Melatonin decreases muscular oxidative stress and inflammation induced by strenuous exercise and stimulates growth factor synthesis

Is melatonin as an ergogenic hormone a myth? a systematic review and meta-analysis

PURPOSE

Melatonin supplementation has been disclosed as an ergogenic substance. However, the effectiveness of melatonin supplementation in healthy subjects has not been systematically investigated. The present study analyzed the effects of melatonin supplementation on physical performance and recovery. In addition, it was investigated whether exercise bout or training alter melatonin secretion in athletes and exercise practitioners.

METHODS

This systematic review and meta-analysis were conducted and reported according to the guidelines outlined in the PRISMA statement. Based on the search and inclusion criteria, 21 studies were included in the systematic review, and 19 were included in the meta-analysis.

RESULTS

Melatonin supplementation did not affect aerobic performance relative to time trial (-0.04; 95% CI: -0.51 to 0.44) and relative to VO2 (0.00; 95% CI: -0.57 to 0.57). Also, melatonin supplementation did not affect strength performance (0.19; 95% CI: -0.28 to 0.65). Only Glutathione Peroxidase (GPx) secretion increased after melatonin supplementation (1.40; 95% CI: 0.29 to 2.51). Post-exercise melatonin secretion was not changed immediately after an exercise session (0.56; 95% CI: -0.29 to 1.41) and 60 min after exercise (0.56; 95% CI: -0.29 to 1.41).

CONCLUSION

The data indicate that melatonin is not an ergogenic hormone. In contrast, melatonin supplementation improves post-exercise recovery, even without altering its secretion.

Melatonin enhances the ability of M2 macrophages to secrete IL10 by inhibiting Erk5 signaling pathway

BACKGROUND

Melatonin plays a role in repairing damaged cartilage and regulating immune cells. The anti-inflammatory effect of Melatonin involves multiple pathways and molecular activation, which directly or indirectly inhibits inflammatory reaction. M2 macrophages have the ability to anti-inflammatory response and repair damaged tissues, secrete IL10 and IL-4, and participate in tissue repair and remodeling. Erk5 is a recently discovered member of the MAPK family and one of the least studied members. It plays an important role in cell differentiation, proliferation, secretion and other functions. This experiment aims to study how Melatonin affects M2 Macrophage polarization and secretion through ERK5 signaling pathway.

METHODS

The RAW 264.7 macrophages were used for cell culture. The cells were cultured according to the pre-experimental results. The effects of Melatonin on M2 macrophages were comprehensively evaluated by CCK8 activity detection, RT-PCR, ELISA, cellular immunofluorescence, and WB.SD mice were selected to evaluate the effect of Melatonin on cartilage damage in rats with knee Osteoarthritis through HE staining, immunohistochemistry and immunofluorescence.

RESULTS

Melatonin cultivates RAW 264.7 macrophages. Without affecting the polarization ratio of M2 Macrophage polarization, Melatonin may reduce Erk5 gene expression, reduce Erk5 and p-Erk5 protein synthesis, and cooperate with BIX 02189 to enhance the secretion function of existing M2 macrophages and increase the secretion of cytokines IL10. Immunohistochemistry of rat knee Osteoarthritis model confirmed that the expression of IL10 was up-regulated and the synthesis of type II collagen was enhanced, but immunofluorescence found that the polarization of M2 Macrophage polarization in subchondral bone was not obvious.

CONCLUSION

Melatonin enhances the ability of M2 macrophages to secrete IL10 by inhibiting Erk5 signaling pathway, but has no effect on M2 Macrophage polarization.

Role of targeting TLR4 signaling axis in liver-related diseases

Toll-like receptor 4 (TLR4) plays an important role as a key signal-receiving transmembrane protein molecule in the liver, and substances that target the liver exert therapeutic effects via TLR4-related signaling pathways. This article provides a comprehensive review of targeting the TLR4 signaling axis to play an important role in the liver based on endogenous substances. Articles were divided into 5 major types of liver disease, acute liver injury, viral hepatitis, alcoholic and non-alcoholic liver disease, cirrhosis, and liver cancer, to elucidate how various endogenous substances affect the liver via the TLR4 pathway and the important role of the pathway itself in liver-related diseases to discover the potential therapeutic implications of the TLR4-related pathway in the liver. The results indicate that activation of the TLR4-related signaling axis primarily plays a role in promoting disease progression in liver-related diseases, and the TLR4/MyD88/NF-κB axis plays the most dominant role. Therefore, exploring the full effects of drugs targeting the TLR4-related signaling axis in the liver and the new use of old drugs may be a new research direction.

Melatonin Inhibits the Ferroptosis Pathway in Rat Bone Marrow Mesenchymal Stem Cells by Activating the PI3K/AKT/mTOR Signaling Axis to Attenuate Steroid-Induced Osteoporosis

Steroid-induced osteoporosis (SIOP) is a form of secondary osteoporosis, but its specific mechanism remains unclear. Glucocorticoid (GC-)-induced death of osteoblasts and bone marrow mesenchymal stem cells (BMSCs) is an important factor in SIOP. Ferroptosis is an iron-dependent type of programmed cell death and can be induced by many factors. Herein, we aimed to explore whether GCs cause ferroptosis of BMSCs, identify pathways as possible therapeutic targets, and determine the underlying mechanisms of action. In this study, we used high-dose dexamethasone (DEX) to observe whether GCs induce ferroptosis of BMSCs. Additionally, we established a rat SIOP model and then assessed whether melatonin (MT) could inhibit the ferroptosis pathway to provide early protection against GC-induced SIOP and investigated the signaling pathways involved. In vitro experiments confirmed that DEX induces ferroptosis in BMSCs. MT significantly alleviates GC-induced ferroptosis of BMSCs. Pathway analysis showed that MT ameliorates ferroptosis by activating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) axis. MT upregulates the expression of PI3K, which is an important regulator of ferroptosis resistance. PI3K activators mimic the antiferroptotic effect of MT, but when the PI3K pathway is blocked, the effect of MT is weakened. Using in vivo experiments, we confirmed the in vitro results and observed that MT can obviously protect against SIOP induced by GC. Notably, even after the initiation of GC-induced ferroptosis, MT can confer protection against SIOP. Our research confirms that GC-induced ferroptosis is closely related to SIOP. MT can inhibit ferroptosis by activating the PI3K/AKT/mTOR signaling pathway, thereby inhibiting the occurrence of SIOP. Therefore, MT may be a novel agent for preventing and treating SIOP.

Effects of Probiotic Supplementation on Exercise with Predominance of Aerobic Metabolism in Trained Population: A Systematic Review, Meta-Analysis and Meta-Regression

The scientific literature about probiotic intake and its effect on sports performance is growing. Therefore, the main aim of this systematic review, meta-analysis and meta-regression was to review all information about the effects of probiotic supplementation on performance tests with predominance of aerobic metabolism in trained populations (athletes and/or Division I players and/or trained population: ≥8 h/week and/or ≥5 workouts/week). A structured search was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA®) statement and PICOS guidelines in PubMed/MEDLINE, Web of Science (WOS), and Scopus international databases from inception to 1 November 2021. Studies involving probiotic supplementation in trained population and execution of performance test with aerobic metabolism predominance (test lasted more than 5 min) were considered for inclusion. Fifteen articles were included in the final systematic review (in total, 388 participants were included). After 3 studies were removed due to a lack of data for the meta-analysis and meta-regression, 12 studies with 232 participants were involved. With the objective of assessing the risk of bias of included studies, Cochrane Collaboration Guidelines and the Physiotherapy Evidence Database (PEDro) scale were performed. For all included studies the following data was extracted: authors, year of publication, study design, the size of the sample, probiotic administration (dose and time), and characteristics of participants. The random effects model and pooled standardized mean differences (SMDs) were used according to Hedges’ g for the meta-analysis. In order to determine if dose and duration covariates could predict probiotic effects, a meta-regression was also conducted. Results showed a small positive and significant effect on the performance test with aerobic metabolic predominance (SMD = 0.29; CI = 0.08−0.50; p < 0.05). Moreover, the subgroup analysis displayed significant greater benefits when the dose was ≥30 × 109 colony forming units (CFU) (SMD, 0.47; CI, 0.05 to 0.89; p < 0.05), when supplementation duration was ≤4 weeks (SMD, 0.44; CI, 0.05 to 0.84; p < 0.05), when single strain probiotics were used (SMD, 0.33; CI, 0.06 to 0.60; p < 0.05), when participants were males (SMD, 0.30; CI, 0.04 to 0.56; p < 0.05), and when the test was performed to exhaustion (SMD, 0.45; CI, 0.05 to 0.48; p < 0.05). However, with references to the findings of the meta-regression, selected covariates did not predict probiotic effects in highly trained population. In summary, the current systematic review and meta-analysis supported the potential effects of probiotics supplementation to improve performance in a test in which aerobic metabolism is predominant in trained population. However, more research is needed to fully understand the mechanisms of action of this supplement.

Melatonin, Zinc, and Vitamin C: Potential Adjuvant Treatment for COVID-19 Patients

The use of nutraceutical approaches may regulate the immune system, performing a potential strategy to contain the worst outcomes of COVID-19. We reviewed the current evidence surrounding nutritional/nutraceutical approaches for the therapy in patients with COVID-19. We searched the PubMed database to report randomized controlled trials (RCTs) and observational research that used melatonin, zinc, or vitamin C supplementation as an intervention for COVID-19 treatment. To date, we found only three concluded studies that assessed zinc supplementation and melatonin therapy in patients with COVID-19, but with inconclusive data, relatively small sample size, and early termination of the trial. On the other hand, vitamin C therapy appears to reduce hyperinflammation and improve the oxygen support status of patients with COVID-19. However, a large part of this research involves pilot trials, and there are still conflicting data regarding mortality rate, mechanical ventilation, and duration of symptoms of patients with COVID-19. Melatonin, zinc, and vitamin C supplementation should be investigated further on the nutritional status-immune response, and data from ongoing trials are needed to understand these molecules as a therapy strategy in patients COVID-19.

Exercise Performance Upregulatory Effect of R-α-Lipoic Acid with γ-Cyclodextrin

α-Lipoic acid (ALA) is a vitamin-like substance that is an indispensable supporting factor for a large number of enzymes. Due to its optical activity, ALA has optical isomers RALA and SALA. The major role of RALA is in energy metabolism. However, RALA cannot be used as a pharmaceutical or nutraceutical because it is sensitive to heat and acid conditions. Previous studies have shown that RALA complexed with γ-cyclodextrin (CD) has a higher antioxidant capacity than that of free RALA. The antioxidant enzyme system protects against intense exercise-induced oxidative damage and is related to the physical status of athletes. The aim of this study was to examine the effect of CD/RALA complex supplementation on antioxidant activity and performance during high-intensity exercise. Twenty-four male C3H/HeSlc mice were divided into four groups (n = 6): swimming+distilled water administration (C), swimming+CD/RALA supplementation (CD/RALA), swimming+RALA suplementation (RALA), and swimming+CD supplementation (CD). Blood ammonia elevation due to exercise stress was repressed by CD/RALA supplementation. The oxidative stress in the kidney increased after exercise and was reduced by CD/RALA supplementation. Our findings suggest that CD/RALA supplementation may be useful for improving the exercise performance in athletes.

Potentiating the Benefits of Melatonin through Chemical Functionalization: Possible Impact on Multifactorial Neurodegenerative Disorders

Although melatonin is an astonishing molecule, it is possible that chemistry will help in the discovery of new compounds derived from it that may exceed our expectations regarding antioxidant protection and perhaps even neuroprotection. This review briefly summarizes the significant amount of data gathered to date regarding the multiple health benefits of melatonin and related compounds. This review also highlights some of the most recent directions in the discovery of multifunctional pharmaceuticals intended to act as one-molecule multiple-target drugs with potential use in multifactorial diseases, including neurodegenerative disorders. Herein, we discuss the beneficial activities of melatonin derivatives reported to date, in addition to computational strategies to rationally design new derivatives by functionalization of the melatonin molecular framework. It is hoped that this review will promote more investigations on the subject from both experimental and theoretical perspectives.

Glutamine supplementation can reduce some atherosclerosis markers after exhaustive exercise in young healthy males

OBJECTIVES

Glutamine can be beneficial to athletes for its antiinflammatory and antioxidant effects. The present study was designed to investigate the effect of glutamine supplementation on some atherosclerosis markers after exhaustive exercise in young healthy males.

METHODS

In an intervention study, 30 healthy males (case = 15 and control = 15) were randomly assigned into two groups. For 14 d, the intervention group received 0.3 g of glutamine per kilogram of body weight per day, with 25 g of sugar in 250 mL of water, and the control group received 25 g of sugar per 250 mL of water. At the end of the intervention, the participants completed one session of exhaustive exercise, and then fasting blood samples were taken to test serum levels of atherosclerosis markers.

RESULTS

In the intervention group, the serum levels of leptin, cholesterol, and oxidized low-density lipoprotein were lower than in the control group after 2 wk of glutamine supplementation (P < 0.05). Interleukin-6 serum levels were lower in the intervention group compared to the control group after supplementation, but not significantly. Serum levels of leptin, interleukin-6, cholesterol, and oxidized low-density lipoprotein, as well as the ratio of oxidized low-density lipoprotein to high-density lipoprotein, were significantly decreased in the intervention group compared to the control group after exhaustive exercise (P < 0.05).

CONCLUSIONS

Glutamine supplementation has beneficial effects for athletes, particularly those doing strenuous physical exercise, through reducing atherosclerosis-related biomarkers and elevating serum adiponectin levels, and it can potentially play a role in decreasing the initiation and progression of atherosclerosis.

The potential remedy of melatonin on osteoarthritis

Osteoarthritis (OA), the most common arthritis worldwide, is a degenerative joint disease characterized by progressive cartilage breakdown, subchondral remodeling, and synovial inflammation. Although conventional pharmaceutical therapies aimed to prevent further cartilage loss and joint dysfunction, there are no ideal strategies that target the pathogenesis of OA. Melatonin exhibits a variety of regulatory properties by binding to specific receptors and downstream molecules and exerts a myriad of receptor-independent actions via intracellular targets as a chondrocyte protector, an anti-inflammation modulator, and a free radical scavenger. Melatonin also modulates cartilage regeneration and degradation by directly/indirectly regulating the expression of main circadian clock genes, such as transcriptional activators [brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein (Bmal) and circadian locomotor output cycles kaput (Clock)], transcriptional repressors [period circadian regulator (Per)1/2, cryptochrome (Cry)1/2, and Dec2], and nuclear hormone receptors [Rev-Erbs and retinoid acid-related orphan receptors (Rors)]. Owing to its effects on cartilage homeostasis, we propose a potential role for melatonin in the prevention and therapy of OA via the modulation of circadian clock genes, mitigation of chondrocyte apoptosis, anti-inflammatory activity, and scavenging of free radicals.

Ameliorating effect of melatonin on mercuric chloride-induced neurotoxicity in rats

Mercury is a highly toxic metal. It induces its toxicity via production of reactive oxygen species. Brain tissues are more susceptible to oxidative damage. Melatonin and its metabolites are free radical scavengers. The aim of this work is to elucidate the neuroprotective effect of melatonin on mercuric chloride-induced neurotoxicity in rats. Fifty male albino rats were used and divided into five groups. Group I acts as normal control. Group II (LD HgCl2) received mercuric chloride at a dose of 2 mg/kg. Group III (HD HgCl2) received HgCl2 at a dose of 4 mg/kg. Rats in group IV (LD HgCl2 +MLT) received HgCl2 2 mg/kg + Melatonin 5 mg/kg. Rats in group V (HD HgCl2+MLT) received HgCl2 4 mg/kg + Melatonin5 mg/kg. This study revealed that mercuric chloride decreased the activity of superoxide dismutase, catalase and glutathione peroxidase enzymes and increased malondialdehyde levels. Toxicity of mercuric chloride lead to upregulation of the gene expression level vascular endothelial growth factor. HgCl2 induced fragmentation of rough endoplasmic reticulum, ballooning of Golgi apparatus, nuclear and cytoplasmic degeneration of pyramidal neurones of rat cerebral cortex. This neuronal damage caused by HgCl2 was significantly improved by melatonin.

Activation of Paraventricular Melatonin Receptor 2 Mediates Melatonin-Conferred Cardioprotection Against Myocardial Ischemia/Reperfusion Injury

Previous studies have shown that melatonin (Mel) can effectively ameliorate myocardial ischemia/reperfusion (MI/R) injury, but the mechanism is yet to be fully elucidated. Mel receptors are expressed in the paraventricular nucleus (PVN), which is also involved in regulating cardiac sympathetic nerve activity. The aim of this study was to examine whether Mel receptors in the PVN are involved in the protective effects of Mel against MI/R injury. The results of quantitative polymerase chain reaction, western blot, and immunofluorescence assays indicated that Mel receptor 2 (MT2) expression in the PVN was upregulated after MI/R. Intraperitoneal administration of Mel significantly improved post-MI/R cardiac function and reduced the infarct size, whereas shRNA silencing of MT2 in the PVN partially blocked this effect. Intraperitoneal administration of Mel reduced sympathetic nerve overexcitation caused by MI/R, whereas shRNA silencing of MT2 in the PVN partially diminished this effect. Furthermore, enzyme-linked immunosorbent assay and western blot results indicated that intraperitoneal administration of Mel lowered the levels of inflammatory cytokines in the PVN after MI/R injury, whereas the application of sh-MT2 in the PVN reduced this effect of Mel. Mel significantly reduced the levels of NF-κB after astrocyte oxygen and glucose deprivation/reoxygenation injury, and this effect was offset when MT2 was silenced. The above experimental results suggest that MT2 in the PVN partially mediated the protective effects of Mel against MI/R injury, and its underlying mechanisms may be related to postactivation amelioration of PVN inflammation and reduction of cardiac sympathetic nerve overexcitation.

L-arginine Improves Plasma Lipid Profile and Muscle Inflammatory Response in Trained Rats After High-Intense Exercise

Purpose: This study aimed to evaluate whether supplementation with L-arginine alone or in combination with physical exercise training can modulate rats' lipid and inflammatory profiles after a single intense exercise session. Methods: Male Wistar rats were divided into four different groups: control (C), trained (T), supplemented with L-arginine (C + A) and trained and supplemented (T + A). Animals from supplemented groups (C + A and T + A groups) received 300 mg/kg animal body weight L-arginine diluted in 30 mL of drinking water for 8 weeks. Exercise training protocol (moderate intensity-70% achieved in the maximum effort test) was held 5 days/week for 8 weeks. Results: Exercise training induced a decrease in the amount of plasma, cholesterol and triglyceride totals, and skeletal muscle VEGF and CINC. Supplementation alone showed a benefit by reducing LDL levels. Conclusion: Training combined with supplementation showed a pronounced reduction in skeletal muscle VEGF and CINC amount. L-arginine supplementation, especially when associated with the regular aerobic physical exercise at moderate intensity was able to improve not only plasma lipid profile but also the inflammatory response of skeletal muscle immediately after an exhaustive physical exercise session.

The anti-inflammatory and analgesic effects of intraperitoneal melatonin after spinal nerve ligation are mediated by inhibition of the NF-κB/NLRP3 inflammasome signaling pathway

OBJECTIVE

To explore the potential analgesic effect of melatonin and its underlying molecular mechanisms in a neuropathic pain model induced by spinal nerve ligation (SNL).

METHODS

The experimental animals were divided into different groups including sham, vehicle, melatonin (MT) treatment, caspase-1 inhibitor (VX-765) treatment and MT2 antagonist (4P-PDOT) treatment. On the first three successive postoperative days, rats were intraperitoneally administered with MT, VX-765 or combination of MT and 4P-PDOT. Hyperalgesic behavior after SNL was evaluated using the paw withdrawal threshold (PWT). We then assessed expression of tumor necrosis factor-α (TNF-α), IL-18, interleukin-1β (IL-1β), NLRP3 inflammasome components, and nuclear factor-κB (NF-κB) activation using enzyme-linked immunosorbent assay kits (ELISA), real-time PCR, immunohistochemistry, and western blot, respectively, in spinal cord horn tissues extracted on postoperative day 7.

RESULTS

The results showed that melatonin treatment alleviated SNL-induced allodynia. We observed an SNL-induced upregulation of TNF-α, IL-18, IL-1β, NLRP3, ASC, cleaved caspase-1, and NF-κB in the lumbar spinal cord horn of rats, which was significantly attenuated by intraperitoneal injection of melatonin or VX-765. Additionally, co-treatment of melatonin and 4P-PDOT abrogated the analgesic and anti-inflammatory effect of melatonin.

CONCLUSION

Melatonin had potent analgesic and anti-inflammatory effects in SNL-induced neuropathic pain via NF-κB/NLRP3 inflammasome signaling pathway. Our results therefore suggested that this pathway could represent a novel therapeutic target for the management of neuropathic pain.

In vitro and in vivo evaluation of a nanofiber wound dressing loaded with melatonin

Wound healing is a complicated process that takes a long time to complete. The three-layer nanofiber wound dressing containing melatonin is highly expected to show remarkable wound repair by reducing the wound healing time. In this study, chitosan (Cs)-polycaprolactone (PCL)/ polyvinylalcohol (PVA)-melatonin (MEL)/ chitosan-polycaprolactone three-layer nanofiber wound dressing was prepared by electrospinning for melatonin sustained release. The characteristics of the wound dressing were further evaluated. The wound dressing had a high water uptake after 24 h (401%), and the water contact angle results showed that it had hydrophilicity effect that supported the cell attachment. The wound healing effect of wound dressing was examined using a full-thickness excisional model of rat skin by the local administration of MEL. The gene expressions of transforming growth factor-beta (TGF-β1), alpha-smooth muscle actin (α-SMA), collagen type I (COL1A1), and collagen type III (COL3A1) were further studied. The histopathological evaluation showed the complete regeneration of the epithelial layer, remodeling of wounds, collagen synthesis, and reduction in inflammatory cells. The NF + 20% MEL significantly increased TGF-β1, COL1A1, COL3A1, and α-SMA mRNA expressions. This wound dressing may have a considerable potential as a wound dressing to accelerate the wound healing.

Metabolomics Profiling and Diagnosis Biomarkers Searching for Drug-Induced Liver Injury Implicated to Polygonum multiflorum: A Cross-Sectional Cohort Study

Aim: The diagnosis of drug-induced liver injury (DILI) remains a challenge and the cases of Polygonum multiflorum Thunb. (PM) induced DILI (PM-DILI) have received much attention This study aimed to identify a simple and high-efficiency approach to PM-DILI diagnosis via metabolomics analysis.

Methods: Plasma metabolites in 13 PM-DILI patients were profiled by liquid chromatography along with high-resolution mass spectrometry. Meanwhile, the metabolic characteristics of the PM-DILI were compared with that of autoimmune hepatitis (AIH), hepatitis B (HBV), and healthy volunteers.

Results: Twenty-four metabolites were identified to present significantly different levels in PM-DILI patients compared with HBV and AIH groups. These metabolites were enriched into glucose, amino acids, and sphingolipids metabolisms. Among these essential metabolites, the ratios of P-cresol sulfate vs. phenylalanine and inosine vs. bilirubin were further selected using a stepwise decision tree to construct a classification model in order to differentiate PM-DILI from HBV and AIH. The model was highly effective with sensitivity of 92.3% and specificity of 88.9%.

Conclusions: This study presents an integrated view of the metabolic features of PM-DILI induced by herbal medicine, and the four-metabolite decision tree technique imparts a potent tool in clinical diagnosis.

Recovery of Diabetic Rats After Physical Exhaustion: Kinetic Alterations in Muscle Inflammation and Muscle-Signaling Proteins to Atrophy and Hypertrophy

The complexity of the adaptive response of diabetics to intense exercise is still poorly understood. To optimize exercise interventions in diabetics, the chronology of inflammatory mediators in muscle and the signaling involved in muscle hypertrophy/atrophy must be understood. Herein, we studied the kinetic inflammatory profile and cellular signaling pathways modulated by physical exhaustion after the induction of type 1 diabetes by streptozotocin in rats. Soleus muscle samples were obtained from diabetic and control groups at the following moments: baseline (no exercise); immediately after exhaustive exercise; and at 2 h, 24 h, 48 h, and 72 h after a treadmill exhaustive exercise. Kinetic production of cytokines and kinetic activation of proteins related to muscle synthesis (p70S6K and Akt) and degradation (GSK3, MuRF1, and MAFbx) were measured in the soleus muscle. We observed that the muscle TNF-α (0.9-fold; p = 0.0007), IL-1β (0.8-fold; p = 0.01), IL-6 (0.8-fold; p = 0.0013), L-selectin (1.0-fold; p = 0.0019), and CINC-2α/β (0.9-fold; p = 0.04) levels were higher in almost all stages of the study in the diabetic animals compared with the control group. Our data showed that exhaustive exercise decreased MAFbx expression in diabetic animals compared to the control group in a time-dependent manner. The decreased activation ratios of MAFbx were followed by a decrease in TNF-α, IL-1β, and IL-6 levels. p70S6k phosphorylation was also decreased in the diabetic group compared to the control group after physical exhaustion. Regarding the activation of proteins related to muscle synthesis and degradation, we found that the alterations induced by exhaustive exercise in the diabetic rats might involve pathways related to synthesis and muscle breakdown. Moreover, after an exhaustive exercise session, the recovery of the inflammatory response in the diabetic animals was slower than that in the control rats while the return of inflammatory cytokines to baseline levels was more effective in the diabetic animals.

Melatonin prevents LPS-induced epithelial-mesenchymal transition in human alveolar epithelial cells via the GSK-3β/Nrf2 pathway

BACKGROUND

Oxidative stress plays a critical role in pulmonary fibrosis after acute lung injury (ALI), and epithelial-mesenchymal transition (EMT) events are involved in this process. The purpose of this study was to investigate the protective effects of melatonin, a natural antioxidant, on lipopolysaccharide (LPS)-induced EMT in human alveolar epithelial cells.

METHODS

Human type II alveolar epithelial cell-derived A549 cells were incubated with LPS and melatonin alone or in combination for up to 24 h. The morphological changes of the treated cells were evaluated as well as indexes of oxidative stress. EMT-related proteins and the Nrf2 signaling pathway were detected by western blot analysis and immunofluorescence staining, respectively. To further investigate the underlying mechanisms, the effects of melatonin on cells transfected Nrf2 short hairpin RNA (shRNA) and the PI3K / GSK-3β signaling pathway were evaluated.

RESULTS

Treatment with melatonin upregulated Nrf2 expression, inhibited LPS-induced cell morphological change, reversed the expressions of EMT-related proteins, and reduced reactive oxygen species (ROS) production in A549 cells, as well as the levels of malondialdehyde (MDA) and anti-oxidative enzymes. Yet, the effects of melatonin were almost completely abolished in cells transfected Nrf2 shRNA. Furthermore, the data demonstrated that melatonin could activate the PI3K/AKT signaling pathway, resulting in phosphorylation of GSK-3β (Ser9) and upregulation of the Nrf2 protein in A549 cells, which ultimately attenuated LPS-induced EMT.

CONCLUSION

The present study is the first to demonstrate that melatonin can protect human alveolar epithelial cells against oxidative stress by effectively inhibiting LPS-induced EMT, which was mostly dependent on upregulation of the Nrf2 pathway via the PI3K/GSK-3β axis. Further studies are warranted to investigate the role of melatonin for the treatment of oxidative stress-associated diseases, as well as pulmonary fibrosis after ALI.

Antioxidant supplements and endurance exercise: Current evidence and mechanistic insights

Antioxidant supplements are commonly consumed by endurance athletes to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. There are numerous commercially available nutritional supplements that are targeted to athletes and health enthusiasts that allegedly possess antioxidant properties. However, most of these compounds are poorly investigated with respect to their in vivo redox activity and efficacy in humans. Therefore, this review will firstly provide a background to endurance exercise-related redox signalling and the subsequent adaptations in skeletal muscle and vascular function. The review will then discuss commonly available compounds with purported antioxidant effects for use by athletes. N-acetyl cysteine may be of benefit over the days prior to an endurance event; while chronic intake of combined 1000 mg vitamin C + vitamin E is not recommended during periods of heavy training associated with adaptations in skeletal muscle. Melatonin, vitamin E and α-lipoic acid appear effective at decreasing markers of exercise-induced oxidative stress. However, evidence on their effects on endurance performance are either lacking or not supportive. Catechins, anthocyanins, coenzyme Q10 and vitamin C may improve vascular function, however, evidence is either limited to specific sub-populations and/or does not translate to improved performance. Finally, additional research should clarify the potential benefits of curcumin in improving muscle recovery post intensive exercise; and the potential hampering effects of astaxanthin, selenium and vitamin A on skeletal muscle adaptations to endurance training. Overall, we highlight the lack of supportive evidence for most antioxidant compounds to recommend to athletes.

Gut-Muscle AxisExists and May Affect Skeletal Muscle Adaptation to Training

Excessive training may limit physiological muscle adaptation through chronic oxidative stress and inflammation. Improper diet and overtraining may also disrupt intestinal homeostasis and in consequence enhance inflammation. Altogether, these factors may lead to an imbalance in the gut ecosystem, causing dysregulation of the immune system. Therefore, it seems to be important to optimize the intestinal microbiota composition, which is able to modulate the immune system and reduce oxidative stress. Moreover, the optimal intestinal microbiota composition may have an impact on muscle protein synthesis and mitochondrial biogenesis and function, as well as muscle glycogen storage. Aproperly balanced microbiome may also reduce inflammatory markers and reactive oxygen species production, which may further attenuate macromolecules damage. Consequently, supplementation with probiotics may have some beneficial effect on aerobic and anaerobic performance. The phenomenon of gut-muscle axis should be continuously explored to function maintenance, not only in athletes.

Effect of nocturnal melatonin intake on cellular damage and recovery from repeated sprint performance during an intensive training schedule

An optimal recovery between training sessions is of similar if not greater importance as the training content and program of the training, itself. One of the most used strategies for improving recovery is the ingestion of supplements. The present study aimed to evaluate the effect of 5 mg oral melatonin supplementation on the recovery from repeated sprint (RSA) of performance and biochemical responses (i.e. oxidative stress, leukocytosis cellular damage) after an intensive training camp (TC). Twenty soccer players performed an RSA test before and after an intensive six-day TC associated with nocturnal melatonin (n = 10) or placebo (n = 10) ingestion. Resting and post-RSA test blood samples were obtained before and after the TC. Compared to placebo, melatonin intake decreased resting oxidative stress markers (i.e, advanced oxidation protein products), leukocytosis (i.e. white blood cells (WBC), neutrophils (NE)) and biomarkers of cellular damage (i.e. creatine kinase (CK)). It also lowered post-exercise leukocytosis (i.e. WBC, NE, lymphocytes (LY), monocytes (MO)) and biomarkers of cellular damage (i.e. CK, aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT)) and raised the activity of the main antioxidant enzymes (i.e. glutathione peroxidase (GPx), glutathione reductase (GR)). In addition, compared to placebo, melatonin reduced the deterioration of the best and total time during the RSA test after the TC. In conclusion, nocturnal melatonin supplementation during an intensive TC alleviated oxidative stress, leukocytosis and cellular damage and improved recovery of RSA performance in soccer players.

The regulatory role of melatonin in skeletal muscle

Melatonin (N-acetyl-5-methoxy-tryptamine) is an effective antioxidant and free radical scavenger, that has important biological effects in multiple cell types and species. Melatonin research in muscle has recently gained attention, mainly focused on its role in cells or tissue repair and regeneration after injury, due to its powerful biological functions, including its antioxidant, anti-inflammation, anti-tumor and anti-cancer, circadian rhythm, and anti-apoptotic effects. However, the effect of melatonin in regulating muscle development has not been systematically summarized. In this review, we outline the latest research on the involvement of melatonin in the regulation of muscle development and regeneration in order to better understand its underlying molecular mechanisms and potential applications.

Daytime melatonin levels in saliva are associated with inflammatory markers and anxiety disorders

BACKGROUND

The bidirectional interaction between melatonin and the immune system has largely gone unexplored in a clinical context and especially in a psychiatric population. This study explored the association between melatonin during the day and inflammatory cytokines in young adult patients seeking psychiatric care.

METHODS

Samples and data were collected from 108 young adults (mean age 21, SD = 2) at an outpatient clinic for affective disorders. Daytime saliva melatonin levels were analyzed with enzyme-linked immunosorbent assay (ELISA) in relation to normalized serum expression levels of 72 inflammatory markers in a proximity extension assay (PEA). In a post hoc analysis the markers associated with melatonin were tested in a generalized linear model to see whether there is a relationship to anxiety disorder or depression.

RESULTS

After Bonferroni correction for multiple testing, melatonin levels at 11:00 were positively correlated with CD5 (p = 4.2e-4). Melatonin levels after lunch were correlated with CCL2/MCP-1 (p = 4.2e-4), CCL3/MPI-1α (p = 6.5e-4) and VEGF-A (p = 5.3e-6). In the generalized linear model, positive associations were found for the presence of any anxiety disorder with melatonin after lunch (p = 0.046), VEGF-A (p = 0.001) and CCL3/MPI-1α (p = 0.001).

CONCLUSION

Daytime saliva levels of melatonin were related to several inflammatory markers in young adults with psychiatric disorders. This observation likely reflects the bidirectional relationship between melatonin production and the immune system. These findings may have relevance for the understanding of psychiatric disorders and other conditions associated with low-grade inflammation.

Impact of Melatonin on Skeletal Muscle and Exercise

Skeletal muscle disorders are dramatically increasing with human aging with enormous sanitary costs and impact on the quality of life. Preventive and therapeutic tools to limit onset and progression of muscle frailty include nutrition and physical training. Melatonin, the indole produced at nighttime in pineal and extra-pineal sites in mammalians, has recognized anti-aging, anti-inflammatory, and anti-oxidant properties. Mitochondria are the favorite target of melatonin, which maintains them efficiently, scavenging free radicals and reducing oxidative damage. Here, we discuss the most recent evidence of dietary melatonin efficacy in age-related skeletal muscle disorders in cellular, preclinical, and clinical studies. Furthermore, we analyze the emerging impact of melatonin on physical activity. Finally, we consider the newest evidence of the gut-muscle axis and the influence of exercise and probably melatonin on the microbiota. In our opinion, this review reinforces the relevance of melatonin as a safe nutraceutical that limits skeletal muscle frailty and prolongs physical performance.

Dance Training Improves Cytokine Secretion and Viability of Neutrophils in Diabetic Patients

Background

Evidence suggests that exercise improves neutrophil function. The decreased functional longevity of neutrophils and their increased clearance from infectious sites contribute to the increased susceptibility to infection and severity of infection observed in patients with diabetes.

Objective

Herein, we investigated the effects of a dance program on neutrophil number, function, and death in type 2 diabetes mellitus (T2DM) patients and healthy volunteers.

Methods

Ten patients with T2DM and twelve healthy individuals participated in a moderate-intensity dance training program for 4 months. The plasma levels of leptin, free fatty acids (FFAs), tumour necrosis factor-α (TNF-α), C-reactive protein (CRP), interleukin-1β (IL-1β), and interleukin-1 receptor antagonist (IL-1ra); neutrophil counts; extent of DNA fragmentation; cell membrane integrity; and production of TNF-α, interleukin-8 (IL-8), interleukin-6 (IL-6), and IL-1β in neutrophils were measured before and after training.

Results

Training reduced plasma levels of TNF-α (1.9-fold in controls and 2.2-fold in patients with T2DM) and CRP (1.4-fold in controls and 3.4-fold in patients with T2DM). IL-1ra levels were higher in the control group (2.2-fold) after training. After training, neutrophil DNA fragmentation was decreased in patients with T2DM (90%), while the number of neutrophils increased (70% in controls and 1.1-fold in patients with T2DM).

Conclusion

Dance training is a nonpharmacological strategy to reduce inflammation and improve neutrophil clearance in patients with T2DM.

The Evaluation of Exogenous Melatonin Administration in Supraspinatus Overuse Tendinopathy in an Experimental Rat Model

Background

Increased oxidative stress and inflammation play a critical role in the etiopathogenesis of chronic tendinopathy. Melatonin is an endogenous molecule that exhibits antioxidant and anti-inflammatory activity. The aim of this study was to evaluate the biochemical and histopathological effects of exogenous melatonin administrations in supraspinatus overuse tendinopathy.

Methods

Fifty rats were divided into the following four groups: cage activity, melatonin treatment, corticosteriod therapy, and control. Melatonin (10 mg/kg, intraperitoneal; twice a day) and triamcinolone (0.3 mg/kg, subacromial; weekly) were administered to the treatment groups after the overuse period. Biochemical and histopathological evaluations were performed on serum samples and biopsies obtained from rats. Plasma inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels were evaluated biochemically.

Results

The TAS, TOS, OSI, iNOS, and VEGF values were significantly lower than the pre-treatment levels in rats receiving exogenous melatonin treatment (3 or 6 weeks) (p<0.05). TOS, iNOS, VEGF, and OSI values after 3 weeks of triamcinolone administration, and TOS, VEGF, and OSI levels after 6 weeks of triamcinolone application, were significantly lower than the pre-treatment levels (p<0.05).

Conclusions

Exogenous melatonin application in overuse tendinopathy reduces oxidative stress and inflammation. Melatonin might be an alternative potential molecule to corticosteroids in the treatment of chronic tendinopathy.

Melatonin effects on pulmonary tissue in the experimental model of Hepatopulmonary Syndrome

Objective:

To evaluate the pulmonary alterations of animals with Hepatopulmonary Syndrome (HPS) submitted to Biliary Duct Ligature (BDL), as well as the antioxidant effect of Melatonin (MEL).

Methods:

Sixteen male Wistar rats, divided into four Sham groups: BDL group, Sham + MEL group and BDL + MEL. The pulmonary and hepatic histology, lipoperoxidation and antioxidant activity of lung tissue, alveolar-arterial O2 difference and lung / body weight ratio (%) were evaluated.

Results:

When comparing the groups, could be observed an increase of vasodilation and pulmonary fibrosis in the BDL group and the reduction of this in relation to the BDL + MEL group. It was also observed significant changes in the activity of catalase, ApCO2, ApO₂ in the LBD group when compared to the other groups.

Conclusion:

The use of MEL has been shown to be effective in reducing vasodilation, fibrosis levels and oxidative stress as well as gas exchange in an experimental HPS model.

Effect of Forced Physical Activity on the Severity of Experimental Colitis in Normal Weight and Obese Mice. Involvement of Oxidative Stress and Proinflammatory Biomarkers

Inflammatory bowel diseases are a heterogeneous group of disorders represented by two major phenotypic forms, Crohn’s disease and ulcerative colitis. Cross talk between adipokines and myokines, as well as changes in intestinal microcirculation, was proposed in pathogenesis of these disorders. C57BL/6 male mice were fed ad libitum for 12 weeks a standard (SD) or high-fat diet (HFD). After the adaptation period, two groups of animals fed SD or HFD were subjected to 6 weeks of the forced treadmill exercise and the experimental colitis was induced in both groups of sedentary and exercising mice fed SD and HFD by intra-colonic administration of 2,4,6-trinitrobenzenesulfonic acid. The disease activity index (DAI), colonic blood flow (CBF), the weight of animals, caloric intake, the mesenteric fad pad, the colonic oxidative stress markers malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) activity and intestinal expression and protein content of proinflammatory markers were evaluated. Macroscopic and microscopic colitis in sedentary SD mice was accompanied by a significant fall in CBF and exacerbated in those fed a HFD. The contents of MDA, GSH, and SOD activity were significantly increased in both SD and HFD fed mice with treadmill exercise as compared with sedentary mice. In sedentary HFD mice a significant increase in the intestinal oxidative stress parameters and mucosal expression of IL-1β, TNF-α, IL-17, IFNγ, IL-6, and IL-10 protein were observed and these effects were aggravated in mice subjected to forced treadmill exercise. The mucosal expression of mRNA for TNF-α, IL-1β, iNOS, COX-2, SOD-1, SOD-2, GPx mRNAs, and the hypoxia inducible factor (HIF)-1α protein expression were upregulated in colonic mucosa of treadmill exercising HFD mice with colitis compared with those without exercise. We conclude that forced treadmill running exacerbates the severity of colonic damage in obese mice due to a fall in colonic microcirculation, an increase in oxidative stress, and the rise in expression and activity of proinflammatory biomarkers.

Melatonin Mitigates Mitochondrial Meltdown: Interactions with SIRT3

Melatonin exhibits extraordinary diversity in terms of its functions and distribution. When discovered, it was thought to be uniquely of pineal gland origin. Subsequently, melatonin synthesis was identified in a variety of organs and recently it was shown to be produced in the mitochondria. Since mitochondria exist in every cell, with a few exceptions, it means that every vertebrate, invertebrate, and plant cell produces melatonin. The mitochondrial synthesis of melatonin is not photoperiod-dependent, but it may be inducible under conditions of stress. Mitochondria-produced melatonin is not released into the systemic circulation, but rather is used primarily in its cell of origin. Melatonin's functions in the mitochondria are highly diverse, not unlike those of sirtuin 3 (SIRT3). SIRT3 is an NAD+-dependent deacetylase which regulates, among many functions, the redox state of the mitochondria. Recent data proves that melatonin and SIRT3 post-translationally collaborate in regulating free radical generation and removal from mitochondria. Since melatonin and SIRT3 have cohabitated in the mitochondria for many eons, we predict that these molecules interact in many other ways to control mitochondrial physiology. It is predicted that these mutual functions will be intensely investigated in the next decade and importantly, we assume that the findings will have significant applications for preventing/delaying some age-related diseases and aging itself.

Melatonin and its metabolites vs oxidative stress: From individual actions to collective protection

Oxidative stress (OS) represents a threat to the chemical integrity of biomolecules including lipids, proteins, and DNA. The associated molecular damage frequently results in serious health issues, which justifies our concern about this phenomenon. In addition to enzymatic defense mechanisms, there are compounds (usually referred to as antioxidants) that offer chemical protection against oxidative events. Among them, melatonin and its metabolites constitute a particularly efficient chemical family. They offer protection against OS as individual chemical entities through a wide variety of mechanisms including electron transfer, hydrogen transfer, radical adduct formation, and metal chelation, and by repairing biological targets. In fact, many of them including melatonin can be classified as multipurpose antioxidants. However, what seems to be unique to the melatonin's family is their collective effects. Because the members of this family are metabolically related, most of them are expected to be present in living organisms wherever melatonin is produced. Therefore, the protection exerted by melatonin against OS may be viewed as a result of the combined antioxidant effects of the parent molecule and its metabolites. Melatonin's family is rather exceptional in this regard, offering versatile and collective antioxidant protection against OS. It certainly seems that melatonin is one of the best nature's defenses against oxidative damage.

Melatonin Treatment Improves Insulin Resistance and Pigmentation in Obese Patients with Acanthosis Nigricans

OBJECTIVE

This study aimed to determine the effects of melatonin on insulin resistance in obese patients with acanthosis nigricans (AN).

METHODS

A total of 17 obese patients with acanthosis nigricans were recruited in a 12-week pilot open trial. Insulin sensitivity, glucose metabolism, inflammatory factors, and other biochemical parameters before and after the administration of melatonin were measured.

RESULTS

After 12 weeks of treatment with melatonin (3 mg/day), homeostasis model assessment insulin resistance index (HOMA-IR) (8.99 ± 5.10 versus 7.77 ± 5.21, p < 0.05) and fasting insulin (37.09 5 ± 20.26 μU/ml versus 32.10 ± 20.29 μU/ml, p < 0.05) were significantly decreased. Matsuda index (2.82 ± 1.54 versus 3.74 ± 2.02, p < 0.05) was significantly increased. There were also statistically significant declines in the AN scores of the neck and axilla, body weight, body mass index, body fat, visceral index, neck circumference, waist circumference, and inflammatory markers.

CONCLUSIONS

It was concluded that melatonin could improve cutaneous symptoms in obese patients with acanthosis nigricans by improving insulin sensitivity and inflammatory status. This trial is registered with ClinicalTrials.gov NCT02604095.

Exogenous melatonin in the treatment of pain: a systematic review and meta-analysis

Melatonin is an important hormone for regulating mammalian circadian biology and cellular homeostasis. Recent evidence has shown that melatonin exerts anti-nociception effects in both animals and humans. However, according to clinical trials, the anti-nociception effects of melatonin are still controversial. The aim of this meta-analysis was to investigate the anti-nociception effects of melatonin premedication. The primary outcome was the effects of melatonin on pain intensity. The secondary outcomes included the number of patients with analgesic requirements, total analgesic consumption, and brain-derived neurotrophic factor (BDNF) levels. In total, 19 studies were included in the current meta-analysis. The pooling data show that melatonin significantly decreased the pain intensity, as evidenced by the pain scores. Moreover, melatonin administration also reduced the proportion of patients with analgesic requirements and BDNF levels. However, the effects of melatonin on total analgesic consumption still require further confirmation. Collectively, the current meta-analysis supports the use of melatonin for anti-nociception.

Melatonin inhibits nucleus pulposus (NP) cell proliferation and extracellular matrix (ECM) remodeling via the melatonin membrane receptors mediated PI3K-Akt pathway

Pinealectomy in vertebrates accelerated intervertebral disk degeneration (IDD). However, the potential mechanisms, particularly melatonin's role, are still to be clarified. In this study, for first time, melatonin membrane receptors of MT1 and MT2 were found to be present in the human intervertebral disk tissues and nucleus pulposus (NP) cells, respectively. Melatonin treatment significantly inhibited NP cell proliferation in dose-dependent manner. Accordingly, melatonin down-regulated gene expression of cyclin D1, PCNA, matrix metallopeptidase-3, and matrix metallopeptidase-9 and upregulated gene expression of collagen type II alpha 1 chain and aggrecan in NP cells. These effects of melatonin were blocked by luzindole, a nonspecific melatonin membrane receptor antagonist. Signaling pathway analysis indicated that in the intervertebral disk tissues and NP cells, melatonin acted on MT1/2 and subsequently reduced phosphorylation of phosphoinositide 3-kinase p85 regulatory subunit, phosphoinositide-dependent kinase-1, and Akt. The results indicate that melatonin is a crucial regulator of NP cell function and plays a vital role in prevention of IDD.

Melatonin Supplementation Ameliorates Energy Charge and Oxidative Stress Induced by Acute Exercise in Rat Heart Tissue

BACKGROUND

Regular physical exercises may help people to be more resistant to everyday problems; however, how acute and intense exercises affect the heart tissues functioning with maximum capacity and how melatonin changes the effect of acute and intense exercises are still not obvious. We aimed to comprehend whether melatonin intravenous injection supports the oxidative/antioxidative conditions and energy charge in heart tissues of rats exposed to acute swimming exercise.

METHODS

Thirty Wistar-albino male rats were categorized into 3 groups with equal number of subjects. Control group performed no application, and acute intensive swimming exercise group were subjected to acute intensive swimming exercise for 30 minutes, and melatonin group were applied 25 mg/kg single dose melatonin administration prior to 30 minutes acute intensive swimming exercise. The levels of malondialdehyde (MDA), and superoxide dismutase, catalase and glutathione peroxidase activities were measured by spectrophotometric method; and the levels of 3-nitrotyrosine (3-NT) and energy charge were determined by a high performance liquid chromatography.

RESULTS

Tissue MDA and 3-NT levels of the acute intensive exercise group were found to be higher than the control group. It was also found that the melatonin administration increased the energy charge and antioxidant activities, while decreased tissue MDA and 3-NT levels in heart tissues. Our results provide evidence for melatonin that can exert potent protective effects on oxidative stress and energy charge for heart tissues in acute swimming exercise.

CONCLUSIONS

These findings suggest that the direct beneficial effects of melatonin could be potentially applied on prevention of oxidative stress and energy deficit.

Endogenous melatonin promotes rhythmic recruitment of neutrophils toward an injury in zebrafish

Neutrophil recruitment to injured tissue appears to be an evolutionarily conserved strategy for organisms to fight against exogenous insults. Recent studies have shown rhythmic migration of neutrophils and several factors, including melatonin, have been implicated in regulating this rhythmic migration. The mechanisms underlying how endogenous melatonin regulates rhythmic neutrophils migration, however, are unclear. Here we generated a zebrafish annat2 mutant that lacks endogenous melatonin and, subsequently, a Tg(lyz:EGFP);aanat2^−/− transgenic line that allows for monitoring neutrophils migration visually in live zebrafish. We observed that migrating neutrophils are significantly reduced in aanat2^−/− mutant zebrafish under a light/dark condition, and the disrupted migrating rhythmicity of neutrophils in aanat2^−/− zebrafish is independent of the circadian clock. Further, we also found that endogenous melatonin enhances neutrophils migration likely by inducing the expression of cytokines such as interleukin-8 and interleukin-1β. Together, our findings provide evidence that endogenous melatonin promotes rhythmic migration of neutrophils through cytokines in zebrafish.

Utilizing melatonin to combat bacterial infections and septic injury

Melatonin, also known as N-acetyl-5-methoxytryptamine, is a ubiquitously acting molecule that is produced by the pineal gland and other organs of animals, including humans. As melatonin and its metabolites are potent antioxidants and free radical scavengers, they are protective against a variety of disorders. Moreover, multiple molecular targets of melatonin have been identified, and its actions are both receptor-mediated and receptor-independent. Recent studies have shown that melatonin may be useful in fighting against sepsis and septic injury due to its antioxidative and anti-inflammatory actions; the results generally indicate a promising therapeutic application for melatonin in the treatment of sepsis. To provide a comprehensive understanding regarding the protective effects of melatonin against septic injury, in the present review we have evaluated the published literature in which melatonin has been used to treat experimental and clinical sepsis. Firstly, we present the evidence from studies that have used melatonin to resist bacterial pathogens. Secondly, we illustrate the protective effect of melatonin against septic injury and discuss the possible mechanisms. Finally, the potential directions for future melatonin research against sepsis are summarized.

Melatonin, a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis

There is highly credible evidence that melatonin mitigates cancer at the initiation, progression and metastasis phases. In many cases, the molecular mechanisms underpinning these inhibitory actions have been proposed. What is rather perplexing, however, is the large number of processes by which melatonin reportedly restrains cancer development and growth. These diverse actions suggest that what is being observed are merely epiphenomena of an underlying more fundamental action of melatonin that remains to be disclosed. Some of the arresting actions of melatonin on cancer are clearly membrane receptor-mediated while others are membrane receptor-independent and involve direct intracellular actions of this ubiquitously-distributed molecule. While the emphasis of melatonin/cancer research has been on the role of the indoleamine in restraining breast cancer, this is changing quickly with many cancer types having been shown to be susceptible to inhibition by melatonin. There are several facets of this research which could have immediate applications at the clinical level. Many studies have shown that melatonin's co-administration improves the sensitivity of cancers to inhibition by conventional drugs. Even more important are the findings that melatonin renders cancers previously totally resistant to treatment sensitive to these same therapies. Melatonin also inhibits molecular processes associated with metastasis by limiting the entrance of cancer cells into the vascular system and preventing them from establishing secondary growths at distant sites. This is of particular importance since cancer metastasis often significantly contributes to death of the patient. Another area that deserves additional consideration is related to the capacity of melatonin in reducing the toxic consequences of anti-cancer drugs while increasing their efficacy. Although this information has been available for more than a decade, it has not been adequately exploited at the clinical level. Even if the only beneficial actions of melatonin in cancer patients are its ability to attenuate acute and long-term drug toxicity, melatonin should be used to improve the physical wellbeing of the patients. The experimental findings, however, suggest that the advantages of using melatonin as a co-treatment with conventional cancer therapies would far exceed improvements in the wellbeing of the patients.

Beneficial Effects of Exogenous Melatonin in Acute Staphylococcus aureus and Escherichia coli Infection-Induced Inflammation and Associated Behavioral Response in Mice After Exposure to Short Photoperiod

The administration of melatonin during acute bacterial infection was evaluated in this study. Mice pre-exposed to normal photoperiodic (NP), short photoperiodic (SP), and long photoperiodic (LP) day lengths were infected separately with live Staphylococcus aureus (5 × 10⁶ cells/ml) or Escherichia coli (2.5 × 10⁷ colony-forming units/ml) and treated with melatonin (10 mg/kg body weight). Behavioral studies were performed before bacterial infection and after melatonin administration. In mice pre-exposed to SP, exogenous melatonin administration resulted in better clearance of bacteria from blood and behavioral improvement. Reduced glutathione content and superoxide dismutase activities were increased, with concomitant decrease in lipid peroxidation content and catalase activities in the liver, brain, and spleen after exogenous melatonin administration. The overproduction of tumor necrosis factor-α, interferon-γ, and interleukin-6 during acute bacterial infection in mice exposed to different photoperiods was probably regulated by the administration of exogenous melatonin, by reducing neutrophil recruitment to spleen, expression of inducible nitric oxide synthase and cyclooxygenase-2 in hypothalamus, and C-reactive protein in the serum, and was also associated with improved behavioral response. Photoperiodic variations in inflammatory and oxidative stress markers might be correlated to serum melatonin and corticosterone levels. This study suggests that the administration of melatonin during SP exposure is protective in infection-induced inflammation than NP and LP exposure.

N-acetylcysteine a possible protector against indomethacin-induced peptic ulcer: crosstalk between antioxidant, anti-inflammatory, and antiapoptotic mechanisms

This study investigated the gastroprotective effects of N-acetylcysteine (NAC) against indomethacin-induced gastric ulcer in rats. Ulceration was induced by a single oral administration of indomethacin (30 mg/kg). 50 male albino rats were allocated into 5 equal groups: control group received normal saline orally, indomethacin group rats received normal saline orally for 5 days and indomethacin (50 mg/kg) on the last day, ranitidine group received ranitidine (reference drug) orally for 5 days (50 mg/kg) before receiving indomethacin (50 mg/kg) on the last day, and NAC groups received NAC orally at 300 and 500 mg/kg, respectively, for 5 days before receiving indomethacin (50 mg/kg) on the last day. Gastric tissue interleukin-1β (IL-1β), interferon-γ (IFN-γ), and caspase-3 levels were immunoassayed. Total thiol (T-SH), myeloperoxidase (MPO), and glucose-6-phosphate dehydrogenase (G6PD) were determined by spectrophotometry. Cytokine-induced neutrophil chemoattractant 2α (CINC-2α) gene expression was evaluated in addition to Bcl-2 immunohistochemistry. Pretreatment with NAC improved the inflammatory, apoptotic, and redox status in a dose-dependent manner particularly in NAC 500 mg/kg pretreated group. These results show a role for NAC in improving indomethacin-induced gastric ulceration via antioxidative, antiapoptotic, and anti-inflammatory interactive mechanisms.

Nutritional leucine supplementation attenuates cardiac failure in tumour-bearing cachectic animals

BACKGROUND

The condition known as cachexia presents in most patients with malignant tumours, leading to a poor quality of life and premature death. Although the cancer-cachexia state primarily affects skeletal muscle, possible damage in the cardiac muscle remains to be better characterized and elucidated. Leucine, which is a branched chain amino acid, is very useful for preserving lean body mass. Thus, this amino acid has been studied as a coadjuvant therapy in cachectic cancer patients, but whether this treatment attenuates the effects of cachexia and improves cardiac function remains poorly understood. Therefore, using an experimental cancer-cachexia model, we evaluated whether leucine supplementation ameliorates cachexia in the heart.

METHODS

Male Wistar rats were fed either a leucine-rich or a normoprotein diet and implanted or not with subcutaneous Walker-256 carcinoma. During the cachectic stage (approximately 21 days after tumour implantation), when the tumour mass was greater than 10% of body weight, the rats were subjected to an electrocardiogram analysis to evaluate the heart rate, QT-c, and T wave amplitude. The myocardial tissues were assayed for proteolytic enzymes (chymotrypsin, alkaline phosphatase, cathepsin, and calpain), cardiomyopathy biomarkers (myeloperoxidase, tissue inhibitor of metalloproteinases, and total plasminogen activator inhibitor 1), and caspase-8, -9, -3, and -7 activity.

RESULTS

Both groups of tumour-bearing rats, especially the untreated group, had electrocardiography alterations that were suggestive of ischemia, dilated cardiomyopathy, and sudden death risk. Additionally, the rats in the untreated tumour-bearing group but not their leucine-supplemented littermates exhibited remarkable increases in chymotrypsin activity and all three heart failure biomarkers analysed, including an increase in caspase-3 and -7 activity.

CONCLUSIONS

Our data suggest that a leucine-rich diet could modulate heart damage, cardiomyocyte proteolysis, and apoptosis driven by cancer-cachexia. Further studies must be conducted to elucidate leucine's mechanisms of action, which potentially includes the modulation of the heart's inflammatory process.