Specializing solely in post-acute brain injury since 1982

Amino Acid Prevalence and Chronic Brain Injury

Association of Amino Acid Prevalence and Chronic Brain Injury

The Transitional Learning Center participates in Amino Acid study

  1. Introduction and Purpose:

The purpose of this study is to evaluate the levels of Amino Acids in adult individuals with chronic (> 2 years) traumatic brain injury (TBI) when compared to a non-brain injured cohort population.Amino study.jpg

Preliminary data from an assay of amino acids in individuals with chronic TBI compared to an assay of individuals without a TBI revealed significantly lower concentrations of amino acids within the TBI group at baseline, as well as a significantly lower amount of amino acid metabolism. This decreased metabolism and resulting concentrations of amino acids may be due to the microbiota present in the lower gastrointestinal tract.

The composition and structure of the fecal microbiome will be determined by 16S rDNA sequencing. Taxonomic and community structure profiles will be treated as outcome variables and modeled together with the participant’s plasma amino acid concentration, years post-injury, age, sex and other variables to determine correlations. These correlations may improve our understanding of the diminished amino acid metabolism within the chronic TBI population.

The endpoint will identify the microbiome structure and composition within the TBI and healthy participants and to assess the participant’s amino acid concentrations and other participant demographics and phenotypic characteristics (years post-injury, age, sex). This comparison may improve our understanding of the diminished amino acid metabolism within the chronic TBI population.

The risks are those related to venipuncture only, as described below.

  1. Background:

A 2006 survey by the National Foundation for Brain Research shows that there are approximately two million TBI cases every year in the United States with 25% requiring hospitalization. Of these, approximately 70,000 to 90,000 suffer long-term disabilities while 100,000 die from their injuries. The estimated direct (e.g., hospital) and indirect (e.g., loss of productivity) costs are $6 billion and $42 billion respectively. In addition to being a serious health problem amongst civilians, the incidence of head traumas creates a greater burden of care amongst the families of those affected.

Individuals with chronic traumatic brain injuries are susceptible to a whole host of medical issues. Approximately one in three individuals with a TBI reports a medical decline over time 10 years after their TBI. Corrigan, Archives of Physical Medicine and Rehab, 2013. The concept that a brain injury is the beginning of a disease process has been accepted by most researchers and clinicians who dealt with TBI. Masel and Dewitt, J. Neurotrauma, 2010.  Individuals with a TBI are twice as likely to die (one year after their injury) as their uninjured cohort, and have a life expectancy reduction of approximately 7 years. The most common cause of death is an infectious process. Harrison-Felix. Archives of PMR, 2009.  When compared to the uninjured cohort, individuals with a TBI are at greater risk for developing neurodegenerative disease, dementia, Parkinsonism, psychiatric disease, and systemic metabolic dysfunction. There are many theories as to why these individuals decline. There are many theories as to the cause, but they are just theories.

Amino acids are the building blocks of proteins and precursors for brain neurotransmitters. The human body requires certain amino acids known as non-essential amino acids (NEAA) and essential amino acids (EAA); NEAA are produced within the body, but EAA must be consumed. Under normal conditions, the brain can synthesize NEAA, but it depends on the transport of blood to receive EAA. Aquilani et al. (Arch Phy Med Rehabil, 2003) reported lower concentrations of several EAA in patients with subacute TBI (average 1.5 months post injury) when compared to a healthy population. Aquilani et al (Arch Phy Med Rehabil, 2006) subsequently studied amino acid levels in individuals who were 3.5 months post injury.  Levels of several essential amino acids as well as tyrosine remained low. In a study done at TLC, Borsheim et al (Arch Phy Med Rehabil 2007) studied subjects averaging 15 months post injury, (eating ad lib) measuring baseline concentrations of the amino acids and then amino acid levels following amino acid supplementation. Many abnormalities were present at baseline, and after supplementation, there were still low levels of valine, alanine and glutamine. A study is presently underway at TLC looking at physical and cognitive changes after broad amino acid supplementation, as well as supplementation with only valine.

The disruption of EAA concentrations after TBI may cause the increased muscle fatigue that is a common issue in the TBI population, and if left untreated, may lessen the quality of recovery and perpetuate the chronic characteristics of TBI. If the disruption of AA concentrations persists into the chronic phase of TBI, this data may give insight into the chronic disease process. This may lead to dietary changes for patients to correct this deficiency.

Currently, there are no published studies on amino acid levels in individuals with chronic TBI. Preliminary data from this study has shown significantly lower concentrations of amino acids amongst participants with a chronic TBI. However, the cause of these diminished levels of amino acids is still unknown.

The human body is host to site-specific microbiomes that contribute to an overall state of health. The composition and structure of the microbiomes vary across sites and individuals. Factors such as age, nutrition, physiology, immune status, among others, have great impact in shaping these bacterial communities.  We propose to characterize the microbiomes associated with stool, saliva, and oral mucosa of participant’s who have suffered a chronic TBI and compare them to healthy controls.

The microbiota that reside in the human body form communities that are found mainly in skin and mucosal surfaces of the mouth, nose, gastrointestinal track and vagina. These bacterial communities differ between people and variations are determined by several factors such as nutrition, physiology, immunity and may have an impact in health and disease. We will collect human samples from stool, saliva, and epithelial cells from inside the mouth of participant’s who have suffered a chronic TBI and compare them to healthy controls. 

  1. Concise Summary of Project:

The purpose of this study is to evaluate whether or not individuals who are disabled as a result of a chronic TBI have developed altered levels of amino acids when compared to a non-brain injured cohort. Furthermore, to identify possible processes that are responsible for the altered levels of amino acids. We suspect the microbial communities within TBI survivors may differ from that of healthy individuals, and this difference may directly affect amino acid metabolism. 

  1. Study Procedures:

Tideway is a long term assisted living program for individuals who are disabled due to issues related to a brain injury. These individuals are incapable of living independently due to ongoing medical issues, cognitive issues or both. Some have their own medical power of attorney. Some have a family member with a medical power of attorney. Tideway is a program of the TransitionalLearningCenter (a post-acute brain injury treatment program).  Many of the individuals who now reside at Tideway had received rehabilitation at TLC and are followed by TLC therapists and staff. 

Brent Masel (the PI on this proposal) is the administrator and medical director of Tideway (and TLC), and thus has a unique perspective and relationship with the residents and their families, as he functions as their physician.  The cohort for the study will come from Tideway. The control group will be recruited from Tideway and TLC staff.

Ten individuals with chronic TBI and 10 healthy age matched control healthy volunteers will fast for eight hours and then consume a predetermined breakfast. Ninety minutes after completing the breakfast, a physician or nurse will collect a blood sample for analysis. A sample of approximately 2 cc of blood will be withdrawn by venipuncture from one of the forearm veins and collected into a 4.7 cc yellow top vacutainer.

Oral epithelial cell samples will be collected via buccal swab. These samples will be coded, refridgerated, and transported to Dr. Nadim Ajami’s lab in the AlkekCenter for Metagenomics and Microbiome Research at Baylor College of Medicine in Houston, Texas. After analysis, these samples will be destroyed.

Stool samples will be collected using a feces catcher (www.fecescatcher.com) and subsequently transferred to a stool-stabilizing kit (OMNIgeneGut, DNAGenotek).  Stool samples will be coded, refrigerated, and transported to Dr. Nadim Ajami’s lab in the AlkekCenter for Metagenomics and Microbiome Research at Baylor College of Medicine in Houston, Texas. After analysis, these samples will be destroyed.

Blood will be coded, refrigerated, and transported to Dr. Melinda Moore’s lab at UTMB. After analysis, these samples will be destroyed.

All genetic information from the participants will be stripped from the samples during analysis and never linked to the participants’ identities.

Data to be collected includes:

Age for both TBI and controls

Gender for both TBI and controls

Medications for both TBI and controls

Medical history for both TBI and controls

Probiotic use for both TBI and controls

Ambulatory status for both TBI and controls

Glascow Coma Scale for TBI group

Description of the injury (mechanism of injury, blast, non-penetrating, mild/moderate/severe)

Note: The information collected on the subjects with TBI already is present in the TLC/Tideway medical records. There will no need for further record gathering.

  1. Sub-Study Procedures:


  1. Criteria for Inclusion of Subjects:

Blood and stool from healthy volunteers and from patients with chronic TBIs will be used in this study. Tideway has a heterogeneous population reflecting the local demographics. Brain injury, however, is more frequent in males, so it is anticipated that a higher percentage of males will be enrolled in the study. However, no exclusion of females is intended and all residents will have the opportunity to participate. None of the females at Tideway are pregnant or of child bearing age/potential. This study is limited to adults only, ages 21-65.



Chronic TBI patients should have a history of:

Head trauma greater than two years prior manifesting in one or more of the following:

a. Loss of consciousness

b. Post-traumatic amnesia

c. Focal neurologic deficits, seizure

d. Persistent symptoms of increased arousal (e.g., difficulty falling or staying asleep, anger and hypervigilance)

e. Impairment in cognitive, social, occupational, or other important areas of functioning (e.g., problems with work and relationships.) 

  1. Criteria for Exclusion of Subjects: 

Patients will be excluded from the study if we are unable to obtain informed consent, less than 21 years of age, or more than 65 years of age. 

  1. Sources of Research Material: 

Tideway (6444 Central City Blvd) is a long term living program for individuals with chronic brain injuries. The TransitionalLearningCenter (1528 Postoffice Street) is a post- acute brain injury treatment program. Tideway is a program of TLC. Blood will be drawn at Tideway and TLC by our nurses who have extensive experience at venipuncture. Blood studies will be done at Dr. Moore’s lab at UTMB. Microbiome studies will be done at the AlkekCenter for Metagenomics and Microbiome Research at the Baylor College of Medicine. Bacterial DNA will be extracted from all samples in an automated and high-throughput manner. Subsequently, the v4 region of the 16S rRNA gene will be amplified and sequenced to determine the composition and structure of the stool and oral micorbiomes. .

The majority of medical information to be gathered and used for this study from the subjects already exists in the TLC/Tideway charts. Other information needed will be gathered after consent is obtained. 

  1. Recruitment Methods and Consenting Process: 

It is clear that the individuals to whom this research is aimed would be considered vulnerable. So as to not lend to subject coercion, Dr. Masel will not approach the residents regarding this study, but will be available to answer specific questions. The research coordinator, Jack Foreman, will present the study to the residents and their families and/or the legal authorized representative, and will do the consenting. As even individuals residing at Tideway who are their own medical power of attorney and/or guardians are of diminished capacity, it is Tideway’s policy to always include the patient’s next of kin in any major medical decision.  In that situation, all subject consents will also include the consent of the next of kin.

Patients will be informed that participation in the study and donation of a blood sample is voluntary and in no way will influence the care they will receive by their physician and Tideway staff.

Participants that have already given consent to donate blood will be informed of the additional sample requests and the rationale that motivates these requests. Their continued participation is still voluntary, but if they agree to continue, they will be required to provide consent for the new sample collection. 

  1. Potential Risks: 

The risks are those associated with venipuncture 

  1. Subject Safety and Data Monitoring: 

Blood will be drawn by our nurse or our physician with extensive experience in venipuncture. 

  1. Procedures to Maintain Confidentiality: 

Data will be in password protected files and stored in locked cabinets in the TLC office suites and will be shredded prior to disposal. Only those investigators actively involved in the project will have access to the data. Subject identities will not be revealed in any description or publication of the research for scientific purposes.

No known additional risks exist outside of those associated with routine care and blood sampling. As this is an observational study and no interventions will be done other than obtaining blood samples, no data safety monitoring board is necessary. Patient identity will be concealed. Samples of blood will be given a registration code which will be used to identify the sample. The registration code will be linked to a database containing the medical information described above. A linking list will be maintained to separate identifiers from data and samples.

Oral and stool samples will be coded upon collection so that when transferred to Alkek Center for Metagenomics and Microbiome Research at Baylor College of Medicine there will be no identifiable information associated with the samples. For microbiome analysis, no host DNA will be amplified or sequenced. The microbiome analysis will return to the PI without host-genetic information. 

  1. Potential Benefits: 

Patients will be informed of the amino acid concentrations present in their blood and the concentration of certain bacteria in their GI tract. If these concentrations are significantly different than those of the healthy population, the patients may receive dietary advice to help correct the differences. By maintaining normal amino acid concentrations, patients may experience an increase in their general health. 

The relationship between traumatic brain injuries and resulting amino acid concentrations is not entirely understood, but if TBI does cause changes to these AA concentrations, it may benefit the individual to correct for those changes. 

  1. Biostatistics: 

The primary outcomes of interest in this study are amino acid levels and assessment of the composition and structure of  microbiome associated with amino acids present in individuals with chronic TBIs and health controls. There is no similar data in the literature concerning the chronic TBI population, however, previous literature has shown significantly lower concentrations of essential amino acids in participants with mild TBI than the concentrations observed in a healthy cohort; Valine concentrations in the healthy control averaged 79.0+/-24.8 mmol/L and valine concentration in the TBI group averaged 13.5+/-10.3 mmol/L. Assuming changes of amino acid concentrations will remain similar in a population with chronic TBIs, we can assume a power of at least 0.8 and an alpha of 0.05 with 10 participants in each study group.


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