Hyperglycemia suppresses hepatic scavenger receptor class B type I expression

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• Hyperglycemia is a key risk factor for atherosclerotic disease.
• Hepatic scavenger receptor class B type I (SR-BI) plays a crucial role in reverse cholesterol transport, mitigating atherosclerosis risk.

Purpose of the Study:

• To investigate how glucose levels regulate SR-BI gene expression in liver cells and animal models.
• To elucidate the molecular signaling pathways involved in glucose-mediated suppression of SR-BI.

Main Methods:

• Utilized HepG2 cells and diabetic rat models to assess SR-BI expression under varying glucose concentrations.
• Employed promoter activity assays, signal transduction pathway inhibitors (p38 MAPK), and gene knockdown techniques (Sp1).

Main Results:

• High glucose significantly reduced hepatic SR-BI mRNA, protein levels, and cholesterol uptake from HDL.
• Glucose-induced suppression of SR-BI was mediated by the p38 MAPK-Sp1 signaling pathway.
• A specific 50-bp promoter fragment containing Sp1 binding sites was identified as critical for glucose regulation.

Conclusions:

• Glucose suppression of hepatic SR-BI expression is partially regulated by the p38 MAPK-Sp1 pathway.
• Inhibition of hepatic SR-BI under hyperglycemic conditions may contribute to accelerated atherosclerosis in diabetic individuals.