Higher levels of O-GlcNAcylation induce aortic stiffness by increasing elastase activity in male, but not female rats.
Authors: Costa Tiago J. , Montandon Ian , Wilson Emily , Fontes Milene , Pernomian Laena , McQuail Joseph , Webb Clinton , Camilla Wenceslau , McCarthy Cameron 
Published: May 2023

Age-associated structural and functional changes in the aorta, including stiffness, loss of elasticity, and reduced vasodilatation, are known to hamper stable peripheral circulation and lead to organ dysfunction. The extracellular matrix (ECM) is a network of macromolecules produced by resident cells. Remodeling of ECM components, include fragmentation of elastin and excessive deposition and crosslinking of collagens, and is a hallmark of aging which leads to stiffening of the aorta. Recently, O-linked beta-N-acetyl glucosamine (O-GlcNAc) has emerged as an essential regulator of cell stress and survival. Interestingly, higher levels of O-GlcNAc are a biomarker for cardiovascular risks (e.g., hypertension and diabetes). However, it is unknown whether O-GlcNAcylation contributes to age-associated aortic stiffness. The goal of these studies was divided into two parts: 1. To determine how the higher levels of O-GlcNAc impact aortic stiffness, and 2. To investigate any potential sex differences. To address this aims, the thoracic aorta was isolated from male and female Wistar and Fisher 344 rats at 3 (3M) and 16 months of age (16M) and mounted on a tissue puller (DMT) to evaluate vessel strain/stress. Blood pressure was measured directly in the carotid artery under anesthesia, and western blot, immunofluorescence, and histology were performed to measure O-GlcNAc levels, elastase expression, and elastin fragmentation, respectively. To induce O-GlcNAc, aorta from 3M Wistar rats were treated with Thiamet G, a pharmacological inhibitor of OGA (1 uM, 24h). The aorta from 3M males presented with a higher strain than age-matched females, indicating sex difference in stiffness (ß-coefficient: 2.5±0.9 vs. 1.6±0.6, p<0.05). However, this difference was abolished in old male and female rats (5.1±0.9 vs. 4.6±0.6 p<0.05 n= duplicates of 4-5). The systolic blood pressure in 16 MO males was increased by ~ 30 mmHg compared to 3M (87±3 vs. 117±4 p=3-4), while only increasing ~ 16 mmHg when compared to 3M and 16 MO females (83±3 vs. 99±4 p=3-4). We observed elevation in O-GlcNAc protein levels from aortas of 16 MO males and females, modestly higher in females. Counter-intuitively, the Thiamet G increased O-GlcNAc levels and induced aortic stiffness in males (2.1± 0.9 vs. 3.6± 0.9 p<0.05 n= duplicates 10), but not in females (2.6± 0.9 vs. 2.7±0.8 n= duplicates 5). The aortic stiffness in males was associated with increased elastin fragmentation and elastase expression (Control 100±10 vs. Thiamet G 400±70 UA p<0.05 n=duplicate 3), which was not observed in females. Collectively, these findings indicate that higher levels of O-GlcNAc contributed to sex differences in aortic stiffness and blood pressure during aging possibly by inducing elastin fragmentation. NIH (R00HL151889, RO1DK132948), NIA (K01AG061263), and American Heart Association (AHA-916031) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.