Non-invasive assessment of disease progression and neuroprotective effects of dietary coconut oil supplementation in the ALS SOD1G93A mouse model: A 1H-magnetic resonance spectroscopic study

Potential of neuroimaging as a biomarker in amyotrophic lateral sclerosis: from structure to metabolism

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by motor neuron degeneration. The development of ALS involves metabolite alterations leading to tissue lesions in the nervous system. Recent advances in neuroimaging have significantly improved our understanding of the underlying pathophysiology of ALS, with findings supporting the corticoefferent axonal disease progression theory. Current studies on neuroimaging in ALS have demonstrated inconsistencies, which may be due to small sample sizes, insufficient statistical power, overinterpretation of findings, and the inherent heterogeneity of ALS. Deriving meaningful conclusions solely from individual imaging metrics in ALS studies remains challenging, and integrating multimodal imaging techniques shows promise for detecting valuable ALS biomarkers. In addition to giving an overview of the principles and techniques of different neuroimaging modalities, this review describes the potential of neuroimaging biomarkers in the diagnosis and prognostication of ALS. We provide an insight into the underlying pathology, highlighting the need for standardized protocols and multicenter collaborations to advance ALS research.

Pleiotropic effects of trisomy and pharmacologic modulation on structural, functional, molecular, and genetic systems in a Down syndrome mouse model

Down syndrome (DS) is characterized by skeletal and brain structural malformations, cognitive impairment, altered hippocampal metabolite concentration and gene expression imbalance. These alterations were usually investigated separately, and the potential rescuing effects of green tea extracts enriched in epigallocatechin-3-gallate (GTE-EGCG) provided disparate results due to different experimental conditions. We overcame these limitations by conducting the first longitudinal controlled experiment evaluating genotype and GTE-EGCG prenatal chronic treatment effects before and after treatment discontinuation. Our findings revealed that the Ts65Dn mouse model reflected the pleiotropic nature of DS, exhibiting brachycephalic skull, ventriculomegaly, neurodevelopmental delay, hyperactivity, and impaired memory robustness with altered hippocampal metabolite concentration and gene expression. GTE-EGCG treatment modulated most systems simultaneously but did not rescue DS phenotypes. On the contrary, the treatment exacerbated trisomic phenotypes including body weight, tibia microarchitecture, neurodevelopment, adult cognition, and metabolite concentration, not supporting the therapeutic use of GTE-EGCG as a prenatal chronic treatment. Our results highlight the importance of longitudinal experiments assessing the co-modulation of multiple systems throughout development when characterizing preclinical models in complex disorders and evaluating the pleiotropic effects and general safety of pharmacological treatments.

Effect of the Mediterranean diet supplemented with nicotinamide riboside and pterostilbene and/or coconut oil on anthropometric variables in amyotrophic lateral sclerosis. A pilot study

Amyotrophic Lateral Sclerosis (ALS) is a chronic and progressive neurodegenerative disease that causes the death of motor neurons and alters patients' body composition. Supplementation with the antioxidants nicotinamide riboside (NR) and pterostilbene (PTER) can combat associated oxidative stress. Additionally, coconut oil is an alternative energy substrate that can address mitochondrial dysfunction. The aim of the present study is to assess the impact of a Mediterranean Diet supplemented with NR and PTER and/or with coconut oil on the anthropometric variables of patients with ALS. A prospective, mixed, randomized, analytical and experimental pilot study in humans was performed through a clinical trial (registered with ClinicalTrials.gov under number NCT03489200) with pre- and post-intervention assessments. The sample was made up of 40 subjects categorized into four study groups (Control, Antioxidants, Coconut oil, and Antioxidants + Coconut oil). Pre- and post-intervention anthropometric assessments were carried out to determine the following data: weight, percentage of fat and muscle mass, skinfolds, body perimeters, Body Mass Index (BMI), Waste-to-Hip Index (WHI) and Waist-Height Ratio (WHR). Compared to the Control group, GAx significantly increased muscle mass percentage and decreased fat mass percentage, triceps, iliac crest, and abdominal skinfolds. GCoco significantly increased muscle mass percentage and decreased fat mass percentage, subscapular skinfolds, and abdominal skinfolds. GAx + coco significantly increased muscle mass percentage and decreased abdominal skinfolds. Therefore, our results suggest that the Mediterranean Diet supplemented with NR and PTER and the Mediterranean Diet supplemented with coconut oil (ketogenic diet) are the two nutritional interventions that have reported the greatest benefits, at anthropometric level.

Metabolomics as a Crucial Tool to Develop New Therapeutic Strategies for Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer’s (AD), Parkinson’s (PD), and amyotrophic lateral sclerosis (ALS), share common pathological mechanisms, including metabolism alterations. However, their specific neuronal cell types affected and molecular biomarkers suggest that there are both common and specific alterations regarding metabolite levels. In this review, we were interested in identifying metabolite alterations that have been reported in preclinical models of NDs and that have also been documented as altered in NDs patients. Such alterations could represent interesting targets for the development of targeted therapy. Importantly, the translation of such findings from preclinical to clinical studies is primordial for the study of possible therapeutic agents. We found that N-acetyl-aspartate (NAA), myo-inositol, and glutamate are commonly altered in the three NDs investigated here. We also found other metabolites commonly altered in both AD and PD. In this review, we discuss the studies reporting such alterations and the possible pathological mechanism underlying them. Finally, we discuss clinical trials that have attempted to develop treatments targeting such alterations. We conclude that the treatment combination of both common and differential alterations would increase the chances of patients having access to efficient treatments for each ND.

Enhanced Cortical Metabolic Activity in Females and Males of a Slow Progressing Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with selective degeneration of motor neurons in the central nervous system. The pathophysiology of ALS is not well understood. We have used ¹H-[¹³C]-NMR spectroscopy together with an administration of [1,6-¹³C₂]glucose and [2-¹³C]acetate in female and male SOD1^G37R mice to assess neuronal and astroglial metabolic activity, respectively, in the central nervous system in ALS condition. The female (p = 0.0008) and male (p < 0.0001) SOD1^G37R mice exhibited decreased forelimb strength when compared with wild-type mice. There was a reduction in N-acetylaspartylglutamate level, and elevation in myo-inositol in the spinal cord of female and male SOD1^G37R mice. The transgenic male mice exhibited increased acetate oxidation in the spinal cord (p = 0.05) and cerebral cortex (p = 0.03), while females showed an increase in the spinal cord (p = 0.02) only. As acetate is transported and preferentially metabolized in the astrocytes, the finding of increased rate of acetate oxidation in the transgenic mice is suggestive of astrocytic involvement in the pathogenesis of ALS. The rates of glucose oxidation in glutamatergic (p = 0.0004) and GABAergic neurons (p = 0.0052) were increased in the cerebral cortex of male SOD1^G37R mice when compared with the controls. The female mice showed an increase in glutamatergic (p = 0.039) neurometabolic activity only. The neurometabolic activity was unperturbed in the spinal cord of either sex. These data suggest differential changes in neurometabolic activity across the central nervous system in SOD1^G37R mice.

Imaging immunological processes from blood to brain in amyotrophic lateral sclerosis

Neuropathology studies of amyotrophic lateral sclerosis (ALS) and animal models of ALS reveal a strong association between aberrant protein accumulation and motor neurone damage, as well as activated microglia and astrocytes. While the role of neuroinflammation in the pathology of ALS is unclear, imaging studies of the central nervous system (CNS) support the idea that innate immune activation occurs early in disease in both humans and rodent models of ALS. In addition, emerging studies also reveal changes in monocytes, macrophages and lymphocytes in peripheral blood as well as at the neuromuscular junction. To more clearly understand the association of neuroinflammation (innate and adaptive) with disease progression, the use of biomarkers and imaging modalities allow monitoring of immune parameters in the disease process. Such approaches are important for patient stratification, selection and inclusion in clinical trials, as well as to provide readouts of response to therapy. Here, we discuss the different imaging modalities, e.g. magnetic resonance imaging, magnetic resonance spectroscopy and positron emission tomography as well as other approaches, including biomarkers of inflammation in ALS, that aid the understanding of the underlying immune mechanisms associated with motor neurone degeneration in ALS.

Neurometabolic Correlates of Reactive and Proactive Motor Inhibition in Young and Older Adults: Evidence from Multiple Regional 1H-MR Spectroscopy

Suboptimal inhibitory control is a major factor contributing to motor/cognitive deficits in older age and pathology. Here, we provide novel insights into the neurochemical biomarkers of inhibitory control in healthy young and older adults and highlight putative neurometabolic correlates of deficient inhibitory functions in normal aging. Age-related alterations in levels of glutamate–glutamine complex (Glx), N-acetylaspartate (NAA), choline (Cho), and myo-inositol (mIns) were assessed in the right inferior frontal gyrus (RIFG), pre-supplementary motor area (preSMA), bilateral sensorimotor cortex (SM1), bilateral striatum (STR), and occipital cortex (OCC) with proton magnetic resonance spectroscopy (¹H-MRS). Data were collected from 30 young (age range 18–34 years) and 29 older (age range 60–74 years) adults. Associations between age-related changes in the levels of these metabolites and performance measures or reactive/proactive inhibition were examined for each age group. Glx levels in the right striatum and preSMA were associated with more efficient proactive inhibition in young adults but were not predictive for reactive inhibition performance. Higher NAA/mIns ratios in the preSMA and RIFG and lower mIns levels in the OCC were associated with better deployment of proactive and reactive inhibition in older adults. Overall, these findings suggest that altered regional concentrations of NAA and mIns constitute potential biomarkers of suboptimal inhibitory control in aging.

Non-invasive characterization of amyotrophic lateral sclerosis in a hTDP-43A315T mouse model: A PET-MR study

Currently TAR DNA binding protein 43 (TDP-43) pathology, underlying Amyotrophic Lateral Sclerosis (ALS), remains poorly understood which hinders both clinical diagnosis and drug discovery efforts. To better comprehend the disease pathophysiology, positron emission tomography (PET) and multi-parametric magnetic resonance imaging (mp-MRI) provide a non-invasive mode to investigate molecular, structural, and neurochemical abnormalities in vivo. For the first time, we report the findings of a longitudinal PET-MR study in the TDP-43^A315T ALS mouse model, investigating disease-related changes in the mouse brain. 2-deoxy-2-[¹⁸F]fluoro-D-glucose [¹⁸F]FDG PET showed significantly lowered glucose metabolism in the motor and somatosensory cortices of TDP-43^A315T mice whereas metabolism was elevated in the region covering the bilateral substantia nigra, reticular and amygdaloid nucleus between 3 and 7 months of age, as compared to non-transgenic controls. MR spectroscopy data showed significant changes in glutamate + glutamine (Glx) and choline levels in the motor cortex and hindbrain of TDP-43^A315T mice compared to controls. Cerebral blood flow (CBF) measurements, using an arterial spin labelling approach, showed no significant age- or group-dependent changes in brain perfusion. Diffusion MRI indices demonstrated transient changes in different motor areas of the brain in TDP-43^A315T mice around 14 months of age. Cytoplasmic TDP-43 proteinaceous inclusions were observed in the brains of symptomatic, 18-month-old mice, but not in non-symptomatic transgenic or wild-type mice. Our results reveal that disease- and age-related functional and neurochemical alterations, together with limited structural changes, occur in specific brain regions of transgenic TDP-43^A315T mice, as compared to their healthy counterparts. Altogether these findings shed new light on TDP-43^A315T disease pathogenesis and may prove useful for clinical management of ALS.

Sensorimotor cortex neurometabolite levels as correlate of motor performance in normal aging: evidence from a 1H-MRS study

Aging is associated with gradual alterations in the neurochemical characteristics of the brain, which can be assessed in-vivo with proton-magnetic resonance spectroscopy (¹H-MRS). However, the impact of these age-related neurochemical changes on functional motor behavior is still poorly understood. Here, we address this knowledge gap and specifically focus on the neurochemical integrity of the left sensorimotor cortex (SM1) and the occipital lobe (OCC), as both regions are main nodes of the visuomotor network underlying bimanual control. ¹H-MRS data and performance on a set of bimanual tasks were collected from a lifespan (20-75 years) sample of 86 healthy adults. Results indicated that aging was accompanied by decreased levels of N-acetylaspartate (NAA), glutamate-glutamine (Glx), creatine ​+ ​phosphocreatine (Cr) and myo-inositol (mI) in both regions, and decreased Choline (Cho) in the OCC region. Lower NAA and Glx levels in the SM1 and lower NAA levels in the OCC were related to poorer performance on a visuomotor bimanual coordination task, suggesting that NAA could serve as a potential biomarker for the integrity of the motor system supporting bimanual control. In addition, lower NAA, Glx, and mI levels in the SM1 were found to be correlates of poorer dexterous performance on a bimanual dexterity task. These findings highlight the role for ¹H-MRS to study neurochemical correlates of motor performance across the adult lifespan.

Motor cortex metabolite alterations in amyotrophic lateral sclerosis assessed in vivo using edited and non-edited magnetic resonance spectroscopy

Previous MRI and proton spectroscopy (¹H-MRS) studies have revealed impaired neuronal integrity and altered neurometabolite concentrations in the motor cortex of patients with amyotrophic lateral sclerosis (ALS). Here, we aim to use MRI with conventional and novel MRS sequences to further investigate neurometabolic changes in the motor cortex of ALS patients and their relation to clinical parameters. We utilized the novel HERMES (Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy) MRS sequence to simultaneously quantify the inhibitory neurotransmitter GABA and antioxidant glutathione in ALS patients (n = 7) and healthy controls (n = 7). In addition, we have also quantified other MRS observable neurometabolites using a conventional point-resolved MR spectroscopy (PRESS) sequence in ALS patients (n = 20) and healthy controls (n = 20). We observed a trend towards decreasing glutathione concentrations in the motor cortex of ALS patients (p = 0.0842). In addition, we detected a 11% decrease in N-acetylaspartate (NAA) (p = 0.025), a 15% increase in glutamate + glutamine (Glx) (p = 0.0084) and a 21% increase in myo-inositol (mIns) (p = 0.0051) concentrations for ALS patients compared to healthy controls. Furthermore, significant positive correlations were found between GABA-NAA (p = 0.0480; Rρ = 0.7875) and NAA-mIns (p = 0.0448; Rρ = -0.4651) levels among the patients. NAA levels in the bulbar-onset patient group were found to be significantly (p = 0.0097) lower compared to the limb-onset group. A strong correlation (p < 0.0001; Rρ = -0,8801) for mIns and a weak correlation (p = 0.0066; Rρ = -0,6673) for Glx was found for the disease progression, measured by declining of the ALS Functional Rating Scale-Revised criteria (ALSFRS-R). Concentrations of mIns and Glx also correlated with disease severity measured by forced vital capacity (FVC). Results suggest that mean neurometabolite concentrations detected in the motor cortex may indicate clinical and pathological changes in ALS.