👤 Fàtima Sabench

This cohort study aimed to explore the relationship between the Notch signaling pathway and the degree of nonalcoholic fatty liver disease (NAFLD). Moreover, this study intended to investigate whether this pathway is related to hepatic lipid metabolism and Toll-like receptors (TLRs). This study used real-time polymerase chain reaction analysis to evaluate the hepatic expression level of all genes studied (Notch receptors NOTCH1, NOTCH2, NOTCH3, and NOTCH4, transcription factors HES1 and HES5, and Hes-related repressor proteins HEY1 and HEY2) in hepatic tissue from two cohorts: women with severe obesity (n = 57) and normal liver structure (n = 20) or NAFLD (n = 37). In women with severe obesity and NAFLD, this study found downregulation of hepatic HES5 expression. This expression correlated positively with the hepatic expression of HES1, HEY1, and NOTCH3. This study also found a positive correlation between HES5 expression and sterol regulatory element-binding protein 1c (SREBP1c) and between NOTCH3 and several genes related to hepatic lipid metabolism (encoding liver X nuclear receptor α variant 1, farnesoid X nuclear receptor, SREBP1c, acetyl-CoA carboxylase 1, fatty acid synthase, peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1, carnitine O-octanoyltransferase, ATP-binding cassette subfamily A member 1, and ATP-binding cassette subfamily G member 1). Finally, this study found a positive correlation between NOTCH2 and TLR2, TLR4, and TLR9 and a positive relationship between NOTCH1 and TLR9. Taken together, these findings suggest that hepatic expression of Notch proteins and ligands in relation to lipid metabolism pathways in the liver could have a role in NAFLD pathogenesis. Show less

The tissue-specific expression profiles of genes within the APOA1/C3/A4/A5 cluster play an important role in lipid metabolism regulation. We hypothesize that the tissue-specific expression of the APOA1/C3/A4/A5 gene cluster will show an inverse pattern with DNA methylation, and that repression in non- or low-expressing tissue, such as the intestine, can be reversed using epigenetic drugs. We analyzed DNA samples from different human adult tissues (liver, intestine, leukocytes, brain, kidney, pancreas, muscle and sperm) using the Infinium HumanMethyation450 BeadChip array. DNA methylation profiles in APOA1/C3/A4/A5 gene cluster were confirmed by bisulfite PCR and pyrosequencing. To determine whether the observed tissue-specific methylation was associated with the expression profile we exposed intestinal TC7/Caco-2 cells to the demethylating agent 5-Aza-2'-deoxycytidine and monitored intestinal APOA1/C3/A4/A5 transcript re-expression by RT-qPCR. The promoters of APOA1, APOC3 and APOA5 genes were less methylated in liver compared to other tissues, and APOA4 gene was highly methylated in most tissues and partially methylated in liver and intestine. In TC7/Caco-2 cells, 5-Aza-2'-deoxycytidine treatment induced a decrease between 37 and 24% in the methylation levels of APOA1/C3/A4/A5 genes and a concomitant re-expression mainly in APOA1, APOA4 and APOA5 genes ranging from 22 to 600%. We have determined the methylation patterns of the APOA1/C3/A4/A5 cluster that may be directly involved in the transcriptional regulation of this cluster. DNA demethylation of intestinal cells increases the RNA levels especially of APOA1, APOA4 and APOA5 genes. Show less