Caption: Structure of parathyroid hormone-related protein (PTHrP), which has been implicated in cancer-related cachexia.
Source: The Protein Data Bank
No matter how much high-calorie food they eat or nutritionally fortified shakes they drink, many people with cancer just can’t seem to maintain their body weight. They lose muscle and fat, sometimes becoming so weak that they can’t tolerate further treatment. Called cachexia, this progressive wasting syndrome has long troubled patients and their families, as well as baffled scientists searching for ways to treat or perhaps even prevent it.
Some previous studies [1-3] have observed that humans and mice suffering from cachexia have “activated” brown fat. This type of fat, as I explained in a previous post, has the ability to convert its chemical energy into heat to keep the body warm. Intrigued by these hints, a team led by Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School in Boston recently decided to explore whether tumor cells might secrete molecules that spur similar brown fat-like activity, causing a gradual depletion of the body’s energy stores.
Using Lewis lung carcinoma (LLC) cells, which cause tumors and cachexia when injected into mice, the NIH-funded team identified four proteins that boosted heat production in mouse fat cells grown in laboratory dishes. Further studies revealed that one of these proteins, called parathyroid hormone-related protein (PTHrP), seemed to be responsible for triggering a phenomenon called “browning.”
Many white adipose tissues, which store fat in large droplets and are often thought of as the bad fat tissue, contain pockets of so-called beige cells.
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