How Obesity Affects Your LiverThursday, November 4, 2010
The term non-alcoholic fatty liver disease (NAFLD) is now widely used to describe hepatic steatosis resulting from excess weight in the absence of a history of significant alcohol use or other known liver diseases.
Already NAFLD is one of the most common liver disease worldwide with approximately 30% of the population affected in industrialized, western countries.
But how exactly does excess weight lead to a fatty liver and how damaging is this effect on liver function?
This is the subject of a comprehensive review by Alexander Wree and colleagues from the University of Duisburg-Essen, Germany, published in the latest issue of DIGESTION.
As the authors point out, visceral adipose tissue secretes free fatty acids (FFAs) and hormones (adipokines) that appear to play a major role in the development of NAFLD. Toxic FFAs can activate the intrinsic apoptosis pathway in hepatocytes (via c-Jun N-terminal kinase_mediated Bax activation) in a process known as ‘lipoapoptosis’. Not surprisingly, apoptotic cell death is a prominent feature in the progression of NAFLD to nonalcoholic steatohepatitis (NASH).
In addition, reduced adiponectin levels commonly associated with obesity may establish a proinflammatory milieu, thus increasing vulnerability to lipotoxicity, which promotes progression from simple steatosis to NASH and even advanced hepatic fibrosis.
Interestingly, obesity also appears to be a significant and independent risk factor for hepatocellular carcinoma, the most frequent type of liver cancer.
There is also data to suggest that excess body weight can adversely affect the progression of chronic hepatitis C and B.
Fortunately, NAFLD is a treatable condition, which responds (often dramatically) to weight loss interventions.
Thus, some readers may be aware that many bariatric surgeons now routinely recommend two weeks of weight loss prior to laparoscopic surgery, as this has been shown to dramatically reduce liver size and improve visibility during the surgical procedure.
As for so many other obesity related conditions, preventing and treating obesity will be a key measure in preventing and controlling this epidemic of fatty liver disease.
Wree A, Kahraman A, Gerken G, & Canbay A (2010). Obesity Affects the Liver – The Link between Adipocytes and Hepatocytes. Digestion, 83 (1-2), 124-133 PMID: 21042023