Interleukin-18 binding protein deficiency results in gut microbiota dysbiosis and aggravated diet-induced MASH in mice

Abstract

Background & Aims MASLD/MASH are now the most prevalent hepatic disorders worldwide. Growing evidence implicates physiological alterations in the gut-liver axis and gut microbiota dysbiosis in this process. IL-18 binding protein (IL-18BP) forms high affinity complexes with IL-18, thus blocking its interaction with IL-18 receptors.

Methods We used high-fat diet (HFD) and methionine choline deficient (MCD) diet to model MASLD/MASH in wild-type (WT) male mice (n = 6-8 mice per group). We also studied antimicrobial peptides (AMPs) production, gut microbiota composition and liver phenotype in Il18bp-/- male mice on both HFD and MCD diets (5-7 mice per group). We manipulated gut microbiota of Il18bp-/- and WT male mice through administration of phages, antibiotic and through co-housing experiments (n = 4-8 mice per group).

Results Feeding WT mice with a HFD or a MCD diet led to a decrease in ileal AMPs expressions (respectively by 63 and 37% for Lyz1; by 47 and 84% for Ang4; by 86 and 46% for Pla2g2a) and an enrichment in gut proteobacteria (respectively by 7 and 23 fold for α-proteobacteria; by 2.1 and 1.7 fold for δ-proteobacteria; by 14 and 20 fold for γ-proteobacteria) when compared to standard chow diet (p<0.05). These changes were associated with a reduction in the ileal Il18bp expression (respectively by 77 and 46%) in HFD and MCD diet-fed WT mice vs. chow diet-fed WT mice (p<0.05). Il18bp-/- mice exhibited a decrease in gut AMPs expression and storage (AMP granules area/crypt respectively decreased by 57 and 62.5% in Il18bp-/- vs. WT mice on HFD and MCD diets). Moreover, Clostridium/Turicimonas/Escherichia bacteria were constitutively overrepresented in gut microbiota of Il18bp-/- vs. WT mice in a diet-amplified manner. Compared to WT mice, Il18bp-/- mice exhibited increased diet-induced hepatic damage (circulating ALT 84 vs. 41 U/L on HFD; 1218 vs. 738 U/L on MCD diet, p <0.05), inflammation (liver TNF-α content 72 vs. 35 pg/g protein on HFD; 441 vs. 169 pg/g protein on MCD diet, p <0.05), and fibrosis (Sirius red 1.45 vs. 0.36% on HFD; 1.64 vs. 0.65% on MCD diet, p <0.01). These changes occurred independently of steatosis modification. Phages, antibiotic and co-housing experiments revealed that specific gut microbiota featuring Il18bp-/- mice is implicated in their exacerbated liver inflammation and fibrosis status.

Conclusions IL-18BP limits the progression of MASLD/MASH by maintaining a normal intestinal production of AMPs and composition of the gut microbiota.

Impact and implications Increasing IL-18BP levels represents a novel therapeutic perspective for patients suffering from MASLD/MASH and gut microbiota dysbiosis.