Impairment of endothelium-dependent ACh-induced relaxation in aorta of diabetic db/db mice--possible dysfunction of receptor and/or receptor-G protein coupling.
Diabetes is a risk factor of ischemic heart disease, cerebral ischemia, and atherosclerosis, in which endothelial dysfunction plays a role in the pathogenesis. We examined vascular responses in the aorta of pre-diabetic db/db mice with normoglycemia, hyperlipidemia, and hyperinsulinemia (6 weeks old), and diabetic db/db mice with hyperglycemia, hyperlipidemia, and hyperinsulinemia (11 weeks old) in comparison with age-matched non-diabetic db/+ mice. Prostaglandin F2alpha (PGF2alpha)-induced contraction was significantly enhanced in the aorta of diabetic but not pre-diabetic db/db mice compared to age-matched non-diabetic db/+ mice. Acetylcholine (ACh), adenosine-5'-diphosphate (ADP), NaF, a G protein activator and A-23187, a Ca-ionophore, caused endothelium-dependent and nitric oxide (NO)-mediated relaxation, and sodium nitroprusside (SNP), an NO donor, caused endothelium-independent relaxation in the pre-contracted aorta of db/db mice. Maximal endothelium-dependent ACh-induced relaxation was reduced in diabetic but not pre-diabetic db/db mice compared to age-matched db/+ mice, while maximal SNP-induced relaxation was not different between diabetic and non-diabetic mice. ACh-induced relaxation in diabetic db/db mice was not affected by ozagrel, a thromboxane A2 (TXA2) synthetase inhibitor, or acetylsalicylic acid (aspirin), a cyclooxygenase inhibitor, suggesting no involvement of endogenous TXA2 or prostanoids in the reduction of relaxation. Maximal endothelium-dependent ADP-, A-23187-, and NaF-induced relaxation was not reduced in diabetic db/db mice. EC50 values for ACh- and SNP-induced relaxation were increased in diabetic but not pre-diabetic db/db mice, suggesting decreases in sensitivity to NO in diabetic mice. Two-week treatment with KV-5070, a PPARgamma agonist, lowered plasma glucose, triglyceride (TG), and insulin but not cholesterol, and reversed the reduced ACh-induced relaxation. In conclusion, ACh-induced endothelium-dependent relaxation is impaired in diabetic db/db mice, probably due to the dysfunction of ACh receptors and/or receptor-G protein coupling. Endothelial dysfunction was not genetic and was considered to be initiated primarily by hyperglycemia, and was improved by anti-diabetic treatment with a PPARgamma agonist.
Miike
Tomohiro
T
Research Laboratories, Kyoto Pharmaceutical Industries, Ltd., Kyoto, 604-8444, Japan.
Kunishiro
Kazuyoshi
K
Kanda
Mamoru
M
Azukizawa
Satoru
S
Kurahashi
Kazuyoshi
K
Shirahase
Hiroaki
H
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000503:physiopathology; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000378:metabolism*; D006943:Hyperglycemia / Q000503:physiopathology; D006946:Hyperinsulinism / Q000503:physiopathology; D006949:Hyperlipidemias / Q000503:physiopathology; D008297:Male; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D047495:PPAR gamma / Q000819:agonists; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D044005:Tetrahydroisoquinolines / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
C533283:KV-5070; D047495:PPAR gamma; D011950:Receptors, Cholinergic; D043562:Receptors, G-Protein-Coupled; D044005:Tetrahydroisoquinolines; D014665:Vasodilator Agents; D009569:Nitric Oxide; D000109:Acetylcholine