CETP inhibitors downregulate hepatic LDL receptor and PCSK9 expression in vitro and in vivo through a SREBP2 dependent mechanism

Abstract

Background CETP inhibitors block the transfer of cholesteryl ester from HDL-C to VLDL-C and LDL-C, thereby raising HDL-C and lowering LDL-C. In this study, we explored the effect of CETP inhibitors on hepatic LDL receptor (LDLR) and PCSK9 expression and further elucidated the underlying regulatory mechanism. Results We first examined the effect of anacetrapib (ANA) and dalcetrapib (DAL) on LDLR and PCSK9 expression in hepatic cells in vitro. ANA exhibited a dose-dependent inhibition on both LDLR and PCSK9 expression in CETP-positive HepG2 cells and human primary hepatocytes as well as CETP-negative mouse primary hepatocytes (MPH). Moreover, the induction of LDLR protein expression by rosuvastatin in MPH was blunted by cotreatment with ANA. In both HepG2 and MPH ANA treatment reduced the amount of mature form of SREBP2 (SREBP2-M). In vivo, oral administration of ANA to dyslipidemic C57BL/6J mice at a daily dose of 50 mg/kg for 1 week elevated serum total cholesterol by approximately 24.5% (p<0.05%) and VLDL-C by 70% (p<0.05%) with concomitant reductions of serum PCSK9 and liver LDLR/SREBP2-M protein. Finally, we examined the in vitro effect of two other strong CETP inhibitors evacetrapib and torcetrapib on LDLR/PCSK9 expression and observed a similar inhibitory effect as ANA in a concentration range of 1–10 µM. Conclusion Our study revealed an unexpected off-target effect of CETP inhibitors that reduce the mature form of SREBP2, leading to attenuated transcription of hepatic LDLR and PCSK9. This negative regulation of SREBP pathway by ANA manifested in mice where CETP activity was absent and affected serum cholesterol metabolism.

New CETP inhibitor K-312 reduces PCSK9 expression: a potential effect on LDL cholesterol metabolism

“…4A). A recent study showed that anacetrapib, torcetrapib, and evacetrapib decreased PCSK9 levels via SREBP-2 in vitro and in vivo (11). However, our more in-depth study into the PCSK9 promoter occupancies by SREBP-1 and -2 demonstrated decreased binding of both transcription regulators in response to K-312 treatment, a candidate mechanism for the increased potency of K-312 treatment over the other CETP/PCSK9 inhibitors (Fig.…”

Regulation of lipid metabolism by obeticholic acid in hyperlipidemic hamsters

“…Significant differences between control and treatment groups were assessed by oneway ANOVA with Dunnett's Multiple Comparison posttest or chylomicron (CM; >80 nm), VLDL (30-80 nm), LDL (16-30 nm), and HDL (8-16 nm) with a dual detection HPLC system consisting of two tandem connected TSK gel Lipopropak XL columns (300 × 7.8 mm; Tosoh, Japan) at Skylight Biotech, Inc. (Tokyo, Japan), as we previously described (25). In addition, 50 l of serum sample from two animals of the same treatment group of day 0, day 7, and day 13 were pooled together and analyzed for cholesterol and TG levels in different lipoprotein fractions after HPLC separation at Skylight Biotech, Inc.…”

Inhibition of PCSK9 Transcription by Berberine Involves Down-regulation of Hepatic HNF1α Protein Expression through the Ubiquitin-Proteasome Degradation Pathway

“…For HepG2 cells, total cell lysates and cytoplasmic and nuclear fractions were isolated as described previously (24,25). Protein concentration was determined using BCA protein assay reagent (Pierce).…”