The new study, published in the Journal of Pineal Research, noted that recent research has suggested that melatonin limits obesity in rodents without affecting food intake and activity – something that therefore indicates that the hormone may have a thermogenic effect.
Coupled with previous work that identified brown fat (or beige fat) in white adipose tissue (WAT) “prompted us to investigate whether melatonin is a brown-fat inducer,” explained the research team.
Led by senior author Ahmad Agil from the University of Granada, Spain, the team used a rat model to reveal that melatonin consumption is associated with the induction of beige fat that is known to help regulate body weight control, and offer metabolic benefits.
“We report, for the first time, that oral melatonin supplementation induces browning of the inguinal WAT,” the authors said.
Agil and his colleagues suggested that their results may also offer an insight in to the previously unsolved puzzle of why melatonin consumption has metabolic benefits for people diabetes and hyperlipidaemia.
“We have demonstrated that chronic melatonin treatment in rats behaves as a white fat browning inducer with thermogenic properties. This may be one of the mechanisms that underlies the antiobesity effect of melatonin and thereby explains its metabolic benefits, that is, antidiabetic and lipid-lowering properties,” wrote the researchers.
“Because melatonin treatment does not modify rat physical activity, it is presumed that it can potentiate the thermogenic effect of exercise,” they said – adding that such an observation, coupled with the hormone’s high pharmacological safety profile make melatonin “a potentially useful tool for a stand-alone or adjunct therapy for obesity.”
The team used Zücker diabetic fatty (ZDF) rats - a model of obesity-related type 2 diabetes and a strain in which melatonin reduces obesity and improves their metabolic profiles.
At five weeks of age, ZDF rats and lean littermates (ZL) were subdivided into two groups, each composed of four rats: control and those supplemented with oral melatonin in the drinking water (10 mg/kg/day) for six weeks.
Melatonin supplementation was found to induce the browning of WAT in both ZDF and ZL rats.
The study also showed that chronic administration of melatonin sensitised the thermogenic effect of exposure to cold, heightened the thermogenic effect of exercise. Therefore, the team suggested that melatonin supplementation may be an ‘excellent’ therapy against obesity.
Given the importance of this discovery, Agil said that he is confident the team will obtain the funding needed to continue their work and be able to achieve their final objective: “to confirm these findings in humans, by administering melatonin to help combat obesity and diabetes.”
Source: Journal of Pineal Research
Published online ahead of print, doi: 10.1111/jpi.12089
“Melatonin induces browning of inguinal white adipose tissue in Zucker diabetic fatty rats”
Authors: Aroa Jiménez-Aranda, Gumersindo Fernández-Vázquez, Daniel Campos, et al