Key result
In STZ-diabetic rats, 1-week high-dose insulin treatment ameliorated endothelial dysfunction and increased aortic expressions of eNOS and VEGF mRNAs.
Why the study?
Does short-term high-dose insulin treatment improve endothelial dysfunction and alter aortic growth factor mRNA expressions in STZ-induced diabetic rats?
Does short-term high-dose insulin treatment improve endothelial dysfunction and alter aortic growth factor mRNA expressions in STZ-induced diabetic rats?
Short-term insulin treatment in diabetic rats ameliorates endothelial dysfunction by inducing overexpression of eNOS and VEGF mRNAs, possibly via upregulated IGF-1 receptors.
Should not yet change insulin practice; hypothesis-generating for vascular effects in diabetes.
We investigated the relationship between the changes in vascular responsiveness and growth factor mRNA expressions induced by 1-wk treatment with high-dose insulin in control and established streptozotocin (STZ)-induced diabetes. Aortas from diabetic rats, but not those from insulin-treated diabetic rats, showed impaired endothelium-dependent relaxation in response to ACh (vs. untreated controls). The ACh-induced nitrite plus nitrate (NOx) level showed no significant difference between controls and diabetics. Insulin treatment increased NOx only in diabetics. In diabetics, insulin treatment significantly increased the aortic expressions of endothelial nitric oxide synthase (eNOS) mRNA and VEGF mRNA. The expression of IGF-1 mRNA was unaffected by diabetes or by insulin treatment. In contrast, the mRNA for the aortic IGF-1 receptor was increased in diabetics and further increased in insulin-treated diabetics. In aortic strips from age-matched control rats, IGF-1 caused a concentration-dependent relaxation. This relaxation was significantly stronger in strips from STZ-induced diabetic rats. These results suggest that in STZ-diabetic rats, short-term insulin treatment can ameliorate endothelial dysfunction by inducing overexpression of eNOS and/or VEGF mRNAs possibly via IGF-1 receptors. These receptors were increased in diabetes, perhaps as result of insulin deficiency.
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Kobayashi et al. (2002) studied Streptozotocin (STZ)-induced diabetes. Insulin vs. Untreated controls and untreated diabetics was evaluated on Vascular responsiveness and growth factor mRNA expressions. In STZ-diabetic rats, 1-week high-dose insulin treatment ameliorated endothelial dysfunction and increased aortic expressions of eNOS and VEGF mRNAs.
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