Eating affects the body clock

Researchers said eating was integral to maintaining the body's internal clock Keystone

Swiss researchers have found new evidence to support their findings that eating habits influence the internal body clock in humans.

A Geneva University study, published in the American medical journal Cell, found that a metabolic enzyme known as SIRT1 stimulated the timing element in genes, helping to regulate the body’s functions.

According to the Frontiers in Genetics research, the brain contains a central “clock” in that is in charge of body functioning. This clock then uses miniscule timers inside gene cells in organs to control the body’s daily workings.

The team argue that the brain clock is affected by light and day cycles, while cellular clocks are coordinated by metabolism.

By swopping the night and day cycles in cells and in live mice over a two-week period, the team showed that the brain’s clock became inverted and that through feeding rhythms other organ clocks were adjusted.

The team were building on their previous research into how metabolism – the cell’s chemical processes – plays a major influence on bodily functions by working to coordinate all cellular clocks.

“We discovered ten years ago that virtually every cell in our body has a clock,” Ueli Schibler, head of the research team, told swissinfo.

“Liver clocks, skin clocks. These countless clocks have to be synchronised. We discovered that it’s feeding cycles that synchronise them.”

Reset daily

Schibler explained that cellular clocks anticipated and coordinated processes in the body, for example by generating a stock of glucose in the day and destroying it at night.

“Most of our physiology is actually cyclical, it goes up and down. You realise when you have jet lag that the rhythm is disturbed. Not only does your brain have a rhythm problem but also all your other organs.”

The team’s research in 2000 experimented with feeding cycles in rats and mice and showed that SIRT1 acted as a sensor, determining if cells were metabolising or not. It would then modify an important protein in cell clocks.

“We said let’s see if metabolism is influencing the clocks and we did these feeding rhythms and found the feeding rhythms were the most dominant synchroniser, or timing cue, for these cell clocks.

“But we still didn’t know the mediator, or in other words what connects them chemically, and that is what this paper is about.

“If you want to have really strong synchronisation or oscillation in every tissue you need to synchronise these individual cellular clocks every day. This is mostly done by metabolism.”

Schibler said the team would continue to study how the metabolic enzyme worked.

He added that the research could pave the way for the further development of inhibitor and activator drugs that could be used to control SIRT1 and thereby, adapt body clocks during times of change such as jet lag.

“Perhaps it would be possible to synchronise the liver clocks after jet lag by taking a pill containing a repressor of SIRT1,” Schibler said.

“Now we can try to inject [the SIRT1 inhibitor] Sirtinol into mice and see whether it switches their phases. As this evidence was not known before, no one has tried to change phases in the organs but I think people will do that now.”

swissinfo, Jessica Dacey

The body clock

Humans have a central internal body clock that allows them to adapt to alternating day and night cycles.

The internal body clock is a mechanism situated in the brain’s hypothalamus.

It anticipates changes in the environment and coordinates various body functions such as sleep and metabolism. Each neuron involved has its own molecular clock, a group of genes with a biological rhythm of 24 hours that fluctuate in synchronicity with light.

Cells in the body have their own miniscule oscillations that are synchronised by the central clock in order to maintain activity in each organ. The Frontiers in Genetics team has found that the rhythm of eating times is the main stimulus of these cellular clocks.

Frontiers in Genetics

The research team has its base at Geneva University and brings together more than 200 researchers from around Switzerland who are experts in the study of genes, chromosomes and the embryonic development of organisms.

The team is supported in part by the Swiss National Science Foundation. It is also considered a National Centre of Competence in Research.