Scientists have found possible targets for drugs that may help to treat sleep problems and metabolic disorders, including diabetes by discovering a major gear in the biological clock that tells the body when to sleep and metabolize food.
Scientists at the Salk Institute for Biological Studies, led by Ronald M. Evans, a professor in Salk's Gene Expression Laboratory, showed that two cellular switches found on the nucleus of mouse cells, known as REV-ERBα and REV-ERBβ, are essential for maintaining normal sleeping and eating cycles and for metabolism of nutrients from food.
The findings, reported March 29 in Nature
, describe a powerful link between circadian rhythms and metabolism and suggest a new avenue for treating disorders of both systems, including jet lag, sleep disorders, obesity and diabetes.
"This fundamentally changes our knowledge about the workings of the circadian clock and how it orchestrates our sleep-wake cycles, when we eat and even the times our bodies metabolize nutrients," says Evans. "Nuclear receptors can be targeted with drugs, which suggests we might be able to target REV-ERBα and β to treat disorders of sleep and metabolism."
Nurses, emergency personnel and others who work shifts that alter the normal 24-hour cycle of waking and sleeping are at much higher risk for a number of diseases, including metabolic disorders such as diabetes. To address this, scientists are trying to understand precisely how the biological clock works and uncover possible targets for drugs that could adjust the circadian rhythm in people with sleep disorders and circadian-associated metabolic disorders.
In mammals, the circadian timing system is orchestrated by a central clock in the brain and subsidiary clocks in most other organs. The master clock in the brain is set by light and determines the overall diurnal or nocturnal preference of an animal, including sleep-wake cycles and feeding behavior.
Scientists knew that two genes, BMAL1 and CLOCK, worked together at the core of the clock's molecular machinery to activate the network of circadian genes. In this way, BMAL1 acts like the accelerator on a car, activating genes to rev up our physiology each morning so that we are alert, hungry and physically active.
Prior to this work REV-ERBα and β were thought to play only a minor role in these cycles, possibly working together to slow CLOCK-BMAL1 activity to make minor adjustments to keep the clock running on time.
However, genetic studies of two genes with similar functions can be very difficult and thus the real importance of REV-ERBα and β remained mysterious.