Intake of melatonin is associated with amelioration of physiological changes, both metabolic and morphological pathologies associated with obesity: an animal model

Melatonin associated with a high-fat diet during pregnancy and lactation prevents liver changes in the offspring

In the present study, we set out to determine whether melatonin combined with a high-fat diet during pregnancy and lactation can prevent liver disorders in offspring. Forty rats were divided into four groups: DC - pregnant rats submitted to the standard diet; DC + Mel - pregnant rats submitted to the standard diet combined with melatonin; HFD - pregnant rats submitted to a high-fat diet; HFD + Mel - pregnant rats submitted to a high-fat diet combined with melatonin. Morphophysiological and biochemical parameters were analyzed. Melatonin (5 mg/kg) was administered intraperitoneally. The HFD group offspring showed an increase in AST, ALT, alkaline phosphatase, cholesterol, triglycerides, LDL and glucose levels, and a reduction in HDL and lipase levels. In the liver obseved steatosis, hepatocellular ballooning, increased lobular parenchyma and reduced non-lobular parenchyma, beside reduced liver glycogen and fibrosis. These changes were not observed in the HFD + Mel group. In conclusion, melatonin combined with a high-fat diet preserves the liver architecture and function in the offspring.

Melatonin Inhibits 17β-Estradiol-Induced Epithelial-Mesenchymal Transition in Endometrial Adenocarcinoma Cells via Upregulating Numb Expression

OBJECTIVES

Melatonin (MLT) shows antitumor effects in various tumor types, including endometrial carcinoma. However, the molecular mechanism involved is unclear. In the current study, we investigated the effect of MLT on the estrogen-induced epithelial-mesenchymal transition (EMT) in endometrial adenocarcinoma cells and explored the pathway that might be involved.

DESIGN

Laboratory study was via cultured endometrial cancer cells. Design refers only to in vitro experiments.

METHODS

In cell culture experiments, cell growth was examined using CCK-8 assays. The expression of Numb and EMT markers in Ishikawa cells was examined using Western blot analysis and real-time PCR. Cell invasion was examined using transwell assays. Cell migration was examined using wound-healing assays and transwell assays. Using immunohistochemistry analysis, the expression of Numb in human endometrial cancers was examined.

RESULTS

In immunohistochemistry experiments, we found that 15.2% of atypical endometrial hyperplasia and 15.6% of endometrial carcinoma did not express Numb. In cell culture experiments, MLT inhibited cell proliferation, invasion, and migration induced by 17β-estradiol (E2) in endometrial cancer cells. MLT decreased the expression of vimentin and Slug and increased the expression of Numb and E-cadherin in Ishikawa cells. Numb knockdown in cancer cells significantly increased cell proliferation, invasion, and migration.

LIMITATIONS

No animal experiments were performed.

CONCLUSIONS

MLT blocked E2-induced cell growth and EMT in endometrial cancer cells via upregulating Numb expression.

Kidney Damage Caused by Obesity and Its Feasible Treatment Drugs

The rapid growth of obesity worldwide has made it a major health problem, while the dramatic increase in the prevalence of obesity has had a significant impact on the magnitude of chronic kidney disease (CKD), especially in developing countries. A vast amount of researchers have reported a strong relationship between obesity and chronic kidney disease, and obesity can serve as an independent risk factor for kidney disease. The histological changes of kidneys in obesity-induced renal injury include glomerular or tubular hypertrophy, focal segmental glomerulosclerosis or bulbous sclerosis. Furthermore, inflammation, renal hemodynamic changes, insulin resistance and lipid metabolism disorders are all involved in the development and progression of obesity-induced nephropathy. However, there is no targeted treatment for obesity-related kidney disease. In this review, RAS inhibitors, SGLT2 inhibitors and melatonin would be presented to treat obesity-induced kidney injury. Furthermore, we concluded that melatonin can protect the kidney damage caused by obesity by inhibiting inflammation and oxidative stress, revealing its therapeutic potential.

Melatonin and cardiovascular disease: from mechanisms of action to potential clinical use (literature review)

Cardiovascular disease remains the most relevant public health problem. Most cardiovascular diseases are associated with an atherosclerosis, the development of which is associated with inflammation and endothelial dysfunction. Melatonin is a neurohormone that is synthesized mainly in the pineal gland and plays a central role in the regulation of sleep and some other body cyclic processes. For a long time, melatonin was perceived as a substance that is effective in the treatment of circadian cycle impairments. At the same time, a large number of studies have accumulated recently that demonstrate a wider range of its biological effects, including anti-inflammatory, antioxidant, antihypertensive and, possibly, hypolipidemic. The review includes current data from experimental and clinical studies demonstrating the cardioprotective effects of melatonin in atherosclerosis, myocardial ischemia, and heart failure.

Animal models of diabetic microvascular complications: Relevance to clinical features

Diabetes has become more common in recent years worldwide, and this growth is projected to continue in the future. The primary concern with diabetes is developing various complications, which significantly contribute to the disease's mortality and morbidity. Over time, the condition progresses from the pre-diabetic to the diabetic stage and then to the development of complications. Years and enormous resources are required to evaluate pharmacological interventions to prevent or delay the progression of disease or complications in humans. Appropriate screening models are required to gain a better understanding of both pathogenesis and potential therapeutic agents. Different species of animals are used to evaluate the pharmacological potentials and study the pathogenesis of the disease. Animal models are essential for research because they represent most of the structural, functional, and biochemical characteristics of human diseases. An ideal screening model should mimic the pathogenesis of the disease with identifiable characteristics. A thorough understanding of animal models is required for the experimental design to select an appropriate model. Each animal model has certain advantages and limitations. The present manuscript describes the animal models and their diagnostic characteristics to evaluate microvascular diabetic complications.

Ameliorating effect of melatonin against nicotine induced lung and heart toxicity in rats

The present study was carried out to investigate the ameliorative effects of melatonin against nicotine-induced heart and lung toxicity. For this purpose, 75 mature male Sprague Dawley (SD) rats weighing 150-170 g were randomly divided into five groups (15 rats each): control group (rats were I/P injected with 1% ethanol in saline), nicotine group (rats were I/P injected with 0.6 mg/kg body weight), and combined nicotine and melatonin groups (rats received nicotine as in the previous group and melatonin at a dose of 1, 5, or 10 mg/kg body weight, respectively); all treatments were continued for 21 days. Fasting blood samples were collected from each rat at the 11th day and one day after the end of the last injection (22nd day) for complete blood count (CBC) determination, while sera were collected for the determination of lipid profiles. Malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, and reduced glutathione (GSH) as well as DNA fragmentation percentage were assessed in cardiac tissue. Heart and lung samples were collected for estimation of caspase-3 expression and histopathological examination. The results revealed that nicotine increased the number of RBCs, Hb concentration, total cholesterol, and low density lipoprotein (LDL) and decreased high density lipoprotein (HDL). In addition, it decreased SOD activity and GSH concentration with increased MDA concentration, and DNA fragmentation in the heart, as well as caspase-3 expression in both heart and lungs. It also induced histopathological changes in the heart and lung tissues. Melatonin could ameliorate the deleterious effect of nicotine on the previous parameters either partially or completely, where melatonin restored complete blood count, improved lipid profile, mended lipid peroxidation and antioxidant parameters in the cardiac tissue, rectified caspase-3 expression in the heart and lungs, ameliorated DNA fragmentation percentage in the heart, and protected both heart and lung tissue against the harmful effect of nicotine. It is concluded that melatonin has a protective effect on the heart and lungs against the harmful effect of nicotine.

Mitochondrial Oxidative Phosphorylation Function and Mitophagy in Ischaemic/Reperfused Hearts from Control and High-Fat Diet Rats: Effects of Long-Term Melatonin Treatment

PURPOSE

Oxidative stress causes mitochondrial dysfunction in myocardial ischaemia/reperfusion (I/R) as well as in obesity. Mitochondrial depolarization triggers mitophagy to degrade damaged mitochondria, a process important for quality control. The aims of this study were to evaluate (i) the effect of I/R on mitochondrial oxidative phosphorylation and its temporal relationship with mitophagy in hearts from obese rats and their age-matched controls, and (ii) the role of oxidative stress in these processes using melatonin, a free radical scavenger.

METHODS

Male Wistar rats were divided into 4 groups: control (normal diet ± melatonin) and high-fat sucrose diet (HFSD ± melatonin). Rats received melatonin orally (10 mg/kg/day). After 16 weeks, hearts were removed and subjected to 40-min stabilization, and 25-min global ischaemia/10-min reperfusion for preparation of mitochondria. Mitochondrial oxidative phosphorylation was measured polarographically. Western blotting was used for evaluation of PINK1, Parkin, p62/SQSTM1 (p62) and TOM 70. Infarct size was measured using tetrazolium staining.

RESULTS

Ischaemia and reperfusion respectively reduced and increased mitochondrial QO2 (state 3) and the ox-phos rate in both control and HFSD mitochondria, showing no major changes between the groups, while melatonin pretreatment had little effect. p62 as indicator of mitophagic flux showed up- and downregulation of mitophagy by ischaemia and reperfusion respectively, with melatonin having no significant effect. Melatonin treatment caused a significant reduction in infarct size in hearts from both control and diet groups.

CONCLUSIONS

The results suggest that I/R (i) affects mitochondria from control and HFSD hearts similarly and (ii) melatonin-induced cardioprotection is not associated with reversal of mitochondrial dysfunction or changes in the PINK1/Parkin pathway.

Effects of melatonin supplementation on disease activity, oxidative stress, inflammatory, and metabolic parameters in patients with rheumatoid arthritis: a randomized double-blind placebo-controlled trial

OBJECTIVE

Considering the pathologic significance of inflammation and oxidative stress in rheumatoid arthritis (RA) as well as the antioxidant, anti-inflammatory and hypolipidemic effects of melatonin, the current research is designed to investigate the effect of melatonin supplementation on disease activity, oxidative stress, inflammatory, and metabolic parameters in RA patients.

METHODS

In this randomized double-blind, placebo-controlled trial, 64 RA cases were selected and randomly assigned into 2 groups to take 6 mg/day melatonin or placebo for 12 weeks. Before and after trial, serum malondialdehyde (MDA), total antioxidant capacity (TAC), erythrocyte sedimentation rate (ESR), lipid profile, fasting blood sugar (FBS), and insulin levels were measured and disease activity was determined by disease activity score-28 (DAS-28).

RESULTS

Compared to the baseline, melatonin significantly decreased DAS-28, ESR, MDA, and LDL-C by 50.5%, 59%, 97%, and 13%, respectively (P<0.001) and significantly increased TAC by 89% (P=0.013) and HDL-C by 22% (P<0.001). After treatment, considerable differences were only seen between the two groups in serum MDA (P<0.001) and LDL-C (P=0.007) concentrations, adjusted for baseline measures. Moreover, there were no significant changes in DAS-28, ESR, TAC, triglyceride, total cholesterol, HDL-C, FBS, and insulin levels compared to placebo group (P>0.05).

CONCLUSIONS

Although melatonin supplementation had no beneficial effects on DAS-28, it could lower serum MDA and LDL-C levels. It seems that melatonin supplementation should not be used as a replace for routine drugs prescribed in RA treatment. Further investigations should be conducted to fully understand the effects of melatonin in RA. Key Points • Compared to baseline, melatonin significantly decreased DAS-28, ESR, MDA, and LDL-C and significantly increased TAC and HDL-C. • After treatment, considerable differences were only seen between melatonin and placebo groups in serum MDA and LDL-C concentrations. • After treatment, there were no significant changes in DAS-28, ESR, TAC, triglyceride, total cholesterol, HDL-C, FBS, and insulin levels compared to the placebo group.

Effects of melatonin supplementation on oxidative stress: a systematic review and meta-analysis of randomized controlled trials

Objectives

Previous studies showed that melatonin supplementation may suppress oxidative stress, however, the results have not been consistent. So, we conducted this meta-analysis to assess the precise relationship between melatonin supplementation and oxidative stress.

Methods

PubMed and Scopus were searched for randomized controlled trials that investigated the effect of melatonin supplementation on oxidative stress up to March 2020. Heterogeneity was assessed by Cochran’s Q test and I-square (I 2) statistic. Data were pooled using the random effect model and standardized mean difference (SMD) was considered as the summary effect size. Also, standard methods were used for assessment of sensitivity analysis and publication bias.

Results

We included 15 related articles and our findings indicated that melatonin supplementation significantly increased total antioxidant capacity (TAC) level (SMD: 1.03, 95% CI: 0.24, 1.81, p=0.011) and reduced protein carbonyl (PCO) (SMD: −1.78, 95% CI: −2.97, −0.58, p=0.004) and malondialdehyde (MDA) levels (SMD: −0.94, 95% CI: −1.48, −0.40, p=0.001). Additionally, there was considerable effect on TAC level by using ≥20 mg/d melatonin and in people under 35 years old. MDA level also decreased using dosage of below 20 mg/d and in people ≥35 years old.

Conclusions

The present study showed a promising effect of melatonin administration for reducing MDA, PCO, and increasing TAC levels. However, further studies especially with more attention to PCO level assessment are needed to confirm the findings of the present study in larger samples on different populations.

The roles of melatonin on kidney injury in obese and diabetic conditions

Obesity is a common and complex health problem worldwide and can induce the development of Type 2 diabetes. Chronic kidney disease (CKD) is a complication occurring as a result of obesity and diabetic conditions that lead to an increased mortality rate. There are several mechanisms and pathways contributing to kidney injury in obese and diabetic conditions. The expansion of adipocytes triggers proinflammatory cytokines release into blood circulation and bind with the receptors at the cell membranes of renal tissues leading to kidney injury. Obesity-mediated inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction are the important causes and progression of CKD. Melatonin (N-acetyl-5-methoxytryptamine) is a neuronal hormone that is synthesized by the pineal gland and plays an essential role in regulating several physiological functions in the human body. Moreover, melatonin has pleiotropic effects such as antioxidant, anti-inflammation, antiapoptosis. In this review, the relationship between obesity, diabetic condition, and kidney injury and the renoprotective effect of melatonin in obese and diabetic conditions from in vitro and in vivo studies have been summarized and discussed.

Role of melatonin in controlling angiogenesis under physiological and pathological conditions

Angiogenesis depends on proangiogenic and anti-angiogenic molecules that regulate endothelial cell proliferation and migration. Well-regulated angiogenesis plays a pivotal role in many physiological conditions such as reproduction and embryonic development, while abnormal angiogenesis is also the basis of a variety of pathological processes including tumor metastasis and atherosclerotic plaque formation. Melatonin has a variety of biological effects, including inhibition of tumor metastasis, stabilizing atherosclerotic plaques, and the regulation of seasonal reproductive rhythms, etc. During certain pathophysiological processes, melatonin exerts different functions depending on its ability to regulate angiogenesis. This review reveals that melatonin has different effects on neovascularization under different physiological and pathological conditions. In tumors, in age-related ocular diseases, and in a hypoxic environment, melatonin inhibits neovascularization in tissues, while in gastric ulcers, skin lesions, and some physiologic processes, it promotes angiogenesis. We also speculate that melatonin may inhibit the neovascularization in atherosclerotic plaques, thus preventing the initiation and development of atherosclerosis. Most studies suggest that these effects are related to the role of melatonin in regulating of vascular endothelial growth factor and its receptors, but the specific regulatory mechanisms remain disparate, which may lead to the differential effects of melatonin on angiogenesis under different conditions. In this review, we thus summarize some seemingly contradictory mechanisms by which melatonin controls angiogenesis under different pathological and physiological conditions, and urge that the regulatory mechanisms be further studied.

The Effects of Melatonin Supplementation on Parameters of Mental Health, Glycemic Control, Markers of Cardiometabolic Risk, and Oxidative Stress in Diabetic Hemodialysis Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVE

This study evaluated the effects of melatonin supplementation on parameters of mental health, glycemic control, markers of cardiometabolic risk, and oxidative stress in diabetic hemodialysis (HD) patients.

DESIGN

A randomized, double-blind, placebo-controlled clinical trial was conducted in 60 diabetic HD patients, 18-80 years of age. Participants were randomly divided into 2 groups to take either melatonin (2 x 5mg/day) (n = 30) or placebo (n = 30) 1 hour before bedtime for 12 weeks. The effects of melatonin on mental health, metabolic status, and gene expression related to metabolic status were assessed using multiple linear regression adjusting for age and BMI.

RESULTS

Melatonin supplementation significantly decreased Pittsburgh Sleep Quality Index (P = .007), Beck Depression Inventory index (P = .001), and Beck Anxiety Inventory index (P = .01) compared with the placebo. Additionally, melatonin administration significantly reduced fasting plasma glucose (β = -21.77 mg/dL, 95% CI -33.22 to -10.33, P < .001), serum insulin levels (β = -1.89 μIU/mL, 95% CI -3.34 to -0.45, P = .01), and homeostasis model of assessment-insulin resistance (β = -1.45, 95% CI -2.10 to -0.80, P < .001), and significantly increased the quantitative insulin sensitivity check index (β = 0.01, 95% CI 0.007-0.02, P < .001) compared with placebo treated subjects. In addition, melatonin administration resulted in a significant reduction in serum high sensitivity C-reactive protein (β = -1.92 mg/L, 95% CI -3.02 to -0.83, P = .001) and plasma malondialdehyde (β = -0.21 μmol/L, 95% CI -0.36 to -0.06, P = .005); also, significant rises in plasma total antioxidant capacity (β = 253.87 mmol/L, 95% CI 189.18-318.56, P < .001) and nitric oxide levels (β = 2.99 μmol/L, 95% CI 0.71-5.28, P = .01) were observed compared with the placebo.

CONCLUSION

Overall, melatonin supplementation for 12 weeks to diabetic HD patients had beneficial effects on mental health, glycemic control, inflammatory markers, and oxidative stress.

The effects of antibiotics and melatonin on hepato-intestinal inflammation and gut microbial dysbiosis induced by a short-term high-fat diet consumption in rats

High-fat diet (HFD) consumption leads to metabolic disorders, gastrointestinal dysfunction and intestinal dysbiosis. Antibiotics also disrupt the composition of intestinal microbiota. The aim of the present study was to investigate the impact of a short-term feeding with HFD on oxidative status, enteric microbiota, intestinal motility and the effects of antibiotics and/or melatonin treatments on diet-induced hepato-intestinal dysfunction and inflammation. Male Sprague-Dawley rats were pair-fed with either standard chow or HFD (45 % fat) and were given tap water or melatonin (4 mg/kg per d) or melatonin plus antibiotics (ABX; neomycin, ampicillin, metronidazole; each 1 g/l) in drinking water for 2 weeks. On the 14th day, colonic motility was measured and the next day intestinal transit was assessed using charcoal propagation. Trunk blood, liver and intestine samples were removed for biochemical and histopathological evaluations, and faeces were collected for microbiota analysis. A 2-week HFD feeding increased blood glucose level and perirenal fat weight, induced low-level hepatic and intestinal inflammation, delayed intestinal transit, led to deterioration of epithelial tight junctions and overgrowth of colonic bacteria. Melatonin intake in HFD-fed rats reduced ileal inflammation, colonic motility and perirenal fat accumulation. ABX abolished increases in fat accumulation and blood glucose, reduced ileal oxidative damage, suppressed HFD-induced overgrowth in colonic bacteria, and reversed HFD-induced delay in intestinal transit; however, hepatic neutrophil accumulation, hepatic injury and dysfunction were further enhanced. In conclusion, the results demonstrate that even a short-term HFD ingestion results in hepato-intestinal inflammatory state and alterations in bacterial populations, which may be worsened with antibiotic intake, but alleviated by melatonin.

Melatonin Supplementation Attenuates the Pro-Inflammatory Adipokines Expression in Visceral Fat from Obese Mice Induced by A High-Fat Diet

Obesity is defined as a condition of abnormal or excessive fat accumulation in white adipose tissue that results from the exacerbated consumption of calories associated with low energy expenditure. Fat accumulation in both adipose tissue and other organs contributes to a systemic inflammation leading to the development of metabolic disorders such as type 2 diabetes, hypertension, and dyslipidemia. Melatonin is a potent antioxidant and improves inflammatory processes and energy metabolism. Using male mice fed a high-fat diet (HFD—59% fat from lard and soybean oil; 9:1) as an obesity model, we investigated the effects of melatonin supplementation on the prevention of obesity-associated complications through an analysis of plasma biochemical profile, body and fat depots mass, adipocytes size and inflammatory cytokines expression in epididymal (EPI) adipose depot. Melatonin prevented a gain of body weight and fat depot mass as well as adipocyte hypertrophy. Melatonin also reversed the increase of total cholesterol, triglycerides and LDL-cholesterol. In addition, this neurohormone was effective in completely decreasing the inflammatory cytokines leptin and resistin in plasma. In the EPI depot, melatonin reversed the increase of leptin, Il-6, Mcp-1 and Tnf-α triggered by obesity. These data allow us to infer that melatonin presents an anti-obesity effect since it acts to prevent the progression of pro-inflammatory markers in the epididymal adipose tissue together with a reduction in adiposity.

Redox homeostasis in a rodent model of circadian disruption: Effect of melatonin supplementation

Continuous light or dark photoperiods are the leading cause of disruption in the circadian rhythm of day-night cycle. The purpose of this study was to understand the cellular redox balance in a model of circadian disrupted rat model and determine the effect of melatonin supplementation. Young male Wistar rats were randomly divided into five groups (n = 4). Group (I): normal day-night (12 h:12 h) cycle, Group (II): normal rats treated with melatonin, Group (III): rats subjected to continuous light exposure (CLE), Group (IV): CLE rats treated with melatonin, and Group (V) Rats subjected to continuous dark. Melatonin (10 mg/kg) was administered orally at dusk to the Group (II) & (IV). Rats were sacrificed after 10 days of treatment and biomarkers of oxidative stress were evaluated. Results demonstrated significant (p < 0.05) increase of malondialdehyde (MDA), plasma membrane redox system (PMRS), protein carbonyl oxidation (PCO), advanced oxidation protein products (AOPPs), and advanced glycation end products (AGEs) during CLE. A significantly (p < 0.05) decreased level of reduced glutathione (GSH) and ferric reducing antioxidant potential in plasma (FRAP) was also observed during CLE. Treatment with melatonin in CLE rats showed reduced level of MDA, PMRS, PCO, AOPPs and AGEs while GSH and FRAP activity were increased. During continuous dark exposure (CDE) the biomarkers of oxidative stress were attenuated compared to control. Supplementation of melatonin could be a promising strategy to maintain redox homeostasis during prolonged condition of light exposure and other conditions of redox imbalance.

Melatonin and Parkinson Disease: Current Status and Future Perspectives for Molecular Mechanisms

Parkinson disease (PD) is a chronic and neurodegenerative disease with motor and nonmotor symptoms. Multiple pathways are involved in the pathophysiology of PD, including apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and changes in the neurotransmitters. Preclinical and clinical studies have shown that melatonin supplementation is an appropriate therapy for PD. Administration of melatonin leads to inhibition of some pathways related to apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and dopamine loss in PD. In addition, melatonin improves some nonmotor symptom in patients with PD. Limited studies, however, have evaluated the role of melatonin on molecular mechanisms and clinical symptoms in PD. This review summarizes what is known regarding the impact of melatonin on PD in preclinical and clinical studies.

The effect of melatonin supplementation on lipid profile and anthropometric indices: A systematic review and meta-analysis of clinical trials

BACKGROUND

Epidemiological evidence suggests that melatonin has some effects on the serum lipid. However, these results are controversial. The aim of this systematic review and meta-analysis is to examine the effect of melatonin supplement on dyslipidemia and anthropometric indices.

METHODS

We searched electronic databases including Medline, Embase, Scopus, Web of Science and Cochrane Library up to Des 2018 without any language restriction. To compare the effects of melatonin with placebo, differences in standardized means difference (SMD) with 95% confidence intervals (95% CI) were pooled using random effects model.

RESULTS

Twelve trials including 641 participants included in meta-analysis finally. The dose of melatonin was reported at 0.8-30 mg. Comparing with the control group, melatonin may improve low density lipoprotein cholesterol (LDL-C) (-0.31 mmol/L, 95% CI (-0.61, 0.01), P = 0.049, I2 = 42%) and triglyceride (TG) level (SMD = -0.45 mmol/L; 95% CI, -0.77, -0.13, P = 0.006, I2 = 47%). No significant effect of melatonin on high density lipoprotein cholesterol (HDL-C) and anthropometric indices was found.

CONCLUSIONS

The results of our systematic review and Meta-analyzes showed that supplementation of melatonin could be effective in improving lipid parameters and should be considered in the prevention of cardiovascular disease, although the effect of this supplement on anthropometric indices needs further investigation.

Melatonin Inhibits in Vitro Smooth Muscle Cell Inflammation and Proliferation and Atherosclerosis in Apolipoprotein E-Deficient Mice

Chronic inflammation and proliferation play important roles in atherosclerosis progression. This study aimed to identify the mechanisms responsible for the anti-inflammatory and antiproliferative effects of melatonin on tumor necrosis factor-α (TNF-α)- and platelet-derived growth factor-BB (PDGF-BB)-treated rat aortic smooth muscle cells (RASMCs). Melatonin reduced TNF-α-induced RASMC inflammation by decreasing vascular cell adhesion molecule-1 (VCAM-1) expression and nuclear factor-kappa B (NF-κB) P65 activity by inhibiting P38 mitogen-activated protein kinase phosphorylation ( P < 0.05). Additionally, melatonin inhibited PDGF-BB-induced RASMC proliferation by reducing mammalian target of rapamycin (mTOR) phosphorylation ( P < 0.05) but not migration in vitro. Melatonin also reduced TNF-α- and PDGF-BB-induced reactive oxygen species (ROS) production ( P < 0.05). Furthermore, melatonin treatment (prevention and treatment groups) significantly repressed high cholesterol diet-stimulated atherosclerotic lesions in vivo (19.59 ± 4.11%, 20.28 ± 5.63%, 32.26 ± 12.06%, respectively, P < 0.05). Taken together, the present study demonstrated that melatonin attenuated TNF-α-induced RASMC inflammation and PDGF-BB-induced RASMC proliferation in cells and reduced atherosclerotic lesions in mice. These results showed that melatonin has anti-inflammatory and antiproliferative properties and may be a novel therapeutic target in atherosclerosis.

Melatonin Supplementation Decreases Hypertrophic Obesity and Inflammation Induced by High-Fat Diet in Mice

Obesity results from critical periods of positive energy balance characterized by caloric intake greater than energy expenditure. This disbalance promotes adipose tissue dysfunction which is related to other comorbidities. Melatonin is a low-cost therapeutic agent and studies indicate that its use may improve obesity-related disorders. To evaluate if the melatonin is efficient in delaying or even blocking the damages caused by excessive ingestion of a high-fat diet (HFD) in mice, as well as improving the inflammatory profile triggered by obesity herein, male C57BL/6 mice of 8 weeks were induced to obesity by a HFD and treated for 10 weeks with melatonin. The results demonstrate that melatonin supplementation attenuated serum triglyceride levels and total and LDL cholesterol and prevented body mass gain through a decreased lipogenesis rate and increased lipolytic capacity in white adipocytes, with a concomitant increment in oxygen consumption and Pgc1a and Prdm16 expression. Altogether, these effects prevented adipocyte hypertrophy caused by HFD and reflected in decreased adiposity. Finally, melatonin supplementation reduced the crown-like-structure (CLS) formation, characteristic of the inflammatory process by macrophage infiltration into white adipose tissue of obese subjects, as well as decreased the gene expression of inflammation-related factors, such as leptin and MCP1. Thus, the melatonin can be considered a potential therapeutic agent to attenuate the metabolic and inflammatory disorders triggered by obesity.

The effect of melatonin on the lipid levels in menopausal women: A double-blind, controlled, clinical trial

BACKGROUND

Cardiovascular diseases are the major public health problem in many countries and are responsible for more than half of the deaths in above 50-year-old women. The most common curable risk factor of these disorders is hypoestrogenemia resulting from menopause. The present study aimed to investigate the effect of melatonin on plasma lipid levels in menopausal women.

MATERIALS AND METHODS

The present double-blind, placebo-controlled, clinical trial was conducted in 2013-2014 on 240 menopausal women between 40 and 60 years old referring to the Gynecology and obstetrics clinics of Shiraz University of Medical Sciences who were randomly divided into two groups. The intervention group received 3 mg melatonin tablets and the control group received the placebo for 3 months. The data were gathered using the demographic information questionnaire and lipid profile test before and 3 months after the intervention. Then, the data were analyzed through the SPSS statistical software (version 16). The repeated measures analysis of variance, the least significant difference, the independent-sample t, the Chi-square, and Fisher's exact tests were done for data analysis.

RESULTS

The two study groups were similar regarding the demographic and clinical variables at the beginning of the study. In the melatonin group, the amount of triglyceride increased from 140.34 ± 48.29 before the study to 151.24 ± 54.60 3 months after the intervention and no significant difference was observed between the two groups in this regard (confidence interval [CI] = 95%, P > 0.05). In addition, no significant difference was found between the two groups concerning low-density lipoprotein cholesterol level (CI = 95%, P = 0.125).

CONCLUSION

Melatonin was not effective in reduction of lipid levels. However, further controlled studies are needed to be conducted on the issue.

Melatonin alleviates liver steatosis induced by prenatal dexamethasone exposure and postnatal high-fat diet

Prenatal exposure to glucocorticoids is associated with negative health consequences for the offspring that persist into adulthood, including liver steatosis. Melatonin has previously been demonstrated to suppress liver steatosis and oxidative stress in humans with non-alcoholic fatty liver disease and in animal models of obesity. The present study aimed to determine whether melatonin protects against liver steatosis induced by prenatal dexamethasone exposure followed by postnatal high-fat diet. Pregnant Sprague-Dawley rats at gestational days 14-21 were administered dexamethasone (0.1 mg/kg/day) or saline via intraperitoneal injection. The offspring were then divided into five groups, as follows: Vehicle, postnatal high-fat diet (VHF), prenatal dexamethasone exposure (DEX), prenatal dexamethasone exposure + postnatal high-fat diet (DHF), and prenatal dexamethasone exposure + postnatal high-fat diet + melatonin (DHFM) group. Following vehicle or dexamethasone exposure of the maternal rats, the offspring rats in the VHF, DHF and DHFM groups received a high-fat diet (58% fat) between weaning and 6 months of age. In the DHFM group, melatonin was administered to the mothers from gestational days 14-21 until weaning. The offspring continued to receive melatonin until they were sacrificed at 6 months old. Oil Red O staining demonstrated stronger intensity in the DHF group compared with that in the other four groups. Western blot analysis also revealed higher levels of cleaved caspase-3, tumor necrosis factor-α (TNF-α), suppressor of cytokine signaling 3 (SOCS3) and malondialdehyde (MDA), as well as reduced expression of manganese superoxide dismutase (MnSOD) and phosphoinositide 3-kinase (PI3K) in the DHF group compared with the vehicle and DHFM groups. In addition, melatonin reduced the Oil Red O staining intensity and the levels of cleaved caspase-3, TNF-α, SOCS3 and MDA, while it increased the MnSOD and PI3K levels, in the DHFM group compared with the DHF group. In conclusion, postnatal high-fat diet aggravated the prenatal dexamethasone-induced liver steatosis in adult rat offspring via inflammation, oxidative stress and cellular apoptosis, which may be ameliorated by prenatal melatonin therapy.

Anti-Inflammatory Effects of Melatonin in Obesity and Hypertension

PURPOSE OF REVIEW

Here, we review the known relations between hypertension and obesity to inflammation and postulate the endogenous protective effect of melatonin and its potential as a therapeutic agent. We will describe the multiple effects of melatonin on blood pressure, adiposity, body weight, and focus on mitochondrial-related anti-inflammatory and antioxidant protective effects.

RECENT FINDINGS

Hypertension and obesity are usually associated with systemic and tissular inflammation. The progressive affection of target-organs involves multiple mediators of inflammation, most of them redundant, which make anti-inflammatory strategies ineffective. Melatonin reduces blood pressure, body weight, and inflammation. The mechanisms of action of this ancient molecule of protection involve multiple levels of action, from subcellular to intercellular. Mitochondria is a key inflammatory element in vascular and adipose tissue and a potential pharmacological target. Melatonin protects against mitochondrial dysfunction. Melatonin reduces blood pressure and adipose tissue dysfunction by multiple anti-inflammatory/antioxidant actions and provides potent protection against mitochondria-mediated injury in hypertension and obesity. This inexpensive and multitarget molecule has great therapeutic potential against both epidemic diseases.

Effect of melatonin different time administration on the development of diet-induced obesity in rats

In recent years much attention has been paid for study of the melatonin use possibilities for improving obesity comorbidities. The aim of our study was to determine the influence of melatonin different time treatment on body weight changes of dietinduced obesity in rats. The administration by gavage of melatonin in dose 30 mg/kg for 7 weeks had the potential to decrease visceral fat weight, Lee index (both after morning and evening treatment) and body weight gain rate (only after evening dose).

Alterations in Metabolism and Diurnal Rhythms following Bilateral Surgical Removal of the Superior Cervical Ganglia in Rats

Mammalian circadian rhythms are controlled by a master pacemaker located in the suprachiasmatic nuclei (SCN), which is synchronized to the environment by photic and nonphotic stimuli. One of the main functions of the SCN is to regulate peripheral oscillators to set temporal variations in the homeostatic control of physiology and metabolism. In this sense, the SCN coordinate the activity/rest and feeding/fasting rhythms setting the timing of food intake, energy expenditure, thermogenesis, and active and basal metabolism. One of the major time cues to the periphery is the nocturnal melatonin, which is synthesized and secreted by the pineal gland. Under SCN control, arylalkylamine N-acetyltransferase (AA-NAT)-the main enzyme regulating melatonin synthesis in vertebrates-is activated at night by sympathetic innervation that includes the superior cervical ganglia (SCG). Bilateral surgical removal of the superior cervical ganglia (SCGx) is considered a reliable procedure to completely prevent the nocturnal AA-NAT activation, irreversibly suppressing melatonin rhythmicity. In the present work, we studied the effects of SCGx on rat metabolic parameters and diurnal rhythms of feeding and locomotor activity. We found a significant difference between SCGx and sham-operated rats in metabolic variables such as an increased body weight/food intake ratio, increased adipose tissue, and decreased glycemia with a normal glucose tolerance. An analysis of locomotor activity and feeding rhythms showed an increased daytime (lights on) activity (including food consumption) in the SCGx group. These alterations suggest that superior cervical ganglia-related feedback mechanisms play a role in SCN-periphery phase coordination and that SCGx is a valid model without brain-invasive surgery to explore how sympathetic innervation affects daily (24 h) patterns of activity, food consumption and, ultimately, its role in metabolism homeostasis.

Potential pleiotropic beneficial effects of adjuvant melatonergic treatment in posttraumatic stress disorder

Loss of circadian rhythmicity fundamentally affects the neuroendocrine, immune, and autonomic system, similar to chronic stress and may play a central role in the development of stress-related disorders. Recent articles have focused on the role of sleep and circadian disruption in the pathophysiology of posttraumatic stress disorder (PTSD), suggesting that chronodisruption plays a causal role in PTSD development. Direct and indirect human and animal PTSD research suggests circadian system-linked neuroendocrine, immune, metabolic and autonomic dysregulation, linking circadian misalignment to PTSD pathophysiology. Recent experimental findings also support a specific role of the fundamental synchronizing pineal hormone melatonin in mechanisms of sleep, cognition and memory, metabolism, pain, neuroimmunomodulation, stress endocrinology and physiology, circadian gene expression, oxidative stress and epigenetics, all processes affected in PTSD. In the current paper, we review available literature underpinning a potentially beneficiary role of an add-on melatonergic treatment in PTSD pathophysiology and PTSD-related symptoms. The literature is presented as a narrative review, providing an overview on the most important and clinically relevant publications. We conclude that adjuvant melatonergic treatment could provide a potentially promising treatment strategy in the management of PTSD and especially PTSD-related syndromes and comorbidities. Rigorous preclinical and clinical studies are needed to validate this hypothesis.

Beneficial effects of melatonin and alpha lipoic acid on lopinavir/ ritonavir-induced alterations in serum lipid and glucose levels of male albino rats

The use of lopinavir/ritonavir (LPV/r) has been associated with alterations in serum lipid and glucose levels. This study was designed to investigate the effects of melatonin (MT) and alpha lipoic acid (ALA) on LPV/r-induced changes in serum levels of triglycerides (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C) and glucose (GL) levels in male albino rats. Rats in group A1 (placebo control) and group A2 (solvent control) were orally treated with normal saline and 1% ethanol respectively. Groups B-F contained 15 rats each which were divided into 3 groups of 5 rats each. Rats in group B were orally treated with MT (10 mg kg-1/day), ALA (10 mg kg-1/day) and a combination of MT and ALA, accordingly. Rats in group C were orally treated with 22.9/5.71, 45.6/11.4 and 91.4/22.9 mg kg-1/day of LPV/r, accordingly. Rats in groups D-F were orally treated with MT (10 mg kg-1/ day), ALA (10 mg kg-1/day) and combined doses of ALA and MT before oral treatment with 22.9/5.71, 45.6/11.4 and 91.4/22.9 mg kg-1/day of LPV/r, accordingly. All rats were treated for 30 days and at the end of the drug treatment, the serum levels of lipid fractions and glucose were evaluated. Treatment with MT and ALA significantly (p<0.05) decreased baseline serum levels of TG, TC, VLDL-C, LDL-C and GL, but these parameters were significantly (p<0.05) increased in a dose-dependent manner in LPV/r-treated rats when compared to placebo control. Administration of MT and ALA prior to treatment with LPV/r significantly (p<0.05) decreased serum levels of TG, TC, VLDL-C, LDL-C and GL when compared to LPV/r-treated rats. However, decreases obtained in rats pretreated with combined doses of MT and ALA were significantly (p<0.05) different when compared to their individual doses. This study showed that MT and ALA can serve as remedies for LPV/r-induced alterations in serum lipid and glucose levels.

Inter-relationships of the chronobiotic, melatonin, with leptin and adiponectin: implications for obesity

Obesity and its medical complications represent a significant problem throughout the world. In recent decades, mechanisms underlying the progression of obesity have been intensively examined. The involvement of both the behavioral aspects, such as calorie-rich diet, low physical activity and sleep deprivation, and the intrinsic factors, including adipose tissue deregulation, chronic inflammation, oxidative stress, and chronodisruption, has been identified. The circadian disturbances of the adipose tissue endocrine function have been correlated with obesity. Leptin and adiponectin are adipokines strongly associated with glucose and lipid metabolism and with energy balance. Their synthesis and secretion display circadian rhythms that are disturbed in the obese state. Hyperleptinemia resulting in leptin resistance, and hypo-adiponectinemia have been linked to the pathophysiology of the obesity-related disorders. A deficiency of melatonin, one of the consequences of sleep deprivation, has also been demonstrated to correlate with obesity. Melatonin is a pineal secretory product involved in numerous actions, such as regulation of internal biological clocks and energy metabolism, and it functions as an antioxidant and as an anti-inflammatory agent. There exists a substantial amount of evidence supporting the beneficial effects of melatonin supplementation on obesity and its complications. In the current review, the results of studies related to the interactions between melatonin, and both leptin and adiponectin are discussed. Despite the existence of some inconsistencies, melatonin has been found to normalize the expression and secretion patterns of both adipokines. These results support the concept of melatonin as a potential therapeutic agent for obesity and related disorders.

The potential physiological crosstalk and interrelationship between two sovereign endogenous amines, melatonin and homocysteine

The antioxidant melatonin and the non-proteinogenic excitotoxic amino acid homocysteine (Hcy) are very distinct but related reciprocally to each other in their mode of action. The elevated Hcy level has been implicated in several disease pathologies ranging from cardio- and cerebro-vascular diseases to neurodegeneration owing largely to its free radical generating potency. Interestingly, melatonin administration potentially normalizes the elevated Hcy level, thereby protecting the cells from the undesired Hcy-induced excitotoxicity and cell death. However, the exact mechanism and between them remain obscure. Through literature survey we have found an indistinct but a vital link between melatonin and Hcy i.e., the existence of reciprocal regulation between them, and this aspect has been thoroughly described herein. In this review, we focus on all the possibilities of co-regulation of melatonin and Hcy at the level of their production and metabolism both in basal and in pathological conditions, and appraised the potential of melatonin in ameliorating homocysteinemia-induced cellular stresses. Also, we have summarized the differential mode of action of melatonin and Hcy on health and disease states.

Melatonin: a potential intervention for hepatic steatosis

Melatonin (N-acetyl-5-methoxytryptamine, MLT) is a neuroendocrine hormone, which is primarily synthesized by the pineal gland in vertebrates. Melatonin is a remarkable molecule with diverse biological and physiological actions and is involved in the regulation of various important functions such as circadian rhythm, energy metabolism, the reproductive system, the cardiovascular system, and the neuropsychiatric system. It also plays a role in disease by having anti-neoplastic and anti-osteoarthritic effects among others. Recently, research has focused on the roles of melatonin in oxidative stress, lipid metabolism, and hepatic steatosis and its potential therapeutic roles.

Melatonin and female hormone secretion in postmenopausal overweight women

Estrogen deficiency is considered to be the main cause of increased appetite and increased weight in postmenopausal women. In this period, reduced secretion of melatonin (MEL) was also observed. The aim of the study was to evaluate the secretion of melatonin, 17-β estradiol and follicle-stimulating hormone (FSH) in relation to body mass index (BMI) in pre- and postmenopausal women. The study included 90 women divided into three equal groups: group I (control)-women without menstrual disorders, group II-postmenopausal women without change in appetite and body weight, group III-postmenopausal women experiencing increased appetite and weight gain. In each patient, serum melatonin, 17-β-estradiol, FSH and urine a 6-sulfatoxymelatonin (aMT6s) were determined. Compared to the control group, the level of melatonin and estradiol was statistically lower. The FSH level was higher than in the groups of postmenopausal women. No significant correlation was found in all groups between the level of melatonin and the levels of estradiol and FSH. A negative correlation was found between aMT6s excretion and BMI, and a positive correlation between the level of FSH and BMI, mainly in overweight women. The obtained results indicate a significant effect of melatonin deficiency on the process of weight gain in postmenopausal women and justify its use in treatment of these disorders.

Melatonin normalizes clinical and biochemical parameters of mild inflammation in diet-induced metabolic syndrome in rats

The objective of this study was to evaluate the efficacy of melatonin to affect mild inflammation in the metabolic syndrome (MS) induced by a high-fat diet in rats. Adult Wistar male rats were divided into four groups (n = 16/group): (i) control diet (3% fat); (ii) high-fat (35%) diet; (iii) high-fat diet + melatonin; and (iv) melatonin. Rats had free access to high-fat or control chow and one of the following drinking solutions for 10 wk: (a) tap water; (b) 25 μg/mL of melatonin. Plasma interleukin (IL)-1β, IL-4, IL-6, IL-10, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and C-reactive protein (CRP) were measured at two time intervals, that is, the middle of daylight period and the middle of the scotophase. In addition, a number of somatic and metabolic components employed clinically to monitor the MS were measured. Melatonin decreased the augmented circulating levels of IL-1β, IL-6, TNF-α, IFN-γ, and CRP seen in obese rats and restored the depressed levels of IL-4 and IL-10. Rats fed with the high-fat diet showed significantly higher body weights and augmented systolic blood pressure from the third and fourth week onwards, respectively, melatonin effectively preventing these changes. In high-fat-fed rats, circulating low-density lipoprotein-cholesterol, total cholesterol, and triglyceride concentration augmented significantly, melatonin being effective to counteract these changes. Melatonin-treated rats showed a decreased insulin resistance, the highest values of plasma high-density lipoprotein-cholesterol, and the lowest values of plasma uric acid. The results indicate that melatonin is able to normalize the altered biochemical pro-inflammatory profile seen in rats fed with a high-fat diet.

Melatonin for prevention of metabolic side-effects of olanzapine in patients with first-episode schizophrenia: randomized double-blind placebo-controlled study

We aimed to determine the efficacy of melatonin 3 mg/day in prevention of olanzapine-induced metabolic side-effects. In a randomized double-blind placebo-controlled study, 48 patients with first-episode schizophrenia who were eligible for olanzapine treatment, were randomly assigned to olanzapine plus either melatonin 3 mg/day or matched placebo for eight weeks. Anthropometric and metabolic parameters as well as psychiatric symptoms using The Positive and Negative Syndrome Scale (PANSS) were assessed at baseline, week 4, and 8. Primary outcome measure was the change from baseline in weight at week 8. Data were analyzed using t-test, Mann-Whitney U test, and mixed-effects model. Thirty-six patients had at least one post-baseline measurement. At week eight, melatonin was associated with significantly less weight gain [mean difference (MD) = 3.2 kg, P = 0.023], increase in waist circumference [MD = 2.83 cm, P = 0.041] and triglyceride concentration [MD = 62 mg/dl, P = 0.090 (nearly significant)] than the placebo. Changes in cholesterol, insulin, and blood sugar concentrations did not differ significantly between the two groups. Patients in the melatonin group experienced significantly more reduction in their PANSS scores [MD = 12.9 points, P = 0.014] than the placebo group. No serious adverse events were reported. To summarize, in patients treated with olanzapine, short-term melatonin treatment attenuates weight gain, abdominal obesity, and hypertriglyceridemia. It might also provide additional benefit for treatment of psychosis. The study was registered in the ClinicalTrials.gov (

REGISTRATION NUMBER

NCT01593774).

Melatonin administration decreases adipogenesis in the liver of ob/ob mice through autophagy modulation

Despite efforts to curb the incidence of obesity and its comorbidities, this condition remains the fifth leading cause of death worldwide. To identify ways to reduce this global effect, we investigated the actions of daily melatonin administration on oxidative stress parameters and autophagic processes as a possible treatment of obesity in ob/ob mice. The involvement of melatonin in many physiological functions, such as the regulation of seasonal body weight variation, glucose uptake, or adiposity, and the role of this indoleamine as an essential antioxidant, has become the focus of numerous anti-obesity studies. Here, we examined the oxidative status in the livers of obese melatonin-treated and untreated mice, observing a decrease in the oxidative stress levels through elevated catalase activity. ROS-mediated autophagy was downregulated in the liver of melatonin-treated animals and was accompanied by significant accumulation of p62. Autophagy is closely associated with adipogenesis; in this study, we report that melatonin-treated obese mice also showed reduced adiposity, as demonstrated by diminished body weight and reduced peroxisome proliferator-activated receptor gamma expression. Based on these factors, it is reasonable to assume that oxidative stress and autophagy play important roles in obesity, and therefore, melatonin could be an interesting target molecule for the development of a potential therapeutic agent to curb body weight.

Melatonin and its atheroprotective effects: a review

Atherosclerosis is a chronic vascular disease in which oxidative stress and inflammation are commonly implicated as major causative factors. Identification of novel strategies that contribute to plaque stabilization or inhibition represents a continuing challenge for the medical community. The evidence from the last decade highlights that melatonin influences the cardiovascular system, but its mechanisms of action have not been definitively clarified. Melatonin has atheroprotective effects by acting on different pathogenic signaling processes; these result from its direct free radical scavenger activity, its indirect antioxidant properties and its anti-inflammatory actions. In this review, we summarize the many pieces of the puzzle which identified molecular targets for prevention and therapy against the atherosclerotic pathogenic processes and we evaluate the data documenting that melatonin treatment has important actions that protect against atherosclerosis and atherosclerosis-related cardiovascular diseases.

Melatonin ameliorates vascular endothelial dysfunction, inflammation, and atherosclerosis by suppressing the TLR4/NF-κB system in high-fat-fed rabbits

Vascular endothelial dysfunction (VED) and inflammation contribute to the initiation and progression of atherosclerosis. Melatonin (MLT) normalizes lipid profile, improves endothelial function, and possesses anti-inflammatory properties. However, the precise mechanisms are still unclear. This study investigated whether MLT could ameliorate VED, inflammation, and atherosclerosis by suppressing the Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) system in high-fat-fed rabbits. Rabbits were randomly divided into three groups that received a standard diet (control group), high-cholesterol diet (atherosclerosis group), or high-cholesterol diet plus 10 mg/kg/day MLT (MLT group) for 12 wk. After treatment, high-fat diet significantly increased serum lipid and inflammatory markers in rabbits in atherosclerosis group compared with that in control group. In addition, high-fat diet also induced VED and typical atherosclerotic plaque formation and increased intima/media thickness ratio, which were significantly improved by MLT therapy as demonstrated in MLT group. Histological and immunoblot analysis further showed that high-fat diet enhanced the expressions of TLR4, myeloid differentiation primary response protein (MyD88), and NF-κB p65, but decreased inhibitor of NF-κB (IκB) expression. By contrast, MLT therapy decreased the expressions of TLR4, MyD88, and NF-κB p65 and increased IκB expression. This study has demonstrated that MLT ameliorates lipid metabolism, VED, and inflammation and inhibits the progression of atherosclerosis in high-fat-fed rabbits. Moreover, our study indicates for the first time that suppression of the TLR4/NF-κB system in local vasculature with atherosclerotic damage is important for the protective effects of MLT.

Insulin and IGF1 enhance IL-17-induced chemokine expression through a GSK3B-dependent mechanism: a new target for melatonin's anti-inflammatory action

Obesity is a chronic inflammation with increased serum levels of insulin, insulin-like growth factor 1 (IGF1), and interleukin-17 (IL-17). The objective of this study was to test a hypothesis that insulin and IGF1 enhance IL-17-induced expression of inflammatory chemokines/cytokines through a glycogen synthase kinase 3β (GSK3B)-dependent mechanism, which can be inhibited by melatonin. We found that insulin/IGF1 and lithium chloride enhanced IL-17-induced expression of C-X-C motif ligand 1 (Cxcl1) and C-C motif ligand 20 (Ccl20) in the Gsk3b(+/+) , but not in Gsk3b(-/-) mouse embryonic fibroblast (MEF) cells. IL-17 induced higher levels of Cxcl1 and Ccl20 in the Gsk3b(-/-) MEF cells, compared with the Gsk3b(+/+) MEF cells. Insulin and IGF1 activated Akt to phosphorylate GSK3B at serine 9, thus inhibiting GSK3B activity. Melatonin inhibited Akt activation, thus decreasing P-GSK3B at serine 9 (i.e., increasing GSK3B activity) and subsequently inhibiting expression of Cxcl1 and Ccl20 that was induced either by IL-17 alone or by a combination of insulin and IL-17. Melatonin's inhibitory effects were only observed in the Gsk3b(+/+) , but in not Gsk3b(-/-) MEF cells. Melatonin also inhibited expression of Cxcl1, Ccl20, and Il-6 that was induced by a combination of insulin and IL-17 in the mouse prostatic tissues. Further, nighttime human blood, which contained high physiologic levels of melatonin, decreased expression of Cxcl1, Ccl20, and Il-6 in the PC3 human prostate cancer xenograft tumors. Our data support our hypothesis and suggest that melatonin may be used to dampen IL-17-mediated inflammation that is enhanced by the increased levels of insulin and IGF1 in obesity.

Obesity-related dysfunction of the aorta and prevention by melatonin treatment in ob/ob mice

In this study, we hypothesized that melatonin administration can minimize alterations in aorta morphology in an animal model of obesity (ob/ob mice). The animals were divided into four groups: (i) control lean mice, (ii) control lean mice treated with melatonin, (iii) ob/ob mice and (iv) ob/ob mice treated with melatonin. The synthetic melatonin was dissolved in 1% ethanol and added to the drinking water from postnatal week 5-13 at a final dose of 100 mg/kg body weight/day. Compared with the obese mice, melatonin intake was associated with a significant decrease in body weight and water consumption. Histological analysis showed that the aortic wall of ob/ob mice had a high Tunica media/lumen ratio and that the elastic fibers in the media layer appeared disrupted and degraded. Moreover, the aorta of ob/ob mice displayed a higher degree of collagen accumulation in the Tunica media compared to the normal aorta. The aorta of ob/ob mice treated with melatonin had a lower Tunica media/lumen ratio and collagen accumulation in comparison with untreated ob/ob mice. Our results showed that whereas melatonin had no apparent histological effects on the aorta in lean mice with normal weight, its administration in ob/ob mice can lead to a reduction in body weight and can ameliorate aorta histopathological dysfunction. This experimental study indicates an apparent protective role for melatonin on the aorta in obesity and melatonin could possibly be an effective tool in the management of obesity-related vascular complications.

Seasonal differences in melatonin concentrations and heart rates during sleep in obese subjects in Japan

During the past several decades, obesity has been increasing globally. In Japan, obesity is defined by a BMI of 25 kg/m² or over; 28.6 % of men and 20.6 % of women are obese. Obese people have an increased incidence of developing cardiovascular, renal, and hormonal diseases and sleep disorders. Obese people also have shortened sleep durations. We investigated seasonal differences in melatonin concentrations, heart rates, and heart rate variability during sleep in obese subjects in Japan. Five obese (BMI, 32.0 ± 4.9 kg/m²) and five non-obese (BMI, 23.2 ± 2.9 kg/m²) men participated in this study in the summer and winter. Electrocardiograms were measured continuously overnight in a climatic chamber at 26 °C with a relative humidity of 50 %. Saliva samples for melatonin were collected at 2300 hours, 0200 hours, and 0600 hours. We found that melatonin concentrations during sleep in obese subjects were significantly lower than those in non-obese subjects in the winter. Heart rate during sleep in winter was significantly higher than that in summer in both obese and non-obese subjects. Heart rate variability was not significantly different in the summer and winter in both obese and non-obese subjects. Our results show that decreased nocturnal melatonin concentrations during winter in obese men may be related to higher heart rates, and this may suggest that obese men are at an increased risk of a cardiovascular incident during sleep, especially in the winter.

Melatonin can improve insulin resistance and aging-induced pancreas alterations in senescence-accelerated prone male mice (SAMP8)

The aim of the present study was to investigate the effect of aging on several parameters related to glucose homeostasis and insulin resistance in pancreas and how melatonin administration could affect these parameters. Pancreas samples were obtained from two types of male mice models: senescence-accelerated prone (SAMP8) and senescence-accelerated-resistant mice (SAMR1). Insulin levels in plasma were increased with aging in both SAMP8 and SAMR1 mice, whereas insulin content in pancreas was decreased with aging in SAMP8 and increased in SAMR1 mice. Expressions of glucagon and GLUT2 messenger RNAs (mRNAs) were increased with aging in SAMP8 mice, and no differences were observed in somatostatin and insulin mRNA expressions. Furthermore, aging decreased also the expressions of Pdx-1, FoxO 1, FoxO 3A and Sirt1 in pancreatic SAMP8 samples. Pdx-1 was decreased in SAMR1 mice, but no differences were observed in the rest of parameters on these mice strains. Treatment with melatonin was able to decrease plasma insulin levels and to increase its pancreatic content in SAMP8 mice. In SAMR1, insulin pancreatic content and plasma levels were decreased. HOMA-IR was decreased with melatonin treatment in both strains of animals. On the other hand, in SAMP8 mice, treatment decreased the expression of glucagon, GLUT2, somatostatin and insulin mRNA. Furthermore, it was also able to increase the expression of Sirt1, Pdx-1 and FoxO 3A. According to these results, aging is associated with significant alterations in the relative expression of pancreatic genes associated to glucose metabolism. This has been especially observed in SAMP8 mice. Melatonin administration was able to improve pancreatic function in old SAMP8 mice and to reduce HOMA-IR improving their insulin physiology and glucose metabolism.

Melatonin may curtail the metabolic syndrome: studies on initial and fully established fructose-induced metabolic syndrome in rats

To examine the effect of melatonin given to rats simultaneously with fructose on initial and fully developed metabolic syndrome, male Wistar rats had free access to chow and 5% or 10% fructose drinking solution for 8 weeks. As compared to controls, systolic blood pressure augmented significantly under both treatments whereas excessive body weight was seen in rats receiving the 10% fructose only. Rats drinking 5% fructose showed a greater tolerance to a glucose load while rats having access to a 10% fructose drinking solution exhibited the expected impaired glucose tolerance found in the metabolic syndrome. Circulating triglyceride and low density lipoproteins-cholesterol (LDL-c) concentration augmented significantly in rats showing a fully developed metabolic syndrome only, while high blood cholesterol levels were found at both stages examined. Melatonin (25 μg/mL drinking solution) counteracted the changes in body weight and systolic blood pressure found in rats administered with fructose. Melatonin decreased the abnormal hyperglycemia seen after a glucose load in 10% fructose-treated rats but it did not modify the greater tolerance to glucose observed in animals drinking 5% fructose. Melatonin also counteracted the changes in plasma LDL-c, triglyceride and cholesterol levels and decreased plasma uric acid levels. The results underline a possible therapeutical role of melatonin in the metabolic syndrome, both at initial and established phases.

Melatonin treatment protects liver of Zucker rats after ischemia/reperfusion by diminishing oxidative stress and apoptosis

Fatty livers occur in up to 20% of potential liver donors and increase cellular injury during the ischemia/reperfusion phase, so any intervention that could enable a better outcome of grafts for liver transplantation would be very useful. The effect of melatonin on liver ischemia/reperfusion injury in a rat model of obesity and hepatic steatosis has been investigated. Forty fa/fa Zucker rats were divided in 4 groups. 3 groups were subjected to 35 min of warm hepatic ischemia and 36 h of reperfusion. One experimental group remained untreated and 2 were given 10mg/kg melatonin intraperitoneally or orally. Another group was sham-operated. Plasma ALT, AST and hepatic content of ATP, MDA, hydroxyalkenals, NOx metabolites, antioxidant enzyme activity, caspase-9 and DNA fragmentation were determined in the liver. The expression of iNOS, eNOS, Bcl2, Bax, Bad and AIF were determined by RT-PCR Melatonin was effective at decreasing liver injury by both ways as assessed by liver transaminases, markers of apoptosis, of oxidative stress and improved liver ATP content. Melatonin administration decreased the activities or levels of most of the parameters measured in a beneficial way, and our study identified also some of the mechanisms of protection. We conclude that administration of melatonin improved liver function, as well as markers of pro/antioxidant status and apoptosis following ischemia/reperfusion in obese rats with fatty liver. These data suggest that this substance could improve outcome in patients undergoing liver transplantation who receive a fatty liver implant and suggest the need of clinical trials with it in liver transplantation.

Melatonin and the metabolic syndrome: a tool for effective therapy in obesity-associated abnormalities?

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities associated with increased risk for cardiovascular diseases. Apart from its powerful antioxidant properties, the pineal gland hormone melatonin has recently attracted the interest of various investigators as a multifunctional molecule. Melatonin has been shown to have beneficial effects in cardiovascular disorders including ischaemic heart disease and hypertension. However, its role in cardiovascular risk factors including obesity and other related metabolic abnormalities is not yet established, particularly in humans. New emerging data show that melatonin may play an important role in body weight regulation and energy metabolism. This review will address the role of melatonin in the MetS focusing on its effects in obesity, insulin resistance and leptin resistance. The overall findings suggest that melatonin should be exploited as a therapeutic tool to prevent or reverse the harmful effects of obesity and its related metabolic disorders.