title: Understanding the cholesterol metabolism-perturbing effects of docosahexaenoic acid by gas chromatography-mass spectrometry targeted metabonomic profiling.
abstract: OBJECTIVE
  Over the past few decades, docosahexaenoic acid (DHA) has gained special attention for management of cholesterol-associated metabolic disorders and neurodegenerative diseases such as Alzheimer's disease (AD) owing to its neuroprotective, anti-inflammatory and hypolipidemic properties. Several epidemiological studies have reported the effect of DHA in reducing the risk of developing AD by lowering cholesterol. Hypercholesterolemia is a pro-amyloidogenic factor influencing the enzymatic processing of amyloid-β precursor protein (AβPP) to toxic β-amyloid. However, the mechanism by which DHA modulates the cholesterol pathway has not been established. Thus, the objective of this study was to investigate the mechanism of regulation of cholesterol metabolism by DHA in an AβPP695overexpressing AD cell model.
  
  
  METHODS
  A gas chromatography/mass spectrometry method was developed and validated for the targeted profiling of 11 cholesterol metabolites in DHA-treated Chinese hamster ovary wild-type (CHO-wt) and AβPP695overexpressing (CHO-AβPP695) cells. The differential metabolite profiles between DHA- and vehicle-treated groups were further analyzed using fold change values of the ratio of concentration of metabolites in CHO-AβPP695to CHO-wt cells. Effect of DHA on key rate-limiting enzymatic activities within the cholesterol pathway was established using biochemical assays.
  
  
  RESULTS
  Our results showed that DHA reduced the levels of key cholesterol anabolites and catabolites in CHO-AβPP695cells as compared to CHO-wt cells. Further enzymatic studies revealed that the cholesterol-lowering effect of DHA was mediated by regulating HMG-CoA reductase and squalene epoxidase enzyme activities.
  
  
  CONCLUSIONS
  We demonstrate for the first time the dual effects of DHA in inhibiting HMG-CoA reductase and squalene epoxidase and modulating the sterol biosynthesis axis of the cholesterol pathway in AβPP695overexpressing AD. Our novel findings underscore the potential of DHA as a multi-target hypocholesterolemic agent for the prophylaxis of AD and other cholesterol-associated diseases.
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore.
authors.forename: Priti
authors.initials: P
authors.lastname: Bahety
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore.
authors.forename: Thi Hai
authors.initials: TH
authors.lastname: Van Nguyen
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Hong
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore.
authors.forename: Luqi
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore. phaccye@nus.edu.sg.
authors.forename: Eric Chun Yong
authors.initials: ECY
authors.lastname: Chan
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Republic of Singapore. phaeplr@nus.edu.sg.
authors.forename: Pui Lai Rachel
authors.initials: PLR
authors.lastname: Ee
mesh_terms: D000544:Alzheimer Disease / Q000517:prevention & control; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D008401:Gas Chromatography-Mass Spectrometry; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D050356:Lipid Metabolism / Q000187:drug effects*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050603:Squalene Monooxygenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013261:Sterols / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D000924:Anticholesteremic Agents; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D013261:Sterols; D004281:Docosahexaenoic Acids; D006903:Hydroxymethylglutaryl CoA Reductases; D050603:Squalene Monooxygenase
keywords: Amyloid β-precursor protein (AβPP); Cholesterol; Docosahexaenoic acid (DHA); Gas chromatography; HMG-CoA reductase; Metabonomics; Squalene epoxidase