Researchers examining a popular supplement that lines the shelves of health food stores have determined that, in mice at least, it lives up to its claim of lowering cholesterol. Furthermore, the supplement--known as guggulsterone--seems to control cholesterol levels in a different way than existing drugs, lending hope for a potential new class of cholesterol-lowering medications.
For more than 2000 years, people have extracted guggulsterone from the resin of the guggul tree in India. Locals consume it to treat a wide variety of ailments, from arthritis to obesity; in recent years, it's been sold in the West as a natural cholesterol-lowering agent. David Moore, a molecular biologist at Baylor College of Medicine in Houston who's a fan of guggulsterone and grows small guggul trees in his backyard, wanted to determine precisely how the extract lowers cholesterol.
Moore and his colleagues suspected that the mechanism might hinge on a receptor, called FXR, found in the nucleus of cells. When active, FXR limits how much cholesterol the body converts into bile acid, which is then excreted from the body. Indeed, Moore's team found that cells treated with guggulsterone inhibited FXR, implying that the compound help turn cholesterol into bile acid. The researchers then turned to two sets of mice: one that was normal, and one that lacked a functioning FXR receptor. After being fed a high-cholesterol diet for a week, some animals were given guggulsterone. In normal mice, cholesterol levels in their liver dropped close to normal; the guggulsterone didn't affect animals without FXR.
Unlike current cholesterol drugs, which block the production of cholesterol in the liver, guggulsterone acts by a different mechanism, possibly speeding up production of bile acids from cholesterol, or doing something else entirely. Other researchers are cautiously optimistic, but say that much more work needs to be done. "You're very lucky if it's that simple," says Ronald Evans, a molecular biologist at the Salk Institute in La Jolla, California.
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