Humans Eye Fix For Fat Rats
The Age
Monday February 5, 2001
Obese rats given a chemical called MSH have shown a huge reduction in feeding, prompting hopes that the chemical could be used to treat human obesity.
The rats, which had been fed a diet that included chips, pies, cake and dim-sims, showed less interest in eating for about four hours after being given the chemical.
MSH, or alpha melanocyte stimulating hormone, occurs naturally in human brains and causes a reduction in feeding. But in obese people and rats, the brain's regulation of food intake is altered.
Margaret Morris, an associate professor of pharmacology at Melbourne University, and Michelle Hansen, a PhD student in the department, investigated the effect of MSH on obese rats. They also looked at the effects of another chemical, NPY, which stimulates feeding.
In the obese rats - which, like obese people, had increased triglyceride and cholesterol levels - Dr Morris noticed reduced concentrations of MSH. ``It was as if their brains had adapted to their fatness," she said.
It was only when the rats' levels of MSH were artificially elevated that they cut their food intake.
Rats fed a low-fat diet also responded to MSH but not to as great an extent.
The findings will be published in the journal Brain Research this month.
``This has clear implications for the treatment of obesity if drugs which can easily access the brain can be developed," Dr Morris said.
About 40 per cent of Australia's adult population is overweight or obese, putting a $400 million annual burden on health care costs.
The need for treatment was increasingly pressing as the number of Australians who were overweight or obese had increased by 5 per cent in the past decade, Dr Morris said.
Targeting the brain is important to finding successful treatments as food intake is regulated by the region of the brain known as the hypothalamus. However, scientists are yet to find a way of penetrating the ``blood-brain" barrier which stops chemicals moving from the blood into the brain. The existence of this barrier means MSH could not simply be injected into people's blood streams.
In Dr Morris' experiments, MSH was injected into the rats' brain fluid - a procedure that would not be appropriate in humans.
Dr Morris' laboratory is examining other brain chemicals and their effect on appetite.
© 2001 The Age