A new study finds that limiting flies to specific
eating hours protected their hearts against aging.
If you’re looking to improve your heart health by
changing your diet, when you eat may be just as
important as what you eat.
In a new study published in Science, researchers at
San Diego State University and the Salk Institute
for Biological Studies found that by limiting the
time span during which fruit flies could eat, they
could prevent aging- and diet-related heart problems.
The researchers also discovered that genes
responsible for the body's circadian rhythm are
integral to this process, but they're not yet sure
how.
Previous research has
found that people who tend to eat later in the day
and into the night have a higher chance of
developing heart disease than people who cut off
their food consumption earlier.
Girish Melkani, Ph.D., a
biologist at SDSU whose research focuses on
cardiovascular physiology, one of the paper’s senior
authors, teamed up with Satchidananda Panda, Ph.D.,
a circadian rhythms expert at the Salk Institute, to
address whether changing the daily eating patterns
of fruit flies could affect their heart health.
Fruit flies have long been used as model organisms
to identify the genetic basis of human disease,
including cardiovascular disease. Shubhroz Gill,
Ph.D., a postdoctoral researcher in Panda’s lab and
now at the Broad Institute in Boston, was the lead
author on this study. Hiep D. Le of the Salk
Institute also contributed to the study.
In their experiments,
one group of 2-week-old fruit flies was given a
standard diet of cornmeal and allowed to feed all
day long. Another group was allowed access to the
food for only 12 hours a day. Over the course of
several weeks, Melkani and Gill recorded how much
food the flies were eating and tested a battery of
health measures related to their sleep, body weight
and heart physiology.
After three weeks, the
results were clear: Flies on the 12-hour
time-restricted feeding schedule slept better, didn’t
gain as much weight and had far healthier hearts
than their “eat anytime” counterparts, even though
they ate similar amounts of food. The researchers
observed the same results after five weeks.
“In very early
experiments, when we compared 5-week-old flies that
were fed for either 24 hours or 12 hours, the hearts
of the latter were in such good shape that we
thought perhaps we had mistaken some young
3-week-old fruit flies for the older group,” Gill
said. “We had to repeat the experiments several
times to become convinced that this improvement was
truly due to the time-restricted feeding.”
What’s more, another set
of experiments revealed that the benefits of a
time-restricted diet weren’t exclusive to young
flies. When the researchers introduced these dietary
time restrictions to older flies, their hearts
became healthier, too. (The average lifespan of a
fruit fly is about 60 days.).
Even if you introduce time-restricted feeding very
late, you still have some benefit,” Melkani said.
Some degree of heart protection persisted even for
flies that went back to eating whenever they wanted,
he added.
Next, the researchers
sequenced the RNA of the flies at various points in
the experiment to find which of their genes had
changed as a result of time-restricted feeding. They
identified three genetic pathways that appear to be
involved: the TCP-1 ring complex chaperonin, which
helps proteins fold; mitochondrial electron
transport chain complexes (mETC); and a suite of
genes responsible for the body’s circadian rhythm.
Melkani and Gill
repeated their experiments using mutant strains of
flies with nonfunctional versions of the TCP-1 and
circadian rhythm genes. In these flies,
time-restricted feeding granted no health benefits,
strengthening the case that these genetic pathways
play key roles.
Conversely, in mutant
flies with altered mETC genes, the flies showed
increased protection against cardiac aging.
“If and how these three pathways all work together,
we don’t yet know entirely,” Melkani said.
Earlier research from
Panda’s lab has shown there are benefits of
time-restricted feeding on other metabolic diseases,
but this is the first study to show that it also
plays a role in protecting against cardiac aging and
diet-induced dysfunction.
All together, these results reinforce the idea that
the daily eating pattern has a profound impact on
both the body and the brain,” Panda said.
Gill noted that there
are some hurdles to clear before extrapolating this
research to humans.
“Humans don’t consume the same food every day,” he
said. “And our lifestyle is a major determinant of
when we can and cannot eat. But at the very minimum,
our studies offer some context in which we should be
pursuing such questions in humans.”
Melkani is optimistic
that the results could one day translate into
cardiac- and obesity-related health benefits for
humans.
“Time-restricted feeding would not require people to
drastically change their lifestyles, just the times
of day they eat,” Melkani said. “The take-home
message then would be to cut down on the late-night
snacks.”
See also
It's not just what you eat, but when you eat it: a
link between fat cell and brain clock molecules
(03/12/2012)
For more information
Science
Time-restricted feeding attenuates age-related
cardiac decline in Drosophila
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