Rationale: The PNPLA3I148M variant is a major genetic risk factor for MASLD, yet its variable penetrance suggests additional environmental triggers. Gut microbial dysbiosis is implicated in MASLD pathogenesis, yet its interaction with PNPLA3I148M remains uncertain. This study explores how dysbiosis synergizes with PNPLA3I148M to drive metabolic dysfunction and MASLD progression. Methods: Gut microbiota profiles from 146 MASLD patients were analyzed. To mechanistically model the gene-diet-microbiome interaction, a murine “dual-hit” model combining Pnpla3I148M and Nlrp6 deficiency was developed. Mice were fed a CHOW or HFD, and subsequently subjected to metabolic, lipidomic, and microbial profiling. Interventions included antibiotic treatment, fecal microbiota transplantation, and Akkermansia muciniphila supplementation. Results: In MASLD patients, gut dysbiosis significantly correlated with metabolic variance in PNPLA3I148M-carriers, manifesting as an adiposity-dependent rise in serum triglycerides. In mice, Pnpla3I148M alone caused mild steatosis under obesogenic conditions, whereas combined with Nlrp6 deficiency it induced spontaneous MASLD even on CHOW diet, worsened by HFD. This phenotype featured gut barrier dysfunction, dysbiosis, hepatic lipid remodeling, and mitochondrial impairment. Mechanistically, dysbiosis enriched bile acid-transforming and ceramide-producing bacteria signature (e.g., Clostridium scindens, Alistipes finegoldii, Oscillibacter), elevating hydrophobic secondary bile acids and ceramides in portal circulation. These metabolites impaired hepatic mitochondrial oxidative phosphorylation, increased ROS, suppressed bile acid synthesis (Cyp7a1, Cyp27a1), and activated lipid uptake pathways (Srebf2/Ldlr, Cd36). Upregulation of ceramide synthase 6 (CerS6) and lipid droplet stabilizers (Plin2, Lipa) promoted intracellular lipid retention, establishing a self-amplifying gut–liver metabolic loop. Antibiotic depletion disrupted this axis, reversing metabolic dysfunction. Dysbiotic FMT transferred pathology to healthy mice, while complete microbiome restoration robustly improved metabolic health; single-strain Akkermansia treatment was partially effective. Conclusion: My findings establish PNPLA3I148M and dysbiosis as synergistic drivers of MASLD, with microbial dysregulation exacerbating genetic susceptibility through gut-liver axis disruption. Therapeutic modulation of the microbiome may offer a targeted strategy for high-risk PNPLA3I148M-carriers.
Madhuri Haque (Wed,) studied this question.