Overview of Lipid Biomarkers in Amyotrophic Lateral Sclerosis (ALS)

Alterations in nasal microbiota of patients with amyotrophic lateral sclerosis

BACKGROUND

Links between alterations in gut microbiota composition and amyotrophic lateral sclerosis (ALS) have previously been reported. This study aimed to examine the microbiota in the nasal cavity of ALS.

METHODS

Sixty-six ALS patients and 40 healthy caregivers who live in close proximity with patients were enrolled. High throughput metagenomic sequencing of the 16S ribosomal deoxyribonucleic acid (rDNA) gene V3-V4 region of nasal microbiota was used to characterize the alpha and beta diversity and relative abundance of bacterial taxa, predict function, and conduct correlation analysis between specific taxa and clinical features.

RESULTS

The nasal microbiome of ALS patients showed lower alpha diversity than that of corresponding healthy family members. Genera Gaiella , Sphingomonas , Polaribacter _1, Lachnospiraceae _NK4A136_group, Klebsiella , and Alistipes were differentially enriched in ALS patients compared to controls. Nasal microbiota composition in ALS patients significantly differed from that in healthy subjects (unweighted UniFrac P = 0.001), while Linear discriminant analysis Effect Size (LEfSe) analysis indicated that Bacteroidetes and Firmicutes dominated healthy nasal communities at the phylum level, whereas Actinobacteria was the predominant phylum and Thermoleophilia was the predominant class in ALS patients. Genus Faecalibacterium and Alistipes were positively correlated with ALS functional rating scale revised (ALSFRS-R; rs = 0.349, P = 0.020 and rs = 0.393, P = 0.008), while Prevotella -9 and Bacteroides operational taxonomic units (OTUs) were positively associated with lung function (FVC) in ALS patients ( rs = 0.304, P = 0.045, and rs = 0.300, P = 0.048, respectively). Prevotella -1 was positively correlated with white blood cell counts (WBC, rs = 0.347, P = 0.021), neutrophil percentage (Neu%, rs = 0.428, P = 0.004), and neutrophil-to-lymphocyte ratio (NLR, rs = 0.411, P = 0.006), but negatively correlated with lymphocyte percentage (Lym%, rs = -0.408, P = 0.006). In contrast, Streptococcus was negatively associated with Neu% ( rs = -0.445, P = 0.003) and NLR ( rs = -0.436, P = 0.003), while positively associated with Lym% ( rs = 0.437, P = 0.003). No significant differences in nasal microbiota richness and evenness were detected among the severe and mild ALS patients.

CONCLUSIONS

ALS is accompanied by altered nasal microbial community composition and diversity. The findings presented here highlight the need to understand how dysbiosis of nasal microbiota may contribute to the development of ALS.

Integrating Widely Targeted Lipidomics and Transcriptomics Unravels Aberrant Lipid Metabolism and Identifies Potential Biomarkers of Food Allergies in Rats

SCOPE

Oral food challenges (OFCs) are currently the gold standard for determining the clinical reactivity of food allergy (FA) but are time-consuming, expensive, and risky. To screen novel peripheral biomarkers of FA and characterize the aberrant lipid metabolism in serum, 24 rats are divided into four groups: peanut, milk, and shrimp allergy (PA, MA, and SA, respectively) and control groups, with six rats in each group, and used for widely targeted lipidomics and transcriptomics analysis.

METHODS AND RESULTS

Widely targeted lipidomics reveal 144, 162, and 206 differentially accumulated lipids in PA, MA, and SA groups, respectively. The study integrates widely targeted lipidomics and transcriptomics and identifies abnormal lipid metabolism correlated with widespread differential accumulation of diverse lipids (including triacylglycerol, diacylglycerol, sphingolipid, and glycerophospholipid) in PA, MA, and SA. Simplified random forest classifier is constructed through five repetitions of 10-fold cross-validation to distinguish allergy from control. A subset of 15 lipids as potential biomarkers allows for more reliable and more accurate prediction of FA. Independent replication validates the reproducibility of potential biomarkers.

CONCLUSION

The results reveal the major abnormalities in lipid metabolism and suggest the potential role of lipids as novel molecular signatures for FA.

Amyotrophic Lateral Sclerosis and Serum Lipid Level Association: A Systematic Review and Meta-Analytic Study

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with unknown etiology. Many metabolic alterations occur during ALS progress and can be used as a method of pre-diagnostic and early diagnosis. Dyslipidemia is one of the physiological changes observed in numerous ALS patients. The aim of this study is to analyze the possible relationship between the rate of disease progression (functional rating scale (ALS-FRS)) and the plasma lipid levels at the early stage of ALS. A systematic review was carried out in July 2022. The search equation was "Triglycerides AND amyotrophic lateral sclerosis" and its variants. Four meta-analyses were performed. Four studies were included in the meta-analysis. No significant differences were observed between the lipid levels (total cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol) and the ALS-FRS score at the onset of the disease. Although the number of studies included in this research was low, the results of this meta-analytic study suggest that there is no clear relationship between the symptoms observed in ALS patients and the plasma lipid levels. An increase in research, as well as an expansion of the geographical area, would be of interest.

SPTSSA variants alter sphingolipid synthesis and cause a complex hereditary spastic paraplegia

Sphingolipids are a diverse family of lipids with critical structural and signalling functions in the mammalian nervous system, where they are abundant in myelin membranes. Serine palmitoyltransferase, the enzyme that catalyses the rate-limiting reaction of sphingolipid synthesis, is composed of multiple subunits including an activating subunit, SPTSSA. Sphingolipids are both essential and cytotoxic and their synthesis must therefore be tightly regulated. Key to the homeostatic regulation are the ORMDL proteins that are bound to serine palmitoyltransferase and mediate feedback inhibition of enzymatic activity when sphingolipid levels become excessive. Exome sequencing identified potential disease-causing variants in SPTSSA in three children presenting with a complex form of hereditary spastic paraplegia. The effect of these variants on the catalytic activity and homeostatic regulation of serine palmitoyltransferase was investigated in human embryonic kidney cells, patient fibroblasts and Drosophila. Our results showed that two different pathogenic variants in SPTSSA caused a hereditary spastic paraplegia resulting in progressive motor disturbance with variable sensorineural hearing loss and language/cognitive dysfunction in three individuals. The variants in SPTSSA impaired the negative regulation of serine palmitoyltransferase by ORMDLs leading to excessive sphingolipid synthesis based on biochemical studies and in vivo studies in Drosophila. These findings support the pathogenicity of the SPTSSA variants and point to excessive sphingolipid synthesis due to impaired homeostatic regulation of serine palmitoyltransferase as responsible for defects in early brain development and function.

The Need for Biomarkers in the ALS-FTD Spectrum: A Clinical Point of View on the Role of Proteomics

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are severely debilitating and progressive neurodegenerative disorders. A distinctive pathological feature of several neurodegenerative diseases, including ALS and FTD, is the deposition of aberrant protein inclusions in neuronal cells, which leads to cellular dysfunction and neuronal damage and loss. Despite this, to date, the biological process behind developing these protein inclusions must be better clarified, making the development of disease-modifying treatment impossible until this is done. Proteomics is a powerful tool to characterize the expression, structure, functions, interactions, and modifications of proteins of tissue and biological fluid, including plasma, serum, and cerebrospinal fluid. This protein-profiling characterization aims to identify disease-specific protein alteration or specific pathology-based mechanisms which may be used as markers of these conditions. Our narrative review aims to highlight the need for biomarkers and the potential use of proteomics in clinical practice for ALS-FTD spectrum disorders, considering the emerging rationale in proteomics for new drug development. Certainly, new data will emerge in the near future in this regard and support clinicians in the development of personalized medicine.

High-resolution mass spectrometry reveals a complex ganglioside pattern and novel polysialylated structures associated with the human motor cortex

We have developed here a superior methodology based on high-resolution mass spectrometry for screening and fragmentation analysis of gangliosides extracted and purified from the human motor cortex . The experiments, conducted on a nanoelectrospray Orbitrap mass spectroscope in the negative ion mode, allowed the discrimination in the native mixture extracted from human motor cortex of no less than 83 different gangliosides, which represents the highest number of structures identified so far in this brain region. The spectral data, acquired in high-resolution mass spectrometry mode with a remarkable sensitivity and an average mass accuracy of 4.48 ppm, also show that the gangliosidome of motor cortex is generally characterized by species exhibiting a much higher degree of sialylation than previously known. Motor cortex was found dominated by complex structures with a sialylation degree ≥3, exhibiting long saccharide chains, in the G1 class. Fucogangliosides and species with the glycan chain elongated by either O-acetylation and/or acetate anion attachments were also detected; the later modification was for the first time discovered in this brain region. Of major significance is the identification of hepta and octasialylated species of GS1 and GO1 type, which are among the structures with the longest oligosaccharide chain discovered so far in the human brain. In the last stage of research, tandem mass spectrometry performed by higher energy collision dissociation provided structural data documenting the occurrence of GT1b (d18:1/20:0) isomer in the human motor cortex.

Understanding and managing metabolic dysfunction in Amyotrophic Lateral Sclerosis

INTRODUCTION

Amyotrophic Lateral Sclerosis (ALS) is a fatal motor neuron disease that leads to death after a median survival of 36 months. The development of an effective treatment has proven to be extremely difficult due to the inadequate understanding of the pathogenesis of ALS. Energy metabolism is thoroughly involved in the disease based on the discoveries of hypermetabolism, lipid/glucose metabolism, the tricarboxylic acid (TCA) cycle, and mitochondrial impairment.

AREA COVERED

Many perturbed metabolites within these processes have been identified as promising therapeutic targets. However, the therapeutic strategies targeting these pathways have failed to produce clinically significant results. The authors present in this review the metabolic disturbances observed in ALS and the derived-therapeutics.

EXPERT OPINION

The authors suggest that this is due to the insufficient knowledge of the relationship between the metabolic targets and the type of ALS of the patient, depending on genetic and environmental factors. We must improve our understanding of the pathological mechanisms and pay attention to the subtle hidden effects of changing diet, for example, and to use this strategy in addition to other drugs or to use metabolism status to determine subgroups of patients.