Nutrients 2020 , 12 , 141
9 of 13
resistance is accompanied by diminished vasodilatory function due to reduced NO bioavailability [9]. Additionally, insulin resistance is associated with increased expression of endothelin ‐ 1 [45], which worsens ED by mediating vasoconstriction. Besides lower glycemia, slowly absorbable carbohydrates prevent an excessive postprandial insulin response, particularly in the early postprandial phase, although we could not document this event due to the late timing of blood sampling [31,44,46]. Moreover, a low ‐ GI beverage containing isomaltulose compared to a high ‐ GI beverage led to reduced daylong insulinemia and attenuated insulin resistance after one week of inactivity [30]. Besides metabolic impairment, insulin resistance is associated with vascular resistance [39,47]. Thus, replacing high ‐ GI carbohydrates might positively impact EF through improved insulin sensitivity which, in turn, enhances the vasodilatory effect of insulin. This would be in line with a study by Hurwitz et al. who investigated differences in the endothelial response between IR and IS subjects following the ingestion of high ‐ versus low ‐ carbohydrate meals [48]. In that study, IR subjects, compared to IS subjects, showed a significantly lower FMD already at baseline. Moreover, the authors observed a decline in postprandial FMD following both meals. Independent of the insulin sensitivity status, the decline in postprandial FMD was more pronounced following the high ‐ carbohydrate meal. Also in the present study, we observed a more pronounced decline in postprandial FMD following sucrose intake compared to isomaltulose intake. This was seen in both IS and IR subjects. Yet, data in IR subjects demonstrate a very pronounced FMD drop following sucrose intake, which appeared to be mitigated by isomaltulose. The present data thus indicate that IR persons, i.e., persons whose glucose metabolism is disturbed, could particularly profit from low ‐ GI carbohydrates. Thirdly, the beneficial effects of GLP ‐ 1 on the vascular system in relation to isomaltulose need to be addressed. Due to its slow hydrolysis, isomaltulose enhances GLP ‐ 1 secretion compared to rapidly available carbohydrates in both healthy persons [30,33] and diabetics [49]. GLP ‐ 1 is known to improve insulin sensitivity as well as secretion and, furthermore, some data suggest that GLP ‐ 1 ameliorates EF [50,51]. The insulin ‐ sensitizing and blood glucose ‐ lowering effects of GLP ‐ 1 presumably prevent postprandial oxidative stress and thus could contribute to a mitigation of ED. Strengths and Limitations To our knowledge, the present study is the first comparing FMD following the ingestion of sucrose and low ‐ GI isomaltulose. Considering the fact that today’s diet contains high amounts of high ‐ GI foods, which leads to adverse health effects, the present results are of clinical relevance. Nevertheless, the efficacy study was based on the primary outcome FMD. Hence, blood analysis was limited with regard to the number of time points and intervals chosen, i.e., every 60 min. This most likely contributed to the failure to detect actual blood glucose peaks which are known to occur in the early postprandial phase. The inclusion of further time points in blood analyses and FMD scanning might have provided additional mechanistic insight on the potential associations between blood glucose and insulin levels with EF. Another limitation of this study is the sample size of the subgroup analysis. A higher number of subjects might have allowed the detection of significant differences in FMD related to the subjects’ insulin sensitivity status. 5. Conclusions In our study, we evaluated the efficacy of isomaltulose (Palatinose™) and sucrose loads on endothelial function as assessed by brachial ultrasound flow ‐ mediated dilation. Our findings show that low ‐ GI isomaltulose, compared to sucrose, led to a better preservation of the basal, pre ‐ prandial, endothelial function in the postprandial phase. Particularly, persons with impaired insulin sensitivity seemed to benefit from the slow ‐ release carbohydrate isomaltulose. Replacing sugar with isomaltulose may exert beneficial effects on cardiovascular health as a result of the more balanced and sustained blood glucose profile. The impact of continued isomaltulose consumption on endothelial function merits further investigations.
Powered by FlippingBook