Antipsychotics and Blood Vessel Function
Condition: Bipolar Disorder; Schizophrenia
MeSH terms: Schizophrenia; Bipolar Disorder
Study type: Observational

Summary: 
      Over the last decade, second generation antipsychotics have been increasingly utilized. Since
      their introduction, however, atypical antipsychotics have been increasingly associated with
      significant metabolic complications including hyperlipidemia, insulin resistance/diabetes
      mellitus, and obesity. These metabolic complications increase the risk for cardiovascular
      disease in populations with an already elevated risk.

      The initial goal of the proposed study is to identify early signs of endothelial dysfunction
      and vascular disease in those treated with atypical antipsychotics. The identification of
      early signs of vascular disease may further link metabolic complications with any
      cardiovascular risk. Demonstration of changes in vascular function associated with atypical
      antipsychotics represents an important identifiable intermediate of more long-term
      cardiovascular risk.

      The second goal of the proposed study is to identify genetic factors that may be associated
      with the development of cardiovascular disease, which can later serve as a guide to predict
      risk. Accurate prediction of risk may facilitate the future development of an empirical,
      risk-based, individualized selection process for antipsychotic medications.

      Aim 1: To quantify the role of antipsychotic-induced metabolic complications on the
      development of vascular disease using measures of endothelial function.

      Hypothesis 1: Atypical antipsychotics will lead to greater impairments in endothelial
      function, evidenced by decreased flow-mediated dilation from baseline measures and compared
      with changes over time in controls. Medication-induced metabolic complications will be
      temporally associated with these impairments in endothelial function.

      Aim 2: To investigate the role of candidate pharmacogenetic polymorphisms with cardiovascular
      and metabolic complications of atypical antipsychotics.

      Hypothesis 2: Profiles of polymorphisms at receptors targeted by atypical antipsychotics will
      be associated with impaired cardiovascular function and metabolic complications.
    

Detailed description: 
      Participants will have all evaluations related to metabolic complications performed in the
      University of Iowa Clinical Research Unit (CRU) or in the EndoPAT laboratory located in Room
      269 GH. For all visits, weights will be measured without shoes, in light clothing, using an
      electronic scale that measures to the nearest 0.25 kg. Standing heights will be measured
      without shoes, to the nearest 0.1 cm using a free-standing stadiometer. These weights and
      heights will be utilized for the computation of body mass index (BMI). Waist circumference
      will be measured horizontally at the tip of the right iliac crest in the standing position
      using a measuring tape. Blood pressure and heart rate will be measured in the sitting
      position after five minutes of silent rest, using an automated sphygmomanometer. An
      ambulatory blood pressure will also be obtained at each visit. An EKG will be conducted
      during Visit 1. Dual energy X-ray absortionmetry (DEXA) will assess percentage of body fat at
      intake, Visit 4 and Visit 8. If a participant is unable to complete a DEXA scan, body fat
      will be determined using the BOD POD® Gold Standard Body Composition Tracking System. The BOD
      POD® is an integrated system consisting of a digital scale to measure subject mass, a large
      egg-shaped fiberglass air displacement plethysmography (ADP) to determine body volume (BV),
      and a computer that operates the equipment and calculates body composition. Body density is
      determined from subject mass and volume measurements and then percent fat is calculated using
      one of several standard formulas. CRU dieticians will perform skin fold measurements at
      intake and completion. Fasting measures of triglycerides, LDL-C, HDL-C, IDL, VLDL,
      apolipoprotein A, apolipoprotein B, Lp(a) cholesterol, C-reactive protein, IL-6, leptin
      levels, insulin levels, and glucose will be obtained at baseline, 2 weeks, 12 weeks, 26
      weeks, 1 year, 2 years, 3 years and 4 years. Hemoglobin A1C will be collected at baseline and
      weeks 12 and 26, 1 year, 2 years, 3 years and 4 years. Cholesterol levels will be determined
      by an enzymatic calorimetric test using cholesterol esterase and cholesterol oxidase. LDL-C
      and HDL-C fractions will be obtained via a homogeneous enzymatic in vitro colorimetric assay.
      For the determination of triglyceride levels, free glycerol is eliminated prior to hydrolysis
      of triglycerides in a preliminary reaction where lipase and 4-aminophenazone are omitted,
      followed by enzymatic hydrolysis of triglycerides and determination of the liberated glycerol
      by a fully enzymatic colorimetric assay reaction. Apolipoproteins and other lipid parameters
      will be measured using beta quantification through the Mayo Medical Laboratories (unit code
      83673).

      Endothelial and Cardiovascular Function: Participants will have endothelial function measured
      at baseline, and each subsequent visit. To maximize completion rates, participants planning
      to discontinue their antipsychotic between weeks 16 and 26 will have their final measures
      taken at the time of discontinuation. Prior to these appointments, participants will be
      instructed to not eat or drink anything (including caffeinated products such as coffee, tea,
      soda, etc.) except water for at least 12 hours prior to the appointment. They will also be
      instructed to not drink any alcohol for 24 hours prior to each study. They will be asked not
      to smoke for the two hours prior to the study. Administration of blood pressure and lipid
      lowering medications for that day will be delayed until after the procedures. Measures of
      endothelial function will be obtained in the Clinical Research Unit (CRU).

      CONDUIT VESSEL FUNCTION: Conduit vessel endothelial function will be assessed non-invasively
      via ultrasound measurement of brachial artery diameter during changes in brachial artery
      flow. The technique uses a 10-13 MHz linear array transducer ultrasound system (Biosound
      ESAOTE, Indianapolis, IN). A 5 cm length of the brachial artery is imaged in longitudinal
      section above the antecubital fossa and the optimal probe site on the skin marked. Baseline
      images of brachial artery diameter and Doppler velocities from the center of the vessel are
      recorded on videotape. While images for brachial artery diameter are being continuously
      recorded, an occluding forearm cuff placed just below the antecubital fossa is inflated for 5
      minutes. The brachial artery diameter and Doppler velocities are continuously recorded
      before, during and after cuff deflation. After approximately 5 minutes, once basal diameter
      and flow have been restored, nitroglycerin (300 mcg) will be administered sublingually and
      measurements made for an additional 6 minutes.

      HEART RATE AND BLOOD PRESSURE VARIABILITY: We will also assess blood pressure and heart rate
      variability using recordings of indirect arterial pressure with a beat-to-beat finger
      systolic and diastolic blood pressure recording in conjunction with the electrocardiogram
      tracing during the conduit vessel function procedures. Data from this measurement will allow
      us to assess blood pressure and heart rate variability. Cardiovascular variability (HRV) is a
      marker for cardiovascular risk whereby lower variability indicates greater risk for
      myocardial infarct and stroke. This procedure can be performed during assessment of conduit
      vessel function so requires no additional time.

      ARTERIAL TONOMETRY: We will utilize arterial tonometry through measurement of pulse wave
      analysis (PWA) and pulse wave velocity (PWV) using a SphygmorCor machine. This machine uses a
      noninvasive probe, pressed lightly on the skin over the carotid, radial and femoral arteries
      for about five minutes each. These measurements will provide a measure of arterial
      compliance, stiffness, and other hemodynamic information. The PWA system is a computerized
      diagnostic tool for the assessment of central blood pressure. The peripheral pressure pulse
      waveform contains information in addition to the maximum and minimal values (systolic and
      diastolic pressures). The PWA system can derive the central aortic pressure waveform from the
      peripheral pressure waveform recorded at the radial or carotid arteries. The system uses
      mathematical transforms to derive the central aortic pressure pulse waveform and then
      calculates a range of central indices of ventricular-vascular interaction, which are
      displayed both graphically and numerically. The PWV system measures the velocity of the blood
      pressure waveform between any two superficial artery sites. A pressure tonometer is used to
      transcutaneously record the pressure pulse waveforms in the underlying artery. The pressure
      pulse waveform is recorded simultaneously with an electrocardiogram (ECG) signal, which
      provides an R-wave timing reference. Pressure pulse recordings are performed consecutively at
      the two superficial artery sites over the carotid and femoral artery. The software processes
      each set of pressure pulse and ECG waveform data to calculate the mean time difference
      between the R-wave and the pressure wave- on a beat-by-beat basis. The PWV is then calculated
      using the mean time difference and the arterial path length between the two recording sites.
      The velocity of the blood pressure pulse waveform is dependent on the stiffness of the artery
      along which the pulse is traveling. Serial measurement of pulse wave velocity in a section of
      artery will indicate the magnitude of change in arterial stiffness in that section of the
      artery.

      PSYCHIATRIC ASSESSMENT: Detailed historical information will be gathered including age,
      occupation, education, race, height, weight, medical history, treatment history, family
      history of medical illness with focus on risk factors for metabolic syndrome, and substance
      use history including tobacco. Basic clinical information will be obtained to verify
      psychiatric diagnosis and assess cardiac risk by the Framingham Heart Study formula. It is
      estimated that this history will take 45 minutes to complete. Affective and psychotic
      symptomatology will be cross-sectionally assessed using the Montgomery Asberg Depression
      Rating Scale, the Young Mania Scale, and the Brief Psychotic Rating Scale.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Thirty patients, 18 - 50 years of age, who are being started on a first-line,
        second-generation, antipsychotic associated with weight gain (risperidone, olanzapine, or
        quetiapine) for the treatment of an affective or psychotic disorder, will be invited to
        participate. Participants must not have taken any of these antipsychotics or clozapine in
        the preceding three months. Another twenty psychiatric controls not taking antipsychotic
        medications will also be enrolled. Statistically, controls will serve primarily to compare
        changes in flow-mediated dilation over time rather than for direct comparison of variables
        between groups. Participation will be voluntary and initiated upon clinician or
        self-referral.