Ambulatory Blood Pressure in Type II Diabetes

Both insulin resistance and insulin concentrations correlate with blood pressure in nondiabetic subjects, but there is no consensus on these relations in subjects with non-insulin-dependent diabetes, perhaps because of the use of nonspecific insulin assays and clinic blood pressure measurement. Therefore, we have investigated the relation between ambulatory blood pressure, insulin sensitivity (measured by an insulin sensitivity test), and levels of insulin and its principal precursors, measured by specific assays, in 24 subjects with non—insulin-dependent diabetes. Insulin sensitivity (glucose metabolic clearance rate) correlated strongly with mean 24hour ambulatory systolic blood pressure (r=— .650, P<.001). In contrast, there was no relation between this blood pressure index and fasting levels of insulin (r=.O96, P=NS) or all Along ago as 1923, soon after insulin had become available, Klemperer and Strisower demonstrated that both diabetic and nondiabetic subjects exhibited transient falls in blood pressure after insulin injection. Seventy years after this simple experiment, the relation between insulin and blood pressure is unresolved and remains hotly debated. In the modern era, with the advent of insulin assays, a correlation was first observed between blood pressure and levels of total immunoreactive insulin (IRI), both fasting and stimulated by glucose, in subjects with essential hypertension. Modan et al showed that insulin concentrations correlated with casual blood pressure independently of glucose intolerance and body mass index (BMI) in the general population. Subsequently, both Ferrannini et al* and Shen et al demonstrated that subjects with essential hypertension exhibited resistance to insulin-mediated glucose disposal. Reaven has proposed that insulin resistance leads to compensatory hyperinsulinemia, which, according to various lines of argument, might have a major role in the pathogenesis of essential hypertension. In nondiabetic subjects, insulin resistance is paralleled by increased insulin concentrations, making it difficult to evaluate the relative contribution of either variable to the pathogenesis of hypertension. By conReceived March 1, 1994; accepted in revised form June 2, 1994. From the Department of Medicine, University College London Medical School, Whittington Hospital, and the Department of Cardiology, National Heart and Lung Hospital, Sydney Street, London, UK (C.F.). Correspondence to Jonathan H. Pinkney, Department of Medicine, University College London Medical School, Whittington Hospital, Archway Wing, G Block, Archway Road, London N19 3UA.UK. © 1994 American Heart Association, Inc. insulin-like molecules (r=.O77, P=NS). Dichotomized on 24hour ambulatory systolic blood pressure levels, the hypertensive group was more insulin resistant than the normotensive group (metabolic clearance rate, 3.6 [0.7] versus 6.5 [3.0] mL • kg" • min", P=.0O6), whereas there was no difference in insulin or proinsulin concentrations among the groups. In multiple regression analysis, insulin sensitivity was the major determinant of blood pressure. We conclude that in subjects with non-insulin-dependent diabetes mellitus, blood pressure is related to insulin sensitivity but not to fasting levels of insulin, suggesting that hyperinsulinemia is probably not the mediator of this relation. (Hypertension. 1994;24 J62-367.)