Josh: While this is certainly an important genetic variation to find, I’m wondering if doctors would be able to use this information if they tested their patients. What could be done differently in treating high levels of triglycerides? This would be much more useful if a drug existed to treat this specific cause of elevated plasma TG levels.
A genetic variant found almost exclusively in individuals of Asian descent increases the risk of elevated triglycerides over four-fold, reports a comprehensive study in the August Journal of Lipid Research. In fact, all 11 subjects who carried both copies of this rare variant for apolipoprotein A-V had extremely high and dangerous triglyceride levels in their blood.
Apolipoprotein A-V is a recently discovered lipid-binding protein that likely plays an important role in metabolizing triglycerides. Some population studies with groups in China and Taiwan indicate that a polymorphism in the APOA5 gene (553 G>T shift) is associated with elevated plasma TG levels, which like cholesterol, increase the risk of heart disease.
To get a broader view of this potentially important gene polymorphism, Clive Pullinger and colleagues examined the frequency and impact of this variant in a population of Chinese-Americans, as well as four other Asian-American populations (Japanese, Korean, Southeast Asian, and Pacific Islander).
The researchers examined 541 individuals and found that 15.1% of Chinese-Americans with high plasma TG (>150 mg/dl) carried at least one copy of the 553T variant, compared with only 3.7% of those with normal TG levels; in non-Chinese Asians these values were 13.7% and 5.4%. When calculated, the 553T variant corresponds to a 4.4 and 2.5 times greater risk of elevated TG in Chinese-Americans and other Asians, respectively.
The frequency became even more prevalent at higher levels; 60% of individuals with TG of >500 mg/dl carried the variant, and at 1000 mg/dl the frequency rose to 80%. And the 11 subjects who had the variant in both copies of their APOA5 gene had an average TG concentration of over 2000 mg/dl, which can pose serious health risks.
This specific genetic change seems restricted to Asians, as the researchers studied 779 non-Asian subjects and found only 3 incidences of the 553T variant (2 Caucasian and 1 Hispanic).
“An apolipoprotein A-V gene SNP is associated with marked hypertriglyceridemia among Asian-American patients”. Clive R. Pullinger, Bradley E. Aouizerat, Irina Movsesyan, Vincent Durlach, Eric J. Sijbrands, Katsuyuki Nakajima, Annie Poon, Geesje M. Dallinga-Thie, Hiroaki Hattori, Lauri L. Green, Pui-Yan Kwok, Richard J. Havel, Philip H. Frost, Mary J. Malloy and John P. Kane. Journal of Lipid Research, Vol. 49, 1846-1854, August 2008.