Gene research: Tests will focus on the Y6 gene and the extent that it determines the amount of fat stored in the body.

Gene research: Tests will focus on the Y6 gene and the extent that it determines the amount of fat stored in the body. Photo: Jim Rice

The body clock may be more influential than previously thought, with researchers finding that it could also play a role in how fat we become and contribute to the risk of diseases such as diabetes.

Researchers from the Garvan Institute of Medical Research in Sydney have found a specific gene which regulates the body clock also plays a role in growth hormone production. The Y6 gene is highly expressed in the only part of the brain known to control the body's circadian rhythm. However, molecular biologist Herbert Herzog said little was known about the Y6 gene.

If you eat at midnight … you might trigger something which upsets the system 

So to test the gene's influence on how much fat is stored on the body, the Garvan researchers collaborated with Sydney University's Amanda Sainsbury-Salis to breed mice without the Y6 gene.

<em>Illustration: Cathy Wilcox</em>

Illustration: Cathy Wilcox

They found in their youth, these mice were smaller and had less lean tissue than normal mice. Significantly, as they reached middle age, the mice grew substantially fatter than normal mice. And when fed a high-calorie, high-fat diet, the mice missing the Y6 gene became obese and developed metabolic problems similar to diabetes.

''It was a surprise because the changes were so massive in terms of the increase in body fat mass,'' Professor Herzog said.

Those mice bred without the Y6 gene recorded an increase in fat mass of 150 per cent, compared to their middle age peers still carrying the gene. He said for mice put on a high-calorie, high-fat diet, the difference was evident earlier and the percentage increase greater.

The relevance of findings, published in the journal Cell Metabolism on Wednesday, still need to be tested in humans where the gene encoding the Y6 receptor is altered. However, Professor Herzog said that given the development of anti-obesity drugs relied heavily on mouse studies, it was fair to assume the findings would prove relevant to humans.

The body's circadian rhythm, or body clock, controls daily variations including sleep pattern and hormone levels that rise and fall according to the time of day. The research showed there was a relationship between the body clock and body composition, as signalling through the Y6 gene was critical to the ways energy was used at different times of the day. ''If you eat at midnight … you might trigger something which upsets the system,'' Professor Herzog said.