Development of the Rabbit NASH Model Resembling Human NASH and Atherosclerosis.

Non-alcoholic steatohepatitis (NASH) is a chronic liver disease which may progress into liver fibrosis and cancer. Since NASH patients have a high prevalence of atherosclerosis and ensuing cardiovascular diseases, simultaneous management of NASH and atherosclerosis is required. Currently, rodents are the most common animal models for NASH and accompanying liver fibrosis, but there are great differences in lipoprotein profiles between rodents and humans, which makes it difficult to reproduce the pathology of NASH patients with atherosclerosis. Rabbits can be a promising candidate for assessing NASH and atherosclerosis because lipoprotein metabolism is more similar to humans compared with rodents. To develop the NASH model using rabbits, we treated the Japanese White rabbit with a newly developed high-fat high-cholesterol diet (HFHCD) containing palm oil 7.5%, cholesterol 0.5%, and ferrous citrate 0.5% for 16 weeks. HFHCD-fed rabbits exhibited NASH at 8 weeks after commencing the treatment and developed advanced fibrosis by the 14th week of treatment. In addition to hypercholesterolemia, atherosclerotic lesion developed in the aorta after 8 weeks. Therefore, this rabbit NASH model might contribute to exploring the concurrent treatment options for human NASH and atherosclerosis.

Vitamin K deficiency of germfree mice caused by feeding standard purified diet sterilized by gamma-irradiation.

Germfree mice died when they were fed a purified diet of AIN-76 formula sterilized by gamma-irradiation. Vitamin K deficiency was suspected and this study was performed to confirm the cause of the death. Germfree mice were fed purified diets of AIN-76 or AIN-93M formula, which were pelleted and sterilized by gamma-irradiation at a dose of 50 kGy. One half of the mice fed the AIN-76 diet died within two weeks and the surviving animals were also in poor health, while 91% of mice fed the AIN-93M diet survived. No hemorrhage was observed grossly in any organs of the surviving animals. Histologically, degeneration with inflammatory cell infiltration was observed as well as hemorrhage and fibrosis in the heart muscles of mice fed the AIN-76 diet. No microscopic lesions were observed in the other organs. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were extremely prolonged when mice were fed the AIN-76 diet. The animals totally recovered when they were intragastrically administered 1 microg/day of vitamin K(3) from the third day of feeding of the AIN-76 diet, except for PT and APTT which were still slightly longer than in mice fed the AIN-93M diet. The concentration of vitamin K(3) supplied in the AIN-76 diet decreased to an undetectable level after gamma-irradiation, while the AIN-93M diet contained 240 microg/kg of vitamin K(1). These results indicate that the deaths of the germfree mice fed the gamma-irradiated AIN-76 diet were caused by vitamin K deficiency. Vitamin K deficiency may cause fatal degeneration of cardiac muscle cells.

Electron-beam sterilization of laboratory animal diets--sterilizing effect of 10-MeV electrons from a linear accelerator.

Electron beam sterilization for laboratory animal diets was examined as an alternative to 60Co gamma rays. Solid, powder diets for "mice and rats" and solid diets for "rabbits and guinea pigs" which are the main products sterilized by 60Co gamma rays were irradiated with 10-MeV electrons from a linear accelerator at the Research Institute for Advanced Science and Technology, Osaka Prefecture University. At least 20 kGy was required to sterilize the samples irrespective of solid or powder diets, which was in good accordance with the results for 60Co gamma rays. Using a set dose of 30 kGy, a thickness of 45 mm for solid diets and 30 mm for powder diets could be sterilized by "one-sided" irradiation. "Dual-sided" irradiation could sterilize all the solid diets and the powder diets contained in the thicknesses of 90 mm and 75 mm, respectively. Irradiation effects of 10-MeV electrons on the nutrient quality of each diet were almost equivalent to those of 60Co gamma rays. These results suggest that commercially adopted sterilization doses for 60Co gamma rays are applicable to electron sterilization without modification if the depth-dose profile and the minimum dose of irradiated samples are precisely assessed.