The Association Between Hepatic Fat Content and Liver Injury in Obese Children and Adolescents

Effects of ethnicity, insulin resistance, and common gene variants

Nicola Santoro, MD, PHD, Ariel E. Feldstein, MD, PHD, Erik Enoksson, MS, Bridget Pierpont, MA, Romy Kursawe, PHD, Grace Kim, MD and
Sonia Caprio, MD

Diabetes Care December 28, 2012  Published online before print December 28, 2012, doi: 10.2337/dc12-1791

Abstract

OBJECTIVE Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH) are highly prevalent in obese youth. Herein, we aimed to study the association between hepatic fat accumulation as assessed by magnetic resonance imaging and circulating levels of cytokeratin-18 (CK-18) fragments, a robust NASH biomarker, and to explore the impact on this association of ethnicity, insulin resistance, and single nucleotide polymorphisms (SNPs) associated with steatosis (rs738409 in the PNPLA3, rs1260326 in the GCKR) or NASH severity (rs2645424 in the FDFT1).

RESEARCH DESIGN AND METHODS Two-hundred twenty-nine obese youths (87 Caucasians, 61 African Americans, and 81 Hispanics; mean age, 12.8 ± 2.9 years; mean BMI, 31.4 ± 7.4) underwent magnetic resonance imaging, oral glucose tolerance test, and CK-18 levels measurement; 12 subjects underwent liver biopsy.

RESULTS African Americans showed lower CK-18 levels than Hispanics (P < 0.001) and Caucasians (P = 0.004). Hepatic fat content (HFF%) and whole body insulin sensitivity index (WBISI) modulated CK-18 levels in Caucasians and Hispanics (P = 0.02 and P = 0.011), but not in African Americans; in fact, CK-18 was associated with HFF% and WBISI in Caucasians (P = 0.0018 and P < 0.0001) and Hispanics (P < 0.0001 and P = 0.02), but not in African Americans (both P = 0.5). The PNPLA3 SNP showed association in Caucasians (P = 0.02) and Hispanics (P = 0.05), and FDFT1 SNP showed an association in Caucasians (P = 0.05) and Hispanics (P = 0.02), with the same trend in African Americans (P = 0.07).

CONCLUSIONS African Americans have lower levels of CK-18 than Caucasians and Hispanics irrespective of HFF% and insulin resistance. Moreover, SNPs in the PNPLA3 and FDFT1 may drive the individual predisposition to development of hepatic injury.