Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS)-based metabolomics for comparison of caffeinated and decaffeinated coffee and its implications for Alzheimer's disease.

Kai Lun Chang,Paul C. Ho,Enzo Palombo

doi:10.1371/journal.pone.0104621

Abstract

Findings from epidemiology, preclinical and clinical studies indicate that consumption of coffee could have beneficial effects against dementia and Alzheimer’s disease (AD). The benefits appear to come from caffeinated coffee, but not decaffeinated coffee or pure caffeine itself. Therefore, the objective of this study was to use metabolomics approach to delineate the discriminant metabolites between caffeinated and decaffeinated coffee, which could have contributed to the observed therapeutic benefits. Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS)-based metabolomics approach was employed to characterize the metabolic differences between caffeinated and decaffeinated coffee. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed distinct separation between the two types of coffee (cumulative Q2 = 0.998). A total of 69 discriminant metabolites were identified based on the OPLS-DA model, with 37 and 32 metabolites detected to be higher in caffeinated and decaffeinated coffee, respectively. These metabolites include several benzoate and cinnamate-derived phenolic compounds, organic acids, sugar, fatty acids, and amino acids. Our study successfully established GC-TOF-MS based metabolomics approach as a highly robust tool in discriminant analysis between caffeinated and decaffeinated coffee samples. Discriminant metabolites identified in this study are biologically relevant and provide valuable insights into therapeutic research of coffee against AD. Our data also hint at possible involvement of gut microbial metabolism to enhance therapeutic potential of coffee components, which represents an interesting area for future research.

Highlights

There is a growing body of epidemiological evidence that supports therapeutic roles of coffee consumption against development of Alzheimer’s disease (AD)
We first established suitability of GC-TOF-MS as an analytical platform for metabolomics analysis of coffee samples by carrying out quality control (QC) analysis. 5 different samples were made for each of the caffeinated and decaffeinated coffee to be used as QC samples
Total ion chromatograms from GC-TOF-MS analyses of injected samples for both caffeinated and decaffeinated coffee were shown in Figure 1A and 1B, respectively

Summary

Introduction

There is a growing body of epidemiological evidence that supports therapeutic roles of coffee consumption against development of Alzheimer’s disease (AD). In a study with follow-up of 21 years, people who drank 3–5 cups of coffee per day during midlife were observed to have 65% reduction in risk of developing AD later in life as compared to those who drank little or no coffee [1]. Recognizing that epidemiologic studies are not direct evidence, Cao and colleagues obtained the first direct human evidence to support benefits of coffee consumption in AD [3]. They observed that mild cognitive impairment (MCI) patients with higher plasma caffeine levels have delayed onset or lower risk of dementia during a 2–4 year follow-up period, and most of caffeine sources for study subjects were traced back to coffee consumption [3]. This study strengthened therapeutic roles of coffee consumption in preventing AD, and proposed coffee consumption as prophylactic intervention far before surfacing of AD symptoms

Objectives

Methods

Results

Conclusion