Integrated lipidomics and proteomics network analysis highlights lipid and immunity pathways associated with Alzheimer's disease
INTRODUCTIONThere is an urgent need to understand the molecular mechanisms underlying Alzheimers Disease (AD) to enable early diagnosis and develop effective treatments. Here we aim to investigate Alzheimers dementia using an unsupervised lipid, protein and gene multi-omic integrative approach. METHODSA lipidomics dataset (185 AD, 40 MCI and 185 controls) and a proteomics dataset (201 AD patients, 104 MCI individuals and 97 controls) were utilised for weighted gene co-expression network analyses (WGCNA). An additional proteomics dataset (94 AD, 55 MCI and 100 controls) was included for external proteomics validation. Modules created within each modality were correlated with clinical AD diagnosis, brain atrophy measures and disease progression, as well as with each other. Gene Ontology (GO) enrichment analysis was employed to examine the biological processes and molecular and cellular functions for protein modules associated with AD phenotypes. Lipid species were annotated in the lipid modules associated with AD phenotypes. Associations between established AD risk loci and lipid/protein modules that showed high correlation with AD phenotypes were also explored. RESULTSFive of the 20 identified lipid modules and five of the 17 identified protein modules were correlated with AD phenotypes. Lipid modules comprising of phospholipids, triglycerides, sphingolipids and cholesterol esters, correlated with AD risk loci involved in immune response and lipid metabolism. Five protein modules involved in positive regulation of cytokine production, neutrophil mediated immunity, humoral immune responses were correlated with AD risk loci involved in immune and complement systems. DISCUSSIONWe have shown the first multi-omic study linking genes, proteins and lipids to study pathway dysregulation in AD. Results identified modules of tightly regulated lipids and proteins that were strongly associated with AD phenotypes and could be pathology drivers in lipid homeostasis and innate immunity. Research in ContextO_LILipid and protein modules were preserved amongst Alzheimers disease (AD) patients, participants with mild cognitive impairment (MCI) and controls. Protein modules were also externally validated. C_LIO_LIFive lipid and five protein modules out of a total of thirty-seven correlated with clinical AD diagnosis, brain atrophy measurements and the rate of cognitive decline in AD. C_LIO_LILipid and protein modules associated with AD phenotypes showed associations with established AD risk loci involved in lipid and immune pathways. C_LI