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Interactions Between Endothelin and Nitric Oxide in the Regulation of Vascular Tone in Obesity and Diabetes
Ist Teil von
Diabetes (New York, N.Y.), 2004-08, Vol.53 (8), p.2060-2066
Ort / Verlag
Alexandria, VA: American Diabetes Association
Erscheinungsjahr
2004
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
Interactions Between Endothelin and Nitric Oxide in the Regulation of Vascular Tone in Obesity and Diabetes
Kieren J. Mather 1 ,
Amale Lteif 1 ,
Helmut O. Steinberg 1 and
Alain D. Baron 1 2
1 Division of Endocrinology & Metabolism, Indiana University School of Medicine, Indianapolis, Indiana
2 Amylin Pharmaceuticals, San Diego, California
Address correspondence and reprint requests to Kieren J. Mather, MD, FRCPC, Division of Endocrinology & Metabolism, Department
of Medicine, Indiana University School of Medicine, CL459, 541 North Clinical Dr., Indianapolis, IN 46202. E-mail: kmather{at}iupui.edu
Abstract
Endothelial dysfunction reflects an imbalance of vasodilators and vasoconstrictors. Endogenous endothelin activity seems to
be increased in human obesity and type 2 diabetes, and cellular studies suggest that this factor may itself reduce bioavailable
nitric oxide (NO). We studied 20 lean, 20 obese, and 14 type 2 diabetic individuals under three protocols, measuring leg vascular
responses to intra-arterial infusions of N G -monomethyl- l -arginine ( l -NMMA; an inhibitor of NO synthase) alone or in combination with BQ123 (an antagonist of type A endothelin receptors) or phentolamine
(used as a control vasodilator). NO synthase inhibition alone (study 1) produced an ∼40% increase in leg vascular resistance
(LVR) in all three participant groups, which was not statistically different across groups (increase in LVR: lean, 135 ± 28;
obese, 140 ± 32; type 2 diabetic, 184 ± 51 units; NS). By design, BQ123 at the infused rate of 3 μmol/min produced equivalent
∼35% reductions in LVR across groups. The subsequent addition of l -NMMA produced a greater increase in LVR among obese participants than lean or type 2 diabetic participants (study 2: lean,
182 ± 48; obese, 311 ± 66; type 2 diabetic, 186 ± 40; P = 0.07). Compared with study 1, the effect of l -NMMA was magnified by BQ123 in obese participants but not in lean or type 2 diabetic participants ( P = 0.005, study 1 vs. 2; P = 0.03 for group effect). Phentolamine (75 mg/min) produced vasodilation in obese participants comparable to that seen with
BQ123 but failed to augment the l -NMMA response. Endothelin antagonism unmasks or augments NO synthesis capacity in obese but not type 2 diabetic participants.
This suggests that impaired NO bioavailability as a result of endogenous endothelin may contribute to endothelial dysfunction
in obesity, in addition to direct vasoconstrictor effects of endothelin. In contrast, endothelin antagonism alone is insufficient
to restore impaired NO bioavailability in diabetes.
ET, endothelin
LBF, leg blood flow
l-NMMA, NG-monomethyl-l-arginine
LVR, leg vascular resistance
NOS, nitric oxide synthase
Footnotes
Accepted May 4, 2004.
Received January 26, 2004.
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