Glycerophosphocholine and Glycerophosphoethanolamine Are Not the Main Sources of the In Vivo (31)P MRS Phosphodiester Signals from Healthy Fibroglandular Breast Tissue at 7 T.

Wybe J M Van Der Kemp,Bertine L Stehouwer,Dennis W J Klomp,Jurgen H Runge,Jannie P Wijnen,Peter R Luijten,Aart J Nederveen

doi:10.3389/fonc.2016.00029

Wybe J M Van Der Kemp, Bertine L Stehouwer + Show 5 more

Open Access

https://doi.org/10.3389/fonc.2016.00029

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Abstract

The identification of the phosphodiester (PDE) (31)P MR signals in the healthy human breast at ultra-high field. In vivo (31)P MRS measurements at 7 T of the PDE signals in the breast were performed investigating the chemical shifts, the transverse- and the longitudinal relaxation times. Chemical shifts and transverse relaxation times were compared with non-ambiguous PDE signals from the liver. The chemical shifts of the PDE signals are shifted -0.5 ppm with respect to glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE), and the transverse and longitudinal relaxation times for these signals are a factor 3 to 4 shorter than expected for aqueous GPC and GPE. The available experimental evidence suggests that GPC and GPE are not the main source of the PDE signals measured in fibroglandular breast tissue at 7 T. These signals may predominantly originate from mobile phospholipids.

Highlights

The phosphomonoesters (PME), phosphocholine (PC) and phosphoethanolamine (PE), and the phosphodiesters (PDEs), glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE), are involved in cell membrane metabolism
The chemical shifts of the GPC and GPE signals in the liver (Figure 2C) do not correspond to the signals observed in the breast spectra (Figures 2A,B), which are usually labeled GPC and GPE, while the chemical shifts of the other metabolites (PE, PC, inorganic phosphate (Pi), γ-ATP, α-ATP) in liver and breast do match
If we would shift the breast spectrum by +0.5 ppm to match the PDE signals between breast and liver, this would correspond to a shift in pH of +0.4 units based on Pi chemical shift

Summary

Introduction

The phosphomonoesters (PME), phosphocholine (PC) and phosphoethanolamine (PE), and the phosphodiesters (PDEs), glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE), are involved in cell membrane metabolism. In contrast to some ex vivo methods, where extraction techniques are used to separate aqueous pools of metabolites from lipid pools, in vivo methods will obtain signals from membrane phospholipids (MPL) [13, 14]. As these MPL have chemical shifts similar to GPC, e.g., glycerophosphatidylethanolamine (GPtE) has almost identical chemical shift as GPC [15, 16] (the molecular structures and chemical shifts are shown in Figure 1) – in vivo distinction of these compounds is hampered

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