Diabetes and Circadian Rhythm Linked By Researchers

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A new cause of diabetes may have been identified by researchers at UT Southwestern Medical Center. Dr. Joseph Takahashi, investigator with the Howard Hughes Medical Institute at UT Southwestern, with researchers at Northwestern University, University of Chicago, University of Wisconsin, Madison; Washington University School of Medicine, St. Louis; and GeneGo Inc. authored a study published in the journal, Nature, that found two genes, CLOCK and BMAL1, when disrupted can lead to diabetes. CLOCK and BMAL1 help control the body’s internal clock system, the circadian rhythm.

About 23.6 million people in the United States—7.8 percent of the population—have diabetes today. There are three main types of diabetes. Basically, diabetes is a disease where the body either produces too much insulin or not enough causing a wide range of symptoms. For more information, please visit here. Circadian rhythms are responsible for cyclical patterns such as sleeping, eating, body temperature, and hormone production.

In this particular study, mice with defective CLOCK and BMAL1 genes were found to be unable to produce sufficient amounts of insulin. Dr. Takahashi discovered the CLOCK gene in 1997. This gene sets up the protein called a transcription factor, which helps decide what other genes will become active. BMAL1 also does this and works with the CLOCK gene.

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The study confirmed that each organ has its own circadian rhythm and that even lacking CLOCK cells would produce appropriate amounts of insulin but that they would be released to the body. Glucose, the body’s main source for energy, is affected by insulin. Researchers found that mice who had lacked the BMAL1 gene only in their pancreases did not become obese but did have abnormally high blood sugar whereas mice without the CLOCK cells were also prone to obesity, metabolic syndrome and liver dysfunction.

Dr. Takahashi says, “This finding indicates that disruption of clock genes only in the pancreas, and not the rest of the body clock, can produce early signs of diabetes.” This will help researchers understand more about the cause of diabetes.

The study was funded by the National Institutes of Health (NIH), the Chicago Biomedical Consortium Searle Funds and the Juvenile Diabetes Research Foundation.

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