Lipidation of HDL is essential to provide the atheroprotective functions of HDL in vivo and is determined via a number of cholesterol transporters in several cholesterol-rich tissues such as the liver. Adipose tissue contains a large pool of free cholesterol, but it is not documented if adipose tissue is involved in cholesterol lipidation of HDL in vivo. The aim of this study was to investigate whether adipocytes are involved in the transfer of cholesterol to HDL in vivo as well as in vitro. Results showed that adipocytes are in fact a source of cholesterol for lipidation of HDL and the cholesterol efflux is controlled by ATP-binding cassette subfamily A member 1 (ABCA1) and scavenger receptor class B type 1 (SR-B1), but not ATP-binding cassette subfamily G member 1 (ABCG1). Moreover, it was reported that adipocyte inflammation downregulates transporters and impairs adipocyte cholesterol efflux to HDL which could explain the presence of low HDL in metabolic diseases associated with abdominal obesity such as metabolic syndrome and type 2 diabetes.
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