Hepatic PCSK9 expression is regulated by nutritional status via insulin and sterol regulatory element-binding protein 1c.
Familial autosomal dominant hypercholesterolemia is associated with high risk for cardiovascular accidents and is related to mutations in the low density lipoprotein receptor or its ligand apolipoprotein B (apoB). Mutations in a third gene, proprotein convertase subtilisin kexin 9 (PCSK9), were recently associated to this disease. PCSK9 acts as a natural inhibitor of the low density lipoprotein receptor pathway, and both genes are regulated by depletion of cholesterol cell content and statins, via sterol regulatory element-binding protein (SREBP). Here we investigated the regulation of PCSK9 gene expression during nutritional changes. We showed that PCSK9 mRNA quantity is decreased by 73% in mice after 24 h of fasting, leading to a 2-fold decrease in protein level. In contrast PCSK9 expression was restored upon high carbohydrate refeeding. PCSK9 mRNA increased by 4-5-fold in presence of insulin in rodent primary hepatocytes, whereas glucose had no effect. Moreover, insulin up-regulated hepatic PCSK9 expression in vivo during a hyperinsulinemic-euglycemic clamp in mice. Adenoviral mediated overexpression of a dominant or negative form of SREBP-1c confirmed the implication of this transcription factor in insulin-mediated stimulation of PCSK9 expression. Liver X receptor agonist T0901317 also regulated PCSK9 expression via this same pathway (a 2-fold increase in PCSK9 mRNA of primary hepatocytes cultured for 24 h in presence of 1 microm T0901317). As our last investigation, we isolated PCSK9 proximal promoter and verified the functionality of a SREBP-1c responsive element located from 335 bp to 355 bp upstream of the ATG. Together, these results show that PCSK9 expression is regulated by nutritional status and insulinemia.
Costet
Philippe
P
INSERM, U539, CHU Hôtel Dieu, 44000, Nantes, France. philippe.costet@univ-nantes.fr
Cariou
Bertrand
B
Lambert
Gilles
G
Lalanne
Florent
F
Lardeux
Bernard
B
Jarnoux
Anne-Laure
AL
Grefhorst
Aldo
A
Staels
Bart
B
Krempf
Michel
M
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000819:agonists; D005215:Fasting / Q000378:metabolism; D005260:Female; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D006845:Hydrocarbons, Fluorinated; D007328:Insulin / Q000502:physiology*; D000071518:Liver X Receptors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009747:Nutritional Physiological Phenomena / Q000502:physiology*; D057093:Orphan Nuclear Receptors; D011401:Promoter Regions, Genetic; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists; D050436:Regulatory Elements, Transcriptional / Q000502:physiology; D012697:Serine Endopeptidases / Q000096:biosynthesis* / Q000235:genetics*; D051780:Sterol Regulatory Element Binding Protein 1 / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
D004268:DNA-Binding Proteins; D006845:Hydrocarbons, Fluorinated; D007328:Insulin; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D012697:Serine Endopeptidases; D051780:Sterol Regulatory Element Binding Protein 1; D013449:Sulfonamides; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides; C472126:Pcsk9 protein, mouse