There has been a widespread misconception among physicians that African Americans are protected from developing nonalcoholic steatohepatitis (NASH). However, a formal histologic and metabolic comparison against well-matched Caucasians has never been performed.
Sixty-seven African American patients were matched 2:1 to Caucasians (n = 134) for age, sex, BMI, hemoglobin A1c, and prevalence of type 2 diabetes mellitus (T2DM). Screening for NASH included measurement of intrahepatic triglyceride content by proton MRS (1H-MRS), followed by a liver biopsy if patients had hepatic steatosis. Insulin resistance was estimated during an oral glucose tolerance test using the Matsuda Index.
Compared with Caucasians, African American patients had a lower intrahepatic triglyceride content (mean ± SD 6.1 ± 6.8% vs. 9.4 ± 7.5%, P = 0.007) and the presence of nonalcoholic fatty liver disease (NAFLD) was less common (25.0% vs. 51.9%, P = 0.003). However, prevalence of NASH was not different between ethnicities in patients with NAFLD (57.1% vs. 73.3%, P = 0.12). Moreover, they showed similar severity in each of the individual histologic parameters (inflammation, ballooning, and fibrosis). Among patients with NAFLD, insulin resistance was similar between both ethnic groups (Matsuda Index: 3.3 ± 1.8 vs. 3.1 ± 1.9, P = 0.61; adipose tissue insulin resistance [Adipo-IR] index: 5.7 ± 4.6 vs. 6.4 ± 4.7 mmol/L ⋅ µU/mL, P = 0.53) but appeared to be worse in African American versus Caucasian patients without NAFLD (Matsuda Index: 4.9 ± 3.6 vs. 7.0 ± 4.9, P = 0.11; Adipo-IR: 3.9 ± 2.8 vs. 2.7 ± 2.3 mmol/L ⋅ µU/mL, P = 0.06). African American patients also had lower plasma triglycerides and higher HDL cholesterol, independent of the severity of intrahepatic triglyceride.
Although African Americans have lower intrahepatic triglyceride accumulation, once NAFLD develops, NASH occurs as frequently, and as severe, as in Caucasian patients. Therefore, African Americans with NAFLD should be screened for NASH with the same degree of clinical resolve as in Caucasian patients.