Metabolomic research on the role of interleukin-4 in Alzheimer’s disease

Abstract

Abstract:Inflammation plays a prominent role in the pathogenesis of Alzheimer's disease, affecting both brain and the peripheral system. Thus, modulation of inflammation in animal models of this neurodegenerative disorder may be of great interest to elucidate the pathological mechanisms underlying this inflammatory component. To this end, a metabolomic investigation on a triple transgenic mouse model obtained by crossing the APP/PS1 mice with interleukin-4 knockout mice (a model of impaired immune function) was performed for the first time. Serum samples from transgenic mice and wild type animals were analyzed by direct infusion mass spectrometry followed by multivariate statistics in order to identify altered metabolites. Subsequently, metabolic pathway analysis allowed the elucidation of potential pathological mechanisms associated with the development of Alzheimer-type disorders in response to interleukin-4 deficiency, such as impaired homeostasis of histamine, altered metabolism of amino acids (threonine, aspartate and tyrosine), deregulated urea cycle and increased production of eicosanoids. Therefore, this work demonstrates the potential of this triple transgenic model with modulated immunity for the study of pathological mechanisms associated with inflammation in Alzheimer's disease. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation COMMENTS FOR THE AUTHOR:Reviewer #1: The authors have not included some important requests for clarification to be added to the manuscript by the reviewer therefor another minor revision is required. Abstract still poorly writtenFor example this sentence:Thereby, the investigation of this inflammatory component presents a great potential for the elucidation of pathological mechanisms underlying to disease, the discovery of potential markers of diagnosis and the development of novel therapeutic approaches Abstract was rewritten. Authors commentWe did not use internal standards because we considered that the validation of reproducibility in metabolomic methods is better assessed using QC samples. In this sense, Naz et al. recently described that "although spiking some selected metabolites could give a good approach to the general behaviour of the method, results cannot be assumed for all the components in the sample" (J Chromatogr A 2014;1353:99). Instead, biological QCs show a similar composition to real samples, so they are preferable for validating non-targeted approaches. Thus, "the se of QCs in non-targeted metabolomics analysis can be considered as equivalent to the use of standards in routine target analysis". Reviewer comment: I don't agree with this statement how can you account for a one off issue and internal standards are also in the sample matrix. You need add this justification to the manuscriptInternal standards must present similar physico-chemical properties to the chemical species of interest in the sample. However, metabolomics approaches are not focused on individual compounds, so the use of internal standards in these method...

Metabolomic investigation of systemic manifestations associated with Alzheimer's disease in the APP/PS1 transgenic mouse model

“…Thereby, metabolomic analysis of brain samples has been extensively applied to examine neurochemical perturbations involved in pathological mechanisms occurring in AD, in both humans 33,34 and transgenic mice. 17 Furthermore, previous metabolomic investigations in different biological compartments of this transgenic model showed numerous metabolic alterations, similar to those described in Tables 2-4, affecting brain 18,19 and serum samples. For this reason, the aim of this work was the characterization of the hepatic and renal metabolomic profiles in the APP/PS1 model of AD for the evaluation of possible implications of these metabolically active organs in the development of disease.…”

“…The analysis of brain samples from APP/PS1 and wild-type mice studied in this work has been previously performed using the same metabolomic multi-platform based on GC-MS and RP-UHPLC-MS, 18 as well as by using direct infusion mass spectrometry. 19 These studies demonstrated that hippocampus and cortex are the most perturbed brain regions in this transgenic model, but cerebellum, striatum and olfactory bulbs are also affected to a lesser extent. The comparison of metabolite profiles from liver, kidney and brain regions showed similar alterations in numerous compounds, thus demonstrating the systemic nature of pathological mechanisms underlying these metabolic abnormalities.…”

“…[35][36][37] On the other hand, other metabolomic approaches described in the 46 However, the study of peripheral organs that could be systemically affected has not been previously addressed. 47,48 One of the most remarkable results could be associated with severe bioenergetic impairments, regarding altered levels of numerous energy-related metabolites listed in Tables 3 and 4. To this end, we selected 6 months-old APP/PS1 mice, a transgenic model that reproduces well some of the neuropathological and behavioral deficits observed in human Alzheimer, with a phenotype characterized by deposition of Ab plaques starting from the age of four months, glial activation, and deficits in cognitive functions at the age of 6 months.…”

Metabolomic Fingerprinting of Blood Samples by Direct Infusion Mass Spectrometry: Application in Alzheimer’s Disease Research

“…Free cholesterol is usually detected in lipophilic extracts as a very intense signal at m/z 369. 35 adducts (m/z 404.39) is possible when ammonium salts are added to sample extracts, as described for glycerolipids. Similarly, cholesteryl esters (CE) are also exclusively detected by ESI(?…”

“…Particularly, the use of direct MS platforms has previously been described in a few research articles with the aim to elucidate pathological hallmarks associated with AD development and progression, in both human cohorts and transgenic animal models, as briefly discussed in this section. The methodology optimized by González-Domínguez et al, based on a two-step extraction procedure and subsequent DI-ESI-MS fingerprinting of serum samples, was successfully employed to identify discriminant metabolites between AD patients and healthy control subjects [16,33], as well as between various transgenic mice lines and wildtype littermates [34,35]. These studies revealed significant disturbances in the homeostasis of various lipid classes (e.g., phospholipids, fatty acids, glycerolipids), energy-related metabolites, neurotransmitters, and other metabolites, thus evidencing the utility of simple and easily available serum samples in clinical research.…”