Mapping the triglyceride distribution in NAFLD human liver by MALDI imaging mass spectrometry reveals molecular differences in micro and macro steatosis
Hepatic lipid accumulation, mainly in the form of triglycerides (TGs), is the hallmark of non-alcoholic fatty liver disease (NAFLD). To date, the spatial distribution of individual lipids in NAFLD-affected livers is not well characterized. This study aims to map the triglyceride distribution in normal human liver samples and livers with NAFLD and cirrhosis with imaging mass spectrometry (MALDI IMS). Specifically, whether individual triglyceride species differing by fatty acid chain length and degree of saturation correlate with the histopathological features of NAFLD as identified with classical H&E. Using a recently reported sodium-doped gold-assisted laser desorption/ionization IMS sample preparation, 20 human liver samples (five normal livers, five samples with simple steatosis, five samples with steatohepatitis, and five samples with cirrhosis) were analyzed at 10-μm lateral resolution. A total of 24 individual lipid species, primarily neutral lipids, were identified (22 TGs and two phospholipids). In samples with a low level of steatosis, TGs accumulated around the pericentral zone. In all samples, TGs with different degrees of side-chain saturation and side-chain length demonstrated differential distribution. Furthermore, hepatocytes containing macro lipid droplets were highly enriched in fully saturated triglycerides. This enrichment was also observed in areas of hepatocyte ballooning in samples with steatohepatitis and cirrhosis. In conclusion, macro lipid droplets in NAFLD are enriched in fully saturated triglycerides, indicating a possible increase in de novo lipogenesis that leads to steatohepatitis and cirrhosis.
KeywordsNon-alcoholic fatty liver disease Triglycerides Imaging mass spectrometry Lipids Fatty acid/synthesis
- AuLDI IMS
Gold-assisted laser desorption/ionization imaging mass spectrometry
De novo lipogenesis
Free fatty acids
- MALDI IMS
Matrix-assisted laser desorption/ionization imaging mass spectrometry
Non-alcoholic fatty liver disease
Optimal cutting temperature compound
Saturated fatty acids
We would like to acknowledge the support of Stephanie Petrillo and Abdellatif Amri for technical support, the MUHC Liver Disease Biobank for all human specimens, and the patients who consented to providing samples to the Biobank, with whose support of this study would not have been possible.
This publication was supported by National Cancer Institute of the National Institutes of Health under award number R01CA198103 and by the Natural Sciences and Engineering Research Council of Canada.
Compliance with ethical standards
Informed consent was obtained from all patients through the McGill University Health Center Liver Disease Biobank. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the research ethics board of the McGill University Health Centre.
Conflict of interest
The authors declare that there is no conflict of interest.
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