Specific knock-down of tissue non-specific alkaline phosphatase mRNA levels inhibits intracellular lipid accumulation in 3T3-L1 and HepG2 cells.

The use of non-specific inhibitors of tissue non-specific alkaline phosphatase (TNSALP) in pre-adipocytes blocks intracellular lipid accumulation. TNSALP is also expressed in hepatocytes, which are known to accumulate lipid in a similar manner to pre-adipocytes. The purpose of this study was to use specific silencing of TNSALP mRNA, using short interfering (si) RNA, to investigate the role of TNSALP in intracellular lipid accumulation in 3T3-L1 and HepG2 cells. Cellular activity of TNSALP was measured using an automated colorimetric assay, and intracellular lipid accumulation was determined using the lipid-specific dye, Oil Red O. Cells were transfected with siRNA directed against TNSALP mRNA, and expression of the TNSALP gene was determined at selected time points postinduction of lipid droplet formation. Expression of the TNSALP gene was inhibited by a maximum of 88 ± 1.9% (P < 0.005 vs. control) 11 days after initiation of lipid droplet formation in the 3T3-L1 cells and 80 ± 8.9% (P < 0.05 vs. control) after 4 days in the HepG2 cells. This led to significant inhibition of both TNSALP activity and intracellular lipid accumulation in both cell lines. These data demonstrates that TNSALP plays an important role in the control of lipid droplet formation in both pre-adipocyte and hepatocyte cell lines.