MSACL 2020 US Abstract

Sodium-doped Gold-assisted Imaging Mass Spectrometry Reveals Alterations in Triglyceride Distribution in NAFLD Human Liver as Conditions Progress

Hussam Alamri (1), Nathan Heath Patterson (2) (3), Ethan Yang (2), P Zoroquiain (4) , Anthoula Lazaris (5), Pierre Chaurand (2) and Peter Metrakos (5)
(1) Department of Surgery, McGill University Health Center, Montreal, Quebec, Canada (2) Department of Chemistry, University of Montreal, Montreal, Quebec, Canada. (3) Mass Spectrometry Research Center, Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA (4) Pathology Department, School of Medicine, Pontificia Universidad Católica de Chile, Avda, Santiago, Chile (5) Cancer Research Program, McGill University Health Center-Research Institute, Montreal, Quebec, Canada

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Ethan Yang (Presenter) University of Montreal

Presenter Bio: Ethan Yang is a PhD candidate in Prof. Pierre Chaurand’s lab at the University of Montreal. His research primarily focuses on elaborating new techniques to enhance the sensitivity and selectivity of MALDI-TOF imaging mass spectrometry for use in fundamental and clinical research to better elucidate lipid biomarkers on thin tissue sections. He obtained his B.Sc. at McGill University, majoring in Biochemistry. Since 2012, he has been an active member of the Let’s Talk Science site in Montreal, a national non-profit organization focused on promoting interest in STEM (science, technology, engineering and mathematics) in youth.

Relevant Financial Disclosures (within past 24 months) No relevant financial relationship(s) to disclose. Discussing Products? NO, presenter will NOT present educational content related to products/services of the ineligible company(ies) listed above. Conflict mitigation NOT REQUIRED.

INTRODUCTION: Non-alcoholic fatty liver disease (NALFD) is a chronic condition marked by the abnormal accumulation of triacylglycerides (TAGs) and diacylglycerides (DAGs) in livers of healthy patients with low alcohol consumption. The disease progresses from simple steatosis (SS) to non-alcoholic steatohepatitis (NASH), marked by the shift in lipid accumulations from micro to macro droplets, and eventually cirrhosis. Previous works have highlighted the various roles that different lipid species play in the pathogenesis of NAFLD. However, the exact distribution of TAGs and the effects of the individual TAG species within the liver, particularly the droplets, were not known.

OBJECTIVES: The study aims to utilize the power of CBS-AuLDI IMS to characterize and compare the distribution of TAGs in the micro and macro droplets of healthy livers with those diagnosed with NAFLD and cirrhosis.

METHODS: Five groups of human liver samples from each of the four grades (normal, SS, NASH & cirrhosis) were cryosectioned at 20 µm, thaw-mounted on ITO conductive glass slides and desiccated for ~1 h prior to further sample preparation. A thin layer of sodium salt (approximately 675 µg/cm2) was then deposited onto the sample with an automatic pneumatic sprayer, followed by a 28 nm layer of gold using a Cressington 308R sputter coater. IMS data were acquired at 10 µm spatial resolution in reflectron geometry using a MALDI-TOF/TOF ultrafleXtreme mass spectrometer. The results were preprocessed and further analyzed in R using the Cardinal package.

RESULTS: A total of 22 TAG species across all samples were analyzed and identified. In normal samples, the TAGs accumulated in low abundance around the pericentral zone. Samples deemed SS showed an overall increase in TAGs and clear distinctions of TAG species based on five functional zones. However, the species distribution was not consistent across samples. In the NASH samples, the overall TAG abundance remained high, with saturated TAGs found to be colocalized in the macrovesicular hepatocyles. Microvesicular hepatocytes found surrounding these macrovesicular hepatocytes were found to have an increase in monosaturated TAGs. Upon cirrhosis, the overall TAGs concentration drops again, with patterns of TAG distribution similar to those seen in SS.

CONCLUSION: Au-CBS-LDI IMS analysis of human liver samples at various stages of NAFLD disease revealed an enrichment of saturated TAGs in hepatocytes with macrovesicular steatosis and monosaturated TAGs in hepatocytes with microvesicular steatosis. A larger cohort and more research is needed to understand on the implications of macrovesicular steatosis and saturated TAGs in NAFLD disease progression.