AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis

Abstract

SignificanceLiver steatosis, or fatty liver, is the most common liver disease in the world, affecting up to 25% of all Americans. There is currently no approved drug available for this condition, which may progress to serious disease, including steatohepatitis, fibrosis, and cirrhosis. Here, we show in rodent and human models of metabolic syndrome that steatosis can be prevented by a simple dietary approach. Inorganic nitrate, present in green leafy vegetables, is converted in vivo to nitric oxide (NO) in a process involving symbiotic host bacteria. NO then induces key metabolic regulatory pathways to ultimately reduce oxidative stress and improve cardiometabolic functions. Clinical trials would be helpful to tell if dietary nitrate is useful in treatment and prevention of fatty liver disease.

3D Primary Hepatocyte Culture Systems for Analyses of Liver Diseases, Drug Metabolism, and Toxicity: Emerging Culture Paradigms and Applications

“…All scale bars = 100 μm. Reproduced with permission . Copyright 2016, American Society for Clinical Investigation.…”

“…A reduction in the hepatocellular lipid content was observed by treatment with various antisteatotic agents, such as metformin and the antioxidant vitamin E, indicating a reversal of hepatic steatosis. PHH spheroids were also recently used to interrogate the protective role of nitrite in reducing chemically and metabolically induced steatosis . Moreover, spheroid cultures were used to reveal the critical role of insulin‐like growth factor binding protein 7, a factor secreted by liver macrophages that binds to the hepatocyte insulin receptor and induces lipogenesis and gluconeogenesis, thus revealing how macrophages contribute to insulin resistance independent of inflammation …”

Human Liver Spheroids as a Model to Study Aetiology and Treatment of Hepatic Fibrosis

“…Advances in tissue engineering support increased cellular longevity in vitro, which is achieved by a three-dimensional (3D) spatial arrangement of cells, and where applied to liver tissue, demonstrate improved hepatocyte viability and functionality [15][16][17]. Primary human hepatocytes (PHH) cultured as 3D spheroids maintain tissue-like architecture, cell-cell interactions, and hepatocyte phenotype [18,19], and have therefore successfully been used to model hepatotoxicity [20][21][22], cholestasis [23], steatosis and insulin resistance [24,25], as well as the impact of genetic variants on lipid biosynthesis [26]. Historically, in vitro liver cultures lacked hetero-cellular interactions, however, co-cultures improve hepatocyte functionality and allow the study of PHH-NPC interactions [27][28][29].…”

A Human Liver‐on‐a‐Chip Platform for Modeling Nonalcoholic Fatty Liver Disease

“…Their chip consisted of a cord of hepatocytes cultured in a grid of closely spaced and parallel microchannels mimicking the endothelial–parenchymal interface of a liver sinusoid, but actual endothelial cells were not employed to build the system. Other studies by Kozyra et al and Cordero‐Herrera et al reported a human hepatic 3D spheroid system using primary human hepatocytes (PHHs) capable of mimicking steatosis conditions in a reversible manner and to prevent steatosis by a simple dietary approach, respectively . In addition, Kostrzewski et al developed a 3D perfused platform using PHHs for steatosis evaluation involving 12 isolated bioreactors where each one has its own flow rate generating an oxygen gradient across the tissue reproducing the in vivo liver sinusoid zonation .…”