Leptin is a hormone that is produced by fat cells and involved in regulating body weight. The function of this hormone is to interact with certain areas of the brain that are involved in controlling hunger. The hypothalamus and brain stem are responsible for sending signals to the body to let it know when to stop eating. There is a small percentage of people who have a genetic mutation in their leptin gene which leads to over-eating and eventually obesity. This genetic mutation is classified as hyperleptinemia. Hyperleptinemia is a condition where there is an increase of leptin in the bloodstream. When the leptin levels are high in the body then it can lead to the development of leptin resistance. Leptin resistance is a result of increased leptin which causes fat cells to increase as well. Due to leptin resistance, the brain cannot recognize when fat cells are dramatically increasing so the body is not signaled when to stop eating which leads to obesity. The physiological causes behind the development of leptin resistance is not fully understood by most people.
Researchers have conducted an experiment involving mice to determine whether the increase of leptin in the bloodstream leads to the development of leptin resistance. The mice used in this experiment were ob/ob and wild-type. This experiment discussed the effects of how a high- fat diet impairs the sensitivity of leptin to the neurons in the hypothalamus. There was two models that were developed from this experiment. One model proposed that leptin resistance is caused by increased plasma leptin levels which leads to overstimulation of leptin receptors and activation of negative feedback loops. The second model proposed that the dietary fats are directly responsible for the development of leptin resistance. The results from the experiment showed that as the mice were fed a high- fat diet they gained significant weight over a short period of time and their ability to limit their food intake was reduced. This confirmed that the diet- induced mice were resistant to leptin even when it was injected directly into their brain. The data from the results supported that hyperleptinemia and excess leptin signaling is required in order for leptin resistance to develop.
I think that it is important to understand the effects of leptin deficiency and leptin resistance in humans and mice, and how obesity is a resulting factor. Additionally, this experiment provided valuable information that can help people that suffer from hyperleptinemia understand how it is developed. Lastly, the findings from this experiment can be used to potentially prevent this genetic mutation from occurring.