MSACL 2018 US Abstract

Topic: Metabolomics

Lipidomic and Metabolomic Profiles Investigating the Role of Alzheimer’s Disease and Genotype

Xueyun Zheng (Presenter)
Pacific Northwest National Laboratory

Bio: I am currently a postdoctoral research associate in the ion mobility mass spectrometry research and development group at Pacific Northwest National Laboratory. I finished my Ph.D. at University of California Santa Barbara in 2015, where my research focus on understanding the effects of small molecule inhibitors and familial mutations on the early aggregation of Alzheimer's disease related amyloid beta protein by using ion mobility mass spectrometry. Currently, my research at PNNL focuses on developing novel analysis platforms by coupling IMS-MS with different front-end techniques, including liquid chromatography, online solid phase extraction, supercritical fluidic extraction, for fast and comprehensive small molecule analyses of complex metabolomics and exposomics studies.

Authorship: Xueyun Zheng, Richard D. Smith, Erin S. Baker
Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99354

Short Abstract

The metabolism of metabolites and lipids have been shown to play important roles in Alzheimer’s disease. However the mechanism of how they involved in the AD pathology remain unclear. In this study, we aimed to profile the presence of lipids and how they change in patient with AD. In this study, 126 brain tissue samples that were grey matter from the frontal cortex and cerebellum (disease control tissue) and 63 plasma samples were investigated. In order to study the differences in metabolites and lipid between AD and control grey matter, both metabolomics and lipidomics studies were performed by using ion mobility spectrometry coupled with mass spectrometry (IMS-MS), in combination with an ultra-fast sub-minute Rapidfire SPE or LC separations.

Long Abstract

Introduction

Alzheimer’s disease is a common dementia that affects 47 million people worldwide and will affect 130 million people in 2050 if no cure or prevention is developed. There is a strong body of evidence that couples abnormal lipid metabolism with AD. Lipids are a vital class of molecules that play important roles in biological processes and are also involved in many pathological processes in a variety of diseases such as diabetes, cancers and neurodegenerative diseases. The brain is highly enriched in lipids which are mostly localized in the neuronal membrane and in myelin. The main lipid classes that are altered in AD include cholesterol, sphingolipids, phospholipids and glycerolipids (including gangliosides). However, the mechanisms of how these lipids are involved in AD pathology are still unclear. In this work, we aim to profile the presence of lipids and how they change in patient with AD.

Methods

The tissue samples and plasma samples were extracted by chloroform/methanol extraction where the metabolites and fatty acids are in the methanol layer and the lipids are in the chloroform layer. The extracted solutions were dried by speedvac and reconstitute in methanol and subject to mass spectrometry analyses.

An Agilent 6560 drift tube-IMS-QTOF MS platform was used to profile the metabolite and lipids in AD. For metabolomics study, the samples were analyzed by coupling Rapidfire, an online SPE system to the IMS-MS platform which enables sub-minute ultrafast analyses. Different SPE cartridges such as C18, graphitic carbon, and HILIC were utilized to effectively extract different classes of metabolites. For lipidomics study, liquid chromatography (LC) pre-separation was applied before IMS-MS analysis (LC-IMS-MS/MS). For the LC analyses, a Waters Aquity UPLC system was used. 10 µL lipid samples were then injected onto a reversed phase Waters CSH column (3.0 mm x 150 mm x 1.7 µm particle size). The lipids in the mixture were separated over a 34 min gradient (mobile phase A: acetonitrile/water (40:60) containing 10 mM ammonium acetate; mobile phase B: acetonitrile/isopropylalcohol (10:90) containing 10 mM ammonium acetate) at a flow rate of 250 µl/min. All IMS-MS data containing both m/z and drift time were processed with the Agilent IM-MS Browser and Mass Profiler software. In parallel, all the metabolite samples were ran on a GC-MS platform and the lipids samples were ran on an Obitrap platform to obtain LC-MS/MS data.

Results

In order to study the differences in metabolites and lipid between AD and control grey matter, both metabolomics and lipidomics studies were performed. 126 brain tissue samples that were grey matter from the frontal cortex and cerebellum (disease control tissue) and 63 plasma samples were investigated. These samples include different APOE genotypes like e2/e3, e3/e3, e3/e4 and e4/e4 with the hypothesis that there are E4 dose dependent changes in the brain. By profiling the differences between these different APOE genotypes, we can better understand why apoE4 carriers are at a greater risk of developing AD. Statistical differences were noted in the different brain locations for each patient group. However, more analyses are taking place and will be ready for illustration at MSACL.

Conclusions & Discussion

Different metabolite and lipid profiles were revealed for different locations of the brain tissues for each patient group, which indicates the impact of apoE4 on AD development.


References & Acknowledgements:

We would like to acknowledge support from the National Institute of Environmental Health Sciences of the NIH (R01 ES022190) and the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory for writing this manuscript. This work was performed in the W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the DOE under contract DE-AC05-76RL0 1830.


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