Objective: Nonalcoholic fatty liver disease (NAFLD) is linked to obesity and diabetes, suggesting an important role of adipose tissue in the pathogenesis of NAFLD. Here we aim to investigate the interaction between adipose tissue and liver in NAFLD, and identify potential early plasma markers that predict NASH. Research Design and Methods: C57Bl/6 mice were chronically fed a high fat diet to induce NAFLD and compared with mice fed low fat diet. Extensive histological and phenotypical analyses coupled with a time-course study of plasma proteins using multiplex assay was performed. Results: Mice exhibited pronounced heterogeneity in liver histological scoring, leading to classification into 4 subgroups: LF-low (LFL) responders displaying normal liver morphology, LF-high (LFH) responders showing benign hepatic steatosis, HF-low (HFL) responders displaying pre-NASH with macrovesicular lipid droplets, and HF-high (HFH) responders exhibiting overt NASH characterized by ballooning of hepatocytes, presence of Mallory bodies, and activated inflammatory cells. Compared to HFL responders, HFH mice gained weight more rapidly and exhibited adipose tissue dysfunction characterized by decreased final fat mass, enhanced macrophage infiltration and inflammation, and adipose tissue remodelling. Plasma haptoglobin, IL-1, TIMP-1, adiponectin and leptin were significantly changed in HFH mice. Multivariate analysis indicated that in addition to leptin, plasma CRP, haptoglobin, eotaxin and MIP-1 early in the intervention were positively associated with liver triglycerides. Intermediate prognostic markers of liver triglycerides included IL-18, IL-1, MIP-1 and MIP-2, whereas insulin, TIMP-1, GCP-2 and MPO emerged as late markers. Conclusions: Our data support the existence of a tight relationship between adipose tissue dysfunction and NASH pathogenesis and point to several novel potential predictive biomarkers for NASH.
Adipose tissue dysfunction signals progression of hepatic steatosis towards nonalcoholic steatohepatitis in C57BL/6 mice.
Specimen part
View SamplesWe studied the effect of dietary fat type, varying in polyunsaturated/saturated fatty acid ratio's (P/S) on development of metabolic syndrome. C57Bl/6J mice were fed purified high-fat diets (45E% fat) containing palm oil (HF-PO; P/S 0.4), olive oil (HF-OO; P/S 1.1) or safflower oil (HF-SO; P/S 7.8) for 8 weeks. A low-fat palm oil diet (LF-PO; 10E% fat) was used as a reference. Additionally, we analyzed diet-induced changes in gut microbiota composition and mucosal gene expression. The HF-PO diet induced a higher body weight gain and liver triglyceride content compared to the HF-OO, HF-SO or LF-PO diet. In the intestine, the HF-PO diet reduced microbial diversity and increased the Firmicutes/Bacteroidetes ratio. Although this fits a typical obesity profile, our data clearly indicate that an overflow of the HF-PO diet to the distal intestine, rather than obesity itself, is the main trigger for these gut microbiota changes. A HF-PO diet-induced elevation of lipid metabolism-related genes in the distal small intestine confirmed the overflow of palm oil to the distal intestine. Some of these lipid metabolism-related genes were previously already associated with the metabolic syndrome. In conclusion, our data indicate that saturated fat (HF-PO) has a more stimulatory effect on weight gain and hepatic lipid accumulation than unsaturated fat (HF-OO and HF-SO). The overflow of fat to the distal intestine on the HF-PO diet induced changes in gut microbiota composition and mucosal gene expression. We speculate that both are directly or indirectly contributive to the saturated fat-induced development of obesity and hepatic steatosis.
Saturated fat stimulates obesity and hepatic steatosis and affects gut microbiota composition by an enhanced overflow of dietary fat to the distal intestine.
Sex, Specimen part
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