Targeted metabolomic analysis in Parkinson's disease brain frontal cortex and putamen with relation to cognitive impairment

Pharmacological recapitulation of the lean phenotype induced by the lifespan-extending sulfur amino acid-restricted diet

Sulfur amino acid restriction (SAAR), lowering the dietary concentration of sulfur amino acids methionine and cysteine, induces strong anti-obesity effects in rodents. Due to difficulties in formulating the SAAR diet for human consumption, its translation is challenging. Since our previous studies suggest a mechanistic role for low glutathione (GSH) in SAAR-induced anti-obesity effects, we investigated if the pharmacological lowering of GSH recapitulates the lean phenotype in mice on a sulfur amino acid-replete diet. Male obese C57BL6/NTac mice were fed high-fat diets with 0.86% methionine (CD), 0.12% methionine (SAAR), SAAR diet supplemented with a GSH biosynthetic precursor, N-acetylcysteine in water (NAC), and CD supplemented with a GSH biosynthetic inhibitor, DL-buthionine-(S, R)-sulfoximine in water (BSO). The SAAR diet lowered hepatic GSH but increased Nrf2, Phgdh, and serine. These molecular changes culminated in lower hepatic lipid droplet frequency, epididymal fat depot weights, and body fat mass; NAC reversed all these changes. BSO mice exhibited all SAAR-induced changes, with two notable differences, i.e., a smaller effect size than that of the SAAR diet and a higher predilection for molecular changes in kidneys than in the liver. Metabolomics data indicate that BSO and the SAAR diet induce similar changes in the kidney. Unaltered plasma aspartate and alanine transaminases and cystatin-C indicate that long-term continuous administration of BSO is safe. Data demonstrate that BSO recapitulates the SAAR-induced anti-obesity effects and that GSH plays a mechanistic role. BSO dose-response studies in animals and pilot studies in humans to combat obesity are highly warranted.

A Multi-omics Framework Based on Machine Learning as a Predictor of Cognitive Impairment Progression in Early Parkinson's Disease

INTRODUCTION

Cognitive impairment (CI) is a common non-motor symptom of Parkinson's disease (PD). However, the diagnosis and prediction of CI progression in PD remain challenging. We aimed to explore a multi-omics framework based on machine learning integrating comprehensive radiomics, cerebrospinal fluid biomarkers, and genetics information to identify CI progression in early PD.

METHODS

Patients were first diagnosed with PD without CI at baseline. According to whether CI progressed within 5 years, patients were divided into two groups: PD without CI and PD with CI. Radiomics signatures were extracted from patients' T1-weighted MRI. We used machine learning methods to construct radiomics, hybrid, and multi-omics models in the training set and validated the models in the testing set.

RESULT

In the two groups, we found 7, 23, and 25 radiomics signatures with significant differences in the parietal, temporal, and frontal lobes, respectively. The radiomics model using the 25 signatures of the frontal lobe had an accuracy of 0.833 and an AUC (area under the curve) of 0.879 to predict CI progression. In addition, the hybrid model fused with the cerebrospinal fluid Aβ level had an accuracy of 0.867 and an AUC of 0.916. In our study, the multi-omics model showed the best predictive performance. The accuracy of the multi-omics model was 0.900, and the average AUC value after five-fold cross-validation was 0.928.

CONCLUSION

Radiomics signatures have a recognition effect in the CI progression in early PD. Multi-omics frameworks combining radiomics, cerebrospinal fluid biomarkers, and genetic information may be a potential predictor of CI progression in PD.

Metabolomics in Parkinson's Disease and Correlation with Disease State

Changes in the level of metabolites, small molecules that are intermediates produced by metabolism or catabolism, are associated with developing diseases. Metabolite signatures in body fluids such as plasma, cerebrospinal fluid, urine, and saliva are associated with Parkinson's disease. Here, we discuss alteration of metabolites in the TCA cycle, pentose phosphate pathway, kynurenic network, and redox system. We also summarize the efforts of many research groups to differentiate between metabolite profiles that characterize PD motor progression and dyskinesia, gait and balance, and non-motor symptoms such as depression and cognitive decline. Understanding how changes in metabolites lead to progression in PD may allow for the identification of individuals at the earliest stage of the disease and the development of new therapeutic strategies.

The associations between prenatal plastic phthalate exposure and lipid acylcarnitine levels in humans and mice

Phthalates are ubiquitous environmental pollutants known for their endocrine-disrupting properties, particularly during critical periods such as pregnancy and early childhood. Phthalates alter lipid metabolism, but the role of prenatal exposure on the offspring lipidome is less understood. In particular, we focused on long chain acylcarnitines - intermediates of fatty acid oxidation that serve as potential biomarkers of mitochondrial function and energy metabolism. This study aimed (i) to investigate the association between prenatal phthalate exposure and the child's blood acylcarnitine concentrations and, (ii) to evaluate the impact of prenatal administration of di-(2-ethylhexyl) phthalate (DEHP) on acylcarnitine levels in mouse offspring blood, brain and liver. We conducted analyses of both a prospective birth cohort study and an experimental study in mice. From the Barwon Infant Study cohort (1074 mother-child pairs), prenatal phthalate exposure was assessed at 36 weeks' gestation and its association with acylcarnitine levels was examined in cord blood, and child's blood at 6 months, 12 months and 4 years. In mice, pregnant C57BL/6 J mouse dams were exposed to 20 μg/kg DEHP for 5 days mid-gestation, and offspring tissues were analyzed at 1 month of age postnatally for acylcarnitine profiles. Our findings demonstrate that prenatal phthalate levels (specifically butyl benzyl phthalate (BBzP) and diisobutyl phthalate (DiBP)) are inversely associated with total long chain acylcarnitine levels in human cord blood at birth. In contrast, BBzP was positively associated with the long chain acylcarnitines at 12 months of age. In mice, prenatal DEHP exposure for only 5 days led to decreased palmitoylcarnitine (AC16:0) levels in the brain and liver, but not in blood. Taken together, our findings highlight that prenatal phthalate exposure can alter acylcarnitine profiles, indicating disruptions in fatty acid metabolism that may have long-term effects on metabolic health.

Dysregulation of mitochondrial α-ketoglutarate dehydrogenase leads to elevated lipid peroxidation in CHCHD2-linked Parkinson's disease models

Dysregulation of mitochondrial function has been implicated in Parkinson's disease (PD), but the role of mitochondrial metabolism in disease pathogenesis remains to be elucidated. Using an unbiased metabolomic analysis of purified mitochondria, we identified alterations in α-ketoglutarate dehydrogenase (KGDH) pathway upon loss of PD-linked CHCHD2 protein. KGDH, a rate-limiting enzyme complex in the tricarboxylic acid cycle, was decreased in CHCHD2-deficient male mouse brains and human dopaminergic neurons. This deficiency of KGDH led to elevated α-ketoglutarate and increased lipid peroxidation. Treatment of CHCHD2-deficient dopaminergic neurons with lipoic acid, a KGDH cofactor and antioxidant agent, resulted in decreased levels of lipid peroxidation and phosphorylated α-synuclein. CHCHD10, a close homolog of CHCHD2 that is primarily linked to amyotrophic lateral sclerosis/frontotemporal dementia, did not affect the KGDH pathway or lipid peroxidation. Together, these results identify KGDH metabolic pathway as a targetable mitochondrial mechanism for correction of increased lipid peroxidation and α-synuclein in Parkinson's disease.

Association of plasma homocysteine with cognitive impairment in patients with Parkinson's disease

Background

Elevated plasma homocysteine (Hcy) has been reported as a risk factor for cognitive impairment in the general population. However, there are conflicting results regarding the relationship between Hcy and cognitive impairment across various cognitive domains in Parkinson's disease (PD).

Objective

This study aims to explore the association between plasma Hcy levels, cognitive impairment, and dysfunction in various cognitive domains among PD patients with and without mild cognitive impairment (MCI).

Methods

A total of 101 PD patients underwent plasma Hcy measurement, comprising 50 PD-MCI patients and 51 patients with normal cognition (PD-NC). A battery of neuropsychological tests was administered to assess different cognitive domains. Adjusted generalized linear models were used to assess the correlations between Hcy levels and cognitive functions.

Results

As anticipated, PD-MCI patients demonstrated a significant decline in cognitive function across all five cognitive domains (memory, executive function, attention/working memory, language, and visuospatial function). Elevated plasma Hcy levels (≥ 10 μmol/L) were associated with a higher odds of PD-MCI, even within the normal range of Hcy levels (< 15 μmol/L). After adjusting for confounding factors, a negative correlation was observed between plasma Hcy levels and the performance on specific cognitive tests evaluating executive functions in PD, such as the Stroop Color-Word Test-C (β = -1.123, 95% CI = -1.845 ∼-0.401, p = 0.0023).

Conclusion

This study underscores a significant link between plasma Hcy levels and PD-MCI, particularly concerning executive dysfunction, even within the normal range of Hcy levels (< 15 μmol/L).

Comprehensive Targeted and Quantitative Profiling of the Human Milk Metabolome: Impact of Delivery Mode, Breastfeeding Practices, and Maternal Diet

SCOPE

Human milk (HM) is rich in bioactive compounds and essential nutrients. While research has focused on lipids, minerals, immune markers, microbiota, and oligosaccharides, specific metabolites are less studied. This study uses targeted metabolomics to identify and quantify metabolites in HM and explores the impact of perinatal and dietary factors on the metabolomic profile.

METHODS AND RESULTS

In a cross-sectional study of 123 healthy lactating women, HM samples were collected up to 1 month postpartum and analyzed using the Biocrates MxP Quant 500 kit. Maternal and neonatal clinical, anthropometric, and nutritional data were collected. A total of 432 metabolites were quantified and categorized into 20 groups. The metabolomic profiles formed three distinct clusters, primarily driven by triglyceride concentration differences. Docosahexaenoic acid (DHA) levels were higher in HM from mothers with vaginal delivery compared to C-section births and differences in hexoses were found between exclusive and mixed-feeding practices. Maternal diets rich in lipids and animal proteins were associated with elevated amino acids, sphingolipids, and glycosyl-ceramides.

CONCLUSION

The HM metabolome was grouped into three clusters influenced by delivery mode, lactation practices, and maternal diet. This comprehensive analysis opens new avenues to explore HM composition and offers valuable insights for future dietary interventions aimed at modulating HM.

Oligodendrocytes, the Forgotten Target of Gene Therapy

If the billions of oligodendrocytes (OLs) populating the central nervous system (CNS) of patients could express their feelings, they would undoubtedly tell gene therapists about their frustration with the other neural cell populations, neurons, microglia, or astrocytes, which have been the favorite targets of gene transfer experiments. This review questions why OLs have been left out of most gene therapy attempts. The first explanation is that the pathogenic role of OLs is still discussed in most CNS diseases. Another reason is that the so-called ubiquitous CAG, CBA, CBh, or CMV promoters-widely used in gene therapy studies-are unable or poorly able to activate the transcription of episomal transgene copies brought by adeno-associated virus (AAV) vectors in OLs. Accordingly, transgene expression in OLs has either not been found or not been evaluated in most gene therapy studies in rodents or non-human primates. The aims of the current review are to give OLs their rightful place among the neural cells that future gene therapy could target and to encourage researchers to test the effect of OL transduction in various CNS diseases.

α-synuclein overexpression and the microbiome shape the gut and brain metabolome in mice

Pathological forms of α-synuclein contribute to synucleinopathies, including Parkinson's disease (PD). Most cases of PD arise from gene-environment interactions. Microbiome composition is altered in PD, and gut bacteria are causal to symptoms in animal models. We quantitatively profiled nearly 630 metabolites in the gut, plasma, and brain of α-synuclein-overexpressing (ASO) mice, compared to wild-type (WT) animals, and comparing germ-free (GF) to specific pathogen-free (SPF) animals (n = 5 WT-SPF; n = 6 ASO-SPF; n = 6 WT-GF; n = 6 ASO-GF). Many differentially expressed metabolites in ASO mice are also dysregulated in human PD patients, including amine oxides, bile acids and indoles. The microbial metabolite trimethylamine N-oxide (TMAO) strongly correlates from the gut to the plasma to the brain in mice, notable since TMAO is elevated in the blood and cerebrospinal fluid of PD patients. These findings uncover broad metabolomic changes that are influenced by the intersection of host genetics and microbiome in a mouse model of PD.

Oral and gut microbiome profiles in people with early idiopathic Parkinson's disease

BACKGROUND

Early detection of Parkinson's disease (PD), a neurodegenerative disease with central and peripheral nerve involvement, ensures timely treatment access. Microbes influence nervous system health and are altered in PD.

METHODS

We examined gut and mouth microbiomes from recently diagnosed patients in a geographically diverse, matched case-control, shotgun metagenomics study.

RESULTS

Here, we show greater alpha-diversity in 445 PD patients versus 221 controls. The microbial signature of PD includes overabundance of 16 OTUs, including Streptococcus mutans and Bifidobacterium dentium, and depletion of 28 OTUs. Machine learning models indicate that subspecies level oral microbiome abundances best distinguish PD with reasonably high accuracy (area under the curve: 0.758). Microbial networks are disrupted in cases, with reduced connectivity between short-chain fatty acid-producing bacteria the the gut. Importantly, microbiome diversity metrics are associated with non-motor autonomic symptom severity.

CONCLUSIONS

Our results provide evidence that predictive oral PD microbiome signatures could possibly be used as biomarkers for the early detection of PD, particularly when there is peripheral nervous system involvement.

Microbiome and micronutrient in ALS: From novel mechanisms to new treatments

Amyotrophic lateral sclerosis is a neurodegenerative disorder. Despite extensive studies, it remains challenging to treat ALS. Recent ALS studies have shown dysbiosis (e.g., loss of microbial diversity and beneficial function in the gut microbiota) is correlated with intestinal inflammation and change of intestinal integrity in ALS. The novel concepts and the roles of microbiome and microbial metabolites through the gut-microbiome-neuron axis in ALS pathogenesis have been slowly recognized by the neurology research field. Here, we will discuss the recent progress of microbiome, including bacteria, fungi, and viruses, in the ALS research. We will discuss our understanding of microbial metabolites in ALS. Micronutrition refers to the intake of essential vitamins, minerals, and other micronutrients. We will summarize the literation related to micronutrition and ALS. Furthermore, we will consider the mutual interactions of microbiome and micronutrition in the ALS progression and treatment. We further propose that the mechanistic and translational studies that shift from suspension of disbelief to cogent ingenuity, and from bench study to bed-side application, should allow new strategies of diagnosis and treatment for ALS.

α-Synuclein Overexpression and the Microbiome Shape the Gut and Brain Metabolome in Mice

Pathological forms of the protein α-synuclein contribute to a family of disorders termed synucleinopathies, which includes Parkinson's disease (PD). Most cases of PD are believed to arise from gene-environment interactions. Microbiome composition is altered in PD, and gut bacteria are causal to symptoms and pathology in animal models. To explore how the microbiome may impact PD-associated genetic risks, we quantitatively profiled nearly 630 metabolites from 26 biochemical classes in the gut, plasma, and brain of α-synuclein-overexpressing (ASO) mice with or without microbiota. We observe tissue-specific changes driven by genotype, microbiome, and their interaction. Many differentially expressed metabolites in ASO mice are also dysregulated in human PD patients, including amine oxides, bile acids and indoles. Notably, levels of the microbial metabolite trimethylamine N-oxide (TMAO) strongly correlate from the gut to the plasma to the brain, identifying a product of gene-environment interactions that may influence PD-like outcomes in mice. TMAO is elevated in the blood and cerebral spinal fluid of PD patients. These findings uncover broad metabolomic changes that are influenced by the intersection of host genetics and the microbiome in a mouse model of PD.

Microbiota-gut-brain axis and its therapeutic applications in neurodegenerative diseases

The human gastrointestinal tract is populated with a diverse microbial community. The vast genetic and metabolic potential of the gut microbiome underpins its ubiquity in nearly every aspect of human biology, including health maintenance, development, aging, and disease. The advent of new sequencing technologies and culture-independent methods has allowed researchers to move beyond correlative studies toward mechanistic explorations to shed light on microbiome-host interactions. Evidence has unveiled the bidirectional communication between the gut microbiome and the central nervous system, referred to as the "microbiota-gut-brain axis". The microbiota-gut-brain axis represents an important regulator of glial functions, making it an actionable target to ameliorate the development and progression of neurodegenerative diseases. In this review, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases. As the gut microbiome provides essential cues to microglia, astrocytes, and oligodendrocytes, we examine the communications between gut microbiota and these glial cells during healthy states and neurodegenerative diseases. Subsequently, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases using a metabolite-centric approach, while also examining the role of gut microbiota-related neurotransmitters and gut hormones. Next, we examine the potential of targeting the intestinal barrier, blood-brain barrier, meninges, and peripheral immune system to counteract glial dysfunction in neurodegeneration. Finally, we conclude by assessing the pre-clinical and clinical evidence of probiotics, prebiotics, and fecal microbiota transplantation in neurodegenerative diseases. A thorough comprehension of the microbiota-gut-brain axis will foster the development of effective therapeutic interventions for the management of neurodegenerative diseases.