Epidemiologic and clinical aspects of insulin resistance and hyperinsulinemia

Relationships between blood pressure and lipids in childhood

This review has discussed the potential interrelationships of elevated blood pressure and lipid abnormalities. Most of the data for this review have been collected in adults, but physiologic and genetic effects may have expression in childhood. Clustering of cardiac risk factors may be mediated by increased levels of insulin. These increased levels of insulin may be genetically determined or may be related to obesity. Recognition of the multiple risk factor phenotype is important, because individuals with multiple risk may have a much higher risk of future coronary events than do individuals with single risk factors. Medical therapy of individuals with multiple risk should be more aggressive than for individuals with single risk factors. Physicians should be cautious about therapy in the pediatric setting because of possible interaction between therapeutic agents and risk factors, however.

Marked association of a RFLP for the low density lipoprotein receptor gene with obesity in essential hypertensives

RFLPs at the low density lipoprotein receptor locus (LDLR) display marked linkage disequilibrium between each other. Cross-sectional analysis of a bi-alleleic ApaLI RFLP of LDLR showed that the 9.4- and 6.6-kb alleles were present in similar frequency between a group of 84 Caucasian essential hypertensive (HT) and a group of 96 normotensive subjects whose parents each had a similar blood pressure status at age > or = 50. After subdividing HTs into lean and obese, however, the frequency of the 6.6-kb allele in the 27 HTs with BMI > or = 26 kg/m2 was 0.63, compared with 0.39 for HTs with BMI < 26 (chi 2 = 8.8; P = 0.004). The difference in genotype frequencies was even more striking (chi 2 = 23; P = 0.00008), with a virtual absence of 9.4-kb homozygotes in the obese HT group (1 vs 22). Genetic variation at LDLR (19p13.2) is thus associated with obesity in HT.

Platelet sodium-hydrogen antiport in obese and diabetic black women

In this investigation we correlated platelet Na-H antiport parameters with blood pressure and serum lipids in a sample population of non-insulin-dependent diabetic obese, nondiabetic obese, and nondiabetic nonobese black women. Parameters of the Na-H antiport were examined in aspirin-treated platelets. These parameters were not altered in resting or in thrombin-stimulated platelets of diabetic patients. The activity index of platelet Na-H antiport after thrombin stimulation was positively correlated with the blood pressure (systolic blood pressure, r = 0.5320 and p = 0.0001; diastolic blood pressure, r = 0.5123 and p = 0.0017). Lower high density lipoprotein cholesterol levels were associated with an alkaline shift in the cytosolic pH set point for activation of the Na-H antiport. Highly significant correlations were also observed between the total cholesterol/high density lipoprotein cholesterol ratio and the cytosolic pH set point for activation of the Na-H antiport. These correlations were independent of diabetes or the body mass index. Together, these observations indicate that parameters of platelet Na-H antiport are altered with an increase in blood pressure and a decrease in serum high density lipoprotein cholesterol.

Diabetes mellitus and hypertension

Diabetes mellitus and hypertension are common diseases that coexist at a greater frequency than chance alone would predict. Hypertension in the diabetic individual markedly increases the risk and accelerates the course of cardiac disease, peripheral vascular disease, stroke, retinopathy, and nephropathy. Our understanding of the factors that markedly increase the frequency of hypertension in the diabetic individual remains incomplete. Diabetic nephropathy is an important factor involved in the development of hypertension in diabetics, particularly type I patients. However, the etiology of hypertension in the majority of diabetic patients cannot be explained by underlying renal disease and remains "essential" in nature. The hallmark of hypertension in type I and type II diabetics appears to be increased peripheral vascular resistance. Increased exchangeable sodium may also play a role in the pathogenesis of blood pressure in diabetics. There is increasing evidence that insulin resistance/hyperinsulinemia may play a key role in the pathogenesis of hypertension in both subtle and overt abnormalities of carbohydrate metabolism. Population studies suggest that elevated insulin levels, which often occurs in type II diabetes mellitus, is an independent risk factor for cardiovascular disease. Other cardiovascular risk factors in diabetic individuals include abnormalities of lipid metabolism, platelet function, and clotting factors. The goal of antihypertensive therapy in the patient with coexistent diabetes is to reduce the inordinate cardiovascular risk as well as lowering blood pressure.

Insulin resistance, hyperinsulinemia, and cardiovascular disease. The need for novel dietary prevention strategies

Insulin resistance associated with hyperinsulinemia (metabolic syndrome) emerged in recent years as an important health risk which is present in approximately 25% of the normal population in western industrialized societies. Insulin resistance as assessed for the whole body arises from a reduced glucose utilization of skeletal muscle. If the metabolic syndrome persists over a prolonged period of time, detrimental influences on the cardiovascular system become apparent involving diabetes mellitus, hypertension, and arteriosclerosis. Of particular pathogenic relevance is an unbalanced influence of insulin arising either from a diminished or enhanced insulin action depending on whether the various tissues of the body exhibit a reduced or unchanged insulin sensitivity. Since insulin resistance and hyperinsulinemia appear to be affected by various lifestyle factors, the unique opportunity exists of reducing cardiovascular mortality by correcting this syndrome at a time when degenerative changes have not occurred in the cardiovascular system. Of great importance is the finding that dietary factors can have a modulatory action on insulin sensitivity. In animal experiments, an increased intake of (saturated) fat and refined carbohydrates increased insulin resistance. Since psychosocial distress is expected to be associated with a sustained activation of the sympathoadrenal axis, it is likely also to aggravate the metabolic syndrome. A factor with a beneficial action appears to be physical exercise. In view of the high incidence of cardiovascular diseases, further research on lifestyle factors with an insulin-sensitizing or insulin-desensitizing action is required. Of prime importance is the reevaluation of established dietary recommendations and diets should be designed which take into account the individual cardiovascular risk factor profile.