Topspin software package version 3

All spectra were recorded using a Bruker AMX‐600 NMR (Bruker, Rheinstetten, Germany) spectrometer that was operated at a 600.13 MHz ¹H resonance frequency. Quality control tests were performed at the beginning of every measurement day. A representative sample was used for NMR probe tuning and matching, determination of the transmitter offset value for water‐pulse pre‐saturation, and 90 pulse adjustments. Each sample was locked and shimmed automatically; receiver gain was set to 90.5 and temperature to 310 K for all experiments. All spectra were acquired and performed using TopSpin software package version 3.0 (Bruker Biospin, Rheinstetten, Germany). The NMR spectroscopy of urine samples was collected with a pre‐saturation ¹H ‐ NOESY pulse sequence (equation as relaxation delay ‐90° ‐ t1‐90° ‐ tm‐90° acquisition, where the relaxation delay was 2 s, t1 was 4 μs, and tm was 100 ms). A total of 128 scans with a spectral width of 5 kHz was collected for all NMR spectra. All the signals were zero filled to 32 k before Fourier transformation. The NMR spectroscopy of serum samples was collected with Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence (equation as relaxation delay ‐90°‐(t‐180°‐t) n ‐ acquisition, where the relaxation delay was 2 s, t was 400 μs).

The proton NMR spectra of the plasma were recorded at 300K on a Bruker Avance II 600 MHz spectrometer (Bruker Biospin, Rheinstetten, Germany) operating at a ¹H frequency of 600.13 MHz and equipped with a broadband-observe probe.
A water-presaturated Carr-Purell-Meiboom-Gill pulse sequence (recycle delay −90^o-(τ-180^o-τ)_n- acquisition) was employed to attenuate the NMR signals from macromolecules. A spin-spin relaxation delay (2nτ) of 76.8 ms and a spin-echo delay τ of 400 μs were used. Typically, the 90^o pulse was set to 13.7 μs, and 32 transients were collected in 49,178 data points for each spectrum using a spectral width of 9590 Hz and an acquisition time of 2.56 seconds.^{[30 ]} After the Fourier transformation, phase correction and baseline correction were performed using the TopSpin software package, version 3.0 (Bruker Biospin, Rheinstetten, Germany). The ¹H chemical shifts referred to the TMSP peak at δ 0.00.
The corrected NMR spectra, corresponding to the chemical shift range of δ 0.8 to 9.0, were imported into AMIX 3.9.5 (Bruker Biospin). All of the spectra were reduced into integral regions of equal lengths of 0.002 ppm. The region δ 4.20 to 5.20 that contained the resonance from residual water and the region of δ 5.50 to 6.00 that contained the resonance from urea were removed to avoid any contributions of H₂O and urea to intergroup differentiations.