Accomplices of Insulin Resistance in Prehypertension: Aldosterone?
Condition: Hypertension; Insulin Resistance
MeSH terms: Hypertension; Prehypertension; Insulin Resistance
Study type: Observational

Summary: 
      The purposes of the study are to evaluate the relative contributions of insulin resistance
      and renin-angiotensin-aldosterone system to blood pressure (BP) in subjects with
      prehypertension. This is a cross-sectional study. Anthropometric and BP measurements will be
      performed in 50 prehypertensive subjects. The subjects will receive a 75-g oral glucose
      tolerance test and a postural stimulation test for the measurements of insulin resistance,
      plasma rennin concentration and aldosterone level. Log (ISI0,120), an insulin sensitivity
      index from the oral glucose tolerance test, will be calculated. Statistical analyses will be
      performed to compare the degree to which aldosterone and Log (ISI0,120) predicted systolic
      and diastolic BP in these prehypertensive subjects.
    

Detailed description: 
      Background: Prehypertension, a new category of blood pressure (BP) classification introduced
      by The Seven Report of the Joint National Commission (JNC-7) on High BP for individuals with
      systolic BP in the range of 120-139 mmHg or diastolic BP between 80-89 mmHg, is a strong
      predictor for the development of hypertension. Insulin resistance (IR) is reported to be
      associated with prehypertension. Activation of the renin-angiotensin-aldosterone (RAA) system
      is a major player in IR and elevation of high BP.

      Aim: The purposes of the study are to evaluate the interactions of IR-RAA and their relative
      contributions to BP in subjects with prehypertension.

      Design: This is a cross-sectional study. Methods: Anthropometric and BP measurements will be
      performed in 50 prehypertensive subjects. The subjects will receive a 75-g oral glucose
      tolerance test (OGTT) and a postural stimulation test for the measurements of IR, plasma
      rennin concentration (PRC) and aldosterone level. The study participants will be divided into
      three subgroups by tertiles of Log (ISI0,120), an insulin sensitivity index from the OGTT.
      Analysis of variance (ANOVA) will be applied to compare the differences in clinical
      characteristics among the three groups. Univariate analyses of general linear models will be
      used to compare the differences in PRC, aldosterone, and aldosterone/rennin ratio (ARR) in
      postural stimulation tests among the three subgroups, showing effects of confounding
      variables including age, sex, BMI and physical inactivity scores. Repeated-measures ANOVA
      will be used to assess the differences in post-challenge PRC, aldosterone, and ARR responses
      in the OGTT with or without adjustments of the above covariates. Pearson and partial
      correlation procedures will be used to test the correlations of PRC, aldosterone, ARR with
      insulin sensitivity and BP. Multiple linear regression models will be used in an attempt to
      compare the degree to which aldosterone (or ARR) and Log (ISI0,120) predicted systolic and
      diastolic BP in these prehypertensive subjects.

      Expected results and contributions: We hope the study can explore the contribution of the
      IR-RAA interactions to BP in subjects with prehypertension.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Subjects with prehypertension, that is, individuals with systolic blood pressure (BP) in
        the range of 120-139 mmHg or diastolic BP between 80-89 mmHg.
      
Keywords: Insulin Resistance; Hypertension; Blood pressure; Aldosterone; Renin