Nitric Oxide Flux and Ureagenesis in Argininosuccinate Synthetase Deficiency (ASSD)(Citrullinemia I) (NOASSD)

RDCRN 5110, Nitric Oxide Flux and Ureagenesis in Argininosuccinate Synthetase Deficiency (ASSD)(Citrullinemia I)(Version 24Feb12, NIH Approved 4/5/2012)

The urea cycle consists of a series of chemical reactions through which the body converts toxic waste- nitrogen into a substance called urea that can be disposed of easily. While disposal of nitrogen is the major function of the urea cycle, recent research has shown that some enzymes of the urea cycle are also important for the production of nitric oxide. Nitric oxide is an important chemical that has many functions in the human body including regulation of blood pressure. Through this study, the investigators will study the production of nitric oxide in subjects with citrullinemia type 1 by administering stable isotopes to these subjects. Stable isotopes are harmless compounds that can be used to track and measure the production of specific compounds in the human body. The overall goal of this study is to understand if citrullinemia patients have a deficiency of nitric oxide production. This knowledge may have an impact on the treatment of patients with citrullinemia.

Study Overview

• Status: Completed
• Conditions: Citrullinemia
• Intervention / Treatment: Other: stable isotope infusion

Detailed Description

This is an interventional, case control study to investigate the production of nitric oxide in patients with citrullinemia type I. Through the infusion of isotopes [15N2-ureido] arginine, [5-13C,4, 4, 5, 5-D4] citrulline, [15N]citrulline, 15N sodium nitrate and [15N][18O3] potassium nitrate, the flux of citrulline and nitrate through the urea cycle pathway will be measured in conjunction with an independent measure of total plasma arginine flux. This will be informative in dissecting the contributions of de novo production of arginine vs. exogenous contribution of arginine into total body NO flux. Total body urea production will be measured by the isotopic dilution of constantly infused [18O][13C]urea. These flux measurements will be correlated with the level of residual enzyme activity and clinical phenotype in these citrullinemia patients. The investigators plan to enroll three patients with citrullinemia.

Three unaffected control subjects will also be studied.

• Study Type: Interventional
• Enrollment (Actual): 6
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Texas
    • Houston, Texas, United States, 77030
      • Baylor College of Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Participants must be adults (18 years and older) with confirmed diagnosis of Argininosuccinate Synthetase Deficiency (ASSD) (Citrullinemia I) who are able to perform study procedures.
• Diagnosis of citrullinemia I must be confirmed by a >10 fold elevation of citrulline in plasma and/or decreased AS enzyme activity in cultured skin fibroblasts or other appropriate tissue and/or identification of pathogenic mutation in the AS gene.
• Subject must be able to take oral or G-tube medication and have a history of adequate compliance of diet and treatment.
• If a woman of child bearing potential and sexually active, participant agrees to use an acceptable method of birth control.
• Most recent serum creatinine level must be less than or equal to 1.5 mg/dl. Serum creatinine measurement may be performed at the subject's local laboratory, but must have been obtained within one year of enrollment.
• Participant agrees to travel to Baylor College of Medicine for the study.
• Control subjects must be over eighteen years of age with no chronic or acute health issues.

Exclusion Criteria:

• Pregnancy, current acute illness and current hyperammonemic episode.

Study Plan

How is the study designed?

Design Details

• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: stable isotope infusion; Infusion of isotopes [15N2-ureido] arginine, [5-13C,4, 4, 5, 5-D4] citrulline, [15N]citrulline, 15N sodium nitrate and [15N][18O3] potassium nitrate,[18O][13C]urea.

Other: stable isotope infusion; Control subjects: [15N2-ureido] arginine (0.69 mg/kg); [5-13C,4,4,5,5-D4] citrulline (0.18mg/kg); 15N citrulline (0.03mg/kg); 15N sodium nitrate (0.003 mg/kg), [15N][18O3] potassium nitrate (0.03 mg/kg) and [18O][13C]urea (1 mg/kg)over 10 minutes. Followed by a 8-hour infusion of [15N2-ureido] arginine (0.69 mg/kg/hr); [5-13C,4,4,5,5-D4] citrulline (0.18mg/kg/hr), [15N][18O3] potassium nitrate (0.003 mg/kg/hr) and [18O][13C]urea (0.1 mg/kg/hr). Citrullinemia type 1 subjects,[15N2-ureido] arginine (4.14 mg/kg); [5-13C,4,4,5,5-D4] citrulline (1.08 mg/kg); 15N citrulline (0.18mg/kg); 15N sodium nitrate (0.003 mg/kg), [15N][18O3] potassium nitrate (0.03 mg/kg) and [18O][13C]urea (1 mg/kg)over 10 minutes, followed by a 8-hour infusion of [15N2-ureido] arginine (4.14 mg/kg/hr); [5-13C,4,4,5,5-D4] citrulline (1.08 mg/kg/hr), [15N][18O3] potassium nitrate (0.003 mg/kg/hr) and [18O][13C]urea (0.1 mg/kg/hr).; Other Names: stable isotopes

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Flux of citrulline and nitrate through the urea cycle pathway will be measured in conjunction with an independent measure of total plasma arginine flux.	Endpoint data to be collected include measurement of isotopic enrichments drawn at 0, 6, 7 and 7.5 hours of infusion. Measurements will include urea, carbon-arginine, guanido-arginine, citrulline, nitric oxide, nitrate and 15N-nitrate.	0, 6, 7 and 7.5 hours of infusion

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Total body urea production will be measured by the isotopic dilution of constantly infused [18O][13C]urea.	Endpoint data to be collected include measurement of isotopic enrichments drawn at 0, 6, 7 and 7.5 hours of infusion. Measurements will include urea, carbon-arginine, guanido-arginine, citrulline, nitric oxide, nitrate and 15N-nitrate.	0, 6, 7 and 7.5 hours of infusion

Collaborators and Investigators

• Sponsor: Baylor College of Medicine
• Investigators: Principal Investigator: Brendan Lee, MD, PhD, Baylor College of Medicine

Publications and helpful links

Helpful Links

• Baylor College of Medicine Website

Study record dates

Study Major Dates

• Study Start: December 1, 2012
• Primary Completion (Actual): September 1, 2013
• Study Completion (Actual): September 1, 2013

Study Registration Dates

• First Submitted: May 30, 2012
• First Submitted That Met QC Criteria: May 31, 2012
• First Posted (Estimate): June 1, 2012

Study Record Updates

• Last Update Posted (Estimate): March 20, 2015
• Last Update Submitted That Met QC Criteria: March 18, 2015
• Last Verified: March 1, 2015

More Information

Terms related to this study

• Keywords: nitric oxide; urea; citrullinemia; argininosuccinate synthetase deficiency
• Additional Relevant MeSH Terms: Metabolic Diseases; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Genetic Diseases, Inborn; Metabolism, Inborn Errors; Brain Diseases, Metabolic; Brain Diseases, Metabolic, Inborn; Amino Acid Metabolism, Inborn Errors; Urea Cycle Disorders, Inborn; Citrullinemia
• Other Study ID Numbers: H-27226