Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Sparrowhawk on 03/10/2008 22:07:36
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Alison Dennis asked the Naked Scientists:
Why do end stage cancer and AIDS sufferers lose weight so rapidly. Is there an increase in metabolism? Those on starvation diets seem to take much longer to become emaciated.
What do you think?
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The phenomenon of extreme and inappropriate weight loss seen amongst terminal patients with malignancies is referred to as cancer cachexia; people can look gaunt, wasted and very weak.
For a long time scientists suspected that the cause was inflammatory chemicals called cytokines that are normally produced by immune and other cells to regulate the activity of other branches of the immune system. Researchers think that cancers inappropriately pump out these signals into the bloodstream where they cause knock-on effects including suppressing appetite. The identity of the signals responsible wasn't known, however.
But recently scientists announced that they have successfully tracked down one of the chemical culprits, a molecule called MIC-1 or macrophage inhibitory cytokine 1. Blood levels of MIC-1 in patients with prostate cancer were directly correlated with tumour-associated weight loss. And when prostate cancers were transplanted into mice the animals lost weight except when an antibody designed to soak up MIC-1 was give at the same time.
MIC-1 seems to bind to receptors (chemical docking stations) in the brain's hypothalamus causing appetite suppression. The ability to block the effect in animals strongly suggests that the same trick could work in human cancer victims, helping them to remain better nourished and therefore stronger.
Reference - the work above was published in Nature Medicine in November 2007 and was carried out by Heiko Johnen et al.
Nature Medicine 13, 1333-1340 (1 November 2007) | doi:10.1038/nm1677
Chris
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Listen to the answer to this question on our podcast. (http://www.thenakedscientists.com/HTML/podcasts/show/2009.10.04/)