title: High glucose, insulin and free fatty acid concentrations synergistically enhance perilipin 3 expression and lipid accumulation in macrophages.
abstract: OBJECTIVE
  Perilipin (PLIN) 3, an intracellular lipid droplet (LD)-associated protein, is implicated in foam cell formation. Since metabolic derangements found in metabolic syndrome, such as high serum levels of glucose, insulin and free fatty acids (FFAs), are major risk factors promoting atherosclerosis, we investigated whether PLIN3 expression is affected by glucose, insulin and oleic acid (OA) using RAW264.7 cells.
  
  
  METHODS
  Real-time PCR and Western blotting were performed to detect PLIN3 or PLIN2 expression. Oil-red O staining and Lipid Analysis were employed to measure cellular content of triacylglycerides (TAG) and cholesterol.
  
  
  RESULTS
  PLIN3 mRNA was stimulated by high glucose or insulin concentrations individually, but not by OA. A combination of any two factors did not enhance PLIN3 expression any more than that evoked by glucose alone at 24h. Interestingly, however, simultaneous addition of all three factors synergistically enhanced the PLIN3 expression. This synergistic effect was not apparent for PLIN2 mRNA expression. Inhibitors of Src family tyrosine kinase and/or phosphatidylinositol 3-kinase, both of which are activated by insulin and FFA signaling, partially suppressed PLIN3 expression induced by the combination of the three factors. While simultaneous addition of glucose, insulin and OA remarkably increased the cellular content of TAG and cholesterol, knocking-down of PLIN3 predominantly reduced TAG content.
  
  
  CONCLUSIONS
  These results indicate that PLIN3 expression is synergistically stimulated by high glucose, insulin and FFA concentrations, in parallel with TAG accumulation in macrophages. This finding raises new evidence of PLIN3 involvement in conversion of macrophages into foam cells.
authors.affiliation: Department of Neurology, Shengjing Hospital, China Medical University, Shenyang 11004, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Fan
authors.forename: Jian-Qiu
authors.initials: JQ
authors.lastname: Gu
authors.forename: Rong
authors.initials: R
authors.lastname: Yan
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Juan
authors.initials: J
authors.lastname: Feng
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ikuyama
mesh_terms: D000818:Animals; D001391:Azo Compounds; D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002784:Cholesterol / Q000097:blood; D004396:Coloring Agents; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D050356:Lipid Metabolism / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D019301:Oleic Acid / Q000494:pharmacology; D000070796:Perilipin-3; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D014162:Transfection; D014280:Triglycerides / Q000097:blood; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D001391:Azo Compounds; D002352:Carrier Proteins; D004396:Coloring Agents; D005230:Fatty Acids, Nonesterified; D007004:Hypoglycemic Agents; D007328:Insulin; D000070796:Perilipin-3; C523440:Plin3 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014280:Triglycerides; D019301:Oleic Acid; D002784:Cholesterol; D019869:Phosphatidylinositol 3-Kinases; D019061:src-Family Kinases; C011049:oil red O; D005947:Glucose
keywords: ADRP; FFAs; Foam cell; G protein-coupled receptor; GPR; LDs; Metabolic syndrome; OA; OXPAT; PI3K; PLIN; PLIN2; PLIN3; PPAR; Perilipin; TAGs; TIP47; adipose differentiation-related protein; free fatty acids; lipid droplets; oleic acid; oxidative tissue-enriched PAT protein; perilipin; peroxisome proliferator-activated receptor; phosphatidylinositol 3-kinase.; tail interacting protein of 47kDa; triacylglycerides