Nonalcoholic fatty liver disease (NAFLD) is the overarching term for a series of complex diseases caused by an accumulation of fat in the liver. The liver is an essential organ in the body which carries out many metabolic functions and also removes toxins from the blood. Persistently increased levels of fat in the liver lead to inflammation of the liver and ultimately liver damage and cirrhosis. Cirrhosis is irreversible scarring of the liver which leads to decreased liver function. Cirrhosis was historically known to be caused by alcohol abuse, but with the emergence of obesity as an epidemic concern, fat accumulation in the liver became a new known causative agent of liver cirrhosis.
A rise in the prevalence of NAFLD has paralleled the rise in obesity over the last few decades. In developed countries, NAFLD has been reported in 20-35% of adults in the general population and 70-90% in obese populations (Black et al. 2014). In America’s pediatric population, 35% of children are categorized as overweight or obese, and about 10-25% of these children have been diagnosed with NAFLD (Della Corte et al. 2012). The disease is difficult to diagnose because in the early stages, people do not usually present with any symptoms (Della Corte et al. 2012). Yet, if left uncontrolled, NAFLD can progress to liver cirrhosis which can only be treated by liver transplantation.
The cause of increased fat accumulation in the liver and progression of NAFLD are multifactorial. There are several hypotheses surrounding increased fat accumulation in hepatocytes (liver cells), but the primary ones focus on increased dietary intake of glucose and fructose which then stimulates the production of fat in hepatocytes by upregulating enzymes that catalyze lipogenesis (Cohen et al. 2011). The progression of NAFLD to more severe forms like nonalcoholic steatohepatitis and cirrhosis has been attributed to increased cytokine levels which lead to an inflammatory state in the liver (Cohen et al. 2011).
At this point, treatments for NAFLD are limited. One option to treat NAFLD is exercise and healthy eating, thereby reducing levels of fat in the body and the liver. Scientists are also trying to discover safe drugs which will act on some of the enzymes that lead to increased production of fat in liver cells in order to combat NAFLD. One recently discovered drug, ursolic acid, is present in the peels of apples. Ursolic acid administration decreases the production of fat and increases the breakdown of fat in the livers of mice and is soon to be investigated in humans (Li et al., 2014). Since drug therapies are limited, it is crucial that individuals take care of their liver by eating well-balanced meals and exercising regularly.
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