Oxidized low-density lipoprotein activates extracellular signal-regulated kinase signaling to downregulate sortilin expression in liver sinusoidal endothelial cells.

BACKGROUND AND AIM: Both type 2 diabetes mellitus and non-alcoholic fatty liver disease are closely associated with elevated levels of low-density lipoprotein cholesterol and its oxidized form (ox-LDL). This study aimed to investigate the regulation of sortilin in liver tissue and its potential implications for lipid metabolism. METHODS: Sixty male Wistar rats were randomly divided into four groups: control group (n = 15), ox-LDL group (n = 15), PD98059 group (n = 15), and ox-LDL + PD98059 group (n = 15). Liver sinusoidal endothelial cells were extracted from liver tissue of the control group and were identified using an anti-CD31 antibody. Lipid droplet accumulation was observed by Oil red O and hematoxylin-eosin staining. The protein expression levels were detected by immunohistochemical staining, real-time reverse transcription-polymerase chain reaction, and western blot. Histopathologic examinations were performed by Gomori methenamine silver staining. RESULTS: The ox-LDL group exhibited increased lipid droplet accumulation. Further, ox-LDL activated the extracellular signal-regulated kinase (ERK)-mediated downregulation of sortilin expression, whereas blocking of ERK signaling by PD98059 increased sortilin protein expression. Consistently, hematoxylin-eosin staining showed that the structure of the hepatocytes was loose and disordered in arrangement, with lipid droplets present in the cytoplasm of the ox-LDL group. However, PD98059 significantly improved the integration of the scaffold structure. Gomori methenamine silver staining showed that the ox-LDL group had darker and more obvious fragmented silver nitrate deposits in the basement membrane and sinus space. CONCLUSIONS: Sortilin can protect liver sinusoidal endothelial cells from injury and maintain integration of the liver scaffold structure in ox-LDL-induced lipid-injured liver.

CTRP13 attenuates the expression of LN and CAV-1 Induced by high glucose via CaMKKß/AMPK pathway in rLSECs.

OBJECTIVE: To investigate the effect and mechanism of CTRP13 on hepatic sinusoidal capillarization induced by high glucose in rat liver sinusoidal endothelial cells (rLSECs). RESULTS: CTRP13 was reduced in high glucose-treated rLSECs. High glucose increased LN and CAV-1 expression and inhibited CaMKKß and AMPK phosphorylation. CTRP13 overexpression protected rLSECs against high glucose-induced increase of LN and CAV-1 expression. Moreover, CTRP13 overexpression increased high glucose-induced inhibition of CaMKKß and AMPK activation in CTRP13-overexpressing rLSECs. Inhibition of CaMKKß and AMPK disturbed the protective effects of CTRP13 in high glucose-induced increase of LN and CAV-1. Hepatic steatosis was enhanced and basement membrane was thickened in liver of diabetic fatty liver rats. CONCLUSIONS: Our data identified the protective role of CTRP13 in hepatic sinusoidal capillarization induced by high glucose via activating CAMKKß/AMPK pathway. CTRP13 may be a potential target for screening and treating diabetic fatty liver. METHODS: Construct lentiviral CTRP13 overexpression vector and transfect rLSECs. Use STO-609 (a CaMKKß inhibitor) or Compound C (an AMPK inhibitor) to treat rLSECs. CTRP13, CaMKKß, AMPK, laminin (LN) and caveolin-1 (CAV-1) were detected by qRT-PCR and Western blotting. Establish rat model of diabetic fatty liver. Use immunohistochemistry, hematoxylin-eosin and silver staining to observe the histopathological features of liver.

High glucose/ox-LDL induced hepatic sinusoidal capillarization via αvß5/FAK/ERK signaling pathway.

OBJECTIVE: The main purpose of this study is to explore the role of integrin αvß5 in hepatic sinusoidal capillarization under high glucose/ox-LDL conditions. METHODS: Establish rat model of diabetic fatty liver disease. LSECs were extracted from tissue obtained from rats of control group, cultured and treated with media containing glucose (25 mM, 24 h)/ox-LDL (100 µg/ml, 24 h) in different inhibitors. The expression of integrin αvß5, FAK, ERK, VN in LSECs were detected by RT-PCR and Western blot. Hematoxylin-eosin staining and gomori methenaminutese silver stain was used to observe the basement membrane histopathological features of the liver tissue. Immunohistochemical to detected the protein expression of integrin αvß5 and VN in liver tissue. Using scanning electron microscopy to visualise the fenestration frequency and fenestration diameter. Protein expression of VN was also testified by immunofluorescence assay. RESULTS: CONCLUSIONS: Integrin αvß5 which induces LSECs dysfunction, promoting hepatic sinusoidal capillarization regulates VN expression via ERK/FAK pathway under high glucose/ox-LDL, may be a potential target for prevention and treatment of T2DM with fatty liver disease.