Protocol for the Assessment of Variability in Histology and Gene Expression in Bariatric Surgery Patients.

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of abnormal liver tests in the United States. NAFLD is often found in association with obesity and diabetes and it is expected to become increasingly prevalent as the incidence of diabetes and obesity continues to increase. NAFLD represents a range of diseases from simple fatty deposition in the liver to more aggressive inflammation and fibrosis, termed nonalcoholic steatohepatitis (NASH). The distinction of NASH as an entity within NAFLD is an important one, as the natural history of this disease is different. Ultimately, NASH may progress to cirrhosis in up to 25% of patients, compared to simple steatosis which is a benign condition.

NAFLD has been estimated at 10-24% in various populations and is significantly higher in obese populations (57.5-74%). NASH is a subset of NAFLD characterized by fatty change with lobular inflammation, hepatocellular injury, progressive fibrosis and cirrhosis. The bariatric surgery population is an ideal cohort to study a large subset of NASH; those with morbid obesity.

The purpose of this study is to examine variability of hepatic histology as well as expression of key metabolic genes in NAFLD/NASH patients undergoing bariatric surgery. Patients will undergo pre-operative laboratory testing, followed by intra-operative liver and fat biopsies. A 12-month follow up will consist of repeat liver biopsy and laboratory testing. We predict that histologic variability of inflammation and fibrosis in NASH is accompanied by differential gene expression. Furthermore, if this variability is pronounced, this will temper the reliance on percutaneous liver biopsy in NASH as the "gold standard" and further emphasize the need for global markers of disease progression.