The cellular pathways of liver fibrosis in non-alcoholic steatohepatitis.

Non-alcoholic steatohepatitis (NASH) is considered the advanced stage of non-alcoholic fatty liver disease (NAFLD). It is characterized by liver steatosis, inflammation and different degrees of fibrosis. Although the exact mechanisms by which fatty liver progresses to NASH are still not well understood, innate and adaptive immune responses seem to be essential key regulators in the establishment, progression, and chronicity of these disease. Diet-induced lipid overload of parenchymal and non-parenchymal liver cells is considered the first step for the development of fatty liver with the consequent organelle dysfunction, cellular stress and liver injury. These will generate the production of pro-inflammatory cytokines, chemokines and damage-associated molecular patterns (DAMPs) that will upregulate the activation of Kupffer cells (KCs) and monocyte-derived macrophages (MMs) favoring the polarization of the tolerogenic environment of the liver to an immunogenic phenotype with the resulting transdifferentiation of hepatic stellate cells (HSCs) into myofibroblasts developing fibrosis. In the long run, dendritic cells (DCs) will activate CD4+ T cells polarizing into the pro-inflammatory lymphocytes Th1 and Th17 worsening the liver damage and inflammation. Therefore, the objective of this review is to discuss in a systematic way the mechanisms known so far of the immune and non-proper immune liver cells in the development and progression of NASH.

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis in HIV infection: a metabolic approach of an infectious disease.

INTRODUCTION: With the successes of antiretroviral therapy, patients infected with human immunodeficiency virus (HIV) living longer. Regarding this, the common diseases of HIV population (i.e., opportunistic infections) are now losing ground in front of metabolic alterations. This phenomenon is related to the delay in progression to acquired immune deficiency syndrome (AIDS), making it so that patients live in a chronic inflammatory state which, combined with other mechanisms such infectious ones, cause metabolic diseases. Areas covered: Considering a high prevalence of metabolic alterations, the relationship between metabolic syndrome (MetS) with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and liver diseases as a major cause of death in the HIV-infected population, this paper aims to overview the mechanisms and prevalence of NAFLD and NASH as they relate to the developed metabolic diseases of HIV patients. Expert opinion: The pathways underlying MetS include the effects of HIV and ART on the liver, adipose tissue, and muscle. These mechanisms result in liver damage, consequently leading to NAFLD and its more severe form NASH. These conditions have increased in HIV-infected population in recent years and since their life expectancy is improving it is important to be ready to attend their new emerging diseases.