Leptin: How Diabetes and Obesity Are Linked

One of the more popular articles on my Web site is a transcript of a lecture about the importance of insulin by Dr. Ron Rosedale, one of world's foremost experts on leptin, a very powerful and influential hormone that has totally changed the way science looks at fat, nutrition and metabolism. Leptin's appetite-controlling role leads to obesity, which significantly raises the risk of diabetes.

Researchers at the University of Michigan and Harvard University found new evidence in mice that may explain the link between obesity and type 2 diabetes and help them understand why some obese people never develop diabetes while many others do. Leptin is the key, because it regulates blood sugar through two different brain-body pathways: One controlling appetite and fat storage and another that tells the liver what to do with its glucose reserves.

The study found it may take disruptions to both pathways to bring on full-blown diabetes and overwhelm the body's ability to control blood glucose levels via the action of insulin.

Scientists discovered the link while observing mice that were genetically modified so the leptin-STAT3 cell-signaling pathway that leads from the brain to the body was disabled. This s/s strain of mice could still produce both leptin and the receptor it binds to when sending STAT3 signals to the body. Even though the s/s mice ate too much and became obese, they did not develop diabetes even after six months, a long time for a mouse. However, other strains of mice that made no leptin, or had no receptors, all became obese and died of diabetes.

Although researchers warned the blood sugar of the genetically modified strain of mice was high, their bodies had far more control than other mice that didn't produce leptin. And when the mice were placed on calorie-restricted diets, their blood sugar levels were normalized.

Cell Metabolism Vol 1, 169-178, March 2005 free full text article

EurekAlert March 16, 2005

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