Effect of extracellular fatty acids on lipid metabolism in cultured rabbit articular chondrocytes

Abstract

Rabbit articular chondrocytes were cultured for 8 h in the presence of various concentrations (5-500 microM) of [14C] oleic, [14C] linoleic, and [3H] arachidonic acids. The radioactive unsaturated fatty acids were incorporated into triacylglycerol (TG) and phosphatidylcholine (PC) in a concentration-dependent manner; more fatty acids were incorporated into TG than into PC, at higher concentrations of extracellular fatty acids. Among these fatty acids, arachidonic acid was incorporated into TG much more than into PC, in spite of a very low concentration of arachidonic acid in TG. After transfer of the labeled cells to maintenance medium, the radioactivity in TG declined rapidly and [3H] arachidonic acid radioactivity in PC increased continuously during the chase time periods. Palmitoyl-unsaturated species were mainly formed in PC when cultured at a concentration of 5 microM of each fatty acid. However, when cultured at 500 microM, unsaturated-unsaturated species, specific for each unsaturated fatty acid were actively formed. These findings indicate that (1) fatty acid composition of TG and PC in articular chondrocytes is influenced by the degree of fatty acid supply, (2) formation and turnover of TG plays a role in fatty acid metabolism of cells, and (3) fatty acid pairing in PC is modulated by extracellular fatty acid concentrations.

Lipid Transport and Metabolism in Healthy and Osteoarthritic Cartilage

“…Diets containing high levels of ω-3 fatty acids lead to a decrease in arachidonic (20:4n-6) and linoleic acids (18:2n-6) and an increase in eicosapentaenoic acid (20:5n-3) in cartilage [39,40]. In addition, Nagao et al demonstrated that extracellular fatty acids modulate intracellular lipid composition in cultured chondrocytes [41]. …”

“…In fact, phosphatidylethanolamine, phosphatidylcholine and sphingomyelin are major components of the articular cartilage boundary lubricant [46]. In addition to the presence of these phospholipids in the joint fluid, free fatty acids may be incorporated by chondrocytes into phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and triacylglycerol (TG) [41,47]. …”

Profiles of Fatty Acids in Different Bone Structures of Growing Chicks

“…The content of fatty acids differs in immature and mature cartilage (Adkisson et al, 1991;Nagao et al, 1991). Young cartilage demonstrates an extremely high content of 5,8,11-eicosatrienoic acid (C 20:3 n − 9) (Adkisson et al, 1991).…”