Adipocyte modulation of high-density lipoprotein cholesterol

Area of Science:

• Metabolic research
• Lipid metabolism
• Adipocyte biology

Background:

• Adipose tissue stores significant free cholesterol.
• The role of adipose tissue in high-density lipoprotein (HDL) cholesterol lipidation in vivo is not well-established.

Purpose of the Study:

• To investigate the role of adipocytes in cholesterol transfer to HDL in vivo and in vitro.
• To identify the specific cholesterol transporters involved in this process.

Main Methods:

• Cholesterol efflux assays using wild-type and knockout adipocytes (ABCA1, SR-BI, ABCG1).
• In vivo studies involving intraperitoneal injection of labeled adipocytes into mice.
• Assessment of tumor necrosis factor-alpha effects on transporter expression and cholesterol efflux.

Main Results:

• Cholesterol efflux to apolipoprotein A-I (apoA-I) and HDL3 was impaired in ABCA1(-/-) and SR-BI(-/-) adipocytes, respectively.
• In vivo studies confirmed adipocyte contribution to HDL cholesterol, dependent on apoA-I levels.
• Tumor necrosis factor-alpha reduced ABCA1 and SR-BI expression, impairing cholesterol efflux.

Conclusions:

• Adipocytes possess a novel metabolic function in promoting cholesterol transfer to HDL in vivo.
• Adipocyte SR-BI and ABCA1, but not ABCG1, are implicated in this cholesterol transfer process.
• Adipocyte modulation of HDL may be compromised in inflammatory adipose conditions, such as type 2 diabetes mellitus.