Chronic melatonin consumption prevents obesity-related metabolic abnormalities and protects the heart against myocardial ischemia and reperfusion injury in a prediabetic model of diet-induced obesity

Baicalin and baicalein against myocardial ischemia-reperfusion injury: A review of the current documents

Myocardial ischemia-reperfusion injury (MIRI) is a significant challenge in the treatment of ischemic heart disease (IHD), arising as a complication from reperfusion therapies designed to restore blood flow after an ischemic event. Despite the availability of various therapeutic strategies, finding an effective treatment for MIRI remains difficult. Baicalin and its aglycone form (baicalein), natural compounds derived from the Chinese skullcap plant (Scutellaria baicalensis), have shown promise due to their antioxidant, anti-inflammatory, and cardioprotective properties. This review aims to explore the potential of baicalin and baicalein as treatments for MIRI, with a focus on their molecular and cellular level effects. These natural agents can decrease oxidative stress by promoting antioxidant enzymes and decreasing harmful oxidative substances that damage cardiac cells. They also exert anti-inflammatory effects by blocking specific pathways that trigger the release of inflammatory mediators. Additionally, they also improve heart cell survival, infarct region, and overall cardiac function by inhibiting key signaling pathways involved in cell death. Research in both animal and cell models suggests that these flavonoids, especially baicalin, can restore cardiac health following MIRI, improving cardiac performance, and reducing cardiac damage. These findings underscore the potential of baicalin and baicalein as therapeutic options for MIRI. However, further research and clinical trials are necessary to elucidate their mechanisms fully and to develop baicalin into a viable treatment.

A comparative study on the effect of melatonin and orlistat combination versus orlistat alone on high fat diet-induced hepatic changes in the adult male albino rats (a histological and morphometric study)

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the extremely usual reason of chronic liver disease, extending from simple hepatic steatosis (HS), nonalcoholic steatohepatitis (NASH) to advanced hepatic fibrosis and cirrhosis. Though orlistat is a Food and Drug Administration (FDA) approved drug for long-duration management of obesity, few cases of severe hepatic insult were declared. Melatonin is an efficient antioxidant; it also regulates metabolic processes that lead to fat accumulation and obesity.

AIM OF THE WORK

The current research aimed to compare the impact of orlistat, melatonin, and their combination on the structural changes of the hepatic tissue of adult male albino rats supplied with high fat diet (HFD).

MATERIAL AND METHODS

Thirty adult male albino rats divided into five groups. Liver specimens were divided into two parts. One-half was processed to obtain paraffin blocks, and the other half was processed to obtain semithin sections. Morphometric study and statistical analysis were done.

RESULTS

Hepatic tissue from the HFD group showed steatosis, ballooning, and inflammation and all these parameters were moderately improved - except for inflammation which worsened with therapy. Combined orlistat and melatonin-treated groups showed marked improvement of all parameters as well as marked improvement in the hepatic fibrosis.Orlistat/Melatonin combination therapy is both safe and effective in comparison to orlistat and melatonin monotherapy.

Impact of Melatonin Supplementation on Glycemic Parameters in Patients with Type 2 Diabetes: A Systematic Review and Meta-analysis

BACKGROUND

Several previous studies indicated that melatonin supplementation may positively affect glycemic control in patients with diabetes. However, research on the influence of melatonin supplementation on glycemic parameters remains inconclusive. Therefore, this study aimed to assess the impacts of melatonin supplementation on glycemic parameters in type 2 diabetes by conducting a meta-analysis.

METHODS

PubMed/Medline, Scopus, and Web of Science were comprehensively searched until July 2024 to find eligible randomized clinical trials (RCTs). The overall effect sizes were estimated by using the randomeffect model and presented as weighted mean differences (WMD) with a 95% confidence interval (CI). Furthermore, the heterogeneity among the included trials was assessed by performing the Cochran Q test and interpreted based on the I² statistic.

RESULTS

Of the 1361 papers, eight eligible RCTs were included in this meta-analysis. Our findings indicated that melatonin supplementation significantly decreased fasting blood glucose (WMD = -12.65 mg/dl; 95% CI: -20.38, -4.92; P = 0.001), insulin (WMD = -2.30 μU/ml; 95% CI: -3.20, -1.40; P < 0.001), hemoglobin A1c (WMD = -0.79 %; 95% CI: -1.28, -0.29; P = 0.002), and HOMA-IR (WMD, -0.83; 95% CI: -1.59 to - 0.07; P = 0.03).

CONCLUSION

According to the results of the current meta-analysis, persons with type 2 diabetes who supplement with melatonin had improved glycemic control. It looks that supplementing with melatonin at a dose exceeding 6 mg daily for over a period of 12 weeks may be more successful than other forms of intervention. Nevertheless, further research with larger sample sizes is necessary to draw definitive conclusions.

Microbial melatonin metabolism in the human intestine as a therapeutic target for dysbiosis and rhythm disorders

Melatonin (MT) (N-acetyl-5-methoxytryptamine) is an indoleamine recognized primarily for its crucial role in regulating sleep through circadian rhythm modulation in humans and animals. Beyond its association with the pineal gland, it is synthesized in various tissues, functioning as a hormone, tissue factor, autocoid, paracoid, and antioxidant, impacting multiple organ systems, including the gut-brain axis. However, the mechanisms of extra-pineal MT production and its role in microbiota-host interactions remain less understood. This review provides a comprehensive overview of MT, including its production, actions sites, metabolic pathways, and implications for human health. The gastrointestinal tract is highlighted as an additional source of MT, with an examination of its effects on the intestinal microbiota. This review explores whether the microbiota contributes to MT in the intestine, its relationship to food intake, and the implications for human health. Due to its impacts on the intestinal microbiota, MT may be a valuable therapeutic agent for various dysbiosis-associated conditions. Moreover, due to its influence on intestinal MT levels, the microbiota may be a possible therapeutic target for treating health disorders related to circadian rhythm dysregulation.

The Circadian Regulation of Nutrient Metabolism in Diet-Induced Obesity and Metabolic Disease

Obesity and other metabolic diseases are major public health issues that are particularly prevalent in industrialized societies where circadian rhythmicity is disturbed by shift work, jet lag, and/or social obligations. In mammals, daylight entrains the hypothalamic suprachiasmatic nucleus (SCN) to a ≈24 h cycle by initiating a transcription/translation feedback loop (TTFL) of molecular clock genes. The downstream impacts of the TTFL on clock-controlled genes allow the SCN to set the rhythm for the majority of physiological, metabolic, and behavioral processes. The TTFL, however, is ubiquitous and oscillates in tissues throughout the body. Tissues outside of the SCN are entrained to other signals, such as fed/fasting state, rather than light input. This system requires a considerable amount of biological flexibility as it functions to maintain homeostasis across varying conditions contained within a 24 h day. In the face of either circadian disruption (e.g., jet lag and shift work) or an obesity-induced decrease in metabolic flexibility, this finely tuned mechanism breaks down. Indeed, both human and rodent studies have found that obesity and metabolic disease develop when endogenous circadian pacing is at odds with the external cues. In the following review, we will delve into what is known on the circadian rhythmicity of nutrient metabolism and discuss obesity as a circadian disease.

Therapeutic potential of a single-dose melatonin in the attenuation of cardiac ischemia/reperfusion injury in prediabetic obese rats

Although acute melatonin treatment effectively reduces cardiac ischemia/reperfusion (I/R) injury in lean rats by modulating melatonin receptor 2 (MT2), there is no information regarding the temporal effects of melatonin administration during cardiac I/R injury in prediabetic obese rats. Prediabetic obese rats induced by chronic consumption of a high-fat diet (HFD) were used. The rats underwent a cardiac I/R surgical procedure (30-min of ischemia, followed by 120-min of reperfusion) and were randomly assigned to receive either vehicle or melatonin treatment. In the melatonin group, rats were divided into 3 different subgroups: (1) pretreatment, (2) treatment during ischemic period, (3) treatment at the reperfusion onset. In the pretreatment subgroup either a nonspecific MT blocker (Luzindole) or specific MT2 blocker (4-PPDOT) was also given to the rats prior to melatonin treatment. Pretreatment with melatonin (10 mg/kg) effectively reduced cardiac I/R injury by reducing infarct size, arrhythmia, and LV dysfunction. Reduction in impaired mitochondrial function, mitochondrial dynamic balance, oxidative stress, defective autophagy, and apoptosis were observed in rats pretreated with melatonin. Unfortunately, the cardioprotective benefits were not observed when 10-mg/kg of melatonin was acutely administered to the rats after cardiac ischemia. Thus, we increased the dose of melatonin to 20 mg/kg, and it was administered to the rats during ischemia or at the onset of reperfusion. The results showed that 20-mg/kg of melatonin effectively reduced cardiac I/R injury to a similar extent to the 10-mg/kg pretreatment regimen. The MT2 blocker inhibited the protective effects of melatonin. Acute melatonin treatment during cardiac I/R injury exerted protective effects in prediabetic obese rats. However, a higher dose of melatonin is required when given after the onset of cardiac ischemia. These effects of melatonin were mainly mediated through activation of MT2.

Akt: A Potential Drug Target for Metabolic Syndrome

The serine/threonine kinase Akt, also known as protein kinase B (PKB), is one of the key factors regulating glucose and lipid energy metabolism, and is the core focus of current research on diabetes and metabolic diseases. Akt is mostly expressed in key metabolism-related organs and it is activated in response to various stimuli, including cell stress, cell movement, and various hormones and drugs that affect cell metabolism. Genetic and pharmacological studies have shown that Akt is necessary to maintain the steady state of glucose and lipid metabolism and a variety of cellular responses. Existing evidence shows that metabolic syndrome is related to insulin resistance and lipid metabolism disorders. Based on a large number of studies on Akt-related pathways and reactions, we believe that Akt can be used as a potential drug target to effectively treat metabolic syndrome.

A New Paradigm in the Relationship between Melatonin and Breast Cancer: Gut Microbiota Identified as a Potential Regulatory Agent

In this review we summarize a possible connection between gut microbiota, melatonin production, and breast cancer. An imbalance in gut bacterial population composition (dysbiosis), or changes in the production of melatonin (circadian disruption) alters estrogen levels. On the one hand, this may be due to the bacterial composition of estrobolome, since bacteria with β-glucuronidase activity favour estrogens in a deconjugated state, which may ultimately lead to pathologies, including breast cancer. On the other hand, it has been shown that these changes in intestinal microbiota stimulate the kynurenine pathway, moving tryptophan away from the melatonergic pathway, thereby reducing circulating melatonin levels. Due to the fact that melatonin has antiestrogenic properties, it affects active and inactive estrogen levels. These changes increase the risk of developing breast cancer. Additionally, melatonin stimulates the differentiation of preadipocytes into adipocytes, which have low estrogen levels due to the fact that adipocytes do not express aromatase. Consequently, melatonin also reduces the risk of breast cancer. However, more studies are needed to determine the relationship between microbiota, melatonin, and breast cancer, in addition to clinical trials to confirm the sensitizing effects of melatonin to chemotherapy and radiotherapy, and its ability to ameliorate or prevent the side effects of these therapies.

Consumption of melatonin supplement improves cardiovascular disease risk factors and anthropometric indices in type 2 diabetes mellitus patients: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Diabetes mellitus is a common chronic disease. Dyslipidemia and hypertension are two complications that may develop in diabetic patients if hyperglycemia, insulin resistance, and weight gain are not controlled. This study investigated the effects of melatonin supplementation on some cardiovascular disease risk factors and anthropometric indices in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

In this double-blind, randomized, placebo-controlled trial, 50 T2DM patients were randomly allocated to intervention and control groups which received two tablets of either melatonin or placebo (250 mg) once a day for 8 weeks. Systolic blood pressure (SBP), mean arterial pressure (MAP), pulse pressure (PP), the atherogenic index of plasma (AIP), weight, body mass index (BMI), waist and hip circumference (WC, HC), a body shape index (ABSI), abdominal volume index (AVI), body adiposity index (BAI), lipid accumulation product (LAP), conicity index, and waist-to-height ratio (WHtR) were evaluated in all the patients pre- and post-intervention.

RESULTS

Melatonin supplementation for 8 weeks significantly decreased the mean levels of SBP, MAP, PP, weight, BMI, WC, HC, BAI, AVI, conicity index, and WHtR post-intervention (p <  0.05). Also, the median changes of SBP, MAP, PP, weight, BMI, WC, HC BAI, AVI, and conicity index were significantly lower in the intervention group compared with the control group (p <  0.05). A significant increase (p <  0.001) was observed in the mean levels of ABSI in the intervention group. The median changes of ABSI were significantly greater in the intervention group compared with the control group (p <  0.001).

CONCLUSIONS

Consumption of melatonin supplement may be effective in controlling arterial pressure including SBP, MAP, and PP and anthropometric indices (as predictors of obesity) in T2DM patients.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT20190303042905N1 . Registered on 17 May 2019.

Constitutive activation of ERK1/2 signaling protects against myocardial ischemia via inhibition of mitochondrial fragmentation in the aging heart

Background

Studies have shown that the ability of the myocardium to tolerate ischemia becomes significantly compromised with age. During ischemia, several endogenous protective signals are activated to protect the heart from injury, among which extracellular-signal regulated kinase (ERK) 1/2 signaling has been established as playing a pivotal role. However, in aging hearts, the activation of ERK1/2 is compromised. Mitogen-activated protein kinase/ERK kinase (MEK) is a major regulator of ERK1/2 signaling. In the present study, we investigated whether transduction of CaMEK, a constitutively activated MEK, using adeno-associated virus serotype 9 (AAV9) could protect the aging heart against ischemia.

Methods

Myocardial ischemia models were established in aging mice and senescent cardiomyocytes, and AAV9-mediated delivery of CaMEK was applied. Echocardiography, fluorescent staining, transmission electron microscopy, flow cytometry, and immunoblotting were used to explore the effects of CaMEK and their underlying mechanism.

Results

AAV9-CaMEK activated ERK1/2 signaling and exerted cardioprotective effects against ischemia in aging hearts. Specifically, CaMEK transduction decreased dynamin-related protein-1 (Drp1) expression and phosphorylation at serine 616, resulting in improved mitochondrial morphology and function in aging ischemic hearts. Furthermore, CaMEK transduction exerted similar protective effects in senescent cardiomyocytes under hypoxia. Meanwhile, with the inhibition of ERK1/2 signaling in senescent cardiomyocytes under hypoxia, the opposite effects were observed, including an increase in mitochondrial fragmentation and aggravation of mitochondrial dysfunction and cell apoptosis.

Conclusions

Our results suggested that AAV9-CaMEK alleviated ischemia-induced myocardium injury in the aging heart, at least in part, through inhibition of mitochondrial fragmentation. Therefore, AAV9-CaMEK is a potential intervention for prevention of ischemia-induced injury of the aging myocardium.

Melatonin reverses the loss of the anticontractile effect of perivascular adipose tissue in obese rats

Perivascular adipose tissue (PVAT) undergoes functional changes in obesity. Increased oxidative stress is a central mechanism whereby obesity induces loss of the anticontractile effect of PVAT. Melatonin is an antioxidant that displays vasoprotective action in cardiovascular disease. Here, we sought to investigate whether melatonin would restore the anticontractile effect of periaortic PVAT in obesity. Male Wistar Hannover rats were treated for 10 weeks with a high-calorie diet. Melatonin (5 mg/kg/d, p.o., gavage) was administered for 2 weeks. Functional findings showed that obesity-induced loss of the anticontractile effect of PVAT and treatment with melatonin reversed this response. Tiron [a scavenger of superoxide anion (O₂ ^- )] restored the anticontractile effect of PVAT in aortas from obese rats, suggesting a role for reactive oxygen species (ROS) in such response. Decreased superoxide dismutase (SOD) activity and augmented levels of ROS were detected in periaortic PVAT from obese rats. These responses were accompanied by decreased levels of nitric oxide (NO) in PVAT. Treatment with melatonin restored SOD activity, decreased ROS levels, and increased NO bioavailability in PVAT from obese rats. Here, we first reported the beneficial effects of melatonin in periaortic PVAT in obesity. Melatonin reversed the adverse effects of obesity in PVAT that included overproduction of ROS, reduced SOD activity, and decreased bioavailability of NO. Therefore, PVAT may constitute an important target for the treatment of obesity-induced vascular dysfunction and melatonin emerges as a potential tool in the management of the vascular complications induced by obesity.

A Comparison of Hematological, Immunological, and Stress Responses to Capture and Transport in Wild White Rhinoceros Bulls (Ceratotherium simum simum) Supplemented With Azaperone or Midazolam

Capture and transport are essential procedures for the management and conservation of southern white rhinoceroses (Ceratotherium simum simum), but are associated with stress-induced morbidity and mortality. To improve conservation efforts, it is crucial to understand the pathophysiology of rhinoceros stress responses and investigate drug combinations that could reduce these responses. In this study we measured rhinoceros stress responses to capture and transport by quantifying hematological and immunological changes together with adrenal hormone concentrations. We investigated whether the potent anxiolytic drug midazolam was able to mitigate these responses compared to azaperone, which is more commonly used during rhinoceros transport. Twenty three wild white rhinoceros bulls were transported for 6 h (280 km) within the Kruger National Park for reasons unrelated to this study. Rhinoceroses were immobilized with either etorphine-azaperone (group A, n = 11) or etorphine-midazolam (group M, n = 12) intramuscularly by darting from a helicopter. Azaperone (group A) or midazolam (group M) were re-administered intramuscularly every 2 h during transport. Serial blood samples were collected at capture (TC), the start of transport (T0) and after 6 h of transport (T6). Changes in hematological and immunological variables over time and between groups were compared using general mixed models. Increases in plasma epinephrine and serum cortisol concentrations indicated that rhinoceroses mounted a stress response to capture and transport. Packed cell volume decreased from TC to T6 indicating that stress hemoconcentration occurred at TC. Neutrophils progressively increased and lymphocytes and eosinophils progressively decreased from T0 to T6, resulting in an increase in neutrophil to lymphocyte ratio; a characteristic leukocyte response to circulating glucocorticoids. A reduction in serum iron concentrations may suggest the mounting of an acute phase response. Rhinoceroses experienced a decrease in unsaturated fatty acids and an increase in lipid peroxidation products at capture and toward the end of transport indicating oxidative stress. Midazolam, at the dose used in this study, was not able to mitigate adrenal responses to stress and appeared to directly influence leukocyte responses.

Melatonin as a protective agent in cardiac ischemia-reperfusion injury: Vision/Illusion?

Melatonin, an emphatic endogenous molecule exerts protective effects either via activation of G-protein coupled receptors (Melatonin receptors, MTR 1-3), tumor necrosis factor receptor (TNFR), toll like receptors (TLRS), nuclear receptors (NRS) or by directly scavenging the free radicals. MTRs are extensively expressed in the heart as well as in the coronary vasculature. Accumulating evidences have indicated the existence of a strong correlation between reduction in the circulating level of melatonin and precipitation of heart attack. Apparently, melatonin exhibits cardioprotective effects via modulating inextricably interlinked pathways including modulation of mitochondrial metabolism, mitochondrial permeability transition pore formation, nitric oxide release, autophagy, generation of inflammatory cytokines, regulation of calcium transporters, reactive oxygen species, glycosaminoglycans, collagen accumulation, and regulation of apoptosis. Convincingly, this review shall describe the various signaling pathways involved in salvaging the heart against ischemia-reperfusion injury.

Melatonin's Impact on Antioxidative and Anti-Inflammatory Reprogramming in Homeostasis and Disease

There is a growing consensus that the antioxidant and anti-inflammatory properties of melatonin are of great importance in preserving the body functions and homeostasis, with great impact in the peripartum period and adult life. Melatonin promotes adaptation through allostasis and stands out as an endogenous, dietary, and therapeutic molecule with important health benefits. The anti-inflammatory and antioxidant effects of melatonin are intertwined and are exerted throughout pregnancy and later during development and aging. Melatonin supplementation during pregnancy can reduce ischemia-induced oxidative damage in the fetal brain, increase offspring survival in inflammatory states, and reduce blood pressure in the adult offspring. In adulthood, disturbances in melatonin production negatively impact the progression of cardiovascular risk factors and promote cardiovascular and neurodegenerative diseases. The most studied cardiovascular effects of melatonin are linked to hypertension and myocardial ischemia/reperfusion injury, while the most promising ones are linked to regaining control of metabolic syndrome components. In addition, there might be an emerging role for melatonin as an adjuvant in treating coronavirus disease 2019 (COVID 19). The present review summarizes and comments on important data regarding the roles exerted by melatonin in homeostasis and oxidative stress and inflammation related pathologies.

Long-chain free fatty acids inhibit ischaemic preconditioning of the isolated rat heart

We recently reported that non-preconditioned hearts from diet-induced obese rats showed, compared to controls, a significant reduction in infarct size after ischaemia/reperfusion, whilst ischaemic preconditioning was without effect. In view of the high circulating FFA concentration in diet rats, the aims of the present study were to: (i) compare the effect of palmitate on the preconditioning potential of hearts from age-matched controls and diet rats (ii) elucidate the effects of substrate manipulation on ischaemic preconditioning. Substrate manipulation was done with dichloroacetate (DCA), which enhances glucose oxidation and decreases fatty acid oxidation. Isolated hearts from diet rats, age-matched controls or young rats, were perfused in the working mode using the following substrates: glucose (10 mM); palmitate (1.2 mM)/3% albumin) + glucose (10 mM) (HiFA + G); palmitate (1.2 mM/3% albumin) (HiFA); palmitate (0.4 mM/3% albumin) + glucose(10 mM) (LoFA + G); palmitate (0.4 mM/3% albumin) (LoFA). Hearts were preconditioned with 3 × 5 min ischaemia/reperfusion, followed by 35 min coronary ligation and 60 min reperfusion for infarct size determination (tetrazolium method) or 20 min global ischaemia/10 or 30 min reperfusion for Western blotting (ERKp44/42, PKB/Akt). Preconditioning of glucose-perfused hearts from age-matched control (but not diet) rats reduced infarct size, activated ERKp44/42 and PKB/Akt and improved functional recovery during reperfusion (ii) perfusion with HiFA + G abolished preconditioning and activation of ERKp44/42 (iii) DCA pretreatment largely reversed the harmful effects of HiFA. Hearts from non-preconditioned diet rats exhibited smaller infarcts, but could not be preconditioned, regardless of the substrate. Similar results were obtained upon substrate manipulation of hearts from young rats. Abolishment of preconditioning in diet rats may be due to altered myocardial metabolic patterns resulting from changes in circulating FA. The harmful effects of HiFA were attenuated by stimulation of glycolysis and inhibition of FA oxidation.

Melatonin against Myocardial Ischemia-Reperfusion Injury: A Meta-analysis and Mechanism Insight from Animal Studies

Aims

Myocardial reperfusion damage after severe ischemia was an important issue during a clinical practice. However, the exacted pathogenesis involved remained unclear and also lacks effective interventions. Melatonin was identified to exert protective effects for alleviating the myocardial I/R injury. This meta-analysis was determined to evaluate the efficacy of melatonin treatment against reperfusion insult and further summarize potential molecular and cellular mechanisms.

Methods and Results

15 eligible studies with 211 animals (108 received melatonin and 103 received vehicle) were included after searching the databases of PubMed, MEDLINE, Embase, and Cochrane. Pretreatment with melatonin was associated with a significant lower infarct size in comparison with vehicle in myocardial I/R damage (WMD: -20.45, 95% CI: -25.43 to -15.47, p < 0.001; I² = 91.4%, p < 0.001). Evidence from subgroup analyses and sensitivity analysis indicated the robust and consistent cardioprotective effect of melatonin, while the metaregression also did not unmask any significant interactions between the pooled estimates and covariates (i.e., sample size, state, species, study type, route of administration, and duration of reperfusion, along with timing regimen of pretreatment). Accordingly, melatonin evidently increased EF (WMD: 17.19, 95% CI: 11.08 to 23.29, p < 0.001; I² = 77.0%, p < 0.001) and FS (WMD: 14.18, 95% CI: 11.22 to 17.15, p < 0.001; I² = 3.5%, p = 0.387) in the setting of reperfusion damage.

Conclusions

Melatonin preadministration conferred a profound cardioprotection against myocardial I/R injury in preclinical studies.

Infusion of Melatonin Into the Paraventricular Nucleus Ameliorates Myocardial Ischemia-Reperfusion Injury by Regulating Oxidative Stress and Inflammatory Cytokines

Melatonin, the receptors for which are abundant in the hypothalamic paraventricular nucleus (PVN), can protect the heart from myocardial ischemia–reperfusion (MI/R) injury. The aim of this study was to determine whether the infusion of melatonin into the PVN protects the heart from MI/R injury by suppressing oxidative stress or regulating the balance between proinflammatory cytokines and anti-inflammatory cytokines in MI/R rats. Male Sprague–Dawley rats were treated with a bilateral PVN infusion of melatonin. MI/R operation was performed 1 week after infusion. At the end of the third week after the infusion, all the rats were euthanized. This was followed by immunohistochemistry and immunofluorescence studies of the rats. MI/R rats showed larger infarct size, increased left ventricular (LV) end-diastolic volume, and decreased LV ejection fraction and LV fractional shortening. Moreover, MI/R rats had a higher level of norepinephrine in the plasma, heart, and PVN; higher PVN levels of reactive oxygen species, NOX2, NOX4, IL-1β, and NF-κB activity; and lower PVN levels of copper/zinc superoxide dismutase (Cu/Zn-SOD) and IL-10 compared with the sham group. Melatonin infusion in PVN reduced LV end-diastolic volume, norepinephrine, reactive oxygen species, NOX2, NOX4, IL-1β, and NF-κB activity, and increased LV ejection fraction, LV fractional shortening, Cu/Zn-SOD, and IL-10. Overall, these results suggest that the infusion of melatonin ameliorates sympathetic nerve activity and MI/R injury by attenuating oxidative stress and inflammatory cytokines in the PVN of MI/R rats.

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 Improves Fatty Liver Syndrome by Inhibiting the Lipogenesis Pathway in Hamsters with High-Fat Diet-Induced Hyperlipidemia

The aim of this study was to investigate the effect of melatonin on hepatic lipid metabolism in hamsters with high-fat diet (HFD)-induced dyslipidemia. Male Syrian hamsters were kept on either a chow control (C) or HFD for four weeks. After four weeks, animals fed the HFD were further randomly assigned to four groups: high-fat only (P), melatonin low-dosage (L), medium-dosage (M), and high-dosage (H) groups. The L, M, and H groups, respectively, received 10, 20, and 50 mg/kg/day of a melatonin solution, while the P and C groups received the ethanol vehicle. After eight weeks of the intervention, results showed that a low dose of melatonin significantly reduced HFD-induced hepatic cholesterol and triglycerides; decreased plasma cholesterol, triglycerides, and low-density lipoprotein cholesterol; and increased plasma high-density lipoprotein cholesterol (p < 0.05). In addition, melatonin markedly decreased activities of the hepatic lipogenic enzymes, acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) (p < 0.05), and elevated the relative hepatic carnitine palmitoyltransferase-1α expression in hamsters with HFD-induced hyperlipidemia. Consequently, melatonin reduced activities of the hepatic lipogenic enzymes, ACC and FAS. In summary, chronic melatonin administration improved HFD-induced dyslipidemia and hepatic lipid accumulation in Syrian hamsters with HFD-induced dyslipidemia, which might have occurred through inhibiting the lipogenesis pathway.

The impact of sugar-sweetened beverage intake on rat cardiac function

Aims

Although there is evidence linking sugar-sweetened beverage (SSB) intake with the development of cardio-metabolic diseases, the underlying mechanisms remain unclear. The current study therefore evaluated the effects of SSB consumption by establishing a unique in-house in vivo experimental model.

Main methods

Male Wistar rats were divided into two groups: a) one consuming a popular local SSB (SSB- Jive), and b) a control group (Control-water) for a period of three and six months (n = 6 per group), respectively. Rats were gavaged on a daily basis with an experimental dosage amounting to half a glass per day (in human terms) (SSB vs. water). Cardiac function was assessed at baseline (echocardiography) and following ex vivo ischemia-reperfusion of the isolated perfused working rat heart. Oral glucose tolerance tests and mitochondrial respiratory analyses were also performed. In addition, the role of non-oxidative glucose pathways (NOGPs), i.e. the polyol pathway, hexosamine biosynthetic pathway (HBP) and PKC were assessed.

Key findings

These data show that SSB intake: a) resulted in increased weight gain, but did not elicit major effects in terms of insulin resistance and cardiac function after three and six months, respectively; b) triggered myocardial NOGP activation after three months with a reversion after six months; and c) resulted in some impairment in mitochondrial respiratory capacity in response to fatty acid substrate supply after six months.

Significance

SSB intake did not result in cardiac dysfunction or insulin resistance. However, early changes at the molecular level may increase risk in the longer term.

The effects of melatonin supplementation on blood pressure in patients with metabolic disorders: a systematic review and meta-analysis of randomized controlled trials

The current systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to evaluate the potential effect of melatonin supplementation on blood pressure in patients with metabolic disorders. The following databases were searched until June 2018: PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials. Two reviewers independently assessed the eligibility of retrieved studies, extracted data from included trials, and evaluated the risk of bias of included studies. Statistical heterogeneity was tested using Cochran's Q test and I-square (I²) statistic. Data were pooled using random-effect models and standardized mean difference (SMD) was considered as the effect size. Eight RCTs, out of 743 potential citations, were eligible to be included in the current meta-analysis. The pooled findings indicated a significant reduction in systolic (SBP) (SMD = -0.87; 95% CI, -1.36, -0.38; P = 0.001; I²: 84.3) and diastolic blood pressure (DBP) (SMD = -0.85; 95% CI, -1.20, -0.51; P = 0.001; I²: 68.7) following melatonin supplementation in individuals with metabolic disorders. In summary, the current meta-analysis demonstrated that melatonin supplementation significantly decreased SBP and DBP in patients with metabolic disorders. Additional prospective studies are recommended using higher supplementation doses and longer intervention periods to confirm our findings.

Treatment with a fixed dose combination antiretroviral therapy drug containing tenofovir, emtricitabine and efavirenz is associated with cardioprotection in high calorie diet-induced obese rats

HIV-infection, certain antiretroviral drug classes, especially protease inhibitors (PI), and obesity are associated with increased ischaemic heart disease (IHD) risk. However, the effect of PI-free fixed dose combination (FDC) antiretroviral therapy (ART) on hearts exposed to ischaemia-reperfusion injury (I/R) is unknown, particularly in obesity. This is becoming relevant as World Health Organisation guidelines recommend a FDC ART containing (non-) nucleoside reverse transcriptase inhibitors (tenofovir (TDF), emtricitabine (FTC) and efavirenz (EFV)) as first-line HIV treatment. Additionally, obesity rates are rising in HIV-infected populations, not only in ART-experienced individuals, but also at the time of ART initiation, which may further increase the risk of IHD. Therefore, we investigated the effects of PI-free FDC ART in myocardial I/R-exposed hearts from obese rats. Obesity was induced in male wistar rats via a 16-week high calorie diet. At week 10, treatment with a FDC ART drug containing TDF/FTC/EFV was initiated. Biometric and metabolic parameters, as well as myocardial functional recovery and infract size (IS), and myocardial signalling proteins following I/R were assessed after 16 weeks. Obese rats presented with increased body and intraperitoneal fat mass, elevated triglyceride and TBARS levels, whilst the hearts responded to I/R with impaired functional performance and increased IS. The FDC ART treatment did not alter biometric and metabolic parameters in obese rats. In a novel finding, ART protected obese hearts against I/R as shown by improved functional performance and smaller IS vs. untreated obese hearts. Cardioprotection was underscored by increased myocardial phosphorylated endothelial nitric oxide synthase (eNOS) and reduced AMP-kinase levels. In conclusion, these results demonstrate for the first time, that 6-weeks treatment of obese rats with a FDC ART drug specifically containing TDF/FTC/EFV conferred cardioprotection against I/R. The FDC ART-induced cardioprotection was seemingly unrelated to metabolic changes, but rather due to direct cardiac mechanisms including the up-regulation of myocardial eNOS.

Melatonin in Heart Failure: A Promising Therapeutic Strategy?

Heart failure is a multifactorial clinical syndrome characterized by the inability of the heart to pump sufficient blood to the body. Despite recent advances in medical management, poor outcomes in patients with heart failure remain very high. This highlights a need for novel paradigms for effective, preventive and curative strategies. Substantial evidence supports the importance of endogenous melatonin in cardiovascular health and the benefits of melatonin supplementation in various cardiac pathologies and cardiometabolic disorders. Melatonin plays a crucial role in major pathological processes associated with heart failure including ischemic injury, oxidative stress, apoptosis, and cardiac remodeling. In this review, available evidence for the role of melatonin in heart failure is discussed. Current challenges and possible limitations of using melatonin in heart failure are also addressed. While few clinical studies have investigated the role of melatonin in the context of heart failure, current findings from experimental studies support the potential use of melatonin as preventive and adjunctive curative therapy in heart failure.

Cardiovascular Benefits of Dietary Melatonin: A Myth or a Reality?

The role of the diet as well as the impact of the dietary habits on human health and disease is well established. Apart from its sleep regulatory effect, the indoleamine melatonin is a well-established antioxidant molecule with multiple health benefits. Convincing evidence supports the presence of melatonin in plants and foods with the intake of such foods affecting circulating melatonin levels in humans. While numerous actions of both endogenous melatonin and melatonin supplementation are well described, little is known about the influence of the dietary melatonin intake on human health. In the present review, evidence for the cardiovascular health benefits of melatonin supplementation and dietary melatonin is discussed. Current knowledge on the biological significance as well as the underlying physiological mechanism of action of the dietary melatonin is also summarized. Whether dietary melatonin constitutes an alternative preventive treatment for cardiovascular disease is addressed.

Melatonin: A Molecule for Reducing Breast Cancer Risk

The objective of this article is to review the basis supporting the usefulness of melatonin as an adjuvant therapy for breast cancer (BC) prevention in several groups of individuals at high risk for this disease. Melatonin, as a result of its antiestrogenic and antioxidant properties, as well as its ability to improve the efficacy and reduce the side effects of conventional antiestrogens, could safely be associated with the antiestrogenic drugs presently in use. In individuals at risk of BC due to night shift work, the light-induced inhibition of melatonin secretion, with the consequent loss of its antiestrogenic effects, would be countered by administering this neurohormone. BC risk from exposure to metalloestrogens, such as cadmium, could be treated with melatonin supplements to individuals at risk of BC due to exposure to this xenoestrogen. The BC risk related to obesity may be reduced by melatonin which decrease body fat mass, inhibits the enhanced aromatase expression in obese women, increases adiponectin secretion, counteracts the oncogenic effects of elevated concentrations of leptin; and decreases blood glucose levels and insulin resistance. Despite compelling experimental evidence of melatonin's oncostatic actions being susceptible to lowering BC risk, there is still a paucity of clinical trials focused on this subject.

Central Circadian Clock Regulates Energy Metabolism

Our body not only responds to environmental changes but also anticipates them. The light and dark cycle with the period of about 24 h is a recurring environmental change that determines the diurnal variation in food availability and safety from predators in nature. As a result, the circadian clock is evolved in most animals to align locomotor behaviors and energy metabolism with the light cue. The central circadian clock in mammals is located at the suprachiasmatic nucleus (SCN) of the hypothalamus in the brain. We here review the molecular and anatomic architecture of the central circadian clock in mammals, describe the experimental and observational evidence that suggests a critical role of the central circadian clock in shaping systemic energy metabolism, and discuss the involvement of endocrine factors, neuropeptides, and the autonomic nervous system in the metabolic functions of the central circadian clock.

Melatonin, mitochondria, and the metabolic syndrome

A number of risk factors for cardiovascular disease including hyperinsulinemia, glucose intolerance, dyslipidemia, obesity, and elevated blood pressure are collectively known as metabolic syndrome (MS). Since mitochondrial activity is modulated by the availability of energy in cells, the disruption of key regulators of metabolism in MS not only affects the activity of mitochondria but also their dynamics and turnover. Therefore, a link of MS with mitochondrial dysfunction has been suspected since long. As a chronobiotic/cytoprotective agent, melatonin has a special place in prevention and treatment of MS. Melatonin levels are reduced in diseases associated with insulin resistance like MS. Melatonin improves sleep efficiency and has antioxidant and anti-inflammatory properties, partly for its role as a metabolic regulator and mitochondrial protector. We discuss in the present review the several cytoprotective melatonin actions that attenuate inflammatory responses in MS. The clinical data that support the potential therapeutical value of melatonin in human MS are reviewed.

Monotherapy of experimental metabolic syndrome: II. Study of cardiovascular effects

Metabolic syndrome belongs to the most important risk factors of cardiovascular diseases. The aim of this study was to investigate changes in cardiovascular system induced by high cholesterol and high fat diet (HCHF) in HTG rats and their influence by a pyridoindole antioxidant - SMe1EC2 (S). The effects of S were compared with those of atorvastatin (A). Male HTG rats were fed HCHF (1% cholesterol + 7.5% lard) for 4 weeks. S and A were administered p.o., 50 mg/kg b.w. Following experimental groups were used: Wistar rats (W), hypertriglyceridemic rats (HTG), HTG rats fed HCHF (CHOL), HTG+S (S-HTG), CHOL+S (S-CHOL), and CHOL+A (A-CHOL). Values of blood pressure (BP) and selected ECG parameters were monitored in conscious animals, functions of the isolated heart and aorta were analyzed ex vivo. At the end of the experiment, systolic (sBP) and diastolic (dBP) blood pressure was increased in HTG and CHOL. S and A decreased BP in all treated groups. Accordingly with BP changes, the aortic endothelial function of CHOL was damaged. Both S and A administration ameliorated the endothelium-dependent relaxation to values of W. PQ and QTc intervals were prolonged in CHOL, while the treatment with S or A improved ECG findings. Prodysrhythmogenic threshold was decreased significantly in CHOL and both treatments returned it to the control values. In conclusion, HCHF increased BP, impaired endothelial relaxation of the aorta and potentiated susceptibility of myocardium to dysrhythmias. The effect of S on the changes induced by HCHF diet was more pronounced than that of A.

Effects of Melatonin on Glucose Homeostasis, Antioxidant Ability, and Adipokine Secretion in ICR Mice with NA/STZ-Induced Hyperglycemia

Diabetes is often associated with decreased melatonin level. The aim was to investigate the effects of different dosage of melatonin on glucose hemostasis, antioxidant ability and adipokines secretion in diabetic institute for cancer research (ICR) mice. Forty animals were randomly divided into five groups including control (C), diabetic (D), low-dosage (L), medium-dosage (M), and high-dosage (H) groups. Groups L, M, and H, respectively, received oral melatonin at 10, 20, and 50 mg/kg of BW (body weight) daily after inducing hyperglycemia by nicotinamide (NA)/ streptozotocin (STZ). After the six-week intervention, results showed that melatonin administration increased insulin level and performed lower area under the curve (AUC) in H group (p < 0.05). Melatonin could lower hepatic Malondialdehyde (MDA) level in all melatonin-treated groups and increase superoxide dismutase activity in H group (p < 0.05). Melatonin-treated groups revealed significant higher adiponectin in L group, and lower leptin/adiponectin ratio and leptin in M and H groups (p < 0.05). Melatonin could lower cholesterol and triglyceride in liver and decrease plasma cholesterol and low-density lipoprotein-cholesterol (LDL-C) in L group, and increase plasma high-density lipoprotein-cholesterol (HDL-C) in H group (p < 0.05). Above all, melatonin could decrease oxidative stress, increase the adiponectin level and improve dyslipidemia, especially in H group. These data support melatonin possibly being a helpful aid for treating hyperglycemia-related symptoms.

Role of melatonin in glucose uptake by cardiomyocytes from insulin-resistant Wistar rats

Aim

Melatonin supplementation reduces insulin resistance and protects the heart in obese rats. However, its role in myocardial glucose uptake remains unknown. This study investigated the effect of short-term melatonin treatment on glucose uptake by cardiomyocytes isolated from obese and insulin-resistant rats.

Methods

Cardiomyocytes were isolated from obese rats fed a high-calorie diet for 16 to 23 weeks, their age-matched controls, as well as young control rats aged four to eight weeks. After incubation with melatonin with or without insulin, glucose uptake was initiated by the addition of 2-deoxy-D-[3H] glucose and measured after 30 minutes. Additional control and obese rats received melatonin in the drinking water (4 mg/kg/day) for the last six weeks of feeding (20 weeks) and glucose uptake was determined in isolated cardiomyocytes after incubation with insulin. Intraperitoneal glucose tolerance and biometric parameters were also measured.

Results

Obese rats (fed for more than 20 weeks) developed glucose intolerance. Cardiomyocytes isolated from these obese rats had a reduced response to insulin-stimulated glucose uptake (ISGU) (p < 0.05). Melatonin administration in vitro had no effect on glucose uptake per se. However, it increased ISGU by cardiomyocytes from the young rats (p < 0.05), while having no effect on ISGU by cardiomyocytes from the older control and obese groups. Melatonin in vivo had no significant effect on glucose tolerance, but it increased basal (p < 0.05) and ISGU by cardiomyocytes from the obese rats (50.1 ± 1.7 vs 32.1 ± 5.1 pmol/mg protein/30 min, p < 0.01).

Conclusion

These data suggest that short-term melatonin treatment in vivo but not in vitro improved glucose uptake and insulin responsiveness of cardiomyocytes in obesity and insulin-resistance states.

New targets for rapid antidepressant action

Current therapeutic options for major depressive disorder (MDD) and bipolar disorder (BD) are associated with a lag of onset that can prolong distress and impairment for patients, and their antidepressant efficacy is often limited. All currently approved antidepressant medications for MDD act primarily through monoaminergic mechanisms. Glutamate is the major excitatory neurotransmitter in the central nervous system, and glutamate and its cognate receptors are implicated in the pathophysiology of MDD, and in the development of novel therapeutics for this disorder. The rapid and robust antidepressant effects of the N-methyl-d-aspartate (NMDA) antagonist ketamine were first observed in 2000. Since then, other NMDA receptor antagonists have been studied in MDD. Most have demonstrated relatively modest antidepressant effects compared to ketamine, but some have shown more favorable characteristics. This article reviews the clinical evidence supporting the use of novel glutamate receptor modulators with direct affinity for cognate receptors: (1) non-competitive NMDA receptor antagonists (ketamine, memantine, dextromethorphan, AZD6765); (2) subunit (GluN2B)-specific NMDA receptor antagonists (CP-101,606/traxoprodil, MK-0657); (3) NMDA receptor glycine-site partial agonists (GLYX-13); and (4) metabotropic glutamate receptor (mGluR) modulators (AZD2066, RO4917523/basimglurant). We also briefly discuss several other theoretical glutamate receptor targets with preclinical antidepressant-like efficacy that have yet to be studied clinically; these include α-amino-3-hydroxyl-5-methyl-4-isoxazoleproprionic acid (AMPA) agonists and mGluR2/3 negative allosteric modulators. The review also discusses other promising, non-glutamatergic targets for potential rapid antidepressant effects, including the cholinergic system (scopolamine), the opioid system (ALKS-5461), corticotropin releasing factor (CRF) receptor antagonists (CP-316,311), and others.

Melatonin protects against uric acid-induced mitochondrial dysfunction, oxidative stress, and triglyceride accumulation in C2C12myotubes

Excess uric acid has been shown to induce oxidative stress, triglyceride accumulation, and mitochondrial dysfunction in the liver and is an independent predictor of type-2 diabetes. Skeletal muscle plays a dominant role in type 2 diabetes and presents a large surface area to plasma uric acid. However, the effects of uric acid on skeletal muscle are underinvestigated. Our aim was therefore to characterize the effects of excessive uric acid on oxidative stress, triglyceride content, and mitochondrial function in skeletal muscle C2C12myotubes and assess how these are modulated by the antioxidant molecule melatonin. Differentiated C2C12myotubes were exposed to 750 µM uric acid or uric acid + 10 nM melatonin for 72 h. Compared with control, uric acid increased triglyceride content by ~237%, oxidative stress by 32%, and antioxidant capacity by 135%. Uric acid also reduced endogenous ROUTINE respiration, complex II-linked oxidative phosphorylation, and electron transfer system capacities. Melatonin counteracted the effects of uric acid without further altering antioxidant capacity. Our data demonstrate that excess uric acid has adverse effects on skeletal muscle similar to those previously reported in hepatocytes and suggest that melatonin at a low physiological concentration of 10 nM may be a possible therapy against some adverse effects of excess uric acid.

NEW & NOTEWORTHY Few studies have investigated the effects of uric acid on skeletal muscle. This study shows that hyperuricemia induces mitochondrial dysfunction and triglyceride accumulation in skeletal muscle. The findings may explain why hyperuricemia is an independent predictor of diabetes.

Myocardial susceptibility to ischaemia/reperfusion in obesity: a re-evaluation of the effects of age

Background

Reports on the effect of age and obesity on myocardial ischaemia/reperfusion (I/R) injury and ischaemic preconditioning are contradictory. The aim of this study was to re-evaluate the effects of age and diet-induced obesity (DIO) on myocardial I/R injury and preconditioning potential.

Methods

Four groups of Wistar male rats were used: age-matched controls (AMC) receiving standard rat chow for (i) 16 weeks and (ii) 16 months respectively; DIO rats receiving a sucrose-supplemented diet for (iii) 16 weeks and (iv) 16 months respectively. The ages of groups (i) and (iii) were 22 weeks (“young”) and groups (ii) and (iv) 17 months (“middle-aged”) at time of experimentation. Isolated perfused working hearts were subjected to 35 min regional ischaemia/1 h reperfusion. Endpoints were infarct size (tetrazolium staining) and functional recovery. Hearts were preconditioned by 3 × 5 min ischaemia/5 min reperfusion. Results were processed using GraphPad Prism statistical software.

Results

Age did not affect baseline heart function before induction of ischaemia and I/R damage as indicated by infarct size and similar values were obtained in hearts from both age groups. Age also had no effect on functional recovery of hearts during reperfusion after regional ischaemia in AMC rats, but cardiac output during reperfusion was better in hearts from middle-aged than young DIO rats.

The diet reduced infarct size in hearts from young rats (% of area at risk: AMC: 32.4 ± 3.6; DIO: 20.7 ± 2.9, p < 0.05), with no differences in hearts from middle-aged rats (AMC: 24.6 ± 4.6; DIO: 28.3 ± 13.5, p = NS). Compared to their respective AMC, diet-induced obesity had no significant effect on functional recovery of hearts from both age groups after exposure to regional ischaemia.

When exposed to the more severe stress of global ischaemia, the functional recovery potential of middle-aged DIO rats appeared to be impeded compared to hearts of young DIO rats, while age had no effect on the functional recovery of AMC hearts.

Preconditioning reduced infarct size in hearts from young control rats and both middle-aged groups, but not from young DIO rats. Age had a significant effect on functional recovery in preconditioning: it was improved in hearts from young control and DIO rats, but depressed in both middle-aged groups.

Conclusions

The data showed that middle-age and obesity had no effect on baseline myocardial function and did not increase susceptibility to I/R damage upon exposure to regional ischaemia. On the contrary, obesity reduced I/R damage in young rats. Preconditioned aging hearts showed a decreased infarct size, but a reduction in functional recovery.

Mechanisms of Melatonin in Alleviating Alzheimer's Disease

Alzheimer's disease (AD) is a chronic, progressive and prevalent neurodegenerative disease characterized by the loss of higher cognitive functions and an associated loss of memory. The thus far "incurable" stigma for AD prevails because of variations in the success rates of different treatment protocols in animal and human studies. Among the classical hypotheses explaining AD pathogenesis, the amyloid hypothesis is currently being targeted for drug development. The underlying concept is to prevent the formation of these neurotoxic peptides which play a central role in AD pathology and trigger a multispectral cascade of neurodegenerative processes post-aggregation. This could possibly be achieved by pharmacological inhibition of β- or γ-secretase or stimulating the nonamyloidogenic α-secretase. Melatonin the pineal hormone is a multifunctioning indoleamine. Production of this amphiphilic molecule diminishes with advancing age and this decrease runs parallel with the progression of AD which itself explains the potential benefits of melatonin in line of development and devastating consequences of the disease progression. Our recent studies have revealed a novel mechanism by which melatonin stimulates the nonamyloidogenic processing and inhibits the amyloidogenic processing of β-amyloid precursor protein (βAPP) by stimulating α -secretases and consequently down regulating both β- and γ-secretases at the transcriptional level. In this review, we discuss and evaluate the neuroprotective functions of melatonin in AD pathogenesis, including its role in the classical hypotheses in cellular and animal models and clinical interventions in AD patients, and suggest that with early detection, melatonin treatment is qualified to be an anti-AD therapy.

Randomised clinical trial comparing melatonin 3 mg, amitriptyline 25 mg and placebo for migraine prevention

INTRODUCTION

Melatonin has been studied in headache disorders. Amitriptyline is efficacious for migraine prevention, but its unfavourable side effect profile limits its use.

METHODS

A randomised, double-blind, placebo-controlled study was carried out. Men and women, aged 18-65 years, with migraine with or without aura, experiencing 2-8 attacks per month, were enrolled. After a 4-week baseline phase, 196 participants were randomised to placebo, amitriptyline 25 mg or melatonin 3 mg, and 178 took a study medication and were followed for 3 months (12 weeks). The primary outcome was the number of migraine headache days per month at baseline versus last month. Secondary end points were responder rate, migraine intensity, duration and analgesic use. Tolerability was also compared between groups.

RESULTS

Mean headache frequency reduction was 2.7 migraine headache days in the melatonin group, 2.2 for amitriptyline and 1.1 for placebo. Melatonin significantly reduced headache frequency compared with placebo (p=0.009), but not to amitriptyline (p=0.19). Melatonin was superior to amitriptyline in the percentage of patients with a greater than 50% reduction in migraine frequency. Melatonin was better tolerated than amitriptyline. Weight loss was found in the melatonin group, a slight weight gain in placebo and significantly for amitriptyline users.

CONCLUSIONS

Melatonin 3 mg is better than placebo for migraine prevention, more tolerable than amitriptyline and as effective as amitriptyline 25 mg.

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.

Reduced silent information regulator 1 signaling exacerbates myocardial ischemia-reperfusion injury in type 2 diabetic rats and the protective effect of melatonin

Diabetes mellitus (DM) increases myocardial oxidative stress and endoplasmic reticulum (ER) stress. Melatonin confers cardioprotective effect by suppressing oxidative damage. However, the effect and mechanism of melatonin on myocardial ischemia-reperfusion (MI/R) injury in type 2 diabetic state are still unknown. In this study, we developed high-fat diet-fed streptozotocin (HFD-STZ) rat, a well-known type 2 diabetic model, to evaluate the effect of melatonin on MI/R injury with a focus on silent information regulator 1 (SIRT1) signaling, oxidative stress, and PERK/eIF2α/ATF4-mediated ER stress. HFD-STZ treated rats were exposed to melatonin treatment in the presence or the absence of sirtinol (a SIRT1 inhibitor) and subjected to MI/R surgery. Compared with nondiabetic animals, type 2 diabetic rats exhibited significantly decreased myocardial SIRT1 signaling, increased apoptosis, enhanced oxidative stress, and ER stress. Additionally, further reduced SIRT1 signaling, aggravated oxidative damage, and ER stress were found in diabetic animals subjected to MI/R surgery. Melatonin markedly reduced MI/R injury by improving cardiac functional recovery and decreasing myocardial apoptosis in type 2 diabetic animals. Melatonin treatment up-regulated SIRT1 expression, reduced oxidative damage, and suppressed PERK/eIF2α/ATF4 signaling. However, these effects were all attenuated by SIRT1 inhibition. Melatonin also protected high glucose/high fat cultured H9C2 cardiomyocytes against simulated ischemia-reperfusion injury-induced ER stress by activating SIRT1 signaling while SIRT1 siRNA blunted this action. Taken together, our study demonstrates that reduced cardiac SIRT1 signaling in type 2 diabetic state aggravates MI/R injury. Melatonin ameliorates reperfusion-induced oxidative stress and ER stress via activation of SIRT1 signaling, thus reducing MI/R damage and improving cardiac function.

Melatonin as a preventive and curative therapy against pulmonary hypertension

Pulmonary hypertension (PH) is characterized by elevated pulmonary arterial pressure, which leads to right ventricular (RV) hypertrophy and failure. The pathophysiological mechanisms of PH remain unclear but oxidative stress is believed to contribute to RV dysfunction. Melatonin is a powerful antioxidant and is cardioprotective against ischemia-reperfusion injury and hypertension. Therefore, we hypothesized that a chronic treatment with melatonin, given as a curative or preventive therapy, may confer cardiovascular benefits in PH. PH was induced in Long Evans rats (n ≥ 6 per group), with a single subcutaneous injection of monocrotaline (MCT, 80 mg/kg). Melatonin was given daily in the drinking water, with the treatment starting either on the day of the injection of MCT (dose testing: melatonin 75 ng/L and 6 mg/kg), 14 days after the injection of MCT (curative treatment: 6 mg/kg), or 5 days before the injection (preventive treatment: 6 mg/kg). The development of PH was assessed by measuring RV hypertrophy, RV function, cardiac interstitial fibrosis, and plasma oxidative stress. Compared with controls, MCT-treated rats displayed RV hypertrophy and dysfunction, increased interstitial fibrosis, and elevated plasma oxidative stress. A chronic melatonin treatment (75 ng/L or 6 mg/kg) reduced RV hypertrophy, improved RV function and reduced plasma oxidative stress. Curative and preventive treatment improved RV functional and plasma oxidative stress parameters and reduced cardiac interstitial fibrosis. Our data demonstrate that melatonin confers cardioprotection in this model of PH. As melatonin is an inexpensive and safe drug, we propose that clinical investigation of the effects of melatonin on RV function in patients with PH should be considered.

Impact of Diet-Induced Obesity and Testosterone Deficiency on the Cardiovascular System: A Novel Rodent Model Representative of Males with Testosterone-Deficient Metabolic Syndrome (TDMetS)

INTRODUCTION

Current models of obesity utilise normogonadic animals and neglect the strong relationships between obesity-associated metabolic syndrome (MetS) and male testosterone deficiency (TD). The joint presentation of these conditions has complex implications for the cardiovascular system that are not well understood. We have characterised and investigated three models in male rats: one of diet-induced obesity with the MetS; a second using orchiectomised rats mimicking TD; and a third combining MetS with TD which we propose is representative of males with testosterone deficiency and the metabolic syndrome (TDMetS).

METHODS

Male Wistar rats (n = 24) were randomly assigned to two groups and provided ad libitum access to normal rat chow (CTRL) or a high fat/high sugar/low protein "obesogenic" diet (OGD) for 28 weeks (n = 12/group). These groups were further sub-divided into sham-operated or orchiectomised (ORX) animals to mimic hypogonadism, with and without diet-induced obesity (n = 6/group). Serum lipids, glucose, insulin and sex hormone concentrations were determined. Body composition, cardiovascular structure and function; and myocardial tolerance to ischemia-reperfusion were assessed.

RESULTS

OGD-fed animals had 72% greater fat mass; 2.4-fold greater serum cholesterol; 2.3-fold greater serum triglycerides and 3-fold greater fasting glucose (indicative of diabetes mellitus) compared to CTRLs (all p<0.05). The ORX animals had reduced serum testosterone and left ventricle mass (p<0.05). In addition to the combined differences observed in each of the isolated models, the OGD, ORX and OGD+ORX models each had greater CK-MB levels following in vivo cardiac ischemia-reperfusion insult compared to CTRLs (p<0.05).

CONCLUSION

Our findings provide evidence to support that the MetS and TD independently impair myocardial tolerance to ischemia-reperfusion. The combined OGD+ORX phenotype described in this study is a novel animal model with associated cardiovascular risk factors and complex myocardial pathology which may be representative of male patients presenting with TDMetS.

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.

The effect of melatonin supplementation on the quality of sleep and weight status in postmenopausal women

Aim of the study

We evaluated the effect of melatonin supplementation on the nutritional status of postmenopausal women.

Material and methods

The study included 56 women (51-65 years) and 25 healthy women (27-36 years). The emotional state was assessed using Hamilton Depression Rating Scale (HAM-D), the quality of sleep using Insomnia Severity Index (ISI). Body mass index (BMI) and waist-hip ratio (WHR) were also calculated. The patients were divided into 3 groups: group I (control) – 25 women with normal body weight, group II – 26 postmenopausal women with normal body weight, group III – 30 postmenopausal women with high body weight. In women from group II and III, routine laboratory tests, levels of thyroid-stimulating hormone (TSH), 17β-estradiol, prolactin, follicle-stimulating hormone (FSH) and the concentration of 6-hydroxymelatonin sulphate (6-HMS) in day/night urine fractions were determined. On the day of the examination, women remained on a liquid diet (1800 kcal). Next, a balanced diet of 1500 kcal and 5 mg of melatonin administration were recommended. The follow-up examinations were performed after 4, 8, 12, 16, 20 and 24 weeks.

Results

The patients from groups II and III showed similar mild levels of anxiety and depression and a significant degree of sleep disorders. In group III, lower urinary 6-HMS excretion was observed at night. In both groups a negative correlation was found between urinary 6-HMS excretion and the degree of sleep disorders. After 24 weeks, a statistically significant improvement of quality of sleep was obtained. A negative correlation was detected between urinary 6-HMS excretion and BMI.

Conclusion

Melatonin supplementation contributed to body weight reduction.

High carbohydrate and high fat diets protect the heart against ischaemia/reperfusion injury

Background

Although obesity is still considered a risk factor in the development of cardiovascular disorders, recent studies suggested that it may also be associated with reduced morbidity and mortality, the so-called “obesity paradox”. Experimental data on the impact of diabetes, obesity and insulin resistance on myocardial ischaemia/reperfusion injury are controversial. Similar conflicting data have been reported regarding the effects of ischaemic preconditioning on ischaemia/reperfusion injury in hearts from such animals. The aim of the present study was to evaluate the susceptibility to myocardial ischaemia/reperfusion damage in two models of diet-induced obesity as well as the effect of ischaemic and pharmacological preconditioning on such hearts.

Methods

Three groups of rats were fed with: (i) normal rat chow (controls) (ii) a sucrose-supplemented diet (DIO) (iii) a high fat diet (HFD). After 16 weeks, rats were sacrificed and isolated hearts perfused in the working mode and subjected to 35 min regional ischaemia/60 min reperfusion. Endpoints were infarct size and functional recovery. Infarct size was determined, using tetrazolium staining. Activation of PKB/Akt and ERKp44/p42 (RISK pathway) during early reperfusion was determined using Western blot. Statistical evaluation was done using ANOVA and the Bonferroni correction.

Results

Infarct sizes of non-preconditioned hearts from the two obese groups were significantly smaller than those of the age-matched controls. Ischaemic as well as pharmacological (beta-adrenergic) preconditioning with a beta2-adrenergic receptor agonist, formoterol, caused a significant reduction in infarct size of the controls, but were without effect on infarct size of hearts from the obese groups. However, ischaemic as well as beta-preconditioning caused an improvement in functional performance during reperfusion in all three groups. A clear-cut correlation between the reduction in infarct size and activation of ERKp44/p42 and PKB/Akt was not observed: The reduction in infarct size observed in the non-preconditioned hearts from the obese groups was not associated with activation of the RISK pathway. However, beta-adrenergic preconditioning caused a significant activation of ERKp44/p42, but not PKB/Akt, in all three groups.

Conclusions

Relatively long-term administration of the two obesity-inducing diets resulted in cardioprotection against ischaemia/reperfusion damage. Further protection by preconditioning was, however, without effect on infarct size, while an improvement in functional recovery was observed.

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.

Association of nocturnal melatonin secretion with insulin resistance in nondiabetic young women

Exogenous melatonin ameliorates insulin resistance in animals, while among humans, polymorphisms in the melatonin receptor gene are associated with insulin resistance. We aimed to investigate the association of endogenous nocturnal melatonin secretion with insulin resistance in humans. We analyzed the association between endogenous nocturnal melatonin secretion, estimated by measuring the main melatonin metabolite, 6-sulfatoxymelatonin, from the first morning urinary void, and the prevalence of insulin resistance based on fasting blood samples collected in a cross-sectional study of 1,075 US women (1997-1999) without diabetes, hypertension, or malignancy. Urinary 6-sulfatoxymelatonin level was standardized to urinary creatinine level; insulin resistance was defined as an insulin sensitivity index value (using the McAuley formula) less than 7.85. Logistic regression models included adjustment for age, body mass index, smoking, physical activity, alcohol intake, dietary glycemic index, family history of diabetes mellitus, blood pressure, plasma total cholesterol, uric acid, and estimated glomerular filtration rate. Higher nocturnal melatonin secretion was inversely associated with insulin levels and insulin resistance. In fully adjusted models, the odds ratio for insulin resistance was 0.45 (95% confidence interval: 0.28, 0.74) among women in the highest quartile of urinary 6-sulfatoxymelatonin:creatinine ratio compared with women in the lowest quartile. Nocturnal melatonin secretion is independently and inversely associated with insulin resistance.