Multiomics analyses reveal dynamic bioenergetic pathways and functional remodeling of the heart during intermittent fasting.

Intermittent fasting (IF) has been shown to reduce cardiovascular risk factors in both animals and humans, and can protect the heart against ischemic injury in models of myocardial infarction. However, the underlying molecular mechanisms behind these effects remain unclear. To shed light on the molecular and cellular adaptations of the heart to IF, we conducted comprehensive system-wide analyses of the proteome, phosphoproteome, and transcriptome, followed by functional analysis. Using advanced mass spectrometry, we profiled the proteome and phosphoproteome of heart tissues obtained from mice that were maintained on daily 12- or 16 hr fasting, every-other-day fasting, or ad libitum control feeding regimens for 6 months. We also performed RNA sequencing to evaluate whether the observed molecular responses to IF occur at the transcriptional or post-transcriptional levels. Our analyses revealed that IF significantly affected pathways that regulate cyclic GMP signaling, lipid and amino acid metabolism, cell adhesion, cell death, and inflammation. Furthermore, we found that the impact of IF on different metabolic processes varied depending on the length of the fasting regimen. Short IF regimens showed a higher correlation of pathway alteration, while longer IF regimens had an inverse correlation of metabolic processes such as fatty acid oxidation and immune processes. Additionally, functional echocardiographic analyses demonstrated that IF enhances stress-induced cardiac performance. Our systematic multi-omics study provides a molecular framework for understanding how IF impacts the heart's function and its vulnerability to injury and disease.

Inflammasome Activation Mediates Apoptotic and Pyroptotic Death in Astrocytes Under Ischemic Conditions.

Inflammation is a hallmark mechanism of ischemic stroke-induced brain injury. Recent studies have shown that an intracellular multimeric protein complex known as an inflammasome is a key factor for inducing an inflammatory response, and apoptotic and pyroptotic cell death in ischemic stroke. Inflammasome assembly leads to the activation of pro-inflammatory caspases, and the maturation and secretion of pro-inflammatory cytokines IL-1ß and IL-18. While the role of inflammasomes in ischemic stroke-induced neuronal death, and microglial activation and cell death have been established, little is known about the role of inflammasomes in astrocytes under ischemic conditions. In this study, we investigated the expression and activation of inflammasome components in protoplasmic and fibrous astrocytes under ischemic conditions. We found that both protoplasmic and fibrous astrocytes expressed a differential increase in inflammasome protein components, and that their activation promoted maturation of IL-1ß and IL-18, and secretion of IL-1ß, as well as initiating apoptotic and pyroptotic cell death. Pharmacological inhibition of caspase-1 decreased expression of cleaved caspase-1 and production of mature IL-1ß, and protected against inflammasome-mediated apoptotic and pyroptotic cell death. Overall, this study provides novel insights into the role of inflammasome signaling in astrocytes under ischemic conditions.

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment.

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

Chronic cerebral hypoperfusion alters the CypA-EMMPRIN-gelatinase pathway: Implications for vascular dementia.

Chronic cerebral hypoperfusion (CCH) is postulated to underlie multiple pathophysiological processes in vascular dementia (VaD), including extracellular matrix dysfunction. While several extracellular matrix proteins, namely cyclophilin A (CypA), extracellular matrix metalloproteinase inducer (EMMPRIN) and gelatinases (matrix metalloproteinases, MMP-2 and -9) have been investigated in acute stroke, their involvement in CCH and VaD remains unclear. In this study, CypA-EMMPRIN-gelatinase proteins were analysed in a clinical cohort of 36 aged, cognitively unimpaired subjects and 48 VaD patients, as well as in a bilateral carotid artery stenosis mouse model of CCH. Lower CypA and higher EMMPRIN levels were found in both VaD serum and CCH mouse brain. Furthermore, gelatinases were differentially altered in CCH mice and VaD patients, with significant MMP-2 increase in CCH brain and serum, whilst serum MMP-9 was elevated in VaD but reduced in CCH, suggesting complex CypA-EMMPRIN-gelatinase regulatory mechanisms. Interestingly, subjects with cortical infarcts had higher serum MMP-2, while white matter hyperintensities, cortical infarcts and lacunes were associated with higher serum MMP-9. Taken together, our data indicate that perturbations of CypA-EMMPRIN signalling may be associated with gelatinase-mediated vascular sequelae, highlighting the potential utility of the CypA-EMMPRIN-gelatinase pathway as clinical biomarkers and therapeutic targets in VaD.

Governance of Assisted Living in Singapore: Lessons for Aging Countries.

A global trend toward aging populations means that the challenge of providing adequate long-term care to older people looms large in many countries. In Singapore, a public discourse revolving around the expansion of assisted living to create age-friendly environments in long-term care has emerged. This study examines Singapore's experience in developing regulations for assisted living by documenting the different levels of regulation in place and by identifying the regulatory gaps remaining to govern assisted living. Anchoring in a conceptual framework on the governance of assisted living, different regulatory components of assisted living at the micro-, meso-, and macro-levels are analyzed. Using a case study method, primary and secondary data examining the experiences of governing and implementing assisted living in Singapore were collected. Analysis was conducted using a thematic analysis approach. Micro- and some macro-level regulations, which include admission assessment, staffing, and infrastructural requirements for assisted living, are maturing and evolving, while meso-level regulations, such as operational management, the monitoring framework, and stipulations for training requirements for staff, remain a work-in-progress in Singapore. The regulations for assisted living are currently primarily guided by soft laws, such as practice guidelines; the government has committed toward enacting permanent regulations for all long-term care facilities with the phased implementation of the Health Care Services Act from 2021 to 2023. We conclude that assisted living, despite the early stage of its development in Singapore, is a viable care model that should be expanded to meet the rising demand for care on the part of a majority of older people, who fall in the middle of the care continuum (that is, they can neither live independently nor need complete institutionalization). We also propose five policy recommendations for all aging countries to strengthen the governance of assisted living in long-term care. These include establishing (i) clear provisions on care quality assessment and the redress of grievance, (ii) minimum standards of care, (iii) differential regulations for assisted living, (iv) routine care assessment, and, (v) applying technology in assisted living facilities to address a shortage of care workers.

The role of inflammasomes in vascular cognitive impairment.

There is an increasing prevalence of Vascular Cognitive Impairment (VCI) worldwide, and several studies have suggested that Chronic Cerebral Hypoperfusion (CCH) plays a critical role in disease onset and progression. However, there is a limited understanding of the underlying pathophysiology of VCI, especially in relation to CCH. Neuroinflammation is a significant contributor in the progression of VCI as increased systemic levels of the proinflammatory cytokine interleukin-1ß (IL-1ß) has been extensively reported in VCI patients. Recently it has been established that CCH can activate the inflammasome signaling pathways, involving NLRP3 and AIM2 inflammasomes that critically regulate IL-1ß production. Given that neuroinflammation is an early event in VCI, it is important that we understand its molecular and cellular mechanisms to enable development of disease-modifying treatments to reduce the structural brain damage and cognitive deficits that are observed clinically in the elderly. Hence, this review aims to provide a comprehensive insight into the molecular and cellular mechanisms involved in the pathogenesis of CCH-induced inflammasome signaling in VCI.

Governance of Assisted Living in Long-Term Care: A Systematic Literature Review.

Assisted living (AL) is an emerging model of care in countries where long-term care needs are escalating, with emphasis given to promoting independence and autonomy among the residents to achieve active and healthy ageing. Unlike established nursing homes, the governance of AL is nebulous due to its novelty and diverse nature of operations in many jurisdictions. A comprehensive understanding of how AL is governed globally is important to inform regulatory policies as the adoption of AL increases. A systematic literature review was undertaken to understand the different levels of regulations that need to be instituted to govern AL effectively. A total of 65 studies, conducted between 1990 to 2020, identified from three major databases (PubMed, Medline, and Scopus), were included. Using a thematic synthesis analytical approach, we identified macro-level regulations (operational authorisation, care quality assessment and infrastructural requirements), meso-level regulations (operational management, staff management and distribution, service provision and care monitoring, and crisis management), and micro-level regulations (clear criteria for resident admission and staff hiring) that are important in the governance of AL. Large-scale adoption of AL without compromising the quality, equity and affordability would require clear provisions of micro-, meso- and macro-level regulations.

AIM2 inflammasome mediates apoptotic and pyroptotic death in the cerebellum following chronic hypoperfusion.

Vascular dementia (VaD) is the second most common form of dementia and is caused by vascular pathologies resulting in chronic cerebral hypoperfusion (CCH)- induced brain injury, and ultimately cognitive impairment and memory loss. Several lines of evidence have demonstrated chronic inflammation may be involved in VaD disease progression. It is now recognized that a major contributor to cerebral and systemic chronic inflammation involves the activation of innate immune molecular complexes termed inflammasomes. Whilst previous studies on animal models of VaD have focused on the cortex, hippocampus and striatum, few studies have investigated the effect of CCH on the cerebellum. Emerging studies have found new roles of the cerebellum in cognition, based on its structural interconnectivity with other brain regions and clinical relevance in neuropsychological deficits. In the present study, we conducted our investigation on the cerebellum using a CCH mouse model of VaD following bilateral common carotid artery stenosis (BCAS). This study is the first to characterize an increased expression of inflammasome receptors, adaptor and effector proteins, markers of inflammasome activation, proinflammatory cytokines, and apoptotic and pyroptotic cell death proteins in the cerebellum following CCH. Furthermore, in AIM2 knockout mice, we observed attenuated inflammasome-mediated production of proinflammatory cytokines, apoptosis, and pyroptosis in the cerebellum following CCH. Collectively, our findings provide novel evidence that AIM2 inflammasome activation promotes apoptosis and pyroptosis in the cerebellum following chronic hypoperfusion in a mouse model of VaD.

Hippocampal transcriptome profiling reveals common disease pathways in chronic hypoperfusion and aging.

Vascular dementia (VaD) is a progressive cognitive impairment of vascular etiology. VaD is characterized by cerebral hypoperfusion, increased blood-brain barrier permeability and white matter lesions. An increased burden of VaD is expected in rapidly aging populations. The hippocampus is particularly susceptible to hypoperfusion, and the resulting memory impairment may play a crucial role in VaD. Here we have investigated the hippocampal gene expression profile of young and old mice subjected to cerebral hypoperfusion by bilateral common carotid artery stenosis (BCAS). Our data in sham-operated young and aged mice reveal an age-associated decline in cerebral blood flow and differential gene expression. In fact, BCAS and aging caused broadly similar effects. However, BCAS-induced changes in hippocampal gene expression differed between young and aged mice. Specifically, transcriptomic analysis indicated that in comparison to young sham mice, many pathways altered by BCAS in young mice resembled those already present in sham aged mice. Over 30 days, BCAS in aged mice had minimal effect on either cerebral blood flow or hippocampal gene expression. Immunoblot analyses confirmed these findings. Finally, relative to young sham mice the cell type-specific profile of genes in both young BCAS and old sham animals further revealed common cell-specific genes. Our data provide a genetic-based molecular framework for hypoperfusion-induced hippocampal damage and reveal common cellular signaling pathways likely to be important in the pathophysiology of VaD.

Intermittent fasting attenuates inflammasome-associated apoptotic and pyroptotic death in the brain following chronic hypoperfusion.

Chronic cerebral hypoperfusion (CCH) has been shown to initiate several inflammatory pathways that can contribute to cognitive deficits and memory loss in vascular cognitive impairment (VCI). Multi-protein complexes termed inflammasomes that may be involved in the inflammatory response to CCH has already been shown to contribute to the inflammatory process and cell death following acute cerebral ischemia. Intermittent fasting (IF) has already been shown to decrease inflammasome activation and protect the brain from ischemic stroke; however, its effects during CCH remains unknown. The present study investigated the impact of IF (16 h of food deprivation daily) for four months on inflammasome-mediated cell death in the cerebellum following CCH in a mouse model of VCI using fourteen to sixteen-week-old male C57BL/6NTac mice. Here we demonstrated that IF decreased inflammasome activation, and initiation of apoptotic and pyroptotic cell death pathways as reflected by the reduction (20-30%) in the expression levels of key effector proteins and cell death markers in the cerebellum following CCH. In summary, our results indicate that IF can attenuate the inflammatory response and cell death pathways in the brain following chronic hypoperfusion in a mouse model of VCI.

AIM2 inflammasome mediates hallmark neuropathological alterations and cognitive impairment in a mouse model of vascular dementia.

Chronic cerebral hypoperfusion is associated with vascular dementia (VaD). Cerebral hypoperfusion may initiate complex molecular and cellular inflammatory pathways that contribute to long-term cognitive impairment and memory loss. Here we used a bilateral common carotid artery stenosis (BCAS) mouse model of VaD to investigate its effect on the innate immune response-particularly the inflammasome signaling pathway. Comprehensive analyses revealed that chronic cerebral hypoperfusion induces a complex temporal expression and activation of inflammasome components and their downstream products (IL-1ß and IL-18) in different brain regions, and promotes activation of apoptotic and pyroptotic cell death pathways. Polarized glial-cell activation, white-matter lesion formation and hippocampal neuronal loss also occurred in a spatiotemporal manner. Moreover, in AIM2 knockout mice we observed attenuated inflammasome-mediated production of proinflammatory cytokines, apoptosis, and pyroptosis, as well as resistance to chronic microglial activation, myelin breakdown, hippocampal neuronal loss, and behavioral and cognitive deficits following BCAS. Hence, we have demonstrated that activation of the AIM2 inflammasome substantially contributes to the pathophysiology of chronic cerebral hypoperfusion-induced brain injury and may therefore represent a promising therapeutic target for attenuating cognitive impairment in VaD.

CD137 Ligand-CD137 Interaction is Required For Inflammasome-Associated Brain Injury Following Ischemic Stroke.

The CD137L-CD137 axis is a potent co-stimulatory immune checkpoint regulator that forms a bidirectional signaling pathway between the CD137 ligand (CD137L) and CD137 receptor to regulate immunological activities. This study investigated the potential involvement of the CD137L-CD137 axis on inflammasome-associated brain injury and neurological deficits in a mouse model of focal ischemic stroke. Cerebral ischemia was induced in male C57BL/6J wild-type (WT), CD137L-deficient (CD137L KO) and CD137-deficient (CD137 KO) mice by middle cerebral artery occlusion (MCAO; 60 min), followed by reperfusion (6 h and 24 h). Brain infarct volume and neurological deficit scores were significantly lower in both CD137L KO and CD137 KO mice compared to WT controls. Moreover, CD137L-deficient brains had significantly lower levels of the pyroptotic protein, NT-Gasdermin D, while CD137-deficient brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3, pyroptotic protein, NT-Gasdermin D, and of the secondary pyroptotic protein NT-Gasdermin E, following ischemic stroke. This protection by CD137L and CD137 deletion was associated with a significant decrease in inflammasome signaling. In conclusion, our data provide evidence for the first time that the CD137L-CD137 axis contributes to brain injury and neurological deficits by activating the inflammasome signaling pathway following ischemic stroke.

Negative Conditioning of Mitochondrial Dysfunction in Age-related Neurodegenerative Diseases.

Mitochondrial dysfunction is regarded as one of the major causes of neuronal injury in age-associated neurodegenerative diseases and stroke. Mitochondrial dysfunction leads to increased reactive oxygen species production, causing mitochondrial DNA mutations, which then results in pathological conditions. Negative conditioning of mitochondrial dysfunction via pharmacological inhibition, phytochemicals, and dietary restriction serve as an avenue for therapeutic intervention to improve mitochondrial quality and function. Here, we focus primarily on mitochondrial biology, evidence for mitochondrial dysfunction in neurodegenerative conditions such as dementia and stroke, and the possibility of using negative conditioning to restore or preserve mitochondrial function in these diseases.

Evidence that NLRC4 inflammasome mediates apoptotic and pyroptotic microglial death following ischemic stroke.

Stroke is the second leading cause of death in the world and a major cause of long-term disability. Recent evidence has provided insight into a newly described inflammatory mechanism that contributes to neuronal and glial cell death, and impaired neurological outcome following ischemic stroke - a form of sterile inflammation involving innate immune complexes termed inflammasomes. It has been established that inflammasome activation following ischemic stroke contributes to neuronal cell death, but little is known about inflammasome function and cell death in activated microglial cells following cerebral ischemia. Microglia are considered the resident immune cells that function as the primary immune defense in the brain. This study has comprehensively investigated the expression and activation of NLRP1, NLRP3, NLRC4 and AIM2 inflammasomes in isolates of microglial cells subjected to simulated ischemic conditions and in the brain following ischemic stroke. Immunoblot analysis from culture media indicated microglial cells release inflammasome components and inflammasome activation-dependent pro-inflammatory cytokines following ischemic conditions. In addition, a functional role for NLRC4 inflammasomes was determined using siRNA knockdown of NLRC4 and pharmacological inhibitors of caspase-1 and -8 to target apoptotic and pyroptotic cell death in BV2 microglial cells under ischemic conditions. In summary, the present study provides evidence that the NLRC4 inflammasome complex mediates the inflammatory response, as well as apoptotic and pyroptotic cell death in microglial cells under in vitro and in vivo ischemic conditions.

Acute or Delayed Systemic Administration of Human Amnion Epithelial Cells Improves Outcomes in Experimental Stroke.

BACKGROUND AND PURPOSE: Human amnion epithelial cells (hAECs) are nonimmunogenic, nontumorigenic, anti-inflammatory cells normally discarded with placental tissue. We reasoned that their profile of biological features, wide availability, and the lack of ethical barriers to their use could make these cells useful as a therapy in ischemic stroke. METHODS: We tested the efficacy of acute (1.5 hours) or delayed (1-3 days) poststroke intravenous injection of hAECs in 4 established animal models of cerebral ischemia. Animals included young (7-14 weeks) and aged mice (20-22 months) of both sexes, as well as adult marmosets of either sex. RESULTS: We found that hAECs administered 1.5 hours after stroke in mice migrated to the ischemic brain via a CXC chemokine receptor type 4-dependent mechanism and reduced brain inflammation, infarct development, and functional deficits. Furthermore, if hAECs administration was delayed until 1 or 3 days poststroke, long-term functional recovery was still augmented in young and aged mice of both sexes. We also showed proof-of-principle evidence in marmosets that acute intravenous injection of hAECs prevented infarct development from day 1 to day 10 after stroke. CONCLUSIONS: Systemic poststroke administration of hAECs elicits marked neuroprotection and facilitates mechanisms of repair and recovery.

Positive effects of intermittent fasting in ischemic stroke.

Intermittent fasting (IF) is a dietary protocol where energy restriction is induced by alternate periods of ad libitum feeding and fasting. Prophylactic intermittent fasting has been shown to extend lifespan and attenuate the progress and severity of age-related diseases such as cardiovascular (e.g. stroke and myocardial infarction), neurodegenerative (e.g. Alzheimer's disease and Parkinson's disease) and cancerous diseases in animal models. Stroke is the second leading cause of death, and lifestyle risk factors such as obesity and physical inactivity have been associated with elevated risks of stroke in humans. Recent studies have shown that prophylactic IF may mitigate tissue damage and neurological deficit following ischemic stroke by a mechanism(s) involving suppression of excitotoxicity, oxidative stress, inflammation and cell death pathways in animal stroke models. This review summarizes data supporting the potential hormesis mechanisms of prophylactic IF in animal models, and with a focus on findings from animal studies of prophylactic IF in stroke in our laboratory.