Thursday, November 20, 2008

Obesity and Leptin

Obesity, the accumulation of excessive body fat, is a growing worldwide health problem, especially in the United States where it’s considered to be at epidemic levels. Health officials estimate that over one-half of the U.S adult population are overweight (defined as up to 20% over the ideal standard weight based on height and build) and about one-third are obese, clinically defined as having a body weight more than 20% their ideal body weight.

Obesity is a major risk factor for many disease conditions, including diabetes, heart disease, high blood pressure, and stroke, and some kinds of cancers. New biochemical research is showing that obesity is not just a consequence of overeating but is often linked to ,malfunctions in the hormone-controlled systems that regulate energy consumption and body weight.
The direct causes of most obesity cases are not known, but genetic (and perhaps environmental) factors are of central importance. Eightly percent of children of two obese parents become obese, while only 14% of children with normal-weight parents become obese. Genetic studies have discovered that obese mice decrease their food intake, show increased activity, and lose weight when injected with leptin, a fat-tissue-derived, protein hormone. Similar studies using human-derived leptin on obese humans have not been as encouraging as with mice. Unfortunately, leptin’s role in human weight regulation appears to be much more complicated than in mice, so a daily injection of leptin will not be the much sought after “magic bullet” treatment for human obesity. One problem is that humans display a decreased sensitivity to leptin or become “leptin resistant,” a condition that may result from malfunctioning receptors or from a limited number of them. Biochemical research continues to confirm that leptin plays an important, but unknown, role in the pathogenesis of human obesity. Its actions may not be direct, however, but effected through messenger molecules such as neuropeptide Y, a hypothalamic hormone, and other regulatory proteins. Leptin research, though, is gratly broadening our understanding of body weight control and may lead to new drug theraphy for obese patients. On another front, research on muscle mithocondrial uncoupling proteins (UCP), respiratory factors that stimulate heat generation and energy use, may also lead to new drugs for treatment of obesity.


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