Targeted and Untargeted Mass Spectrometry Reveals the Impact of High-Fat Diet on Peripheral Amino Acid Regulation in a Mouse Model of Alzheimer’s Disease

Abstract

Recent research regarding amino acid metabolism has shown that there may be a link between obesity and Alzheimer’s disease (AD). This work reports a metabolomics study using targeted and untargeted mass spectrometry-based metabolomic strategies to investigate this link. Targeted hydrophilic interaction liquid chromatography–triple quadrupole mass spectrometry and untargeted reversed-phase liquid chromatography-high resolution tandem mass spectrometry assays were developed to analyze the metabolic changes that occur in AD and obesity. APPSwe/PS1ΔE9 (APP/PSEN1) transgenic mice (to represent familial or early-onset AD) and wild-type littermate controls were fed either a high-fat diet (HFD, 60% kcal from lard) or a low-fat diet (LFD, 10% kcal from lard) from 2 months of age or a reversal diet (HFD, followed by LFD from 9.5 months). For targeted analyses, we applied the guidelines outlined in the Clinical and Laboratory Standards Institute (CLSI) LC–MS C62-A document and the U.S. Food and Drug Administration (FDA) bioanalytical method validation guidance for industry to evaluate the figures of merit of the assays. Our targeted and untargeted metabolomics results suggest that numerous peripheral pathways, specifically amino acid metabolism and fatty acid metabolism, were significantly affected by AD and diet. Multiple amino acids (including alanine, glutamic acid, leucine, isoleucine, and phenylalanine), carnitines, and members of the fatty acid oxidation pathway were significantly increased in APP/PSEN1 mice on HFD compared to those on LFD. More substantial effects and changes were observed in the APP/PSEN1 mice than in the WT mice, suggesting that they were more sensitive to an HFD. These dysregulated peripheral pathways include numerous amino acid pathways and fatty acid beta oxidation and suggest that obesity combined with AD further enhances cognitive impairment, possibly through aggravated mitochondrial dysfunction. Furthermore, partial reversibility of many altered pathways was observed, which highlights that diet change can mitigate the metabolic effects of AD. The same trends in individual amino acids were observed in both strategies, highlighting the biological validity of the results.

The role of plant‐derived natural antioxidants in reduction of oxidative stress

“…Alzheimer's disease (AD) is considered as the most common age‐associated neurodegenerative disease, and because of the high metabolic activity, the brain regions such as the hippocampus are vulnerable to glucose and oxygen supply variations 123 . Brain inflammation could be achieved with natural molecules, specifically polyphenolic flavonoids.…”

“…81 Alzheimer's disease (AD) is considered as the most common age-associated neurodegenerative disease, and because of the high metabolic activity, the brain regions such as the hippocampus are vulnerable to glucose and oxygen supply variations. 123 Brain inflammation could be achieved with natural molecules, specifically polyphenolic flavonoids. The flavone luteolin showed improvement of AD, and other disorders through various mechanisms, including inhibition of microglia activation, AchE133 inhibition, and prevention of Ab42 plaque formation, inhibition of fibrillary β-amyloid-induced inflammation, decreasing zinc-induced tau phosphorylation, and inhibition of reducing mucin-type O-gycosylation of amyloid precursor protein.…”

Simultaneous Quantitation and Discovery (SQUAD) Analysis: Combining the Best of Targeted and Untargeted Mass Spectrometry-Based Metabolomics

“…Another methodology based on HRAM analysis was developed using targeted and untargeted screening strategies to discover potential biomarkers for the reliable detection of food product adulteration [54][55][56]. Many other studies from various research fields have also benefited from combining MS-based data from targeted and untargeted approaches [57][58][59][60][61][62][63][64][65][66][67], and even NMR-targeted data with MS-untargeted analysis [68]. Melnik et al 2017, for example, developed a platform coupling targeted and untargeted metabolomics via splitting the flow from one UPLC into an orbitrap DDAbased discovery and a triple-quadrupole (TQ) MRM quantitation method to study the association between the metabolome and microbiome of human fecal samples [69].…”

Standard Doses of Cholecalciferol Reduce Glucose and Increase Glutamine in Obesity-Related Hypertension: Results of a Randomized Trial

“…To that end, normo- and hypertensive patients with underlying obesity or metabolic syndrome were analyzed after cholecalciferol supplementation. Moreover, given that high-fat diets in combination with other diseases could potentiate the dysregulation of numerous pathways of amino acid and lipid metabolism [ 23 ], we hypothesized that obese hypertensives could represent a good model to track the effects of interventions aimed to modulate the serum metabolome.…”