Bombesin is an amino acid found in the digestive system. It is a peptide with a chain of 14 amino acids. Although it is not fully understood, it is known to play an important role in the release of gastrin, the activation of G-protein receptors in the brain and the initiation of the negative feedback loop that stops eating. It also can be an indicator of developing tumors related to certain types of cancers. This complex amino acid is located in the nerves of the gastrointestinal tract.
With a key role in digestion, bombesin stimulates the release of the hormone gastrin. Gastrin subsequently causes the release of gastric acid from the stomach walls. This helps to break down food in the stomach and assists in moving food particles along the digestive tract by controlling the contraction of smooth muscles. Gastrin is released from G-cells, which are enterendocrine cells in the stomach walls and glands.
Bombesin acts in the stomach to suppress the appetite. This amino acid peptide was originally discovered in the skin of frogs that use the action of bombesin to their advantage. By interfering with the metabolic processes of the body, the peptide leads to a buildup of waste products in the frog's glands that can be released as a defense mechanism when the frog is threatened. It is hypothesized that the feeling of fear in humans might also be related to bombesin.
The manner in which food is digested in the body and how this relates to the sensation of hunger is an extremely complicated process. Receptors in the brain respond to signals from the digestive tract, and bombesin is one of two chemicals that initiate a negative feedback loop that controls eating behavior. Along with cholecystokinin, bombesin responds to food in the stomach and stimulates the brain to release a satiety signal. The loop works via negative feedback because the fuller the stomach, the greater the signal to prevent further eating.
An increase in the activity of bombesin receptors can be indicative of a number of different types of cancer. These include small cell carcinomas in the lungs as well as ovarian and breast cancers. Other types of cancers that might be indicated are pancreatic, prostate, nervous system, thyroid and colorectal cancers. Research into peptide markers and tumor growth was in its infancy as of 2011, but some scientists believed that research into this peptide's relationship to cancer cells might be valuable in discovering a cure for the disease.
