When the season becomes darker and colder, the brown fat of animals begins to develop. The fabric generates heat efficiently and quickly and regulates appetite. Brown fat is also present in humans.
In a new study conducted at the Turku PET Center in Finland, researchers observed that shorter daylight hours impact opioid receptor signaling in the brown fat of animals. When the amount of light decreases, levels of opioid receptors increase. The observation was made in rats living in an artificial environment mimicking seasonal changes in daylight.
“In the study, we observed that the number of mu-opioid receptors in brown fat depended on the length of daylight the rat was exposed to. This complements our previous findings that day length modulates opioid receptor levels in emotional brain circuitry in humans. and rats,” says lead researcher Lihua Sun of the Turku PET Center at the University of Turku.
He states that the activity of opioid receptors in brown fat and in the brain are two separate phenomena. However, they share the same goal of helping a mammal, person or animal to adapt both physiologically and emotionally to the changing seasons.
“Opioid receptor levels in the brain and brown fat might be interconnected, for example enhancing each other’s activity, but further research is needed to confirm this,” Sun points out.
New breakthrough in opioid receptor research
Professor Anne Roivainen from the Turku PET Center says this is the first time that mu-opioid receptor levels have been assessed in peripheral regions using positron emission tomography (PET) imaging.
“The finding highlights that mu-opioid receptors affect the seasonality of brown fat activity.
Opioid receptors are parts of the cell through which opioid hormones can impact the cell. An example of these hormones is endorphin, which promotes pleasure and relieves pain in the body.
Therefore, the functions of opioid receptors in the brain play a central role in both pain, mood and emotions. Abnormalities in receptor function have been linked to psychiatric disorders such as depression, anxiety, and eating disorders. Opioid receptor levels may also be important for seasonal affective changes such as seasonal affective disorder. Its symptoms include winter blue and overeating.
Whether seasonal variations in mu-opioid receptor levels in the brain and brown fat underlie seasonal affective changes requires even more scientific evidence, according to Roivainen and Sun.
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Materials provided by University of Turku. Note: Content may be edited for style and length.
