Effect of Acetaminophen and N-Acetylcysteine on Liver Metabolism on Homocystinuria

Functional Consequences and Therapeutic Intervention in Hampered Production of Cysteine, Glutathione and Taurine in Classical Homocystinuria

In homocystinuria due to cystathionine beta synthase (CBS) deficiency or classical homocystinuria, decreased blood cysteine levels are observed. Cysteine is essential for the synthesis of molecules such as glutathione and taurine. Main functions of glutathione are to detoxify drugs and to scavenge reactive oxygen species. N-acetylcysteine is a commercially available drug chemically similar to cysteine. In CBS deficient animal models, N-acetylcysteine supplementation improves cysteine and liver glutathione concentrations. N-acetylcysteine also acts directly as a scavenger of free radicals. In CBS deficiency, increased oxidative damage has been described and possibly contributes to the clinical manifestations of CBS deficiency. Acetaminophen (Paracetamol) is a common painkiller and its overdose (>4 g/day) is a major cause of acute liver failure. Glutathione is required for Acetaminophen detoxification, and the preferred treatment for an overdose is the administration of N-acetylcysteine.

The aim of this study is to demonstrate that CBS deficiency patients have glutathione depletion and to investigate if Acetaminophen can induce subclinical liver damage and if N-acetylcysteine supplementation could prevent the toxic-effects of acetaminophen.

The investigators' hypothesis is that CBS deficiency patients have an inadequate supply of cysteine for the glutathione synthesis, which impairs antioxidants defenses and increases risk of intoxication of drugs that require glutathione, such as Acetaminophen. This potential increased liver toxicity induced by drugs or other xenobiotics that are detoxified by the glutathione pathway has not been explored in CBS deficiency patients. The experiments should provide answers about the functional role of cysteine and glutathione depletion in CBS deficiency and if N-acetylcysteine might have a place as an adjunct therapy for CBS deficiency.

Study Overview

• Status: Suspended
• Conditions: CBS Deficiency
• Intervention / Treatment: Drug: Acetaminophen; Drug: N-acetylcysteine

Detailed Description

STUDY PROCEDURES

A phase I-II clinical cross-over, not blinded, trial will be conducted. Adult patients with homocystinuria and paired-sex and age- healthy controls will be enrolled. Individuals with hepatic, renal or gastric disease; smokers, illicit drugs users or those who are hypersensitive to any of the components of the drugs tested (acetaminophen and N-acetylcysteine ) will be excluded.

Patients will be submitted to two procedures:

Step 1: In this stage, individuals will receive a single standard dose of Acetaminophen (1.5g) orally and blood samples will be drawn at time 0, 2, 4, 6 and 8 hours after the administration.

Step 2: In this stage, individuals will receive again a normal dose of acetaminophen (1.5g) orally and one hour later a single dose of oral N-acetylcysteine (70 mg per kilogram of body weight)(. Blood samples will be drawn at the same points.

In plasma we will measure methionine, homocysteine, cysteine and glutathione by LC-MS/MS. Taurine will also be determined by Biochrom 30 Amino Acid Analyser. Pyroglutamate will be determined as a marker for glutathione depletion.

As markers of oxidative stress we will assay thiobarbituric acid-reactive substances, protein carbonyl content, thiol content, DNA damage 2',7'-dichlorofluorescein fluorescence assay, and activities of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase . Liver function parameters aspartate transaminase (AST) and alanine transaminase (ALT) activities will also be determined.

All measurements will be performed at all 5 points of blood collection and in the two stages of the trial.

• Study Type: Interventional
• Enrollment (Anticipated): 10
• Phase: Phase 2; Phase 1

Contacts and Locations

Study Locations

• Brazil
  • RS
    • Porto Alegre, RS, Brazil, 90035-007
      • Hospital de Clínicas de Porto Alegre

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Age over 18 years
• For patients: molecular diagnosis of homocystinuria due to cystathionine beta synthase (CBS) deficiency

Exclusion Criteria:

• Gastric, hepatic or kidney disease
• Smoking
• Illicit drug users;
• Acetaminophen or N-acetylcysteine hypersensitivity.
• Controls: use of vitamins supplements

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Acetaminophen; Adult patients with homocystinuria due to cystathionine beta synthase (CBS) deficiency and controls will receive a single dose of Acetaminophen (1.5g) orally. Blood will be drawn at time 0, 2, 4, 6 and 8 hours after the acetaminophen dose.	Drug: Acetaminophen; Adult patients with homocystinuria due to cystathionine beta synthase (CBS) deficiency and controls will receive a single dose of Acetaminophen (1.5g) orally. Blood will be drawn at time 0, 2, 4, 6 and 8 hours after the acetaminophen dose to measure liver enzymes and markers of oxidative stress.; Other Names: paracetamol
Experimental: Acetaminophen + N-acetylcysteine; Patients with homocystinuria due to cystathionine beta synthase (CBS) deficiency and controls will receive again a normal dose of acetaminophen (1.5g) orally and one hour later oral N-acetylcysteine (70 mg per kilogram of body weight). Blood will be drawn at time 0, 2, 4, 6 and 8 hours after the acetaminophen dose.	Drug: Acetaminophen; Adult patients with homocystinuria due to cystathionine beta synthase (CBS) deficiency and controls will receive a single dose of Acetaminophen (1.5g) orally. Blood will be drawn at time 0, 2, 4, 6 and 8 hours after the acetaminophen dose to measure liver enzymes and markers of oxidative stress.; Other Names: paracetamol; Drug: N-acetylcysteine; Patients with homocystinuria due to cystathionine beta synthase (CBS) deficiency and controls will receive again a normal dose of acetaminophen (1.5g) orally and one hour later oral N-acetylcysteine (70 mg per kilogram of body weight). Blood will be drawn at time 0, 2, 4, 6 and 8 hours after the acetaminophen dose to measure liver enzymes and markers of oxidative stress.; Other Names: NAC

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in aspartate transaminase (AST) in 4 hours	A difference >30% between pre and pos Acetaminophen administration will be considered clinically significant.	4 hours
Change in aspartate transaminase (AST) in 6 hours	A difference >30% between pre and pos Acetaminophen administration will be considered clinically significant.	6 hours
Change in alanine transaminase (ALT) in 4 hours	A difference >30% between pre and pos Acetaminophen administration will be considered clinically significant.	4 hours
Change in alanine transaminase (ALT) in 6 hours	A difference >30% between pre and pos Acetaminophen administration will be considered clinically significant.	6 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in sulfhydryl levels in 2 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	2 hours
Change in sulfhydryl levels in 4 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	4 hours
Change in sulfhydryl levels in 6 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	6 hours
Change in sulfhydryl levels in 8 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	8 hours
Change in plasma GST activity in 2 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	2 hours
Change in plasma GST activity in 4 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	4 hours
Change in plasma GST activity in 6 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	6 hours
Change in plasma GST activity in 8 hours	A difference >30% between pre and pos measurements will be considered clinically significant.	8 hours

Collaborators and Investigators

• Sponsor: Hospital de Clinicas de Porto Alegre
• Collaborators: Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, Brazil
• Investigators: Principal Investigator: Ida VD Schwartz, PhD, Professor

Study record dates

Study Major Dates

• Study Start (Anticipated): February 11, 2022
• Primary Completion (Anticipated): June 30, 2022
• Study Completion (Anticipated): December 1, 2022

Study Registration Dates

• First Submitted: May 28, 2019
• First Submitted That Met QC Criteria: July 9, 2019
• First Posted (Actual): July 11, 2019

Study Record Updates

• Last Update Posted (Actual): June 30, 2021
• Last Update Submitted That Met QC Criteria: June 25, 2021
• Last Verified: June 1, 2021

More Information

Terms related to this study

• Keywords: Acetaminophen; N-acetylcysteine; Glutathione; Homocysteine; Homocystinuria; Cysteine
• Additional Relevant MeSH Terms: Metabolic Diseases; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Genetic Diseases, Inborn; Connective Tissue Diseases; Metabolism, Inborn Errors; Brain Diseases, Metabolic; Brain Diseases, Metabolic, Inborn; Amino Acid Metabolism, Inborn Errors; Hyperhomocysteinemia; Homocystinuria; Physiological Effects of Drugs; Molecular Mechanisms of Pharmacological Action; Anti-Infective Agents; Peripheral Nervous System Agents; Antiviral Agents; Analgesics; Sensory System Agents; Analgesics, Non-Narcotic; Antipyretics; Protective Agents; Respiratory System Agents; Antioxidants; Antidotes; Free Radical Scavengers; Expectorants; Acetaminophen; Acetylcysteine; N-monoacetylcystine
• Other Study ID Numbers: 20180677; 34863.494.21707.15062018 (Other Identifier: FAPERGS/CAPES)

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