Anxiety-mediated Impairments in Large Elastic Artery Function and the Autonomic Nervous System

The goal of this study is to evaluate the effectiveness of a short-term (4 weeks) pharmacological blockade of sympathetic nerve activity (clonidine) on anxiety symptoms, vascular function, inflammation, muscle sympathetic nerve activity, and oxidant stress in individuals with moderate-to-high anxiety. Individuals who are interested in the study will be identified by an online screening survey and will be contacted by the research team; advertisements, flyers and mass emails will direct individuals to the online screening survey. Those deemed eligible to participate will be randomized to either the clonidine intervention or hydrochlorothiazide as a blood-pressure lowering control condition. If eligible participants are currently being treated with blood pressure-lowering medications, they will be asked to go off these medications for 2 weeks prior to and during the course of the study. During the 2 week washout of blood pressure-lowering medications, participants will have safety visits (2 additional visits) that include measurements of blood pressure at 4 days and 7 days after the beginning of the washout period before the intervention. Assessments of anxiety symptoms via various surveys, vascular function (via non-invasive, well-established techniques), inflammation, muscle sympathetic nerve activity, and oxidant stress will be performed at baseline and at the post intervention session. Similar baseline measurements will be performed in control subjects with low or no anxiety for comparison, but these individuals will not undergo the intervention.

Participants with moderate-to-high anxiety will have a total of 6 visits to the laboratory, which includes the screening and consent (visit 1). Visit 2 (baseline measurements) and visit 6 (post-intervention measurements) will be more extensive (\~4.5 hours) compared to the other visits (\~30 min). Participants completing the washout will have an additional 2 visits (\~30 min each) before "visit 2." Control subjects with low or no anxiety will only participate in visit 1 (screening and consent ) and visit 2 (baseline measurements).

Anxiety disorders are the most common mental health problems in the United States, occurring in about 18% of adults per year, and a lifetime prevalence of approximately 28% (25). Importantly, anxiety disorders are associated with increased risk for sudden cardiac death and non-fatal myocardial infarction (27, 46) independent of other mood disorders (13, 15). However, establishing a clear consensus on the mechanism(s) by which chronic anxiety confers cardiovascular disease (CVD) risk has proven difficult. Previous studies examining the potential role of vascular dysfunction in subjects with anxiety have been confounded by co-morbidities (e.g., hypertension, smoking, obesity) (31, 38) and added psychiatric disorders (63). Additionally, studies focusing on the relation between anxiety and robust predictors of CVD mortality, such as large elastic artery (e.g., aortic, carotid) stiffness, have been lacking.

Anxiety is experienced as negative feelings of threat, restlessness, tension and irritability, and somatic symptoms, such as palpitations, sweating, trembling, and dry mouth (57). Patients with clinically diagnosed anxiety disorder demonstrate more than 2-fold increase in future CVD events (23). Despite the strong association between anxiety and CVD risk, there is currently a gap in knowledge describing potential mechanisms by which anxiety leads to CVD. Evidence suggests that chronically high levels of anxiety may be associated with the progression of subclinical atherosclerosis such as carotid artery intima-media thickness (38) and elevated inflammation (5, 44). Symptoms of anxiety may also lead to impairment in resistance vessel dilator function (53). However, few studies have examined large elastic artery stiffness in subjects with high levels of anxiety. This is clinically important because large elastic artery stiffness (i.e., carotid and aortic) is a robust independent risk factor for CVD events such as stroke and myocardial infarction (6, 19, 59, 61). Interestingly, greater large elastic artery stiffness (aortic) is observed with higher resting muscle sympathetic nerve activity (MSNA) in healthy individuals even after adjusting for BP (9, 55). In this regard, numerous studies have shown that high MSNA independent of any increase in blood pressure can have deleterious vascular (7, 17, 32), metabolic (2, 20), cardiac (50, 52), and renal effects (1, 14, 54). Higher tonic MSNA is an independent determinant of aortic artery stiffness as assessed by the gold standard carotid-femoral pulse wave velocity (PWV) in healthy humans (55). Even acute increases in MSNA, such as during mental stress which is a potent stimulus for increases in MSNA (3), can lead to transiently greater large elastic artery stiffness (40). Furthermore, in healthy humans, acute mental stress induces transient endothelial dysfunction (16), an important modulator of arterial stiffness. Given findings from previous studies (22) showing that anxiety symptoms are associated with indices of elevated sympathetic nerve activity (e.g., elevated circulating norepinephrine), lead us to our overall hypothesis that anxiety-induced sympathetic overactivity leads to increased large elastic artery (carotid and aortic) stiffness in subjects with chronic anxiety.

The purpose of this study is to 1) determine the extent to which measures of vascular and autonomic function (large elastic artery stiffness, vascular inflammation and baroreflex function) is impaired in subjects with moderate-to-high anxiety, and 2) test the magnitude by which short-term (4 weeks) sympathetic nerve activity blockade (clonidine) improves large elastic artery stiffness, vascular inflammation and baroreflex function in subjects with moderate-to-high levels of anxiety.

In healthy subjects, chronic anxiety has been associated with increased risk of cardiac events (13, 15, 23). Interestingly, evidence suggests baroreflex function is reduced in subjects with anxiety (48, 60), thus adding additional cardiac risk burden to this population. Consistent with this, impairment in cardiac baroreflex sensivity (BRS) is a significant predictor of cardiac arrhythmias and myocardial infarction mortality (29, 56). Moreover, reduced cardiac BRS is a sensitive predictor of mortality after myocardial infarction (28, 30), particularly in subjects with anxiety (47). Reduced baroreflex activation can be attributed, in part, to reduced distensibility of baroreceptor regions within the elastic carotid and aortic arteries as a result of increased arterial stiffness (8). Given the associated risk of cardiac BRS impairment with anxiety, and the increase in large elastic artery stiffness in this population, there is a critical need to examine whether reductions in SNA and large elastic artery stiffness ameliorates cardiac BRS impairment in subjects with anxiety, thus providing experimental support for the novel idea that anxiety leads to increased CVD risk at least in part through elevated large artery stiffness.

Eligibility Criteria:
Inclusion Criteria for participants with moderate-to-high anxiety to undergo drug intervention:

* Willing and able to provide written, signed consent after the nature of the study has been explained, and prior to any research-related procedures.

Age is \> or = 18 and \< or = 79 years

No history of cardiovascular disease (e.g., heart attack, stroke, heart failure, valvular heart disease, cardiomyopathy), or peripheral arterial disease.

Non-smokers, defined as no history of smoking or no smoking for at least the past 3 months.

Normal resting 12-lead ECG (no evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Blood chemistries indicative of normal renal (creatinine \<2.0mg/dl), liver (\<3 times upper limit for ALT, AST), and thyroid function (TSH between 0.4 - 5.0 mU/L) or on stable thyroid medication with no dose change for 3 months.

Exclusion Criteria:

* Current use of clonidine or beta-blockers

Current use of antihypertensive medications for reasons other than hypertension (e.g., hydrochlorothiazide for leg edema or kidney stone prevention, beta-blockers for tremor)

Difficult to control hypertension (e.g., on 2 or 3 antihypertensive medications)

Low blood pressure (e.g., systolic BP \< 110 mmHg)

Hypertensive and have not been stable on their current antihypertensive medication regimen for at least 6 months

Blood pressure not controlled either on or off antihypertensive medications (e.g., BP \> 150/100)

Current diagnosis or history of cancer, liver disease, HIV/AIDS

History of brain tumor, aneurysm or injury

Clinical diagnosis of mental health disorders such as bipolar disorder or schizophrenia

History of cardiovascular disease such as heart angioplasty/stent or bypass surgery, myocardial infarction, stroke, heart failure with or without LV ejection fraction \<40%, cardiomyopathy, valvular heart disease, cardiomyopathy, heart transplantation, atherosclerosis.

Current tobacco user or history of tobacco use within the past 3 months (cigarettes, cigars, chewing tobacco, Hookah).

History of lung emphysema, chronic bronchitis or chronic obstructive pulmonary disease (COPD).

Abnormal resting 12-lead ECG (e.g., evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Serious neurologic disorders including seizures.

History of renal failure, dialysis or kidney transplant.

Use of any investigational products or investigational medical devices within 30 days prior to screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.

Recent flu-like symptoms within the past 2 weeks.

Pregnant or breastfeeding at screening, or planning to become pregnant (self or partner) at any time during the study. A urinary pregnancy test will be done on all females. If test is positive, the subject will be excluded.

History of rheumatoid arthritis, Grave's disease, systemic lupus erythamatosis, and Wegener's granulomatosis.

Taking anticoagulation, anti-seizure, or antipsychotic agents.

Start of or dose change to an antidepressant or anti-anxiety medication within the past 3 months (if no change in medication or dose in past 3 month, then subject will be eligible).

Immunodeficiency or systemic autoimmune disease.

History of bleeding disorders or conditions of the microcirculation (i.e. von Willebrand disease, Raynaud's disease).

History of co-morbid condition that would limit life expectancy to \<1 year.

Taking chronic non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin, naproxen, acetaminophen (Tylenol®), ibuprofen (Advil®, Motrin®) and not able or willing to go off of for 2 weeks prior to each study visit.

Taking cox-2 inhibitors (Celebrex®, Vioxx®, etc) or allopurinol (Zyloprim®, Lopurin®, Aloprim®).

Taking steroids or biologics: corticosteroids (prednisone); methotrexate, infliximib (Remicade®), etaneracept (Enbrel®); anakinra (Kineret®).

Those who are currently donating blood, platelets, or plasma at the time of screening.

Vulnerable populations (prisoners, etc.) will not be eligible to participate in this study.

On weight loss drugs (i.e. orilistat (Xenical®), sibutramine (Meridia®), phenylpropanol-amine (Acutrim®)), or similar over-the-counter medications within 3 months of screening.

Any surgery within 30 days of screening

Those who currently donate blood, platelets, or plasma

Any condition that, in the view of the PI or Co-I, places the subject at high risk or poor treatment and study compliance.

We will also enroll 36 participants ages 18-79 years (50% men, 50% women) with low or no anxiety as control subjects to participate in only baseline testing (not participate in the drug intervention).

Inclusion criteria:

Willing and able to provide written, signed consent after the nature of the study has been explained, and prior to any research-related procedures.

Age is \> or = 18 and \< or = 79 years

No history of cardiovascular disease (e.g., heart attack, stroke, heart failure, valvular heart disease, cardiomyopathy), or peripheral arterial disease.

Non-smokers, defined as no history of smoking or no smoking for at least the past 3 months.

Normal resting 12-lead ECG (no evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Blood chemistries indicative of normal renal (creatinine \<2.0mg/dl), liver (\<3 times upper limit for ALT, AST), and thyroid function (TSH between 0.4 - 5.0 mU/L) or on stable thyroid medication with no dose change for 3 months.

Exclusion Criteria:

Current use of clonidine or beta-blockers

Current use of antihypertensive medications for reasons other than hypertension (e.g., hydrochlorothiazide for leg edema or kidney stone prevention, beta-blockers for tremor)

Difficult to control hypertension (e.g., on 2 or 3 antihypertensive medications)

Low blood pressure (e.g., systolic BP \< 110 mmHg)

Hypertensive and have not been stable on their current antihypertensive medication regimen for at least 6 months

Blood pressure not controlled either on or off antihypertensive medications (e.g., BP \> 150/100)

Current diagnosis or history of cancer, liver disease, HIV/AIDS

History of brain tumor, aneurysm or injury

Clinical diagnosis of mental health disorders such as bipolar disorder or schizophrenia

History of cardiovascular disease such as heart angioplasty/stent or bypass surgery, myocardial infarction, stroke, heart failure with or without LV ejection fraction \<40%, cardiomyopathy, valvular heart disease, cardiomyopathy, heart transplantation, atherosclerosis.

Current tobacco user or history of tobacco use within the past 3 months (cigarettes, cigars, chewing tobacco, Hookah).

History of lung emphysema, chronic bronchitis or chronic obstructive pulmonary disease (COPD).

Abnormal resting 12-lead ECG (e.g., evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Serious neurologic disorders including seizures.

History of renal failure, dialysis or kidney transplant.

Use of any investigational products or investigational medical devices within 30 days prior to screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.

Recent flu-like symptoms within the past 2 weeks.

Pregnant or breastfeeding at screening, or planning to become pregnant (self or partner) at any time during the study. A urinary pregnancy test will be done on all females. If test is positive, the subject will be excluded.

History of rheumatoid arthritis, Grave's disease, systemic lupus erythamatosis, and Wegener's granulomatosis.

Taking anticoagulation, anti-seizure, or antipsychotic agents.

Start of or dose change to an antidepressant or anti-anxiety medication within the past 3 months (if no change in medication or dose in past 3 month, then subject will be eligible).

Immunodeficiency or systemic autoimmune disease.

History of bleeding disorders or conditions of the microcirculation (i.e. von Willebrand disease, Raynaud's disease).

History of co-morbid condition that would limit life expectancy to \<1 year.

Taking chronic non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin, naproxen, acetaminophen (Tylenol®), ibuprofen (Advil®, Motrin®) and not able or willing to go off of for 2 weeks prior to each study visit.

Taking cox-2 inhibitors (Celebrex®, Vioxx®, etc) or allopurinol (Zyloprim®, Lopurin®, Aloprim®).

Taking steroids or biologics: corticosteroids (prednisone); methotrexate, infliximib (Remicade®), etaneracept (Enbrel®); anakinra (Kineret®).

Those who are currently donating blood, platelets, or plasma at the time of screening.

Vulnerable populations (prisoners, etc.) will not be eligible to participate in this study.

On weight loss drugs (i.e. orilistat (Xenical®), sibutramine (Meridia®), phenylpropanol-amine (Acutrim®)), or similar over-the-counter medications within 3 months of screening.

Any surgery within 30 days of screening

Those who currently donate blood, platelets, or plasma

Any condition that, in the view of the PI or Co-I, places the subject at high risk or poor treatment and study compliance.

We will also enroll 36 participants ages 18-79 years (50% men, 50% women) with low or no anxiety as control subjects to participate in only baseline testing (not participate in the drug intervention). These subjects will be either lean (body mass index \< 25) or on the obesity spectrum (body mass index \> 30).

Because obesity is linked with hypertension and type 2 diabetes, enrollment of subjects may include those with pre-hypertension or hypertension (systolic blood pressure \>/= 120 - \<180 mmHg- average of at least 3 measurements 2 min apart after 10 min seated resting position), and/or pre-diabetes (defined as fasting blood glucose between 100-126 mg/dl, fasting blood glucose of 140-199 mg/dl at 120 min of an oral glucose tolerance test, or HbA1C of 6-6.5%) or type 2 diabetes (defined as fasting blood glucose between \>126 mg/dl, fasting blood glucose of \>199 mg/dl at 120 min of an oral glucose tolerance test, or HbA1C \> 6.5%). These subjects may be taking anti-hypertensive and/or diabetes (anti-hyperglycemic) medications. Subjects will be asked to refrain from medications the morning of the study visit, and to bring their medications with them to take immediately following their study visit.

Inclusion criteria:

Willing and able to provide written, signed consent after the nature of the study has been explained, and prior to any research-related procedures.

Age is \> or = 18 and \< or = 79 years

No history of cardiovascular disease (e.g., heart attack, stroke, heart failure, valvular heart disease, cardiomyopathy), or peripheral arterial disease.

Non-smokers, defined as no history of smoking or no smoking for at least the past 3 months.

Normal resting 12-lead ECG (no evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Blood chemistries indicative of normal renal (creatinine \<2.0mg/dl), liver (\<3 times upper limit for ALT, AST), and thyroid function (TSH between 0.4 - 5.0 mU/L) or on stable thyroid medication with no dose change for 3 months.

Exclusion Criteria:

Current diagnosis or history of cancer, liver disease, HIV/AIDS

History of brain tumor, aneurysm or injury

Clinical diagnosis of mental health disorders such as bipolar disorder or schizophrenia

History of cardiovascular disease such as heart angioplasty/stent or bypass surgery, myocardial infarction, stroke, heart failure with or without LV ejection fraction \<40%, cardiomyopathy, valvular heart disease, cardiomyopathy, heart transplantation, atherosclerosis.

Current tobacco user or history of tobacco use within the past 3 months (cigarettes, cigars, chewing tobacco, Hookah).

History of lung emphysema, chronic bronchitis or chronic obstructive pulmonary disease (COPD).

Abnormal resting 12-lead ECG (e.g., evidence of myocardial infarction, left ventricular hypertrophy, left-bundle branch block, 2nd or 3rd degree AV block, atrial fibrillation/flutter, atherosclerosis).

Serious neurologic disorders including seizures.

History of renal failure, dialysis or kidney transplant.

Use of any investigational products or investigational medical devices within 30 days prior to screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.

Recent flu-like symptoms within the past 2 weeks.

Pregnant or breastfeeding at screening, or planning to become pregnant (self or partner) at any time during the study. A urinary pregnancy test will be done on all females. If test is positive, the subject will be excluded.

History of rheumatoid arthritis, Grave's disease, systemic lupus erythamatosis, and Wegener's granulomatosis.

Taking anticoagulation, anti-seizure, or antipsychotic agents.

Start of or dose change to an antidepressant or anti-anxiety medication within the past 3 months (if no change in medication or dose in past 3 month, then subject will be eligible).

Immunodeficiency or systemic autoimmune disease.

History of bleeding disorders or conditions of the microcirculation (i.e. von Willebrand disease, Raynaud's disease).

History of co-morbid condition that would limit life expectancy to \<1 year.

Taking chronic non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin, naproxen, acetaminophen (Tylenol®), ibuprofen (Advil®, Motrin®) and not able or willing to go off of for 2 weeks prior to each study visit.

Taking cox-2 inhibitors (Celebrex®, Vioxx®, etc) or allopurinol (Zyloprim®, Lopurin®, Aloprim®).

Taking steroids or biologics: corticosteroids (prednisone); methotrexate, infliximib (Remicade®), etaneracept (Enbrel®); anakinra (Kineret®).

Those who are currently donating blood, platelets, or plasma at the time of screening.

Vulnerable populations (prisoners, etc.) will not be eligible to participate in this study.

On weight loss drugs (i.e. orilistat (Xenical®), sibutramine (Meridia®), phenylpropanol-amine (Acutrim®)), or similar over-the-counter medications within 3 months of screening.

Any surgery within 30 days of screening

Those who currently donate blood, platelets, or plasma

Any condition that, in the view of the PI or Co-I, places the subject at high risk or poor treatment and study compliance.