Reply to: “Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patients”
Authors: Eric Trépo, Pierre Pradat, Jeanette J. McCarthy, Hans L. Tillmann
Journal: Journal of Hepatology (2012)

Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patientsJournal of HepatologyVol. 56Issue 5PreviewSteatosis is frequently observed in patients with chronic hepatitis C (CHC), and is associated with fibrosis progression and treatment failure [1,2]. Tillmann et al. recently reported a negative association between the interleukin 28B (IL28B) rs12979860 CC genotype, predicting sustained virological response [3], and steatosis in genotype-1 CHC [4]. However, whether this association was independent of other genetic factors was not evaluated. Full-Text PDF Open Access We thank Dr. Valenti et al. for raising an additional point that PNPLA3 might be associated with steatosis in the setting of HCV infection after controlling for IL28B [[1]Valenti L. Aghemo A. Stattermayer A.F. Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patients.J Hepatol. 2012; 56: 1209-1210Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar]. They demonstrate in their cohort of 567 treatment naïve patients that both IL28B (rs12979860) and PNPLA3 (rs738409) may contribute to steatosis. Furthermore, in their study the beneficial effect of IL28B was limited to the patients without the PNPLA3 risk allele "G" as rs738409. A role of PNPLA3 GG genotype for steatosis in HCV infected patients has been observed in several studies, especially when excluding genotype 3 patients [2Cai T. Dufour J.F. Muellhaupt B. Gerlach T. Heim M. Moradpour D. et al.Viral genotype-specific role of PNPLA3, PPARG, MTTP, and IL28B in hepatitis C virus-associated steatosis.J Hepatol. 2011; 55: 529-535Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar, 3Trépo E. Pradat P. Potthoff A. Momozawa Y. Quertinmont E. Gustot T. et al.Impact of patatin-like phospholipase-3 (rs738409 C>G) polymorphism on fibrosis progression and steatosis in chronic hepatitis C.Hepatology. 2011; 54: 60-69Crossref PubMed Scopus (154) Google Scholar, 4Müller T. Buch S. Berg T. Hampe J. Stickel F. Distinct, alcohol-modulated effects of PNPLA3 genotype on progression of chronic hepatitis C.J Hepatol. 2011; 55: 732-733Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar, 5Toyoda H. Kumada T. Favorable association between genetic polymorphisms near the IL28B gene and hepatic steatosis: direct or indirect?.J Hepatol. 2012; 56: 738-739Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar]. In the Duke cohort, we did not find a significant difference for steatosis in relation to PNPLA3, (25/52 vs. 67/127, p = 0.623). However, in the European cohort, the rs738409 SNP was used instead of SNP rs2281135. The SNP rs2281135 is considered a tagging SNP (rs2281135) for the likely causal SNP (rs738409) within the PNPLA3 region. Thus, as we had a tagging SNP (rs2281135) for the likely causal SNP (rs738409) within the PNPLA3 region only for the Duke cohort, we cannot rule out that the lack of a significant difference is due to the lack of accuracy of a surrogate SNP. Interestingly though, when grouped according to PNPLA3 rs2281135 GG vs. non-GG, the role of IL28B remained significant in the PNPLA3 rs2281135 GG patients only (p = 0.002), while it was only a trend in the non-GG patients (p = 0.46).An association of IL28B and steatosis was also found in several other [1Valenti L. Aghemo A. Stattermayer A.F. Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patients.J Hepatol. 2012; 56: 1209-1210Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar, 2Cai T. Dufour J.F. Muellhaupt B. Gerlach T. Heim M. Moradpour D. et al.Viral genotype-specific role of PNPLA3, PPARG, MTTP, and IL28B in hepatitis C virus-associated steatosis.J Hepatol. 2011; 55: 529-535Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar, 5Toyoda H. Kumada T. Favorable association between genetic polymorphisms near the IL28B gene and hepatic steatosis: direct or indirect?.J Hepatol. 2012; 56: 738-739Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar, 6Tillmann HL, Patel K, Muir AJ, Guy CD, Li JH, Lao XQ, et al. Beneficial IL28B genotype associated with lower frequency of hepatic steatosis in patients with chronic hepatitis C. J Hepatol 2011 [Epub ahead of print].Google Scholar] but not all studies. A study by Trépo et al., evaluating both PNPLA3 (rs738409) and IL28B (rs12979860), reported no association between steatosis and rs12979860 but for rs738409. Thus, a trend could not be excluded. The data for rs12979860 were not given in the original paper but are included now in Table 1. These data are actually in line with the other published data, in that way that there is a trend for IL28B CC genotype being associated with absence of steatosis, though not significantly (p = 0.12).Table 1Frequency of steatosis. (A) PNPLA3 grouping within IL28B groups in the Duke and European cohort respectively. (B) IL28B grouping within PNPLA3 groups in the Duke and European cohort respectively.In (A), ∗CC vs. non-CC significant at p= 0.002 in the Duke cohort; ∗∗CC vs. non-CC not significant at p= 0.12 in the European cohort.PNPLA3 rs2281135 shows only small trend for association with steatosis in the Duke cohort in either IL28B group. Interestingly, in the European cohort this trend was not significant in the "non-CC" group, but reached significance in the IL28B "CC" groups.In (B), ∗AA or AG vs. GG are not significant at p= 0.62 in the Duke cohort; ∗∗CC or CG vs. GG are significant at p= 0.003 in the European cohort. Open table in a new tab Of note, the IL28B CC genotype's impact seems to concern mainly patients without the "at risk" PNPLA3 GG genotype, thus confirming Dr. Valenti et al. observation. Trépo et al. also evaluated multiple tagging SNPs within the PNPLA3 region including rs2281135, which revealed a p value of 0.017 compared to the p value of 0.009 for rs738409 for steatosis >5%. These two SNPs, rs738409 and rs2281135, are partially correlated (i.e. in linkage disequilibrium) [[7]Speliotes E.K. Butler J.L. Palmer C.D. Voight B.F. GIANT Consortium MIGen Consortium et al.PNPLA3 variants specifically confer increased risk for histologic nonalcoholic fatty liver disease but not metabolic disease.Hepatology. 2010; 52: 904-912Crossref PubMed Scopus (286) Google Scholar].Thus, overall, the data indicate the PNPLA3 and IL28B have somewhat independent effects on steatosis. Furthermore, the study highlights that tagging SNPs are likely to be not accurate enough. To illustrate further, whereas we found steatosis associated with IL28B rs12979860 (the most strongly associated SNP for HCV clearance in Caucasians [[6]Tillmann HL, Patel K, Muir AJ, Guy CD, Li JH, Lao XQ, et al. Beneficial IL28B genotype associated with lower frequency of hepatic steatosis in patients with chronic hepatitis C. J Hepatol 2011 [Epub ahead of print].Google Scholar]), we did not find a similar significant association of steatosis with IL28B rs8880917, which is in linkage disequilibrium with rs12979860 and may be a poorer marker of treatment response. In summary, this data might highlight the importance of choosing the right SNP in situations where several tagging SNPs can be used.Conflict of interestThe authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript. We thank Dr. Valenti et al. for raising an additional point that PNPLA3 might be associated with steatosis in the setting of HCV infection after controlling for IL28B [[1]Valenti L. Aghemo A. Stattermayer A.F. Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patients.J Hepatol. 2012; 56: 1209-1210Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar]. They demonstrate in their cohort of 567 treatment naïve patients that both IL28B (rs12979860) and PNPLA3 (rs738409) may contribute to steatosis. Furthermore, in their study the beneficial effect of IL28B was limited to the patients without the PNPLA3 risk allele "G" as rs738409. A role of PNPLA3 GG genotype for steatosis in HCV infected patients has been observed in several studies, especially when excluding genotype 3 patients [2Cai T. Dufour J.F. Muellhaupt B. Gerlach T. Heim M. Moradpour D. et al.Viral genotype-specific role of PNPLA3, PPARG, MTTP, and IL28B in hepatitis C virus-associated steatosis.J Hepatol. 2011; 55: 529-535Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar, 3Trépo E. Pradat P. Potthoff A. Momozawa Y. Quertinmont E. Gustot T. et al.Impact of patatin-like phospholipase-3 (rs738409 C>G) polymorphism on fibrosis progression and steatosis in chronic hepatitis C.Hepatology. 2011; 54: 60-69Crossref PubMed Scopus (154) Google Scholar, 4Müller T. Buch S. Berg T. Hampe J. Stickel F. Distinct, alcohol-modulated effects of PNPLA3 genotype on progression of chronic hepatitis C.J Hepatol. 2011; 55: 732-733Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar, 5Toyoda H. Kumada T. Favorable association between genetic polymorphisms near the IL28B gene and hepatic steatosis: direct or indirect?.J Hepatol. 2012; 56: 738-739Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar]. In the Duke cohort, we did not find a significant difference for steatosis in relation to PNPLA3, (25/52 vs. 67/127, p = 0.623). However, in the European cohort, the rs738409 SNP was used instead of SNP rs2281135. The SNP rs2281135 is considered a tagging SNP (rs2281135) for the likely causal SNP (rs738409) within the PNPLA3 region. Thus, as we had a tagging SNP (rs2281135) for the likely causal SNP (rs738409) within the PNPLA3 region only for the Duke cohort, we cannot rule out that the lack of a significant difference is due to the lack of accuracy of a surrogate SNP. Interestingly though, when grouped according to PNPLA3 rs2281135 GG vs. non-GG, the role of IL28B remained significant in the PNPLA3 rs2281135 GG patients only (p = 0.002), while it was only a trend in the non-GG patients (p = 0.46). An association of IL28B and steatosis was also found in several other [1Valenti L. Aghemo A. Stattermayer A.F. Interaction between IL28B and PNPLA3 genotypes in the pathogenesis of steatosis in chronic hepatitis C non genotype-3 patients.J Hepatol. 2012; 56: 1209-1210Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar, 2Cai T. Dufour J.F. Muellhaupt B. Gerlach T. Heim M. Moradpour D. et al.Viral genotype-specific role of PNPLA3, PPARG, MTTP, and IL28B in hepatitis C virus-associated steatosis.J Hepatol. 2011; 55: 529-535Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar, 5Toyoda H. Kumada T. Favorable association between genetic polymorphisms near the IL28B gene and hepatic steatosis: direct or indirect?.J Hepatol. 2012; 56: 738-739Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar, 6Tillmann HL, Patel K, Muir AJ, Guy CD, Li JH, Lao XQ, et al. Beneficial IL28B genotype associated with lower frequency of hepatic steatosis in patients with chronic hepatitis C. J Hepatol 2011 [Epub ahead of print].Google Scholar] but not all studies. A study by Trépo et al., evaluating both PNPLA3 (rs738409) and IL28B (rs12979860), reported no association between steatosis and rs12979860 but for rs738409. Thus, a trend could not be excluded. The data for rs12979860 were not given in the original paper but are included now in Table 1. These data are actually in line with the other published data, in that way that there is a trend for IL28B CC genotype being associated with absence of steatosis, though not significantly (p = 0.12). In (A), ∗CC vs. non-CC significant at p= 0.002 in the Duke cohort; ∗∗CC vs. non-CC not significant at p= 0.12 in the European cohort. PNPLA3 rs2281135 shows only small trend for association with steatosis in the Duke cohort in either IL28B group. Interestingly, in the European cohort this trend was not significant in the "non-CC" group, but reached significance in the IL28B "CC" groups. In (B), ∗AA or AG vs. GG are not significant at p= 0.62 in the Duke cohort; ∗∗CC or CG vs. GG are significant at p= 0.003 in the European cohort. Of note, the IL28B CC genotype's impact seems to concern mainly patients without the "at risk" PNPLA3 GG genotype, thus confirming Dr. Valenti et al. observation. Trépo et al. also evaluated multiple tagging SNPs within the PNPLA3 region including rs2281135, which revealed a p value of 0.017 compared to the p value of 0.009 for rs738409 for steatosis >5%. These two SNPs, rs738409 and rs2281135, are partially correlated (i.e. in linkage disequilibrium) [[7]Speliotes E.K. Butler J.L. Palmer C.D. Voight B.F. GIANT Consortium MIGen Consortium et al.PNPLA3 variants specifically confer increased risk for histologic nonalcoholic fatty liver disease but not metabolic disease.Hepatology. 2010; 52: 904-912Crossref PubMed Scopus (286) Google Scholar]. Thus, overall, the data indicate the PNPLA3 and IL28B have somewhat independent effects on steatosis. Furthermore, the study highlights that tagging SNPs are likely to be not accurate enough. To illustrate further, whereas we found steatosis associated with IL28B rs12979860 (the most strongly associated SNP for HCV clearance in Caucasians [[6]Tillmann HL, Patel K, Muir AJ, Guy CD, Li JH, Lao XQ, et al. Beneficial IL28B genotype associated with lower frequency of hepatic steatosis in patients with chronic hepatitis C. J Hepatol 2011 [Epub ahead of print].Google Scholar]), we did not find a similar significant association of steatosis with IL28B rs8880917, which is in linkage disequilibrium with rs12979860 and may be a poorer marker of treatment response. In summary, this data might highlight the importance of choosing the right SNP in situations where several tagging SNPs can be used. Conflict of interestThe authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript. The authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.