Ambulatory blood pressure and components of the metabolic syndrome in the population : With reference to the renin-angiotensin system, IgF-I, IGFBP-1, neuropentide Y, and leptin

Sammanfattning: The term "the metabolic syndrome" has been given to the constellation of insulin resistance, high blood pressure and hyperlipidemia. In western countries it is strongly associated with obesity and atherosclerosis. The cause of the metabolic syndrome is, however, incompletely understood. Ambulatory blood pressure (ABP) is devoid of the so called white-coat effect (WCE) of clinic BP recordings and might thus better estimate the actual BP-load. This is a descriptive study of the renin-angiotensin system, IGF-I, IGFBP-1, neuropeptide Y, and leptin and their relations to ABP and components of the metabolic syndrome.A population-based study on 224 subjects 18-70 years old, evenly age-distributed and randomly selected from the population of Linköping, Sweden, was performed. This group was the result of a participation rate of 67%. Venous blood was drawn at 0800 a.m. and clinic BP was recorded as well as anthropometric data such as height and weight. A spacelab ABP recorder was applied. ABP reference data were calculated. It was found that clinic BP rose more steeply with age than did ABP and that predetermined day/night intervals causedmisclassification of the diurnal BP variation. The relation of the WCE, defined as the clinic BP minus daytime ABP, was shown to be positively correlated with the levels of plasma cortisol and only weakly to levels of neuropeptide Y. The renin-angiotensin system was decribed in thepopulation. It was shown that the levels of plasma renin-activity (PRA) were affected by age and oestrogen-medication, although this was not the case for plasma immuno-reactive active renin (IRR). Neither PRA nor IRR showed any age-independent correlations to BP. Refererence values were given for IGF-I and IGFBP-1. It was found that IGF-I declined with age and that it"'s binding protein, IGFBP-1, increased with age. The relations of neuropeptide Y, a BP-elevating and appetite-stimulating polypeptide, to the components of the metabolicsyndrome was described. Although no significant cotTelations were found between plasma neuropeptide Y and BP, body-mass-index (BMI) or C-peptide in either gender, a positive correlation was found between both total and LDL cholesterol and neuropeptide Y in women,but not in men. The levels of the anorexogenic substance leptin was shown to correlate positively with BMI and C-peptide in both genders in the studied population. Leptin correlated negatively with testosterone levels in men. Ten OH-deficient subjects were shown to have higher levels of leptin than controls matched for BM! and gender from the population-study. Substitution of GH lowered the levels of leptin.Data from this population-based study will be valuable in the further evaluation of the components of the metabolic syndrome in different populations and in diseases other than OH-deficiency.