The metabolic syndrome as a predictor of nonalcoholic fatty liver disease

The Role of the Gut Microbiome and its Derived Mediators in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has become an emerging disease throughout the world. Metabolic comorbidities such as obesity (especially central obesity), diabetes, and dyslipidaemia have been established as risk factors not only for NAFLD development, but also for the disease progression. Dietary or genetic obesity has been hypothesised to induce alteration of gut microbiota, thereby causing the promotion of deoxycholic acid production in the intestinal tract. Elevated levels of deoxycholic acid can provoke senescence-associated secretory phenotype in hepatic stellate cells through enterohepatic circulation, which in turn leads to the secretion of various inflammatory and tumour-promoting factors in the liver and may further result in obesity-induced hepatocellular carcinoma. Short-chain fatty acids are mainly produced through the fermentation of indigestible carbohydrates by gut microbiota. Gut microbiota have been considered to play a role in NAFLD and its disease progression. The main end products resulting from the indigestible carbohydrate catabolism of intestinal microbes are short-chain fatty acids, constituting acetate, propionate, and butyrate. High concentrations of propionate can promote development of NAFLD, whereas acetate and butyrate can prevent the development of the disease.

Nonalcoholic fatty liver disease: An overview of current insights in pathogenesis, diagnosis and treatment

Estimates of people suffering from overweight (one billion) and obesity (300 million) are increasing. The accumulation of triglycerides in the liver, in the absence of excess alcohol intake, has been described in the early sixties. It was not until 1980, however, that Ludwig et al named this condition nonalcoholic steatohepatitis (NASH). Subsequently, nonalcoholic fatty liver disease (NAFLD) has been used as a general name for conditions ranging from simple steatosis through steatohepatitis to end-stage liver disease (cirrhosis). Many studies have demonstrated the significant correlation with obesity and insulin resistance. Other studies have revealed a significant correlation between hepatic steatosis, cardiovascular disease and increased intima-media thickness. WHO estimated that at least two million patients will develop cirrhosis due to hepatic steatosis in the years to come. Longitudinal cohort studies have demonstrated that those patients with cirrhosis have a similar risk to develop hepatocellular carcinoma as those with other causes of cirrhosis. Taken all together, NAFLD has become the third most important indication for liver transplantation. Therefore, training programmes in internal medicine, gastroenterology and hepatology should stress the importance of diagnosing this entity and treat properly those at risk for developing complications of portal hypertension and concomittant cardiovascular disease. This review will focus on the clinical characteristics, pathophysiology, imaging techniques and the readily available therapeutic options.