Haptoglobin 2 Allele is Associated With Histologic Response to Vitamin E in Subjects With Nonalcoholic Steatohepatitis

Abstract

Background: Haptoglobin (Hp) genotype has been linked to oxidative stress and cardiovascular outcomes in response to vitamin E (VitE) among patients with diabetes mellitus. Its effect on histologic response to VitE in nonalcoholic steatohepatitis (NASH) is unknown.

Goals: Our objective was to determine if Hp genotype associates with response to VitE in patients with NASH.

Study: A post hoc analysis of 228 patients receiving VitE or placebo in 2 clinical trials was performed. Regression analysis was used to assess the effect of VitE versus placebo, by Hp genotype (1-1, 2-1, or 2-2), on histologic features and laboratory markers of nonalcoholic fatty liver disease, comparing baseline to end of treatment values. An interaction term was included in the regression models to assess differential treatment effect across Hp genotype.

Results: Hp 2-2 patients treated with VitE versus placebo showed significant histologic improvement (51% vs. 20%; OR=4.2; P=0.006), resolution of steatohepatitis (44% vs. 12%; OR=6.2; P=0.009), decrease in nonalcoholic fatty liver disease Activity Score (NAS) (-2.2 vs. -0.6; P=0.001), and decrease in liver enzymes alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase. Hp 2-1 patients on VitE versus placebo showed improved resolution of steatohepatitis, NAS and liver enzymes. Hp 1-1 patients showed no significant improvement in histology or liver enzymes. VitE had no effect on fibrosis stage in any group. Regression analysis showed incremental benefit of having Hp 2-2 or 2-1 versus 1-1 for all liver enzyme.

Conclusions: Hp 2 allele is associated with greater histologic and biological improvement in NASH with VitE treatment compared with the Hp 1 allele.

Figure 1:

(A) Study design flow diagram depicting enrollment and post-hoc exclusions for the two clinical trials, PIVENS and TONIC. (B) Distribution of haptoglobin (Hp) genotypes. Hp genotypes of study participants were determined by conventional polymerase chain reaction (PCR) using two primer sets (primers A/B; C/D). For each subject, PCR products of the two primer sets were pooled, resolved on agarose gel, and visualized under ultraviolet light. Hp 1–1 was identified by a sole 1757-bp band; Hp 2–2 by two bands at 3481-bp and 349-bp; and Hp 2–1 by bands at 1757-bp and 349-bp (with or without a faint band at 3481; and Hp 2–1 by bands at 1757-bp and 349-bp (with or without a faint band at 3481-bp).Abbreviations: Hp, haptoglobin; EOT, end of treatment; PCR, polymerase chain reaction; PIVENS, Pioglitazone versus Vitamin E versus Placebo for the Treatment of Non-diabetic Patients with Nonalcoholic Steatohepatitis; TONIC, Treatment of Nonalcoholic Fatty Liver Disease In Children; VitE, vitamin E.

Figure 2:

Hematoxylin and eosin-stained liver sections were evaluated in a blinded manner to determine scores for steatosis (0–3), lobular inflammation (0–3) and hepatocellular ballooning (0–2) at the beginning of the original trials and at the end-of-treatment (EOT). Changes in these scores from baseline to EOT were analyzed for Hp 2–2, Hp 2–1 and Hp 1–1 patients treated with vitamin E (VitE; blue bars) versus placebo (orange bars). Changes in steatosis (A), lobular inflammation (B) and hepatocellular ballooning (C) are shown, together with p-values comparing VitE versus placebo for each genotype.