The Vital Role of Melatonin and Its Metabolites in the Neuroprotection and Retardation of Brain Aging

Sleep as the Foundation of Brain Health

Sleep is a vital function, taking about one-third of a human lifetime, and is essential for achieving and maintaining brain health. From homeostatic neurophysiology to emotional and procedural memory processing to clearance of brain waste, sleep and circadian alignment remain paramount. Yet modern lifestyles and clinical practice often dismiss sleep, resulting in profound long-term repercussions. This chapter examines the roles of sleep and circadian rhythms in memory consolidation, synaptic plasticity, and clearance of metabolic waste, highlighting recent advances in neuroscience research. We explore how insufficient and disordered sleep-a public health concern-can impair cognition, escalate neurodegenerative risks, and compromise neurovascular integrity, thereby impacting brain health. These findings underscore the need for comprehensive screening for disturbed sleep and targeted interventions in clinical practice. Emerging interventions and AI-driven technologies may allow early detection and personalized and individualized treatments and improve outcomes. Overall, this chapter reaffirms that healthy sleep is indispensable at any level of neurological disease prevention-on par with the role of diet and exercise in cardiovascular health-and represents the foundation of brain health.

Melatonin alleviates ferroptosis triggered by cadmium via regulating ferritinophagy and iron metabolism in spermatogonia

Melatonin (Mel), a classical antioxidant, has the potential to mediate ferroptosis. Cadmium (Cd) poses a substantial threat to the male reproductive system, as it can induce testicular injury by triggering ferroptosis. The study aimed to explore the protective role and mechanism of Mel in Cd-induced ferroptosis in spermatogonia (spg). Our results demonstrated that Cd disrupted the mitochondrial ultrastructure and induced more autophagosomes in spg. Exposure to Cd resulted in a reduction of the mitochondrial membrane potential of the cells. The transcriptomics analysis revealed significant differences in gene expression associated with ferroptosis and autophagy. Mel could reverse the changes caused by Cd in the genes mentioned above. Furthermore, Cd increased cellular iron content and elevated reactive oxygen species levels, which induced oxidative stress in spg. Mel pretreatment reduced iron accumulation and oxidative damage caused by Cd exposure. Additional studies demonstrated that Cd exposure activated NCOA4-mediated ferritinophagy in spg. Mel pretreatment, as anticipated, inhibited the increased the mRNA and protein expression of ATG5, LC3B, and NCOA4 caused by Cd, ameliorated Cd-caused iron overload and oxidative stress, and protected spg from ferroptosis. Our study provides a therapeutic basis for the use of Mel to treat Cd-induced testicular injury.

Molecules in the Serotonin-Melatonin Synthesis Pathway Have Distinct Interactions with Lipid Membranes

The neurotransmitter serotonin is involved in physiological processes such as appetite, sleep, and mood and diseases such as anxiety and depression. Traditionally, the effects of serotonin were thought to be initiated by binding to its target transmembrane receptors. It is also known that serotonin can bind directly to the membrane with high affinity and modulate lipid dynamics, lateral segregation of lipids, vesicular association, and membrane protein activity. We investigated if other small molecules in the serotonin metabolic pathway, some of which are known to be signaling molecules while some others are not, have similar membrane modulating effects. Therefore, we examined serotonin and several of its metabolites: 5-hydroxytryptophan (5-HTP), serotonin, N-acetylserotonin (NAS), and melatonin in model membranes mimicking synaptic membranes. Using 2H NMR spectroscopy of deuterated 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), we observed that all metabolites disorder the synaptic membrane-mimicking model membranes. The largest disordering effect was observed for NAS and the smallest for tryptophan. Using fluorescence correlation spectroscopy, it was found that only NAS promotes vesicular association similar to that of serotonin, while the others did not. Furthermore, we found that the serotonin metabolites differed in their membrane distribution by employing solid state 1H magic angle spinning nuclear Overhauser enhancement spectroscopy (NOESY) experiments in simple POPC membranes. Similar results were obtained in synaptic membrane mimics using molecular dynamics simulations. In conclusion, while the causal correlation between membrane modulation effects and membrane distribution for the serotonin metabolites remains elusive, this study suggests that small-molecule metabolites and drugs can have drastic biological effects mediated through the membrane. The finding that small changes in structure lead to very different membrane modulation and distributions suggests the possibility of developing membrane modulating drugs in the future.

Cognitive Dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-Aetiology and Potential Treatments

Systemic infection and inflammation impair mental function through a combination of altered attention and cognition. Here, we comprehensively review the relevant literature and report personal clinical observations to discuss the relationship between infection, peripheral inflammation, and cerebral and cognitive dysfunction in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Cognitive dysfunction in ME/CFS could result from low-grade persistent inflammation associated with raised pro-inflammatory cytokines. This may be caused by both infectious and non-infectious stimuli and lead to altered regional cerebral blood flow accompanied by disturbed neuronal function. Immune dysregulation that manifests as a subtle immunodeficiency or the autoimmunity targeting of one or more neuronal receptors may also be a contributing factor. Efforts to reduce low-grade systemic inflammation and viral reactivation and to improve mitochondrial energy generation in ME/CFS have the potential to improve cognitive dysfunction in this highly disabling condition.

Tryptophan metabolism-related gene CYP1B1 serves as a shared biomarker for both Parkinson's disease and insomnia

Parkinson's disease (PD) and insomnia are prevalent neurological disorders, with emerging evidence implicating tryptophan (TRP) metabolism in their pathogenesis. However, the precise mechanisms by which TRP metabolism contributes to these conditions remain insufficiently elucidated. This study explores shared tryptophan metabolism-related genes (TMRGs) and molecular mechanisms underlying PD and insomnia, aiming to provide insights into their shared pathogenesis. We analyzed datasets for PD (GSE100054) and insomnia (GSE208668) obtained from the Gene Expression Omnibus (GEO) database. TMRGs were obtained from the Molecular Signatures Database (MSigDB) and the Genecards database. Tryptophan metabolism-related differentially expressed genes (TM-DEGs) were identified by intersecting TMRGs with shared differentially expressed genes (DEGs) from these datasets. Through Protein-Protein Interaction (PPI) network analysis, Support Vector Machine-Recursive Feature Elimination (SVM-RFE) , and Extreme Gradient Boosting (XGBoost) machine learning, we identified Cytochrome P4501B1 (CYP1B1) and Electron Transfer Flavoprotein Alpha (ETFA) as key hub genes. Subsequently, we employed CIBERSORT and single-sample gene set enrichment analysis (ssGSEA) to further investigate the association between hub genes and peripheral immune activation and inflammatory response. Additionally, gene interaction, Drug-mRNA, Transcription Factor (TF)-mRNA, and competing endogenous RNA (ceRNA) networks centered on these hub genes were constructed to explore regulatory mechanisms and potential drug interactions. Finally, validation through bioinformatics and animal experiments identified CYP1B1 as a promising biomarker associated with both PD and insomnia.

Molecular pathways and biological roles of melatonin and vitamin D; effects on immune system and oxidative stress

Melatonin and vitamin D are associated with the immune system and have important functions as antioxidants. Numerous attempts have been made to identify up to date activities of these molecules in various physiological conditions. The biosynthetic pathways of melatonin and vitamin D are correlated to sun exposure in an inverse manner. Vitamin D is biosynthesized when the skin is exposed to the sun's UV radiation, while melatonin synthesis occurs in the pineal gland principally during night. Additionally, vitamin D is particularly associated with intestinal absorption, metabolism, and homeostasis of ions including calcium, magnesium. However, melatonin has biological marks and impacts on the sleep-wake cycle. The roles of vitamin D and melatonin are opposed to each other individually, but either of them is implicated in the immune system. Recently studies have shown that melatonin and vitamin D have their specific set of aberrations in different cell signaling pathways, such as serine/threonine-specific protein kinase (Akt), phosphoinositide 3-kinase (PI3K), nuclear factor-κB (NF-κB), mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK), Wnt/β-catenin, and Notch. The aim of this review is to clarify the common biological functions and molecular mechanisms through which melatonin and vitamin D could deal with different signaling pathways.

Dysfunctional mitochondria in age-related neurodegeneration: Utility of melatonin as an antioxidant treatment

Mitochondria functionally degrade as neurons age. Degenerative changes cause inefficient oxidative phosphorylation (OXPHOS) and elevated electron leakage from the electron transport chain (ETC) promoting increased intramitochondrial generation of damaging reactive oxygen and reactive nitrogen species (ROS and RNS). The associated progressive accumulation of molecular damage causes an increasingly rapid decline in mitochondrial physiology contributing to aging. Melatonin, a multifunctional free radical scavenger and indirect antioxidant, is synthesized in the mitochondrial matrix of neurons. Melatonin reduces electron leakage from the ETC and elevates ATP production; it also detoxifies ROS/RNS and via the SIRT3/FOXO pathway it upregulates activities of superoxide dismutase 2 and glutathione peroxidase. Melatonin also influences glucose processing by neurons. In neurogenerative diseases, neurons often adopt Warburg-type metabolism which excludes pyruvate from the mitochondria causing reduced intramitochondrial acetyl coenzyme A production. Acetyl coenzyme A supports the citric acid cycle and OXPHOS. Additionally, acetyl coenzyme A is a required co-substrate for arylalkylamine-N-acetyl transferase, which rate limits melatonin synthesis; therefore, melatonin production is diminished in cells that experience Warburg-type metabolism making mitochondria more vulnerable to oxidative stress. Moreover, endogenously produced melatonin diminishes during aging, further increasing oxidative damage to mitochondrial components. More normal mitochondrial physiology is preserved in aging neurons with melatonin supplementation.

Sleep and cognitive outcomes in multiple sclerosis; a systematic review

BACKGROUND

Multiple sclerosis (MS) is a disabling disease of the central nervous system. People living with MS often have co-existing sleep disorders and cognitive dysfunction. The objective of this study was to scrutinize the relationship between cognitive outcomes and sleep conditions in MS.

METHODS

This study followed the Joanna Briggs Institute's (JBI) and PRISMA guidelines. PubMed, Scopus, Embase, and Web of Science databases were searched and original studies delineating the relationship between sleep status and cognitive findings in MS patients‌ were included. The risk of bias was assessed using the JBI critical appraisal tools.

RESULTS

In the final review, out of 1635 screened records, 35 studies with 5321 participants were included. Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and polysomnography were the most common assessment tools for evaluation of sleep condition, and cognitive evaluations were conducted using the tests including Paced Auditory Serial Addition Test (PASAT), California Verbal Learning Test (CVLT), Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test (BVMT). Assessing the quality of studies showed no significant bias in most of the included articles. A link between sleep condition and cognitive abilities was suggested in the literature, especially with objective measurement of sleep condition; however, current evidence did not support a substantial association between self-reported sleep quality and processing speed and working memory in patients with MS.

DISCUSSION

Evidence proposes sleep is an independent factor associated with cognitive outcomes in MS. Given the limitations of the evidence such as the lack of well-designed prospective studies, these findings need to be interpreted with caution.

Reversing Aging and Improving Health Span in Glaucoma Patients: The Next Frontier?

How to cite this article: Dada T, Mahalingam K, Bhartiya S. Reversing Aging and Improving Health Span in Glaucoma Patients: The Next Frontier? J Curr Glaucoma Pract 2024;18(3):87-93.