Effects of Different Forms of a Natural Heart Hormone on Blood Pressure and Fluid Balance in Healthy Volunteers

Effects of Glycosylated Atrial Natriuretic Peptide on Blood Pressure and Fluid Balance in Healthy Volunteers

The human heart produces hormones that help regulate blood pressure and fluid balance in the body. One of these hormones is atrial natriuretic peptide (ANP). ANP lowers blood pressure by relaxing blood vessels and increasing urinary excretion by the kidneys.

Previous research has demonstrated that ANP naturally carries a small sugar molecule attached. This sugar moiety is produced endogenously and can modify the biological activity of ANP. When this sugar is present, ANP may affect blood vessels and renal function differently compared with the non-glycosylated form.

The present study examines how this sugar modification alters the physiological effects of ANP. This is achieved by administering ANP, either with or without the attached sugar molecule, via intravenous infusion. The study aims to determine whether glycosylated ANP differs from the native form in its effects on blood pressure and fluid balance.

Study Overview

• Status: Completed
• Conditions: Heart Failure; Hypertension; Kidney Failure
• Intervention / Treatment: Other: Infusion of two different cardiac peptides plus vehicle

Detailed Description

Introduction Atrial natriuretic peptide (ANP) is a critical component of the natriuretic peptide family and plays a central role in cardiovascular homeostasis. ANP is primarily synthesized and secreted by atrial myocytes in response to atrial stretch and related stimuli. The peptide exerts biological effects through binding to specific receptors, leading to activation of A-type guanylyl cyclase (GC) (also known as NPR-A) and subsequent production of cyclic guanosine monophosphate (cGMP). This signaling cascade induces vasodilation, natriuresis, and diuresis, thereby contributing to regulation of blood pressure and fluid balance.

The concept of proteoforms refers to the various molecular forms that a protein can assume, arising from genetic variation, alternative splicing, and post-translational modification. ANP proteoforms therefore comprise molecular variants of ANP with potentially distinct biological activities and clinical implications.

ANP proteoforms have diagnostic and prognostic value in cardiovascular disease. Elevated ANP and related peptides indicate increased cardiac stress and are observed in conditions such as heart failure, hypertension, and acute coronary syndromes. Measurement of ANP, together with B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP), is widely used in clinical practice to assist diagnosis and guide management (Volpe 2021).

Beyond diagnostic utility, ANP possesses therapeutic potential. Vasodilatory and natriuretic properties make ANP an attractive candidate for treatment of conditions associated with fluid overload and hypertension. Recombinant ANP analogues have been used clinically in acute heart failure.

Recent advances highlight strategies to enhance natriuretic peptide activity. Inhibition of neprilysin prolongs peptide half-life and biological effect. Combined neprilysin inhibition and angiotensin receptor blockade has demonstrated clinical benefit in heart failure (McMurray 2013).

Post-translational modification, including glycosylation, further diversifies ANP function. Glycosylated ANP refers to peptide forms containing covalently attached carbohydrate groups, typically linked to serine or threonine residues. This modification alters receptor binding, biological activity, and resistance to proteolytic degradation. Glycosylation may therefore influence the physiological and therapeutic profile of ANP. Recent observations suggest that glycosylation modulates interaction with natriuretic peptide receptors and downstream signaling pathways (Hansen 2019).

Objectives, Hypothesis, and Endpoints The primary objective of the study is to clarify the physiological significance of glycosylated ANP in humans.

The primary hypothesis is that glycosylated ANP regulates blood pressure without inducing diuresis.

Primary endpoints include diuresis and natriuresis during intervention. Secondary endpoints include changes in blood pressure and plasma and urinary concentrations of natriuretic peptides, renin-angiotensin-aldosterone parameters, electrolytes, cyclic nucleotides, metabolic substrates, stress hormones, and amino acids.

Methods and Study Design The study is designed as a randomized, double-blind, placebo-controlled crossover investigation. Each participant acts as an individual control. Randomization assigns infusion with ANP, glycosylated ANP (gANP), or saline on separate study days.

Following written informed consent, screening is performed after overnight fasting and includes clinical assessment, laboratory evaluation, and urine testing.

On study days, participants are admitted after a 10-hour fast. Procedures include bladder emptying, venous catheter placement, baseline sampling, and continuous blood pressure monitoring. Infusions of ANP, gANP, or saline are administered according to protocol.

Blood samples are obtained at predefined intervals, and urine is collected during and after infusion. Ultrasonographic assessment of vascular parameters and bladder volumes is performed where applicable.

Study Population Inclusion criteria comprise healthy male individuals aged 18-30 years with normal body mass index and hemoglobin levels.

Exclusion criteria include recent illness, chronic disease, hypotension, smoking, substance abuse, recent blood donation, and medication use incompatible with study requirements.

Safety and Ethics Both ANP and gANP are associated with blood pressure reduction. Continuous monitoring is implemented, and infusion is discontinued if symptomatic hypotension occurs.

The study is conducted in accordance with ethical guidelines, with approval from the relevant ethics committee.

Biobank and Data Handling Biological samples are coded and stored according to regulatory requirements. Analyses are performed at designated institutions, and remaining material is handled in accordance with approved protocols.

Funding and Registration The study is supported by Innovation Fund Denmark. A patent application related to glycosylated ANP has been filed.

Trial registration was completed following recognition of registry requirements, with all study parameters finalized prior to participant enrollment and approved by the ethics committee.

• Study Type: Interventional
• Enrollment (Actual): 17
• Phase: Early Phase 1

Contacts and Locations

Study Locations

• Denmark
  • Copenhagen, Denmark, 2400
    • 4) Department of Clinical Pharmacology, Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen, Denmark

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy male volunteers
• Age: 18-30 years
• BMI: 20-25 kg/m²
• Body weight ≤90 kg (amended protocol)
• Normal hemoglobin
• Ability to provide informed consent

Exclusion Criteria:

• Acute illness within two weeks
• Chronic cardiovascular, renal, hepatic, pulmonary, metabolic or malignant disease
• Hypotension or history of syncope
• Smoking
• Substance or alcohol abuse
• Recent blood donation (<3 months)
• Medication that cannot be safely interrupted

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Atrial Natriuretic Peptide (ANP) - a well described cardiac hormone; Atrial Natriuretic Peptide (ANP) Participants receive an intravenous infusion of native atrial natriuretic peptide (ANP), a naturally occurring heart hormone known to lower blood pressure by relaxing blood vessels and increasing salt and water excretion by the kidneys. ANP is administered at a fixed weight-adjusted dose over a defined infusion period, followed by post-infusion observation and monitoring of blood pressure, urine output, and blood markers.	Other: Infusion of two different cardiac peptides plus vehicle; Interventions Original protocol: ANP: 200 pmol/kg/min for 120 minutes gANP: 200 pmol/kg/min for 120 minutes Amended protocol: ANP: 200 pmol/kg/min for 60 minutes gANP: 300 pmol/kg/min for 60 minutes Control: Saline infusion at 0.7 mL/kg/hour
Experimental: Glycosylated Atrial Natriuretic Peptide (gANP) - a naturally occurring modified cardiac hormone; Participants receive an intravenous infusion of glycosylated atrial natriuretic peptide (gANP), a naturally occurring sugar-modified form of ANP. Glycosylation alters the stability and biological activity of the hormone. gANP is administered at a weight-adjusted dose comparable to or slightly higher than native ANP, according to protocol amendments, with the same monitoring procedures. The purpose is to assess whether the sugar-modified form produces different effects on blood pressure, fluid balance, and vascular function compared with native ANP.	Other: Infusion of two different cardiac peptides plus vehicle; Interventions Original protocol: ANP: 200 pmol/kg/min for 120 minutes gANP: 200 pmol/kg/min for 120 minutes Amended protocol: ANP: 200 pmol/kg/min for 60 minutes gANP: 300 pmol/kg/min for 60 minutes Control: Saline infusion at 0.7 mL/kg/hour
Placebo Comparator: Placebo (Saline); Participants receive an intravenous infusion of isotonic saline at a low, weight-adjusted rate. This arm serves as a placebo control to account for the effects of the infusion procedure, time, and study conditions. The volume administered is equal to both of the active days. All measurements and observations are identical to those performed during the active intervention arms.	Other: Infusion of two different cardiac peptides plus vehicle; Interventions Original protocol: ANP: 200 pmol/kg/min for 120 minutes gANP: 200 pmol/kg/min for 120 minutes Amended protocol: ANP: 200 pmol/kg/min for 60 minutes gANP: 300 pmol/kg/min for 60 minutes Control: Saline infusion at 0.7 mL/kg/hour

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Diuresis and natriuresis	Primary Objective Diuresis and natriuresis are quantified immediately after conclusion of peptide/placebo administration and repeated after an additional two hours of observation.	Collection and quantification will take place after completion of two hours of peptide/placebo administration and again after two hours of observation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood pressure	Blood pressure will be measured during infusion and observation on all experimental days.	Measurement will take place every ten minutes throughout the experimental day.
Metabolic markers	Metabolic markers in plasma will be quantified (listed in detailed description) in plasma	During and after infusion of peptide/placebo with 20-30 min interval.
cyclic GMP	Concentration of the second messenger, cGMP, in plasma and urine.	Quantification will take place once every hour (plasma) and every two hours (urine)

Collaborators and Investigators

• Sponsor: Peter Fruergaard Andersen
• Collaborators: Rigshospitalet, Denmark; University Hospital Bispebjerg and Frederiksberg; Region Hovedstadens Apotek
• Investigators: Principal Investigator: Katrine T-B Schjoldager, Associate Professor, Department of Cellular and Molecular Medicine, University of Copenhagen

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2022
• Primary Completion (Actual): March 30, 2023
• Study Completion (Actual): March 30, 2026

Study Registration Dates

• First Submitted: April 28, 2026
• First Submitted That Met QC Criteria: May 15, 2026
• First Posted (Actual): May 26, 2026

Study Record Updates

• Last Update Posted (Actual): May 26, 2026
• Last Update Submitted That Met QC Criteria: May 15, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: ANP, atrial natriuretic peptide; glycosylation, post-translational modification, peptide
• Additional Relevant MeSH Terms: Urogenital Diseases; Vascular Diseases; Cardiovascular Diseases; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Heart Diseases; Heart Failure; Hypertension; Renal Insufficiency; Atrial Fibrillation, Familial, 6
• Other Study ID Numbers: 77354/H-21000305

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No