced formation of PCSK9_55, most of which was found in the extracellular space. Under the same conditions we found that: i) adding a cell-permeable furin inhibitor preferentially decreased the formation of PCSK9_55 extracellularly; ii) using pulse-chase, we observed the formation of PCSK9_55 exclusively extracellularly in a time-dependent manner. A recombinant form of PCSK9_55 was efficiently produced but displayed impaired secretion that resulted in its intracellular trapping. However, the non-secreted PCSK9_55 was able to induce degradation of LDLR, though with 50% lower efficiency compared with PCSK9_62. Collectively, our data show that PCSK9_55 is generated in the extracellular space, and that intracellular PCSK9_55 is not secreted but retains the ability to degrade the LDLR through an intracellular pathway.




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Generation and validation of a conditional knockout mouse model for the study of the Smith-Lemli-Opitz Syndrome [Research Articles]

Smith-Lemli-Opitz Syndrome (SLOS) is a developmental disorder (OMIM #270400) caused by autosomal recessive mutations in the Dhcr7 gene, which encodes the enzyme 3β-hydroxysterol-7 reductase. SLOS patients present clinically with dysmorphology and neurological, behavioral and cognitive defects, with characteristically elevated levels of 7-dehydrocholesterol (7-DHC) in all bodily tissues and fluids. Previous mouse models of SLOS have been hampered by postnatal lethality when Dhcr7 is knocked out globally, while a hypomorphic mouse model showed improvement in the biochemical phenotype with ageing, and did not manifest most other characteristic features of SLOS. We report the generation of a conditional knockout of Dhcr7 (Dhcr7flx/flx), validated by generating a mouse with a liver-specific deletion (Dhcr7L-KO). Phenotypic characterization of liver-specific knockout mice revealed no significant changes in viability, fertility, growth curves, liver architecture, hepatic triglyceride secretion, or parameters of systemic glucose homeostasis. Furthermore, qPCR and RNA-Seq analyses of livers revealed no perturbations in pathways responsible for cholesterol synthesis, either in male or female Dhcr7L-KO mice, suggesting hepatic disruption of post-squalene cholesterol synthesis leads to minimal impact on sterol metabolism in the liver. This validated conditional Dhcr7 knockout model may now allow us to systematically explore the pathophysiology of SLOS, by allowing for temporal, cell and tissue-specific loss of DHCR7.




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Multi-modal Functional Imaging of Brown Adipose Tissue [Images in Lipid Research]




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rHDL modelling and the anchoring mechanism of LCAT activation [Research Articles]

Lecithin:cholesterol-acyl-transferase (LCAT) plays a major role in cholesterol metabolism as it is the only extracellular enzyme able to esterify cholesterol. LCAT activity is required for lipoprotein remodelling and, most specifically, for the growth and maturation of HDLs. In fact, genetic alterations affecting LCAT func- tionality may cause a severe reduction in plasma levels of HDL-cholesterol with important clinical consequences. Although several hypotheses were formulated, the exact molecular recognition mechanism between LCAT and HDLs is still unknown. We employed a combination of structural bioinformatics procedures to deepen the insights into the HDL-LCAT interplay that promotes LCAT activation and cholesterol esterification. We have generated a data-driven model of reconstituted HDL (rHDL) and studied the dynamics of an assembled rHDL::LCAT supramolecular complex, pinpointing the conformational changes originating from the interaction between LCAT and apolipoprotein A-I (apoA-I) that are necessary for LCAT activation. Specifically, we propose a mechanism in which the anchoring of LCAT lid to apoA-I helices allows the formation of a hydrophobic hood that expands LCAT active site and shields it from the solvent, allowing the enzyme to process large hydrophobic substrates.




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Apolipoprotein C3 and apolipoprotein B colocalize in proximity to macrophages in atherosclerotic lesions in diabetes [Images in Lipid Research]