Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis in Japan.

During the past 20 to 30 years, the frequency of patients presenting with nonalcoholic fatty liver diseases (NAFLD) has increased gradually in Japan in proportion to the increase in the population with life-style related diseases. We describe here the current status of the clinical and basic aspects of research into NAFLD in Japan. The increase in the incidence of life-style-related diseases has resulted in an increase in NAFLD throughout the past 20 to 30 years. The rate of obesity in the population is not high compared to western countries but the incidence of NAFLD is similar to those countries. In 2008 we started a nationwide study of NAFLD which has been supported by the Ministry of Labor and Welfare Japan. In this project, we planned to investigate the epidemiology, genetic backgrounds and biochemical markers, and liver injury in patients with diabetes mellitus (DM) and hepatocellular carcinoma in NASH, and treatment of NASH. Approximately 20 to 25% of DM patients showed NAFLD in which the prevalence of NASH might be more than 30 to 40%. Fortunately, we have been able to obtain very interesting results from our group studies, including single necleotide polymorphisms (SNPs) which will be published in the near future.