Macromolecular-Suppressed GABA-Edited MR Spectroscopy in the Posterior Cingulate Cortex of Patients With Acute Mild Traumatic Brain Injury

Potential neuroprotective and autophagy-enhancing effects of alogliptin on lithium/pilocarpine-induced seizures in rats: Targeting the AMPK/SIRT1/Nrf2 axis

BACKGROUND

Status epilepticus (SE) as a severe neurodegenerative disease, greatly negatively affects people's health, and there is an urgent need for innovative treatments. The valuable neuroprotective effects of glucagon-like peptide-1 (GLP-1) in several neurodegenerative diseases have raised motivation to investigate the dipeptidyl peptidase-4 (DPP-4) inhibitor; alogliptin (ALO), an oral antidiabetic drug as a potential treatment for SE. ALO has shown promising neuroprotective effects in Alzheimer's and Parkinson's diseases, but its impact on SE has not yet been studied.

AIM

The present study aimed to explore the repurposing potential for ALO in a lithium/pilocarpine (Li/Pil)-induced SE model in rats.

MAIN METHODS

ALO (30 mg/kg/day) was administered via gavage for 14 days, and SE was subsequently induced in the rats using a single dose of Li/Pil (127/60 mg/kg), while levetiracetam was used as a standard antiepileptic drug.

KEY FINDINGS

The results showed that ALO reduced seizure severity and associated hippocampal neurodegeneration. ALO also increased γ-aminobutyric acid (GABA) levels, diminished glutamate spikes, and corrected glial fibrillary acidic protein (GFAP) changes. At the molecular level, ALO increased GLP-1 levels and activated its downstream signaling pathway, AMP-activated protein kinase (AMPK)/sirtuin-1 (SIRT1). ALO also dampened the brain's pro-oxidant response, curbed neuroinflammation, and counteracted hippocampal apoptosis affording neuroprotection. In addition, it activated autophagy as indicated by Beclin1 elevation.

SIGNIFICANCE

This study suggested that the neuroprotective properties and autophagy-enhancing effects of ALO make it a promising treatment for SE and can potentially be used as a management approach for this condition.

Mechanistic and therapeutic relationships of traumatic brain injury and γ-amino-butyric acid (GABA)

Traumatic brain injury (TBI) is a highly prevalent medical condition for which no medications specific for the prophylaxis or treatment of the condition as a whole exist. The spectrum of symptoms includes coma, headache, seizures, cognitive impairment, depression, and anxiety. Although it has been known for years that the inhibitory neurotransmitter γ-amino-butyric acid (GABA) is involved in TBI, no novel therapeutics based upon this mechanism have been introduced into clinical practice. We review the neuroanatomical, neurophysiological, neurochemical, and neuropharmacological relationships of GABA neurotransmission to TBI with a view toward new potential GABA-based medicines. The long-standing idea that excitatory and inhibitory (GABA and others) balances are disrupted by TBI is supported by the experimental data but has failed to invent novel methods of restoring this balance. The slow progress in advancing new treatments is due to the complexity of the disorder that encompasses multiple dynamically interacting biological processes including hemodynamic and metabolic systems, neurodegeneration and neurogenesis, major disruptions in neural networks and axons, frank brain lesions, and a multitude of symptoms that have differential neuronal and neurohormonal regulatory mechanisms. Although the current and ongoing clinical studies include GABAergic drugs, no novel GABA compounds are being explored. It is suggested that filling the gap in understanding the roles played by specific GABAA receptor configurations within specific neuronal circuits could help define new therapeutic approaches. Further research into the temporal and spatial delivery of GABA modulators should also be useful. Along with GABA modulation, research into the sequencing of GABA and non-GABA treatments will be needed.

Simultaneous Measurement of GABA, Glutathione, and Glutamate-Glutamine in the Thalamus using Edited MR Spectroscopy: Feasibility and Applications in Traumatic Brain Injury

BACKGROUND

MR spectroscopy (MRS) is a noninvasive tool for evaluating biochemical alterations, such as glutamate (Glu)/gamma-aminobutyric acid (GABA) imbalance and depletion of antioxidative glutathione (GSH) after traumatic brain injury (TBI). Thalamus, a critical and vulnerable region post-TBI, is challenging for MRS acquisitions, necessitating optimization to simultaneously measure GABA/Glu and GSH.

PURPOSE

To assess the feasibility and optimize acquisition and processing approaches for simultaneously measuring GABA, Glx (Glu + glutamine (Gln)), and GSH in the thalamus, employing Hadamard encoding and reconstruction of MEscher-GArwood (MEGA)-edited spectroscopy (HERMES).

STUDY TYPE

Prospective.

SUBJECTS

28 control subjects (age: 35.9 ± 15.1 years), and 17 mild TBI (mTBI) patients (age: 32.4 ± 11.3 years).

FIELD STRENGTH/SEQUENCE

3T/T1-weighted magnetization-prepared rapid gradient-echo (MP-RAGE), HERMES.

ASSESSMENT

We evaluated the impact of acquisition with spatial saturation bands and post-processing with spectral alignment on HERMES performance in the thalamus among controls. Within-subject variability was examined in five controls through repeated scans within a week. The HERMES spectra in the posterior cingulate cortex (PCC) of controls were used as a reference for assessing HERMES performance in a reliable target. Furthermore, we compared metabolite levels and fitting quality in the thalamus between mTBI patients and controls.

STATISTICAL TESTS

Unpaired t-tests and within-subject coefficient-of-variation (CV). A P-value <0.05 was deemed significant.

RESULTS

HERMES spectra, acquired with saturation bands and processed with spectral alignment, yielded reliable metabolite measurements in the thalamus. The mean within-subject CV for GABA, Glx, and GSH levels were 18%, 10%, and 16% in the thalamus (7%, 9%, and 16% in the PCC). GABA (3.20 ± 0.60 vs 2.51 ± 0.55, P < 0.01) and Glx (8.69 ± 1.23 vs 7.72 ± 1.19, P = 0.03) levels in the thalamus were significantly higher in mTBI patients than in controls, with GSH (1.27 ± 0.35 vs 1.22 ± 0.28, P = 0.65) levels showing no significant difference.

DATA CONCLUSION

Simultaneous measuring GABA/Glx and GSH using HERMES is feasible in the thalamus, providing valuable insight into TBI.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.