Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease and it encompasses a spectrum from simple steatosis to steatohepatitis, fibrosis, or cirrhosis. The mechanisms involved in the occurrence of NAFLD and its progression are probably due to a metabolic profile expressed within the context of a genetic predisposition and is associated with a higher energy intake. The metabolic syndrome (MS) is a cluster of metabolic alterations associated with an increased risk for the development of cardiovascular diseases and diabetes. NAFLD patients have more than one feature of the MS, and now they are considered the hepatic components of the MS. Several scientific advances in understanding the association between NAFLD and MS have identified insulin resistance (IR) as the key aspect in the pathophysiology of both diseases. In the multi parallel hits theory of NAFLD pathogenesis, IR was described to be central in the predisposition of hepatocytes to be susceptible to other multiple pathogenetic factors. The recent knowledge gained from these advances can be applied clinically in the prevention and management of NAFLD and its associated metabolic changes. The present review analyses the current literature and highlights the new evidence on the metabolic aspects in the adult patients with NAFLD.

Hepatitis C virus (HCV) infection is a global health problem with 150 million infected people worldwide. Liver can be greatly affected by changes in gut microbiota due to increased intestinal permeability with passage of microbial antigens into the liver through the portal circulation. The concept of 'gut-liver' axis is important to understand the pathophysiology of several liver diseases. Several recent studies also revealed that an altered gut microbiota can be implicated in the pathogenesis of HCV-induced chronic liver disease (CHC). Areas covered: An overview of intestinal microflora composition, host reaction during CHC, and a description of relevant clinical trials on the use of probiotics in this field. Expert commentary: HCV patients gut microbiota composition is stable over liver disease stages. This is a unique example of gut disbiosis stability vs. NAFLD, HBV, HIV, and HCV co-infected patients. The impact of HCV infection on intestinal permeability allows gut disbiosis starting, maintenance and its proinflammatory effect until liver cirrhosis and HCC development. HCV eradication has unraveled the strong impact of gut microbiota unbalance on liver disease development with possible future implications for probiotics use to change the natural history of cirrhosis progression.

Bacterial infections are often found in patients with liver cirrhosis, the most frequent being pneumonia, urinary tract infection and spontaneous bacterial peritonitis. Gram negative bacteria, especially Escherichia coli were predominant in the etiology. The extent to which bacterial infections are taken into consideration in cases with liver cirrhosis is rather high; however, they are not proved etiologically to the satisfactory level.

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