Dynamics of Liver Macrophage Subsets in a Novel Mouse Model of Non-Alcoholic Steatohepatitis Using C57BL/6 Mice

Impacts of liver macrophages, gut microbiota, and bile acid metabolism on the differences in iHFC diet-induced MASH progression between TSNO and TSOD mice

BACKGROUND

Tsumura-Suzuki non-obese (TSNO) mice exhibit a severe form of metabolic dysfunction-associated steatohepatitis (MASH) with advanced liver fibrosis upon feeding a high-fat/cholesterol/cholate-based (iHFC) diet. Another ddY strain, Tsumura-Suzuki diabetes obese (TSOD) mice, are impaired in the progression of iHFC diet-induced MASH.

AIM

To elucidate the underlying mechanisms contributing to the differences in MASH progression between TSNO and TSOD mice.

METHODS

We analyzed differences in the immune system, gut microbiota, and bile acid metabolism in TSNO and TSOD mice fed with a normal diet (ND) or an iHFC diet.

RESULTS

TSOD mice had more anti-inflammatory macrophages in the liver than TSNO mice under ND feeding, and were impaired in the iHFC diet-induced accumulation of fibrosis-associated macrophages and formation of histological hepatic crown-like structures in the liver. The gut microbiota of TSOD mice also exhibited a distinct community composition with lower diversity and higher abundance of Akkermansia muciniphila compared with that in TSNO mice. Finally, TSOD mice had lower levels of bile acids linked to intestinal barrier disruption under iHFC feeding.

CONCLUSIONS

The dynamics of liver macrophage subsets, and the compositions of the gut microbiota and bile acids at steady state and post-onset of MASH, had major impacts on MASH development.

Emerging Insights into the Role of BDNF on Health and Disease in Periphery

Brain-derived neurotrophic factor (BDNF) is a growth factor that promotes the survival and growth of developing neurons. It also enhances circuit formation to synaptic transmission for mature neurons in the brain. However, reduced BDNF expression and single nucleotide polymorphisms (SNP) are reported to be associated with functional deficit and disease development in the brain, suggesting that BDNF is a crucial molecule for brain health. Interestingly, BDNF is also expressed in the hypothalamus in appetite and energy metabolism. Previous reports demonstrated that BDNF knockout mice exhibited overeating and obesity phenotypes remarkably. Therefore, we could raise a hypothesis that the loss of function of BDNF may be associated with metabolic syndrome and peripheral diseases. In this review, we describe our recent finding that BDNF knockout mice develop metabolic dysfunction-associated steatohepatitis and recent reports demonstrating the role of one of the BDNF receptors, TrkB-T1, in some peripheral organ functions and diseases, and would provide an insight into the role of BDNF beyond the brain.