Central insulin resistance, the diminished cellular sensitivity to insulin in the brain, has been implicated in diabetes mellitus, Alzheimer’s disease and other neurological disorders. However, whether and how centra...Central insulin resistance, the diminished cellular sensitivity to insulin in the brain, has been implicated in diabetes mellitus, Alzheimer’s disease and other neurological disorders. However, whether and how central insulin resistance plays a role in the eye remains unclear. Here, we performed intracerebroventricular injection of S961, a potent and specific blocker of insulin receptor in adult Wistar rats to test if central insulin resistance leads to pathological changes in ocular structures. 80 mg of S961 was stereotaxically injected into the lateral ventricle of the experimental group twice at 7 days apart, whereas buffer solution was injected to the sham control group. Blood samples, intraocular pressure, trabecular meshwork morphology, ciliary body markers, retinal and optic nerve integrity, and whole genome expression patterns were then evaluated. While neither blood glucose nor serum insulin level was significantly altered in the experimental or control group, we found that injection of S961 but not buffer solution significantly increased intraocular pressure at 14 and 24 days after first injection, along with reduced porosity and aquaporin 4 expression in the trabecular meshwork, and increased tumor necrosis factor α and aquaporin 4 expression in the ciliary body. In the retina, cell density and insulin receptor expression decreased in the retinal ganglion cell layer upon S961 injection. Fundus photography revealed peripapillary atrophy with vascular dysregulation in the experimental group. These retinal changes were accompanied by upregulation of pro-inflammatory and pro-apoptotic genes, downregulation of anti-inflammatory, anti-apoptotic, and neurotrophic genes, as well as dysregulation of genes involved in insulin signaling. Optic nerve histology indicated microglial activation and changes in the expression of glial fibrillary acidic protein, tumor necrosis factor α, and aquaporin 4. Molecular pathway architecture of the retina revealed the three most significant pathways involved being inflammation/cell stress, insulin signaling, and extracellular matrix regulation relevant to neurodegeneration. There was also a multimodal crosstalk between insulin signaling derangement and inflammation-related genes. Taken together, our results indicate that blocking insulin receptor signaling in the central nervous system can lead to trabecular meshwork and ciliary body dysfunction, intraocular pressure elevation, as well as inflammation, glial activation, and apoptosis in the retina and optic nerve. Given that central insulin resistance my lead to neurodegenerative phenotype in the visual system, targeting insulin signaling may hold promise for vision disorders involving the retina and optic nerve.展开更多
Glaucoma, the world's leading cause of irreversible blindness, is a condition for which elevated intraocular pressure is currently the only modifiable risk factor. However, the disorder can continue to progress ev...Glaucoma, the world's leading cause of irreversible blindness, is a condition for which elevated intraocular pressure is currently the only modifiable risk factor. However, the disorder can continue to progress even at reduced intraocular pressure. This indicates additional key factors that contribute to the etiopathogenesis. There has been a growing amount of literature suggesting glaucoma as a neurodegenerative disease of the visual system. However, it remains debatable whether the observed pathophysiological conditions are causes or consequences. This review summarizes recent in vivo imaging studies that helped advance the understanding of early glaucoma involvements and disease progression in the brains of humans and experimental animal models. In particular, we focused on the non-invasive detection of early structural and functional brain changes before substantial clinical visual field loss in glaucoma patients; the eye-brain interactions across disease severity; the metabolic changes occurring in the brain's visual system in glaucoma; and, the widespread brain involvements beyond the visual pathway as well as the potential behavioral relevance. If the mechanisms of glaucomatous brain changes are reliably identified, novel neurotherapeutics that target parameters beyond intraocular pressure lowering can be the promise of the near future, which would lead to reduced prevalence of this irreversible but preventable disease.展开更多
Optic nerve health is essential for proper function of the visual system.However,the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve,such as glaucoma,is not fully understood.Re...Optic nerve health is essential for proper function of the visual system.However,the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve,such as glaucoma,is not fully understood.Recently,it was hypothesized that a lack of proper clearance of neurotoxins contributes to neurodegenerative diseases.The ability to clear metabolic waste is essential for tissue homeostasis in mammals,including humans.While the brain lacks the traditional lymphatic drainage system identified in other anatomical regions,there is growing evidence of a glymphatic system in the central nervous system,which structurally includes the optic nerve.Named to acknowledge the supportive role of astroglial cells,this perivascular fluid drainage system is essential to remove toxic metabolites from the central nervous system.Herein,we review existing literature describing the physiology and dysfunction of the glymphatic system specifically as it relates to the optic nerve.We summarize key imaging studies demonstrating the existence of a glymphatic system in the optic nerves of wild-type rodents,aquaporin 4-null rodents,and humans;glymphatic imaging studies in diseases where the optic nerve is impaired;and current evidence regarding pharmacological and lifestyle interventions that may help promote glymphatic function to improve optic nerve health.We conclude by highlighting future research directions that could be applied to improve imaging detection and guide therapeutic interventions for diseases affecting the optic nerve.展开更多
Blindness provides an unparalleled opportunity to study plasticity of the nervous system in humans.Seminal work in this area examined the often dramatic modifications to the visual cortex that result when visual input...Blindness provides an unparalleled opportunity to study plasticity of the nervous system in humans.Seminal work in this area examined the often dramatic modifications to the visual cortex that result when visual input is completely absent from birth or very early in life（Kupers and Ptito,2014）.More recent studies explored what happens to the visual pathways in the context of acquired blindness.This is particularly relevant as the majority of diseases that cause vision loss occur in the elderly.展开更多
基金supported by a grant from All India Institute of Medical Sciences,New Delhi (to RD and TD)Indian Council of Medical Research,Senior Research Fellowship Grant (3/1/2(24)/oph-2009-NCD-II,to MAF)+1 种基金Feldstein Medical Foundation Research Grant (to KCC)unrestricted fund from Research to Prevent Blindness to NYU Langone Health Department of Ophthalmology (to KCC)。
文摘Central insulin resistance, the diminished cellular sensitivity to insulin in the brain, has been implicated in diabetes mellitus, Alzheimer’s disease and other neurological disorders. However, whether and how central insulin resistance plays a role in the eye remains unclear. Here, we performed intracerebroventricular injection of S961, a potent and specific blocker of insulin receptor in adult Wistar rats to test if central insulin resistance leads to pathological changes in ocular structures. 80 mg of S961 was stereotaxically injected into the lateral ventricle of the experimental group twice at 7 days apart, whereas buffer solution was injected to the sham control group. Blood samples, intraocular pressure, trabecular meshwork morphology, ciliary body markers, retinal and optic nerve integrity, and whole genome expression patterns were then evaluated. While neither blood glucose nor serum insulin level was significantly altered in the experimental or control group, we found that injection of S961 but not buffer solution significantly increased intraocular pressure at 14 and 24 days after first injection, along with reduced porosity and aquaporin 4 expression in the trabecular meshwork, and increased tumor necrosis factor α and aquaporin 4 expression in the ciliary body. In the retina, cell density and insulin receptor expression decreased in the retinal ganglion cell layer upon S961 injection. Fundus photography revealed peripapillary atrophy with vascular dysregulation in the experimental group. These retinal changes were accompanied by upregulation of pro-inflammatory and pro-apoptotic genes, downregulation of anti-inflammatory, anti-apoptotic, and neurotrophic genes, as well as dysregulation of genes involved in insulin signaling. Optic nerve histology indicated microglial activation and changes in the expression of glial fibrillary acidic protein, tumor necrosis factor α, and aquaporin 4. Molecular pathway architecture of the retina revealed the three most significant pathways involved being inflammation/cell stress, insulin signaling, and extracellular matrix regulation relevant to neurodegeneration. There was also a multimodal crosstalk between insulin signaling derangement and inflammation-related genes. Taken together, our results indicate that blocking insulin receptor signaling in the central nervous system can lead to trabecular meshwork and ciliary body dysfunction, intraocular pressure elevation, as well as inflammation, glial activation, and apoptosis in the retina and optic nerve. Given that central insulin resistance my lead to neurodegenerative phenotype in the visual system, targeting insulin signaling may hold promise for vision disorders involving the retina and optic nerve.
基金supported by the National Institutes of Health R01-EY028125(Bethesda,MD,USA)(to KCC)BrightFocus Foundation G2013077 and G2016030(Clarksburg,MD,USA)(to KCC)Research to Prevent Blindness/Stavros Niarchos Foundation International Research Collaborators Award(New York,NY,USA)(to KCC)
文摘Glaucoma, the world's leading cause of irreversible blindness, is a condition for which elevated intraocular pressure is currently the only modifiable risk factor. However, the disorder can continue to progress even at reduced intraocular pressure. This indicates additional key factors that contribute to the etiopathogenesis. There has been a growing amount of literature suggesting glaucoma as a neurodegenerative disease of the visual system. However, it remains debatable whether the observed pathophysiological conditions are causes or consequences. This review summarizes recent in vivo imaging studies that helped advance the understanding of early glaucoma involvements and disease progression in the brains of humans and experimental animal models. In particular, we focused on the non-invasive detection of early structural and functional brain changes before substantial clinical visual field loss in glaucoma patients; the eye-brain interactions across disease severity; the metabolic changes occurring in the brain's visual system in glaucoma; and, the widespread brain involvements beyond the visual pathway as well as the potential behavioral relevance. If the mechanisms of glaucomatous brain changes are reliably identified, novel neurotherapeutics that target parameters beyond intraocular pressure lowering can be the promise of the near future, which would lead to reduced prevalence of this irreversible but preventable disease.
基金supported by National Institutes of Health,No.R01-EY028125Bright Focus Foundation,No.G2019103+2 种基金Feldstein Medical FoundationResearch to Prevent Blindness/Stavros Niarchos Foundation International Research Collaborators Awardan unrestricted grant from Research to Prevent Blindness to NYU Langone Health Department of Ophthalmology(to KCC)。
文摘Optic nerve health is essential for proper function of the visual system.However,the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve,such as glaucoma,is not fully understood.Recently,it was hypothesized that a lack of proper clearance of neurotoxins contributes to neurodegenerative diseases.The ability to clear metabolic waste is essential for tissue homeostasis in mammals,including humans.While the brain lacks the traditional lymphatic drainage system identified in other anatomical regions,there is growing evidence of a glymphatic system in the central nervous system,which structurally includes the optic nerve.Named to acknowledge the supportive role of astroglial cells,this perivascular fluid drainage system is essential to remove toxic metabolites from the central nervous system.Herein,we review existing literature describing the physiology and dysfunction of the glymphatic system specifically as it relates to the optic nerve.We summarize key imaging studies demonstrating the existence of a glymphatic system in the optic nerves of wild-type rodents,aquaporin 4-null rodents,and humans;glymphatic imaging studies in diseases where the optic nerve is impaired;and current evidence regarding pharmacological and lifestyle interventions that may help promote glymphatic function to improve optic nerve health.We conclude by highlighting future research directions that could be applied to improve imaging detection and guide therapeutic interventions for diseases affecting the optic nerve.
基金supported by National Institutes of Health Contracts P30-EY008098 and T32-EY017271-06(BethesdaMD)+14 种基金United States Department of Defense DM090217(ArlingtonVA)Alcon Research Institute Young Investigator Grant(Fort WorthTX)Eye and Ear Foundation(PittsburghPA)Research to Prevent Blindness(New YorkNY)Aging Institute Pilot Seed GrantUniversity of Pittsburgh(PittsburghPA)Postdoctoral Fellowship Program in Ocular Tissue Engineering and Regenerative OphthalmologyLouis J.Fox Center for Vision RestorationUniversity of Pittsburgh and UPMC(PittsburghPA)
文摘Blindness provides an unparalleled opportunity to study plasticity of the nervous system in humans.Seminal work in this area examined the often dramatic modifications to the visual cortex that result when visual input is completely absent from birth or very early in life（Kupers and Ptito,2014）.More recent studies explored what happens to the visual pathways in the context of acquired blindness.This is particularly relevant as the majority of diseases that cause vision loss occur in the elderly.
