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Glutamate recycling between neurons and astrocytes is essential to maintain neurotransmitter homeostasis. Disturbances in glutamate homeostasis, resulting in excitotoxicity and neuronal death, have been described as a potential mechanism in Alzheimer's disease (AD) pathophysiology. However, glutamate neurotransmitter metabolism in different human brain cells, particularly astrocytes, has been poorly investigated at the early stages of AD. We sought to investigate glucose and glutamate metabolism in AD by employing human induced pluripotent stem cell (hiPSC)-derived astrocytes and neurons carrying mutations in the amyloid precursor protein (APP) or presenilin-1 (PSEN-1) gene as found in familial types of AD (fAD). Methods such as livecell bioenergetics and metabolic mapping using [13C]-enriched substrates were used to examine metabolism in the early stages of AD. Our results revealed greater glycolysis and glucose oxidative metabolism in astrocytes and neurons with APP or PSEN-1 mutations, accompanied by an elevated glutamate synthesis compared to control WT cells. Astrocytes with APP or PSEN-1 mutations exhibited reduced expression of the excitatory amino acid transporter 2 (EAAT2), and glutamine uptake increased in mutated neurons, with enhanced glutamate release specifically in neurons with a PSEN-1 mutation. These results demonstrate a hypermetabolic phenotype in astrocytes with fAD mutations possibly linked to toxic glutamate accumulation. Our findings further identify metabolic imbalances that may occur in the early phases of AD pathophysiology. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of polyquaternium‐1 (PQ)‐preserved and benzalkonium chloride (BAK)‐preserved travoprost eye drops on viability of primary human conjunctival goblet cell (GC) cultures and on secretion of mucin and cytokines. Furthermore, to evaluate the physicochemical properties of the branded travoprost eye drop Travatan® and available generics. Methods: The effect of travoprost eye drops was evaluated on GC cultures. Cell viability was assessed through lactate dehydrogenase (LDH) and tetrazolium dye (MTT) colorimetric assays. Mucin secretion was evaluated by immunohistochemical staining. Secretion of interleukin (IL)‐6 and IL‐8 was measured using BD Cytometric Bead Arrays. pH, viscosity, droplet mass, osmolality and surface tension were measured for all included eye drops. Results: In the LDH assay, BAK travoprost caused significant GC loss after 2 hrs of incubation compared to the control. PQ travoprost caused no GC loss at any time point. Both PQ‐ and BAK travoprost caused secretion of mucin to the cytoplasma. No difference in IL‐6 and IL‐8 secretion was identified compared to controls. The pH values for the generics were lower (pH 6.0) than the pH value for Travatan (pH 6.7; p < 0.0001). The viscosity was lowest for Travatan, while the mean droplet mass was higher for Travatan (35 mg) than the generics (28–30 mg; p ≤ 0.0318). The osmolality and surface tension did not differ between the eye drops investigated. Conclusion: BAK travoprost caused GC loss, indicating that PQ preservation may be preferable in treatment of glaucoma. Furthermore, physicochemical properties of branded and generic travoprost eye drops can not be assumed to be identical. [ABSTRACT FROM AUTHOR]

Recent studies indicate a crucial role for neuronal glycogen storage and degradation in memory formation. We have previously identified alpha‐amylase (α‐amylase), a glycogen degradation enzyme, located within synaptic‐like structures in CA1 pyramidal neurons and shown that individuals with a high copy number variation of α‐amylase perform better on the episodic memory test. We reported that neuronal α‐amylase was absent in patients with Alzheimer's disease (AD) and that this loss corresponded to increased AD pathology. In the current study, we verified these findings in a larger patient cohort and determined a similar reduction in α‐amylase immunoreactivity in the molecular layer of hippocampus in AD patients. Next, we demonstrated reduced α‐amylase concentrations in oligomer amyloid beta 42 (Aβ42) stimulated SH‐SY5Y cells and neurons derived from human‐induced pluripotent stem cells (hiPSC) with PSEN1 mutation. Reduction of α‐amylase production and activity, induced by siRNA and α‐amylase inhibitor Tendamistat, respectively, was further shown to enhance glycogen load in SH‐SY5Y cells. Both oligomer Aβ42 stimulated SH‐SY5Y cells and hiPSC neurons with PSEN1 mutation showed, however, reduced load of glycogen. Finally, we demonstrate the presence of α‐amylase within synapses of isolated primary neurons and show that inhibition of α‐amylase activity with Tendamistat alters neuronal activity measured by calcium imaging. In view of these findings, we hypothesize that α‐amylase has a glycogen degrading function within synapses, potentially important in memory formation. Hence, a loss of α‐amylase, which can be induced by Aβ pathology, may in part underlie the disrupted memory formation seen in AD patients. [ABSTRACT FROM AUTHOR]

Aims/Purpose: The aim of the study is to evaluate energy metabolism and retinal tissue survival in retinal explants in a murine model of AD (TgSwDI) during aging. Methods: The 7‐, 12‐ and 24‐month‐old TgSwDI mouse model was compared with age‐matched wild‐type (WT) mice. Characterization of the mouse model was assessed by Aβ plaques staining. Cell viability was evaluated by lactate dehydrogenase (LDH) assay of retinal explants at 4 and 24 h of incubation with culture media. Retinal ganglion cell (RGC) survival was quantified by RBPMS staining in 7‐month‐old mice. Glucose metabolism was analysed by gas chromatography mass spectrometry (GC–MS) using uniformly labelled glucose by incubating whole retinas for 30 min with glucose in 7‐month‐old mice. And lactate, produced by glycolysis, was evaluated by the lactate assay in 7‐month‐old mice. Results: The presence of Aβ plaques and vascularization was detected in the retinas of TgSwDI mice, whereas they were not found in the retinas of control mice. At 7 months, the viability of retinal explants was reduced in the TgSwDI model compared to the age‐matched WT model using the LDH assay. Compared to controls, RGC survival in the TgSwDI model tended to decrease. We performed GC–MS to evaluate glucose metabolism and observed no difference between the TgSwDI and WT groups. Lactate production showed no significant differences between the groups. Conclusions: The presence of Aβ plaques was detected in the retinas of the TgSwDI model, indicating that it is a good model for studying the retina in AD. Retinal tissue viability was altered at different ages in the TgSwDI model, and RGC survival was also reduced in the AD model, substantiating that AD affect the retina. We did not detect any differences between WT and TgSwDI groups in energy metabolism, implying that alterations in retinal tissue and cell survival may be related to other pathways. Further studies are needed to explore this, ultimately providing novel insight to address visual function affected by AD. [ABSTRACT FROM AUTHOR]

* Shared co‐author. Purpose: Previous cerebral studies of Alzheimer's disease (AD) have provided evidence for a neuronal metabolic dysfunction, which precede the cognitive decline. Since the retina is one of the most energy demanding tissues in the body and considered an extension of the brain due to its origin from the neural tissue, we speculate whether dysfunctional energy metabolism is present in AD models. Thus, the aim of the study is to evaluate energy metabolism and tissue survival in retinal explants in a murine model of AD (TgSwDI) during aging. Methods: The 8‐, 12‐, and 24‐month‐old TgSwDI mouse model was compared with age‐matched wild‐type (WT) mice. Tissue survival was assessed by lactate dehydrogenase (LDH) viability assays of retinal explants at 2, 4 and 24 hours of incubation with culture media. Total ATP levels were quantified by bioluminescence assays to assess energy metabolism in TgSwDI mice. Results: Retinal explant survival was reduced in the TgSwDI model compared to the age‐matched WT model with LDH assay at 8 months. The 8‐month‐old AD TgSwDI mice showed a tendency to decrease in total ATP levels after 2 hours of retinal explant incubation (p = 0.07). Conclusions: Retinal tissue survival is impaired in the TgSwDI model during various ages, and tendencies of decreased retinal ATP levels were established at 8 months, implying disrupted retinal energy metabolism similar to changes observed in the AD brain. [ABSTRACT FROM AUTHOR]

Purpose: Visual changes are some of the earliest symptoms that patients with Alzheimer's disease (AD) experience1. Pathophysiological processes such as amyloid‐β plaque formation, vascular changes, neuroinflammation, and loss of retinal ganglion cells (RGCs) have been detected in the retina of AD patients and animal models1. However, little is known about the molecular processes that underlie retinal neurodegeneration in AD. The cellular architecture and constant sensory activity of the retina impose high metabolic demands2. We thus hypothesized that energy metabolism might be compromised in the AD retina similarly to what has been observed in the AD brain3. Methods/ Results: To address this question, we explored cellular alterations and retinal metabolic activity in the 5xFAD mouse model of AD. We used 8‐months old female 5xFAD mice, in which the AD‐related pathology has been shown to be apparent. We observed that RGC density is selectively affected in the retina of 5xFAD mice. To map retinal metabolic activity, we incubated isolated retinal tissue with [U‐13C]glucose and analyzed tissue extracts by gas chromatography‐mass spectrometry. We found that the retinas of 5xFAD mice exhibit glucose hypometabolism. Moreover, we detected decreased glutamine synthesis in 5xFAD retinas but no changes in the expression of markers of Müller glia, the main glial cell type responsible for glutamate uptake and glutamine synthesis in the retina. Conclusions: These findings suggest that AD presents with metabolic alterations not only in the brain but also in the retina that may be detrimental to RGC activity and survival, potentially leading to the visual impairments that AD patients suffer. Chiquita, S. et al. The Retina as a Window or Mirror of the Brain Changes Detected in Alzheimer's Disease: Critical Aspects to Unravel. Molecular Neurobiology vol. 56 5416–5435 (2019).Oesch, N. W., Wade Kothmann, W. & Diamond, J. S. Illuminating synapses and circuitry in the retina. Current Opinion in Neurobiology vol. 21 238–244 (2011).Andersen, J. V. et al. Deficient astrocyte metabolism impairs glutamine synthesis and neurotransmitter homeostasis in a mouse model of Alzheimer's disease. Neurobiol. Dis. 148, (2021). [ABSTRACT FROM AUTHOR]

Purpose: Neurodegenerative retinal diseases are a significant course for blindness. Diseases such as glaucoma, which is the leading course of irreversible blindness in the world, and other inner retinal conditions such as inherited mitochondrial neuropathies are poorly understood. The treatment options for these diseases are often limited and insufficient to prevent blindness. Common for most of these diseases is the loss of the retinal ganglion cells (RGC). Methods: To elucidate the underlying pathological and protective pathways in these inner retinal diseases, respectively, we aim to assess retinal organoids generated from patient‐specific induced pluripotent stem cells (iPSC) and their controls. We have previously established the method of extracting RGCs from our retinal organoids via magnetic‐activated cell sorting (MACS). Results: The subsequent characterization of these RGCs was performed using cell‐specific markers such as CD90, BRN3a and RBPMS via qPCR and immunocytochemistry. Electron microscopy was used to investigate the intracellular organelle conditions of the RGCs. Future experiments are aimed at respiratory capacity analysis, metabolomics, transcriptomics and proteomics of RGCs extracted via MACS from retinal organoids derived from patient iPSCs in hopes of identifying the differences and possibly cellular mechanisms contributing to neurodegenerative retinal diseases in patients compared to healthy controls. Conclusions: This could potentially lead to further understanding of disease mechanisms in patients with inner retinal diseases. In addition, this could establish a diseases model to test new treatment options such as neuroprotective drugs. [ABSTRACT FROM AUTHOR]