| Endocannabinoid System: Why We Keep Eating Editor's Note: This is a fascinating system of positive and negative feedback loops. Much research is being conducted on the understanding and manipulation of the system. I will abstract some of the research since it will impact the future of weight management. Steven Dominguez, MD, MPH Research on brain, fat cell, and other body tissue regulated eating and weight management is evolving. One of the most dynamic concepts which has earned merit in Europe is the Endocannabinoid System (EC). There are two EC receptors (CB1 and CB2). Both are known as our to affect our "feel good" or "comfort" control. This is because CB1 is found in the brain and other tissues and has been researched extensively with marijuana (THC). CB2 is associated with the immune system and has not been as extensively researched. In weight management, we refer to the CB1 receptors. They are the ones in the brain, in adipose tissue, in the liver, and in all of the metabolically important organs. As you see, the CB1 receptors are very important in understanding why we keep eating. Nearly everybody understands that eating is dependent upon signals from the brain to the stomach, and from the stomach to the brain (satiety signal) via the vagus nerve. Soon we will discuss the other organs that also assist in regulating eating behaviors (adiposity signal). The Satiety Signal Simply stated, the satiety signal is a negative feedback signal from the stomach to the brain via the vagus nerve. The EC system interacts with the satiety signals directly through protein peptides released by stomach cells in relation to the amount and type of food consumed. The commonly known peptide are cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide YY (PYY). In addition there is a whole list of peptides secreted from the stomach that act to reduce meal size. That signal gets to the brain via the vagus nerve. However, ghrelin, although it follows the same pattern, actually increases meal size. Endocannabinoids act directly with each one of these signals to DECREASE satiety - that is to make you eat more. The Adiposity System The two most significant adiposity hormones are leptin and insulin. Both of these are released in direct proportion to the body's fat mass. Note that the fat cells are an endocrine gland, releasing a multitude of hormones apart from these two. Leptin and insulin act on the hypothalamus of the brain to either stimulate a Catabolic or Anabolic reaction. Catabolic means that we eat less and spend more energy (lose weight). Anabolic means we eat more and spend less energy (gain weight). The EC receptors are found throughout the neuroendocrine system, and will cause a negative inhibitory response in the hypothalamus to leptin and insulin. This means that instead of losing weight, you will gain weight since you will "feel good" when you eat and the more you eat, the better you feel! As you see from the slide above, the EC system is pervasive and causes these organs to work in synergy resulting in an anabolic effect. This is why "the more you eat, the more you eat." Abstracted from: The Endocannabinoid System: The Mechanisms Behind Metabolic Homeostasis and Imbalance Stephen C. Woods, PhD University of Cincinnati Cincinnati, Ohio |
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