Dietary wheat amylase trypsin inhibitors worsen chronic liver disease in pre-clinical models of NASH and liver fibrosis

Background and aims:

Specific nutrient signals from the intestine may be important drivers of obesity and non-alcoholic fatty liver disease (NAFLD). A common dietary component, wheat amylase trypsin inhibitors (ATI), activate intestinal macrophages and dendritic cells via toll like receptor 4. We showed that upon activation by ATI, these cells migrate and propagate the inflammatory stimulus to the periphery. We therefore studied how far nutritional ATI would affect NAFLD and liver fibrosis in preclinical models of NASH and liver fibrosis.

Methods and Results:

Male C57BI/6J mice received a carbohydrate and protein (zein) defined low fat or high fat diet (HFD), with or without 30% of the protein being replaced by wheat gluten (G, naturally containing 0.15 g ATI per 10 g), or 0.7% of the zein as purified ATI for 8 weeks. Male Mdr2-knockout (Mdr2KO) mice were fed ATI enriched and ATI de-enriched diets for 6 weeks. At sacrifice blood, liver and peripheral adipose tissues were collected for biochemical, immunological and histological analysis. In the NASH model, insulin resistance (IR) was assessed by an intraperitoneal glucose tolerance test.

In NASH, mice on the HFD gained significant weight and developed IR. Compared to the HFD alone, mice fed the HFD/G/ATI or the HFD/ATI diets gained significantly more weight and displayed significantly higher serum transaminases and triglycerides, increased liver, epididymal, mesenteric and inguinal fat, and a higher insulin resistance. ATI feeding promoted liver and adipose tissue inflammation, M1 macrophage polarization and infiltration, and enhanced the fibrogenic response in the liver. In Mdr2KO mice, liver weight in the ATI fed group was significantly increased compared to the ATI free group. Overall, liver transcripts for col1a1, alpha-sma and col3a1 were significantly upregulated in the ATI fed vs. ATI-free groups. In line, Sirius red morphometry showed a higher collagen deposition in the ATI-fed mice.

Conclusion:

When ingested in quantities comparable to average human consumption, wheat ATI exacerbate the key features of rodent NAFLD and the metabolic syndrome despite their irrelevant caloric value. Moreover, dietary ATI promoted liver fibrosis in the NASH and the Mdr2KO mouse model of PSC.