image: Positron emission tomography/computed tomography (PET/CT) detects mu-opioid receptors in brown fat and rat brain. see more
Credit: Photographer/Author Lihua Sun / Vecteezy.com
As the season gets darker and colder, the animals’ brown fat begins to grow. The fabric produces heat efficiently and quickly, and regulates appetite. Brown fat is also present in people.
In a new study conducted at the Turku PET Centre, Finland, researchers observed that shorter daylight hours affect opioid receptor signaling in the animals’ brown fat. When the amount of light decreases, the 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 levels of opioid receptors in the emotional circuits of the brain in humans and rats,” says senior researcher Lihua Sun of the Turku PET Center at the University of Turku.
It states that opioid receptor activity in brown fat and 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 change of season.
“The levels of opioid receptors in the brain and brown fat could be interconnected, for example, reinforcing each other’s activity, but more research is needed to confirm this,” Sun emphasizes.
New breakthrough in opioid receptor research
Professor Anne Roivainen from Turku PET Center explains that this is the first time mu opioid receptor levels in peripheral regions have been assessed using positron emission tomography (PET).
“The finding highlights that mu-opioid receptors affect the seasonality of brown fat activity. Future studies should further investigate whether mu-opioid receptors in brown fat are directly related to energy consumption of the fabrics,” says Roivainen.
Opioid receptors are parts of the cell through which opioid hormones can affect the cell. An example of these hormones is endorphin, which promotes pleasure and relieves pain in the body.
Consequently, the functions of opioid receptors in the brain play a central role in both pain and mood and emotions. Abnormalities of receptor function have been linked to psychiatric disorders such as depression and anxiety and eating disorders. Opioid receptor levels may also be important for seasonal affective changes, such as seasonal affective disorder. Its symptoms include winter blues and overeating.
According to Roivainen and Sun, whether seasonal variations in mu-opioid receptor levels in brain and brown fat underlie seasonal affective changes still requires more scientific evidence.
The research results have been published in the European Journal of Nuclear Medicine and Molecular Imaging.
magazine
European Journal of Nuclear Medicine and Molecular Imaging
Title of the article
[11C]PET imaging of carfentanil to study the peripheral opioid system in vivo: effect of photoperiod on mu-opioid receptor availability in brown adipose tissue
Publication date of the article
27-Sep-2022
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