Patients with diet-induced obesity and type 2 diabetes are at greater risk for developing cardiovascular complications. An important complication is impaired blood vessel function. In a clinically relevant murine model of diet-induced obesity we showed that exposure to elevated free fatty acids (FFAs) reduces nitric oxide (NO) bioavailability leading to arterial dysfunction. My 2007 R15 sought to determine whether the signaling link between elevated FFAs and impaired NO bioavailability involves the lipid metabolite ceramide. Inhibition of ceramide synthesis with myriocin, or heterozygous deletion of dihydroceramide desaturase, an enzyme which catalyzes ceramide synthesis, prevented endothelial dysfunction and systemic hypertension, and preserved endothelial NO synthase (eNOS) phosphorylation in arteries from fat-fed mice. Molecular mechanisms whereby ceramide might lower NO bioavailability were examined using cultured endothelial cells. Palmitate induced repression of basal and agonist-stimulated eNOS phosphorylation, eNOS dimer formation, and NO production were restored following inhibition of ceramide synthesis. The ceramide-induced impairment of eNOS phosphorylation or dimer formation, respectively, was not the result of impaired kinase-mediated eNOS phosphorylation or superoxide anion-mediated peroxynitrite formation. [Instead, ceramide causes protein phosphatase 2A (PP2A) to associate directly with the eNOS/Akt complex, and this is concurrent with decreased basal and agonist-stimulated eNOS phosphorylation. New data obtained since the last submission suggest that PP2A attenuates eNOS phosphorylation by preventing phosphorylation of the pool of Akt that colocalizes with eNOS and / or by directly dephosphorylating eNOS.] In this renewal, Aim 1 will test the hypothesis that PP2A associates with and disrupts the Akt-Hsp90-eNOS complex as a consequence of de novo ceramide synthesis leading to impaired basal and agonist-stimulated eNOS phosphorylation.
Aim 2 will test the hypothesis that ceramide relieves the association of inhibitor 2 of PP2A (I2PP2A) with PP2A such that PP2A can translocate to the membrane and associate with eNOS.
Aim 3 will test the hypothesis that ceramide-induced, PP2A-mediated vascular dysfunction occurs in mice with diet-induced obesity. Results from these studies will provide mechanistic insight linking endogenous vascular ceramide biosynthesis to cardiovascular defects in a murine model of diet-induced obesity and type 2 diabetes, and present new targets for the treatment of vascular dysfunction in these prevalent conditions. Support for our research via the NIH R15 mechanism has provided >35 undergraduate researchers with valuable experience and each has continued to pursue an advanced degree in the biomedical sciences.

Public Health Relevance

Obesity can lead to type 2 diabetes and cardiovascular complications. Our research is focused on determining the mechanisms whereby obesity impairs blood vessel function. We will determine the mechanism whereby the fat metabolite ceramide impairs eNOS enzyme activity and precipitates arterial dysfunction.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Academic Research Enhancement Awards (AREA) (R15)
Project #
Application #
Study Section
Hypertension and Microcirculation Study Section (HM)
Program Officer
Maric-Bilkan, Christine
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Utah
Other Domestic Higher Education
Salt Lake City
United States
Zip Code
Bharath, Leena P; Mueller, Robert; Li, Youyou et al. (2014) Impairment of autophagy in endothelial cells prevents shear-stress-induced increases in nitric oxide bioavailability. Can J Physiol Pharmacol 92:605-12
Bosse, John D; Lin, Han Yi; Sloan, Crystal et al. (2013) A low-carbohydrate/high-fat diet reduces blood pressure in spontaneously hypertensive rats without deleterious changes in insulin resistance. Am J Physiol Heart Circ Physiol 304:H1733-42
Symons, J David (2013) Opportunity "nox": a novel approach to preventing endothelial dysfunction in the context of insulin resistance. Diabetes 62:1818-20
Symons, J David; Abel, E Dale (2013) Lipotoxicity contributes to endothelial dysfunction: a focus on the contribution from ceramide. Rev Endocr Metab Disord 14:59-68
Larson, Abigail J; Symons, J David; Jalili, Thunder (2012) Therapeutic potential of quercetin to decrease blood pressure: review of efficacy and mechanisms. Adv Nutr 3:39-46
Symons, J David; Hu, Ping; Yang, Ying et al. (2011) Knockout of insulin receptors in cardiomyocytes attenuates coronary arterial dysfunction induced by pressure overload. Am J Physiol Heart Circ Physiol 300:H374-81
Tanner, Jason M; Kearns, Devin T; Kim, Bum Jun et al. (2010) Fasting-induced reductions in cardiovascular and metabolic variables occur sooner in obese versus lean mice. Exp Biol Med (Maywood) 235:1489-97
Symons, J David; McMillin, Shawna L; Riehle, Christian et al. (2009) Contribution of insulin and Akt1 signaling to endothelial nitric oxide synthase in the regulation of endothelial function and blood pressure. Circ Res 104:1085-94
Zhang, Quan-Jiang; McMillin, Shawna L; Tanner, Jason M et al. (2009) Endothelial nitric oxide synthase phosphorylation in treadmill-running mice: role of vascular signalling kinases. J Physiol 587:3911-20
Soesanto, Will; Lin, Han-Yi; Hu, Eric et al. (2009) Mammalian target of rapamycin is a critical regulator of cardiac hypertrophy in spontaneously hypertensive rats. Hypertension 54:1321-7