Dietary supplementation with branched‐chain amino acids suppresses diethylnitrosamine‐induced liver tumorigenesis in obese and diabetic C57BL/KsJ‐db/db mice

Abstract

Obesity and related metabolic abnormalities, including insulin resistance, are risk factors for hepatocellular carcinoma in non-alcoholic steatohepatitis as well as in chronic viral hepatitis. Branched-chain amino acids (BCAA), which improve insulin resistance, inhibited obesity-related colon carcinogenesis in a rodent model, and also reduced the incidence of hepatocellular carcinoma in obese patients with liver cirrhosis. In the present study, we determined the effects of BCAA on the development of diethylnitrosamine (DEN)-induced liver tumorigenesis in obese C57BL ⁄ KsJ-db ⁄ db (db ⁄ db) mice with diabetes mellitus. Male db ⁄ db mice were given tap water containing 40 ppm DEN for an initial 2 weeks and thereafter they received a basal diet containing 3.0% of BCAA or casein, which served as a nitrogen content-matched control of BCAA, throughout the experiment. Supplementation with BCAA significantly reduced the total number of foci of cellular alteration, a premalignant lesion of the liver, and the expression of insulin-like growth factor (IGF)-1, IGF-2, and IGF-1 receptor in the liver when compared to the casein supplementation. BCAA supplementation for 34 weeks also significantly inhibited both the development of hepatocellular neoplasms and the proliferation of hepatocytes in comparison to the basal diet or casein-fed groups. Supplementation with BCAA improved liver steatosis and fibrosis and inhibited the expression of a-smooth muscle actin in the DEN-treated db ⁄ db mice. The serum levels of glucose and leptin decreased by dietary BCAA, whereas the value of the quantitative insulin sensitivity check index increased by this agent, indicating the improvement of insulin resistance and hyperleptinemia. In conclusion, oral BCAA supplementation improves insulin resistance and prevents the development of liver tumorigenesis in obese and diabetic mice. (Cancer Sci 2010; 101: 460-467) H epatocellular carcinoma is a major health problem worldwide. The development of HCC is frequently associated with chronic inflammation of the liver induced by a persistent infection with the hepatitis B virus or hepatitis C virus.(1) The risk of HCC is also elevated in those with metabolic syndrome, also called insulin resistance syndrome, which is commonly associated with obesity and impaired glucose tolerance.(1-4) Non-alcoholic fatty liver disease is known to be a hepatic manifestation of the metabolic syndrome. Diabetes mellitus, a condition associated with hyperinsulinemia, has been proposed as a risk factor for both chronic liver disease and HCC through the development of NASH, which is observed in a subset of patients with non-alcoholic fatty liver disease and involves inflammation, cell damage, and ⁄ or fibrosis in the liver.(5-7) In 1998, Day and James proposed, in their ''two hit theory,'' that insulin resistance is regarded as a critical factor in the etiology of NASH. (8) C57BL ⁄ KsJ-db ⁄ db (db ⁄ db) mice are a genetically altered animal model with phenotypes of obesity and diabetes mellitus. A functional defect in t...

Acyclic Retinoid Inhibits Diethylnitrosamine-Induced Liver Tumorigenesis in Obese and Diabetic C57BLKS/J- +Leprdb/+Leprdb Mice

“…Recent evidence also indicates that obesity and the related metabolic abnormalities, especially diabetes mellitus, increase the risk of HCC (1)(2)(3). In a rodent model, the occurrence of diethylnitrosamine (DEN)-induced liver tumorigenesis was found to be significantly higher in obese and diabetic C57BLKS/JþLepr db /þLepr db (db/db) mice than in genetic control mice (4). Diabetes mellitus has been shown to increase the risk of primary HCC in patients with viral hepatitis (5).…”

“…Before sacrifice, the mice were fasted for 6 hours, and at sacrifice, blood samples were collected for assaying the serum concentrations of insulin, glucose, and TNF-a, which was as described previously (4,29). The serum TNF-a (Shibayagi) levels were determined using an enzyme immunoassay according to the manufacturer's protocol.…”

“…cDNA was amplified from 0.2 mg of total RNA by using the SuperScript III FirstStrand Synthesis System (Invitrogen), and quantitative real-time reverse transcription PCR (RT-PCR) analysis was carried out as described previously (4). The specific primers used for amplification of the TNF-a, IL-6, IL-1b, and b-actin genes were as described previously (30).…”

Long-term Branched Chain Amino Acid Supplementation Ameliorates Diethylnitrosamine-induced Liver Glutathione S-transferase-p Positivity in Zucker Fatty Rats

“…Previous DEN-induced hepatocarcinogenesis obese animal models require more time for tumor development and the incidence of HCC is lower. For example, less than 27% of DEN-treated db/db mice developed HCC by 34 weeks, 15 and 33% of DEN-treated Fatty liver Shionogi (FLS) mice developed HCC by 26 weeks. 16 Leptin receptor-mediated signaling is important to hepatic fibrosis.…”

“…21,22 Furthermore, long-term oral supplementation with BCAA granules inhibits liver carcinogenesis in overweight and obese patients with liver cirrhosis. 9 Long-term administration of BCAA improves insulin resistance 15 and inhibits VEGF production, 23 which may therefore inhibit carcinogenesis.…”