Epidemiology

Hepatic fat contributes to ethnic differences in cardiometabolic risk factors

Last Updated: 2010-07-08 17:29:06 -0400 (Reuters Health)

By Victoria Stern

NEW YORK (Reuters Health) - Hepatic fat may worsen cardiometabolic risk profiles regardless of ethnicity or visceral fat, new research suggests.

The study, published online June 23 in American Journal of Clinical Nutrition, found that liver fat was correlated with concentrations of large very-low-density lipoproteins (VLDL) in African Americans, whites and Hispanics.

"The results also help explain the different metabolic risk profiles observed in African Americans, whites and Hispanics," study investigator Dr. Sonia Caprio, from Yale University, told Reuters Health in an interview. African Americans are less likely to have fatty livers, which may explain why they tend to have more favorable metabolic risk profiles compared to whites and Hispanics.

The prevailing theory is that visceral adipose tissue (VAT) has deleterious metabolic effects in adults. However, emerging evidence suggests that liver fat distribution may also play a pivotal role in determining the different lipoprotein profiles among African Americans, whites and Hispanics.

Dr. Caprio and her colleagues recruited 99 obese adolescents (33 white, 33 African American, and 33 Hispanic) with normal glucose tolerance and measured their VAT, their hepatic fat fraction (HFF), and their fasting lipoprotein particle number and size.

Although African American youths had a greater body-fat percentage than either whites (p=0.006) or Hispanics (p=0.007), overall they had a more favorable metabolic risk profile.

African Americans had lower triglyceride (p=0.001) and higher HDL (p=0.03) concentrations as well as lower concentrations of total (p=0.007), large (p=0.005), and medium VLDL (p<0.0001).

In addition, VAT and HFF were significantly higher in Hispanic (VAT, p<0.0001; HFF, p=0.01) and in white youths (VAT, p<0.0001; HFF, p=0.001) than in African Americans.

But regardless of ethnicity, liver fat played an important role in determining cardiometabolic risk profile in all three ethnic groups. In multivariate linear models, VAT predicted large HDL (p=0.003) and total small LDL (p=0.001) concentrations, while HFF predicted large VLDL concentrations (p=0.03).

Dr. Caprio went a step further in a new study, to be published online in July in Diabetes Care. She and her colleagues compared people with equal visceral fat content but discordant liver fat content. Only the subjects with more liver fat had abnormal metabolic profiles.

Although the current study focused on how patterns of fat distribution may be linked to ethnic differences in lipoprotein profiles, the researchers note that genetically driven interethnic differences also need to be considered in future studies.

http://link.reuters.com/bas56m

Am J Clin Nutr 2010.