Underrated enemy - from nonalcoholic fatty liver disease to cancers of the gastrointestinal tract

Abstract

Nonalcoholic fatty liver disease (NAFLD) is intrahepatic ectopic lipid deposition which is present despite a lack of other causes of secondary hepatic fat accumulation. It is the most common chronic liver disorder in the welldeveloped countries. NAFLD is a multidisciplinary disease that affects various systems and organs and is inextricably linked to simple obesity, metabolic syndrome, insulin resistance and overt diabetes mellitus type 2. The positive energy balance related to obesity leads to a variety of systemic changes including modified levels of insulin, insulin- like growth factor-1, adipokines, hepatokines and cytokines. It is strongly linked to carcinogenesis and new evidence proves that NAFLD is associated with higher risk of all-cause mortality and cancer-specific mortality among cancer survivors. This article focuses on the association between NAFLD and extrahepatic gastrointestinal tract cancers, aiming to shed light on the pathomechanism of changes leading to the development of tumors.

Keywords: NAFLD; adipokines; carcinogenesis; insulin resistance; obesity.

Fig. 1

Association between non-alcoholic fatty liver diseases and the mechanism of carcinogenesis

Fig. 2

Effect of changes in adipokines concentration in NAFLD on mechanisms involved in the carcinogenesis. In NAFLD serum levels of leptin, resistin, chemerin and visfatin are elevated, which stimulate pathways leading to tumour development. On the contrary, the level of adiponectin, which is responsible for downregulating cancerogenesis-promoting pathways, is decreased