Leptin is a human hormone that plays significant roles in appetite and weight control, metabolism and reproduction. At the same time, leptin is associated with a host of disease states. This hormone is produced by fat cells throughout the body and also by cells that line the stomach. People who do not produce enough leptin, and those who produce the hormone but are resistant to it, overeat and become obese, according to researchers at Rockefeller University. Ongoing research confirms that leptin also plays a key role in the development of some inflammatory conditions and other chronic disease states.
History
In 1994, researcher Jeffrey Friedman and colleagues at Rockefeller University in New York discovered both leptin and the gene that encodes this hormone, which they named "obese," and which is generally referred to as the ob gene. Working with laboratory animals, these researchers found that mice with defective ob genes were up to three times heavier than mice with normal genes. When injected with synthetic leptin, the obese mice became more active and lost weight.
Function
Leptin works in the brain, with other brain chemicals, to promote normal eating and prevent overeating. Leptin replacement therapy in humans with leptin deficiency or resistance results in weight loss and better control of insulin resistance and triglycerides, or blood fat, levels. Leptin also plays a role in bone formation, immunity and angiogenesis, or the normal growth of new blood vessels.
Deficiency
A complete absence of leptin is rare, and many obese people have normal levels of leptin circulating in their blood. Some obese people are resistant to the appetite-regulating effects of leptin, which may explain why it is so difficult for some people to resist overeating, according to researchers at the University of Michigan Medical School.
Chronic Disease
Leptin's role in malignant tumor growth and other areas of health, such as immunity and inflammation, is recognized, but not well understood, according to research performed at the Sbarro Institute for Cancer Research and Molecular Medicine in Philadelphia and the Santiago University Clinical Hospital Research Laboratory in Spain. The Spanish researchers found that leptin is associated with the development of inflammatory conditions such as type 1 diabetes, bowel inflammation, rheumatoid arthritis and osteoarthritis. Research published in a 2008 issue of "Nature Reviews Cardiology" also found that high levels of leptin are associated with higher risk of developing cardiovascular disease.
References
- The Rockefeller University: Leptin
- "Cell Research": Leptin--A Multifunctional Hormone
- "Brain Pathology": Leptin and Its Receptor are Overexpressed in Brain Tumors and Correlate with the Degree of Malignancy
- "Cellular and Molecular Life Sciences": Leptin Receptor Action and Mechanisms of Leptin Resistance
- "Nature Reviews Cardiology": Relationships Between Leptin and C-Reactive Protein with Cardiovascular Disease in the Adult General Population
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