Non-alcoholic steatohepatitis: what is it, and why is it important in the Asia-Pacific region?

Non-alcoholic steatohepatitis (NASH), is a critical link in the chain of metabolic fatty liver disorders that spans steatosis to cryptogenic cirrhosis. It is the hepatic manifestation of the insulin resistance (or metabolic) syndrome, and provides a clue to understanding fibrotic progression of other chronic liver diseases, particularly hepatitis C. Non-alcoholic steatohepatitis is often the first clinical indication of insulin resistance, with its complications of high blood pressure, coronary heart disease and type 2 diabetes. Among those with risk factors, NASH is common: present in at least 20% of obese adults or children with or without type 2 diabetes, and at least 5% of those overweight. With emerging urbanization, increasing affluence and behavioral changes of physical inactivity and high fat/energy-excessive diet, type 2 diabetes has become common in Asia and the western Pacific rim. The rates range from 7-40%, which in countries like Japan represents a 3-20-fold increase (depending on age) over the last 20 years. The increase is associated with central adiposity, insulin resistance, hepatic steatosis and NASH. After cancer, cirrhosis from NASH is now the second most common age-related cause of death in type 2 diabetes. Reversing these trends must become a public health priority; the first awakenings were evident in Taiwan at the time of this meeting. In order to stimulate clinicians to think more about the importance of metabolic liver disease for development of cirrhosis, this review will cover clinical and laboratory features, natural history and an approach to diagnosis and management of NASH. Some emerging concepts on pathogenesis will be mentioned briefly, but the emphasis will be on the potency of lifestyle adjustments (physical activity and diet) to prevent or reverse fatty liver disorders.