Effects of Melatonin to Reduce Nocturnal Hypertension in Patients With Neurogenic Orthostatic Hypotension

Study Overview
=================
Brief Summary
-----------------
Neurogenic Orthostatic Hypotension (NOH) is clinically defined as a consistent drop in systolic blood pressure (SBP) ≥30mmHg upon standing from a seated or lying position. However, 50% of NOH patients also have associated supine hypertension. It has been proposed that supine hypertension is the result of intact post-ganglionic sympathetic nerves and therefore due to residual sympathetic tone. Furthermore, research investigating the effects of melatonin shows blood pressure implication of this naturally secreted hormone. Specifically, melatonin has been investigated as a non-traditional anti-hypertensive agent for patients with essential and nocturnal hypertension. Central and peripheral mechanisms have been proposed to help explain how melatonin reduces blood pressures. Therefore, we aim to identify NOH patients as having either intact or denervated post-ganglionic sympathetic nerves, monitor the correlation to supine hypertension and subsequently investigate the effects of melatonin on blood pressure in these patients.

Detailed Description
-----------------
Neurogenic orthostatic hypotension (NOH) is a debilitating condition associated with reduced quality of life, impaired function and is also an independent predictor of mortality(Bendini et al., 2007; Cordeiro et al., 2009; Rose et al., 2006). NOH is clinically defined as a sustained reduction in systolic blood pressure (SBP) ≥30mmHg within 3 minutes of standing or head-up tilt to at least 60 degrees on a tilt table(Freeman et al., 2011). Specifically, neurogenic OH can be differentiated from other causes of orthostatic hypotension, such as hypotension due to endocrine issues, generalized low blood pressure, low blood volume, etc., in that NOH is associated with autonomic dysfunction. Specifically, dysfunction of the reflexive regulation mediated by the sympathetic nervous system(Goldstein and Sharabi, 2009; Low et al., 2008). Studies have implicated specific dysfunction of the peripheral sympathetic nerves in disorders that have accompanying NOH such as Multiple System Atrophy (MSA), Pure Autonomic Failure (PAF) and Parkinson Disease (PD+NOH)(Imrich et al., 2009; Senard et al., 1993; Sharabi et al., 2006). In clinical NOH populations with known diagnoses such as MSA, PAF and PD+NOH, infusions of yohimbine have been used to detect whether post-ganglionic sympathetic nerves are intact or denervated. Yohimbine is an alpha-adrenoceptor antagonist that, in healthy/intact sympathetic nerves, causes an increase in the release of norepinephrine (NE) from sympathetic nerves via increased sympathetic neuronal outflow. NE is a natural neurotransmitter that is released when the sympathetic nervous system is required to increase its activity. In persons with intact post-ganglionic sympathetic nerves an infusion of yohimbine results in an increase in blood pressure, arterial NE levels, and heart rate levels, with a decrease in forearm blood flow indicative of vasoconstriction. In contrast, patients with sympathetic denervation these responses are attenuated(Senard et al., 1993; Shannon et al., 2000; Sharabi et al., 2006). However, in these studies, the clinical population consisted of MSA, PAF and PD+NOH. Little research has been done in NOH populations without an underlying diagnosis, and in fact, 1/3 of patients with NOH have no identifiable underlying cause (Robertson and Robertson, 1994). Furthermore, it has been hypothesized that supine hypertension in this select patient population is due to residual sympathetic tone in patients with intact post-ganglionic sympathetic nerves. Approximately 50% of NOH patients have associated supine hypertension(Shannon et al., 2000), which if left untreated, comes with its very own unique set of cardiovascular complications, such as significantly higher left-ventricular mass indices, specific end organ damage(Vagaonescu et al., 2000), heart attack and stroke. Therefore, clinicians are left with the challenging dilemma of finding a near impossible balance between the risks associated with supine hypertension versus the risks of sudden hypotension upon standing and the associated consequences of falls, fractures and head injuries resulting in more immediately morbid events. Medications such as nitrates and other antihypertensives can be prescribed, however their use is strongly cautioned as it is quite frequent that NOH patients are often older and have nocturia, and as a result are up frequently throughout the night. Other options such as raising the head of the bed 4 inches from the ground in order to reduced renal hyper-perfusion pose as an additional conservative measure, however, this does not act as a treatment for the supine hypertension. In contrast, melatonin is a natural hormone secreted by the pineal gland in response to low light and is involved in maintaining proper circadian rhythms and sleep patterns. However, more recently, there has been a growing source of literature supporting melatonin as having an important role in blood pressure control: i) In rats, following pinealectomy, there is evidence of vasoconstriction (Cunnane et al., 1980) and hypertension (Zanoboni et al., 1978; Zanoboni and Zanoboni-Muciaccia, 1967). ii) Experimental hypertension elicited via pinealectomy can be reversed through exogenous administration of melatonin(Holmes and Sugden, 1976). iii) Continuous light exposure, results in a melatonin deficiency, peripheral vasoconstriction and hypertension(Briaud et al., 2004; Brown et al., 1991). Therefore, melatonin is now being looked at as a non-traditional anti-hypertensive medication in patients with essential and nocturnal hypertension. In a study of 34 patients with nocturnal hypertension, administration of melatonin proved to have a slight, yet significant, reduction in nighttime blood pressure measurements(Grossman et al., 2006). In these studies, melatonin was taken for 3 or 4 weeks via an oral prescription 1 hour before bed. The dose was formulated as a controlled- or slow-release throughout the night. In these studies, there was an average systolic BP drop of 6.5mmHg and 4mmHg diastolic in supine/nighttime blood pressures. While this reduction may not seem significant, clinical it is. In a study of 2156 hypertensive patients, following a median follow-up period of 5.6 years it was found that the cardiovascular risk adjustment per 5mmHg reduction of nocturnal blood pressure in patients aged 55 years and above, was 0.92 (95%CI0.88-0.96) and per 5mmHg reduction in nocturnal diastolic blood pressure was 0.82 (95%CI0.77-0.88). The decrease in mean asleep BP during follow-up was most significantly associated with event-free survival (Hermida et al., 2010). In women, a mean decrease of 6mmHg in diastolic pressure significantly reduced overall mortality from vascular disease by 21%, fatal and nonfatal stroke by 42%, and fatal and nonfatal coronary heart disease by 14% (Rich-Ewards et al., 1995). Currently, the posed mechanisms of melatonin to reduced blood pressure consist of both central and peripheral mechanisms (Capsoni et al., 1994; Pogan et al., 2002; Ray, 2003; Satake et al., 1991; Stankov et al., 1993; Weekley, 1993). Therefore, the objectives of the current study are: 1. Identify NOH patients as having either peripherally intact vs denervated post-ganglionic sympathetic innervation to help identify a group of patients potentially more susceptible to supine hypertension. 2. Administer melatonin and monitor its effects on supine/nocturnal blood pressures in patients with supine hypertension, and 3. Investigate the proposed mechanisms of melatonin by comparing its effects in patients with peripherally intact vs denervated sympathetic nerves.

Official Title
-----------------
Identifying the Pathophysiology of Neurogenic Orthostatic Hypotension and the Effects of Melatonin on Reducing Supine Hypertension in Peripherally Intact Versus Denervated Post-ganglionic Sympathetic Nerves

Conditions
-----------------
Hypotension, Orthostatic, Hypertension, Autonomic Nervous System Diseases

Intervention / Treatment
-----------------
* Drug: Yohimbine
* Drug: Melatonin


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Control population: Healthy males or females between the ages of 18-80. Patient population: Males or females who have been previously diagnosed with Neurogenic Orthostatic Hypotension. Exclusion Criteria: Patient population: Medical therapies or medications which could interfere with testing of autonomic function. Clinically significant heart disease. Presence of unrelated nerve damage in the peripheral nervous system. Pregnant or breast feeding females. The presence of failure of other organ systems or systemic illness that can affect autonomic function or your ability to cooperate. These include dementia, heart failure, kidney or liver disease, severe anemia, alcoholism, any new and abnormal cell growth identified as malignant, hypothyroidism, surgical procedures where the nerves of the sympathetic nervous system have been cut, or cerebrovascular disease. Exclusion criteria for monitoring the effects of melatonin 1. All the above PLUS No lying/night time hypertension as determined by 24-hour blood pressure monitoring Exclusion criteria for healthy controls: Presence of ANY autonomic dysfunction Medical therapies or medications which could interfere with testing of autonomic function. Clinically significant heart disease. Presence of ANY nerve damage in the peripheral nervous system. Pregnant or breast feeding females. The presence of failure of other organ systems or systemic illness that can affect autonomic function or your ability to cooperate. These include dementia, heart failure, kidney or liver disease, severe anemia, alcoholism, any new and abnormal cell growth identified as malignant, hypothyroidism, surgical procedures where the nerves of the sympathetic nervous system have been cut, or cerebrovascular disease.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Effects of Yohimbine<br>Investigation into the integrity of post-ganglionic sympathetic nerves in patients with idiopathic neurogenic orthostatic hypotension | Drug: Yohimbine<br>* Oral Yohimbine will be used to identify the integrity of post-ganglionic sympathetic nerves in patients with NOH<br>* Other names: DIN:01901885;|
| Experimental: Effects of melatonin on blood pressure<br>Investigation into the effects of melatonin at two separate dosages (2 and 5mg) on nocturnal blood pressure in NOH patients with intact versus denervated post-ganglionic sympathetic nerves | Drug: Melatonin<br>* Monitor the effects of melatonin on supine hypertension in NOH patients with intact and denervated post-ganglionic nerves. Identify the mechanistic pathway of melatonin in blood pressure regulation<br>* Other names: melatonin timed release; 2 or 5 mg;|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Investigation into the integrity of post-ganglionic sympathetic nerves in idiopathic NOH | Markers of post-ganglionic sympathetic function will be examined (i.e. sympathetic blood markers, heart rate, blood pressure, sympathetic nerve activity, etc.) | Sympathetic markers will be assessed during and immediately following the test. A comparison between healthy participants and NOH patients will be ongoing throughout recruitment and upon completion of study recruitment | 
| Effects of melatonin on supine hypertension in persons with neurogenic orthostatic hypotension | Supine systolic blood pressure | 4 weeks | 
| Effects of melatonin on supine hypertension in patients with neurogenic orthostatic hypotension | Change in postural (supine-standing) systolic blood pressure | 4 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum markers of sympathetic activation |  | Before and during stimulation of sympathetic nervous system | 
| Carotid artery diameter |  | During stimulation of sympathetic nervous system | 
| Sympathetic nerve activation using microneurography |  | During stimulation of sympathetic nervous system | 
| Orthostatic symptoms based on standard autonomic symptom questionnaires |  | 30 minutes before testing | 
| Sleep quality assessment using Epworth Sleepiness Scale |  | Assessed at pre- and post- melatonin treatment; week 1 and week 5 of melatonin intervention timeframe | 
| Urine and Saliva melatonin levels |  | Assessed at pre- and post- melatonin treatment; week 1 and week 5 of melatonin intervention timeframe | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Melatonin, Yohimbine, Anti-hypertensive agents