Melatonin in the regulation of liver steatosis following prenatal glucocorticoid exposure

Breastfeeding and Future Cardiovascular, Kidney, and Metabolic Health-A Narrative Review

The benefits of breastfeeding for both mother and infant are generally recognized; however, the connections between breast milk, lactation, and long-term offspring health and disease remain incompletely understood. Cardiovascular-kidney-metabolic syndrome (CKMS) has become a major global public health challenge. Insufficient breast milk supply, combined with various early-life environmental factors, markedly increases the future risk of CKMS, as highlighted by the developmental origins of health and disease (DOHaD) concept. Given its richness in nutrients and bioactive components essential for infant health, this review focuses on reprogramming strategies involving breast milk to improve offspring's cardiovascular, kidney, and metabolic health. It also highlights recent experimental advances in understanding the mechanisms driving CKMS programming. Cumulatively, the evidence suggests that lactational impairment heightens the risk of CKMS development. In contrast, early interventions during the lactation period focused on animal models that leverage breast milk components in response to early-life cues show potential in improving cardiovascular, kidney, and metabolic outcomes-an area warranting further investigation and clinical translation.

Exploring Oxidative Stress and Metabolic Dysregulation in Lung Tissues of Offspring Rats Exposed to Prenatal Polystyrene Microplastics: Effects of Melatonin Treatment

Metabolomics research provides a clearer understanding of an organism's metabolic state and enables a more accurate representation of its functional performance. This study aimed to investigate changes in the metabolome of lung tissues resulting from prenatal exposure to polystyrene microplastics (PS-MPs) and to understand the underlying mechanisms of lung damage in rat offspring. We conducted metabolomic analyses of lung tissue from seven-day-old rat pups exposed to prenatal PS-MPs. Our findings revealed that prenatal exposure to PS-MPs led to significantly increased oxidative stress in lung tissues, characterized by notable imbalances in nucleic acid metabolism and altered profiles of specific amino acids. Furthermore, we evaluated the therapeutic effects of melatonin treatment on lung function in 120-day-old offspring and found that melatonin treatment significantly improved lung function and histologic change in the affected offspring. This study provides valuable biological insights into the mechanisms underlying lung damage caused by prenatal PS-MPs exposure. Future studies should focus on validating the results of animal experiments in humans, exploring additional therapeutic mechanisms of melatonin, and developing suitable protocols for clinical use.

Therapeutic benefit of melatonin in 5-fluorouracil-induced renal and hepatic injury

Nephrotoxicity and hepatotoxicity include increased oxidative stress and apoptosis; as a result, liver and kidney damage are related to its pathogenesis. These are significant side effects caused in cancer patients treated with 5-FU. In the research, 25 rats were divided into five groups, including control, 5-FU and 5-FU + 2.5, 5 and 10 mg/kg melatonin (MEL), and the protective impact of MEL against 5-FU-induced hepatorenal damage in rats was investigated. 5-FU caused significant harm, resulting in severe renal failure and histopathological changes. It also increased BUN, creatinine and hepatic function markers levels while decreasing superoxide dismutase and glutathione peroxidase activity. Additionally, 5-FU led to a notable increase in malondialdehyde content. However, MEL co-administration to rats reversed most biochemical and histologic effects. In the control and MEL + 5-FU groups, the values were comparable. The doses of MEL treatment had a significant positive impact on 5-FU-induced oxidative stress, apoptosis, lipid peroxidation and kidney damage. Our data concluded that MEL has an ameliorative effect on hepatorenal damage caused by 5-FU.

Nutritional Approaches Targeting Gut Microbiota in Oxidative-Stress-Associated Metabolic Syndrome: Focus on Early Life Programming

Metabolic syndrome (MetS) denotes a constellation of risk factors associated with the development of cardiovascular disease, with its roots potentially traced back to early life. Given the pivotal role of oxidative stress and dysbiotic gut microbiota in MetS pathogenesis, comprehending their influence on MetS programming is crucial. Targeting these mechanisms during the early stages of life presents a promising avenue for preventing MetS later in life. This article begins by examining detrimental insults during early life that impact fetal programming, ultimately contributing to MetS in adulthood. Following that, we explore the role of oxidative stress and the dysregulation of gut microbiota in the initiation of MetS programming. The review also consolidates existing evidence on how gut-microbiota-targeted interventions can thwart oxidative-stress-associated MetS programming, encompassing approaches such as probiotics, prebiotics, postbiotics, and the modulation of bacterial metabolites. While animal studies demonstrate the favorable effects of gut-microbiota-targeted therapy in mitigating MetS programming, further clinical investigations are imperative to enhance our understanding of manipulating gut microbiota and oxidative stress for the prevention of MetS.

Melatonin Use during Pregnancy and Lactation Complicated by Oxidative Stress: Focus on Offspring's Cardiovascular-Kidney-Metabolic Health in Animal Models

Cardiovascular-kidney-metabolic (CKM) syndrome has emerged as a major global public health concern, posing a substantial threat to human health. Early-life exposure to oxidative stress may heighten vulnerability to the developmental programming of adult diseases, encompassing various aspects of CKM syndrome. Conversely, the initiation of adverse programming processes can potentially be thwarted through early-life antioxidant interventions. Melatonin, originally recognized for its antioxidant properties, is an endogenous hormone with diverse biological functions. While melatonin has demonstrated benefits in addressing disorders linked to oxidative stress, there has been comparatively less focus on investigating its reprogramming effects on CKM syndrome. This review consolidates the current knowledge on the role of oxidative stress during pregnancy and lactation in inducing CKM traits in offspring, emphasizing the underlying mechanisms. The multifaceted role of melatonin in regulating oxidative stress, mediating fetal programming, and preventing adverse outcomes in offspring positions it as a promising reprogramming strategy. Currently, there is a lack of sufficient information in humans, and the available evidence primarily originates from animal studies. This opens up new avenues for novel preventive intervention in CKM syndrome.

Prenatal High-Fat Diet Combined with Microplastic Exposure Induces Liver Injury via Oxidative Stress in Male Pups

Prenatal high-fat diet (HFD) or exposure to microplastics can affect the accumulation of liver fat in offspring. We sought to determine the effects of maternal HFD intake and microplastic exposure on fatty liver injury through oxidative stress in pups. Pregnant female Sprague-Dawley rats were randomly divided into maternal HFD (experimental group) or normal control diet (NCD; control group) groups with or without microplastic exposure. As a result, the following groups were established: HFD-L (HFD + microplastics, 5 µm, 100 μg/L), HFD-H (HFD + microplastics, 5 µm, 1000 μg/L), NCD-L (NCD + microplastics, 5 µm, 100 μg/L), and NCD-H (NCD + microplastics, 5 µm, 1000 μg/L). The pups were sacrificed on postnatal day 7 (PD7). Liver histology revealed increased hepatic lipid accumulation in pups in the HFD-L and HFD-H groups compared to those in the HFD, NCD-L, NCD-H, and NCD groups on PD7. Similarly, liver TUNEL staining and cellular apoptosis were found to increase in pups in the HFD-L and HFD-H groups compared to those in the HFD, NCD-L, NCD-H, and NCD groups. The expression levels of malondialdehyde, a lipid peroxidation marker, were high in the HFD, HFD-L, and HFD-H groups; however, the highest expression was observed in the HFD-H group (p < 0.05). The levels of glutathione peroxidase, an antioxidant enzyme, decreased in the HFD, HFD-L, and HFD-H groups (p < 0.05). Overall, oxidative stress with cellular apoptosis plays a vital role in liver injury in offspring after maternal intake of HFD and exposure to microplastic; such findings may shed light on future therapeutic strategies.

Maternal hepatic immunology during pregnancy

The liver plays pivotal roles in immunologic responses, and correct hepatic adaptations in maternal immunology are required during pregnancy. In this review, we focus on anatomical and immunological maternal hepatic adaptations during pregnancy, including our recent reports in this area. Moreover, we summarize maternal pregnancy-associated liver diseases, including hyperemesis gravidarum; intrahepatic cholestasis of pregnancy; preeclampsia, specifically hemolysis, elevated liver enzymes, and low platelet count syndrome; and acute fatty liver of pregnancy. In addition, the latest information about the factors that regulate hepatic immunology during pregnancy are reviewed for the first time, including human chorionic gonadotropin, estrogen, progesterone, growth hormone, insulin like growth factor 1, oxytocin, adrenocorticotropic hormone, adrenal hormone, prolactin, melatonin and prostaglandins. In summary, the latest progress on maternal hepatic anatomy and immunological adaptations, maternal pregnancy-associated diseases and the factors that regulate hepatic immunology during pregnancy are discussed, which may be used to prevent embryo loss and abortion, as well as pregnancy-associated liver diseases.

Metabolic Syndrome Programming and Reprogramming: Mechanistic Aspects of Oxidative Stress

Metabolic syndrome (MetS) is a worldwide public health issue characterized by a set of risk factors for cardiovascular disease. MetS can originate in early life by developmental programming. Increasing evidence suggests that oxidative stress, which is characterized as an imbalance between reactive oxygen species (ROS), nitric oxide (NO), and antioxidant systems, plays a decisive role in MetS programming. Results from human and animal studies indicate that maternal-derived insults induce MetS later in life, accompanied by oxidative stress programming of various organ systems. On the contrary, perinatal use of antioxidants can offset oxidative stress and thereby prevent MetS traits in adult offspring. This review provides an overview of current knowledge about the core mechanisms behind MetS programming, with particular focus on the occurrence of oxidative-stress-related pathogenesis as well as the use of potential oxidative-stress-targeted interventions as a reprogramming strategy to avert MetS of developmental origins. Future clinical studies should provide important proof of concept for the effectiveness of these reprogramming interventions to prevent a MetS epidemic.

Prophylactic administration of carnosine and melatonin abates the incidence of apoptosis, inflammation, and DNA damage induced by titanium dioxide nanoparticles in rat livers

Although titanium dioxide nanoparticles (TDO-ns) are extensively used in the food, medicine, and cosmetic industries, discussions about the possible hazards of nanomaterials are just beginning to emerge. This study aimed to detect the inflammatory stress, oxidative stress, and apoptotic cell death induced in the livers of rats exposed to TDO-ns (600 mg/kg, particle size ≤ 100 nm). Furthermore, the modulation of these toxic effects by two potent naturally occurring antioxidants, carnosine (Carno) or melatonin (Melato), was evaluated. The co-administration of carnosine or melatonin to rats intoxicated with TDO-ns significantly attenuated the increases in serum tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), immunoglobulin G (IgG), vascular endothelial growth factor (VEGF), nitric oxide (NO), and alanine aminotransferase (ALT) levels. The two agents markedly ameliorated hepatic DNA damage and the alterations in hepatic malondialdehyde (MDA), glutathione (GSH), cytochrome P450, caspase-3, total phospholipid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and triglyceride (TG) levels. These results support the use of Carno or Melato as prophylactic agents against TDO-ns-induced liver damage.

Light and Circadian Signaling Pathway in Pregnancy: Programming of Adult Health and Disease

Light is a crucial environmental signal that affects elements of human health, including the entrainment of circadian rhythms. A suboptimal environment during pregnancy can increase the risk of offspring developing a wide range of chronic diseases in later life. Circadian rhythm disruption in pregnant women may have deleterious consequences for their progeny. In the modern world, maternal chronodisruption can be caused by shift work, jet travel across time zones, mistimed eating, and excessive artificial light exposure at night. However, the impact of maternal chronodisruption on the developmental programming of various chronic diseases remains largely unknown. In this review, we outline the impact of light, the circadian clock, and circadian signaling pathways in pregnancy and fetal development. Additionally, we show how to induce maternal chronodisruption in animal models, examine emerging research demonstrating long-term negative implications for offspring health following maternal chronodisruption, and summarize current evidence related to light and circadian signaling pathway targeted therapies in pregnancy to prevent the development of chronic diseases in offspring.

Expression of melatonin receptors and CD4 in the ovine thymus, lymph node, spleen and liver during early pregnancy

As a pineal gland hormone, melatonin acts through its receptors to modulate the immune system. The immune system is composed of primary and secondary organs, and immune organs are adapted to the presence of the fetal alloantigen during pregnancy. However, it is unclear whether melatonin affects maternal immune organs during early pregnancy in sheep. In this study, the ovine thymus, lymph node, spleen and liver were sampled at day 16 of the oestrous cycle, and at days 13, 16 and 25 of pregnancy. The expression of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2) and cluster of differentiation 4 (CD4) was detected by quantitative real-time polymerase chain reaction, Western blot and immunohistochemistry experiments. Our results showed that during early pregnancy there was an upregulation of MT1 mRNA and protein in the thymus, lymph node and liver, and there was a downregulation in the spleen. The expression of MT2 mRNA and protein was increased in the thymus but decreased in the spleen and liver, and there was no significant change in the lymph node during early pregnancy. CD4 protein was upregulated in the thymus, lymph node and liver, but there were no significant changes in the spleen during early pregnancy. In conclusion, early pregnancy induces tissue-specific expression of MT1, MT2 and CD4, which may be due to the different functions of the thymus, lymph node, spleen and liver. Further, melatonin is involved in immune regulation of the maternal thymus, lymph node, spleen and liver during early pregnancy in sheep.

Maternal exposure to environmentally relevant doses of bisphenol A causes reproductive dysfunction in F1 adult male rats: protective role of melatonin

This study investigated the protective effects of melatonin (MLT), a potent antioxidant, in male Wistar rats exposed to environmentally relevant doses of bisphenol A (BPA) in utero. Pregnant Wistar rats were randomly assigned into five groups. Group 1 (control) received 0.2 mL 1% dimethyl sulfoxide (DMSO)/99% canola oil as vehicle; group 2 received BPA at 25 μg/kg/day; group 3 received BPA at 250 μg/kg/day; group 4 received BPA at 25 μg/kg/day with concurrent MLT 1 mg/kg/day while group 5 received BPA at 250 μg/kg/day with concurrent MLT 1 mg/kg/day. Treatments were by gavage from gestational day (GD) 10-21. The BPA-treated rats showed dose-dependent significant reduction in body weight, gonosomatic index, sperm motility, livability and count. Also, BPA caused significant reduction in the levels of serum testosterone and luteinizing hormone while it caused significant increases in the levels of follicle stimulating hormone as well as estradiol. Furthermore, BPA induced testicular oxidative stress including significant decreases in the activities of testicular SOD, GSH and GPx as well as GST, increasing the levels of testicular MDA and H2O2. It further induced interstitial necrosis and germinal cell degeneration in the testis with a subsequent diminution of the tubular and luminal diameter. However, co-treatment with MLT offered protection against testicular damage induced by BPA. Melatonin is likely to protect against alterations of the male reproductive system caused by BPA through a direct action on the mechanism of anti-oxidants as well as through the inhibition of necrosis.

Protective role of melatonin in early-stage and end-stage liver cirrhosis

The liver is composed of hepatocytes, cholangiocytes, Kupffer cells, sinusoidal endothelial cells, hepatic stellate cells (HSCs) and dendritic cells; all these functional and interstitial cells contribute to the synthesis and secretion functions of liver tissue. However, various hepatotoxic factors including infection, chemicals, high‐fat diet consumption, surgical procedures and genetic mutations, as well as biliary tract diseases such as sclerosing cholangitis and bile duct ligation, ultimately progress into liver cirrhosis after activation of fibrogenesis. Melatonin (MT), a special hormone isolated from the pineal gland, participates in regulating multiple physiological functions including sleep promotion, circadian rhythms and neuroendocrine processes. Current evidence shows that MT protects against liver injury by inhibiting oxidation, inflammation, HSC proliferation and hepatocyte apoptosis, thereby inhibiting the progression of liver cirrhosis. In this review, we summarize the circadian rhythm of liver cirrhosis and its potential mechanisms as well as the therapeutic effects of MT on liver cirrhosis and earlier‐stage liver diseases including liver steatosis, nonalcoholic fatty liver disease and liver fibrosis. Given that MT is an antioxidative and anti‐inflammatory agent that is effective in eliminating liver injury, it is a potential agent with which to reverse liver cirrhosis in its early stage.

Maternal corticotropin-releasing hormone is associated with LEP DNA methylation at birth and in childhood: an epigenome-wide study in Project Viva

Background:

Corticotropin-releasing hormone (CRH) plays a central role in regulating the secretion of cortisol which controls a wide range of biological processes. Fetuses overexposed to cortisol have increased risks of disease in later life. DNA methylation may be the underlying association between prenatal cortisol exposure and health effects. We investigated associations between maternal CRH levels and epigenome-wide DNA methylation of cord blood in offsprings and evaluated whether these associations persisted into mid-childhood.

Methods:

We investigated mother-child pairs enrolled in the prospective Project Viva pre-birth cohort. We measured DNA methylation in 257 umbilical cord blood samples using the HumanMethylation450 Bead Chip. We tested associations of maternal CRH concentration with cord blood cells DNA methylation, adjusting the model for maternal age at enrollment, education, maternal race/ethnicity, pre-pregnancy body mass index, parity, gestational age at delivery, child sex, and cell-type composition in cord blood. We further examined the persistence of associations between maternal CRH levels and DNA methylation in children’s blood cells collected at mid-childhood (N = 239, age: 6.7–10.3 years) additionally adjusting for the children’s age at blood drawn.

Results:

Maternal CRH levels are associated with DNA methylation variability in cord blood cells at 96 individual CpG sites (False Discovery Rate < 0.05). Among the 96 CpG sites, we identified 3 CpGs located near the LEP gene. Regional analyses confirmed the association between maternal CRH and DNA methylation near LEP. Moreover, higher maternal CRH levels were associated with higher blood-cell DNA methylation of the promoter region of LEP in mid-childhood (P < 0.05, β = 0.64, SE = 0.30).

Conclusion:

In our cohort, maternal CRH was associated with DNA methylation levels in newborns at multiple loci, notably in the LEP gene promoter. The association between maternal CRH and LEP DNA methylation levels persisted into mid-childhood.

Regulation of Leptin Methylation Not via Apoptosis by Melatonin in the Rescue of Chronic Programming Liver Steatosis

We examined the mechanisms of chronic liver steatosis after prenatal dexamethasone exposure and whether melatonin rescues adult offspring with liver steatosis. Melatonin rescued prenatal dexamethasone-exposed livers with steatosis in young rats. Sprague-Dawley rats pregnant at gestational day 14–21 were administered with intraperitoneal dexamethasone (DEX) or prenatal dexamethasone and melatonin between gestational day 14 and postnatal day ~120 (DEX+MEL). Chronic programming effects in the liver were assessed at day ~120. Liver steatosis increased in the DEX compared with that in the vehicle group and decreased in the DEX+MEL group (p < 0.05), with no changes in cellular apoptosis. Expression of leptin and its receptor decreased in the DEX (p < 0.05) and increased in the DEX+MEL group (p < 0.05), as revealed by RT-PCR and Western blotting. Tumor necrosis factor alpha (TNF-α) and interleukin (IL)-6 expression increased in the DEX group compared with that in the vehicle group and decreased in the DEX+MEL group (p < 0.05). Liver DNA methyltransferase activity and leptin methylation increased in the DEX group (p < 0.05) and decreased in the DEX+MEL group (p < 0.05), with no changes in HDAC activity. Thus, prenatal dexamethasone induces liver steatosis at ~120 days via altered leptin expression and liver inflammation without leptin resistance. Melatonin reverses leptin methylation and expression and decreases inflammation and chronic liver steatosis not via apoptosis or histone deacetylation (HDAC).

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

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

Prenatal dexamethasone and postnatal high-fat diet have a synergistic effect of elevating blood pressure through a distinct programming mechanism of systemic and adipose renin-angiotensin systems

Background

Hypertension may result from high-fat (HF) diet induced-obesity and overexposure to glucocorticoids in utero. Recent studies demonstrated the potent contribution of adipose tissue’s renin-angiotensin system (RAS) to systemic RAS, which plays a key role in regulating blood pressure (BP). In this study, we investigated the effects of prenatal dexamethasone (DEX) exposure and postnatal HF diet on RAS of adipose tissue.

Methods

RAS and BP of 6-month old rats exposed to prenatal DEX and/or postnatal HF diet were examined.

Results

Prenatal DEX plus postnatal HF exerted a synergistic effect on systolic BP. Prenatal DEX exposure suppressed plasma angiotensin (ANG) I and ANG II, whereas postnatal HF suppressed plasma ANG-(1–7) level. Prenatal DEX increased prorenin receptor and renin levels, but suppressed angiotensinogen (AGT) and angiotensin-converting-enzyme 1 (ACE1) mRNA expressions in adipose tissue. Postnatal HF increased AGT mRNA expression, but suppressed prorenin receptor, renin, ACE2, ANG II type 2 receptor (AT2R), and Mas receptor (MasR) mRNA expression levels.

Conclusions

Prenatal GC exposure altered the ACE1/ANG II/ANG II type 1 receptor (AT1R) axis, whereas postnatal HF negatively impacted the ACE2/ANG-(1–7)/MasR axis. Prenatal DEX exposure and postnatal HF synergistically elevated BP through a distinct programming mechanism of systemic and adipose RAS. Adipose RAS might be a target for precise hypertension treatment.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0701-0) contains supplementary material, which is available to authorized users.

The Effects of Melatonin on Elevated Liver Enzymes during Statin Treatment

Taking statins can cause increase in the level of aspartate and alanine aminotransferase. The aim of this study was to assess the usefulness of melatonin in counteracting the adverse hepatic events from statins. Methods. The research program included 60 patients (aged 47–65 years, 41 women and 19 men) with hyperlipidemia taking atorvastatin or rosuvastatin at a dose of 20–40 mg daily. The patients were randomly allocated in two groups. Group I (n = 30) was recommended to take the same statin at a standardized daily dose of 20 mg together with melatonin at a dose of 2 × 5 mg. Group II (n = 30) patients took statin with placebo at the same dose and time of the day. Follow-up laboratory tests (AST, ALT, GGT, and ALP) were evaluated after 2, 4, and 6 months of treatment. Results. In Group I the levels of all enzymes decreased after 6 months, particularly AST, 97,2 ± 19,1 U/L versus 52,8 ± 12,3 U/L (p < 0,001); ALT, 87,4 ± 15,6 U/L versus 49,8 ± 14,5 U/L (p < 0,001); and GGT, 84,1 ± 14,8 U/L versus 59,6 U/L (p < 0,001). Conclusion. Melatonin exerts a hepatoprotective effect in patients taking statins.

Effects of Melatonin on Liver Injuries and Diseases

Liver injuries and diseases are serious health problems worldwide. Various factors, such as chemical pollutants, drugs, and alcohol, could induce liver injuries. Liver diseases involve a wide range of liver pathologies, including hepatic steatosis, fatty liver, hepatitis, fibrosis, cirrhosis, and hepatocarcinoma. Despite all the studies performed up to now, therapy choices for liver injuries and diseases are very few. Therefore, the search for a new treatment that could safely and effectively block or reverse liver injuries and diseases remains a priority. Melatonin is a well-known natural antioxidant, and has many bioactivities. There are numerous studies investigating the effects of melatonin on liver injuries and diseases, and melatonin could regulate various molecular pathways, such as inflammation, proliferation, apoptosis, metastasis, and autophagy in different pathophysiological situations. Melatonin could be used for preventing and treating liver injuries and diseases. Herein, we conduct a review summarizing the potential roles of melatonin in liver injuries and diseases, paying special attention to the mechanisms of action.

Developmental Programming of Adult Disease: Reprogramming by Melatonin?

Adult-onset chronic non-communicable diseases (NCDs) can originate from early life through so-called the "developmental origins of health and disease" (DOHaD) or "developmental programming". The DOHaD concept offers the "reprogramming" strategy to shift the treatment from adulthood to early life, before clinical disease is apparent. Melatonin, an endogenous indoleamine produced by the pineal gland, has pleiotropic bioactivities those are beneficial in a variety of human diseases. Emerging evidence support that melatonin is closely inter-related to other proposed mechanisms contributing to the developmental programming of a variety of chronic NCDs. Recent animal studies have begun to unravel the multifunctional roles of melatonin in many experimental models of developmental programming. Even though some progress has been made in research on melatonin as a reprogramming strategy to prevent DOHaD-related NCDs, future human studies should aim at filling the translational gap between animal models and clinical trials. Here, we review several key themes on the reprogramming effects of melatonin in DOHaD research. We have particularly focused on the following areas: mechanisms of developmental programming; the interrelationship between melatonin and mechanisms underlying developmental programming; pathophysiological roles of melatonin in pregnancy and fetal development; and insight provided by animal models to support melatonin as a reprogramming therapy. Rates of NCDs are increasing faster than anticipated all over the world. Hence, there is an urgent need to understand reprogramming mechanisms of melatonin and to translate experimental research into clinical practice for halting a growing list of DOHaD-related NCDs.

Melatonin Alleviates Liver Apoptosis in Bile Duct Ligation Young Rats

Bile duct ligation (BDL)-treated rats display cholestasis and liver damages. The potential protective activity of melatonin in young BDL rats in terms of apoptosis, mitochondrial function, and endoplasmic reticulum (ER) homeostasis has not yet been evaluated. Three groups of young male Sprague-Dawley rats were used: one group received laparotomy (Sham), a second group received BDL for two weeks (BDL), and a third group received BDL and intraperitoneal melatonin (100 mg/day) for two weeks (BDL + M). BDL group rats showed liver apoptosis, increased pro-inflamamtory mediators, caspases alterations, anti-apoptotic factors changes, and dysfunction of ER homeostasis. Melatonin effectively reversed apoptosis, mainly through intrinsic pathway and reversed ER stress. In addition, in vitro study showed melatonin exerted its effect mainly through the melatonin 2 receptor (MT2) in HepG2 cells. In conclusion, BDL in young rats caused liver apoptosis. Melatonin rescued the apoptotic changes via the intrinsic pathway, and possibly through the MT2 receptor. Melatonin also reversed ER stress induced by BDL.

Plasma Prostaglandin E2 Levels Correlated with the Prevention of Intravenous Immunoglobulin Resistance and Coronary Artery Lesions Formation via CD40L in Kawasaki Disease

BACKGROUND

A form of systemic vasculitis, Kawasaki disease (KD) occurs most frequently in children under the age of five years old. Previous studies have found that Prostaglandin E2 (PGE2) correlates with KD, although the related mechanisms are still unknown. CD40L may also be a marker of vasculitis in KD, so this study focuses on PGE2 and CD40L expression in KD.

MATERIALS AND METHODS

This study consisted of a total of 144 KD patients, whose intravenous immunoglobulin (IVIG)/coronary arterial lesion (CAL) formation resistance was evaluated. PGE2 levels were evaluated in vitro to study the effect of CD40L on CD4+ T lymphocytes.

RESULTS

PGE2 levels significantly increased after IVIG treatment (p<0.05), especially in patients who responded to initial IVIG treatment (p = 0.004) and for patients without CAL formation (p = 0.016). Furthermore, an in vitro study revealed that IVIG acted as a trigger for PGE2 expression in the acute-stage mononuclear cells of KD patients. According to our findings, both IVIG and PGE2 can impede surface CD40L expressions on CD4+ T lymphocytes (p<0.05).

CONCLUSIONS

The results of this study are among the first to find that plasma PGE2 is correlated with the prevention of IVIG resistance and CAL formation through CD40L in KD.

Hepcidin-Induced Iron Deficiency Is Related to Transient Anemia and Hypoferremia in Kawasaki Disease Patients

Kawasaki disease (KD) is a type of systemic vasculitis that primarily affects children under the age of five years old. For sufferers of KD, intravenous immunoglobulin (IVIG) has been found to successfully diminish the occurrence of coronary artery lesions. Anemia is commonly found in KD patients, and we have shown that in appropriately elevated hepcidin levels are related to decreased hemoglobin levels in these patients. In this study, we investigated the time period of anemia and iron metabolism during different stages of KD. A total of 100 patients with KD and 20 control subjects were enrolled in this study for red blood cell and hemoglobin analysis. Furthermore, plasma, urine hepcidin, and plasma IL-6 levels were evaluated using enzyme-linked immunosorbent assay in 20 KD patients and controls. Changes in hemoglobin, plasma iron levels, and total iron binding capacity (TIBC) were also measured in patients with KD. Hemoglobin, iron levels, and TIBC were lower (p < 0.001, p = 0.009, and p < 0.001, respectively) while plasma IL-6 and hepcidin levels (both p < 0.001) were higher in patients with KD than in the controls prior to IVIG administration. Moreover, plasma hepcidin levels were positively and significantly correlated with urine hepcidin levels (p < 0.001) prior to IVIG administration. After IVIG treatment, plasma hepcidin and hemoglobin levels significantly decreased (both p < 0.001). Of particular note was a subsequent gradual increase in hemoglobin levels during the three weeks after IVIG treatment; nevertheless, the hemoglobin levels stayed lower in KD patients than in the controls (p = 0.045). These findings provide a longitudinal study of hemoglobin changes and among the first evidence that hepcidin induces transient anemia and hypoferremia during KD's acute inflammatory phase.

Postnatal High-Fat Diet Increases Liver Steatosis and Apoptosis Threatened by Prenatal Dexamethasone through the Oxidative Effect

The objective of this study was to investigate cellular apoptosis in prenatal glucocorticoid overexposure and a postnatal high fat diet in rats. Pregnant Sprague-Dawley rats at gestational days 14 to 21 were administered saline (vehicle) or dexamethasone and weaned onto either a normal fat diet or a high fat diet for 180 days; in total four experimental groups were designated, i.e., vehicle treated group (VEH), dexamethasone treated group (DEX), vehicle treated plus high-fat diet (VHF), and dexamethasone treated plus high-fat diet (DHF). Chronic effects of prenatal liver programming were assessed at postnatal day 180. The apoptotic pathways involved proteins were analyzed by Western blotting for their expressions. Apoptosis and liver steatosis were also examined by histology. We found that liver steatosis and apoptosis were increased in the DHF, DEX, and VHF treated groups, and that the DHF treated group was increased at higher levels than the DEX and VHF treated groups. The expression of leptin was decreased more in the DHF treated group than in the DEX and VHF treated groups. Decreased peroxisome proliferator-activated receptor-gamma coactivator 1α, phosphoinositide-3-kinase, manganese superoxide dismutase and increased malondialdehyde expression levels were seen in DHF treated group relative to the DEX treated group. The DHF treated group exhibited higher levels of oxidative stress, apoptosis and liver steatosis than the DEX treated group. These results indicate that the environment of high-fat diet plays an important role in the development of liver injury after prenatal stress.

Potential epigenetic mechanism in non-alcoholic Fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive fat accumulation in the liver. It ranges from simple steatosis to its more aggressive form, non-alcoholic steatohepatitis (NASH), which may develop into hepatic fibrosis, cirrhosis, or hepatocellular carcinoma (HCC) if it persists for a long time. However, the exact pathogenesis of NAFLD and the related metabolic disorders remain unclear. Epigenetic changes are stable alterations that take place at the transcriptional level without altering the underlying DNA sequence. DNA methylation, histone modifications and microRNA are among the most common forms of epigenetic modification. Epigenetic alterations are involved in the regulation of hepatic lipid metabolism, insulin resistance, mitochondrial damage, oxidative stress response, and the release of inflammatory cytokines, all of which have been implicated in the development and progression of NAFLD. This review summarizes the current advances in the potential epigenetic mechanism of NAFLD. Elucidation of epigenetic factors may facilitate the identification of early diagnositic biomarkers and development of therapeutic strategies for NAFLD.

Effects of melatonin on prenatal dexamethasone-induced epigenetic alterations in hippocampal morphology and reelin and glutamic acid decarboxylase 67 levels

Prenatal glucocorticoid exposure causes brain damage in adult offspring; however, the underlying mechanisms remain unclear. Melatonin has been shown to have beneficial effects in compromised pregnancies. Pregnant Sprague-Dawley rats were administered vehicle (VEH) or dexamethasone between gestation days 14 and 21. The programming effects of prenatal dexamethasone exposure on the brain were assessed at postnatal days (PND) 7, 42, and ∼120. Melatonin was administered from PND21 to the rats exposed to dexamethasone, and the outcome was assessed at ∼PND120. In total, there were four groups: VEH, vehicle plus melatonin (VEHM), prenatal dexamethasone-exposure (DEX), and prenatal dexamethasone exposure plus melatonin (DEXM). Spatial memory, gross hippocampal morphology, and hippocampal biochemistry were examined. Spatial memory assessed by the Morris water maze showed no significant differences among the four groups. Brain magnetic resonance imaging showed that all rats with prenatal dexamethasone exposure (DEX + DEXM) exhibited increased T2-weighted signals in the hippocampus. There were no significant differences in the levels of mRNA expression of hippocampal reln, which encodes reelin, and GAD1, which encodes glutamic acid decarboxylase 67, at PND7. At both PND42 and ∼PND120, reln and GAD1 mRNA expression levels were decreased. At ∼PND120, melatonin restored the reduced levels of hippocampal reln and GAD1 mRNA expression in the DEXM group. In addition, melatonin restored the reln mRNA expression levels by (1) reducing DNA methyltransferase 1 (DNMT1) mRNA expression and (2) reducing the binding of DNMT1 and the methyl-CpG binding protein 2 (MeCP2) to the reln promoter. The present study showed that prenatal dexamethasone exposure induced gross alterations in hippocampal morphology and reduced the levels of hippocampal mRNA expression of reln and GAD1. Spatial memory was unimpaired. Thus, melatonin had a beneficial effect in restoring hippocampal reln mRNA expression by reducing DNMT1 and MeCP2 binding to the reln promoter.

Cross-fostering increases TH1/TH2 expression in a prenatal dexamethasone exposure rat model

BACKGROUND

Prenatal dexamethasone exposure has been reported to increase allergy potential in childhood possibly by interference with normal immunological development in utero. This study investigated the effects of prenatal dexamethasone on T helper cell immune responses in a rat model.

METHODS

Pregnant rats received either dexamethasone 0.1 mg/kg/day or normal saline from gestational day 14-21. Off-springs were cared for by their biological mother, or cross-fostered by the opposing group. Spleen and blood samples were collected at post-natal day 7 and 120 and tested for mRNA expression and plasma cytokine levels of Th1/Th2/Th17 immune response.

RESULTS

Both Th1 (T-bet) and Th2 (GATA-3) mRNA expression were shown to have a significant increase in the prenatal dexamethasone exposure group at day 120 (p<0.05). The plasma levels for Th1 (IFNγ and IL-2) and Th2 (IL-4, IL-5, IL-13) were found to have no significant differences between the two group (p>0.05). The mRNA expression of Th17 (RORγt) showed a significant decrease at post-natal day 120 as well as the plasma level of IL-17A at day 7 (11.21±1.67 vs. 6.23±1.06 pg/ml, p = 0.02). Cross-fostering by a dexamethasone exposed mother resulted in a significant increase in Th1/Th2 mRNA expression (p<0.05) and decrease of Th17.

CONCLUSIONS

Prenatal dexamethasone exposure increased Th1, Th2 and decreased Th17 expression. Cross-fostering by a dexamethasone exposed mother results in more prominent increase of Th1 and Th2 expression.

Melatonin regulates aging and neurodegeneration through energy metabolism, epigenetics, autophagy and circadian rhythm pathways

Brain aging is linked to certain types of neurodegenerative diseases and identifying new therapeutic targets has become critical. Melatonin, a pineal hormone, associates with molecules and signaling pathways that sense and influence energy metabolism, autophagy, and circadian rhythms, including insulin-like growth factor 1 (IGF-1), Forkhead box O (FoxOs), sirtuins and mammalian target of rapamycin (mTOR) signaling pathways. This review summarizes the current understanding of how melatonin, together with molecular, cellular and systemic energy metabolisms, regulates epigenetic processes in the neurons. This information will lead to a greater understanding of molecular epigenetic aging of the brain and anti-aging mechanisms to increase lifespan under healthy conditions.