Effect of melatonin on age induced changes in daily serotonin rhythms in suprachiasmatic nucleus of male Wistar rat

Day time-restricted feeding shows differential synchronizing effects on age-related changes of serotonin metabolism in SCN and the pineal gland in male Wistar rats

The circadian timing system is synchronized by the environmental photic and non-photic signals. Light is the major cue that entrains the master circadian oscillator located in suprachiasmatic nucleus (SCN). With aging condition ocular light impairs because of the age-related deficiencies in the eye as a result the clock becomes less sensitive to light. In such case non-photic cues may play a major role in synchronizing the clock. Earlier studies have linked altered meal timings to induce many physiological changes including serotonin in different brain regions such as hypothalamus, brain stem and striatum. Much is not known about the effect of timed food restriction as a non-photic stimulus on serotonergic system in SCN under aging condition. We report here the synchronizing effects of time-restricted feeding (TRF) as a non-photic stimulus on serotonin and its related metabolites in the SCN and pineal gland of male Wistar rats upon aging. Under food restriction daily rhythmicity of serotonin 5-HT and 5-HTOH was abolished whereas NAS, 5-MIAA and NAT showed a significant decrease in their daily pulses upon food restriction in 3 months (m) old rats. Under forced day time feeding schedule the mean 24 h levels of serotonin have significantly decreased in 12 and 24 m old animals in SCN and pineal gland. Most of the serotonin metabolites in the SCN and pineal gland of 12 and 24 m old ad libitum fed group rats have shown rhythmicity. 5-HT, NAS, MEL and NAT have shown daily rhythm in the SCN of 12 and 24 m old rats whereas 5-MIAA and 5-MTOH did not show daily rhythm in both the age groups. The mean 24 h levels of 5-HTP, 5-HIAA, 5-MIAA, 5-MTOH, MEL and NAT were increased in the pineal gland of 12 and 24 months old rats. This work help demonstrate the role of TRF in synchronising age induced desynchronization in serotonin metabolome.

Multiplexed Visualization Method to Explore Complete Targeting Regulatory Relationships Among Circadian Genes for Insomnia Treatment

Understanding the complete map of melatonin synthesis, the information transfer network among circadian genes in pineal gland, promises to resolve outstanding issues in endocrine systems and improve the clinical diagnosis and treatment level of insomnia, immune disease and hysterical depression. Currently, some landmark studies have revealed some genes that regulate circadian rhythm associated with melatonin synthesis. However, these studies don't give a complete map of melatonin synthesis, as transfer information among circadian genes in pineal gland is lost. New biotechnology, integrates dynamic sequential omics and multiplexed imaging method, has been used to visualize the complete process of melatonin synthesis. It is found that there are two extremely significant information transfer processes involved in melatonin synthesis. In the first stage, as the light intensity decreased, melatonin synthesis mechanism has started, which is embodied in circadian genes, Rel, Polr2A, Mafk, and Srbf1 become active. In the second stage, circadian genes Hif1a, Bach1, Clock, E2f6, and Per2 are regulated simultaneously by four genes, Rel, Polr2A, Mafk, and Srbf1 and contribute genetic information to Aanat. The expeditious growth in this technique offer reference for an overall understanding of gene-to-gene regulatory relationship among circadian genes in pineal gland. In the study, dynamic sequential omics and the analysis process well provide the current state and future perspectives to better diagnose and cure diseases associated with melatonin synthesis disorder.

Melatonin supplementation over different time periods until ageing modulates genotoxic parameters in mice

The ageing process is a multifactorial phenomenon, associated with decreased physiological and cellular functions and an increased propensity for various degenerative diseases. Studies on melatonin (N-acetyl-5-methoxytryptamine), a potent antioxidant, are gaining attention since melatonin production declines with advancing age. Hence, the aim of this study was to evaluate the effects of chronic melatonin consumption on genotoxic and mutagenic parameters of old Swiss mice. Herein, 3-month-old Swiss albino male mice (n = 240) were divided into eight groups and subdivided into two experiments: first (three groups): natural ageing experiment; second (five groups): animals that started water or melatonin supplementation at different ages (3, 6, 12 and 18 months) until 21 months. After 21 months, the animals from the second experiment were euthanized to perform the comet assay, micronucleus test and western blot analysis. The results demonstrated that melatonin prolonged the life span of the animals. Relative to genomic instability, melatonin was effective in reducing DNA damage caused by ageing, presenting antigenotoxic and antimutagenic activities, independently of initiation age. The group receiving melatonin for 18 months had high levels of APE1 and OGG1 repair enzymes. Conclusively, melatonin presents an efficient antioxidant mechanism aiding modulating genetic and physiological alterations due to ageing.

Therapeutic effects of hydro-alcoholic leaf extract of Withania somnifera on age-induced changes in daily rhythms of Sirt1, Nrf2 and Rev-erbα in the SCN of male Wistar rats

The temporal expression pattern of the circadian clock genes are known to be altered/attenuated with advance in age. Withania somnifera (WS) essentially consists of numerous active constituents including withanolides is known to have antioxidant, anti-inflammatory and adaptogenic properties. We have earlier demonstrated therapeutic effects of hydro-alcoholic leaf extract of WS on the age-induced alterations in the levels and daily rhythms of various clock genes such as rBmal1, rPer1, rPer2 and rCry1. We have now studied effects of hydro-alcoholic leaf extract of WS on the age-induced alterations in the levels and daily rhythms of expression of SIRT1 (an NAD⁺ dependent histone deacetylase and a modulator of clock) and NRF2 (a clock controlled gene and a master transcription factor regulating various endogenous antioxidant enzymes) in addition to rRev-erbα in SCN of adult [3 months (m)], middle-aged (12 m) and old-aged (24 m) male Wistar rats. The daily rhythms of rNrf2 expression showed 6 h phase delay in middle age and 12 h phase advance in old age. WS restored rSirt1 daily rhythms and phase in old age whereas it restored the phase of rNrf2 in the SCN of both middle and old aged animals. At protein level, SIRT1 expression showed phase advances in 12 m and 24 m whereas NRF2 daily rhythms were abolished in both the age groups. WS restored the phase and daily rhythms of SIRT1 as well as NRF2 in 12 m old rats. However, rRev-erbα expression was found insensitive to WS treatment in all the age groups studied. Pairwise correlation analysis demonstrated significant stoichiometric interactions among rSirt1, rNrf2 and rRev-erbα in 3 m which altered with aging significantly. WS treatment resulted in differential restorations of such interactions.

The role of melatonin, a multitasking molecule, in retarding the processes of ageing

Biological ageing is generally accompanied by a gradual loss of cellular functions and physiological integrity of organ systems, the consequential enhancement of vulnerability, senescence and finally death. Mechanisms which underlie ageing are primarily attributed to an array of diverse but related factors including free radical-induced damage, dysfunction of mitochondria, disruption of circadian rhythms, inflammaging, genomic instability, telomere attrition, loss of proteostasis, deregulated sensing of nutrients, epigenetic alterations, altered intercellular communication, and decreased capacity for tissue repair. Melatonin, a prime regulator of human chronobiological and endocrine physiology, is highly reputed as an antioxidant, immunomodulatory, antiproliferative, oncostatic, and endocrine-modulatory molecule. Interestingly, several recent reports support melatonin as an anti-ageing agent whose multifaceted functions may lessen the consequences of ageing. This review depicts four categories of melatonin's protective effects on ageing-induced molecular and structural alterations. We also summarize recent findings related to the function of melatonin during ageing in various tissues and organs.

Mitochondrial dysfunction in metabolism and ageing: shared mechanisms and outcomes?

Mitochondria are key in the metabolism of aerobic organisms and in ageing progression and age-related diseases. Mitochondria are essential for obtaining ATP from glucose and fatty acids but also in many other essential functions in cells including aminoacids metabolism, pyridine synthesis, phospholipid modifications and calcium regulation. On the other hand, the activity of mitochondria is also the principal source of reactive oxygen species in cells. Ageing and chronic age-related diseases are associated with the deregulation of cell metabolism and dysfunction of mitochondria. Cell metabolism is controlled by three major nutritional sensors: mTOR, AMPK and Sirtuins. These factors control mitochondrial biogenesis and dynamics by regulating fusion, fission and turnover through mito- and autophagy. A complex interaction between the activity of these nutritional sensors, mitochondrial biogenesis rate and dynamics exists and affect ageing, age-related diseases including metabolic disease. Further, mitochondria maintain a constant communication with nucleus modulating gene expression and modifying epigenetics. In this review we highlight the importance of mitochondria in ageing and the repercussion in the progression of age-related diseases and metabolic disease.

Daily NO rhythms in peripheral clocks in aging male Wistar rats: protective effects of exogenous melatonin

In mammals suprachiasmatic nucleus (SCN), acts as a light entrainable master clock and by generation of temporal oscillations regulates the peripheral organs acting as autonomous clocks resulting in overt behavioral and physiological rhythms. SCN also controls synthesis and release of melatonin (hormonal message for darkness) from pineal. Nitric Oxide (NO) acts as an important neurotransmitter in generating the phase shifts of circadian rhythms and participates in sleep-wake processes, maintenance of vascular tone as well as signalling and regulating inflammatory processes. Aging is associated with disruption of circadian timing system and decline in endogenous melatonin leading to several physiological disorders. Here we report the effect of aging on NO daily rhythms in various peripheral clocks such as kidney, intestine, liver, heart, lungs and testis. NO levels were measured at zeitgeber time (ZT) 0, 6, 12 and 18 in these tissues using Griess assay in male Wistar rats. Aging resulted in alteration of NO levels as well as phase of NO in both 12 and 24 months groups. Correlation analysis demonstrated loss of stoichiometric interaction between the various peripheral clocks with aging. Age induced alterations in NO daily rhythms were found to be most significant in liver and, interestingly least in lungs. Neurohormone melatonin, an endogenous synchroniser and an antiaging agent decreases with aging. We report further differential restoration with exogenous melatonin administration of age induced alterations in NO daily rhythms and mean levels in kidney, intestine and liver and the stoichiometric interactions between the various peripheral clocks.

Daily rhythms of serotonin metabolism and the expression of clock genes in suprachiasmatic nucleus of rotenone-induced Parkinson's disease male Wistar rat model and effect of melatonin administration

The circadian system in suprachiasmatic nucleus (SCN) involves regulated serotonin levels and coordinated expression of various clock genes. To understand circadian disfunction in the age-related neurodegenerative disorder Parkinson's disease (PD), the rotenone-induced PD (RIPD) male Wistar rat model was used. The alterations in the rhythmic dynamic equilibrium of interactions between the various components of serotonin metabolism and the molecular clock were measured. There was significant decrease in the mean 24 h levels of tryptophan, 5-hydroxytryptophan (5-HTP), serotonin (5-HT), N-acetyl serotonin (NAS) and melatonin (MEL) by approximately 63, 51, 76 and 96% respectively ( p ≤ 0.05). However significant increase in 5-methoxy indole acetic acid (5-MIAA), 5-methoxy tryptophol (5-MTOH), 5-hydroxy tryptophol (5-HTOH) indicated increased serotonin catabolism with the abolition of daily rhythms of MEL, 5-HTP and 5-MIAA in RIPD. 24 h mean levels of rPer1, rCry1, rBmal1 reduced by about 0.5, 0.74 and 0.39-fold and increased for rPer2 by about 1.7-fold. The daily pulse of rPer2, rCry1, rCry2 and rBmal1 significantly decreased by 0.36, 0.6, 0.14, 0.1 and 0.2-fold. As melatonin, an antioxidant and an endogenous synchronizer of rhythm declined in RIPD male Wistar rat model, the effects of melatonin-administration on the rhythmic expression of various clock genes were studied. Interestingly, melatonin-administration resulted in restoration of the phase of rPer1 daily rhythm in RIPD indicating differential sensitivity of various clock components towards melatonin. The animals which were administered both rotenone and MEL for 48 days interestingly showed neuroprotective effects in dark phase on correlations between expression of various genes.

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.

Differential role of melatonin in restoration of age-induced alterations in daily rhythms of expression of various clock genes in suprachiasmatic nucleus of male Wistar rats

Aging is associated with changes in several basic parameters of circadian rhythms in mammals leading to circadian dysfunction. The hypothalamic Suprachiasmatic nucleus (SCN) regulates neuronal, endocrine and behavioral rhythms through the expression of various clock genes and release of melatonin from pineal gland. In the present study, we investigated the effect of aging on daily rhythms of various clock genes such as rPer1, rPer2, rCry1, rCry2 and rBmal1 in the SCN of male Wistar rats. The m-RNA expression levels of these genes were studied by using quantitative Polymerase Chain Reaction (qPCR) in 3 age groups [3 (adult), 12 and 24 month (m)] at variable time points (Zeitgeber time (ZT)-0, 6, 12 and 18). The m-RNA expression for all genes studied was rhythmic in SCN of adult rats with maximum for rPer1 at ZT-6, rPer2, rCry1 and rCry2 at ZT-12 and rBmal1 at ZT-18. However in 12 and 24 m, the phases of expression of these genes were significantly altered with abolition of daily rhythms of rCry1, rCry2 and rBmal1 in 24 m. Melatonin, messenger of darkness, an endogenous synchronizer of rhythm, an antioxidant and an antiaging drug, declines with aging. We therefore studied the effects of melatonin administered subcutaneously at 1 h before the onset of darkness (ZT-11) for 11 days on age induced desynchronization in expression of these genes. We report here differential restoration of daily rhythm, phase, levels and stoichiometric interaction of m-RNA expression of these genes in various age groups in rat SCN with melatonin treatment.

Effect of restricted feeding on nocturnality and daily leptin rhythms in OVLT in aged male Wistar rats

Circadian system has direct relevance to the problems of modern lifestyle, shift workers, jet lag etc. To understand non-photic regulation of biological clock, the effects of restricted feeding (RF) on locomotor activity and daily leptin immunoreactivity (ir) rhythms in three age groups [3, 12 and 24 months (m)] of male Wistar rats maintained in light:dark (LD) 12:12 h conditions were studied. Leptin-ir was examined in the suprachiasmatic nucleus (SCN), the medial preoptic area (MPOA) and organum vasculosum of the lamina terminalis (OVLT). Reversal of feeding time due to restricted food availability during daytime resulted in switching of the animals from nocturnality to diurnality with significant increase in day time activity and decrease in night time activity. The RF resulted in % diurnality of approximately 32, 29 and 73 from % nocturnality of 82, 92 and 89 in control rats of 3, 12 and 24 m age, respectively. The increase in such switching from nocturnality to diurnality with restricted feeding was found to be robust in 24 m rats. The OVLT region showed daily leptin-ir rhythms with leptin-ir maximum at ZT-0 in all the three age groups. However leptin-ir levels were minimum at ZT-12 in 3 and 12 m though at ZT-18 in 24 m. In addition the mean leptin-ir levels decreased with increase in food intake and body weight significantly in RF aged rats. Thus we report here differential effects of food entrained regulation in switching nocturnality to diurnality and daily leptin-ir rhythms in OVLT in aged rats.

Aging signaling pathways and circadian clock-dependent metabolic derangements

The circadian clock machinery orchestrates organism metabolism to ensure that development, survival, and reproduction are attuned to diurnal environmental variations. For unknown reasons, there is a decline in circadian rhythms with age, concomitant with declines in the overall metabolic tissue homeostasis and changes in the feeding behavior of aged organisms. This disruption of the relationship between the clock and the nutrient-sensing networks might underlie age-related diseases; overall, greater knowledge of the molecular mediators of and variations in clock networks during lifespan may shed light on the aging process and how it may be delayed. In this review we address the complex links between the circadian clock, metabolic (dys)functions, and aging in different model organisms.

Melatonin administration differentially affects age-induced alterations in daily rhythms of lipid peroxidation and antioxidant enzymes in male rat liver

A central clock/pacemaker, suprachiasmatic nuclei of the hypothalamus coordinates and entrains circadian oscillations in the peripheral tissues such as the liver, kidney, heart, lungs etc. called peripheral clocks. These also have endogenous circadian oscillations. The circadian rhythms of antioxidants present in cytosol signify redox state of the cell during day/night cycle. The liver has a major impact on homeostasis through its control on serum protein composition and plays a pivotal role in the metabolism of nutrients, drugs, hormones, and metabolic waste products and undergoes substantial changes in structure and function upon aging. In present study, the temporal patterns of oxidative stress indicators in liver were studied. Daily rhythms of lipid peroxidation end products, reduced glutathione (GSH), oxidized glutathione (GSSG) and antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were studied in liver at variable time points (Zeitgeber Time (ZT) 0, 6, 12 and 18) in three age groups: 3 (adult), 12 and 24 months old male Wistar rats. There was increase in oxidative stress in 12 and 24 months old rats indicated through a significant increase in lipid peroxidation, decrease in GSH/GSSG ratio and antioxidant enzyme activities. In 3 months old rats, lipid peroxidation was maximum at ZT-12 whereas GSH, SOD and CAT activities were minimum at ZT-12. The maximum level in 24 h i.e., acrophases of lipid peroxidation, GPx, SOD and CAT activities in liver cell free extracts altered upon aging. As melatonin, messenger of darkness, an endogenous synchronizer of rhythm, an antioxidant and an antiaging drug, declines with aging we studied the effects of melatonin on activities of these antioxidant enzymes in aging rats. Melatonin administration resulted in differential restoration of acrophases, amplitude, mean as well as daily rhythms of lipid peroxidation and antioxidants in liver of 12 and 24 months old rats.

Circadian rhythms, aging, and life span in mammals

Resetting the circadian clock leads to well being and increased life span, whereas clock disruption is associated with aging and morbidity. Increased longevity and improved health can be achieved by different feeding regimens that reset circadian rhythms and may lead to better synchrony in metabolism and physiology. This review focuses on recent findings concerning the relationships between circadian rhythms, aging attenuation, and life-span extension in mammals.

Melatonin alters age-related changes in transcription factors and kinase activation

Male mice were fed 40 ppm melatonin for 2 months prior to sacrifice at age 26 months, and compared with both 26 and 4 month-old untreated controls. The nuclear translocation of NF-κB increased with age in both brain and spleen and this was reversed by melatonin only in brain. Another transcription factor, AP-1 was increased with age in the spleen and not in brain and this could be blocked by melatonin treatment. The fraction of the active relative to the inactive form of several enabling kinases was compared. The proportion of activated ERK was elevated with age in brain and spleen but this change was unresponsive to melatonin. A similar age-related increase in glial fibrillary acidic protein (GFAP) was also refractory to melatonin treatment. The cerebral melatonin M1 receptor decreased with age in brain but increased in spleen. The potentially beneficial nature of melatonin for the preservation of brain function with aging was suggested by the finding that an age-related decline in cortical synaptophysin levels was prevented by dietary melatonin.