Cholesterol proves healthy for medal winner

Dr Sandra Orgeig with a bearded lizard, one of the many species that increases its cholesterol due to a drop in body temperature.
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Monday, 29 April 2002

Dr Sandra Orgeig from the University of Adelaide will this week receive the prestigious Fenner Medal awarded by the Australian Academy of Science in Canberra.

The Fenner Medal recognises distinguished research in plants and non- mammalian animals by Australian scientists under the age of 40. Dr Orgeig, from the University's Department of Environmental Biology, will receive the medal and present a talk on her research at the Shine Dome in Canberra on Thursday, May 2.

For the past 10 years Dr Orgeig has been researching the crucial role that cholesterol plays in the healthy performance of human and animal lungs. Her work has involved a wide range of vertebrate species, including lungfish, salamanders, reptiles, marsupials and humans.

"Cholesterol has had some very bad press in the last 10 years or so," Dr Orgeig says. "The word conjures up terrible images of large fatty deposits in blood vessels and is generally associated with obesity. We're constantly told to lower our cholesterol intake and we're bombarded in supermarkets with 'low cholesterol' products.

"While this is all true, it is important to realise that cholesterol is a natural product, is produced by our bodies and has some very important physiological functions."

Her work centres on the role of cholesterol in pulmonary surfactant. Pulmonary surfactant is a complex substance that controls the surface tension of the fluid lining the inner lung. Secreted by the alveoli in the lungs, surfactant is a key ingredient in helping the lung to inflate, transfer oxygen and carbon dioxide to and from the blood, and defend against bacteria and other invaders.

Failure of the surfactant system causes the death of thousands of Australians each year. To date, the only treatment is the administration of an artificial surfactant via the airways, and external lung ventilation until the natural surfactant system repairs itself. The perfect artificial surfactant is the focus of intense interest and research around the world.

Dr Orgeig has discovered that the amount of cholesterol in pulmonary surfactant changes under different physiological conditions, such as changes in body temperature and exercise. In reptiles, amphibians or fish that have body temperatures of five or 10 degrees Celsius, the cholesterol prevents their surfactant from becoming hard like cold butter, thereby enabling healthy lung operation.

Her research could lead to new and better methods of treating respiratory diseases, as well as preserving lungs needed for life- saving transplants.

"Commercial surfactants are not usually stable over an extended temperature range," Dr Orgeig says.

"This thermal stability is crucial during the cold preservation of lungs destined for transplantation, for hypothermic patients or patients undergoing hypothermic surgery, or in other situations when body temperature is below 37C."

However, much work remains to be done, such as figuring out how cholesterol works in surfactant, where the surfactant cholesterol is made, and how it ends up in the alveoli.

"There is still quite a lot to do in terms of working out how and why cholesterol does what it does, but it is clear that at least in surfactant, cholesterol really is very important and it is not at all 'bad'," Dr Orgeig says.

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