Analysis of amino acid profiles of blood over time and biomarkers associated with non-alcoholic steatohepatitis in STAM mice.

Ayaka Iida,Ryoko Yamamoto,Koichi Tsuneyama,Masanori Ohta,Tsuyoshi Nakamura,Sachi Kuranuki,Takayuki Masaki,Mayuko Ichimura,Masaya Uchida,Masataka Seike

doi:10.1538/expanim.18-0152

Abstract

The changes in free amino acid (AA) levels in blood during the progression from non-alcoholic steatohepatitis (NASH) to hepatocellular carcinoma (HCC) are unclear. We investigated serum AA levels, along with biochemical and histological events, in a mouse model of NASH. We induced NASH in male C57BL/6J mice with a streptozotocin injection and high-fat diet after 4 weeks of age (STAM group). We chronologically (6, 8, 10, 12, and 16 weeks, n=4–12 mice/group) evaluated the progression from steatohepatitis to HCC by biochemical and histological analyses. The serum AA levels were determined using an AA analyzer. Serum aspartate aminotransferase and alanine aminotransferase levels were higher in the STAM group than in the normal group (non-NASH-induced mice). Histological analysis revealed that STAM mice had fatty liver, NASH, and fibrosis at 6, 8, and 10 weeks, respectively. Moreover, the mice exhibited fibrosis and HCC at 16 weeks. The serum branched-chain AA levels were higher in the STAM group than in the normal group, especially at 8 and 10 weeks. The Fischer ratio decreased at 16 weeks in the STAM group, with increasing aromatic AA levels. These results suggested that this model sequentially depicts the development of fatty liver, NASH, cirrhosis, HCC, and AA metabolism disorders within a short experimental period. Additionally, serum amyloid A was suggested to be a useful inflammation biomarker associated with NASH. We believe that the STAM model will be useful for studying AA metabolism and/or pharmacological effects in NASH.

Highlights

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease that is strongly associated with obesity and disorders of carbohydrate metabolism [11, 13]
NAFLD is considered a comorbidity of the metabolic syndrome [20], and its types range from non-alcoholic fatty liver to non-alcoholic steatohepatitis (NASH) with progressive fibrosis without alcohol abuse [3, 33]
We clarified the changes in free amino acid levels in blood over time during the progression from NASH to hepatocellular carcinoma (HCC) in mice

Summary

Introduction

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease that is strongly associated with obesity and disorders of carbohydrate metabolism [11, 13]. Among the different types of NAFLD, NASH sometimes progresses to liver diseases with a poor prognosis, including cirrhosis and hepatocellular carcinoma (HCC) [4]. Liver diseases, such as cirrhosis and HCC, generally decrease branched-chain amino acid (BCAA) levels in the blood. A recent study reported that free amino acid levels in the blood of patients with obesity and NASH change with increasing levels of BCAA [14].

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Results

Conclusion