All these activities upset the body’s food clock, a collection of interacting genes and molecules known technically as the food-entrainable oscillator, which keeps the human body on a metabolic even keel. A new study by researchers at the University of California — San Francisco is helping to reveal how this clock works on a molecular level.
Published this month in the journal Proceedings of the National Academy of Sciences, the research team has shown that a protein called PKCγ is critical in resetting the food clock if eating habits change.
The study showed that normal laboratory mice given food only during their regular sleeping hours will adjust their food clock over time and begin to wake up from their slumber, and run around in anticipation of their new mealtime. But mice lacking the PKCγ gene are not able to respond to changes in their meal time. Instead they sleep right through it.
The work has implications for understanding the molecular basis of diabetes, obesity and other metabolic syndromes because a desynchronized food clock may serve as part of the pathology underlying these disorders, said Louis Ptacek, a professor at the university.
It may also help explain why night owls are more likely to be obese than morning larks, Ptacek said.
“Understanding the molecular mechanism of how eating at the wrong time of the day desynchronizes the clocks in our body can facilitate the development of better treatments for disorders associated with night-eating syndrome, shift work and jet lag,” he added.
In most organisms, biological clockworks are governed by a master clock, referred to as the circadian oscillator, which keeps track of time and coordinates our biological processes with the rhythm of a 24-hour cycle of day and night.
Life forms as diverse as humans, mice and mustard greens all possess such master clocks. And in the last decade or so, scientists have uncovered many of their inner workings, uncovering many of the genes whose cycles are tied to the clock and discovering how in mammals it is controlled by a tiny spot in the brain known as the superchiasmatic nucleus.
Scientists also know that in addition to the master clock, human bodies have other clocks operating in parallel throughout the day. One of these is the food clock, which is not tied to one specific spot in the brain but rather multiple sites throughout the body.
The food clock is there to help bodies make the most of the nutritional intake. It controls genes that help in everything from the absorption of nutrients in the digestive tract to their dispersal through the bloodstream, and it is designed to anticipate eating patterns. Even before someone eats a meal, the body begins to turn on some of these genes and turn off others, preparing for the burst of sustenance, which is why pangs of hunger are felt just as the lunch hour arrives.
Scientists have known that the food clock can be reset over time if an organism changes its eating patterns, eating to excess or at odd times, since the timing of the food clock is pegged to feeding during the prime foraging and hunting hours in the day. But until now, very little was known about how the food clock works on a genetic level.
What Ptacek and his colleagues discovered is the molecular basis for this phenomenon: the PKCγ protein binds to another molecule called BMAL and stabilizes it, which shifts the clock in time.