Measurement of fractional whole-body gluconeogenesis in humans from blood samples using 2H nuclear magnetic resonance spectroscopy

Several problems limit quantification of gluconeogenesis. We applied in vitro H-2-nuclear magnetic resonance (NMR) spectroscopy to simultaneously measure H-2 in all glucose carbons for direct assessment of gluconeogenesis. This method was compared With H-2 measurement in carbons 5 and 2 using gas chromatography-mass spectrometry (hexamethylenetetramine [HMT]) and with in vivo C-13 magnetic resonance spectroscopy (MRS). After 14 h of fasting, and following (H2O)-H-2 ingestion, blood was obtained from nine healthy and seven type 2 diabetic subjects. Glucose was purified, acetylated, and analyzed for H-2 in carbons 1-6 with H-2-NMR. Using 5:2 ratios, gluconeogenesis increased (P < 0.05) over time and mean gluconeogenesis was lower in control subjects than in type 2 diabetic patients (63 +/- 3 vs. 75 +/- 2%, P < 0.01). C-13-MRS revealed higher hepatic glycogenolysis in control subjects (3.9 +/- 0.4 vs. 2.3 +/- 0.2 mumol (.) kg(-1) (.) min(-1)) yielding mean contribution of gluconeogenesis of 65 +/- 3 and 77 +/- 2% (P < 0.005). Measurement of gluconeogenesis by H-2-NMR correlated linearly with C-13-MRS (r = 0.758, P = 0.0007) and HMT (r = 0.759, P = 0.0007). In an additional protocol, H-2 enrichments demonstrated a fast decline of gluconeogenesis from similar to100 to similar to68% (P < 0.02) within 4 h of galactose infusion after 40-44 It of fasting. Thus, in vitro H-2-NMR offers an alternative approach to determine fractional gluconeogenesis in good agreement with standard methods and allows monitoring of rapid metabolic alterations.