Long‐term hypercaloric diet exacerbates metabolic liver disease in PNPLA3 I148M animals

Abstract

Background & Aims Nonalcoholic fatty liver disease (NAFLD) is a major health burden associated with the metabolic syndrome leading to liver fibrosis, cirrhosis and ultimately liver cancer. In humans, the PNPLA3 I148M polymorphism of the phospholipase patatin‐like phospholipid domain containing protein 3 (PNPLA3) has a well‐documented impact on metabolic liver disease. In this study, we used a mouse model mimicking the human PNPLA3 I148M polymorphism in a long‐term high fat diet (HFD) experiment to better define its role for NAFLD progression. Methods Male mice bearing wild‐type Pnpla3 (Pnpla3WT), or the human polymorphism PNPLA3 I148M (Pnpla3148M/M) were subjected to HFD feeding for 24 and 52 weeks. Further analysis concerning basic phenotype, inflammation, proliferation and cell death, fibrosis and microbiota were performed in each time point. Results After 52 weeks HFD Pnpla3148M/M animals had more liver fibrosis, enhanced numbers of inflammatory cells as well as increased Kupffer cell activity. Increased hepatocyte cell turnover and ductular proliferation were evident in HFD Pnpla3148M/M livers. Microbiome diversity was decreased after HFD feeding, changes were influenced by HFD feeding (36%) and the PNPLA3 I148M genotype (12%). Pnpla3148M/M mice had more faecal bile acids. RNA‐sequencing of liver tissue defined an HFD‐associated signature, and a Pnpla3148M/M specific pattern, which suggests Kupffer cell and monocytes‐derived macrophages as significant drivers of liver disease progression in Pnpla3148M/M animals. Conclusion With long‐term HFD feeding, mice with the PNPLA3 I148M genotype show exacerbated NAFLD. This finding is linked to PNPLA3 I148M‐specific changes in microbiota composition and liver gene expression showing a stronger inflammatory response leading to enhanced liver fibrosis progression.

Impact of PNPLA3 I148M on alpha-1 antitrypsin deficiency-dependent liver disease progression

“…Increased NAFLD disease progression in animals with the PNPLA3 I148M polymorphism can be triggered by WSD. [24] Interestingly, mice with PiZ and PiZ/PNPLA3 I148M showed significantly less liver damage than the PNPLA3 I148M group. Moreover, we did not observe an increase in fat accumulation in the liver between PiZ groups, but we saw a decrease in lipid parameters in the PiZ groups compared to non-PiZ groups, which is in accordance with the lower body and liver weight of the PiZ groups.…”

“…[15,34] We here tested our working WT and PNPLA3 I148M data as recently published. [24] Data are expressed as mean ± SEM from 9 to 10 mice per group. *p < 0.05; **p < 0.01; ***p < 0.001; ordinary one-way ANOVA with Tukey's multiple comparison test or Kruskal-Wallis test with Dunn's post hoc test.…”

“…WT and PNPLA3 I148M control groups after administration of Western-style diet were shared in terms of the 3Rs ("replacement, reduction and refinement") according to the animal welfare (Authority for Environment Conservation and Consumer Protection of the State of North Rhine-Westphalia, LANUV, Recklinghausen, Germany) and recently published. [24] All animal groups were treated in parallel to avoid batch effects.…”

“…A western-style diet (WSD) triggers stronger NAFLD disease progression in animals with the PNPLA3 I148M polymorphism, especially after long-term feeding. [24] Therefore, we challenged all 4 animal strains with WSD diet for 24 weeks. Indeed, we saw significant increases of the liver transaminases AST and ALT in the PNPLA3 I148M group compared to WT controls (Figure 6A).…”

Usefulness of PNPLA3 variant for predicting hepatic events in steatotic liver disease: a matter of ethnicity or baseline risk?

“…Moreover, they speculated that therapeutic strategies capable of lowering the hepatic levels of the variant PNPLA3 protein, if confirmed effective in the ongoing studies in MASLD individuals, should be eagerly awaited in this Country. Indeed, while the latest experimental studies in the homozygous PNPLA3 148 M/M (rs738409 GG) knock‐in‐mutant mice are further extending our knowledge of the mechanisms by which the variant PNPLA3 protein promotes the severity of the MASLD phenotype, 8 implicating even changes in the gut microbiota, PNPLA3 silencing with antisense oligonucleotides was already proven effective in reducing inflammation and fibrosis in this same animal model 9 …”