Impact of INsulin Sensitivity on Cardiovascular Risk Markers During 10-20 Years of FOllow-up

In 1988 Reaven described a syndrome designed "syndrome X" based on the clustering of resistance to insulin-stimulated glucose uptake, hyperinsulinaemia, hyperglycaemia, increased triglycerides, decreased high-density lipoprotein (HDL) cholesterol and high blood pressure and proposed insulin resistance as the common feature and the aetiology of the syndrome. Later obesity and the sympathetic nervous system have been proposed as pathogenic factors of the metabolic syndrome, and still major controversy exists regarding its precise aetiology and different definitions of metabolic syndrome are also discussed.

Insulin resistance is a growing epidemic concern in both industrialized and developing countries. It is one of the components of the metabolic syndrome, and plays an important role in the pathogenesis of type 2 diabetes. In view of the predicted increase in the number of diabetic patients during the coming decades, further information about risk factors and pathophysiology of diabetes are of utmost importance for early detection and possible prevention and early treatment from both a medical and a financial perspective. Our research group has for decades studied the pathophysiology of insulin resistance, hypertension, sympathoadrenal hyperreactivity and dyslipidaemia. We have also recently finished a long-term follow up study of subjects based on their cardiovascular and sympathetic responses to mental stress.

During 1991-2002 healthy young men recruited from the military enlistments in the Oslo/Akershus area were examined at Center of Cardiovascular and Renal Research, Division of Medicine, Oslo University Hospital, Ullevål. Young, healthy men, mean age of 21, were examined using the hyperinsulinaemic isoglycaemic glucose clamp technique, which is the gold standard to assess insulin sensitivity. The present study aims to re-examine these subjects in order to investigate the influence of insulin sensitivity on development of cardiovascular risk factors and diabetes. We therefore have a unique opportunity to perform a true, long-term follow-up study of a homogenous sample of subjects of same race and gender which may provide new insights into various pathophysiological mechanisms in diabetes and cardiovascular disease including elucidating the connections between insulin resistance, changes in parameters of body build, blood pressure and sympathetic over-activity. Clarifying these mechanisms are of direct importance for the entire population. There has to our knowledge not been any previous long-term follow-up on subjects based on their insulin resistance measured with this gold standard technique.

We now want to re-examine the same subject to investigate the influence of insulin sensitivity on development of cardiovascular risk factors like blood pressure, heart rate, body build (weight, BMI, waist-hip ration, skinfold thickness), reduced insulin sensitivity, diabetes mellitus, dyslipidaemia, and sympathoadrenal activity or manifest cardiovascular disease among young men during 10-20 years of follow-up.