Summary: Some people experience greater pleasure by eating food than others. Thus, these individuals are more likely to consume excess calories. Dopamine pathways are known to be associated with addiction and the consolidation of memories. However, studies show that food addiction is more complex with the involvement of various other pathways. The new studies show that two overlapping mechanisms that are opioid and endocannabinoid systems, play a vital role in food addiction. PET scan of the brain confirms lower expression of MOR receptors in those consuming excessive food. However, it appears that the effect of the endocannabinoid system on appetite is more varied. Thus, researchers propose that targeting the opioid system could be one of the ways of managing eating disorders.
Excessive energy intake leads to obesity. However, eating disorders also increase the risk of numerous other disorders. It appears that obesity and related disorders have lots to do with how people control their urge to eat food. Obese individuals often consume more calories. They have a greater hunger due to hormones and certain peculiarities of the central nervous system.
Dopamine pathways are long known to play a central role in addiction, pleasure-seeking behavior. Thus, researchers think that dopamine also plays a role in food addiction. Overconsumption of food leads to a greater dopamine response. Dopamine also has a role in the consolidation of these memories. Thus, people living with eating disorders are more likely to be tempted to increase their dopamine by consuming more food1.
A new study confirms the role of opioid and endocannabinoid systems in eating disorders, too
Figure 1 Activity of opioid system in various brain centers associated with eating disorders
It seems that targeting dopamine may help, but not in all cases. Thus, it became evident that there must be other pathways involved in an eating disorder, too. Therefore, researchers started paying attention to two of the overlapping systems that are opioid and endocannabinoid systems.
Early studies and experiences with cannabinoids show that they may influence appetite in a complex manner. For example, cannabis extracts are known to be potent appetite modifiers, with some cannabinoids stimulating the appetite, while others rather suppressing2.
Similarly, researchers have noticed abnormalities in the levels of endogenous opioids like endorphins in those with eating disorders. Again, these changes are similar to those found in people addicted to various substances3. Further, like cannabinoids, experience shows that opioid use can also modulate appetite and alter eating behavior.
With the advances in imaging technologies, it is now possible to visualize the activity of various pathways in the brains of individuals. Thus, in the new study, researchers analyzed the activity of μ-opioid receptors (MOR) and cannabinoid CB1 receptors (CB1) in various brain centers in healthy subjects. At the same time, they analyzed their eating habits with the help of the Dutch Eating Behavior Questionnaire (DEBQ). This study was done by researchers at the University of Turku in Finland4.
For analyzing the activity of MOR receptors in different brain centers, researchers used carfentanil PET scans from 92 healthy subjects. And for understanding the activity of CB1 receptors, they used FMPEP-d2 scans from 35 adults.
The study demonstrated that individuals with low expression of MOR receptors were more likely to consume more calories. On the other hand, changes in CB1 receptors were associated with more varied eating disorders.
Thus, the study confirmed that both the opioid and endocannabinoid pathways have a vital role in regulating eating habits. In addition, these pathways play a crucial role in food reward pathways. Moreover, the study could also demonstrate a considerable overlap between the two pathways. Nevertheless, the role of these two pathways is distinct in controlling eating behaviors.
Therefore, the study shows that one of the novel ways of managing eating disorders could be targeting the opioid receptors in the brain. Although, researchers remain less clear about targeting CB1 receptors for managing eating disorders.
This insight also underscores the complexity of the brain’s reward system, which is similarly implicated in opioid addiction treatment, where managing cravings and dependencies often involves targeting these receptors to help restore balance in the brain’s chemistry.
References
1. Botticelli L, Micioni Di Bonaventura E, Del Bello F, et al. Underlying Susceptibility to Eating Disorders and Drug Abuse: Genetic and Pharmacological Aspects of Dopamine D4 Receptors. Nutrients. 2020;12(8):2288. doi:10.3390/nu12082288
2. Marco EM, Romero-Zerbo SY, Viveros MP, Bermudez-Silva FJ. The role of the endocannabinoid system in eating disorders: pharmacological implications. Behavioural Pharmacology. 2012;23(5 and 6):526-536. doi:10.1097/FBP.0b013e328356c3c9
3. Lienard Y, Vamecq J. [The auto-addictive hypothesis of pathological eating disorders]. Presse Med. 2004;33(18 Suppl):33-40. doi:10.1016/s0755-4982(04)72380-5
4. Kantonen T, Karjalainen T, Pekkarinen L, et al. Cerebral μ-opioid and CB1 receptor systems have distinct roles in human feeding behavior. Transl Psychiatry. 2021;11(1):1-9. doi:10.1038/s41398-021-01559-5
