Plasma PCSK9 levels are significantly modified by statins and fibrates in humans.
BACKGROUND
Proprotein convertase subtilisin kexin-like 9 (PCSK9) is a secreted glycoprotein that is transcriptionally regulated by cholesterol status. It modulates levels of circulating low density lipoprotein cholesterol (LDLC) by negatively regulating low density lipoprotein receptor (LDLR) levels. PCSK9 variants that result in 'gain of function' have been linked to autosomal dominant hypercholesterolemia, while significant protection from coronary artery disease has been documented in individuals who carry 'loss of function' PCSK9 variants. PCSK9 circulates in human plasma, and we previously reported that plasma PCSK9 is positively correlated with total cholesterol and LDLC in men.


RESULTS
Herein, we report the effects of two lipid-modulating therapies, namely statins and fibrates, on PCSK9 plasma levels in human subjects. We also document their effects on endogenous PCSK9 and LDLR expression in a human hepatocyte cell line, HepG2, using immunoprecipitation and immunoblot analyses. Changes in plasma PCSK9 following fenofibrate or gemfibrozil treatments (fibric acid derivatives) were inversely correlated with changes in LDLC levels (r = -0.558, p = 0.013). Atorvastatin administration (HMGCoA reductase inhibitor) significantly increased plasma PCSK9 (7.40%, p = 0.033) and these changes were inversely correlated with changes in LDLC levels (r = -0.393, p = 0.012). Immunoblot analyses of endogenous PCSK9 and LDLR expression by HepG2 cells in response to statins and fibrates showed that LDLR is more upregulated than PCSK9 by simvastatin (2.6x vs 1.5x, respectively at 10 muM), while fenofibrate did not induce changes in either.


CONCLUSIONS
These results suggest that in vivo (1) statins directly increase PCSK9 expression while (2) fibrates affect PCSK9 expression indirectly through its modulation of cholesterol levels and (3) that these therapies could be improved by combination with a PCSK9 inhibitor, constituting a novel hypercholesterolemic therapy, since PCSK9 was significantly upregulated by both treatments.
Mayne
Janice
J
Chronic Disease Program, Ottawa Health Research Institute, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada. jmayne@ohri.ca
Dewpura
Thilina
T
Raymond
Angela
A
Cousins
Marion
M
Chaplin
Anna
A
Lahey
Karen A
KA
Lahaye
Stephen A
SA
Mbikay
Majambu
M
Ooi
Teik Chye
TC
Chrétien
Michel
M
D000069059:Atorvastatin; D002995:Clofibric Acid / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006538:Heptanoic Acids / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D011758:Pyrroles / Q000008:administration & dosage / Q000494:pharmacology; D011973:Receptors, LDL / Q000097:blood; D012697:Serine Endopeptidases / Q000097:blood*
D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011758:Pyrroles; D011973:Receptors, LDL; D002995:Clofibric Acid; D000069059:Atorvastatin; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases