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BackgroundPrevious studies have demonstrated that postprandial hyperglycemia attenuates brachial artery flow-mediated dilation (FMD) in prediabetic patients, in diabetic patients, and even in normal subjects. We have previously reported that postprandial hyperinsulinemia also attenuates FMD. In the present study we evaluated the relationship between different degrees of postprandial attenuation of FMD induced by postprandial hyperglycemia and hyperinsulinemia and differences in ingested carbohydrate content in non-diabetic individuals.MethodsThirty-seven healthy subjects with no family history of diabetes were divided into 3 groups: a 75-g oral glucose loading group (OG group) (n = 14), a test meal group (TM group) (n = 12; 400 kcal, carbohydrate content 40.7 g), and a control group (n = 11). The FMD was measured at preload (FMD0) and at 60 minutes (FMD60) and 120 (FMD120) minutes after loading. Plasma glucose (PG) and immunoreactive insulin (IRI) levels were determined at preload (PG0, IRI0) and at 30 (PG30, IRI30), 60 (PG60, IRI60), and 120 (PG120, IRI120) minutes after loading.ResultPercentage decreases from FMD0 to FMD60 were significantly greater in the TM group (−21.19% ± 17.90%; P < 0.001) and the OG group (−17.59% ± 26.64%) than in the control group (6.46% ± 9.17%; P < 0.01), whereas no significant difference was observed between the TM and OG groups. In contrast, the percentage decrease from FMD0 to FMD120 was significantly greater in the OG group (−18.91% ± 16.58%) than in the control group (6.78% ± 11.43%; P < 0.001) or the TM group (5.22% ± 37.22%; P < 0.05), but no significant difference was observed between the control and TM groups. The FMD60 was significantly correlated with HOMA-IR (r = −0.389; P < 0.05). In contrast, FMD120 was significantly correlated with IRI60 (r = −0.462; P < 0.05) and the AUC of IRI (r = −0.468; P < 0.05). Furthermore, the percentage change from FMD0 to FMD120 was significantly correlated with the CV of PG (r = 0.404; P < 0.05), IRI60 (r = 0.401; p < 0.05) and the AUC of IRI (r = 0.427; P < 0.05). No significant correlation was observed between any other FMDs and glucose metabolic variables.ConclusionDifferences in the attenuation of postprandial FMD induced by different postprandial insulin levels may occur a long time postprandially but not shortly after a meal.

Our study showed that oral glucose loading attenuates FMD and shortens elapsed time at the maximum after-hyperaemia diameter, and the effect of glucose fluctuation on atherosclerosis in individuals with normal glucose tolerance remains despite only the attenuation of endothelial function.

We evaluated the effect of sitagliptin on vascular endothelial function in Japanese type 2 diabetes patients without cardiovascular disease. Subjects included 24 Japanese type 2 diabetes patients without cardiovascular disease. This study was a prospective, open-label, randomized clinical trial. We divided the study subjects into 2 groups: subjects who received sitagliptin 50 mg daily (sitagliptin group, n = 12) and subjects who did not receive sitagliptin (control group, n = 12). Brachial artery flow-mediated dilation (FMD) was measured after overnight fasting. Sitagliptin administration was initiated at 1 month after enrollment in study (baseline). FMD and level of biochemical variables in the sitagliptin and control groups were measured at baseline and 3 months from baseline (3 months). We evaluated the effect of sitagliptin on vascular endothelial function by measuring FMD. FMD at 3 months was significantly higher in the sitagliptin group than in the control group (5.36% ± 2.18% vs 3.41% ± 2.29%, P = 0.040), while FMD at baseline was not significantly different between the 2 groups. In addition, FMD of the sitagliptin group at 3 months was significantly higher than that at baseline (5.36% ± 2.18% vs 3.67% ± 2.30%, P = 0.004), while no significant differences were observed in the FMD of the control group during the study period. The change in the adiponectin from baseline to 3 months was significantly higher in the sitagliptin group than that in the control group (0.82 ± 2.18 μg/mL vs 0.01 ± 0.55 μg/mL, P = 0.039). Sitagliptin improves vascular endothelial function of the brachial artery in Japanese type 2 diabetes patients without cardiovascular disease. Furthermore, elevation of adiponectin may induce reduction of endothelial dysfunction in type 2 diabetes patients treated with sitagliptin

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