The PNPLA3 I148M variant is associated with immune cell infiltration and advanced fibrosis in MASLD: a prospective genotype-phenotype study

Abstract

Background: Increasing evidence reveals that immune cells significantly contribute to metabolic dysfunction-associated steatotic liver disease (MASLD) progression. The patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148M variant has been linked to hepatic inflammation and fibrosis; however, its role in immune cell infiltration and activation within the liver remains unclear.

Methods: Seventy patients with MASLD were prospectively enrolled. Genomic DNA was extracted from buccal swabs or liver biopsy samples, followed by single nucleotide polymorphism genotyping to determine the rs738409 SNP genotype at codon 148 of PNPLA3. Immunohistochemistry was conducted using CD3 and CD68 antibodies to quantify T cell and macrophage infiltration, respectively. Total RNA extracted from biopsy specimens was used for quantitative reverse transcription polymerase chain reaction to assess the expression of specific markers associated with immune cell activation.

Results: Among the 70 patients with MASLD, 34 had the GG genotype, whereas 21 and 15 had the GC and CC genotypes, respectively. The GG genotype group showed a higher proportion of advanced fibrosis (F3 or F4) than the GC + CC group (P = 0.051). GG genotype carriers exhibited significantly higher CD3⁺ and CD68⁺ cell counts in the periportal region than the GC/CC carriers (P < 0.05). The transcriptomic analysis revealed elevated expression of markers associated with chronic antigen stimulation and immune cell activation (CD8A, GZMB, CCL2, and TIMP1) in GG carriers compared with those of GC and CC (P < 0.05). Furthermore, correlations among various markers, including inflammatory, steatosis-associated, and fibrosis-associated markers, exhibited consistent positive correlations.

Conclusions: Our findings revealed that the PNPLA3 I148M variant and increased immune cell infiltration and activation were significantly correlated within the MASLD liver. Further studies are needed to elucidate the mechanistic links between this genetic variant and liver inflammation.

Keywords: Immune cell; Liver fibrosis; Metabolic dysfunction-associated steatotic liver disease; PNPLA3.