Figure 1

Natural abundance ¹³C NMR typical spectra of isolated livers from rats in different nutritional conditions. Livers were perfused and isolated from a rat (A) fed ad libitum, (B) starved for 48 hr, (C) 6^th hour post force-feeding with glucose 18.2 mg/g body weight, following 48 hr of fasting and (D) 6^th hour post force-feeding with (glucose 14.0 mg + butyrate 1.90 mg)/g body weight, following 48 hr of fasting. An external silicone reference gives a resonance at 0 ppm. Peak assignments: (a and h) fatty acids chains; (b) C-1 glycogen; (c) C-1α and C-1β glucose (mainly exogenous glucose of the perfusate); (d) glucose and glycogen (C-3β, C-5β glucose, glycogen; C-2 glucose; C-3α glucose; C-2, C-5α glucose, C-5 glycogen; C-4αβ glucose, glycogen); (e) C-6 glucose, glycogen; (f) choline; (g) ethanolamine. The chemical shift scale δ is given in parts per million (ppm) according to: chemical shift (Hz) = δ (ppm) × A(MHz), A being the frequency of the spectrometer. The unit ppm is used owing to the order value (10^-6) of a constant characterizing the chemical nature of the nucleus. This scale allows an easy comparison between spectra obtained in spectrometers operating at different magnetic fields.