Reduced NO-cGMP signaling contributes to vascular inflammation and insulin resistance induced by high-fat feeding.
OBJECTIVE
Diet-induced obesity (DIO) in mice causes vascular inflammation and insulin resistance that are accompanied by decreased endothelial-derived NO production. We sought to determine whether reduced NO-cGMP signaling contributes to the deleterious effects of DIO on the vasculature and, if so, whether these effects can be blocked by increased vascular NO-cGMP signaling.


RESULTS
By using an established endothelial cell culture model of insulin resistance, exposure to palmitate, 100 micromol/L, for 3 hours induced both cellular inflammation (activation of IKK beta-nuclear factor-kappaB) and impaired insulin signaling via the insulin receptor substrate-phosphatidylinositol 3-kinase pathway. Sensitivity to palmitate-induced endothelial inflammation and insulin resistance was increased when NO signaling was reduced using an endothelial NO synthase inhibitor, whereas endothelial responses to palmitate were blocked by pretreatment with either an NO donor or a cGMP analogue. To investigate whether endogenous NO-cGMP signaling protects against vascular responses to nutrient excess in vivo, adult male mice lacking endothelial NO synthase were studied. As predicted, both vascular inflammation (phosphorylated I kappaB alpha and intercellular adhesion molecule levels) and insulin resistance (phosphorylated Akt [pAkt] and phosphorylated eNOS [peNOS] levels) were increased in endothelial NO synthase(-/-) (eNOS(-/-)) mice, reminiscent of the effect of DIO in wild-type controls. Next, we asked whether the vascular response to DIO in wild-type mice can be reversed by a pharmacological increase of cGMP signaling. C57BL6 mice were either fed a high-fat diet or remained on a low-fat diet for 8 weeks. During the final 2 weeks of the study, mice on each diet received either placebo or the phosphodiesterase-5 inhibitor sildenafil, 10 mg/kg per day orally. In high-fat diet-fed mice, vascular inflammation and insulin resistance were completely prevented by sildenafil administration at a dose that had no effect in mice fed the low-fat diet.


CONCLUSIONS
Reduced signaling via the NO-cGMP pathway is a mediator of vascular inflammation and insulin resistance during overnutrition induced by high-fat feeding. Therefore, phosphodiesterase-5, soluble guanylyl cyclase, and other molecules in the NO-cGMP pathway (eg, protein kinase G) constitute potential targets for the treatment of vascular dysfunction in the setting of obesity.
Rizzo
Norma O
NO
Department of Medicine, University of Washington, Seattle, WA 98109, USA.
Maloney
Ezekiel
E
Pham
Matilda
M
Luttrell
Ian
I
Wessells
Hunter
H
Tateya
Sanshiro
S
Daum
Guenter
G
Handa
Priya
P
Schwartz
Michael W
MW
Kim
Francis
F
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D001018:Aortic Diseases / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism; D004041:Dietary Fats; D004195:Disease Models, Animal; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007249:Inflammation / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology / Q000517:prevention & control; D018836:Inflammation Mediators / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology
D015815:Cell Adhesion Molecules; D004041:Dietary Fats; D004791:Enzyme Inhibitors; D018836:Inflammation Mediators; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D016328:NF-kappa B; D020030:Nitric Oxide Donors; D058986:Phosphodiesterase 5 Inhibitors; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D019308:Palmitic Acid; D009569:Nitric Oxide; D000068677:Sildenafil Citrate; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP