Short and Long Term Regulation of “Leptin” Through Feeding

The substance produced by the adipocytes in our bodies is called leptin. If we have more adipocytes, we can produce more leptin. Hunger, metabolism and behavior. At high leptin levels, animals behave as if they are fully nourished, eat less, become more active, and enhance the activity of the immune system. On the other hand, the level of leptin is low, the animal eats more and becomes more restful.

Figure 4-4 summarizes the overall structure of the system for food level detection and meal opening and closing. Leptin, insulin and blood glucose levels regulate food intake for a short period of time (several hours). Since leptin reflects calories stored in adipocytes, it is also important for long-term weight regulation. Figure 5-4 summarizes how insulin and leptin control the body's energy and food use. Low levels of insulin and leptin indicate that the body is in a negative energy balance (consuming more energy and ingesting it). To counter this situation, these signals suppress unnecessary physical activity, save energy and stimulate the diet. High levels of insulin and leptin indicate that the body is in a positive energy balance (it gains more energy and uses it). In this case, these signals increase physical activity, thereby burning energy and inhibiting feeding.

Adipose tissue plays an important role in regulating food intake over a long period of time. As a person becomes body fat, the release of leptin in adipose tissue increases. Elevated levels of leptin in the blood reach the hypothalamus where the hypothalamus stimulates satiety cells. As the feeling of fullness increases, food intake decreases, resulting in less energy storage and the circle closes

The role of leptin and cholecystokinin in regulating food intake The relationship between leptin and cholecystokinin was investigated under conditions of short term regulation of food intake. Leptin doses were injected intraperitoneally into one experimental group of mice; leptin and cholecystokinin were administered together in the other groups. Leptin alone did not alter food intake during the first 4 hours after injection, while co-injection showed a decrease in food intake during the first 3 hours after injection. Coinjections were reduced by approximately 83% compared to controls. Feed consumption decreased by 62% with cholecystokinin in the first hour, even with intake of 12 microgram per kg leptin. Coinjection of leptin and cholecystokinin does not alter gastric emptying rate but is treated separately (Barrachina et al., 1997)