Contra-thermodynamic hydrogen atom abstraction in the selective C−H functionalization of trialkylamine N‑CH3 groups

We report a simple one-pot protocol that affords functionalization of N-CH3 groups in N-methyl-N,N-dialkylamines with high selectivity over N-CH2R or N-CHR2 groups. The radical cation DABCO+•, prepared in situ by oxidation of DABCO with a triarylaminium salt, effects highly selective and contra-thermodynamic C−H abstraction from N-CH3 groups. The intermediates that result react in situ with organometallic nucleophiles in a single pot, affording novel and highly selective homologation of N-CH3 groups. Chemoselectivity, scalability, and recyclability of reagents are demonstrated, and a mechanistic proposal is corroborated by computational and experimental results. The utility of the transformation is demonstrated in the late-stage site-selective functionalization of natural products and pharmaceuticals, allowing rapid derivatization for investigation of structure−activity relationships

Inferred support for disturbance-recovery hypothesis of North Atlantic phytoplankton blooms

Analyses of satellite-derived chlorophyll data indicate that the phase of rapid phytoplankton population growth in the North Atlantic (the ‘spring bloom') is actually initiated in the winter rather than the spring, contradicting Sverdrup's Critical Depth Hypothesis. An alternative disturbance-recovery hypothesis (DRH) has been proposed to explain this discrepancy, in which the rapid deepening of the mixed layer reduces zooplankton grazing rates sufficiently to initiate the bloom. We use Bayesian parameter inference on a simple Nutrient-Phytoplankton-Zooplankton (NPZ) to investigate the DRH and also investigate how well the model can capture the multiyear and spatial dynamics of phytoplankton concentrations and population growth rates. Every parameter in our NPZ model was inferred as a probability distribution given empirical constraints, this provides a more objective method to identify a model parameterisation given available empirical evidence, rather than fixing or tuning individual parameter values. Our model explains around 75% of variation in the seasonal dynamics of phytoplankton concentrations, 30% of variation in their population rates of change, and correctly predicts the phases of population growth and decline. Our parameter-inferred model supports DRH, revealing the sustained reduction of grazing due to mixed layer deepening as the driving mechanism behind bloom initiation, with the relaxation of nutrient limitation being another contributory mechanism. Our results also show that the continuation of the bloom is caused in part by the maintenance of phytoplankton concentrations below a level that can support positive zooplankton population growth. Our approach could be employed to formally assess alternative hypotheses for bloom formatio

Application of compositional models for glycan HILIC data

Glycoconjugates constitute a major class of biomolecules which include glycoproteins, glycosphingolipids and proteoglycans. The enzymatic process in which glycans (sugar chains) are linked to proteins or lipids is called glycosylation. Glycosylation is involved in many biological processes, both physiological and pathological, inlcuding host-pathogen interactions, tumour invasion, cell trafficking and signalling. Changes in glycan structure are thought be be at least partly responsible for the development of inflammation, infection, arteriosclerosis, immune defects and autoimmunity. Such changes have been observed in human diseases such as diabetes mellitus, rheumatoid arthritis and Alzheimer’s Disease. Aberrant patterns of glycosylation are also a universal feature of cancer cells. The field of glycobiology thus shows great potential for the discovery of glycan biomarkers for disease diagnosis and prognosis. Here we focus specifically on N-glycans, that is, glycans attached to protein molecules via a nitrogen atom. This class of glycans is the best characterized. High-throughput HILIC analysis is a well-established technique for the separation and quantification of N-linked glycans released from glycoproteins. HILIC analysis quantifies theN-glycan structures in serum via a chromatogram, which is subsequently standardized and integrated. The generated data for each sample is a set of relative HILIC peak areas and as a result, the data is compositional. To-date, most statistical analyses of these glycan data fail to account for their compositional nature. We compare and contrast three compositional data models for the glycan HILIC data: the Dirichlet, Nested Dirichlet and Logistic Normal models, with the intention of providing tools for the statistical analysis of compositional data analysis in the glycobiology field. We use these three models for classification of disease/control cases in ovarian and lung cancer diagnosis applications. We discuss and compare these models in terms of their classification performance and goodness-of-fit

A novel experimental technique and its application to study the effects of particle density and flow submergence on bed particle saltation

This research was sponsored by EPSRC grant EP/G056404/1 which is greatly appreciated.Peer reviewedPublisher PD

Association of Social Risk Factors With Mortality among Us adults With a New Cancer Diagnosis

This cohort study examines the associations of multiple social risk factors with mortality risk among patients newly diagnosed with cancer in the US

Targeting mitochondrial fitness as a strategy for healthy vascular aging.

Cardiovascular diseases (CVD) are the leading cause of death worldwide and aging is the primary risk factor for CVD. The development of vascular dysfunction, including endothelial dysfunction and stiffening of the large elastic arteries (i.e., the aorta and carotid arteries), contribute importantly to the age-related increase in CVD risk. Vascular aging is driven in large part by oxidative stress, which reduces bioavailability of nitric oxide and promotes alterations in the extracellular matrix. A key upstream driver of vascular oxidative stress is age-associated mitochondrial dysfunction. This review will focus on vascular mitochondria, mitochondrial dysregulation and mitochondrial reactive oxygen species (ROS) production and discuss current evidence for prevention and treatment of vascular aging via lifestyle and pharmacological strategies that improve mitochondrial health. We will also identify promising areas and important considerations ('research gaps') for future investigation.REVIEW ARTICLE| JUNE 25 2020 Targeting mitochondrial fitness as a strategy for healthy vascular aging Matthew J. Rossman ; Rachel A. Gioscia-Ryan ; Zachary S. Clayton ; Michael P. Murphy ; Douglas R. Seals Crossmark: Check for Updates Clin Sci (Lond) (2020) 134 (12): 1491–1519. https://doi.org/10.1042/CS20190559 Article history Split-Screen Views Icon Views PDF Link PDF Share Icon Share Cite Icon Cite Get Permissions Abstract Cardiovascular diseases (CVD) are the leading cause of death worldwide and aging is the primary risk factor for CVD. The development of vascular dysfunction, including endothelial dysfunction and stiffening of the large elastic arteries (i.e., the aorta and carotid arteries), contribute importantly to the age-related increase in CVD risk. Vascular aging is driven in large part by oxidative stress, which reduces bioavailability of nitric oxide and promotes alterations in the extracellular matrix. A key upstream driver of vascular oxidative stress is age-associated mitochondrial dysfunction. This review will focus on vascular mitochondria, mitochondrial dysregulation and mitochondrial reactive oxygen species (ROS) production and discuss current evidence for prevention and treatment of vascular aging via lifestyle and pharmacological strategies that improve mitochondrial health. We will also identify promising areas and important considerations (‘research gaps’) for future investigation. Keywords:arterial stiffness, endothelial function, mitophagy, oxidative stress, reactive oxygen species Subjects:Aging, Cardiovascular System & Vascular Biology, Translational Science Cardiovascular diseases (CVD) remain the largest contributor to morbidity and mortality in both developed and many developing nations [1,2]. Aging is by far the strongest risk factor for CVD, with >90% of all deaths occurring in adults 50 years of age and older [1,2]. Importantly, the changing demographics of aging characterized by a shift toward older populations [3] predicts a progressive, marked increase in prevalence of CVD in the absence of effective intervention [4]. A key mechanism by which aging increases CVD risk is the development of vascular dysfunction [5,6]. A number of adverse changes to the vasculature occur with aging, but two major clinically relevant expressions are endothelial dysfunction, as assessed by reduced arterial dilation in response to endothelium-derived nitric oxide (NO), and stiffening of the large elastic arteries (i.e., the aorta and carotid arteries) [5,6]. In combination, endothelial dysfunction and arterial stiffening contribute to a ‘vascular aging’ phenotype that drives much of the adverse effects of age on CVD. Vascular endothelial dysfunction The vascular endothelium is a single-cell layer lining the lumen of blood vessels. Endothelial cells play a critical role regulating vasomotor tone, metabolism, immune function, thrombosis and many other processes via synthesis and release of a variety of vasoactive molecules [7]. A major vasodilatory and largely vasoprotective molecule released by endothelial cells is NO, which is produced in response to mechanical (i.e., blood flow) and chemical (e.g., acetylcholine [ACh]) stimuli by the enzyme nitric oxide synthase (eNOS); eNOS catalyzes the generation of NO from L-arginine and oxygen, with NO subsequently diffusing to vascular smooth muscle cells where it induces vascular smooth muscle relaxation and vasodilation [7]. Endothelial dysfunction occurs with aging and is characterized by a decline in endothelium-dependent dilation (EDD), largely as a consequence of reductions in NO, although changes in concentrations of vasoactive factors such as prostaglandins, endothelin-1, norepinephrine and angiotensin II also contribute [7]. NO-mediated EDD can be determined in pre-clinical models by assessing changes in artery diameter in response to flow in vivo [8,9] or changes in diameter of isolated artery segments ex vivo in response to mechanical or pharmacological stimuli, such as ACh [10]. In humans, the gold-standard non-invasive assessment of NO-mediated EDD is brachial artery flow-mediated dilation (FMD), in which the change in brachial artery diameter in response to increases in blood flow is determined [10,11]. Brachial artery FMD primarily assesses macrovascular (conduit artery) function. Microvascular (resistance vessel) function can be determined by measuring changes in blood flow in response to intra-arterial infusions of ACh and is primarily assessed in the forearm [10,11]. These experimental approaches all demonstrate reduced endothelial function with aging in pre-clinical models and humans [12–17]. Endothelial dysfunction is the major antecedent of atherosclerosis [5,18] and both reduced brachial artery FMD and lower forearm blood flow responses to ACh are independent predictors of CV events and CVD in middle-aged and older adults free from clinical disease in large, community-based cohort studies [19–21]. Large elastic artery stiffening The aorta and carotid arteries expand and recoil as blood is ejected into the arterial system by the left ventricle during systole [22]. This action limits arterial pulsatile pressures by providing a dampening function and protects the downstream microvasculature from potentially damaging fluctuations in blood pressure and flow [23]. Moreover, the elastic recoil of the aorta aids in the propulsion of blood to the periphery and maintains perfusion of the heart during diastole [22]. With aging, aortic stiffening results in blood being ejected into a stiffer aorta, which augments central systolic blood pressure because the ejected pressure wave travels at a higher velocity in stiffer arteries and is reflected by points of impedance such that the returning pressure wave reaches the heart at mid-to-late systole [22,24]. In addition, the greater forward moving pressure wave amplitude (from systolic ejection, prior to the return of wave reflections) is a major contributor to the age-related increase in central systolic blood pressure after age 60, particularly in women, as a consequence of a plateau or decrease in reflected wave amplitude [25,26]. The augmented systolic blood pressure, in turn, contributes to isolated systolic hypertension and results in a loss of diastolic pressure augmentation, such that aortic pulse pressure is widened [22,24]. Aortic stiffening therefore increases left ventricular afterload during systole, promoting left ventricular hypertrophy and dysfunction, and compromises coronary perfusion during diastole because of the reduced augmentation of diastolic pressure [24,27]. The loss of pulsatility-dampening effects of the aorta and the carotid artery also allows for transmission of high pulsatile pressures to the delicate small vessels in the microcirculation, which is particularly harmful for high-flow, low-resistance organs such as the brain and kidney, and a potential causative factor in target organ damage [23]. Structural changes to arteries, functional influences (i.e., factors influencing vascular smooth muscle tone) and the stiffness of vascular smooth muscle cells contribute to large elastic artery stiffening with aging [28,29]. The primary structural changes mediating arterial stiffening occur in the extracellular matrix and include degradation/fragmentation of elastin (e.g., by matrix metalloproteinases), an increase in the deposition of collagen and formation of advanced glycation end products (AGEs), which cross-link collagen fibers, increasing their stiffness [5,30,31]. Increased vascular smooth muscle tone is a consequence of changes such as reductions in NO and increased sympathetic nervous system, endothelin-1 and renin–angiotensin aldosterone system activity [32–34]. These factors also influence the intrinsic stiffness of the vascular smooth muscle cells, which adds to the stiffness of the arterial wall [29]. The mechanical stiffness of the large elastic arteries can be determined ex vivo in pre-clinical models by directly measuring properties such as compliance by creating stress-strain curves [35,36]. In vivo, arterial stiffness can be assessed in pre-clinical settings and humans with pulse wave velocity (PWV), which is a measure of the (regional) speed of the pulse wave generated by the heart when blood is ejected into the arterial system [22]. Aortic PWV is the predominant measure in rodents and carotid-femoral PWV is the reference standard measure of aortic stiffness in humans [10,22]. Carotid-femoral PWV increases with aging and is a strong, independent predictor of CVD risk in older adults [37,38]. Moreover, consistent with aortic stiffness-associated end organ damage, growing evidence supports an association between elevated carotid-femoral PWV and other age-related clinical disorders such as cognitive decline, dementia, including Alzheimer’s disease, and decreases in renal function/chronic kidney disease [39–43]. The local distensibility of the carotid artery can also be determined in humans by measuring carotid artery compliance (the change in artery diameter for a given change in arterial pressure) and determining the carotid distensibility coefficient (i.e., changes in artery diameter normalized to diastolic lumen diameter) and/or carotid beta-stiffness index, which is largely independent of blood pressure [10,22]. Carotid artery compliance is associated with incident stroke, independent of aortic stiffness [44]. Mechanisms of vascular dysfunction with aging The primary molecular mechanisms of vascular aging are oxidative stress and chronic, low grade inflammation [45,46] (Figure 1). Excessive production of reactive oxygen species (ROS) in combination with unchanged or decreased abundance/activity of antioxidant enzymes (e.g., superoxide dismutase, SOD) results in the development of oxidative stress in arteries with aging [24,45]. Excess superoxide rapidly reacts with NO to form the secondary reactive species peroxynitrite (ONOO−), decreasing the bioavailability of NO [24,45], causing endothelial dysfunction. Peroxynitrite is also the primary molecule that reacts with and oxidizes tetrahydrobiopterin (BH4), an essential co-factor for NO production by eNOS [47]. Loss of BH4 leads to eNOS uncoupling, whereby eNOS produces more superoxide and less NO, exacerbating oxidative stress and decreasing bioavailable NO and endothelial cell function [47]. Excess ROS also can activate pro-inflammatory networks such as those regulated by the transcription factor nuclear factor kappa B (NF-kB), which up-regulates the production of pro-inflammatory cytokines that can impair vascular function and activate other ROS producing systems and enzymes, creating an adverse feed-forward (vicious) cycle of inflammation and oxidative stress [24,45]. Figure 1 Aging is associated with mitochondrial dysfunction-induced increases in reactive oxygen species (ROS) and oxidative stress and increases in pro-inflammatory cytokine signaling and chronic low-grade inflammation. Together, these processes induce vascular dysfunction, featuring: (lower left) large elastic artery stiffening mediated by degradation of elastin fibers (blue), increased deposition of collagen (brown), and greater cross-linking of structural proteins by advanced glycation end-products (dashed connecting lines); and (right) vascular endothelial dysfunction characterized by reduced nitric oxide (NO) bioavailability and endothelium-dependent dilation. These and other changes to arteries, in turn, increase the risk of developing cardiovascular diseases, chronic kidney disease, and Alzheimer’s disease and related dementias. VIEW LARGEDOWNLOAD SLIDE Mechanisms of age-associated vascular dysfunction and related clinical disorders Aging is associated with mitochondrial dysfunction-induced increases in reactive oxygen species (ROS) and oxidative stress and increases in pro-inflammatory cytokine signaling and chronic low-grade inflammation. Together, these processes induce vascular dysfunction, featuring: (lower left) large elastic artery stiffening mediated by degradation of elastin fibers (blue), increased deposition of collagen (brown), and greater cross-linking of structural proteins by advanced glycation end-products (dashed connecting lines); and (right) vascular endothelial dysfunction characterized by reduced nitric oxide (NO) bioavailability and endothelium-dependent dilation. These and other changes to arteries, in turn, increase the risk of developing cardiovascular diseases, chronic kidney disease, and Alzheimer’s disease and related dementias. This overall state of oxidative stress and inflammation also contributes to arterial stiffening with aging by altering the structural properties of the arterial wall. Production of collagen by fibroblasts is stimulated by superoxide-related oxidative stress [30,48,49]. Matrix metalloproteinases are up-regulated and elastin content is lower in aorta of SOD-deficient mice, consistent with the concept that elastin degradation is induced by oxidative stress [50]. Vascular oxidative stress also promotes transforming growth factor β signaling and this, in turn, stimulates inflammation, which further reinforces arterial stiffness via activation of the pro-oxidant enzyme, NADPH oxidase [48]. AGEs interact with the receptor for AGEs to activate NFkB-regulated pro-inflammatory pathways and oxidative stress, which ultimately perpetuates arterial stiffening and further increases production of AGEs [51]. Mitochondrial dysfunction is emerging as a key source of vascular oxidative stress and contributor to age-related vascular dysfunction. The remaining sections of this article will focus on mitochondrial dysfunction as a driver of vascular aging and review current evidence for prevention/treatment of age-associated vascular dysfunction via lifestyle and pharmacological strategies that improve mitochondrial health. We will also discuss current ‘research gaps’ and future directions for the field. Vascular mitochondria, mitochondrial dysregulation and ROS Mitochondria are cytoplasmic organelles that are present in the majority of cell types in the human body, including vascular endothelial and smooth muscle cells. Mitochondria are often referred to as the ‘powerhouse’ of the cell for their role in ATP production by oxidative phosphorylation, which occurs via a series of electron transfers through the respiratory chain in the mitochondrial inner membrane that is coupled to ATP synthesis by the FoF1-ATP synthase by the protonmotive force across the inner membrane. However, mitochondria are also vital for a number of additional cellular processes, including regulation of metabolism, calcium homeostasis, immune function, cell growth and stem cell function, and cell death pathways. Although mitochondrial density in vascular tissues is considerably lower than other tissues such as skeletal muscle, liver and heart [52,53], increasing evidence indicates that these organelles are critical for maintenance of cellular and tissue homeostasis in the vasculature. This topic has been reviewed in detail elsewhere [54–61], but below we briefly summarize some of the key roles of mitochondria in the vasculature. A first important distinction is to consider the vascular cell type in question, as the density and subcellular distribution of mitochondria vary between endothelial and vascular smooth muscle cells, and indeed even among the same cell types in different vascular beds [54,60]. In general, unlike in highly metabolically active tissues with greater ATP demand, the principal role of mitochondria in the vasculature appears to be cellular signaling rather than energy provision [54]. Cellular energy demand is quite low in endothelial cells, and ATP demand is met primarily via glycolysis. However, endothelial mitochondria are critical in the regulation of calcium homeostasis, apoptosis/necrosis, cellular response to stress, and immune and inflammatory pathways. An essential feature of these roles is the regulated production of signaling molecules including redox-active molecules (reactive oxygen, nitrogen and other species; mtROS), mitochondrial DNA, mitochondria-derived peptides and damage-associated molecular pattern molecules (DAMPs), which exert effects intra- and extra-cellularly [62]. Importantly, there is cross-talk between mitochondrial and nuclear signaling pathways, whereby mitochondria-derived signaling is both influenced by and can influence nuclear events including gene expression [63]. Similarly, in vascular smooth muscle cells, mitochondria have an important role in cellular signaling. Mitochondria are involved in signaling pathways for regulation of vascular smooth muscle cell growth and proliferation (e.g., TGF-β activity) [64], as well as maintenance of the dynamic balance among synthesis and breakdown of extracellular structural proteins, including collagen and elastin (e.g., matrix metalloproteinase enzyme activities) [65]. There is also emerging evidence demonstrating interplay between mtROS signaling and inflammatory pathways known to be important for regulating vascular smooth muscle cell function, including those involving NFkB and the NLRP3-inflammasome [66–69], further highlighting the crucial role of mtROS in vascular homeostasis. Mitochondrial ROS The signaling functions of vascular mitochondria are thought to be mediated in large part by the production of ROS at low, physiological levels. However, the dysregulation of this mtROS production also has the potential to lead to pathophysiological sequelae that disrupt other mitochondrial functions, cellular homeostasis, and ultimately vascular function. The production of ROS by mitochondria can occur at several sites (Figure 2), including but not limited to the electron transport proteins, and this topic has been reviewed in detail elsewhere [54,60,70]. The most important sites for ROS production within mitochondria appear to be complexes I and III. These ROS are thought to be critical transducers of signaling mediated by mitochondria, leading to post-transcriptional modification of proteins and interactions with immune and inflammatory cellular pathways, although the mechanistic details are still uncertain. In the vasculature, the proximal mtROS species is superoxide, which is generated primarily at the electron transport chain in the mitochondrial inner membrane via interaction between oxygen and unpaired electrons, influenced by the proton motive force and the redox state of the coenzyme Q pool and integrity of intrinsic electron transport chain proteins [54,58,60,70]. Superoxide is released into the matrix (complex I) or into both the matrix and intermembrane space (complex III); it can also undergo dismutation to hydrogen peroxide by the antioxidant enzyme manganese superoxide dismutase (MnSOD) [59,60,62,70]. Hydrogen peroxide is also generated de novo on the surface of the mitochondrial outer membrane or in the intermembrane space mitochondria by p66SHC, a growth factor adapter protein referred to as a sensor/marker and ‘master regulator’ of mitochondrial redox signaling whose activity is indicative of the rate of mtROS production [71]. In addition, NADPH oxidase 4 (NOX4) is viewed as a primarily mitochondrial isoform of the NOX monoamine oxidase family of enzymes that contributes to mitochondrial hydrogen peroxide generation [72], although more research is needed to confirm the mitochondrial specificity of NOX4. Figure 2 Aging is associated with dysregulated mitochondrial quality control featuring reduced mitochondrial biogenesis (upper left) and reduced mitophagy (upper right), increased mitochondrial fission (upper middle right), reduced mitochondrial fusion (lower middle right), reduced mitochondrial stress resistance (lower right), increased mitochondrial DNA damage (middle left of mitochondria image) and increased bioactivity of mitochondrial reactive oxygen species (e.g., superoxide and other reactive oxygen species [ROS], middle of mitochondria image) relative to antioxidant defenses (e.g., manganese superoxide dismutase [SOD], lower right of mitochondria). VIEW LARGEDOWNLOAD SLIDE Mechanisms of age-associated mitochondrial dysfunction Aging is associated with dysregulated mitochondrial quality control featuring reduced mitochondrial biogenesis (upper left) and reduced mitophagy (upper right), increased mitochondrial fission (upper middle right), reduced mitochondrial fusion (lower middle right), reduced mitochondrial stress resistance (lower right), increased mitochondrial DNA damage (middle left of mitochondria image) and increased bioactivity of mitochondrial reactive oxygen species (e.g., superoxide and other reactive oxygen species [ROS], middle of mitochondria image) relative to antioxidant defenses (e.g., manganese superoxide dismuta

Brief bouts of device-measured intermittent lifestyle physical activity and its association with major adverse cardiovascular events and mortality in people who do not exercise: a prospective cohort study

BACKGROUND: Guidelines emphasise the health benefits of bouts of physical activity of any duration. However, the associations of intermittent lifestyle physical activity accumulated through non-exercise with mortality and major adverse cardiovascular events (MACE) remain unclear. We aimed to examine the associations of bouts of moderate-to-vigorous intermittent lifestyle physical activity (MV-ILPA) and the proportion of vigorous activity contributing within these bouts with mortality and MACE. METHODS: In this prospective cohort study, we used data from the UK Biobank on adults who do not exercise (ie, those who did not report leisure-time exercise) who had wrist-worn accelerometry data available. Participants were followed up until Nov 30, 2022, with the outcome of interest of all-cause mortality obtained through linkage with NHS Digital of England and Wales, and the NHS Central Register and National Records of Scotland, and MACE obtained from inpatient hospitalisation data provided by the Hospital Episode Statistics for England, the Patient Episode Database for Wales, and the Scottish Morbidity Record for Scotland. MV-ILPA bouts were derived using a two-level Random Forest classifier and grouped as short (<1 min), medium (1 to <3 min; 3 to <5 min), and long (5 to <10 min). We further examined the dose-response relationship of the proportion of vigorous physical activity contributing to the MV-ILPA bout. FINDINGS: Between June 1, 2013, and Dec 23, 2015, 103 684 Biobank participants wore an accelerometer on their wrist. 25 241 adults (mean age 61·8 years [SD 7·6]), of whom 14 178 (56·2%) were women, were included in our analysis of all-cause mortality. During a mean follow-up duration of 7·9 years (SD 0·9), 824 MACE and 1111 deaths occurred. Compared with bouts of less than 1 min, mortality risk was lower for bouts of 1 min to less than 3 min (hazard ratio [HR] 0·66 [0·53-0·81]), 3 min to less than 5 min (HR 0·56 [0·46-0·69]), and 5 to less than 10 min (HR 0·48 [0·39-0·59]). Similarly, compared with bouts of less than 1 min, risk of MACE was lower for bouts of 1 min to less than 3 min (HR 0·71 [0·54-0·93]), 3 min to less than 5 min (0·62 [0·48-0·81]), and 5 min to less than 10 min (0·59 [0·46-0·76]). Short bouts (<1 min) were associated with lower MACE risk only when bouts were comprised of at least 15% vigorous activity. INTERPRETATION: Intermittent non-exercise physical activity was associated with lower mortality and MACE. Our results support the promotion of short intermittent bouts of non-exercise physical activity of moderate-to-vigorous intensity to improve longevity and cardiovascular health among adults who do not habitually exercise in their leisure time. FUNDING: Australian National Health, Medical Research Council, and Wellcome Trust

Reexamining Chronic \u3cem\u3eToxoplasma gondii\u3c/em\u3e Infection: Surprising Activity for a Dormant Parasite

Purpose of Review Despite over a third of the world’s population being chronically infected with Toxoplasma gondii, little is known about this largely asymptomatic phase of infection. This stage is mediated in vivo by bradyzoites within tissue cysts. The absence of overt symptoms has been attributed to the dormancy of bradyzoites. In this review, we reexamine the conventional view of chronic toxoplasmosis in light of emerging evidence challenging both the nature of dormancy and the consequences of infection in the CNS. Recent Findings New and emerging data reveal a previously unrecognized level of physiological and replicative capacity of bradyzoites within tissue cysts. These findings have emerged in the context of a reexamination of the chronic infection in the brain that correlates with changes in neuronal architecture, neurochemistry, and behavior that suggest that the chronic infection is not without consequence. Summary The emerging data driven by the development of new approaches to study the progression of chronic toxoplasma infection reveals significant physiological and replicative capacity for what has been viewed as a dormant state. The emergence of bradyzoite and tissue cyst biology from what was viewed as a physiological “black box” offers exciting new areas for investigation with direct implications on the approaches to drug development targeting this drug-refractory state. In addition, new insights from studies on the neurobiology on chronic infection reveal a complex and dynamic interplay between the parasite, brain microenvironment, and the immune response that results in the detente that promotes the life-long persistence of the parasite in the host

TIMP-3 facilitates binding of target metalloproteinases to the endocytic receptor LRP-1 and promotes scavenging of MMP-1

Matrix metalloproteinases (MMPs) and the related families of disintegrin metalloproteinases (ADAMs) and ADAMs with thrombospondin repeats (ADAMTSs) play a crucial role in extracellular matrix (ECM) turnover and shedding of cell-surface molecules. The proteolytic activity of metalloproteinases is post-translationally regulated by their endogenous inhibitors, known as tissue inhibitors of metalloproteinases (TIMPs). Several MMPs, ADAMTSs and TIMPs have been reported to be endocytosed by the low-density lipoprotein receptor-related protein-1 (LRP-1). Different binding affinities of these proteins for the endocytic receptor correlate with different turnover rates which, together with differences in their mRNA expression, determines their nett extracellular levels. In this study, we used surface plasmon resonance to evaluate the affinity between LRP-1 and a number of MMPs, ADAMs, ADAMTSs, TIMPs and metalloproteinase/TIMP complexes. This identified MMP-1 as a new LRP-1 ligand. Among the proteins analyzed, TIMP-3 bound to LRP-1 with highest affinity (KD = 1.68 nM). Additionally, we found that TIMP-3 can facilitate the clearance of its target metalloproteinases by bridging their binding to LRP-1. For example, the free form of MMP-1 was found to have a KD of 34.6 nM for LRP-1, while the MMP-1/TIMP-3 complex had a sevenfold higher affinity (KD = 4.96 nM) for the receptor. TIMP-3 similarly bridged binding of MMP-13 and MMP-14 to LRP-1. TIMP-1 and TIMP-2 were also found to increase the affinity of target metalloproteinases for LRP-1, albeit to a lesser extent. This suggests that LRP-1 scavenging of TIMP/metalloproteinase complexes may be a general mechanism by which inhibited metalloproteinases are removed from the extracellular environment