The Association of Different Measures of Insulinaemia with Vascular Risk Factors in Healthy Normoglycaemic Normotensive Non-obese Men and Women

Abstract

Hyperinsulinaemia is said to be a risk factor for cardiovascular disease, but the extent to which different insulinaemic measures are associated with vascular risk factors in ostensibly healthy individuals, and whether they operate independently in men and women, remains uncertain. The association between risk factors and various insulinaemic measures was examined in 148 men and 118 women who were normoglycaemic, normotensive, and non-obese (body mass index in men less than 27, in women less than 25). A 75 g glucose tolerance test was administered after blood sampling for fibrinogen, lipids, lipoproteins and insulin. Insulin was also measured after 1 and 2 hours. Significant univariate correlations (p less than 0.01) were most consistently recorded between insulinaemic measures and fasting serum triglycerides in men and women, whilst systolic blood pressure only correlated with insulinaemia in women, and diastolic blood pressure correlated with fasting and 2 hour insulinaemic measures in men and women. Inconsistent associations were noted with total serum cholesterol in men and women, with high density lipoprotein cholesterol, body mass index, apoprotein B and A1 in men, and with fibrinogen in women. Age was not correlated with any insulinaemic measure in men or women. Differences in vascular risk factors between quintiles of the insulinaemic measures were examined, after correction for body mass index. The dominant association with fasting and post-glucose load insulinaemic measures was with triglycerides, especially in women, with less frequent graded differences between quintiles observed for total cholesterol, and diastolic and systolic blood pressures in men and women. The incidence of other risk factors often only differed in the lowest or highest quintile in comparison to other quintiles, suggesting a threshold rather than a graded effect. Furthermore, differences in HDL cholesterol and apoprotein B were only recorded for top quintiles of post-glucose challenge/integrated insulinaemic measures in men, whilst serum fibrinogen concentrations only differed significantly in women in the top insulinaemic area under the curve quintile. In the absence of additional risk factors such as diabetes, hypertension and obesity, insulinaemic measures are not consistently related to blood pressure and measures of lipid metabolism and coagulation, and are thus a weak predictor of other cardiovascular risk factors. The vascular risk profile associated with insulin appears somewhat different in apparently healthy men and women.