How Excess Holiday
Eating Disturbs Your 'Food Clock'
If
the sinful excess of holiday eating sends your system into butter-slathered,
brandy-soaked overload, you are not alone: People who are jet-lagged, people
who work graveyard shifts and plain-old late-night snackers know just how you
feel.
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 (UCSF) is helping to
reveal how this clock works on a molecular level.
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 sleeping 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,
MD, the John C. Coleman Distinguished Professor of Neurology at UCSF and a
Howard Hughes Medical Institute Investigator.
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.
Resetting the Food Clock
Look
behind the face of a mechanical clock and you will see a dizzying array of
cogs, flywheels, reciprocating counterbalances and other moving parts.
Biological clocks are equally complex, composed of multiple interacting genes
that turn on or off in an orchestrated way to keep time during the day.
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, our 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 our bodies make the most of our nutritional intake.
It controls genes that help in everything from the absorption of nutrients in
our digestive tract to their dispersal through the bloodstream, and it is
designed to anticipate our eating patterns. Even before we eat a meal, our
bodies begin to turn on some of these genes and turn off others, preparing for
the burst of sustenance -- which is why we feel the pangs of hunger just as the
lunch hour arrives.
Scientist
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.
The
article, "PKCγ participates in food entrainment by regulating BMAL1"
is authored by Luoying Zhang, Diya Abrahama, Shu-Ting Lin, Henrik Oster, Gregor
Eichele, Ying-Hui Fu, and Louis J. Ptácek and appears in the Proceedings of the
National Academy of Sciences.
In
addition to UCSF, authors on the study are affiliated with the Max Planck
Institute of Biophysical Chemistry in Göttingen, Germany.
This
work was supported by the National Institutes of Health via grants #GM079180
and #708 HL059596, the Sandler Neurogenetics Fund, and the Howard Hughes
Medical Institute.
Story Source:
The
above story is reprinted from materials provided
by University
of California, San Francisco (UCSF). The original article was
written by Jason Bardi.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
1. L. Zhang, D. Abraham, S.-T. Lin, H. Oster, G.
Eichele, Y.-H. Fu, L. J. Ptacek. PKC participates in food
entrainment by regulating BMAL1. Proceedings of the National
Academy of Sciences, 2012; 109 (50): 20679 DOI:10.1073/pnas.1218699110
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University of California, San Francisco (UCSF) (2012, December
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