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Blood levels Good HDL cholesterol can hurt the heart
For years, health experts have assumed that "good" cholesterol can protect against cardiovascular disease. Scientists have now found in a study that this does not seem to apply to all people. For some, a high level of HDL-C may even increase the risk of disease.
"Good" versus "bad" cholesterol
For years, a dispute raging over the good and bad cholesterol. High cholesterol levels are considered harmful to health, they are intended to promote arteriosclerosis (arteriosclerosis) and other cardiovascular diseases. However, according to experts, this only applies to the so-called "bad" LDL cholesterol. In contrast, the "good" HDL cholesterol should even counteract the health risk. Researchers at the Medical University of Innsbruck reported last year that it does not depend on the amount in the blood, but that the quality is crucial. However, an international research group has found that protective HDL cholesterol may even increase the risk of vascular disease.
Arteriosclerosis: Cholesterol is one cause of this. Image: Christoph Burgstedt - fotolia HDL probably not the direct protection factor
Although so-called HDL-cholesterol (HDL-C) has long been considered a "good cholesterol" to protect against vascular calcification and myocardial infarction, a new study now shows that a particularly high level of HDL-C even causes cardiovascular disease can favor. Namely, if a certain, rare genetic feature is present, reports the news agency dpa. As the large international team of scientists around Daniel Rader writes in the journal "Science", HDL is generally not the direct protection factor against heart disease, for which it is held by many people - including cardiologists.
Increased risk of heart disease
For cholesterol, which is not water-soluble but fat-soluble, the body has certain proteins that bring the cholesterol to where it's needed: LDL (Low-Density-Lipoprotein) refers to the body's smallest lipoproteins, the fats transport to the individual body regions. The most important task of HDL is to transport excess cholesterol from certain tissues, such as blood vessel walls, to the liver, where it is converted and then excreted. Because of this, high levels of HDL cholesterol have been proven to protect against atherosclerosis and its sequelae. The new study by researchers around Rader from the University of Pennsylvania in Philadelphia is the first evidence of a genetic mutation that increases the HDL-C value, but increases the risk of heart disease.
Mutation prevents protection factor
According to the researchers, the scientists had analyzed critical areas in the genome of 328 people with particularly high HDL-C levels in order to track down the genetic causes of such values. One gene they focused on was SCARB1, the major docking site for HDL on cell surfaces. It is said that the team encountered a human with no functional SCARB1 gene during the course of the investigations. The normal HDL-C level is about 50 milligrams, but for this woman he was extremely high at 150 milligrams per deciliter. Therefore, the researchers made stem cells of the 67-year-old and made them grow liver cells. The team said they were far less able to receive HDL than liver cells usually.
"The mutation prevents the receptor from reaching the cell surface where it has to be to record HDL," Rader said. This mutation was also found in 11 out of 524 other people with very high HDL-C levels. According to the dpa report, the medical team, in collaboration with research teams worldwide, confirmed that the rare occurrence of SCARB1 alteration can increase the risk of coronary heart disease. (Ad)