Glucagon-Like Peptide-1 Modulates Cholesterol Homeostasis by Suppressing the miR-19b-Induced Downregulation of ABCA1.

BACKGROUND/AIMS: Abnormal regulation of cholesterol homeostasis is associated with type 2 diabetes mellitus (T2DM) and multiple other diseases. Glucagon-like peptide-1 (GLP-1) has unique effects on modulating hepatic lipid metabolism. However, the mechanism behind these is largely unknown. The aim of this study was to investigate the effects of GLP-1 on cholesterol-induced lipotoxicity in hepatocytes and examine the underlying mechanisms.

METHODS: Cell viability was determined by CCK-8. Caspase-3 detection was used to assess the effects of GLP-1 on cholesterol-induced apoptosis. TNF-α and IL-6 as the inflammatory markers were measured by ELISA. The alterations of miR-19b and ATP-binding cassette transporter A1 (ABCA1) resulting from high-fat diet/cholesterol incubation or GLP-1 were detected by real-time PCR and western blot.

RESULTS: GLP-1 markedly up-regulated the expression of ABCA1 protein, but didn't affect peroxisome proliferator-activated receptor α (PPAR-α) protein. The miR-19b levels were significantly down-regulated in GLP-1-treated groups. The inhibition and overexpression of miR-19b were established to explore the effects of a GLP-1-mediated alteration in miR-19b. Cholesterol transport assays revealed that treatment with GLP-1 alone or together with miR-19b inhibitor significantly enhanced ABCA1-dependent cholesterol efflux, resulting in reduced total cholesterol. Further, histological examination was used to detect lipid accumulation. Cholesterol significantly attenuated cell viability, promoted hepatic cell apoptosis, and facilitated lipid accumulation, and these effects could be reversed by GLP-1.

CONCLUSION: GLP-1 may affect cholesterol homeostasis by regulating the expression of miR-19b and ABCA1.