Repurposing Proteostasis-Modifying Drugs to Prevent or Treat Age-Related Dementia: A Systematic Review

Plasma proteomic biomarkers and the association between poor cardiovascular health and incident dementia: The UK Biobank study

BACKGROUND

The study examined how plasma proteome indicators may explain the link between poor cardiovascular health (CVH) and dementia risk.

METHODS

The present study involved 28,974 UK Biobank participants aged 50-74y at baseline (2006-2010) who were followed-up for ≤ 15 y for incidence of dementia. CVH was calculated using Life's Essential 8 (LE8) total scores. The scores were standardized and reverse coded to reflect poor CVH (LE8z_rev). OLINK proteomics was available on this sample (k = 1,463 plasma proteins). The study primarily tested the mediating effects of the plasma proteome in LE8z_rev-dementia effect. The total effect was decomposed into "mediation only" or pure indirect effect (PIE), "interaction only" or interaction referent (INTREF), "neither mediation nor interaction" or controlled direct effect (CDE), and "both mediation and interaction" or mediated interaction (INTMED).

RESULTS

The study found poorer CVH assessed by LE8z_rev increased the risk of all-cause dementia by 11 % [per 1 SD, hazard ratio, (HR) = 1.11, 95 % CI: 1.03-1.20, p = 0.005). The study identified 11 plasma proteins with strong mediating effects, with GDF15 having the strongest association with dementia risk (per 1 SD, HR = 1.24, 95 % CI: 1.16, 1.33, P < 0.001 when LE8z_rev is set at its mean value) and the largest proportion mediated combining PIE and INTMED (62.6 %; 48 % of TE is PIE), followed by adrenomedullin or ADM. A first principal component with 10 top mediators (TNFRSF1A, GDF15, FSTL3, COL6A3, PLAUR, ADM, GFRAL, ACVRL1, TNFRSF6B, TGFA) mediated 53.6 % of the LE8z_rev-dementia effect. Using all the significant PIE (k = 526) proteins, we used OLINK Insight pathway analysis to identify key pathways, which revealed the involvement of the immune system, signal transduction, metabolism, disease, protein metabolism, hemostasis, membrane trafficking, extracellular matrix organization, developmental biology, and gene expression among others. STRING analysis revealed that five top consistent proteomic mediators were represented in two larger clusters reflecting numerous interconnected biological gene ontology pathways, most notably cytokine-mediated signaling pathway for GDF15 cluster (GO:0019221) and regulation of peptidyl-tyrosine phosphorylation for the ADM cluster (GO:0050730).

CONCLUSION

Dementia is linked to poor CVH mediated by GDF15 and ADM among several key proteomic markers which collectively explained ∼ 54 % of the total effect.

Lithium Exposure and Risk of Major Neurocognitive Disorders: A Systematic Review and Meta-analysis

BACKGROUND

Published studies on the association between lithium use and the decreased risk of major neurocognitive disorders (MNCDs) have shown disparities in their conclusions. We aimed to provide updated evidence of this association.

METHODS

A comprehensive literature search was performed in PubMed, EMBASE, and Cochrane Library from inception until August 31, 2023. All the observational studies evaluating the association between lithium use and MNCD risk were eligible for inclusion. Pooled odds ratios (ORs) and 95% prediction intervals were computed using random-effects models.

RESULTS

Eight studies with 377,060 subjects were included in the analysis. In the general population on the association between lithium use versus nonuse and dementia, the OR was 0.94 (95% confidence interval [CI] = 0.77-1.24). Further analysis also demonstrated that lithium use was not associated with an increased risk of Alzheimer's disease (OR = 0.69, 95% CI: 0.31-1.65). When the analysis was restricted to individuals with bipolar disorder to reduce the confounding by clinical indication, lithium exposure was also not associated with a decreased risk of MNCD (OR = 0.9, 95% CI = 0.71-1.15).

CONCLUSION

The results of this systematic review and meta-analysis do not support a significant association between lithium use and the risk of MNCD.

Hospital-treated prevalent infections, the plasma proteome and incident dementia among UK older adults

The plasma proteome can mediate the association of hospital-treated infections with dementia incidence. We screened up to 37,269 UK Biobank participants aged 50-74 years for the presence of a prevalent hospital-treated infection, subsequently tested as a predictor for ≤1,463 plasma proteins and dementia incidence. Four-way decomposition models decomposed infection-dementia total effect into pure mediation, pure interaction, neither or both through the plasma proteome. Hospital-treated infections increased dementia two-fold. The strongest mediation effect was through the growth differentiation factor 15 (GDF15) protein. Top 17 proteomic mediators explained collectively 5% of the total effect, while pathway analysis of all mediators (k = 221 plasma proteins) revealed top pathways including the immune system, signal transduction, metabolism, disease and metabolism of proteins, with the GDF15 cluster reflecting most strongly the "transmembrane receptor protein tyrosine kinase signaling pathway". The association of hospital-treated infections with dementia was partially mediated through GDF15 and other plasma proteomic markers.

Ageing in the brain: mechanisms and rejuvenating strategies

Ageing is characterized by the progressive loss of cellular homeostasis, leading to an overall decline of the organism's fitness. In the brain, ageing is highly associated with cognitive decline and neurodegenerative diseases. With the rise in life expectancy, characterizing the brain ageing process becomes fundamental for developing therapeutic interventions against the increased incidence of age-related neurodegenerative diseases and to aim for an increase in human life span and, more importantly, health span. In this review, we start by introducing the molecular/cellular hallmarks associated with brain ageing and their impact on brain cell populations. Subsequently, we assess emerging evidence on how systemic ageing translates into brain ageing. Finally, we revisit the mainstream and the novel rejuvenating strategies, discussing the most successful ones in delaying brain ageing and related diseases.

Neuromelanin: Its role in the pathogenesis of idiopathic Parkinson's disease and potential as a therapeutic target

Parkinson's disease is an increasingly prevalent condition that involves the marked loss of dopaminergic neurons in the substantia nigra pars compacta. These neurons pigmented with neuromelanin along with other regions of the brain are almost exclusively victims of neurodegeneration in the disease. The link between neuromelanin and Parkinson's disease has been widely studied for decades. While many studies have outlined the pigment's neuroprotective function as a potent free radical scavenger, antioxidant, and ion-chelator, it has also been observed to play a role in cell death due to mitochondrial dysfunction and oxidative stress, especially in the parkinsonian disease state. This is due to the damaging effects of neuromelanin precursors, neuromelanin-related ion dysregulation and intra- and extraneuronal neuromelanin accumulation. Current and emerging therapeutic endeavours guided by these pathological processes may include antioxidant therapy, proteostasis enhancement, ion chelation and neuromelanin-targeted immunotherapy to prevent the accumulation, formation and effects of neuromelanin and oxidative neuromelanin precursors. Some of these therapeutic strategies are already in nascent stages, while others have produced mixed results in clinical trials. This review aims to provide an update on how neuromelanin and neuromelanin-related substances may be linked to the pathogenesis of Parkinson's disease and how future therapeutic strategies may be able to hamper or prevent neuromelanin-related pathological processes and ultimately modify disease progression in Parkinson's.

Meeting Report: Aging Research and Drug Discovery

Aging is the single largest risk factor for most chronic diseases, and thus possesses large socioeconomic interest to continuously aging societies. Consequently, the field of aging research is expanding alongside a growing focus from the industry and investors in aging research. This year’s 8th Annual Aging Research and Drug Discovery (ARDD) meeting was organized as a hybrid meeting from August 30th to September 3rd 2021 with more than 130 attendees participating on-site at the Ceremonial Hall at University of Copenhagen, Denmark, and 1800 engaging online. The conference comprised of presentations from 75 speakers focusing on new research in topics including mechanisms of aging and how these can be modulated as well as the use of AI and new standards of practices within aging research. This year, a longevity workshop was included to build stronger connections with the clinical community.

Proteostasis deregulation as a driver of C9ORF72 pathogenesis

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two related neurodegenerative disorders that display overlapping features. The hexanucleotide repeat expansion GGGGCC (G₄ C₂ ) in C9ORF72 gene has been causally linked to both ALS and FTD emergence, thus opening a novel potential therapeutic target for disease intervention. The main driver of C9ORF72 pathology is the disruption of distinct cellular processes involved in the function of the proteostasis network. Here we discuss main findings relating to the induction of neurodegeneration by C9ORF72 mutation and proteostasis deregulation, highlighting the role of the endoplasmic reticulum stress, nuclear transport, and autophagy in the disease process. We further discuss possible points of intervention to target proteostasis mediators to treat C9ORF72-linked ALS/FTD.

Targeting impaired nutrient sensing with repurposed therapeutics to prevent or treat age-related cognitive decline and dementia: A systematic review

BACKGROUND

Dementia is a debilitating syndrome that significantly impacts individuals over the age of 65 years. There are currently no disease-modifying treatments for dementia. Impairment of nutrient sensing pathways has been implicated in the pathogenesis of dementia, and may offer a novel treatment approach for dementia.

AIMS

This systematic review collates all available evidence for Food and Drug Administration (FDA)-approved therapeutics that modify nutrient sensing in the context of preventing cognitive decline or improving cognition in ageing, mild cognitive impairment (MCI), and dementia populations.

METHODS

PubMed, Embase and Web of Science databases were searched using key search terms focusing on available therapeutics such as 'metformin', 'GLP1', 'insulin' and the dementias including 'Alzheimer's disease' and 'Parkinson's disease'. Articles were screened using Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). The risk of bias was assessed using the Cochrane Risk of Bias tool v 2.0 for human studies and SYRCLE's risk of bias tool for animal studies.

RESULTS

Out of 2619 articles, 114 were included describing 31 different 'modulation of nutrient sensing pathway' therapeutics, 13 of which specifically were utilized in human interventional trials for normal ageing or dementia. Growth hormone secretagogues improved cognitive outcomes in human mild cognitive impairment, and potentially normal ageing populations. In animals, all investigated therapeutic classes exhibited some cognitive benefits in dementia models. While the risk of bias was relatively low in human studies, this risk in animal studies was largely unclear.

CONCLUSIONS

Modulation of nutrient sensing pathway therapeutics, particularly growth hormone secretagogues, have the potential to improve cognitive outcomes. Overall, there is a clear lack of translation from animal models to human populations.

Anti-angiogenic effects of VEGF stimulation on endothelium deficient in phosphoinositide recycling

Anti-angiogenic therapies have generated significant interest for their potential to combat tumor growth. However, tumor overproduction of pro-angiogenic ligands can overcome these therapies, hampering success of this approach. To circumvent this problem, we target the resynthesis of phosphoinositides consumed during intracellular transduction of pro-angiogenic signals in endothelial cells (EC), thus harnessing the tumor’s own production of excess stimulatory ligands to deplete adjacent ECs of the capacity to respond to these signals. Using zebrafish and human endothelial cells in vitro, we show ECs deficient in CDP-diacylglycerol synthase 2 are uniquely sensitive to increased vascular endothelial growth factor (VEGF) stimulation due to a reduced capacity to re-synthesize phosphoinositides, including phosphatidylinositol-(4,5)-bisphosphate (PIP2), resulting in VEGF-exacerbated defects in angiogenesis and angiogenic signaling. Using murine tumor allograft models, we show that systemic or EC specific suppression of phosphoinositide recycling results in reduced tumor growth and tumor angiogenesis. Our results suggest inhibition of phosphoinositide recycling provides a useful anti-angiogenic approach.

Tumors can overproduce pro-angiogenic ligands overcoming currently approved anti-angiogenic therapies and hindering their success. Here, the authors show that targeting phosphoinositide recycling during tumor angiogenesis harnesses the tumor’s own production of angiogenic ligands to deplete adjacent endothelial cells of the capacity to respond to these signals.

Drug synergy as a strategy for compression of morbidity in a Caenorhabditis elegans model of Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide. AD is a multifactorial disease with simultaneous occurrence of several connected pathological processes including mitochondrial dysfunction and impaired proteostasis. Most of these are also implicated in organismal aging per se. The presence of separable pathological conditions poses the opportunity to try combination treatments that target these different processes separately. This approach may provide an effective strategy to target AD; therefore, we investigated whether a combination of metformin (targeting mitochondria and energy metabolism) and lithium (targeting proteostasis) could result in synergistic benefits. In this perspective paper, we looked for benefits in lifespan and healthspan using a transgenic nematode strain, GRU102, which expresses pan-neuronal human amyloid-beta (Aβ). Individually, metformin and lithium extended the lifespan of both non-transgenic GRU101 controls and GRU102. Combination treatment using metformin and lithium did not result in any synergistic increase in GRU102 lifespan, but this treatment did result in a significant compression of morbidity when compared with each individual drug, resulting in relative and absolute extension of healthspan. Despite over-expressing pathogenic human Aβ in their neurons, GRU102 worms treated with the combination treatment enjoyed longer lifespans and significantly compressed morbidity, even compared with untreated non-transgenic animals. These findings suggest combination treatment as a strategy to compress morbidity, and highlight the distinction between healthspan and lifespan.

A Prospective Repurposing of Dantrolene as a Multitarget Agent for Alzheimer's Disease

The orphan drug dantrolene (DAN) is the only therapeutic treatment for malignant hyperthermia (MH), a pharmacogenetic pathology affecting 0.2 over 10,000 people in the EU. It acts by inhibiting ryanodine receptors, which are responsible for calcium recruitment in striatal muscles and brain. Because of its involvement in calcium homeostasis, DAN has been successfully investigated for its potential as neuroprotecting small molecule in several animal models of Alzheimer’s disease (AD). Nevertheless, its effects at a molecular level, namely on putative targets involved in neurodegeneration, are still scarcely known. Herein, we present a prospective study on repurposing of DAN involving, besides the well-known calcium antagonism, inhibition of monoamine oxidase B and acetylcholinesterase, cytoprotection from oxidative insult, and activation of carnitine/acylcarnitine carrier, as concurring biological activities responsible for neuroprotection.

Effects of inhibiting mTOR with rapamycin on behavior, development, neuromuscular physiology and cardiac function in larval Drosophila

Rapamycin and other mTOR inhibitors are being heralded as possible treatments for many human ailments. It is currently being utilized clinically as an immunomodulator after transplantation procedures and as a treatment for certain forms of cancer, but it has numerous potential clinical indications. Some studies have shown profound effects on life cycle and muscle physiology, but these issues have not been addressed in an organism undergoing developmental processes. This paper fills this void by examining the effect of mTOR inhibition by rapamycin on several different qualities of larval Drosophila. Various dosages of the compound were fed to second instar larvae. These larvae were monitored for pupae formation to elucidate possible life cycle effects, and a delay to pupation was quantified. Behavioral deficits were documented in rapamycin-treated larvae. Electrophysiological measurements were taken to discern changes in muscle physiology and synaptic signaling (i.e. resting membrane potential, amplitude of excitatory post-synaptic potentials, synaptic facilitation). Pupation delay and effects on behavior that are likely due to synaptic alterations within the central nervous system were discovered in rapamycin-fed larvae. These results allow for several conclusions as to how mTOR inhibition by rapamycin affects a developing organism. This could eventually allow for a more informed decision when using rapamycin and other mTOR inhibitors to treat human diseases, especially in children and adolescents, to account for known side effects.

Summary: Inhibiting mTOR by rapamycin delays pupation, reduced body wall contractions and mouth-hook movements while synaptic transmission appeared normal in larval Drosophila.

Methylene blue does not bypass Complex III antimycin block in mouse brain mitochondria

Methylene blue (MB) is a promising prodrug to treat mitochondrial dysfunctions that is currently being used in clinical trials for Alzheimer's disease. MB can penetrate the blood brain barrier, accumulating in brain mitochondria where it acts as a redox mediator in the electron transfer chain (ETC). Mitochondrial flavins are thought to reduce MB, which is then oxidized by cytochrome c, thereby bypassing inhibited Complex I of ETC. We found that in mouse brain mitochondria, MB fails to restore the membrane potential and respiration inhibited by antimycin. Furthermore, antimycin inhibits MB-induced H₂ O₂ generation. Our data suggest that the acceptor of electrons from MB is a Qo ubiquinol-binding site of Complex III; thus, MB-based drugs might not be helpful in mitochondrial dysfunctions involving Complex III inhibition.

Precision Medicine for Frontotemporal Dementia

Frontotemporal dementia (FTD) is a common young-onset dementia presenting with heterogeneous and distinct syndromes. It is characterized by progressive deficits in behavior, language, and executive function. The disease may exhibit similar characteristics to many psychiatric disorders owing to its prominent behavioral features. The concept of precision medicine has recently emerged, and it involves neurodegenerative disease treatment that is personalized to match an individual's specific pattern of neuroimaging, neuropathology, and genetic variability. In this paper, the pathophysiology underlying FTD, which is characterized by the selective degeneration of the frontal and temporal cortices, is reviewed. We also discuss recent advancements in FTD research from the perspectives of clinical, imaging, molecular characterizations, and treatment. This review focuses on the approach of precision medicine to manage the clinical and biological complexities of FTD.