The liver normally makes and stores fat, which is required in moderation for normal body function. However, if the process goes awry, excess fat in the liver can cause major liver damage.  In fact, fatty liver is a leading cause of liver failure in the United States, and is often brought on by obesity and diabetes. In turn, the increasing prevalence of these diseases has brought with it an epidemic of liver disease.

Abnormal sleep patterns, such as those of shift-workers, can be risk factors for obesity and diabetes. Investigators have known for decades that fat production by the liver runs on a 24-hour cycle, the circadian rhythm, and is similar to the sleep-wake cycle.  A research team led by Mitchell Lazar, MD, PhD, director of the Institute for Diabetes, Obesity, and Metabolism at the University of Pennsylvania School of Medicine, has discovered molecules that act as “shift workers” to maintain the daily rhythm of fat metabolism. When those molecules do not do their jobs, the liver dramatically fills with fat. These findings are reported in this week’s issue of Science.

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