By Merritt McKinney

NEW YORK, Apr 11 (Reuters Health) - Scientists in Massachusetts have discovered that the sugar-regulating hormone insulin plays a crucial role in moving fatty acids from the blood to fat-storage cells after a meal.

Although the research was conducted on the cellular level, eventually it may lead to a better understanding of how fat is metabolized in the body, the study's lead author told Reuters Health.

After a meal, levels of both sugar, or glucose, and fatty acids rise in the blood. Scientists knew already that insulin reduces glucose in the blood in two ways. First, the hormone signals the liver to slow its production of glucose. Second, insulin increases the uptake of sugar into tissues by causing glucose transporters within each cell to move to the surface where they draw sugar into the cell.

How the body lowers levels of fatty acids in the blood has been uncertain, however.

Now Dr. Harvey F. Lodish and colleagues at the Whitehead Institute for Biomedical Research at the Massachusetts Institute of Technology in Cambridge report that insulin is also involved in regulating levels of fatty acids in the blood. A report on the findings appears in the April issue of the journal Developmental Cell.

"Insulin causes cells to take up fatty acids from the blood," Lodish said in an interview. "It does so by a fundamentally similar mechanism" to how it handles sugar, he explained.

When the researchers added insulin to cells called adipocytes--which store most of the body's fat--fatty acid transporters moved to the surface of the cells from other parts of the cells. These transporters, FATP1 and FATP4, seem to promote the uptake of fatty acids into cells, because as the transporters congregated at the cell membrane, levels of fatty acids in the blood dropped.

Now that researchers understand how fatty acid transporters affect the uptake of fat on the cellular level, the next step, according to Lodish, is to measure the impact the transporters have on overall levels of fat in the body.

Genetically altering mice to have more or fewer fatty acid transporters may reveal the role these transporters have in the metabolism of fat by the whole body, he said. Such research could also lead to a better understanding of diseases that affect metabolism, including type 2 diabetes, Lodish and his colleagues note in their report.

SOURCE: Developmental Cell 2002;2:477-488.

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