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CME / ABIM MOC / CE

What Do Cerebrospinal Fluid Biomarkers in Unipolar Depression Tell Us?

  • Authors: News Author: Megan Brooks; CME Author: Laurie Barclay, MD
  • CME / ABIM MOC / CE Released: 6/10/2022
  • THIS ACTIVITY HAS EXPIRED FOR CREDIT
  • Valid for credit through: 6/10/2023, 11:59 PM EST
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Target Audience and Goal Statement

This activity is intended for psychiatrists, family medicine and primary care clinicians, internists, neurologists, nurses, nurse practitioners, pharmacists, physician assistants, and other members of the health care team for patients with unipolar depression.

The goal of this activity is for learners to be better able to describe differences in quantified cerebrospinal fluid biomarkers in patients with unipolar depression compared with healthy control individuals, based on a systematic review and meta-analysis.

Upon completion of this activity, participants will:

  • Assess differences in quantified cerebrospinal fluid biomarkers in patients with unipolar depression compared with healthy control individuals, based on a systematic review and meta-analysis
  • Evaluate the clinical implications of differences in quantified cerebrospinal fluid biomarkers in patients with unipolar depression compared with healthy control individuals, based on a systematic review and meta-analysis
  • Outline implications for the healthcare team


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News Author

  • Megan Brooks

    Freelance writer, Medscape

    Disclosures

    Megan Brooks has no relevant financial relationships.

CME Author

  • Laurie Barclay, MD

    Freelance writer and reviewer
    Medscape, LLC

    Disclosures

    Laurie Barclay, MD, has the following relevant financial relationships:
    Stocks, stock options, or bonds: AbbVie (former)

Editor/Nurse Planner

  • Lisa Simani, APRN, MS, ACNP

    Associate Director, Accreditation and Compliance
    Medscape, LLC

    Disclosures

    Lisa Simani, APRN, MS, ACNP, has no relevant financial relationships.

Compliance Reviewer

  • Amanda Jett, PharmD, BCACP

    Associate Director, Accreditation and Compliance
    Medscape, LLC

    Disclosures

    Amanda Jett, PharmD, BCACP, has no relevant financial relationships.

Peer Reviewer

This activity has been peer reviewed and the reviewer has no relevant financial relationships.


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CME / ABIM MOC / CE

What Do Cerebrospinal Fluid Biomarkers in Unipolar Depression Tell Us?

Authors: News Author: Megan Brooks; CME Author: Laurie Barclay, MDFaculty and Disclosures
THIS ACTIVITY HAS EXPIRED FOR CREDIT

CME / ABIM MOC / CE Released: 6/10/2022

Valid for credit through: 6/10/2023, 11:59 PM EST

processing....

Clinical Context

Depression is the third leading global cause of years lived with disability. Despite multiple hypotheses, depression pathophysiology is incompletely understood. Identification of potential subgroups of depression with different biomarkers might help explain the diverse symptomatology and variability in treatment response observed in patients with depression. Multiple biomarkers of depression involved in several brain circuits are altered in patients with unipolar depression.

Study Synopsis and Perspective

The first comprehensive meta-analysis of all biomarkers quantified to date in cerebrospinal fluid (CSF) of individuals with unipolar depression showed that several could be "clinically meaningful" because they suggest neuroimmunological alterations, disturbances in the blood-brain barrier, hyperactivity in the hypothalamic-pituitary-adrenal (HPA) axis, and impaired neuroplasticity as factors in depression pathophysiology.

However, said study investigator Michael E. Benros, MD, PhD, professor and head of research at Mental Health Centre Copenhagen and University of Copenhagen, Denmark, this is on a group level. "So in order to be relevant in a clinical context, the results need to be validated by further high-quality studies identifying subgroups with different biological underpinnings," he told Medscape Medical News.

The study was published online April 20 in JAMA Psychiatry.

Multiple Pathways to Depression

The systematic review and meta-analysis included 97 studies investigating 165 CSF biomarkers. 

Of the 42 biomarkers investigated in at least 2 studies, patients with unipolar depression had higher CSF levels of interleukin 6, a marker of chronic inflammation; total protein, which signals blood-brain barrier dysfunction and increased permeability; and cortisol, which is linked to psychological stress, compared with healthy controls.

Depression was also associated with:

  • lower CSF levels of homovanillic acid, the major terminal metabolite of dopamine
  • gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the CNS thought to play a vital role in the control of stress and depression
  • somatostatin, a neuropeptide often coexpressed with GABA
  • brain-derived neurotrophic factor (BDNF), a protein involved in neurogenesis, synaptic plasticity, and neurotransmission
  • amyloid-β 40, implicated in Alzheimer disease
  • transthyretin, involved in transport of thyroxine across the blood-brain barrier

Collectively, the findings point toward a "dysregulated dopaminergic system, a compromised inhibitory system, [HPA] axis hyperactivity, increased neuroinflammation and blood-brain barrier permeability, and impaired neuroplasticity as important factors in depression pathophysiology," the investigators write.

"It is notable that we did not find significant difference in the metabolite levels of serotonin and noradrenalin, which are the most targeted neurotransmitters in modern antidepressant treatment," said Dr Benros. However, this could be explained by substantial heterogeneity between studies and the fact that quantification of total CSF biomarker concentrations does not reflect local alteration within the brain, he explained.

Many of the studies had small cohorts, and most quantified only a few biomarkers, making it hard to examine potential interactions between biomarkers or identify specific phenotypes of depression.

"[N]ovel high-quality studies including larger cohorts with an integrative approach and extensive numbers of biomarkers are needed to validate these potential biomarkers of depression and set the stage for the development of more effective and precise treatments," the researchers note. 

Which Ones Hold Water?

Reached for comment, Dean MacKinnon, MD, associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, Baltimore, Maryland, noted that this analysis "extracts the vast amount of knowledge" gained from different studies on biomarkers in the CSF for depression.

"They were able to identify 97 papers that have enough information in them that they could sort of lump them together and see which ones still hold water. It's always useful to be able to look at patterns in the research and see if you can find some consistent trends," he told Medscape Medical News.

Dr MacKinnon, who was not part of the research team, also noted that "nonreplicability" is a problem in psychiatry and psychology research, "so being able to show that at least some studies were sufficiently well done, to get a good result, and that they could be replicated in at least one other good study is useful information."

When it comes to depression, Dr MacKinnon said, "We just don't know enough to really pin down a physiologic pathway to explain it. The fact that some people seem to have high cortisol and some people seem to have high permeability of blood-brain barrier, and others have abnormalities in dopamine, is interesting and suggests that depression is likely not a unitary disease with a single cause."

He cautioned, however, that the findings do not have immediate clinical implications for individual patients with depression. 

"Theoretically, down the road, if you extrapolate from what they found, and if it's truly the case that this research maps to something that could suggest a different clinical approach, you might be able to determine whether one patient might respond better to [a selective serotonin reuptake inhibitor or serotonin and norepinephrine reuptake inhibitor] or something like that," Dr MacKinnon said.

The study was funded by unrestricted grants from the Lundbeck Foundation. Dr Benros reported grants from Lundbeck Foundation during the conduct of the study. Dr MacKinnon has disclosed no relevant financial relationships.

JAMA Psychiatry. Published online April 20, 2022.[1]

Study Highlights

  • The meta-analysis included 97 studies with available data.
  • Of 165 biomarkers studied, 42 were quantified in at least 2 studies.
  • Compared with healthy controls, patients with unipolar depression had higher CSF levels of interleukin 6 (7 studies; standardized mean difference [SMD], 0.35; 95% confidence interval [CI], 0.12-0.59; I 2=16%), total protein (5 studies; SMD, 0.53; 95% CI, 0.35-0.72; I 2=0%), and cortisol (2 studies; SMD, 1.23; 95% CI, 0.89-1.57; I 2=0%).
  • Interleukin 6 is a marker of chronic inflammation; total protein reflects blood-brain barrier dysfunction and increased permeability, and cortisol is linked to psychological stress.
  • Patients with depression had lower CSF levels of homovanillic acid (17 studies; SMD, −0.26; 95% CI, −0.39 to −0.14; I 2=11%), GABA (4 studies; SMD, −0.50; 95% CI, −0.92 to −0.08; I 2=55%), somatostatin (5 studies; SMD, −1.49; 95% CI, −2.53 to −0.45; I 2=91%), BDNF (3 studies; SMD, −0.58; 95% CI, −0.97 to −0.19; I 2=0%), amyloid-β 40 (3 studies; SMD, −0.80; 95% CI, −1.14 to −0.46; I 2=0%), and transthyretin (2 studies; SMD, −0.82; 95% CI, −1.37 to −0.27; I 2=0%).
  • Homovanillic acid is the major terminal metabolite of dopamine; GABA is the major CNS inhibitory neurotransmitter implicated in control of stress and depression; somatostatin is a neuropeptide often coexpressed with GABA; BDNF is a protein involved in neurogenesis, synaptic plasticity, and neurotransmission and increases in the blood in response to antidepressant treatment; amyloid-β 40 is implicated in Alzheimer disease; and transthyretin facilitates thyroxine transport across the blood-brain barrier and may be neuroprotective.
  • The investigators concluded that numerous CSF biomarkers were altered in individuals with unipolar depression, indicating multifactorial pathogenesis involving several neurocircuits.
  • CSF biomarker changes suggest that a dysregulated dopaminergic system, compromised inhibitory system, HPA-axis hyperactivity, increased neuroinflammation and blood-brain barrier permeability, and impaired neuroplasticity are important in depression pathophysiology.
  • Study limitations include a limited number of eligible studies for most of the identified biomarkers, small sample sizes, and substantial heterogeneity among studies.
  • Novel high-quality studies including larger cohorts, an integrative approach, and extensive numbers of biomarkers are needed to validate these potential biomarkers of depression and target development of more effective and precise treatments.
  • Identifying potential subgroups of depression with different biomarkers might help explain diverse symptomatology and variability in treatment response.
  • Failure to find differences in metabolite levels of serotonin and noradrenalin, which are the most targeted neurotransmitters in modern antidepressant treatment, may be explained by heterogeneity between studies, the fact that quantifying total CSF biomarker concentrations does not reflect local alteration within the brain, and/or the existence of subgroups in depression.
  • The findings are not yet applicable for management of individual patients with depression, but if validated, CSF biomarkers theoretically might be able to determine whether a patient might respond better to a particular drug such as a selective serotonin reuptake inhibitor or serotonin and norepinephrine reuptake inhibitor.

Clinical Implications

  • Numerous CSF biomarkers were altered in individuals with unipolar depression.
  • The alterations suggest multifactorial pathogenesis involving several neurocircuits.
  • Implications for the Health Care Team: If validated, these potential biomarkers of depression could facilitate development of more effective and precise treatments.

 

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