Alkaline phosphatase is involved in the control of adipogenesis in the murine preadipocyte cell line, 3T3-LI

Objective: As alkaline phosphatase may play a role in cell differentiation, our aim was to study the possible role of this enzyme in the differentiation of preadipocytes (3T3-L1 cells) into adipocytes. Research Methods and Procedures: 3T3-L1 cells were grown in medium containing insulin, dexamethasone and IBMX to induce adipogenesis. Adipogenesis was measured using the triglyceride-specific dye, oil red O at 0, 3, 7 and 11 days after initiation of adipogenesis in the presence or absence of the alkaline phosphatase inhibitors, levamisole, histidine and Phe-Gly-Gly. Intracellular localisation of the enzyme was detected using ELF-phosphatase, a fluorescent substrate and alkaline phosphatase gene expression was assessed using RT-PCR. Results: Alkaline phosphatase activity was detected in untransformed cells (1.91 +/- 0.62 mU/mg protein) and activity increased 11.5 +/- 1.4-fold after 11 days treatment with transformation medium and 5.3 +/- 0.3-fold in transforination medium containing levamisole (p < 0.05). Triglyceride content of cells increased 3.1 +/- 0.2-fold after 11 days treatment with transformation medium and 2.1 +/- 0.3-fold in the presence of levamisole (p < 0.005). Histidine inhibited adipogenesis and alkaline phosphatase to a greater extent than did levarnisole, but Phe-Gly-Gly had no effect on these variables. Alkaline phosphatase was localised around the lipid droplets of the cells. Gene expression of alkaline phosphatase increased during adipogenesis. Discussion: This study demonstrates that tissue-nonspecific alkaline phosphatase is present in 3T3-L1 cells and that it may play a role in the control of adipogenesis. (c) 2004 Elsevier B.V. All rights reserved.