Once oxidized, LDL is taken up by macrophages (cells of the immune system) that occupy the subendothelial space of the blood vessel wall and eventually form foam cells and fatty streaks (early atherosclerosis), ultimately forming artery-narrowing plaques and setting the stage for heart attacks.
Both factors are believed to be important in decreasing fatty streaks, the early signs of plaque formation in coronary arteries.
The researchers discovered mast cells in 50 percent of the normal vessel sections, in 84 percent of the fatty streaks
, and in 95 percent of the so-called shoulder, a rupture-prone area of the plaque (see illustration).
Rubin and his colleagues inserted the human gene for HDLs' primary protein into mice that ordinarily develop telltale fatty streaks in their arteries when fed a high-fat diet.
Fatty streaks did develop in engineered mice receiving ultra-high-fat cookies containing cocoa butter, but these deposits covered only one-eighth as much area as those of control mice on the same diet.
The apo A-1 increase, which in turn elevated total levelsof HDLs, "had a very profound effect" in preventing fatty streaks, Rubin concludes.
In subsequent work, Kruth and his co-workers observed the unesterified particles accumulating -- even before fatty streaks
appeared--in the arteries of rabbits fed high-cholesterol diets.
Preliminary results from a multicenter study show that teenagers can develop well-established fatty streaks in their coronary artery walls, and that some teens even develop artery-narrowing plaque.
Heart Study uncovered evidence of fatty streaks in children's arterial walls and showed that children with high blood cholesterol are likely to remain at risk of elevated blood choletserol as they grow older (SN:10/8/88, p.
Now, early results of another ongoing study, caled Pathobiological Determinants of Atherosclerosis in Youth (PDAY), confirm that by the time a person reaches age 19, smooth fatty streaks can form beneath the endothelial tissue lining the insides of arteries, developing into raised lesions by age 34.
At the same time, evidence of potential heart disease -- once thought to be confined to older people -- is being found in some children as young as 3 years of age, in the form of fatty streaks in the heart's main artery, the aorta.
In teenagers, fatty streaks may develop in and under the layer of cells that lines coronary artery walls.
Connors and his colleagues showed that a diet high in omega-3 fatty acids decreases serum cholesterol and LDL levels, reducing the risk that fatty streaks
will form in the arteries.