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)] [(pD(2)) 7.0 +/- 0.1 compared with 6.7 +/- 0.09 CD] and the thromboxane analogue 9,11-dideoxy-9(alpha),11(alpha)-methanoepoxy prostaglandin F-2 alpha (U-46619) [(pD(2)) 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.