Researchers have identified two genetic mutations that are fairly common in individuals of African descent and are associated with a 50 percent reduction in LDL (“bad”) cholesterol.

It has been shown previously, in mouse studies, that other mutations in the gene, called PCSK9, cause High cholesterol levels with raised LDL levels.

To see if there might be PCSK9 variations that have the opposite effect, Dr. Jonathan Cohen and colleagues from the University of Texas Southwestern Medical Center at Dallas analyzed the DNA sequence of PCSK9 in 128 adults with low LDL levels. Half the subjects were African American.

One or other of two so-called “nonsense” mutations in PCSK9 were found in 2 percent of African Americans, but in less than 0.1 percent of European Americans, the team reports in the research journal Nature Genetics.

Carriers of the variant genes had sharply lower LDL and total cholesterol levels compared with non-carriers.

Cohen’s group noted a similar frequency of these two PCSK9 mutations in an independent population-based group of 850 African Americans from Cook County, Illinois.

The researchers point out that the genetic mutations identified are “the most common sequence variants yet described to have large effects on plasma cholesterol levels.”

SOURCE: Nature Genetics, online January 16, 2005.