Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hep...Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hepatic ApoE expression(ΔApoE),24-month-oldΔApoE mice displayed a 95%reduction in circulating ApoE levels and significantly improved fracture healing.ApoE treatment of aged BMSCs inhibited osteoblast differentiation in tissue culture models;RNA-seq,Western blot,immunofluorescence,and RT-PCR analyses indicated that the Wnt/β-catenin pathway is the target of this inhibition.Indeed,we showed that ApoE had no effect on cultures with stabilizedβ-catenin levels.Next,we determined that Lrp4 serves as the osteoblast cell surface receptor to ApoE,as expression of Lrp4 is required in ApoE-based inhibition of Wnt/β-catenin signaling and osteoblast differentiation.Importantly,we validated this ApoE-Lrp4-Wnt/β-catenin molecular mechanism in human osteoblast differentiation.Finally,we identified an ApoE-neutralizing antibody(NAb)and used it to treat aged,wildtype mice 3 days after fracture surgery resulting in fracture calluses with 35%more bone deposition.Our work here identifies novel liver-to-bone cross-talk and a noninvasive,translatable therapeutic intervention for aged bone regeneration.展开更多
Complex genetic relationships between neurodegenerative disorders and neuropsychiatric symptoms have been shown, suggesting shared pathogenic mechanisms and emphasizing the potential for developing common therapeutic ...Complex genetic relationships between neurodegenerative disorders and neuropsychiatric symptoms have been shown, suggesting shared pathogenic mechanisms and emphasizing the potential for developing common therapeutic targets. Apolipoprotein E(APOE) genotypes and their corresponding protein(Apo E) isoforms may influence the biophysical properties of the cell membrane lipid bilayer. However, the role of APOE in central nervous system pathophysiology extended beyond its lipid transport function. In the present review article, we analyzed the links existing between APOE genotypes and the neurobiology of neuropsychiatric symptoms in neurodegenerative and vascular diseases. APOE genotypes(APOE ε2, APOE ε3, and APOE ε4) were implicated in common mechanisms underlying a wide spectrum of neurodegenerative diseases, including sporadic Alzheimer's disease, synucleinopathies such as Parkinson's disease and Lewy body disease, stroke, and traumatic brain injury. These shared pathways often involved neuroinflammation, abnormal protein accumulation, or responses to acute detrimental events. Across these conditions, APOE variants are believed to contribute to the modulation of inflammatory responses, the regulation of amyloid and tau pathology, as well as the clearance of proteins such as α-synuclein. The bidirectional interactions among Apo E, amyloid and mitochondrial metabolism, immunomodulatory effects, neuronal repair, and remodeling underscored the complexity of Apo E's role in neuropsychiatric symptoms associated with these conditions since from early phases of cognitive impairment such as mild cognitive impairment and mild behavioral impairment. Besides Apo E-specific isoforms' link to increased neuropsychiatric symptoms in Alzheimer's disease(depression, psychosis, aberrant motor behaviors, and anxiety, not apathy), the APOE ε4 genotype was also considered a significant genetic risk factor for Lewy body disease and its worse cognitive outcomes. Conversely, the APOE ε2 variant has been observed not to exert a protective effect equally in all neurodegenerative diseases. Specifically, in Lewy body disease, this variant may delay disease onset, paralleling its protective role in Alzheimer's disease, although its role in frontotemporal dementia is uncertain. The APOE ε4 genotype has been associated with adverse cognitive outcomes across other various neurodegenerative conditions. In Parkinson's disease, the APOE ε4 allele significantly impacted cognitive performance, increasing the risk of developing dementia, even in cases of pure synucleinopathies with minimal co-pathology from Alzheimer's disease. Similarly, in traumatic brain injury, recovery rates varied, with APOE ε4 carriers demonstrating a greater risk of poor long-term cognitive outcomes and elevated levels of neuropsychiatric symptoms. Furthermore, APOE ε4 influenced the age of onset and severity of stroke, as well as the likelihood of developing stroke-associated dementia, potentially due to its role in compromising endothelial integrity and promoting blood–brain barrier dysfunction.展开更多
Alzheimer’s disease(AD)is the most common form of dementia,affecting over 50 million people worldwide.This figure is projected to nearly double every 20 years,reaching 82 million by 2030 and 152 million by 2050(Alzhe...Alzheimer’s disease(AD)is the most common form of dementia,affecting over 50 million people worldwide.This figure is projected to nearly double every 20 years,reaching 82 million by 2030 and 152 million by 2050(Alzheimer’s Disease International).The apolipoproteinε4(APOE4)allele is the strongest genetic risk factor for late-onset AD(after age 65 years).Apolipoprotein E,a lipid transporter,exists in three variants:ε2,ε3,andε4.APOEε2(APOE2)is protective against AD,APOEε3(APOE3)is neutral,while APOE4 significantly increases the risk.Individuals with one copy of APOE4 have a 4-fold greater risk of developing AD,and those with two copies face an 8-fold risk compared to non-carriers.Even in cognitively normal individuals,APOE4 carriers exhibit brain metabolic and vascular deficits decades before amyloid-beta(Aβ)plaques and neurofibrillary tau tangles emerge-the hallmark pathologies of AD(Reiman et al.,2001,2005;Thambisetty et al.,2010).Notably,studies have demonstrated reduced glucose uptake,or hypometabolism,in brain regions vulnerable to AD in asymptomatic middle-aged APOE4 carriers,long before clinical symptoms arise(Reiman et al.,2001,2005).展开更多
基金supported by a Borden Scholars awardDuke Claude D.Pepper Older Americans Independence Center Pilot Award(P30AG028716)by the NIH/NIA(R01AG081393)。
文摘Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hepatic ApoE expression(ΔApoE),24-month-oldΔApoE mice displayed a 95%reduction in circulating ApoE levels and significantly improved fracture healing.ApoE treatment of aged BMSCs inhibited osteoblast differentiation in tissue culture models;RNA-seq,Western blot,immunofluorescence,and RT-PCR analyses indicated that the Wnt/β-catenin pathway is the target of this inhibition.Indeed,we showed that ApoE had no effect on cultures with stabilizedβ-catenin levels.Next,we determined that Lrp4 serves as the osteoblast cell surface receptor to ApoE,as expression of Lrp4 is required in ApoE-based inhibition of Wnt/β-catenin signaling and osteoblast differentiation.Importantly,we validated this ApoE-Lrp4-Wnt/β-catenin molecular mechanism in human osteoblast differentiation.Finally,we identified an ApoE-neutralizing antibody(NAb)and used it to treat aged,wildtype mice 3 days after fracture surgery resulting in fracture calluses with 35%more bone deposition.Our work here identifies novel liver-to-bone cross-talk and a noninvasive,translatable therapeutic intervention for aged bone regeneration.
文摘Complex genetic relationships between neurodegenerative disorders and neuropsychiatric symptoms have been shown, suggesting shared pathogenic mechanisms and emphasizing the potential for developing common therapeutic targets. Apolipoprotein E(APOE) genotypes and their corresponding protein(Apo E) isoforms may influence the biophysical properties of the cell membrane lipid bilayer. However, the role of APOE in central nervous system pathophysiology extended beyond its lipid transport function. In the present review article, we analyzed the links existing between APOE genotypes and the neurobiology of neuropsychiatric symptoms in neurodegenerative and vascular diseases. APOE genotypes(APOE ε2, APOE ε3, and APOE ε4) were implicated in common mechanisms underlying a wide spectrum of neurodegenerative diseases, including sporadic Alzheimer's disease, synucleinopathies such as Parkinson's disease and Lewy body disease, stroke, and traumatic brain injury. These shared pathways often involved neuroinflammation, abnormal protein accumulation, or responses to acute detrimental events. Across these conditions, APOE variants are believed to contribute to the modulation of inflammatory responses, the regulation of amyloid and tau pathology, as well as the clearance of proteins such as α-synuclein. The bidirectional interactions among Apo E, amyloid and mitochondrial metabolism, immunomodulatory effects, neuronal repair, and remodeling underscored the complexity of Apo E's role in neuropsychiatric symptoms associated with these conditions since from early phases of cognitive impairment such as mild cognitive impairment and mild behavioral impairment. Besides Apo E-specific isoforms' link to increased neuropsychiatric symptoms in Alzheimer's disease(depression, psychosis, aberrant motor behaviors, and anxiety, not apathy), the APOE ε4 genotype was also considered a significant genetic risk factor for Lewy body disease and its worse cognitive outcomes. Conversely, the APOE ε2 variant has been observed not to exert a protective effect equally in all neurodegenerative diseases. Specifically, in Lewy body disease, this variant may delay disease onset, paralleling its protective role in Alzheimer's disease, although its role in frontotemporal dementia is uncertain. The APOE ε4 genotype has been associated with adverse cognitive outcomes across other various neurodegenerative conditions. In Parkinson's disease, the APOE ε4 allele significantly impacted cognitive performance, increasing the risk of developing dementia, even in cases of pure synucleinopathies with minimal co-pathology from Alzheimer's disease. Similarly, in traumatic brain injury, recovery rates varied, with APOE ε4 carriers demonstrating a greater risk of poor long-term cognitive outcomes and elevated levels of neuropsychiatric symptoms. Furthermore, APOE ε4 influenced the age of onset and severity of stroke, as well as the likelihood of developing stroke-associated dementia, potentially due to its role in compromising endothelial integrity and promoting blood–brain barrier dysfunction.
基金supported by National Institute on Aging(NIH-NIA)R01AG054459(to ALL).
文摘Alzheimer’s disease(AD)is the most common form of dementia,affecting over 50 million people worldwide.This figure is projected to nearly double every 20 years,reaching 82 million by 2030 and 152 million by 2050(Alzheimer’s Disease International).The apolipoproteinε4(APOE4)allele is the strongest genetic risk factor for late-onset AD(after age 65 years).Apolipoprotein E,a lipid transporter,exists in three variants:ε2,ε3,andε4.APOEε2(APOE2)is protective against AD,APOEε3(APOE3)is neutral,while APOE4 significantly increases the risk.Individuals with one copy of APOE4 have a 4-fold greater risk of developing AD,and those with two copies face an 8-fold risk compared to non-carriers.Even in cognitively normal individuals,APOE4 carriers exhibit brain metabolic and vascular deficits decades before amyloid-beta(Aβ)plaques and neurofibrillary tau tangles emerge-the hallmark pathologies of AD(Reiman et al.,2001,2005;Thambisetty et al.,2010).Notably,studies have demonstrated reduced glucose uptake,or hypometabolism,in brain regions vulnerable to AD in asymptomatic middle-aged APOE4 carriers,long before clinical symptoms arise(Reiman et al.,2001,2005).
