Non-alcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. One of the most common models used in NASH research is a nutritional model where NASH is induced by feeding a diet deficient in both methionine and choline. However, the dietary methionine-/choline-deficient model in mice can cause severe weight loss and liver atrophy, which are not characteristics of NASH seen in human patients. Exclusive, long-term feeding with a high-fat diet (HFD) produced fatty liver and obesity in mice, but the HFD for several months did not affect fibrosis. We aimed to establish a mouse model of NASH with fibrosis by optimizing the methionine content in the HFD. Male mice were fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) consisting of 60 kcal% fat and 0.1% methionine by weight. After 1–14 weeks of being fed CDAHFD, the mice were killed. C57BL/6J mice maintained or gained weight when fed CDAHFD, while A/J mice showed a steady decline in body weight (of up to 20% of initial weight). In both strains of mice, plasma levels of alanine aminotransferase increased from week 1, when hepatic steatosis was also observed. By week 6, C57BL/6J mice had developed enlarged fatty liver with fibrosis as assessed by Masson's trichrome staining and by hydroxyproline assay. Therefore, this improved CDAHFD model may be a mouse model of rapidly progressive liver fibrosis and be potentially useful for better understanding human NASH disease and in the development of efficient therapies for this condition.

Most acute hepatitis C virus (HCV) infections become chronic and some progress to liver cirrhosis or hepatocellular carcinoma. Standard therapy involves an interferon (IFN)-α-based regimen, and efficacy of therapy has been significantly improved by the development of protease inhibitors. However, several issues remain concerning the injectable form and the side effects of IFN. Here, we report an orally available, small-molecule type I IFN receptor agonist that directly transduces the IFN signal cascade and stimulates antiviral gene expression. Like type I IFN, the small-molecule compound induces IFN-stimulated gene (ISG) expression for antiviral activity in vitro and in vivo in mice, and the ISG induction mechanism is attributed to a direct interaction between the compound and IFN-α receptor 2, a key molecule of IFN-signaling on the cell surface. Our study highlights the importance of an orally active IFN-like agent, both as a therapy for antiviral infections and as a potential IFN substitute.

The SMXA-5 recombinant inbred strain, which was established from nondiabetic parental SM/J and A/J mice, develops diabetic phenotypes such as impaired glucose tolerance. The combination of diabetogenic genes in the SM/J and A/J genomes impairs glucose tolerance in SMXA-5 mice. Using (SM/J x SMXA-5)F2 mice fed a high-fat diet, we previously detected a diabetogenic locus, T2dm2sa, on chromosome (Chr) 2. The A/J allele at this locus is diabetogenic. The SM.A-T2dm2sa congenic mouse, in which the Chr 2 region of A/J including T2dm2sa was introgressed into SM/J, showed obviously impaired glucose tolerance. These results indicate that SM.A-T2dm2sa mice develop diabetogenic traits due to T2dm2sa with the A/J allele and unknown diabetogenic loci with the SM/J allele. The aim of this study was to dissect these unknown loci, using quantitative trait locus (QTL) analysis in the (A/J x SM.A-T2dm2sa) F2 intercross fed a high-fat diet. The results revealed a highly significant QTL, T2dm4sa, for glucose tolerance on Chr 6 and a significant QTL, T2dm5sa, for glucose tolerance on Chr 11. These loci with the SM/J allele were diabetogenic. The diabetogenic effect of T2dm4sa or T2dm5sa was verified by the impairment of glucose tolerance in the A/J-6(SM) or A/J-11(SM) consomic strain, in which Chr 6 or Chr 11 of SM/J is introgressed into A/J, respectively. These results demonstrate that diabetogenic loci exist in the genomes of nondiabetic A/J and SM/J mice and suggest that T2dm2sa with the A/J allele and T2dm4sa and/or T2dm5sa with the SM/J allele elicit impaired glucose tolerance in SM.A-T2dm2sa mice.

abdominal fat but not of subcutaneous fat might be linked to the development of these metabolic complications (3)(4)(5). Moreover, each abdominal fat depot, such as mesenteric or epididymal, is thought to contribute differently to the development of insulin resistance ( 6 ). Metabolic complications such as obesity, insulin resistance, and type 2 diabetes are complex traits controlled by multiple genes and environmental factors. To search for obesity genes, numerous quantitative trait locus (QTL) analyses have been performed using mice, starting in 1993 by . In 2002, Brockmann et al. ( 8 ) reviewed 166 QTLs for obesity, that is body weight and body fat weight, from 24 studies. Wuschke et al. ( 9 ) performed a metaanalysis of 279 QTLs for body weight and body fat weight using 34 published mouse experiments. Recently, some groups reported the analysis of relation between QTLs for body fat distribution and QTLs for traits of obesity-related diseases using mouse models ( 10-14 ). Although the association of diabetes with obesity is suggested in various animal models of type 2 diabetes, a few reports have focused on the simultaneous analyses of QTLs for type 2 diabetes and fat distribution. The genetic basis and mechanisms linking fat distribution to these metabolic complications remain poorly understood.SXMA recombinant-inbred (RI) strains are established from parental strains SM/J and A/J mice ( 15 ), and the genome of each SMXA RI strain consists of a mixture of the SM/J and A/J mouse genomes. The SMXA-5 mouse, which belongs to the 26 SMXA RI strains, has been shown to develop impaired glucose tolerance, fatty liver, and moderate obesity ( 16 ). The development of these metabolic complications in SMXA-5 mice are quite accelerated Abstract Each abdominal fat depot, such as mesenteric or epididymal, differently contributes to the development of insulin resistance. The aim of this study was to identify the genetic regions that contribute to fat accumulation in epididymal/mesenteric fat and to examine whether or not the genetic regions that affect glucose metabolism and body fat distribution are coincident. We previously mapped a major quantitative trait locus (QTL) ( T2dm2sa ) for impaired glucose tolerance on chromosome 2 and revealed that SM.AT2dm2sa congenic mice showed not only glucose tolerance but also fat accumulation. In the present study, to identify the loci/genes that control the accumulation of abdominal fat, we perfomed QTL analyses of epididymal/mesenteric fat weight by using (A/J×SM.A-T2dm2sa )F2 mice in which the effect of T2dm2sa was excluded. As a result, two highly signifi cant QTLs for mesenteric fat, as well as three significant QTLs for epididymal/mesenteric fat, were mapped on the different chromosomal regions. This suggests that the fat accumulations in individual fat depots are controlled by distinct genomic regions. In humans, obesity is a major risk factor for insulin resistance, type 2 diabetes, dyslipidemia, cardiovascular disease, fatty liver, and stroke ( 1, 2 ). The accumulation of

SummaryThe interaction between causative genes and diet is known to influence the onset of obesity and diabetes in humans, although it has remained difficult to identify diabetogenic gene(s) because humans are genetically and environmentally heterogeneous. Mouse SMXA recombinant inbred (RI) strains are established from parental inbred strains (SM/J and A/J) and have been shown to be beneficial tools for analyzing polygenic traits. We previously mapped a significant quantitative trait locus (QTL, T2dm1sa ) on Chromosome (Chr.) 10 and suggestive QTLs on Chr. 2, 6, and 18 for diabetes-related traits by using SMXA RI strains fed a high-carbohydrate diet. As a first step in identifying the responsible gene among QTLs for glucose tolerance mapped on Chr. 10 and 18, we established new strains of A.SM-T2dm1sa and SM.A-D18Mit19-D18Mit7 congenic mice. Each congenic strain bears the diabetogenic allele of an introgressed chromosomal region on a genetic background strain carrying the non-diabetogenic allele. The diabetogenic effect of T2dm1sa mapped on Chr. 10 was not supported by studies of A.SM-T2dm1sa congenic mice when the mice were fed a high-carbohydrate or high-fat diet. SM.A-D18Mit19-D18Mit7 congenic mice showed impaired glucose tolerance not only when they were fed a high-carbohydrate diet, but also when they were fed a high-fat diet. Thus, it appears that gene(s) affecting diabetes-related traits under either dietary condition may be present on Chr. 18. Key Words congenic, quantitative trait locus, high-fat diet, recombinant inbredThe prevalence of obesity and diabetes has increased worldwide ( 1 ). The interaction between genes and diet is known to exert an influence on the pathogenicity of obesity and diabetes in humans ( 2 -4 ). However, it should be noted that the increasing incidence of obesity and diabetes is not due to changes in genetic factors in populations, but rather to environmental factors such as changes in lifestyle (e.g., changes in diet and levels of activity) ( 5 ). A high percentage of dietary fat has been associated with the conversion of impaired glucose tolerance to overt type 2 diabetes in humans ( 6 , 7 ). Petro and co-workers ( 8 ) reported that a high percentage of dietary fat is a crucial stimulus for obesity and diabetes in C57BL/6 mice, a model for diet-induced diabetes and obesity. Using this mouse model, they demonstrated that dietary fat is a critical factor in the development and maintenance of obesity and type 2 diabetes. Therefore, it is of value to analyze diabetogenic gene(s) while considering dietary content such as fat intake. It is difficult to identify diabetogenic gene(s) in humans due to genetic heterogeneity, and dietary factors cannot be easily controlled. However, using inbred animal models, it becomes possible to strictly control genetic and environmental factors.Recombinant inbred strains are derived from two different parental inbred strains and are beneficial tools for analyzing polygenic traits. Mouse SMXA recombinant inbred (SMXA RI) strains have been establishe...