Bradlee Duncan

Vascular dysfunction that accompanies obesity and insulin resistance may be mediated by lipid metabolites. We sought to determine if vascular ceramide leads to arterial dysfunction and to elucidate the underlying mechanisms. Pharmacological inhibition of de novo ceramide synthesis, using the Ser palmitoyl transferase inhibitor myriocin, and heterozygous deletion of dihydroceramide desaturase prevented vascular dysfunction and hypertension in mice after high-fat feeding. These findings were… Show more

Vascular dysfunction that accompanies obesity and insulin resistance may be mediated by lipid metabolites. We sought to determine if vascular ceramide leads to arterial dysfunction and to elucidate the underlying mechanisms. Pharmacological inhibition of de novo ceramide synthesis, using the Ser palmitoyl transferase inhibitor myriocin, and heterozygous deletion of dihydroceramide desaturase prevented vascular dysfunction and hypertension in mice after high-fat feeding. These findings were recapitulated in isolated arteries in vitro, confirming that ceramide impairs endothelium-dependent vasorelaxation in a tissue-autonomous manner. Studies in endothelial cells reveal that de novo ceramide biosynthesis induced protein phosphatase 2A (PP2A) association directly with the endothelial nitric oxide synthase (eNOS)/Akt/Hsp90 complex that was concurrent with decreased basal and agonist-stimulated eNOS phosphorylation. PP2A attenuates eNOS phosphorylation by preventing phosphorylation of the pool of Akt that colocalizes with eNOS and by dephosphorylating eNOS. Ceramide decreased the association between PP2A and the predominantly cytosolic inhibitor 2 of PP2A. We conclude that ceramide mediates obesity-related vascular dysfunction by a mechanism that involves PP2A-mediated disruption of the eNOS/Akt/Hsp90 signaling complex. These results provide important insight into a pathway that represents a novel target for reversing obesity-related vascular dysfunction. Show less

Ceramide accumulation in vascular smooth muscle might contribute to obesity-related arterial dysfunction and hypertension. To test this hypothesis, mice were treated with myriocin (M), an inhibitor of an enzyme required for ceramide biosynthesis (i.e., serine palmitoyltransferase). 10-week old mice consumed chow containing 45% (HF, n=20) or 10% (Con, n=20) fat ± M (0.3 mg/kg i.p., n=10) or vehicle (V; saline i.p., n=10) for 14 weeks. Mean (MAP), systolic (SBP), and diastolic (DBP) blood… Show more

Ceramide accumulation in vascular smooth muscle might contribute to obesity-related arterial dysfunction and hypertension. To test this hypothesis, mice were treated with myriocin (M), an inhibitor of an enzyme required for ceramide biosynthesis (i.e., serine palmitoyltransferase). 10-week old mice consumed chow containing 45% (HF, n=20) or 10% (Con, n=20) fat ± M (0.3 mg/kg i.p., n=10) or vehicle (V; saline i.p., n=10) for 14 weeks. Mean (MAP), systolic (SBP), and diastolic (DBP) blood pressures then were recorded via telemetry for 6 x 24-h periods followed by excision of the aorta and femoral arteries. Vascular ceramide (pmol ceramide/mg aorta) increased (p<0.05) from 17±4 in Con-V mice to 30±3 in HF-V animals, and was suppressed in HF-M animals (10±1). Elevated (*p<0.05) MAP, SBP, and DBP in HF-V vs. Con-V mice was prevented in HF-M animals. Values in the Table represent the mean±SE of 6 dark/active cycles. Impaired (*p<0.05) acetylcholine (ACh)-evoked vasorelaxation (wire-myography) in femoral arteries from HF-V vs. Con-V mice was prevented in HF-M animals. Sodium-nitroprusside-evoked vasorelaxation was similar among groups. ACh values represent % vasorelaxation. Show less