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BACE1 regulates expression of Clusterin in astrocytes for enhancing clearance of β-amyloid peptides

ABSTRACT: BACE1 role in reactive astrocytes are unknown. We used single cell RNA sequencing (scRNA-seq) to analyze reactive astrocytes in mice with and without germline Bace1. We also examine reactive astrocytes in the case of adult Bace1 conditional knockout on a 5xFAD Alzheimer's disease mouse model.

ORGANISM(S): Mus musculus

PROVIDER: GSE230116 | GEO | 2023/04/24

REPOSITORIES: GEO

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Project description:Activated brown adipose tissue contributes to control of energy and glucose homeostasis in rodents and humans. Defining cell-autonomous processes underlying BAT differentiation and activation may thus reveal novel therapeutic targets for obesity and type 2 diabetes mellitus intervention. Here we show that ageing- and obesity-associated demises in BAT function coincide with down-regulation of mature microRNAs in BAT in the presence of reduced expression of the critical microRNA processing enzyme Dicer1. To mimic this partial down-regulation of microRNA processing in obesity and ageing, we inactivated one allele of Dicer1 selectively in BAT of mice. BAT- restricted heterozygosity of Dicer1 caused glucose intolerance in lean mice and aggravated diet-induced-obesity (DIO)-evoked deterioration of glucose homeostasis. Using combinatorial analyses of altered microRNA-expression in BAT during in vitro preadipocyte commitment and mouse models of progeria, longevity and DIO, we identified 23 microRNAs dysregulated among these conditions. Of these, we identified miR-328 as a novel regulator of BAT differentiation. miR-328 over-expression promotes BAT-differentiation and impairs muscle progenitor commitment, while reducing miR-328 expression blocks BAT specification. We validated the ß-Secretase Bace1 as a target of miR-328, which is consequently over-expressed in BAT of obese and premature ageing mice. Reducing Bace1 expression enhances brown adipocyte, while impairing myogenic differentiation in vitro. In vivo small-molecule Bace1 inhibition in obese mice delayed DIO-induced weight gain, ameliorated obesity-associated deterioration of glucose metabolism and improved insulin sensitivity. Collectively, these experiments reveal reduced Dicer1-miR-328-Bace1 axis in presence of generalized impairment of microRNA processing in ageing and obesity as a novel determinant of ageing- and obesity-associated decline in BAT function. This may define in vivo Bace1-inhibition as an innovative therapeutic approach to not only target age-related neurodegenerative diseases but at the same time improving age-related impairment of BAT-function and metabolism. C57BL/6 mice ( 4 weeks of age) were treated with a calory-rich, high-sugar high-fat diet (HFD) for a course of 4 weeks. Then groups were stratified and one group continued to receive HFD (BAT13-15) or HFD supplemented with an experimental small-molecule Bace 1 inhibitor (BAT17, 33, 35).

Project description:Alzheimer’s disease (AD) is an unremitting neurodegenerative disorder characterized by cerebral amyloid-β (Aβ) accumulation and gradual decline in cognitive function. Changes in brain energy metabolism arise in the preclinical phase of AD, suggesting an important metabolic component of early AD pathology. Neurons and astrocytes function in close metabolic collaboration, which is essential for the recycling of neurotransmitters in the synapse. However, how this metabolic interplay may be affected during the early stages of AD development has not been sufficiently investigated. Here, we provide an integrative analysis of cellular metabolism during the early stages of Aβ accumulation in the cerebral cortex and hippocampus of the 5xFAD mouse model of AD. Our electrophysiological examination revealed an increase in spontaneous excitatory signaling in hippocampal brain slices of 5xFAD mice. This hyperactive neuronal phenotype coincided with decreased hippocampal TCA cycle metabolism mapped by stable 13C isotope tracing. Particularly, reduced astrocyte TCA cycle activity led to decreased glutamine synthesis, in turn hampering neuronal GABA synthesis in the 5xFAD hippocampus. In contrast, cerebral cortical slices of 5xFAD mice displayed an elevated capacity for oxidative glucose metabolism suggesting a metabolic compensation. When we explored the brain proteome and metabolome of the 5xFAD mice, we found limited changes, supporting that the functional metabolic disturbances between neurons and astrocytes are early events in AD pathology. In addition, we show that synaptic mitochondrial and glycolytic function was impaired selectively in the 5xFAD hippocampus, whereas non-synaptic mitochondrial function was maintained. These findings were supported by ultrastructural analyses demonstrating disruptions in mitochondrial morphology, particularly in the 5xFAD hippocampus. Collectively, our study reveals complex region and cell specific metabolic adaptations, in the early stages of amyloid pathology, which may be fundamental for the progressing synaptic dysfunction in AD.

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BACE1 regulates expression of Clusterin in astrocytes for enhancing clearance of β-amyloid peptides

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