Low plasma GABA is a trait-like marker for bipolar illness

Area of Science:

• Neuroscience
• Psychiatry
• Biochemistry

Background:

• Plasma gamma-aminobutyric acid (pGABA) serves as an indicator of central nervous system GABA activity.
• Previous studies linked low pGABA levels to unipolar depression symptoms in about 40% of patients.
• GABA is a key inhibitory neurotransmitter implicated in mood regulation.

Purpose of the Study:

• To investigate plasma gamma-aminobutyric acid (pGABA) levels in patients diagnosed with bipolar disorder.
• To determine if low pGABA is specific to the depressed phase or also present in the manic phase of bipolar disorder.
• To explore low pGABA as a potential shared biological marker between unipolar and bipolar mood disorders.

Main Methods:

• Blood samples were collected from symptomatic bipolar disorder patients upon hospital or clinic admission.
• Plasma gamma-aminobutyric acid (pGABA) levels were quantified.
• pGABA levels were compared between bipolar patients (manic and depressed phases) and healthy control subjects.

Main Results:

• Bipolar disorder patients, in both manic and depressed phases, exhibited significantly lower mean pGABA levels compared to healthy controls.
• Approximately 30% to 40% of bipolar patients presented with pGABA levels below the normal control range.
• The distribution pattern of pGABA levels in bipolar patients mirrored that observed in symptomatic unipolar depression.

Conclusions:

• Low plasma gamma-aminobutyric acid (pGABA) is not exclusive to the depressed state and is also observed in the manic phase of bipolar disorder.
• These findings suggest that reduced pGABA levels may represent a common biological correlate underlying both unipolar and bipolar mood disorders.
• pGABA warrants further investigation as a potential biomarker for mood disorders.