Variant PNPLA3 increases the HCC risk: prospective study in patients treated at the Saarland University Medical Center

Altered profiles of circulating cytokines in chronic liver diseases (NAFLD/HCC): Impact of the PNPLA3I148M risk allele

BACKGROUND

Individuals carrying the risk variant p.I148M of patatin-like phospholipase domain-containing protein 3 (PNPLA3) have a higher susceptibility to fatty liver diseases and associated complications, including HCC, a cancer closely linked to chronic inflammation. Here, we assessed circulating cytokine profiles for patients with chronic liver diseases genotyped for PNPLA3.

METHODS

Serum concentrations of 22 cytokines were measured by multiplex sandwich-ELISA. The cohort comprised 123 individuals: 67 patients with NAFLD without cirrhosis (57 steatosis, 10 NASH), 24 patients with NAFLD with cirrhosis, 21 patients with HCC (15 cirrhosis), and 11 healthy controls. Receiver operator characteristic analyses were performed to assess the suitability of the cytokine profiles for the prediction of steatosis, cirrhosis, and HCC.

RESULTS

HGF, IL-6, and IL-8 levels were increased in patients, with ∼2-fold higher levels in patients with cirrhosis versus healthy, while platelet derived growth factor-BB (PDGF-BB) and regulated on activation, normal T cell expressed and secreted (RANTES) showed lower concentrations compared to controls. Migration inhibitory factor and monocyte chemoattractant protein-1 (MCP-1) were found at higher levels in NAFLD samples (maximum: NAFLD-cirrhosis) versus healthy controls and HCC samples. In receiver operator characteristic analyses, migration inhibitory factor, IL-8, IL-6, and monocyte chemoattractant protein-1 yielded high sensitivity scores for predicting noncirrhotic NAFLD (vs. healthy). The top combination to predict cirrhosis was HGF plus PDGF-BB. Migration inhibitory factor performed best to discriminate HCC from NAFLD; the addition of monokine induced gamma (MIG), RANTES, IL-4, macrophage colony-stimulating factor (M-CSF), or IL-17A as second parameters further increased the AUC values (> 0.9). No significant impact of the PNPLA3I148M allele on cytokine levels was observed in this cohort.

CONCLUSIONS

Cytokines have biomarker potential in patients with fatty liver, possibly suited for early HCC detection in patients with fatty liver. Patients carrying the PNPLA3 risk allele did not present significantly different levels of circulating cytokines.

The Pnpla3 Variant I148M Reveals Protective Effects Towards Hepatocellular Carcinoma in Mice via Restoration of Omega-3 Polyunsaturated Fats

Alcohol consumption and high caloric diet are leading causes of progressive fatty liver disease. Genetic variant rs738409 in patatin-like phospholipase domain-containing protein 3 (PNPLA3 rs738409 C>G) has been repeatedly described as one of the major risk loci for alcoholic liver cirrhosis (ALC) and hepatocellular carcinoma (HCC) in humans, however, the mechanism behind this association is incompletely understood. We generated mice carrying the rs738409 variant (PNPLA3 I148M) in order to detect genotype-phenotype relationships in mice upon chow and alcohol-high fat/high sugar diet (EtOH/WD). We could clearly demonstrate that the presence of rs738409 per se is sufficient to induce spontaneous development of steatosis after one year in mice on a chow diet, whereas in the setting of unhealthy diet feeding, PNPLA3 I148M did not affect hepatic inflammation or fibrosis, but induced a striking lipid remodelling, microvesicular steatosis and protected from HCC formation. Using shot gun lipidomics, we detected a striking restoration of reduced long chain-polyunsaturated fatty acids (LC-PUFA)-containing TGs, docosapentaenoic acid (C22:5 n3) and omega-3-derived eicosanoids (5-HEPE, 20-HEPE, 19,20-EDP, 21-HDHA) in PNPLA3 I148M mice upon EtOH/WD. At the molecular level, PNPLA3 I148M modulated enzymes for fatty acid and TG transport and metabolism. These findings suggest (dietary) lipids as an important and independent driver of hepatic tumorigenesis. Genetic variant in PNPLA3 exerted protective effects in mice, conflicting with findings in humans. Species-related differences in physiology and metabolism should be taken into account when modelling unhealthy human lifestyle, as genetic mouse models may not always allow for translation of insight gained in humans.

Correlation between PNPLA3 rs738409 polymorphism and hepatocellular carcinoma: a meta-analysis of 10,330 subjects

PURPOSE

The correlation between patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 polymorphism and hepatocellular carcinoma was investigated by several pilot studies, but the results of these studies were controversial. Therefore, we performed this study to better assess the relationship between PNPLA3 rs738409 polymorphism and the likelihood of hepatocellular carcinoma.

METHODS

Eligible studies were searched in PubMed, Medline, EMBASE, and Web of Science. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between PNPLA3 rs738409 polymorphism and hepatocellular carcinoma.

RESULTS

A total of 17 studies with 10,330 participants were analyzed. A significant association with the likelihood of hepatocellular carcinoma was detected for the PNPLA3 rs738409 polymorphism in dominant (P = 0.0001; OR 0.66; 95% CI 0.53, 0.82), recessive (P < 0.0001; OR 2.32; 95% CI 1.76, 3.06) and allele (P < 0.0001; OR 0.64; 95% CI 0.53, 0.77) comparisons. Further subgroup analyses revealed that the PNPLA3 rs738409 polymorphism was significantly associated with the likelihood of hepatocellular carcinoma in Caucasians (dominant model: P < 0.0001, OR 0.57, 95% CI 0.45, 0.71; recessive model: P < 0.0001, OR 2.74, 95% CI 2.02, 3.71; allele model: P < 0.0001, OR 0.56, 95% CI 0.46, 0.67). However, no positive results were detected in Asians.

CONCLUSIONS

Our findings indicated that the PNPLA3 rs738409 polymorphism may serve as a potential biological marker of hepatocellular carcinoma in Caucasians.