Lipids as biomarkers of brain disorders

Potential Transdiagnostic Lipid Mediators of Inflammatory Activity in Individuals With Serious Mental Illness

Mental disorders are heterogeneous and psychiatric comorbidities are common. Previous studies have suggested a link between inflammation and mental disorders. This link can manifest as increased levels of proinflammatory mediators in circulation and as signs of neuroinflammation. Furthermore, there is strong evidence that individuals suffering from psychiatric disorders have increased risk of developing metabolic comorbidities. Our group has previously shown that, in a cohort of low-functioning individuals with serious mental disorders, there is increased expression of genes associated with the NLRP3 inflammasome, a known sensor of metabolic perturbations, as well as increased levels of IL-1-family cytokines. In the current study, we set out to explore the interplay between disease-specific changes in lipid metabolism and known markers of inflammation. To this end, we performed mass spectrometry-based lipidomic analysis of plasma samples from low-functioning individuals with serious mental disorders (n = 39) and matched healthy controls (n = 39). By identifying non-spurious immune-lipid associations, we derived a partial correlation network of inflammatory markers and molecular lipids. We identified levels of lipids as being altered between individuals with serious mental disorders and controls, showing associations between lipids and inflammatory mediators, e.g., osteopontin and IL-1 receptor antagonist. These results indicate that, in low-functioning individuals with serious mental disorders, changes in specific lipids associate with immune mediators that are known to affect neuroinflammatory diseases.

Effect of Heavy Ion 12C6+ Radiation on Lipid Constitution in the Rat Brain

Heavy ions refer to charged particles with a mass greater than four (i.e., alpha particles). The heavy ion irradiation used in radiotherapy or that astronauts suffer in space flight missions induces toxicity in normal tissue and leads to short-term and long-term damage in both the structure and function of the brain. However, the underlying molecular alterations caused by heavy ion radiation have yet to be completely elucidated. Herein, untargeted and targeted lipidomic profiling of the whole brain tissue and blood plasma 7 days after the administration of the 15 Gy (260 MeV, low linear energy (LET) = 13.9 KeV/μm) plateau irradiation of disposable ¹²C⁶⁺ heavy ions on the whole heads of rats was explored to study the lipid damage induced by heavy ion radiation in the rat brain using ultra performance liquid chromatography-mass spectrometry (UPLC–MS) technology. Combined with multivariate variables and univariate data analysis methods, our results indicated that an orthogonal partial least squares discriminant analysis (OPLS–DA) could clearly distinguish lipid metabolites between the irradiated and control groups. Through the combination of variable weight value (VIP), variation multiple (FC), and differential (p) analyses, the significant differential lipids diacylglycerols (DAGs) were screened out. Further quantitative targeted lipidomic analyses of these DAGs in the rat brain tissue and plasma supported the notion that DAG 47:1 could be used as a potential biomarker to study brain injury induced by heavy ion irradiation.

Studies on the Neuromodulatory Effects of Ginkgo biloba on Alterations in Lipid Composition and Membrane Integrity of Rat Brain Following Aluminium Neurotoxicity

Brain contains the highest lipid content involved in various structural and physiological activities such as structural development, neurogenesis, synaptogenesis, signal transduction and myelin sheath formation. Lipids bilayer is essential to maintain the structural integrity for the physiological functions of protein. Impairments in lipid metabolism and its composition can lead to the progression of various brain ailments such as neurodegenerative and neuropsychiatric disorders. Aluminium (Al), the potent neurotoxin has been linked to Alzheimer's disease (AD) like pathology. Al can bind to biomembrane and influence oligomerization and conformational changes of proteins by acting as cross-linkers. The present study evaluated the influence of Ginkgo biloba (GBE) on the lipid profile alterations induced by Al lactate in hippocampal and cortical regions using FTIR spectroscopy. Rats were exposed with 10 mg/kg b.w. (intraperitoneal) of Al lactate for 6 weeks. This was followed by a treatment protocol of GBE (100 mg/kg b.w.) both preexposure (2 weeks) and conjunctive (6 weeks) exposure. A self recovery group was also included, where Al withdrawal was done for 2 weeks post Al exposure. A significant decrease in peak areas of cholesterol, sphingolipids and phospholipids was observed in Al treated groups. Further, polyunsaturated fatty acids and membrane fluidity has also decreased, as revealed by olefinic and methyl asymmetric stretching bands. Al treatment significantly increased the fluorescence polarization, anisotropy and order parameter, which however were normalized following GBE supplementation. Results also showed that pretreatment with GBE provided more beneficial effects on the adverse changes following Al in membrane composition and behavioral outcome.

Exploring Sphingolipid Implications in Neurodegeneration

Over the past decade, it was found that relatively simple sphingolipids, such as ceramide, sphingosine, sphingosine-1-phosphate, and glucosylceramide play important roles in neuronal functions by regulating rates of neuronal growth and differentiation. Homeostasis of membrane sphingolipids in neurons and myelin is essential to prevent the loss of synaptic plasticity, cell death and neurodegeneration. In our review we summarize data about significant brain cell alterations of sphingolipids in different neurodegenerative diseases such as Alzheimer's disease, Parkinson disease, Amyotrophic Lateral Sclerosis, Gaucher's, Farber's diseases, etc. We reported results obtained in brain tissue from both animals in which diseases were induced and humans in autopsy samples. Moreover, attention was paid on sphingolipids in biofluids, liquor and blood, from patients. In Alzheimer's disease sphingolipids are involved in the processing and aggregation of β-amyloid and in the transmission of the cytotoxic signal β-amyloid and TNFα-induced. Recently, the gangliosides metabolism in transgenic animals and the relationship between blood sphingolipids changes and cognitive impairment in Alzheimer's disease patients have been intensively studied. Numerous experiments have highlighted the involvement of ceramide and monohexosylceramide metabolism in the pathophysiology of the sporadic forms of Parkinson's disease. Moreover, gene mutations of the glucocerebrosidase enzyme were considered as responsible for Parkinson's disease via transition of the monomeric form of α-synuclein to an oligomeric, aggregated toxic form. Disturbances in the metabolism of ceramides were also associated with the appearance of Lewy's bodies. Changes in sphingolipid metabolism were found as a manifestation of Amyotrophic Lateral Sclerosis, both sporadic and family forms, and affected the rate of disease development. Currently, fingolimod (FTY720), a sphingosine-1-phosphate receptor modulator, is the only drug undergoing clinical trials of phase II safety for the treatment of Amyotrophic Lateral Sclerosis. The use of sphingolipids as new diagnostic markers and as targets for innovative therapeutic strategies in different neurodegenerative disorders has been included.

Sphingolipids in food and their critical roles in human health

Sphingolipids (SLs) are ubiquitous structural components of cell membranes and are essential for cell functions under physiological conditions or during disease progression. Abundant evidence supports that SLs and their metabolites, including ceramide (Cer), ceramide-1-phosphate (C1P), sphingosine (So), sphingosine-1-phosphate (S1P), are signaling molecules that regulate a diverse range of cellular processes and human health. However, there are limited reviews on the emerging roles of exogenous dietary SLs in human health. In this review, we discuss the ubiquitous presence of dietary SLs, highlighting their structures and contents in foodstuffs, particularly in sea foods. The digestion and metabolism of dietary SLs is also discussed. Focus is given to the roles of SLs in both the etiology and prevention of diseases, including bacterial infection, cancers, neurogenesis and neurodegenerative diseases, skin integrity, and metabolic syndrome (MetS). We propose that dietary SLs represent a "functional" constituent as emerging strategies for improving human health. Gaps in research that could be of future interest are also discussed.

Changes in the Metabolism of Sphingoid Bases in the Brain and Spinal Cord of Transgenic FUS(1-359) Mice, a Model of Amyotrophic Lateral Sclerosis

The aim of this study was to evaluate changes in the content of sphingoid bases - sphingosine (SPH), sphinganine, and sphingosine-1-phosphate (SPH-1-P) - and in expression of genes encoding enzymes involved in their metabolism in the brain structures (hippocampus, cortex, and cerebellum) and spinal cord of transgenic FUS(1-359) mice. FUS(1-359) mice are characterized by motor impairments and can be used as a model of amyotrophic lateral sclerosis (ALS). Lipids from the mouse brain structures and spinal cord after 2, 3, and 4 months of disease development were analyzed by chromatography/mass spectrometry, while changes in the expression of the SPHK1, SPHK2, SGPP2, SGPL1, ASAH1, and ASAH2 genes were assayed using RNA sequencing. The levels of SPH and sphinganine (i.e., sphingoid bases with pronounced pro-apoptotic properties) were dramatically increased in the spinal cord at the terminal stage of the disease. The ratio of the anti-apoptotic SPH-1-P to SPH and sphinganine sharply reduced, indicating massive apoptosis of spinal cord cells. Significant changes in the content of SPH and SPH-1-P and in the expression of genes related to their metabolism were found at the terminal ALS stage in the spinal cord. Expression of the SGPL gene (SPH-1-P lyase) was strongly activated, while expression of the SGPP2 (SPH-1-P phosphatase) gene was reduced. Elucidation of mechanisms for the regulation of sphingolipid metabolism in ALS will help to identify molecular targets for the new-generation drugs.