Stable NgBR knockdown HepG2 (shNgBRi) cells were generated as described in the supplemental information and used to conduct the following experiments. (A) NgBR knockdown in shNgBRi cells was characterized by western blotting and real time RT-PCR. *: P<0.05 vs. control (shNSi) cells (n=3). (B) Determination of cellular lipid accumulation by Oil Red O staining. (C) Quantitative analysis of cellular FFA and TG levels. *: P<0.05 vs. shNSi cells (n=3). (D) Control HepG2 cells (shNSi) and NgBR-deficient HepG2 cells (shNgBRi) were cultured in MEM medium containing 10% regular or lipoprotein-deficient serum (Kalen Biomedical, Montgomery village, MD) for 24 h followed by Oil Red O staining (left panel). Quantitative levels of total lipid content in shNSi and shNgBRi cells were determined as described in the Methods. *, #: P<0.05 vs. shNSi cells in MEM medium containing either regular or lipoprotein deficient serum, respectively (n=3). (E, F) Overexpression of NgBR attenuates NgBR deficiency-caused lipid accumulation. shNgBRi cells were transiently transfected with an NgBR expression vector for 24 h. NgBR expression was then determined by western blotting (E). Cellular lipid content was determined by Oil Red O staining and quantitative analysis, respectively (F). *: P<0.05 vs. shNSi cells (n=3); #: P<0.05 vs. shNgBRi cells without transfection of NgBR expression vector (n=3).