Long-term melatonin administration increases polyunsaturated fatty acid percentage in plasma lipids of hypercholesterolemic rats

Melatonin ameliorates myocardial infarction in obese diabetic individuals: The possible involvement of macrophage apoptotic factors

In recent days, the hike in obesity-mediated epidemics across the globe and the prevalence of obesity-induced cardiovascular disease has become one of the chief grounds for morbidity and mortality. This epidemic-driven detrimental events in the cardiac tissues start with the altered distribution and metabolism pattern of high-density lipoprotein and low-density lipoprotein (LDL) leading to cholesterol (oxidized LDL) deposition on the arterial wall and atherosclerotic plaque generation, followed by vascular spasms and infarction. Subsequently, obesity-triggered metabolic malfunctions induce free radical generation which may further trigger pro-inflammatory signaling and nuclear factor kappa-light-chain-enhancer of activated B cells transcriptional factor, thus inducing interferon-gamma, tumor necrosis factor-alpha, and inducible nitric oxide synthase. This terrifying cardiomyopathy can be further aggravated in type 2 diabetes mellitus, thereby making obese diabetic patients prone toward the development of myocardial infarction (MI) or stroke in comparison to their nondiabetic counterparts. The accelerated oxidative stress and pro-inflammatory response induced cardiomyocyte hypertrophy, followed by apoptosis in obese diabetic individuals, causing progression of athero-thrombotic vascular disease. Being an efficient antioxidative and anti-inflammatory indolamine, melatonin effectively inhibits lipid peroxidation, pro-inflammatory reactions, thereby resolving free radical-induced myocardial damages along with maintaining antioxidant reservoir to preserve cardiovascular integrity. Prolonged melatonin treatment maintains balanced body weight and serum total cholesterol concentration by inhibiting cholesterol synthesis and promoting cholesterol catabolism. Additionally, melatonin promotes macrophage polarization toward the anti-inflammatory state, providing a proper shield during the recovery period. Therefore, the protective role of melatonin in maintaining the lipid metabolism homeostasis and blocking the atherosclerotic plaque rupture could be targeted as the possible therapeutic strategy for the management of obesity-induced acute MI. This review aimed at orchestrating the efficacy of melatonin in ameliorating irrevocable oxidative cardiovascular damage induced by the obesity-diabetes correlation.

Evidence for the Benefits of Melatonin in Cardiovascular Disease

The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Mechanisms of Melatonin in Obesity: A Review

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

Clinical Application of Melatonin in the Treatment of Cardiovascular Diseases: Current Evidence and New Insights into the Cardioprotective and Cardiotherapeutic Properties

Cardiovascular diseases (CVDs) are the leading global cause of mortality and disability, tending to happen in younger individuals in developed countries. Despite improvements in medical treatments, the therapy and long-term prognosis of CVDs such as myocardial ischemia-reperfusion, atherosclerosis, heart failure, cardiac hypertrophy and remodeling, cardiomyopathy, coronary artery disease, myocardial infarction, and other CVDs threatening human life are not satisfactory enough. Therefore, many researchers are attempting to identify novel potential therapeutic methods for the treatment of CVDs. Melatonin is an anti-inflammatory and antioxidant agent with a wide range of therapeutic properties. Recently, several investigations have been carried out to evaluate its effectiveness and efficiency in CVDs therapy, focusing on mechanistic pathways. Herein, this review aims to summarize current findings of melatonin treatment for CVDs.

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 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.

Endothelium and its alterations in cardiovascular diseases: life style intervention

The endothelium, which forms the inner cellular lining of blood vessels and lymphatics, is a highly metabolically active organ that is involved in many physiopathological processes, including the control of vasomotor tone, barrier function, leukocyte adhesion, and trafficking and inflammation. In this review, we summarized and described the following: (i) endothelial cell function in physiological conditions and (ii) endothelial cell activation and dysfunction in the main cardiovascular diseases (such as atherosclerosis, and hypertension) and to diabetes, cigarette smoking, and aging physiological process. Finally, we presented the currently available evidence that supports the beneficial effects of physical activity and various dietary compounds on endothelial functions.

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 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.

Reactive oxygen species and the hypomotility of the gall bladder as targets for the treatment of gallstones with melatonin: a review

Free radical-mediated damage of the gall bladder epithelium predisposes to the development of both gall bladder inflammation and gallstone formation, which often coexist. Melatonin, a pineal and gut secretory product, due to its antioxidant activity along with its effect on the aging gall bladder myocytes, inhibits gallstone formation. Melatonin reduces the biliary levels of cholesterol by inhibiting cholesterol absorption across the intestinal epithelium and by increasing the conversion of cholesterol to bile acids. The incidence of gallstones is increasing and is expected to rise dramatically with the increase in the longevity and the risk factors such as obesity. The change in the prevalence of cholelithiasis is associated with a proportionate rise in the incidence of cholangiocarcinoma. In an attempt to improve the quality of life of the rapidly increasing aging population, this article reviews up-to-date information on the pathophysiology of the gall bladder function and discusses the development of new therapies with potential good patient compliance and lower cost than the current treatments.

Prolonged melatonin administration in 6-month-old Sprague-Dawley rats: metabolic alterations

The aim of this work was to evaluate the effect of prolonged melatonin administration on chosen metabolic and hormonal variables in male and female Sprague-Dawley rats. Melatonin was administered in tap water (4 microg/ml) daily from the 6th month of age. Rats were fed a standard type of diet ad libitum and were kept in a light regimen L:D--12:12h. The experiment was terminated after 12 weeks of melatonin administration. Melatonin decreased body mass during the whole experiment in females and from the 42nd day of the experiment in males. Relative heart muscle weight in females and absolute/relative thymus weight in males were increased after melatonin administration. Melatonin decreased glycaemia, heart muscle glycogen concentration in females and liver glycogen concentration in both sexes. Serum insulin concentration in males was decreased; serum corticosterone concentration was increased in both males and females. Serum triacylglycerol and heart muscle cholesterol concentration in females were decreased, however in males serum and heart muscle cholesterol concentration was increased. Liver phospholipid concentration in females was decreased and heart muscle phospholipid concentration in males was increased. Melatonin increased malondialdehyde concentration in heart muscle in males and in liver in both sexes. Melatonin induced prominent sex-dependent changes in both carbohydrate and lipid metabolism.

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

Obesity and its associated metabolic pathologies are the most common and detrimental diseases, affecting over 50% of the adult population. Our knowledge about the protective effects of melatonin against high-fat diet (HFD)-induced obesity is still marginal. In this investigation, we hypothesized that melatonin can minimize the metabolic pathologies and morphological changes associated with obesity in animals receiving an HFD. To examine these effects, and to test our hypothesis, an animal model formed of male Boscat white rabbits was established. The animals were divided into three groups: (i) a control group fed regular diet; (ii) an obesity group fed an HFD for 12 weeks; and (iii) a treated group fed HFD for 12 weeks and then treated with melatonin for 4 weeks. The animals were killed and their serum and tissues were evaluated for: (i) lipid profile (cholesterol, triglycerides and low-density lipoprotein) and glucose; (ii) antioxidant enzyme (serum glutathione peroxidase, GSH-PX); and (iii) fatty changes (liver, kidney and blood vessels). Compared with the control group, intake of HFD (obesity group) was associated with: (i) a statistically significant increase in blood pressure, heart rate, sympathetic nerve activity, body weight, food consumption, serum lipids, blood glucose levels and atherogenic index; (ii) decreased level of GSH-PX and high-density lipoprotein (HDL); and (iii) fatty changes in the liver and kidney as well as atheromatous changes in the blood vessels. Compared with the obesity group, intake of melatonin (treated group) was associated with: (i) a statistically significant decrease in blood pressure, heart rate, sympathetic nerve activity, body weight, food consumption, serum lipids, blood glucose levels and atherogenic index; (ii) increased level of GSH-PX and HDL; and (iii) disappearance of fatty changes in the liver and kidney as well as atheromatous changes in the blood vessels. The administration of melatonin reduced the metabolic pathologies associated with the intake of HFD, suggesting a protective role. Although the underlying mechanisms are unclear, they may include its antioxidant and receptor-mediated effects. The clinical ramifications of these effects await further investigations.

Metabolic effects of melatonin on oxidative stress and diabetes mellitus

Melatonin, which is synthesized in the pineal gland and other tissues, has a variety of physiological, immunological, and biochemical functions. It is a direct scavenger of free radicals and has indirect antioxidant effects due to its stimulation of the expression and activity of antioxidative enzymes such as glutathione peroxidase, superoxide dismutase and catalase, and NO synthase, in mammalian cells. Melatonin also reduces serum lipid levels in mammalian species, and helps to prevent oxidative stress in diabetic subjects. Long-term melatonin administration to diabetic rats reduced their hyperlipidemia and hyperinsulinemia, and restored their altered ratios of polyunsaturated fatty acid in serum and tissues. It was recently reported that melatonin enhanced insulin-receptor kinase and IRS-1 phosphorylation, suggesting the potential existence of signaling pathway cross-talk between melatonin and insulin. Because TNF-alpha has been shown to impair insulin action by suppressing insulin receptor-tyrosine kinase activity and its IRS-1 tyrosine phosphorylation in peripheral tissues such as skeletal muscle cells, it was speculated that melatonin might counteract TNF-alpha-associated insulin resistance in type 2 diabetes. This review will focus on the physiological and metabolic effects of melatonin and highlight its potential use for the treatment of cholesterol/lipid and carbohydrate disorders.

Melatonin reduces cholesterol accumulation and prooxidant state induced by high cholesterol diet in the plasma, the liver and probably in the aorta of C57BL/6J mice

We examined the hypolipidemic and antioxidative effects of melatonin in plasma, liver and aorta of C57BL/6J mice fed on a high cholesterol (HC) diet. Mice were fed normal mice chow containing 1.5% cholesterol and 0.5% cholic acid for 4 months with or without melatonin (10 mg/L in drinking water) treatment. HC diet was observed to increase cholesterol, triglyceride and diene conjugate (DC) levels in plasma and liver. There was a tendency towards an increase in cholesterol level in the aorta following HC diet. In addition, aortic DC levels were higher than those of control group. No fatty streaks or plaques developed in the aorta of mice following HC diet, but in some sections, derangement of the endothelial layer was detected. Melatonin treatment was found to reduce plasma, liver cholesterol and DC levels as well as liver triglyceride levels in hypercholesterolemic mice. Aortic cholesterol and DC levels were also reduced in hypercholesterolemic mice when given melatonin, although not statistically significant. There were no differences in aortic histopathological findings of mice fed on a HC diet with and without melatonin treatment. In conclusion, our results indicate that melatonin reduces HC diet-induced cholesterol accumulation and prooxidant state in the plasma, liver and probably in the aorta.

Melatonin prevents apoptosis and enhances HSP27 mRNA expression induced by heat shock in HL-60 cells: possible involvement of the MT2 receptor

Previous studies have reported that melatonin protects cells and tissues against stressful stimuli. In the present study using HL-60 cells, we show that cells acquire increased resistance to apoptosis normally induced by heat shock when they are incubated with melatonin. This effect of melatonin is saturable at nanomolar concentrations and appears to be mediated by the MT2 subtype melatonin receptor. The high affinity melatonin receptor agonist, 2-iodomelatonin, reproduced the melatonin effect while it was fully blocked by the selective MT2 antagonist 4-phenyl-2-propionamidotetraline. The melatonin response to heat shock-induced apoptosis was pertussis toxin sensitive and, interestingly, the non-selective MT1/MT2 melatonin receptor ligand luzindole was found to display agonistic activity. Furthermore, we provide evidence that melatonin enhanced HSP27 mRNA expression as a result of heat shock - HSP27, is known to play an important role in the defense of cells against apoptosis induced by stressful agents. Together, these results demonstrate that melatonin, likely via receptor mechanisms, interferes with the apoptotic pathway activated by heat shock.

Melatonin: detoxification of oxygen and nitrogen-based toxic reactants

In the last decade, melatonin has been found to be highly protective against damage to macromolecules resulting from oxygen and nitrogen-based reactants. Considering this, numerous studies have examined the mechanisms whereby this indoleamine directly detoxifies these damaging agents. The evidence is compelling that melatonin scavenges several oxygen-derived reactive agents including the hydroxyl radical (OH), hydrogen peroxide (H2O2), singlet oxygen (1O2) and hypochlorous acid (HOCl). Additionally, melatonin reportedly reacts with nitric oxide (NO), the peroxynitrite anion (ONOO-) and/or peroxynitrous acid (ONOOH) to detoxify them. In some cases the products that are formed as a consequence of melatonin's scavenging actions have been identified. Whereas the ability of melatonin to neutralize these toxic agents likely accounts, in part, for the antioxidant activity of melatonin, it is not the only means by which melatonin serves to protect molecules from oxygen and nitrogen-based reactive metabolites.