News Article
Intensive Insulin Therapy Cuts Hypertension Risk in Type 1 Diabetes
Intensive insulin therapy decreases the risk for incident hypertension by 20% in patients with type 1 diabetes, according to a report in the Sept. 22 issue of the Archives of Internal Medicine.
Intensive insulin therapy appears to exert its antihypertensive effect by improving glycemic control, rather than by other mechanisms, reported Dr. Ian H. de Boer of the University of Washington, Seattle, and his associates.
"These results strongly suggest that hyperglycemia plays a role in the pathogenesis of hypertension in type 1 diabetes mellitus," the investigators noted.
Until now, the close correlation between diabetes and hypertension usually has been attributed to underlying obesity, insulin resistance, and hyperinsulinemia. The long-term effect of hyperglycemia on blood pressure has not been understood, Dr. de Boer and his associates said.
They studied the development of hypertension using data from the multicenter Diabetes Control and Complications Trial (DCCT), which ran from 1983 to 1993, and its extension, the Epidemiology of Diabetes Intervention and Complications (EDIC) study, which ran from 1993 through 2005. In these studies, 1,375 subjects aged 13-39 years at enrollment were randomly assigned to receive either conventional or intensive insulin therapy. They were closely followed for a median of 16 years, with frequent measurements of blood pressure and other relevant clinical characteristics.
A total of 630 subjects developed incident hypertension. Intensive insulin therapy reduced the overall long-term incidence of hypertension by 20%. Subject age, race, body mass index, and blood pressure at baseline did not influence the antihypertensive effects of the treatment.
"The salutary effect of intensive insulin therapy occurred in a delayed fashion. During the DCCT itself, there was little or no blood pressure benefit to intensive insulin therapy. In contrast, during the EDIC study follow-up, participants who had previously been assigned to intensive insulin therapy were at lower risk for developing hypertension," Dr. de Boer and his associates said (Arch. Intern. Med. 2008;168:1867-73).
This delay "suggests that the protective effect of intensive therapy on blood pressure occurs over a relatively long period, and/or that beneficial effects of glucose lowering are counterbalanced by unmeasured adverse effects in the short term." One such adverse effect is the weight gain associated with intensive insulin therapy, the researchers added.
The exact mechanism by which hyperglycemia leads to hypertension is not yet known. However, hyperglycemia is known to exert detrimental effects on the vascular wall, which lead to vasoconstriction and extracellular matrix deposition. The resulting vascular remodelling is likely to exert little effect at first but to progress over time, they noted.
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