Novel Methodology to Measure Protein Accumulation

Accumulation of damaged proteins is thought to underlie many degenerative conditions, including aging, diabetes, Alzheimer's disease, cataracts, and others. Over time, proteins can be irreversibly damaged by a variety of factors, such as reactive oxygen species, and without timely degradation they can accumulate and aggregate. We believe this can contribute to the development of chronic degenerative disorders.

The purpose of this study is to develop a novel methodology for measuring protein accumulation and test it in two groups of people: young (18-30 years) and old (≥65 years). This methodology will require that people drink a solution of essential amino acids that includes isotopically labeled L[ring-13C6]phenylalanine. We will then collect blood and muscle samples, to isolate plasma and skeletal muscle proteins. Participants will return to the study center four more times on a weekly interval.

We hypothesize that older proteins, which persisted in circulation and accumulated over time, will have a higher degree of post-translational oxidative damage than newly synthesized proteins.

Study Overview

• Status: Completed
• Conditions: Aging
• Intervention / Treatment: Other: L[ring-13C6]phenylalanine

• Study Type: Observational
• Enrollment (Actual): 24

Contacts and Locations

Study Locations

• United States
  • Minnesota
    • Rochester, Minnesota, United States, 55905
      • Mayo Clinic

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (ADULT, OLDER_ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

• Sampling Method: Probability Sample

Study Population

Two groups of otherwise healthy participants will be recruited: young (18-30 years) and old (≥65 years). We anticipate screening up to 30 individuals for each group (up to 60 total for study) in order to enroll 12 individuals for each group (24 total for study). A high ratio of screened to enrolled participants is necessary due to exclusion criteria and concern about finding healthy older participants and relatively inactive younger participants. An equal number of participants will be enrolled in each group. We will attempt to have an equal number of men and women.

Description

Inclusion Criteria:

• Age 18-30 years
• Age greater than 65 years

Exclusion Criteria:

• Active or uncontrolled cardiovascular disease
• Chronic kidney disease with serum creatinine ≥ 1.4 mg/dL for women and ≥ 1.5 mg/dL for men
• Chronic liver disease (elevation in serum transaminases ≥ 3 times the upper limit of normal)
• Any debilitating chronic illness, including malignancy
• Significant malabsorptive state, including prior gastric bypass surgery or inflammatory bowel disease
• Diabetes mellitus (types 1 or 2) or glucose ≥ 110 mg/dL.
• Obesity (BMI ≥ 31 kg/m2)
• Anticoagulant therapy (warfarin or heparin) or bleeding disorder that increases risk of bleeding during a muscle biopsy.
• Anemia (hemoglobin ≤ 11 g/dL)
• Use of medications known to modulate protein synthesis, mitochondrial function, and/or glucose homeostasis (including β-blockers and corticosteroids).
• Participation in another study where the 13CPhe was administered during the past 6 months.
• Moderate or high level of structured exercise (on average, ≥ 30 minutes per day and ≥ 2 days per week)
• Pregnancy
• Daily use of tobacco products (smoking or chewing); or smoking ≥7 cigarettes per week, on average. Abstinence from tobacco for ≥3 months is required before enrollment in the study.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Young; Healthy adults 18-30 years old	Other: L[ring-13C6]phenylalanine; Oral drink composed of essential amino acids including L[ring-13C6]phenylalanine
Elderly; Healthy adults greater than 65 years old	Other: L[ring-13C6]phenylalanine; Oral drink composed of essential amino acids including L[ring-13C6]phenylalanine

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Isotopic enrichment of plasma and skeletal muscle proteins achieved by oral ingestion of [13C6]-phenylalanine	Administration of an oral amino acid mixture containing isotopically-labeled [13C6]-phenylalanine (13C-Phe) will result in 13C-Phe incorporation into newly synthesized proteins. Measuring isotopic enrichment (IE) of 13C-Phe immediately after administration and weekly for 3 consecutive weeks will allow for estimation of protein accumulation.	3 weeks
Degree of post-translational modifications in plasma and muscle proteins	The abundance of post-translational modifications of plasma and muscle proteins will be measured using mass spectrometry.	3 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assess differences in protein accumulation as a function of age	Use the newly developed methodology to assess whether otherwise healthy older adults (≥65 years old) have greater accumulation of plasma and muscle proteins compared to healthy young adults (18-30 years old).	3 weeks
Assess differences in protein modification/damage as a function of age	The abundance of post-translational modification/damage of plasma and muscle proteins will be measured using mass spectrometry in young (18-30 years old)and older (>65 years old) adults.	3 weeks

Collaborators and Investigators

• Sponsor: Mayo Clinic

Study record dates

Study Major Dates

• Study Start: December 1, 2011
• Primary Completion (ACTUAL): August 1, 2013
• Study Completion (ACTUAL): August 1, 2013

Study Registration Dates

• First Submitted: January 4, 2012
• First Submitted That Met QC Criteria: January 4, 2012
• First Posted (ESTIMATE): January 6, 2012

Study Record Updates

• Last Update Posted (ESTIMATE): April 10, 2014
• Last Update Submitted That Met QC Criteria: April 9, 2014
• Last Verified: April 1, 2014

More Information

Terms related to this study

• Keywords: Aging; Protein accumulation; Protein damage
• Other Study ID Numbers: 11-004969