Quantitative analysis of prostate metabolites using ¹H HR-MAS spectroscopy

A method was developed to quantify prostate metabolite concentrations using ¹H high-resolution magic angle spinning (HR-MAS) spectroscopy. T₁ and T₂ relaxation times (in milliseconds) were determined for the major prostate metabolites and an internal TSP standard, and used to optimize the acquisition and repetition times (TRs) at 11.7 T. At 1°C, polyamines (PAs; T^1mean = 100 ± 13, T_2mean = 30.8 ± 7.4) and citrate (Cit; T_1mean = 237 ± 39, T_2mean = 68.1 ± 8.2) demonstrated the shortest relaxation times, while taurine (Tau; T_1mean = 636 ± 78, T _2mean = 331 ± 71) and choline (Cho; T_1mean = 608 ± 60, T_2mean = 393 ± 81) demonstrated the longest relaxation times. Millimolal metabolite concentrations were calculated for 60 postsurgical tissues using metabolite and TSP peak areas, and the mass of tissue and TSP. Phosphocholine plus glycerophosphocholine (PC+GPC), total choline (tCho), lactate (Lac), and alanine (Ala) concentrations were higher in prostate cancer ([PC+GPC]_mean = 9.34 ± 6.43, [tCho]_mean = 13.8 ± 7.4, [Lac]_mean = 69.8 ± 27.1, [Ala] _mean = 12.6 ± 6.8) than in healthy glandular ([PC+GPC] _mean = 3.55 ± 1.53, P < 0.01; [tCho]_mean = 7.06 ± 2.36, P < 0.01; [Lac]_mean = 46.5 ± 17.4, P < 0.01; [Ala]_mean = 8.63 ± 4.91, P = 0.051) and healthy stromal tissues ([PC+GPC]_mean = 4.34 ± 2.46, P < 0.01; [tCho] _mean = 7.04 ± 3.10, P < 0.01; [Lac]_mean = 45.1 ± 18.6, P < 0.01; [Ala]_mean = 6.80 ± 2.95, P < 0.01), while Cit and PA concentrations were significantly higher in healthy glandular tissues ([Cit]_mean = 43.1 ± 21.2, [PAs] _mean = 18.5 ± 15.6) than in healthy stromal ([Cit] _mean = 16.1 ± 5.6, P < 0.01; [PAs]_mean = 3.15 ± 1.81, P < 0.01) and prostate cancer tissues ([Cit]_mean = 19.6 ± 12.7, P < 0.01; [PAs]_mean = 5.28 ± 5.44, P < 0.01). Serial spectra acquired over 12 hr indicated that the degradation of Cho-containing metabolites was minimized by acquiring HR-MAS data at 1°C compared to 20°C.