Body clock regulating gene may be determining how fat we become

Researchers have suggested that a specific gene regulating our body clock could be playing a crucial role in determining how fat we become.

Evolution has preserved the ' neuropeptide Y (NPY) system', as it is known, in most species.

In man, the neurotransmitter NPY communicates with four well-known 'cell surface receptors' in the brain (Y1, Y2, Y4 and Y5), which in turn trigger the system's effects.

The new study has shown that mice have an additional receptor, Y6, which has profound effects on their body composition. Y6 is produced in a very small region of the brain that regulates the body clock, as well as growth hormone production.

PhD student Ernie Yulyaningsih, Dr Kim Loh, Dr Shu Lin and Professor Herbert Herzog from Sydney's Garvan Institute of Medical Research, together with Associate Professor Amanda Sainsbury-Salis, now at the University of Sydney, showed that mice without the Y6 gene were smaller, and had less lean tissue, than normal mice.

On the other hand, as they aged, these 'knockout mice' grew fatter than the normal mice, especially when fed a highfat diet. In that case, they became obese and developed metabolic problems similar to diabetes.

Professor Herbert Herzog said that their work shows that Pancreatic Polypeptide has a very high affinity for Y6 in mice, and probably controls the circadian aspect of food intake, as the same amount of calories eaten at different times of the day has different effects on body weight.

He said that the Y6 gene is highly expressed in a part of the brain called the ' hypothalamic suprachiasmatic nucleus ', which is known to control the body's circadian rhythm and may also critically modulate metabolic processes in response to food.