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Show UNDERGRADUATE RESEARCH ABSTRACTS SPRING 200 Bradlee Duncan Jucid Cahoon i Brandon McDonald Mil da Palionyte J. David Symons Contribution from Ceramide to Vascular Dysfunction Bradlee Duncan, Judd Cahoon, Brandon McDonald, Milda Palionyte (J. David Symons) Department of Exercise and Sports Science University of Utah Our laboratory is interested in mechanisms responsible for vascular dysfunction that is associated with diet-induced obesity. To study this, mice consume standard (10% fat; CON) or high-fat chow (45% fat; HF) for 10 weeks. Systemic abnormalities similar to those in patients with type 2 diabetes and the metabolic syndrome are produced in HF vs. CON mice. Furthermore, arteries from HF mice have substantially lower phosphorylat-ed (i.e., activated) endothelial nitric oxide (NO) synthase (eNOS) compared to those obtained from CON animals. eNOS is an enzyme produced by the endothelium that is responsible for NO production and blood vessel relaxation. The focus of this project is to determine whether obesity leads to vascular dysfunction by initiating formation of the sphingolipid ceramide. Rationale for investigating ceramide originates from cell culture studies showing that this sphingolipid inhibits phosphorylation of Akt (an "upstream" modulator of eNOS). Thus, ceramide might decrease eNOS phosphorylation by inhibiting an upstream activator of this enzyme, and ultimately lead to vascular dysfunction. Studies have clearly demonstrated that exogenous application of ceramide reduces vascular function. We can inhibit endogenous formation of this sphingolipid using a drug called myriocin that inhibits the rate-limiting enzyme responsible for ceramide synthesis. 10-week old CON and HF mice were treated with myriocin (0.3mg/kg, intraperitoneal; IP) or vehicle (phosphate buffered saline, PBS; IP) every second day throughout the feeding regimen. At 20-weeks of age HF mice completed a glucose tolerance test (GTT) wherein 1 mg / g glucose is injected IP, blood samples are obtained for 120-min, and the area under the glucose clearance curve (AUC) is calculated. Three days later, arterial tissue was used to assess ceramide content and endothelium-dependent vasorelaxation using acetylcholine (ACh). Preliminary results from 4-6 mice are shown below. CON - PBS HF HF -Myriocin Vascular ceramide (pmol/mg aorta) 17±4 30 ±2 10 ± 1 Fasting glucose (mg/dL) 95.4 ±6.8 121.9 ±7.6 102.4 ±5.1 AUC (min*mg/dL) 15774 ±1225 27874 ± 1378 19818 ±586 ACh evoked vasorelaxation (% relaxation) 83 ±4 61±6 92 ±4 These findings indicate that: 1) vascular ceramide accumulation; 2) hyperglycemia; 3) glucose intolerance; and 4) impaired ACh-evoked vasorelaxation produced by HF feeding are attenuated by myriocin (e.g., HF-myriocin).Thus, metabolic disturbances and vascular dysfunction might be alleviated when ceramide is inhibited. 21 |
