Tetrahydrobiopterin increases insulin sensitivity in patients with type 2 diabetes and coronary heart disease.
Tetrahydrobiopterin (BH(4)) is an essential cofactor of nitric oxide synthase that improves endothelial function in diabetics, smokers, and patients with hypercholesterolemia. Insulin resistance has been suggested as a contributing factor in the development of endothelial dysfunction via an abnormal pteridine metabolism. We hypothesized that BH(4) would restore flow-mediated vasodilation (FMD, endothelial-dependent vasodilation), which may affect insulin resistance in type 2 diabetic patients. Thirty-two subjects (12 type 2 diabetic subjects, 10 matched nondiabetic subjects, and 10 healthy unmatched subjects) underwent infusion of BH(4) or saline in a random crossover study. Insulin sensitivity index (S(I)) was measured by hyperinsulinemic isoglycemic clamp. FMD was measured using ultrasonography. BH(4) significantly increased S(I) in the type 2 diabetics [3.6 +/- 0.6 vs. 4.9 +/- 0.7 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P < 0.05], while having no effects in nondiabetics [8.9 +/- 1.1 vs. 9.0 +/- 0.9 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P = 0.92] or in healthy subjects [17.5 +/- 1.6 vs. 18 +/- 1.8 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P = 0.87]. BH(4) did not affect the relative changes in brachial artery diameter from baseline FMD (%) in type 2 diabetic subjects (2.3 +/- 0.8 vs. 1.8 +/- 1.0%, P = 0.42), nondiabetic subjects (5.3 +/- 1.1 vs. 6.6 +/- 0.9%, P = 0.32), or healthy subjects (11.9 +/- 0.6 vs. 11.0 +/- 1.0%, P = 0.48). In conclusion, BH(4) significantly increases insulin sensitivity in type 2 diabetic patients without any discernible improvement in endothelial function.
Nyström
Thomas
T
Dept. of Internal Medicine, Karolinska Institute, Stockholm South Hospital, Södersjukhuset, Stockholm SE-118 83, Sweden. thomas.nystrom@sos.sll.se
Nygren
Arne
A
Sjöholm
Ake
A
D001708:Biopterins / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism*; D003067:Coenzymes / Q000494:pharmacology / Q000502:physiology; D003327:Coronary Disease / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism*; D003925:Diabetic Angiopathies / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D012016:Reference Values; D014664:Vasodilation / Q000502:physiology*
D001786:Blood Glucose; D003067:Coenzymes; D007328:Insulin; D001708:Biopterins; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C003402:sapropterin