Abstract MP48: Smooth Muscle Cell-Specific Deletion Of O-GlcNAc Transferase Impedes Atherosclerotic Lesion Formation In Western Diet-fed Apoe -/- Mice

Abstract

Attachment of O-linked N-acetylglucosamine (O-GlcNAc) to nucleocytoplasmic proteins or ‘O-GlcNAcylation’ is a ubiquitous post-translational modification affecting numerous cellular processes. We and others have previously reported that augmented protein O-GlcNAcylation mediates upregulation of numerous genes associated with atherosclerosis. Recent studies suggest the role of O-GlcNAc transferase (OGT), a key regulator of O-GlcNAc signaling, in diabetic vascular calcification and wound healing. However, the role of OGT in the etiology of atherosclerosis is elusive. The goal of the current study was to interrogate whether OGT plays a direct role in the development of atherosclerosis. For this, we crossed tamoxifen-inducible male Myh11-CreERT2;OGT fl/y ;ApoE -/- mice with female OGT fl/+ ;ApoE -/- to generate SMC-specific OGT knockout on ApoE -/- background. To induce Cre recombinase activity, mice genotypes were injected i.p. with 60mg/Kg/day tamoxifen (peanut oil-vehicle control) once daily for 5 consecutive days beginning at 6 wks age. This was followed by a Western diet feeding regimen for additional 6-7 wks. Mice were harvested at 14 wks age after overnight fasting; plasma, aorta, and heart were collected for biochemical, molecular, and lesion studies. Immunoblotting confirmed loss of OGT expression in aortic vessels of tamoxifen-treated Cre tg ;OGT fl/y ;ApoE -/- mice (smOGT KO ;ApoE -/- ) vs. age-matched tamoxifen-treated Cre tg ;OGT +/y ;ApoE -/- littermates (smOGT WT ;ApoE -/- , with intact OGT). Aortic root morphometry revealed a significant reduction (2.5-fold) in lesion lipid burden in smOGT KO ;ApoE -/- mice compared with smOGT WT ;ApoE -/- . This was accompanied by attenuated PCNA (proliferation marker), osteopontin (SM synthetic marker), pERK (SM signaling regulator), YY1 (transcriptional repressor of SM contractile genes), and SRF (transcriptional regulator of SMC proliferation) expression in smOGT KO ;ApoE -/- vs. smOGT WT ;ApoE -/- aortic lysates, shown via immunoblotting. Interestingly, SMC-specific OGT deletion had no effect on plasma total cholesterol and total triglyceride levels. Taken together, these results demonstrate a protective role of SMC-specific loss of OGT on atherosclerotic lesion formation.