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Smooth muscle‐specific deletion of O‐GlcNAc transferase inhibits SMC de‐differentiation in STZ‐induced hyperglycemic mice
Author(s) -
Khanal Saugat,
Mathias Amy,
Lallo Jason,
Ferrell Jessica,
Ohanyan Vahagn,
Raman Priya
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.05298
Subject(s) - tamoxifen , endocrinology , medicine , diabetes mellitus , cre recombinase , streptozotocin , biology , in vivo , vascular smooth muscle , chemistry , smooth muscle , biochemistry , transgene , gene , genetically modified mouse , microbiology and biotechnology , cancer , breast cancer
Vascular smooth muscle cell (VSMC) migration and proliferation, hallmark of SMC phenotypic switching central to the evolution of atherosclerosis, is profoundly enhanced in diabetic patients. Hyperglycemia, characteristic of diabetes, increases glucose flux through the hexosamine metabolic pathway triggering an enhanced signaling via O‐linked N‐acetylglucosamine (O‐GlcNAc) transferase (OGT), key regulator of protein O‐GlcNAcylation. Multiple studies, including ours, support an association between O‐GlcNAcylation and diabetes‐related complications. However, the role of OGT in VSMC activation in diabetes remains elusive. The goal of the present study was to interrogate whether OGT plays a direct role in SMC de‐differentiation in hyperglycemic mice in vivo . Briefly, we crossed OGT fl/fl female mice with tamoxifen‐inducible Myh11‐Cre ER T2 male mice (Cre tg ); the resulting Cre tg /OGT fl/Y males (produced in F1 generation) were used for Cre recombinase activation. Specifically, Cre tg /OGT fl/Y and age‐matched Cre tg /OGT +/Y littermates at 6 wks age were injected i.p. with tamoxifen (60mg/kg/day) or peanut oil (vehicle control) once daily for 5 consecutive days. Two weeks post‐tamoxifen, mice genotypes received low‐dose STZ (50mg/Kg/day, i.p) or vehicle (citrated buffer) once daily for 5 consecutive days for induction of hyperglycemia. At 16 wks age, mice were subjected to metabolic profiling and cardiac function studies followed by plasma, heart and aortic tissue harvests. Immunoblotting of aortic lysates confirmed loss of OGT expression in tamoxifen‐treated Cre tg /OGT fl/Y (smOGT −/Y ) mice compared to vehicle‐treated Cre tg /OGT fl/Y littermates and tamoxifen‐treated OGT fl/Y mice (smOGT +/Y , with intact OGT). In contrast, OGT expression was unaltered in left ventricular tissue lysates derived from smOGT −/Y vs. smOGT +/Y mice, validating our SMC‐specific OGT knockout mouse model. Immunoblotting further revealed augmented α‐SMA and Calponin expression (SM contractile markers) in aortic vessels of hyperglycemic smOGT −/Y vs. hyperglycemic smOGT +/Y mice. This was accompanied with attenuated PCNA (proliferation marker) and Vimentin (SM synthetic marker) expression in aortic vasculature of smOGT −/Y vs smOGT +/Y mice, under conditions of hyperglycemia. Importantly, increased α‐SMA and Calponin expression occured concomitant to reduced YY1 (transcriptional repressor of SM contractile genes) expression in aortic vessels of smOGT −/Y vs. smOGT +/Y mice, in response to STZ‐induced hyperglycemia. Interestingly, SMC‐specific OGT deletion had no effect on cardiac function of the mice genotypes under basal and hyperglycemic conditions, shown via Echocardiography. Moreover, hyperglycemic smOGT −/Y mice revealed a time‐dependent increase in energy expenditure reflected in differences in O 2 consumption and CO 2 production compared to hyperglycemic smOGT +/Y mice, depicted via CLAMS studies. Taken together, our results demonstrate a direct regulatory role of OGT on VSMC phenotypic transformation in response to hyperglycemia. Overall, the current study suggests OGT as a potential target in diabetic atherosclerotic disease. Support or Funding Information AHA‐Grant‐in‐Aid 16GRNT31200034; NIH‐NHLBI 1R56HL141409‐01