title: Altered mechanism of adenosine-induced coronary arteriolar dilation in early-stage metabolic syndrome.
abstract: Onset of the combined metabolic syndrome (MetS) is a complex progressive process involving numerous cardiovascular risk factors. Although patients with established MetS exhibit reduced coronary flow reserve and individual components of the MetS reduce microvascular vasodilation, little is known concerning the impact of early-stage MetS on the mechanisms of coronary flow control. Therefore, we tested the hypothesis that coronary arteriolar dilation to adenosine is attenuated in early-stage MetS by reduced A2 receptor function and diminished K+ channel involvement. Pigs were fed control or high-fat/cholesterol diet for 9 weeks to induce early-stage MetS. Coronary atheroma was determined in vivo with intravascular ultrasound. In vivo coronary dilation was determined by intracoronary adenosine infusion. Further, apical coronary arterioles were isolated, cannulated and pressurized to 60 cmH2O for in vitro pharmacologic assessment of adenosine dilation. Coronary atheroma was not different between groups, indicating early-stage MetS. Coronary arteriolar dilation to adenosine (in vivo) and 2-chloroadenosine (2-CAD; in vitro) was similar between groups. In control arterioles, 2-CAD-mediated dilation was reduced only by selective A(2A) receptor inhibition, whereas only dual A(2A/2B) inhibition reduced this response in MetS arterioles. Arteriolar A(2B), but not A(2A), receptor protein expression was reduced by MetS. Blockade of voltage-dependent K+ (K(v)) channels reduced arteriolar sensitivity to 2-CAD in both groups, whereas ATP-sensitive K+ (K(ATP)) channel inhibition reduced sensitivity only in control arterioles. Our data indicate that the mechanisms mediating coronary arteriolar dilation to adenosine are altered in early-stage MetS prior to overt decrements in coronary vasodilator reserve.
authors.affiliation: E102 Vet Med Bldg, Dept. of Biomedical Sciences, University of Missouri, Columbia, MO 65211, USA. benders@missouri.edu
authors.forename: Shawn B
authors.initials: SB
authors.lastname: Bender
authors.forename: Johnathan D
authors.initials: JD
authors.lastname: Tune
authors.forename: Lena
authors.initials: L
authors.lastname: Borbouse
authors.forename: Xin
authors.initials: X
authors.lastname: Long
authors.forename: Michael
authors.initials: M
authors.lastname: Sturek
authors.forename: M Harold
authors.initials: MH
authors.lastname: Laughlin
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D058908:Adenosine A2 Receptor Agonists; D000818:Animals; D001160:Arterioles / Q000378:metabolism / Q000503:physiopathology; D002318:Cardiovascular Diseases / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D002784:Cholesterol / Q000494:pharmacology; D003326:Coronary Circulation / Q000187:drug effects*; D004041:Dietary Fats / Q000494:pharmacology; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000378:metabolism; D043705:Receptor, Adenosine A2A / Q000378:metabolism; D012307:Risk Factors; D013552:Swine; D013556:Swine, Miniature; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D058908:Adenosine A2 Receptor Agonists; D004041:Dietary Fats; D024642:Potassium Channels, Voltage-Gated; D043705:Receptor, Adenosine A2A; D014665:Vasodilator Agents; D002784:Cholesterol; D000241:Adenosine