MR Antagonist and STRIATIN

• Status: Recruiting
• Trial end date: 2022-08-31
• Target enrollment: 0
• Participant gender: All

Summary

Salt sensitivity of blood pressure is a substantial risk factor for cardiovascular morbidity and mortality. Inappropriate increases in renal sodium reabsorption lead to volume expansion, hypertension and salt sensitive blood pressure. Key homeostatic mechanisms that regulate renal sodium reabsorption are: first, hormonal, e.g., renin-angiotensin-aldosterone system and second, vascular, e.g., renal vasculature. Dysfunction in one or both mechanisms leads to hypertension and salt sensitive blood pressure. The investigators recently documented that striatin plays a novel role in the development of salt sensitive blood pressure. However, the mechanisms that lead to striatin-mediated salt sensitive blood pressure are not clear; defining these mechanisms is the overall goal of this proposal.

Striatin is a calmodulin- and caveolin-binding protein that can function as either a scaffolding and/or signaling protein, specifically in relation to the mechanism of action of steroids. In a large study of well characterized subjects from the HyperPATH cohort, the investigators documented that hypertensive and normotensive humans who are striatin risk allele carriers have salt sensitive blood pressure.

The investigators then developed a striatin heterozygous knockout mouse as a tool to identify potential mechanisms for the salt sensitive blood pressure. The investigators documented that these mice also have salt sensitive blood pressure with higher blood pressure levels and inappropriately increased aldosterone levels on a liberal salt diet.

• Phase: Phase 4
• Accepts Healthy Volunteers?: Accepts Healthy Volunteers

Details

• Lead Sponsor: Brigham and Women's Hospital
• Treatments: Amlodipine; Eplerenone

Criteria

The subjects evaluated in this protocol are hypertensive and carry the Striatin rs254093 risk allele or both Striatin rs888083 and rs6744560 risk alleles. Most will be recruited from the HyperPATH cohort. The HyperPATH cohort was developed under a SCOR in Hypertension program. This program has demographic data and DNA on more than 4000 subjects. Currently, nearly 2000 of them have undergone an extensive phenotyping protocol. All hypertensive medications have been stopped for 4 weeks before study except agents that interfere with the renin-angiotensin-aldosterone system (RAAS) are stopped for three months and amlodipine and/or hydrochlorothiazide is added if necessary for blood pressure control until one month before study initiation. Then each subject is studied twice on a diet consisting of 100 mmol potassium, 800 mg calcium, isocaloric, 2500 ml. The two times they are studied are after one week of a liberal sodium diet (200 mmol) and after one week of a low sodium diet (10 mmol). Blood is obtained supine, upright and after a 3 ng Ang II infusion and a norepinephrine dose response curve. BP and renal plasma flow are assessed in response to the diet and the Ang II infusion and 24 hour urines are collected on each diet. An oral glucose tolerance test is performed on each subject and blood is obtained for DNA. In addition to hypertensives, the nearly 2000 intensively studied cohort consists of 75 individuals in 10 families, 225 sibling pairs with hypertension, 525 normotensive individuals without a family history of hypertension or diabetes before the age of 60, and 250 type II diabetic subjects with or without hypertension. On most of the 4000 subjects serum, plasma, urine and DNA is available for measurements and analyses. Currently the data set consists of approximately 2100 data points of demographic data, family history, biomarkers, and genotypes. The subjects have been recruited from Boston MA, Salt Lake City UT, Paris France, Rome Italy and Nashville TN. The demographics consists of the following: 52% male, 18% of African descent, 3% Asian descent, age 17-66, hypertension stage 1-2, diet or oral medication controlled diabetes (80% of the total diabetics). A few subjects will be recruited from advertisements on the Internet and in local newspapers, from fliers and postings in the hospital, through mailings to households located in the Boston areas and through patient registries at Brigham and Womens Hospital. As an example of the richness of these sources is the Research Patient Data Registry (RPDR). RPDR is a centralized clinical data registry of 2.8 million Brigham and Womens Hospital and Massachusetts General Hospital patients. With approval of the Institutional Review Board, investigators may use the RPDR Data Acquisition Engine to obtain medical record information for patients with a specific diagnosis. Patients who meet inclusion criteria for a specific study can be identified. Potential research subjects may be contacted by his/her physician to inform the patient of the possibility of participating in a research study and to provide the patient with the information for contacting the study personnel. Investigators from Brigham and Womens Hospital may apply to use the RPDR. RPDR contains over 90,000 hypertensives, ages 17-65 years with 13.5 % of African descent and 52.8 % women.

We reported in our studies using the HyperPATH cohort that there was no racial, age or ethnic differences in the salt sensitive blood pressure responses related to Striatin allele variants. Thus, an equal number of females and males and the same proportion of Africans as in the HyperPATH cohort will be studied. Subjects in HyperPATH and those recruited for the new study in this project will have the similar characteristics. The range in age is >17; however, it is anticipated that the clear majority will be between the ages of 40 and 60 years.

Hypertensive patients previously treated will be weaned off medications for two-four weeks except agents that interfere with the renin-angiotensin-aldosterone system (RAAS) are stopped for three months and amlodipine and/or hydrochlorothiazide is added if necessary for blood pressure control until one month before study initiation. Thus, these subjects will match the characteristics of subjects recruited in HyperPATH. They must have a diastolic blood pressure between 95 and 105 mm Hg off medication in each of three screening visits. Subjects with diastolic blood pressures greater than 105 mm Hg or systolic blood pressures greater than 180 mm Hg will be excluded. Subjects with only elevated systolic blood pressure (but diastolic less than 95 mm Hg) will be excluded because such subjects were not in the HyperPATH cohort.

Based on individual statements, subjects with current excessive alcohol use (greater than 12 oz/ETOH/week) or recreational drug use will be excluded. Subjects taking other medications (except thyroid supplements) or weighing more than 150% of an ideal body weight will be excluded. Subjects with other major cardiovascular diseases, diabetes, asthma, or other major medical illness will be excluded. Subjects who smoke will be excluded. In addition, subjects must have normal values for the following screening tests: CBC, serum electrolytes, liver enzymes, TSH, urinalysis, 24-hour urine excretion of catecholamines and cortisol, and ECG. Specifically, estimated GFR must be > 60 ml/min and serum potassium < 5.0 mmol/l. Subjects with hypokalemia while on diuretics will be evaluated for hyperaldosteronism before inclusion in this study. Cushings syndrome will be ruled out clinically, and with a 24-hour urine cortisol if there is clinical uncertainty. For the more difficult question of renal artery stenosis, we will perform renal artery digital subtraction angiogram in patients with hypertension and a two-component abdominal bruit. Patients with greater than 50% renal artery stenosis will be further evaluated, but excluded from this study. Subjects with a known sensitivity to any of the agents, such as amlodipine or eplerenone will be excluded. Women who are pregnant will be excluded and will be dropped from the study if they become pregnant during the study because eplerenone has not been approved for use in pregnancy and the activity of the RAAS is dramatically altered by pregnancy.

The screened, eligible hypertensives will enter a two-week single blind placebo washout phase. Pill count will be used to determine compliance. Those with BP between 145-170/90-109 mmHg and pill count between 80-100% will enter the randomized phase, counseled regarding salt intake, and randomized double blindly into one of our two treatment arms. We will recruit approximately 105 individuals to have 45 individuals in each drug group for analyses. This assumes that we will have 10-15% non-completers.

INCLUSION CRITERIA:

1. rs2540923A allele carrier OR both Striatin rs888083 and rs6744560 risk allele carrier

2. ages >17 years;

3. hypertension as defined by primary physician;

4. not on more than two anti-hypertensives;

5. normal renal, metabolic, electrolyte, complete blood cell count, and lipid profile laboratory tests;

6. if on an angiotensin converting enzyme inhibitor, angiotensin receptor blocker or mineralocorticoid receptor antagonist, needs to be washed out for 3 months.

EXCLUSION CRITERIA:

1. known cardiac disease other than hypertension

2. renal, circulatory or neurologic diseases

3. diabetes; smoking

4. secondary hypertension as indicated by history, physical examination or screening blood and urine tests; any drug therapy, except for anti-hypertensives and replacement thyroid medication.