High-fat diet increases O-GlcNAc levels in cerebral arteries: a link to vascular dysfunction associated with hyperlipidaemia/obesity?

Obesity and high fat intake induce alterations in vascular function and structure. Aberrant O -GlcNAcylation ( O -GlcNAc) of vascular proteins has been implicated in vascular dysfunction associated with cardiovascular and metabolic diseases. In the present study, we tested the hypothesis that high-fat diet (HFD)-mediated increases in O -GlcNAc-modified proteins contribute to cerebrovascular dysfunction. O -GlcNAc-protein content was increased in arteries from male Wistar rats treated with a HFD (45% fat) for 12 weeks compared with arteries from rats on control diet (CD). HFD augmented body weight [(g) 550±10 compared with 502±10 CD], increased plasma triacylglycerols [(mg/dl) 160±20 compared with 95±15 CD] and increased contractile responses of basilar arteries to serotonin [5-hydroxytryptamine (5-HT)] [(pD2) 7.0±0.1 compared with 6.7±0.09 CD] and the thromboxane analogue 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F2α (U-46619) [(pD2) 7.2±0.1 compared with 6.8±0.09 CD]. Of importance, increased levels of O -GlcNAc [induced by 24 h-incubation of vessels with a potent inhibitor of O -GlcNAcase (OGA), O -(2-acetamido-2-deoxy-D-glucopyranosylidene)amino- N -phenylcarbamate (PugNAc)] increased basilar artery contractions in response to U-46619 [(pD2) 7.4±0.07 compared with 6.8±0.08 CD] and 5-HT [(pD2) 7.5±0.06 compared with 7.1±0.1 CD]. Vessels from rats on the HFD for 12 weeks and vessels treated with PugNAc displayed increased phosphorylation of p38 (Thr180/182) and extracellular signal-regulated kinase 1/2 (Erk1/2) (Ser180/221). Increased 5HT-induced contractions in arteries from rats on the HFD or in arteries incubated with PugNAc were abrogated by mitogen-activated protein kinase (MAPK) inhibitors. Our data show that HFD augments cerebrovascular O -GlcNAc and this modification contributes to increased contractile responses and to the activation of the MAPK pathway in the rat basilar artery. * CD, : control diet; E max, : maximal effect generated by the agonist; Erk1/2, : extracellular signal-regulated kinase 1/2; ET-1, : endothelin-1; HBP, : hexosamine biosynthesis pathway; HFD, : high-fat diet; 5-HT, : 5-hydroxytryptamine; MAPK, : mitogen-activated protein kinase; MCAO, : middle cerebral artery occlusion; OGA, : O -GlcNAcase; O -GlcNAc, : O -GlcNAcylation; PE, : phenylephrine; PugNAc, : O -(2-acetamido-2-deoxy-D-glucopyranosylidene)amino- N -phenylcarbamate; SBP, : systolic blood pressure; U-46619, : thromboxane analogue 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F2α