Multiplexed Targeted Spatial Mass Spectrometry Imaging Assays to monitor lipids and NAD+ metabolites in CD38 knockout mice exhibiting improved metabolism

TL;DR

A new mass spectrometry method reveals how lipid and NAD+ levels change in the livers of mice lacking the CD38 enzyme, which is linked to better metabolism.

Contribution

A novel iprm-PASEF workflow combining TIMS and MALDI enables confident identification and quantification of lipid isomers and NAD+ metabolites in spatial MSI.

Findings

CD38−/− livers showed increased NAD+ and decreased ADPR compared to wild-type mice.

The iprm-PASEF method allowed differentiation of lipid isomers at the MS2 fragment ion level.

The approach provides robust and specific spatial metabolic insights in liver tissues.

Abstract

Mass spectrometry imaging (MSI) is a rapidly advancing technology that provides mapping of the spatial molecular landscape of tissues for a variety of analytes. Matrix-assisted laser desorption/ionization (MALDI)-MSI is commonly employed, however, confident in situ identification and accurate quantification of analytes remain challenging. We present a novel imaging methodology combining trapped ion mobility spectrometry (TIMS)-based parallel accumulation-serial fragmentation (PASEF) with MALDI ionization for targeted imaging parallel reaction monitoring (iprm-PASEF). We investigated the spatial distribution of lipids and metabolites in liver tissues from wild-type and CD38 knockout mice (CD38−/−). CD38, an enzyme involved in nicotinamide adenine dinucleotide (NAD+) metabolism, significantly influences liver metabolic function and contributes to age-related NAD+ decline. Although CD38 deletion previously was linked to improved metabolic phenotypes, the underlying spatial metabolic mechanisms are poorly understood. The spatial iprm-PASEF workflow enabled confident identification and differentiation of lipid isomers at the MS2 fragment ion level and revealed increased NAD+ and decreased adenosine diphosphate ribose (ADPR), a by-product of NAD+ hydrolysis, in CD38−/− livers. This approach provided confident, specific, and robust MS2-based identification and quantification of fragment ions in spatial MSI experiments. Additionally, the innovative iprm-PASEF opens unprecedented opportunities for spatial metabolomics and lipidomics, offering spatially resolved insights into molecular mechanisms.

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