A new "platform" with a crucial role in the body's ability to process and take up fat from the diet has been found, according to a report in the April issue of the journal Cell Metabolism, published by Cell Press.
Researchers discovered a protein that sits on the inner surfaces of capillaries, where it delivers "packages" of dietary fat from the bloodstream to enzymes that prepare them for entry into cells of the body. Once inside cells, the fats are either burned as a rich source of energy or stored for later use.
"We've found a new, very important partner in a process people thought they understood 20 years ago," said Anne Beigneux of the University of California, Los Angeles.
While it is too soon to say whether the finding will have clinical implicationsin efforts to limit the body's capacity to store fat, for instanceone thing is for certain: "Soon, every biochemistry book will have to be revised," she said.
Dietary fats in mammals are packaged by the intestine into "chylomicrons," which are large triglyceride-rich lipoproteins, Beigneux explained. After reaching the bloodstream, the triglycerides within chylomicrons are broken down by an enzyme found along the surface of capillaries, mainly in the heart, skeletal muscle, and fat tissue. In those tissues, the so-called lipoprotein lipase enzyme is synthesized, secreted, and transported to the capillaries, where the packaged lipids are taken apart.
The fat "bundles" have to be broken down because the lipids are otherwise unable to get across cell membranes, Beigneux added.
The researchers "stumbled onto" a new player in the process after a team at Genentech found mutant mice with severe chylomicronemia, a condition in which the inability to properly process dietary fat leads to high levels of blood triglycerides.
The micewhich lacked a gene called glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1, or Gpihbp1exh
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Contact: Erin Doonan
edoonan@cell.com
617-397-2802
Cell Press
3-Apr-2007