Saturated phosphatidic acids mediate saturated fatty acid–induced vascular calcification and lipotoxicity
Masashi Masuda, … , Makoto Kuro-o, Makoto Miyazaki
Masashi Masuda, … , Makoto Kuro-o, Makoto Miyazaki
Published October 26, 2015
Citation Information: J Clin Invest. 2015;125(12):4544-4558. https://doi.org/10.1172/JCI82871.
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Research Article Vascular biology

Saturated phosphatidic acids mediate saturated fatty acid–induced vascular calcification and lipotoxicity

Abstract

Recent evidence indicates that saturated fatty acid–induced (SFA-induced) lipotoxicity contributes to the pathogenesis of cardiovascular and metabolic diseases; however, the molecular mechanisms that underlie SFA-induced lipotoxicity remain unclear. Here, we have shown that repression of stearoyl-CoA desaturase (SCD) enzymes, which regulate the intracellular balance of SFAs and unsaturated FAs, and the subsequent accumulation of SFAs in vascular smooth muscle cells (VSMCs), are characteristic events in the development of vascular calcification. We evaluated whether SMC-specific inhibition of SCD and the resulting SFA accumulation plays a causative role in the pathogenesis of vascular calcification and generated mice with SMC-specific deletion of both Scd1 and Scd2. Mice lacking both SCD1 and SCD2 in SMCs displayed severe vascular calcification with increased ER stress. Moreover, we employed shRNA library screening and radiolabeling approaches, as well as in vitro and in vivo lipidomic analysis, and determined that fully saturated phosphatidic acids such as 1,2-distearoyl-PA (18:0/18:0-PA) mediate SFA-induced lipotoxicity and vascular calcification. Together, these results identify a key lipogenic pathway in SMCs that mediates vascular calcification.

Authors

Masashi Masuda, Shinobu Miyazaki-Anzai, Audrey L. Keenan, Kayo Okamura, Jessica Kendrick, Michel Chonchol, Stefan Offermanns, James M. Ntambi, Makoto Kuro-o, Makoto Miyazaki

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Figure 5

SFAs were preferentially incorporated into PA and accumulated as fully saturated PAs in VSMCs in vitro and in vivo.

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SFAs were preferentially incorporated into PA and accumulated as fully s...
(A) Schematic representation of GPAT4, AGPAT3, and AGPAT5, which are localized in the ER. (B) Autoradiography and (C) quantification of SCD activity in human VSMCs treated with 300 nM of the SCDi CAY10566 using 14C-18:0 and 14C-16:0 as substrates (n = 6). VSMCs were treated with 14C-18:0 and 14C-16:0 for 6 hours in the presence/absence of SCDi. SFAs and MUFAs isolated from total cell lysate were separated on a silver nitrate–coated TLC. (D) Autoradiography and quantification of (E) 14C-18:0 and (F) 16:0 incorporation into the lipid fraction in human VSMCs treated with SCDi. Human VSMCs were pretreated with SCDi for 2 hours and incubated with 14C-18:0 and 14C-16:0 for 6 hours in the presence/absence of SCDi. Total lipids isolated from total cell lysate (3 mg protein) were separated on a boric acid–coated TLC. (G) LC-MS–based lipidomic analysis and (H) absolute levels of PA species in VSMCs treated with SCDi. Human VSMCs were treated with SCDi for 12 hours. Lipid content was quantified with LC-MS/MS. (I) LC-MS–based lipidomic analysis and (J) absolute levels of PA species in the aortic medial layers of SMC-Scd1/2 KO mice. Mice (n = 6) were sacrificed at 18 weeks old. The medial layer of aortas were dissected under a dissecting microscope. LPE, lysophosphatidylethanolamine; NL, neutral lipids. *P < 0.01 (2-tailed Student’s t test).