Hyperglycemia induces key genetic and phenotypic changes in human liver epithelial HepG2 cells which parallel the Leprdb/J mouse model of non-alcoholic fatty liver disease (NAFLD)

Abstract

Non-alcoholic fatty liver disease (NAFLD) is a growing global health concern. With a propensity to progress towards non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma, NAFLD is an important link amongst a multitude of comorbidities including obesity, diabetes, and cardiovascular and kidney disease. As several in vivo models of hyperglycemia and NAFLD are employed to investigate the pathophysiology of this disease process, we aimed to characterize an in vitro model of hyperglycemia that was amenable to address molecular mechanisms and therapeutic targets at the cellular level. Utilizing hyperglycemic cell culturing conditions, we induced steatosis within a human hepatocyte cell line (HepG2 cells), as confirmed by electron microscopy. The deposition and accumulation of lipids within hyperglycemic HepG2 cells is significantly greater than in normoglycemic cells, as visualized and quantified by Nile red staining. Alanine aminotransferase (ALT) and alkaline phosphatase (ALP), diagnostic biomarkers for liver damage and disease, were found to be upregulated in hyperglycemic HepG2 cells as compared with normoglycemic cells. Suppression of CEACAM1, GLUT2, and PON1, and elevation of CD36, PCK1, and G6PK were also found to be characteristic in hyperglycemic HepG2 cells compared with normoglycemic cells, suggesting insulin resistance and NAFLD. These in vitro findings mirror the characteristic genetic and phenotypic profile seen in Leprdb/J mice, a well-established in vivo model of NAFLD. In conclusion, we characterize an in vitro model displaying several key genetic and phenotypic characteristics in common with NAFLD that may assist future studies in addressing the molecular mechanisms and therapeutic targets to combat this disease.

CD40 Receptor Knockout Protects against Microcystin-LR (MC-LR) Prolongation and Exacerbation of Dextran Sulfate Sodium (DSS)-Induced Colitis

“…The effects of MC-LR also need to be better understood in the setting of pre-existing disease conditions. In fact, we have recently reported its severe toxicity in the liver at low, chronic doses in the setting of pre-existing non-alcoholic fatty liver disease (NAFLD) [21,22]. This has raised the concern that populations with pre-existing disease conditions should be urgently studied given their potentially increased susceptibility to MC-LR toxicity.…”

Complex Positive Effects of SGLT-2 Inhibitor Empagliflozin in the Liver, Kidney and Adipose Tissue of Hereditary Hypertriglyceridemic Rats: Possible Contribution of Attenuation of Cell Senescence and Oxidative Stress

“…Excessive lipid content in the liver, commonly referred to as non-alcoholic fatty liver disease (NAFLD), may further progress to non-alcoholic steatohepatitis (NASH), which is a more severe form of liver disease characterised by hepatocyte injury, inflammation, and fibrosis and by association with a higher risk of cardiovascular diseases [ 36 ]. There is evidence that HepG2 cells cultivated in hyperglycaemic media have elevated lipid content together with increased gene expression of key biomarkers of insulin resistance or NAFLD [ 37 ]. Reduction of intracellular lipid accumulation after empagliflozin treatment in our study suggests its protective effect on HepG2 cells.…”

TNAP: A New Multitask Enzyme in Energy Metabolism

“…Like in the intestinal lumen, another possible TNAP substrate in the liver is CD36. In HepG2 hepatocytes cultured in presence of high glucose or FA levels, TNAP expression increased in parallel with that of CD36 [ 71 , 72 ], and TNAP inhibition with levamisole or siRNA reduced triglyceride (TG) accumulation [ 71 , 73 ]. That TNAP controls CD36 activity in hepatocytes however remains to be demonstrated.…”

“…Since CD36 dephosphorylation facilitates FA uptake [ 44 , 45 , 46 ], if TNAP was responsible for dephosphorylating CD36, then its deficiency should lead to decreased, and not increased liver steatosis [ 14 ]. In fact, whether the function of TNAP in lipid accumulation in hepatocytes [ 71 , 72 ] relies on CD36 modulation remains obscure, because TNAP was reported to be located at the surface of lipid droplets [ 71 ], and thus not where CD36 is expected to be active. Finally, it is conceivable that TNAP indeed participates in CD36-associated FA uptake, but on other tissues than the liver, nevertheless impacting liver steatosis.…”