Semin Liver Dis 2008; 28(4): 370-379
DOI: 10.1055/s-0028-1091981
© Thieme Medical Publishers

Mechanisms of Disease Progression in Nonalcoholic Fatty Liver Disease

Janice Jou1 , Steve S. Choi1 , 2 , Anna Mae Diehl1
  • 1Division of Gastroenterology, Department of Medicine, Duke University Medical Center, Durham, North Carolina
  • 2Section of Gastroenterology, Department of Medicine, Durham Veteran Affairs Medical Center, Durham, North Carolina
Further Information

Publication History

Publication Date:
27 October 2008 (online)

ABSTRACT

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of hepatic pathology, ranging from simple steatosis (also called nonalcoholic fatty liver or NAFL) in its most benign form, to cirrhosis in its most advanced form. Nonalcoholic steatohepatitis (NASH) is an intermediate level of hepatic pathology. Hepatocyte accumulation of triglyceride is a hallmark of NAFL and NASH, but this sometimes subsides once cirrhosis has developed. Triglyceride storage per se is not hepatotoxic. Rather, it is a marker of increased exposure of hepatocytes to potentially toxic fatty acids. NAFL progresses to NASH when adaptive mechanisms that protect hepatocytes from fatty acid-mediated lipotoxicity become overwhelmed and rates of hepatocyte death begin to outstrip mechanisms that normally regenerate dead hepatocytes. This triggers repair responses that involve activation of hepatic stellate cells to myofibroblasts. The myofibroblasts generate excessive matrix and produce factors that stimulate expansion of liver progenitor populations. The progenitor cells produce chemokines to attract various kinds of inflammatory cells to the liver. They also differentiate to replace the dead hepatocytes. The intensity of these repair responses generally parallel the degree of hepatocyte death, resulting in variable distortion of the hepatic architecture with fibrosis, infiltrating immune cells, and regenerating epithelial nodules. As in other types of chronic liver injury, cirrhosis ensues in patients with NAFLD when repair is extreme and sustained, but ultimately unsuccessful, at reconstituting healthy hepatic epithelia.

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Anna Mae DiehlM.D. 

Division of Gastroenterology, Department of Medicine, Duke University Medical Center, Genome Sciences Research Building-1

595 LaSalle Street, Suite 1073, DUMC 3256, Durham, NC 27710

Email: annamae.diehl@duke.edu