Relationship between non-alcoholic steatohepatitis, PNPLA3 I148M genotype and bone mineral density in adolescents

Background & Aims It is uncertain whether non-alcoholic steatohepatitis (NASH) is a risk factor for low bone mineral density (BMD). Our aim was to investigate: (a) associations between NASH and BMD values and (b) associations between PNPLA3 I148M genotypes and BMD, in children with histologically proven non-alcoholic fatty liver disease (NAFLD). Methods Results BMD area (g/cm(2)) was measured using dual-energy X-ray absorptiometry (DEXA). NASH was diagnosed by a Steatosis, Activity and Fibrosis (SAF) score and FLIP algorithm. Genotyping for patatin-like phospholipase domain containing-3 (PNPLA3) I148M genotype (rs738409) (CC, CG and GG) was undertaken using the TaqMan SNP genotyping allelic discrimination method. Logistic regression was used to test associations [OR (95% CIs)] between low BMD, and both NASH and PNPLA3 I148M genotypes. Thirty-four adolescents (mean age 13.8 +/- 1.1 years) with histologically confirmed NAFLD were studied. Subjects with NASH (n = 25) had a lower BMD (means (SDs) 0.87 +/- 0.06 vs 0.97 +/- 0.12, P = 0.005), compared to subjects without NASH. Subjects with PNPLA3 CG+GG genotypes had a lower BMD compared with subjects with PNPLA3-CC genotype (means (SDs) 0.79 +/- 0.20 vs 0.92 +/- 0.10, P = 0.009). PNPLA3 CG+GG genotypes were independently associated with NASH [OR (95% CIs 1.78, 1.24, 2.99)], and low BMD was associated with both PNPLA3 CG+GG (OR 3.62 (95% CIs 1.21, 5.53), P = 0.028) and with SAF score (OR 2.76 (95% CIs 1.12, 5.41), P = 0.045). Conclusions Taken together the independent associations between: (a) low BMD and PNPLA3 CG+GG genotype; (b) low BMD and NASH; and (c) PNPLA3 CG+GG genotype and NASH, provide support for a causal relationship between NASH and low BMD.