title: Sphingomyelin synthase overexpression increases cholesterol accumulation and decreases cholesterol secretion in liver cells.
abstract: BACKGROUND
  Studies have shown that plasma high density lipoprotein cholesterol levels are negatively correlated with the development of atherosclerosis, whereas epidemiological studies have also shown that plasma sphingomyelin level is an independent risk factor for atherosclerosis.
  
  
  METHODS
  To evaluate the relationship between cellular sphingomyelin level and cholesterol metabolism, we created two cell lines that overexpressed sphingomyelin synthase 1 or 2 (SMS1 or SMS2), using the Tet-off expression system.
  
  
  RESULTS
  We found that SMS1 or SMS2 overexpression in Huh7 cells, a human hepatoma cell line, significantly increased the levels of intracellular sphingomyelin, cholesterol, and apolipoprotein A-I and decreased levels of apolipoprotein A-I and cholesterol in the cell culture medium, implying a defect in both processes.
  
  
  CONCLUSIONS
  Our findings indicate that the manipulation of sphingomyelin synthase activity could influence the metabolism of sphingomyelin, cholesterol and apolipoprotein A-I.
authors.affiliation: School of Pharmacy, Fudan University, Shanghai, People's Republic of China.
authors.forename: Nianlong
authors.initials: N
authors.lastname: Yan
authors.forename: Tingbo
authors.initials: T
authors.lastname: Ding
authors.forename: Jibin
authors.initials: J
authors.lastname: Dong
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.forename: Manping
authors.initials: M
authors.lastname: Wu
mesh_terms: D016632:Apolipoprotein A-I / Q000378:metabolism; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism; D013109:Sphingomyelins; D017855:Transferases (Other Substituted Phosphate Groups) / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D016632:Apolipoprotein A-I; D013109:Sphingomyelins; D002784:Cholesterol; D017855:Transferases (Other Substituted Phosphate Groups); C070186:phosphatidylcholine-ceramide phosphocholine transferase