A Study to Estimate How Often Post-stroke Spasticity Occurs and to Provide a Standard Guideline on the Best Way to Monitor Its Development

 You're that blitheringly stupid you think survivors want spasticity monitored; NOT CURED? WOW!

After you are the 1 in 4 per WHO that has a stroke I really hope schadenfreude hits you hard with spasticity. You deserve it.

You haven't followed spasticity research for almost a decade? WOW!

30% get spasticity (30 posts to March 2016)

A Study to Estimate How Often Post-stroke Spasticity Occurs and to Provide a Standard Guideline on the Best Way to Monitor Its Development

ClinicalTrials.gov IDNCT06055725

SponsorIpsen

Information Provided byIpsen Medical Director

Study Start (Actual)2023-11-01

Primary Completion (Estimated) 2027-11-30

Study Completion (Estimated)2027-11-30

Enrollment (Estimated)1051

Study TypeObservational

Last Update Posted2025-12-03

This study will monitor patients during the first year following their stroke. Stroke is a very serious condition where there is a sudden interruption of blood flow in the brain. The main aim of the study will be to find out how many of those who experience their first-ever stroke then go on to develop spasticity that would benefit from treatment with medication. Spasticity is a common post-stroke condition that causes stiff or ridged muscles. The results of this study will provide a standard guideline on the best way to monitor the development of post-stroke spasticity.

To learn more, visitClinicalTrials.gov

Contacts and Locations

Contact Information

Study Contact

NameIpsen Clinical Study Enquiries

PhoneSee e mail

Emailclinical.trials@ipsen.com

Study Contact Backup

NameNot available

PhoneNot available

EmailNot available

United States Locations

California

Anderson, California, United States 92354

Loma Linda

Los Angeles, California, United States 90095

University Of California, Los Angeles Medical Center

Mental imagery after stroke: an exploratory study to investigate the relationship with cognitive and motor performance during rehabilitation

 Why were you so incompetent in NOT CREATING A PROTOCOL ON THIS from all the previous research? Didn't know about previous research? You're fired, regardless!

mental imagery (31 posts to October 2010)

Mental imagery after stroke: an exploratory study to investigate the relationship with cognitive and motor performance during rehabilitation

• Marcella Ottonello, 
• E. N. Aiello, 
• A. Moreschi, 
• E. Torselli, 
• B. Poletti & 
• C. Pistarini 

• 75 Accesses

• Explore all metrics 

Abstract

Introduction

Mental imagery (MI) is a crucial cognitive process involved in planning, memory, and motor skill rehearsal. While MI training has shown promise in stroke rehabilitation, research on MI ability and its impairment in stroke patients, particularly concerning its relationship with cognitive and motor performance, remains limited. This exploratory study aimed to describe MI ability in stroke patients during early rehabilitation and investigate its relationship with cognitive functioning, and to explore if MI can predict motor and cognitive outcomes.

Methods

Thirty sub-acute stroke patients (within three months of onset) were recruited. Participants underwent neuropsychological assessment using the Mental Imagery Test (MIT), Mental Performance in Stroke (MEPS), Frontal Assessment Battery (FAB), Token Test (TT), and Vividness of Visual Imagery Questionnaire (VVIQ). Clinical variables and functional outcomes (Barthel Index at admission and discharge) were also collected. Statistical analyses included univariable associations and multiple linear regression models to assess the impact of MI on MEPS, FAB, and Barthel Index-derived measures (ΔBI, Rehabilitation Efficiency (REy), and Rehabilitation Effectiveness (REs)), controlling for relevant covariates.

Results

The study found a significant positive correlation between MIT scores and overall cognitive performance as measured by MEPS (β = 0.48, t(21) = 2.64,p = .015) and FAB (β = 0.57,t(21) = 3.79,p = .001). This suggests that better MI ability is associated with better general cognitive functioning and executive efficiency in stroke patients. Further analysis revealed that the association with MEPS was primarily driven by visuo-spatial tasks. The presence of unilateral spatial neglect was found to detrimentally affect MIT performance. However, no significant relationship was found between MIT scores and any of the Barthel Index-derived measures of functional independence.

Discussion

These findings indicate a strong link between general mental imagery ability and cognitive functions, particularly visuo-spatial and executive functions, in early-stage stroke rehabilitation. The lack of association with functional motor outcomes suggests that general MI tests might not be sensitive enough to predict physical recovery, possibly due to the distinction between general mental imagery and more specific motor imagery. The study highlights the importance of assessing MI ability, especially considering visuo-spatial and executive functions, before implementing imagery-based rehabilitation protocols. Further research is needed to develop individualised interventions that account for cognitive impairments in stroke patients.

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How a simple salt swap could reduce Aussies’ stroke risk

 Will your incompetent? doctor and hospital know enough to get the dietician to update diet protocols on this?

Do you prefer your doctor, hospital and board of director's incompetence NOT KNOWING? OR NOT DOING?

Of course your competent? doctor told you about the salt controversary years ago, right?

You'll want your competent? doctor to explain all these and give you an EXACT PROTOCOL ON SALT! Noting how much salt your brain needs to function properly! If your doctor doesn't know that, how much else doesn't s/he know? And you're being treated for a brain injury by them?

But this:

 

Review finds no proven clinical benefit to strict salt restriction for patients with heart failure

And this:

In many high income countries, approximately 75% of salt in the diet comes from processed foods and meals prepared outside the home.  So, this China study may not have much relevance in your country.

Intake of potassium- and magnesium-enriched salt improves functional outcome after stroke: a randomized, multicenter, double-blind controlled trial January 2018

Low-Salt Diet Ineffective, Study Finds. Disagreement Abounds. June 2011 

The wrong white crystals: not salt but sugar as aetiological in hypertension and cardiometabolic disease December 2014

Why Everything We Know About Salt May Be Wrong May 2017 

Researchers reveal surprising findings on how salt affects blood flow in the brain

November 2021 

You'll want your competent? doctor to explain these and give you an EXACT PROTOCOL ON SALT!

 

 The latest here:

How a simple salt swap could reduce Aussies’ stroke risk

Aussies have been urged to shake things up in the kitchen and at the dinner table by making a simple swap that could reduce their risk of high blood pressure (hypertension); the leading cause of preventable death in Australia.

A new paper by Australia’s National Hypertension Taskforce recommends substituting regular salt, which is high in sodium, with potassium-enriched salt, saying the switch can significantly reduce high blood pressure and the risk of stroke and heart attacks, particularly for people already living with hypertension.

National Hypertension Taskforce member and Stroke Foundation Chief Executive Officer, Dr Lisa Murphy, says this small change can make a big difference.

“Your traditional Sunday roast or summer barbecue will still taste the same but will be better for your health. Research shows us that high sodium consumption is linked to hypertension so replacing sodium with potassium, an important mineral found in fruit and vegetables, is a simple but effective way to reduce your risk. And to make life easier, you can find potassium-enriched salt at your local supermarket.”

A recent global modelling study on the health effects of switching from regular salt to potassium-enriched salt by The George Institute of Global Health found replacing regular salt with potassium-enriched salt in Australia alone could prevent approximately 500 stroke deaths and 2,000 stroke events each year.

“This recommendation aligns with the latest international guidance from the World Health Organization, the European Society of Cardiology, and the American Heart Association, and has the potential to save thousands of Australian lives,” Dr Murphy said.

High blood pressure affects around one in three Australian adults and remains the leading cause of preventable death and disability nationwide. Excess sodium and insufficient potassium intake are key dietary drivers. Despite the strong evidence supporting the benefits of potassium-enriched salt, it is inconsistently recommended by clinicians and rarely used by patients.

“This is due mostly to clinicians and patients being unaware of the availability, effectiveness and acceptability of potassium-enriched salt and we want to change that,” Dr murphy said.

It is hoped the taskforce’s position, published in the National Journal of Hypertension, paves the way for the recommendations to be adopted more widely and marks an important step forward in the national effort to prevent and control hypertension.

The National Hypertension Taskforce was founded by the Australian Cardiovascular Alliance (ACvA) and Hypertension Australia, with significant support from Stroke Foundation and Heart Foundation as cofounding members. The Taskforce aims to increase the number of Australians with their blood pressure both treated and controlled effectively from 32% to 70% by 2030.

Stroke Weakens How the Brain Integrates Speech Sounds

 What is your doctors' EXACT PROTOCOL to fix this? Oh, nothing like usual? And you're paying them for incompetence? The board of directors incompetently can't tell what competence looks like in their stroke medical 'professionals'!

Stroke Weakens How the Brain Integrates Speech Sounds

Summary: A new study comparing stroke survivors with healthy adults reveals that post-stroke language disorders stem not from slower hearing but from weaker integration of speech sounds. While patients detected sounds as quickly as controls, their brains processed speech features with far less strength, especially when words were unclear.

Healthy listeners extended processing during uncertainty, but stroke survivors did not, suggesting they may abandon sound analysis too early to fully grasp difficult words. The findings highlight neural patterns essential for verbal comprehension and point to faster, story-based diagnostic tools for language impairments.

Key Facts

• Weakened Integration: Stroke survivors process speech sound features with much lower neural strength despite normal sound detection speed.
• Reduced Persistence: When words are unclear, they do not sustain processing long enough to resolve ambiguity.
• Diagnostic Potential: Simple story-listening tasks may replace lengthy behavioral tests for language disorders.

Source: SfN

Following stroke, some people experience a language disorder that hinders their ability to process speech sounds. How do their brains change from stroke? 

Researchers led by Laura Gwilliams, faculty scholar at the Wu Tsai Neuroscience Institute and Stanford Data Science and assistant professor at the Stanford School of Humanities and Sciences, and Maaike Vandermosten, associate professor at the Department of Neurosciences at KU Leuven, compared the brains of 39 patients following stroke and 24 healthy age-matched controls to unveil language processing brain mechanisms.  

Additionally, when there was uncertainty about what words were being said, healthy people processed speech sound features longer compared to those who had experienced a stroke. Credit: Neuroscience News

As reported in their Journal of Neuroscience paper, the researchers recorded brain activity while volunteers listened to a story.

 People with verbal speech processing issues from stroke were not slower to process speech sounds but had much weaker processing than healthy participants.

According to the researchers, this suggests that people with this language disorder can hear sounds of all kinds as well as healthy people but have issues integrating speech sounds to understand language. 

Additionally, when there was uncertainty about what words were being said, healthy people processed speech sound features longer compared to those who had experienced a stroke. 

This could mean that, following stroke, people do not process speech sounds long enough to successfully comprehend words that are difficult to detect. 

This work points to brain activity patterns that may be crucial for understanding verbal language, according to the authors. 

First author Jill Kries expresses excitement about continuing to explore how this simple approach—listening to a story—can be used to improve diagnostics for conditions characterized by language processing issues, which currently involve hours of behavioral tasks.

Key Questions Answered:

Q: Why do some stroke survivors struggle to understand spoken language?

A: Their brains detect sounds normally but integrate speech features with reduced strength, making comprehension harder even when hearing is intact.

Q: What happens when the spoken words are unclear?

A: Healthy listeners process sound features longer to resolve ambiguity, but stroke survivors stop too soon, leading to missed meaning.

Q: How could this research change diagnostics for language disorders?

A: Story-listening brain recordings may provide a quick, naturalistic alternative to hours of behavioral language testing.

Editorial Notes:

• This article was edited by a Neuroscience News editor.
• Journal paper reviewed in full.
• Additional context added by our staff.

About this stroke and speech processing research news

Author: SfN Media
Source: SfN
Contact: SfN Media – SfN
Image: The image is credited to Neuroscience News

Original Research: Closed access.
“The Spatio-Temporal Dynamics of Phoneme Encoding in Aging and Aphasia” by Laura Gwilliams et al. Journal of Neuroscience

Do High-Fat Dairy Products Protect the Brain?

 

Your doctor has informed you of the benefits of dairy fat, right?

 Maybe ask about Grana Padano cheese and see how long your doctor has been incompetent!

Study: Aged Cheese Lowers Blood Pressure September 2019

Eating cheese may offset blood vessel damage from salt Article no longer available so have your doctor find it.

Dairy fat from milk, butter, and cheese could actually PREVENT a heart attack September 2021 

Oh no, your doctor is totally fucking incompetent? And you're paying them?

But a more nuanced analysis here:

A Study Linked Cheese to Lower Dementia Risk. Is That Too Good to Be True?

The latest here:

Do High-Fat Dairy Products Protect the Brain?

A higher intake of high-fat cheese and high-fat cream, but not low-fat dairy products, was associated with a lower risk for dementia, independent of lifestyle factors and overall diet quality, results of a large Swedish population-based study showed.

However, the investigators emphasized that the observational study design does not prove a causal link, and outside experts urged caution in interpreting the findings.

“For decades, the debate over high-fat vs low-fat diets has shaped health advice, sometimes even categorizing cheese as an unhealthy food to limit. Our study found that some high-fat dairy products may actually lower the risk for dementia, challenging some long-held assumptions about fat and brain health,” study investigator Emily Sonestedt, PhD, of Lund University in Lund, Sweden, said in a news release. 

The study was published online on December 17 in Neurology. 

Daytime Naps May Increase Risk for Stroke

 Correlation! Solve the causation problem; NAPS ARE NOT THE PROBLEM! What is causing the naps? 

Daytime Naps May Increase Risk for Stroke

Stroke risk was highest in individuals who took unplanned naps longer than 60 minutes and lowest in those who took planned short naps, indicating that both duration and intention modify vascular risk.

Longer daytime naps are associated with a progressively higher risk for stroke, according to findings published in Sleep Medicine Reviews.

Researchers conducted a systematic review and meta-analysis to assess the relationship between daytime napping and stroke risk. The analysis included 13 quantitative studies, encompassing 15,855 individuals with stroke and 595,520 control individuals. An additional 7 studies were utilized for qualitative review.

Across studies, napping duration was associated with increasing stroke risk. Compared with no napping, naps lasting 1 to 30 minutes were associated with a modestly higher risk for stroke (odds ratio [OR], 1.27; 95% CI, 0.98-1.64), while naps longer than 90 minutes showed the strongest association (OR, 1.79; 95% CI, 1.37-2.35).

When grouped more broadly, naps lasting 60 minutes or less were associated with an OR of 1.27 (95% CI, 1.06-1.51), whereas naps exceeding 60 minutes were linked to a substantially higher risk (OR, 1.86; 95% CI, 1.53-2.27), indicating a progressively increasing association with longer nap duration.

 

The extensive amount of clinical material collected suggests that naps, especially those longer than 60 or 90 min, are risk factors for stroke.

Nap intention also appeared to modify risk. Planned naps lasting 60 minutes or less were associated with a lower risk for stroke (OR, 0.82; 95% CI, 0.70-0.96). In contrast, unplanned naps of similar duration were linked to increased risk (OR, 1.37; 95% CI, 1.10-1.70). Both planned and unplanned naps lasting longer than 60 minutes were associated with elevated risk, with the strongest association observed for unplanned long naps (OR, 2.88; 95% CI, 2.05-4.04), compared with planned long naps (OR, 1.78; 95% CI, 1.14-2.26).

Daytime napping was also associated with increased risk across stroke subtypes. The association was strongest for ischemic stroke (OR, 1.48; 95% CI, 1.05-2.09), followed by hemorrhagic stroke (OR, 1.45; 95% CI, 1.09-1.94), and subarachnoid hemorrhage (OR, 1.44; 95% CI, 1.08–1.92).

Studies that classified napping as present vs absent also showed higher odds of total stroke among individuals who napped (OR, 1.44; 95% CI, 1.27-1.67).

Although differences in study design prevented pooled meta-analysis of nap frequency, several large prospective studies suggested that napping more than twice per week was associated with increased stroke risk, with particularly strong associations among individuals who napped 6 to 7 times per week.

Study limitations included substantial heterogeneity across studies, reliance on self-reported nap characteristics, inconsistent adjustment for confounding variables, and limited availability of detailed sleep-quality measures.

“The extensive amount of clinical material collected suggests that naps, especially those longer than 60 or 90 min, are risk factors for stroke. However, the cause of napping warrants further research and currently appears to be related to night sleep disturbances,” the study authors concluded.

Chronobiology and Neurodegeneration: The Role of Melatonin in Alzheimer's Disease

 

Ask your fuckingly incompetent doctor, hospital and board of directors when EXACTLY THEY ARE GOING TO SOLVE THE MELATONIN CONUMDRUM!

Study links long-term melatonin use to heart problems November 2025

Melatonin: a ferroptosis inhibitor with potential therapeutic efficacy for the post-COVID-19 trajectory of accelerated brain aging and neurodegeneration April 2024

Melatonin enhances neurogenesis and neuroplasticity in long-term recovery following cerebral ischemia in mice March 2025

Melatonin Supplementation in Alzheimer’s disease: The Potential Role in Neurogenesis June 2025

Melatonin May Improve Your Memory, New Study Suggests August 2023

Probably more in all these other melatonin posts.

melatonin (33 posts to February 2012)

Do you prefer your doctor, hospital and board of director's incompetence NOT KNOWING? OR NOT DOING?

Send me personal hate mail on this: oc1dean@gmail.com. I'll print your complete statement with your name(If you can't stand by your name don't bother replying anonymously) and my response in my blog. Or are you afraid to engage with my stroke-addled mind? No excuses are allowed! You're medically trained; it should be simple to precisely state EXACTLY WHY you aren't working on 100% recovery protocols with NO EXCUSES!

I take no prisoners in trying to get stroke solved! No knowledge of all of this and you have blithering idiots in charge, how long before you fire all of them? 

The latest here:

Chronobiology and Neurodegeneration: The Role of Melatonin in Alzheimer's Disease

Author links open overlay panel, , , 

https://doi.org/10.1016/j.nupsyc.2025.100001Get rights and content

Under a Creative Commons license

Open access

Highlights

• •
  To our knowledge, this review systematically consolidate evidence on melatonin’s role across all major hallmarks of AD, amyloid-β neurotoxicity, production and protection, followed by its effects on tau hyperphosphorylation, mitochondrial functional dynamics, oxidative stress, calcium hypothesis, cholinergic hypothesis, neuroinflammation, blood brain barrier maintenance, insulin dynamics, circadian rhythms and concludes with its clinical and translational implications.
• •
  The review advances the current understanding of melatonin as a pleiotropic molecule by positioning it within a multi-target therapeutic framework, in contrast to the reductionist focus of most existing literature on isolated mechanisms.
• •
  Our review uniquely emphasizes melatonin’s role in modulating insulin metabolism and circadian rhythm regulation—two increasingly recognized yet underexplored contributors to AD pathogenesis.
• •
  We bridge preclinical and clinical insights, offering a translational perspective that underscores melatonin’s potential as an adjunctive or preventive strategy in AD management.
• •
  Despite abundant studies on melatonin’s individual effects, no existing review has synthesized its actions in a unified, cross-pathological context. This review fills a significant gap by providing a holistic view of melatonin’s therapeutic promise in AD.

Abstract

Melatonin, a hormone synthesized endogenously in the brain, exhibits a decline with advancing age and is found at reduced levels in individuals with AD. Clinical studies suggest that melatonin supplementation can enhance sleep quality, alleviate sundowning symptoms, and potentially delay the progression of cognitive deterioration in AD patients. While the precise molecular mechanisms remain under investigation, it is hypothesized that melatonin modulates the activity of various protein kinases and phosphatases involved in tau regulation. In this review, we elucidate melatonin’s capacity to mitigate Aβ-induced neurotoxicity, suppress excessive microglial activation, inhibit tau protein hyperphosphorylation, and regulate insulin signaling. Additionally, melatonin contributes to reducing oxidative stress, preserving the integrity of the blood–brain barrier, supporting mitochondrial function, attenuating neuroinflammatory responses, maintaining cholinergic neurotransmission, and regulating intracellular calcium homeostasis. Thus in the current review, we aim to highlight the importance of melatonin’s therapeutic potential as a multi-targeted agent in both the prevention and treatment of AD.

Introduction

Alzheimer’s disease (AD) is a severe life threatening, chronic age-related neurodegenerative disease (Lin et al., 2013) and a leading cause of dementia affecting more than 55 million people on a global basis (Gale et al., 2018). Pathological hallmarks of AD are characterized by the formation and accumulation of extracellular senile plaques (SPs) composed of β-amyloid (Aβ) and neurofibrillary tangles (NFTs) present intracellularly, which are made up of abnormal hyperphosphorylated tau, a protein of microtubule family (Scheltens et al., 2021). Despite the tremendous amounts of research, the etiology of AD alongside it’s molecular players have not yet been fully discovered. However, studies have pointed at a few known mechanisms that contribute to AD pathophysiology, that includes genetic predisposition (for e.g. expression levels of Apolipoproteins (APOE4) and presenilins (PS) genes like PSEN1 and PSEN2), inflammation, oxidative stress, mitochondrial dysfunction, neurotoxicity by neurotoxicants and environmental factors (Lane et al., 2018).

Table 1. Summary Table highlighting the effect of melatonin on each of the pathophysiological outcome of AD

Sr. No	Pathophysiology	Effect of Melatonin	Mechanisms	Limitations
1	Aβ neurotoxicity & production/clearance balance	Lowers brain oligomeric Aβ, shifts Aβ toward soluble/peripheral pools, reduces Aβ-induced toxicity (preclinical).	Inhibits β/γ-secretase activity, promotes clearance, reduces oxidative stress and aggregation.	Mostly animal data with supraphysiological doses; indirect clearance measures; unclear preventive vs therapeutic timing.
2	Mechanisms of melatonin-mediated neuroprotection against Aβ	Reduces synaptic loss and cell death, preserves cognition in Aβ-exposed models.	Antioxidant, anti-apoptotic, inhibition of Aβ oligomerization, MT1/MT2 and SIRT1 pathways.	Pleiotropic actions obscure primary mechanism; limited causal blockade experiments.
3	Tau pathology	Decreases tau hyperphosphorylation and aggregation in vitro and in vivo.	Modulates kinases (↓GSK3β, ↓CDK5) and phosphatases; reduces oxidative stress.	Limited chronic models; unclear receptor dependence; few human data.
4	Circadian–metabolic bridge: melatonin & insulin	Improves insulin signaling, rescues hippocampal insulin resistance in metabolic and STZ models.	Enhances IRS/Akt phosphorylation, reduces inflammation and oxidative stress; aligns metabolic rhythms.	Species differences; pharmacologic doses; unclear central vs peripheral effects.
5	Oxidative stress	Reduces ROS, lipid peroxidation and oxidative damage markers across models.	Free-radical scavenging; upregulates Nrf2 and antioxidant enzymes; stabilizes mitochondria.	High doses used; difficulty separating direct from secondary effects.
6	Chronoprotective role (circadian regulation)	Restores sleep–wake cycles and clock gene expression; improves sleep quality.	Activates MT1/MT2 receptors, phase-shifts clock, synchronizes peripheral/central rhythms.	Heterogeneous dosing/timing; species differences; reduced efficacy in advanced disease.
7	BBB stability	Preserves tight junction proteins, reduces BBB permeability and MMP activity.	Anti-inflammatory (↓NF-κB/TLR4), MMP-9 inhibition, antioxidant protection, AMPK activation.	Acute models dominate; chronic AD-related BBB dysfunction underexplored.
8	Mitochondrial protection	Improves mitochondrial respiration, reduces ROS, prevents mPTP opening.	Activates SIRT1/PGC-1α, stabilizes membrane potential, inhibits cytochrome c release.	In vivo mitochondrial data limited; unclear direct vs secondary effects.
9	Neuroinflammation	Attenuates microglial/astrocytic activation and lowers pro-inflammatory cytokines.	Suppresses NF-κB/TLR4 signaling, decreases iNOS/COX2, promotes anti-inflammatory phenotype.	Acute LPS/toxin models; limited translational biomarkers or human data.
10	Cholinergic hypothesis	Restores ACh levels, reduces AChE activity, protects cholinergic neurons.	Reduces oxidative stress, preserves choline acetyltransferase, indirect anti-inflammatory effects.	Sparse mechanistic data; inconsistent cognitive effects clinically.
11	Calcium hypothesis	Stabilizes intracellular Ca2+, reduces Ca2+-mediated toxicity in neurons.	Modulates NMDA receptor activity, supports mitochondrial Ca2+ buffering.	Mostly in vitro data; chronic Ca2+ dysregulation in AD not fully modeled.

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Melatonin (N-acetyl-5-methoxytryptamine), a key hormone produced by pineal gland is a tryptophan metabolite, which exerts its role in a varied range of physiological functions such as regulation of the circadian rhythms, maintaining sleep-wake cycle, managing oxidative stress levels, immunological aspects and clearance of free radicals(Prodhan et al., 2021). The production of melatonin, is done through a series of enzymatic reactions in pineal gland that involves other metabolites such as serotonin, N-acetyl serotonin and 5-hydroxytryptophan. Melatonin, an endocrine hormone with amphiphilic properties are secreted directly into the bloodstream at night by pineal gland, thereby affecting both central nervous system(CNS) and peripheral nervous system(PNS) organs(Claustrat & Leston, 2015). Human research studies have shown that pineal gland can also release melatonin directly into brain ventricles (Leston et al., 2010). From the bloodstream, melatonin is directly taken up by the liver, where it is converted to 6-hydroxymelatonin sulfate, via a series of enzymatic reactions, and lastly excreted through urine (Bojkowski et al., 1987).

Melatonin primarily influences the target cells by binding to two of the G-protein coupled receptors namely melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2) (de Lima Menezes et al., 2024). Melatonin receptor 3 (MT3) is involved in events that exercises protection due to oxidative stress (de Lima Menezes et al., 2024). The localisation of MT1 and MT2 is not homogenous. MT1 is found in various organs and tissues such as superior chiasmatic nucleus (SCN), ovary, cerebellum, testis, kidney, liver etc. whereas MT2 is more restricted towards brain and partly found in liver and heart tissues (Dubocovich & Markowska, 2005). Activation of MT1 and MT2 receptors lead to the initiation of various signalling pathways, one of which includes the inhibition of adenylate cyclase, which produces cyclone adenosine monophosphate (cAMP), a secondary messenger crucial for cellular and physiological processes (Ahmad et al., 2023). Moreover, melatonin extends its biological activities such as interaction with nuclear receptors and membrane bound intracellular proteins such as calmodulin (Cecon et al., 2018).

Role of Melatonin in Alzheimer’s Disease

Apart from regulating the sleep-wake cycles, and maintain the circadian rhythms melatonin implicates direct and indirect association with pathways involved in AD pathophysiology (Arendt & Skene, 2005). This includes the potential of melatonin to reduce the production of Aβ plaques, alongside exercising it’s protective effect on the Aβ oligomers, which are the most deadly and pathogenic form of Aβ. Melatonin also have been partially found to be involved in modulation of hyperphosphosphorylation of tau (Cline et al., 2018a). Moreoever, melatonin exerts it’s neuroprotective effect by reducing the oxidative stress levels, and promoting the clearance of free radicals in the CNS (D. Xu et al., 2020). Additionally melatonin implicates its effects on circadian processes of brain cells, organizes neural activity, modulates synaptic transmission activity in regard to natural sleep wake cycle, which could potentially alleviate the pathological symptoms of AD (Kruk et al., 2021). Melatonin may influence AD pathology through several additional protective mechanisms, including improved blood-brain barrier (BBB) function, increased removal of metabolites and protein fragments associated with AD; a process largely driven by astrocytes during sleep and enhanced insulin signalling, which is also thought to contribute to AD (De Felice et al., 2022a).

The production of melatonin decreases as the human brain ages, due to the age-related calcification process of pineal gland rather than it’s increased clearance ability (Sack et al., 1986). Clinically speaking, reduced melatonin levels, and disturbed 24-hour melatonin rhythmic cycles are common symptoms observed in patients with dementia and AD (J. L. Wang et al., 2015). Decreased melatonin levels in serum and cerebrospinal fluid (CSF), and disturbed melatonin diurnal rhythm are observed in AD patients (J.-N. Zhou et al., 2003a). Moreoever, CSF melatonin levels decreases significantly as AD progresses pathologically, whose severity is determined by braak stages (R. Y. Liu et al., 1999a). Reduced melatonin levels, are also a key characteristic of preclinical subjects of AD, who are intact cognitively but show early signs of AD thereby regarding it as an important biomarker for the identification of early-onset alzheimer’s disease(EOAD) (Y.-H. Wu et al., 2003). Although molecular alterations occur in the pineal gland of AD patients, there are no observed differences in pineal gland’s weight, degree of calcification, or overall protein content (Friedland et al., 1990). It has also been found that β1-adrenergic receptor mRNA is absent and both the activity and gene expression of monoamine oxidase (MAO) are increased in AD patients. This indicates that disrupted noradrenergic signalling and decreased serotonin, the precursor to melatonin, which might be the cause of melatonin rhythm loss and decreased melatonin levels observed in AD (Y.-H. Wu et al., 2007). External melatonin supplementation, has been suggested as a treatment option for AD patients, which mitigates the effects of agitated behaviour, confusion and “sundowning” symptoms and improves cognitive functioning of AD patients (Cardinali et al., 2002). Thus, this makes melatonin supplementation, which is very less toxic and hideous towards normal functioning of AD patients, a possible symptomatic treatment option.

Since melatonin can alleviate certain clinical symptoms of AD and its levels significantly decline during the progression of the condition, exploring the connection between melatonin and AD pathology may offer valuable insights into its potential for prevention or treatment. This review will focus on melatonin's role in Aβ toxicity, tau hyperphosphorylation, mitochondrial dysfunction, oxidative stress, calcium imbalance, cholinergic system dysregulation, neuroinflammatory microglial activity responses, BBB, insulin resistance and role in regulating circadian rhythms. Each section will cover observations, evidence, mechanism, and theoretical interpretations in a structure pattern.

Melatonin and its potential roles in Aβ neurotoxicity and production/clearance balance

Cleavage of amyloid precursor protein (APP) by β- and γ-secretases leads to the production of Aβ. The production of Aβ fragments follows two classical pathways in AD pathogenesis: amyloidogenic and non-amyloidogenic pathway(Ma et al., 2022). Amyloidogenic processing pathway is initiated when the APP is cleaved by β-secretases in order to form a C-terminal fragment (CTF) with 99 amino acids (C99). C99 is later cleaved by γ-secretases to produce pathogenic forms of Aβ. This amyloidogenic pathway produces neurotoxic fragments like Aβ1− 40 and Aβ1− 42 (Armstrong, 2013). Majority of APP undergoes the non-amyloidogenic pathway first, in which APP is cleaved by α-secretases, which further forms a N- terminal soluble APP- α and C-terminal fragment of 83 amino acids knows as C83. Further C83 is cleaved by γ-secretases to release APP intracellular domain (AICD) (Bruno et al., 2021). Increased levels of non-amyloidogenic pathway processing leads to reduction in production of Aβ and ameliorates the effects mediated by AD pathology (Rostagno, 2022).

A. Evidence

Increased production of Aβ and impaired clearance of Aβ, leads to the assembly and accumulation of Aβ, later on which leads to formation of toxic forms of Aβ, called as oligomeric Aβ and amyloid fibrils. Hence inhibition of this Aβ fibril formation and accumulation is another intervention to stop AD pathogenesis(Rostagno, 2022). Various research studies have shown that melatonin has the ability to slow down or diminish the Aβ production and improper accumulation, by enhancing the non-amyloidogenic APP processing pathway (Minich et al., 2022). Additionally when not comparing with previous conventional models of Aβ plaque formation, melatonin interacts with several biological pathways. For instance, melatonin has been shown to promote α-secretase cleavage of βAPP in both neuronal and non-neuronal cultured cells by increasing the expression of the non-amyloidogenic proteases ADAM10 and ADAM17. Conversely, when α-secretase inhibitors are present in these cell lines, melatonin's ability to activate the non-amyloidogenic pathway through α-secretase is blocked(Shukla et al., 2015). Research using SH-SY5Y cells, a well-established model for investigating neurodegeneration, has shown that melatonin suppresses the expression of amyloidogenic β-secretases(Panmanee et al., 2015). Melatonin treatment appears to reduce the levels of Aβ in the brains of both sporadic and transgenic animal models of AD(Ng et al., 2010). This effect may be due to its ability to simultaneously enhance α-secretase activity, an enzyme that promotes non-amyloidogenic processing of amyloid precursor protein and reduce β-secretase activity, which is involved in Aβ generation. Interestingly, this interaction seems to be bi-directional: studies have shown that Aβ peptides can significantly suppress melatonin production by the pineal gland(Cecon et al., 2015), suggesting a feedback loop that may further influence disease progression.

B. Mechanism

Melatonin appears to regulate the activity of enzymes involved in the processing of membrane-bound APP) in neurons, notably glycogen synthase kinase-3β (GSK3β) (Uemura et al., 2007). GSK3β, a serine/threonine kinase abundantly expressed in the brain, plays a pivotal role in AD pathology by increasing β-secretase activity while simultaneously suppressing α-secretase activity(Ly et al., 2013a). This enzymatic imbalance favors the accumulation of Aβ peptides both inside and outside neurons. In AD mouse models, melatonin has been found to inhibit GSK3β activity, potentially through activation of the MT1 melatonin receptor, as demonstrated in studies using SH-SY5Y neuroblastoma cells(Nopparat et al., 2022a). Notably, under hyperglycemic conditions simulated by high glucose exposure, these cells showed impaired glucose sensing, which activated the pAkt/GSK3β signalling cascade. This activation led to increased expression of BACE (β-secretase) and elevated production of the Aβ42 peptide, further contributing to amyloid pathology(Nopparat et al., 2022a). This effect was mitigated when cells were pretreated with melatonin. Additionally, melatonin might influence the clearance of amyloid-beta by modulating the insulin-degrading enzyme (IDE), a key protease responsible for degrading Aβ both inside and outside cells(Kurochkin et al., 2018). In diabetic mouse models, IDE levels are reduced alongside heightened GSK3β activity in the CNS(Jolivalt et al., 2008). Notably, a synthesized compound combining melatonin and the metal chelator trientine, referred to as melatonin-trientine was found to increase IDE expression, reduce Aβ buildup, and prevent neuronal degeneration in the brains of APP/Presenilin 1 mice(Li et al., 2022).

Another way melatonin exerts its anti-amyloidogenic effects is by promoting the removal of Aβ from the brain. Astrocytes, located at the boundary between brain tissue and the perivascular space which contains capillaries, larger arteries, and veins are involved in clearing Aβ through processes such as enzymatic breakdown and by increasing the activity of efflux transporters for Aβ at the blood-brain barrier (Bechmann et al., 2007). Research using mouse neuroblastoma cells (Neuro-2a) indicates that melatonin may enhance the expression of Transcription Factor EB, a key regulator of lysosome formation. This, in turn, facilitates the clearance of Aβ by astrocytes through the autophagosome-lysosome pathway (Thal, 2012).

Studies have proved that melatonin upregulates the expression of low-density lipoprotein receptor-related protein 1 (LRP1), which is a key receptor involved in transporting Aβ across the BBB and mediating its uptake by astrocytes enhances the clearance of Aβ (Promyo et al., 2020a). Apolipoprotein E (ApoE),a protein involved in lipid transport via cell surface receptors can possibly interfere with this process. ApoE competes with Aβ for LRP1-mediated uptake, and hence hinders the process of Aβ clearance, thereby contributing towards its accumulation and plaque formation in the brain(Hatters et al., 2006). Research in the past decades have depicted that, in astrocytes derived from transgenic AD mouse models that overexpress ApoE, melatonin has been found to counteract ApoE's pro-aggregation effects on Aβ(Verghese et al., 2013). Clinical studies have reported that individuals who have the high-risk APOE4/4 genotype do exhibit lower melatonin levels in cerebrospinal fluid that are at a level that is close to half what individuals carrying just one APOE4 allele have, suggesting such individuals may gain benefit from melatonin supplementation(R. Y. Liu et al., 1999b; Poeggeler et al., 2001).

There are several clinical models established which extensively elucidate melatonin’s role in Aβ neurotoxicity and production/clearance mechanisms. Besides helping the brain’s support cells (astrocytes) clear out waste, melatonin might also ease the buildup of Aβ by boosting the brain’s lymphatic drainage system. In a mouse model of AD (Tg2576), which has a gene mutation causing excess Aβ in the brain, melatonin treatment seemed to shift more Aβ to the lymph nodes in the neck and armpits, while Aβ levels in the brain showed signs of decreasing. Studies conducted by (O’Neal-Moffitt et al., 2015a) illustrates how melatonin reduces Aβ production, by interfering with amyloid fibril formation, and thereby decreasing Aβ deposition in transgenic mouse brains; whereas chronic supplementation improved spatial memory in APP/PS1 mice.

Preclinical evidence across diverse animal models including transgenic APP/PS1 and Tg2576 mice, senescence-accelerated SAMP8 mice, and Aβ-infused or toxin-induced rats consistently demonstrates that melatonin mitigates amyloid-β neurotoxicity(O’Neal-Moffitt et al., 2015a). It inhibits amylodgenesis, prevents fibril aggregation, restores mitochondrial and antioxidant defenses, and improves cognition(Dragicevic et al., 2011a; Matsubara, Bryant-Thomas, et al., 2003; Olcese et al., 2009). These findings collectively support melatonin’s multifaceted neuroprotective potential against the amyloidogenic cascade of AD.

C. Limitations

Despite substantial preclinical evidence supporting melatonin’s neuroprotective actions against amyloid-β toxicity, several factors limit its direct translation to human studies. These include the use of excessively high doses, simplified or incomplete AD models, insufficient attention to circadian timing and sex differences, and interventions initiated before significant disease manifestation. In addition, inconsistencies in experimental protocols and potential publication bias hinder reproducibility and clinical relevance. Overcoming these challenges through standardized methodologies, use of aged and multifactorial animal models, and incorporation of chronopharmacological approaches will be essential to translate preclinical findings into meaningful clinical outcomes.

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