The regulatory role of melatonin in skeletal muscle

Melatonin in animal husbandry: functions and applications

Melatonin (N-acetyl-5-methoxytryptamine) is an essential small molecule with diverse biological functions. It plays several key roles, including regulating the secretion of reproductive hormones and the reproductive cycle, enhancing the functionality of reproductive organs, improving the quality of sperm and eggs, and mitigating oxidative stress in the reproductive system. Melatonin effectively inhibits and scavenges excess free radicals while activating the antioxidant enzyme system and reduces the production of inflammatory factors and alleviates tissue damage caused by inflammation by regulating inflammatory pathways. Additionally, melatonin contributes to repairing the intestinal barrier and regulating the gut microbiota, thereby reducing bacterial and toxin permeation. The use of melatonin as an endogenous hormone in animal husbandry has garnered considerable attention because of its positive effects on animal production performance, reproductive outcomes, stress adaptation, disease treatment, and environmental sustainability. This review explores the characteristics and biological functions of melatonin, along with its current applications in animal production. Our findings may serve as a reference for the use of melatonin in animal farming and future developmental directions.

Modulation of neural circuits by melatonin in neurodegenerative and neuropsychiatric disorders

Neurodegenerative and neuropsychiatric disorders are two broad categories of neurological disorders characterized by progressive impairments in movement and cognitive functions within the central and peripheral nervous systems, and have emerged as a significant cause of mortality. Oxidative stress, neuroinflammation, and neurotransmitter imbalances are recognized as prominent pathogenic factors contributing to cognitive deficits and neurobehavioral anomalies. Consequently, preventing neurodegenerative and neuropsychiatric diseases has surfaced as a pivotal challenge in contemporary public health. This review explores the investigation of neurodegenerative and neuropsychiatric disorders using both synthetic and natural bioactive compounds. A central focus lies on melatonin, a neuroregulatory hormone secreted by the pineal gland in response to light-dark cycles. Melatonin, an amphiphilic molecule, assumes multifaceted roles, including scavenging free radicals, modulating energy metabolism, and synchronizing circadian rhythms. Noteworthy for its robust antioxidant and antiapoptotic properties, melatonin exhibits diverse neuroprotective effects. The inherent attributes of melatonin position it as a potential key player in the pathophysiology of neurological disorders. Preclinical and clinical studies have demonstrated melatonin's efficacy in alleviating neuropathological symptoms across neurodegenerative and neuropsychiatric conditions (depression, schizophrenia, bipolar disorder, and autism spectrum disorder). The documented neuroprotective prowess of melatonin introduces novel therapeutic avenues for addressing neurodegenerative and psychiatric disorders. This comprehensive review encompasses many of melatonin's applications in treating diverse brain disorders. Despite the strides made, realizing melatonin's full neuroprotective potential necessitates further rigorous clinical investigations. By unravelling the extended neuroprotective benefits of melatonin, future studies promise to deepen our understanding and augment the therapeutic implications against neurological deficits.

Melatonin supplementation enhances pulmonary rehabilitation outcomes in COPD: a randomized, double-blind, placebo-controlled study

Melatonin (MLT), the main product of the pineal gland, is involved in muscle tissue repair and regeneration, besides several other important physiologic functions. In COPD, MLT administration can improve lung oxidative stress and sleep quality, but its potential effects on the outcomes of pulmonary rehabilitation (PR) have not been previously investigated. A randomized controlled trial was undertaken to test the hypothesis that a combined approach of rehabilitative exercise training and MLT supplementation could maximize functional performance, health status and quality of life in patients with COPD. Thirty-nine individuals with COPD referred to a supervised PR program at the Federal University of Ceara, Brazil, were randomized to receive MLT (3 mg/day; n = 18) or placebo (n = 21). Exercise capacity (6-min walk test - 6MWT), health status (COPD assessment test), and quality of life (airways questionnaire 20) were investigated as primary outcomes. No differences were observed at baseline in demographic, anthropometric and clinical characteristics between MLT and placebo groups. At the end of PR, superiority of the MLT group was demonstrated in improvement in the distance covered in the 6MWT (71 ± 26 vs. 25 ± 36 m; p < 0.01), health status (-11 ± 6 vs. -3 ± 5; p < 0.01), and quality of life (-6.9 ± 3.0 vs. -1.9 ± 2.4; p < 0.01), compared to the placebo group. In conclusion, MLT supplementation during the course of 12 weeks of PR can improve functional capacity, health status and quality of life in patients with COPD. These findings may have significant implications for the management of this condition.

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

Melatonin Improves Skeletal Muscle Structure and Oxidative Phenotype by Regulating Mitochondrial Dynamics and Autophagy in Zücker Diabetic Fatty Rat

Obesity-induced skeletal muscle (SKM) inflexibility is closely linked to mitochondrial dysfunction. The present study aimed to evaluate the effects of melatonin on the red vastus lateralis (RVL) muscle in obese rat models at the molecular and morphological levels. Five-week-old male Zücker diabetic fatty (ZDF) rats and their age-matched lean littermates (ZL) were orally treated either with melatonin (10 mg/kg body weight (BW)/24 h) (M-ZDF and M-ZL) or non-treated (control) (C-ZDF and C-ZL) for 12 weeks. Western blot analysis showed that mitochondrial fission, fusion, and autophagy were altered in the C-ZDF group, accompanied by reduced SIRT1 levels. Furthermore, C-ZDF rats exhibited depleted ATP production and nitro-oxidative stress, as indicated by increased nitrites levels and reduced SOD activity. Western blotting of MyH isoforms demonstrated a significant decrease in both slow and fast oxidative fiber-specific markers expression in the C-ZDF group, concomitant with an increase in the fast glycolytic fiber markers. At the tissue level, marked fiber atrophy, less oxidative fibers, and excessive lipid deposition were noted in the C-ZDF group. Interestingly, melatonin treatment partially restored mitochondrial fission/fusion imbalance in the RVL muscle by enhancing the expression of fission (Fis1 and DRP1) markers and decreasing that of fusion (OPA1 and Mfn2) markers. It was also found to restore autophagy, as indicated by increased p62 protein level and LC3BII/I ratio. In addition, melatonin treatment increased SIRT1 protein level, mitochondrial ATP production, and SOD activity and decreased nitrites production. These effects were associated with enhanced oxidative phenotype, as evidenced by amplified oxidative fiber-specific markers expression, histochemical reaction for NADH enzyme, and muscular lipid content. In this study, we showed that melatonin might have potential therapeutic implications for obesity-induced SKM metabolic inflexibility among patients with obesity and T2DM.

Homo sapiens May Incorporate Daily Acute Cycles of “Conditioning–Deconditioning” to Maintain Musculoskeletal Integrity: Need to Integrate with Biological Clocks and Circadian Rhythm Mediators

Human evolution required adaptation to the boundary conditions of Earth, including 1 g gravity. The bipedal mobility of Homo sapiens in that gravitational field causes ground reaction force (GRF) loading of their lower extremities, influencing the integrity of the tissues of those extremities. However, humans usually experience such loading during the day and then a period of relative unloading at night. Many studies have indicated that loading of tissues and cells of the musculoskeletal (MSK) system can inhibit their responses to biological mediators such as cytokines and growth factors. Such findings raise the possibility that humans use such cycles of acute conditioning and deconditioning of the cells and tissues of the MSK system to elaborate critical mediators and responsiveness in parallel with these cycles, particularly involving GRF loading. However, humans also experience circadian rhythms with the levels of a number of mediators influenced by day/night cycles, as well as various levels of biological clocks. Thus, if responsiveness to MSK-generated mediators also occurs during the unloaded part of the daily cycle, that response must be integrated with circadian variations as well. Furthermore, it is also possible that responsiveness to circadian rhythm mediators may be regulated by MSK tissue loading. This review will examine evidence for the above scenario and postulate how interactions could be both regulated and studied, and how extension of the acute cycles biased towards deconditioning could lead to loss of tissue integrity.

Exercise, Diet and Sleeping as Regenerative Medicine Adjuvants: Obesity and Ageing as Illustrations

Regenerative medicine uses the biological and medical knowledge on how the cells and tissue regenerate and evolve in order to develop novel therapies. Health conditions such as ageing, obesity and cancer lead to an impaired regeneration ability. Exercise, diet choices and sleeping pattern have significant impacts on regeneration biology via diverse pathways including reducing the inflammatory and oxidative components. Thus, exercise, diet and sleeping management can be optimized towards therapeutic applications in regenerative medicine. It could allow to prevent degeneration, optimize the biological regeneration and also provide adjuvants for regenerative medicine.

Mechanisms of Melatonin in Obesity: A Review

Obesity and its complications have become a prominent global public health problem that severely threatens human health. Melatonin, originally known as an effective antioxidant, is an endogenous hormone found throughout the body that serves various physiological functions. In recent decades, increasing attention has been paid to its unique function in regulating energy metabolism, especially in glucose and lipid metabolism. Accumulating evidence has established the relationship between melatonin and obesity; nevertheless, not all preclinical and clinical evidence indicates the anti-obesity effect of melatonin, which makes it remain to conclude the clinical effect of melatonin in the fight against obesity. In this review, we have summarized the current knowledge of melatonin in regulating obesity-related symptoms, with emphasis on its underlying mechanisms. The role of melatonin in regulating the lipid profile, adipose tissue, oxidative stress, and inflammation, as well as the interactions of melatonin with the circadian rhythm, gut microbiota, sleep disorder, as well as the α7nAChR, the opioidergic system, and exosomes, make melatonin a promising agent to open new avenues in the intervention of obesity.

Dihydromyricetin resists inflammation-induced muscle atrophy via ryanodine receptor-CaMKK-AMPK signal pathway

Skeletal muscle plays a pivotal role in the maintenance of physical and metabolic health. Skeletal muscle atrophy usually results in physical disability, inferior quality of life and higher health care costs. The higher incidence of muscle atrophy in obese and ageing groups is due to increased levels of inflammatory factors during obesity and ageing. Dihydromyricetin, as a bioactive polyphenol, has been used for anti‐inflammatory, anti‐tumour and improving insulin sensitivity. However, there are no published reports demonstrated the dihydromyricetin effect on inflammation‐induced skeletal muscle atrophy. In this study, we first confirmed the role of dihydromyricetin in inflammation‐induced skeletal muscle atrophy in vivo and in vitro. Then, we demonstrated that dihydromyricetin resisted inflammation‐induced skeletal muscle atrophy by activating Ca²⁺‐CaMKK‐AMPK through signal pathway blockers, Ca²⁺ probes and immunofluorescence. Finally, we clarified that dihydromyricetin activated Ca²⁺‐CaMKK‐AMPK signalling pathway through interaction with the ryanodine receptor, its target protein, by drug affinity responsive target stability (DARTS). Our results not only demonstrated that dihydromyricetin resisted inflammation‐induced muscle atrophy via the ryanodine receptor‐CaMKK‐AMPK signal pathway but also discovered that the target protein of dihydromyricetin is the ryanodine receptor. Our results provided experimental data for the development of dihydromyricetin as a functional food and new therapeutic strategies for treating or preventing skeletal muscle atrophy.

Functional Mechanisms of Mitochondrial Respiratory Chain Supercomplex Assembly Factors and Their Involvement in Muscle Quality

Impairment of skeletal muscle function causes disabilities in elderly people. Therefore, in an aged society, prevention and treatment of sarcopenia are important for expanding healthy life expectancy. In addition to aging, adipose tissue disfunction and inflammation also contribute to the pathogenesis of sarcopenia by causing the combined state called ‘sarcopenic obesity’. Muscle quality as well as muscle mass contributes to muscle strength and physical performance. Mitochondria in the skeletal muscles affect muscle quality by regulating the production of energy and reactive oxygen species. A certain portion of the mitochondrial respiratory chain complexes form a higher-order structure called a “supercomplex”, which plays important roles in efficient energy production, stabilization of respiratory chain complex I, and prevention of reactive oxygen species (ROS) generation. Several molecules including phospholipids, proteins, and certain chemicals are known to promote or stabilize mitochondrial respiratory chain supercomplex assembly directly or indirectly. In this article, we review the distinct mechanisms underlying the promotion or stabilization of mitochondrial respiratory chain supercomplex assembly by supercomplex assembly factors. Further, we introduce regulatory pathways of mitochondrial respiratory chain supercomplex assembly and discuss the roles of supercomplex assembly factors and regulatory pathways in skeletal muscles and adipose tissues, believing that this will lead to discovery of potential targets for prevention and treatment of muscle disorders such as sarcopenia.