Effect of melatonin on total food intake and macronutrient choice in rats

Effects of dietary melatonin supplementation on growth performance and intestinal health of rice field eel (Monopterus albus)

The objective was to assess the impact of melatonin supplementation on the growth performance and intestinal health of rice field eel, Monopterus albus. Three hundred and sixty fish (28.46 ± 0.24 g) were fed five diets supplemented with melatonin of 0, 30, 60, 120, and 240 mg/kg for 70 days. The study found that the variables FBW, WGR, SGR, and FCR exhibited a statistically significant quadratic relationship (P < 0.05) with the dietary melatonin concentrations, and the highest FBW, WGR and SGR as well as lowest FCR were observed in the 120 mg/kg melatonin group, digestive enzymes activities (such as amylase, trypsin, and lipase) also had significant quadratic relationship (P < 0.05), and the highest intestinal villus height and goblet cells were found in the 120 mg/kg diet (P < 0.01), melatonin in diets significantly increased SOD and CAT activities in serum, up-regulated the expression of anti-inflammatory factors (IL-10) and tight junction protein (ZO-1), and down-regulated the expression of pro-inflammatory factors (IL-1β, IL-8, IL-15, and TNF-α) in the gut, dietary melatonin improved the intestinal microflora compositions, in the group that supplementation a dosage of 120 mg/kg, there was a noticeable rise in the abundance of Firmicutes and the ratio of Firmicutes/Bacteroidota, compared with control group (P < 0.1). Conclusively, dietary supplementation of melatonin promoted growth performance, enhanced intestinal immune capacity and serum antioxidant level, and improved intestinal morphology properties and intestinal flora composition in M. albus. In conclusion, based on quadratic broken-line regression analysis of WGR and FCR, the optimal concentration of melatonin to be supplied is predicted to be 146-148 mg/kg.

Effects of exogenous melatonin on body mass and thermogenesis in red-backed vole (Eothenomys miletus) between Kunming and Dali regions

Melatonin (MEL) is an indole hormone synthesized and secreted by the pineal gland at night, which is involved in the regulation of body mass and thermogenesis in small mammals. To test the effects of exogenous MEL on body mass and thermogenic ability in two different red-backed vole (Eothenomys miletus) populations from two different regions (Kunming [KM] and Dali [DL]) with different annual variation in climatic variables, such as temperature, sunshine and rainfall. we traced the changes of energy balance in E. miletus from KM and DL, which were placed at 25 ± 1°C with photoperiod of 12 L:12 D, intraperitoneal injection of MEL was performed daily for 28 days. The results showed that body mass and food intake were significantly decreased, while resting metabolic rate (RMR) and nonshivering thermogenesis (NST) were significantly increased after MEL injection; Contents of total protein, mitochondrial protein, the activities of cytochrome C oxidase (COX) and α-glycerophosphate oxidase (α-PGO) in liver and brown adipose tissue (BAT) were enhanced; the activity of thyroxin 5'-deiodinase (T₄ 5'-DII) and uncoupling protein 1 (UCP1) in BAT were also increased. Serum leptin, triiodothyronine (T₃ ) levels and T₃ /T₄ ratio were significantly increased, thyroxine (T₄ ) levels was significantly decreased. Moreover, body mass and food intake in E. miletus from KM were higher than those from DL, but RMR and NST were lower than those from DL. Changes of body mass, food intake and thermogenic activity of KM were higher than those of DL when exposed to injection of MEL, indicating that E. miletus in KM were more sensitive to MEL. Furthermore, MEL was involved in the regulation of body mass and thermogenesis in E. miletus between KM and DL.

Suppression of obesity by melatonin through increasing energy expenditure and accelerating lipolysis in mice fed a high-fat diet

Backgrounds/objectives

Melatonin promotes brown adipose tissue (BAT) activity, leading to body mass reduction and energy expenditure. However, the mechanisms governing these beneficial effects are not well-established. This study aimed to assess the effects of (1) melatonin on BAT and energy metabolism, and (2) fibroblast growth factor 21 (FGF21) in BAT-mediated thermogenesis.

Methods

Male C57BL/6 J mice received a high-fat diet (HFD) or normal chow, accompanied by intraperitoneal injection of 20 mg/kg melatonin for 12 weeks. FGF21^−/− mice consumed an HFD with or without melatonin for 8 weeks.

Results

Melatonin attenuated weight gain, insulin resistance, adipocyte hypertrophy, inflammation, and hepatic steatosis induced by the HFD and increased energy expenditure. Furthermore, melatonin improved cold tolerance by increasing BAT uncoupling protein 1 (UCP1) expression and producing heat. Notably, melatonin resulted in a shift in energy metabolism favouring the utilization of fat, and it increased FGF21 in circulating and metabolic tissues and skeletal muscle phosphorylation of AMP-activated protein kinase. However, melatonin did not protect against obesity, insulin resistance, and energy expenditure in HFD-fed FGF21^−/− mice.

Conclusions

Melatonin suppressed obesity and insulin resistance resulting from the HFD by enhancing BAT activity and energy expenditure, and these effects were dependent on FGF21.

Effects of Melatonin and Propolis Supplementation on Inflammation, Oxidative Stress, and Clinical Outcomes in Patients with Primary Pneumosepsis: A Randomized Controlled Clinical Trial

Background & Objective: The present study aimed to investigate the effects of propolis and melatonin supplementation on inflammation, clinical outcomes, and oxidative stress markers in patients with primary pneumosepsis. Materials and Methods: This pilot randomized controlled trial was conducted on 55 patients with primary pneumosepsis who were randomly assigned to the intervention and control groups. In the three intervention groups, the patients received propolis alone (1,000 mg/day), propolis (1,000 mg/day) plus melatonin (20 mg/day), and melatonin alone (20 mg/day). The control group received placebo. The inflammatory and oxidative stress markers as well as clinical outcomes were evaluated before and after the intervention, and the 28-day survival rate was also recorded. Results: After the intervention, the combination of propolis and melatonin significantly reduced interleukin-6 (-55.282 pg/ml ) and C-reactive protein (-21.656 mg/l ) levels, while increasing gavage intake (326.680 ml/day ) and improving some clinical outcomes (APACHE II, SOFA and NUTRIC scores) compared to control group. However, no significant difference was observed between the groups in terms of oxidative stress and hematological indices. In addition, the 28-day survival rate had no significant difference between the groups (P=0.07). Conclusion: Supplementation with propolis and melatonin may improve clinical outcomes by reducing inflammation. Further investigations are required to confirm these findings.

Functional Molecules of Intestinal Mucosal Products and Peptones in Animal Nutrition and Health

There is growing interest in the use of intestinal mucosal products and peptones (partial protein hydrolysates) to enhance the food intake, growth, development, and health of animals. The mucosa of the small intestine consists of the epithelium, the lamina propria, and the muscularis mucosa. The diverse population of cells (epithelial, immune, endocrine, neuronal, vascular, and elastic cells) in the intestinal mucosa contains not only high-quality food protein (e.g., collagen) but also a wide array of low-, medium-, and high-molecular-weight functional molecules with enormous nutritional, physiological, and immunological importance. Available evidence shows that intestinal mucosal products and peptones provide functional substances, including growth factors, enzymes, hormones, large peptides, small peptides, antimicrobials, cytokines, bioamines, regulators of nutrient metabolism, unique amino acids (e.g., taurine and 4-hydroxyproline), and other bioactive substances (e.g., creatine and glutathione). Therefore, dietary supplementation with intestinal mucosal products and peptones can cost-effectively improve feed intake, immunity, health (the intestine and the whole body), well-being, wound healing, growth performance, and feed efficiency in livestock, poultry, fish, and crustaceans. In feeding practices, an inclusion level of an intestinal mucosal product or a mucosal peptone product at up to 5% (as-fed basis) is appropriate in the diets of these animals, as well as companion and zoo animals.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Altered metabolic and hormonal responses in male rats exposed to acute bright light-at-night associated with global DNA hypo-methylation

The association between light pollution and disruption of daily rhythms, metabolic and hormonal disorders, as well as cancer progression is well-recognized. These adverse effects could be due to nocturnal melatonin suppression. The signaling pathway by which light pollution affects metabolism and endocrine responses is unclear. We studied the effects of artificial light at night (ALAN¹) on body mass, food and water intake, daily rhythms of body temperature, serum glucose and insulin in male rats. Daily rhythms of urine production and urinary 6-sulfatoxymelatonin (6-SMT²), as well as global DNA methylation in pancreas and liver tissues were also assessed. Mass gain was higher in ALAN rats compared with controls. Food intake, water consumption, glucose, insulin, and 6-SMT levels markedly lessened in response to ALAN. Conversely, urine production and body temperature were elevated in ALAN rats compared with controls. Significant 24-h rhythms were detected for all variables that were altered in mesor, amplitude, and acrophase occurrences under ALAN conditions. DNA hypo-methylation was detected in ALAN pancreatic tissue compared with controls, but not in hepatic tissue. Overall, ALAN affects metabolic and hormonal physiology in different levels in which flexible crosstalk between melatonin and both epigenetics and metabolic levels expressed as body temperature rhythm, is suggested to mediate the environmental exposure at the molecular level and subsequently physiology is altered. The flexibility of epigenetic modifications provides a potential therapeutic target for rectifying ALAN adverse effects by epigenetic markers such as melatonin and behavioral lifestyle interventions for confining ALAN exposures as much as possible.

Artificial light at night alters behavior in laboratory and wild animals

Life has evolved to internalize and depend upon the daily and seasonal light cycles to synchronize physiology and behavior with environmental conditions. The nightscape has been vastly changed in response to the use of artificial lighting. Wildlife is now often exposed to direct lighting via streetlights or indirect lighting via sky glow at night. Because many activities rely on daily and seasonal light cues, the effects of artificial light at night could be extensive, but remain largely unknown. Laboratory studies suggest exposure to light at night can alter typical timing of daily locomotor activity and shift the timing of foraging/food intake to the daytime in nocturnal rodents. Additionally, nocturnal rodents decrease anxiety-like behaviors (i.e., spend more time in the open and increase rearing up) in response to even dim light at night. These are all likely maladaptive responses in the wild. Photoperiodic animals rely on seasonal changes in day length as a cue to evoke physiological and behavioral modifications to anticipate favorable and unfavorable conditions for survival and reproduction. Light at night can mask detection of short days, inappropriately signal long days, and thus desynchronize seasonal reproductive activities. We review laboratory and the sparse field studies that address the effects of exposure to artificial light at night to propose that exposure to light at night disrupts circadian and seasonal behavior in wildlife, which potentially decreases individual fitness and modifies ecosystems.

Long-term exogenous melatonin treatment modulates overall feed efficiency and protects ovarian tissue against injuries caused by ethanol-induced oxidative stress in adult UChB rats

BACKGROUND

Chronic ethanol intake leads to reproductive damage including reactive oxygen species formation, which accelerates the oxidative process. Melatonin is known to regulate the reproductive cycle, food/liquid intake, and it may also act as a potent antioxidant indoleamine. The aim of this study was to verify the effects of alcoholism and melatonin treatment on overall feed efficiency and to analyze its protective role against the oxidative stress in the ovarian tissue of UChB rats (submitted to 10% [v/v] voluntary ethanol consumption).

METHODS

Forty adult female rats (n = 10/group) were finally selected for this study: UChB Co: drinking water only; and UChB EtOH: drinking ethanol at 2 to 6 ml/100 g/d + water, both receiving 0.9% NaCl + 95% ethanol 0.04 ml as vehicle. Concomitantly, UChB Co + M and UChB EtOH + M groups were infused with vehicle + melatonin (100 μg/100 g body weight/d) intraperitoneally over 60 days. All animals were euthanized by decapitation during the morning estrus (4 am).

RESULTS

Body weight gain was reduced with ethanol plus melatonin after 40 days of treatment. In both melatonin-treated groups, it was observed a reduction in food-derived calories and liquid intake toward the end of treatment. The amount of consumed ethanol dropped during the treatment. Estrous cycle was longer in rats that received both ethanol and melatonin, with prolonged diestrus. Following to oxidative status, lipid hydroperoxide levels were higher in the ovaries of ethanol-preferring rats and decreased after melatonin treatment. Additionally, antioxidant activities of superoxide dismutase, glutathione peroxidase activity, and glutathione reductase activity were increased in melatonin-treated groups.

CONCLUSIONS

We suggest that melatonin is able to affect feed efficiency and, conversely, it protects the ovaries against the oxidative stress arising from ethanol consumption.

Keeping track of time under ice and snow in a sub-arctic lake: plasma melatonin rhythms in Arctic charr overwintering under natural conditions

Although photoperiod is considered as a major environmental cue for timing of seasonal events in fish, little is known about the photic information perceived by fish in different aquatic environments. The strongly seasonal Arctic charr, Salvelinus alpinus, reside in lakes covered by thick ice and snow throughout the dark winter in the north. In the present study, we have measured diel changes in their plasma melatonin concentrations from September to June in Lake Storvatnet (70 degrees N), northern Norway. In addition, we have measured the in vitro melatonin production of Arctic charr pineal glands held at experimental light conditions. From September to April a diel profile in plasma melatonin was seen in the charr in Lake Storvatn, with highest concentrations at night. This profile reflected the prevailing above-surface photoperiod, even in February when there were minimal changes in sub-surface irradiance between day and night. In June, plasma melatonin was low throughout the 24-hr cycle, despite there being a marked sub-surface difference in irradiance between night and day. At this time the irradiance in night probably remained above the threshold for suppression of melatonin production. The in vitro experiments revealed no endogenous rhythm in the pineal melatonin secretion, supporting the conclusion that the diel profile seen in the Arctic charr in their natural habitat was driven by ambient photoperiod. In conclusion, the Arctic charr appear to keep track of time even under the extreme conditions of high latitudes during winter, when lakes have thick ice and snow cover.

Melatonin effects on food intake and activity rhythms in two fish species with different activity patterns: Diurnal (goldfish) and nocturnal (tench)

Melatonin has several known physiological functions, the main one being synchronization of daily and seasonal rhythms. In addition, melatonin has been reported to influence food intake and behavioral rhythms with varying results depending on the species. The aim of this research was to evaluate the effects of intraperitoneal melatonin injection on food intake and locomotor activity in two different fish species: goldfish (diurnal) and tench (nocturnal), under different light regimes: constant light (LL) conditions or LD 12:12, with melatonin administration at mid-light (ML), mid-dark (MD), and after a 1-h light pulse at MD. In addition to these acute tests, in the case of goldfish we also investigated the effects of daily melatonin administration for 1 week. Our results indicated that acute melatonin administration significantly decreased goldfish food intake (16-52% inhibition, depending on the light regime) and locomotor activity (55-100%), with the chronic treatment inducing a similar total food intake inhibition that persisted for 7 days. In tench, a nocturnal fish species, acute melatonin administration at MD and ML reduced food intake (37% and 29%, respectively), while locomotor activity was not affected at MD and slightly increased at ML. Taken together, these results indicated that melatonin reduced food intake in both species, while its effects on locomotor activity depended on the time of administration (light or dark phase) and the activity patterns of the species.