Glucose production, recycling, and gluconeogenesis in normals and diabetics: a mass isotopomer [U-13C]glucose study.
Eight normal controls and nine non-insulin-dependent diabetes mellitus diabetics were, after an overnight fast, infused for 3 h with [6-3H]- and with [U-13C]glucose with six 13C carbons at rates from 0.03 to 0.15 mg.kg-1.min-1. Plasma glucose and lactate were assayed by gas chromatography-mass spectroscopy. Several parameters of glucose metabolism were calculated from the mass isotopomer distribution. Glucose production (GP) determined with [6-3H]- and [U-13C]glucose agreed closely. GP was 1.9 +/- 0.16 (range 1.3-2.5) mg.kg-1.min-1 in controls and 2.8 +/- 0.29 (1.7-4.5) mg.kg-1.min-1 in diabetics (P < 0.05). The correlation in diabetes between plasma glucose and GP (r = 0.911, P < 0.01) was close. Recycling of carbon (8 vs 7%) dilution by unlabeled carbon (2- vs 2.3-fold), and dilution via the tricarboxylic acid cycle (1.5-fold) were similar in controls and diabetics. Gluconeogenesis was 0.90 +/- 0.08 (0.5-1.3) mg.kg-1.min-1 in controls and 1.30 +/- 0.13 (0.8-1.9) mg.kg-1.min-1 in diabetics (P < 0.05). Gluconeogenesis contributions to GP were 46.6 +/- 4.0% (26-61%) in the controls and 48.8 +/- 5.7% (32-83%) in diabetics. We show that, using [U-13C]glucose infusion of 2-5% of glucose turnover (0.03-0.10 mg.kg-1.min-1), a large number of parameters of glucose metabolism may be determined in humans.
Tayek
J A
JA
Department of Internal Medicine, Harbor-University of California, Los Angeles Medical Center, Torrance 90509, USA.
Katz
J
J
D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D005943:Gluconeogenesis; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D019344:Lactic Acid / Q000096:biosynthesis; D008297:Male; D008875:Middle Aged; D019289:Pyruvic Acid / Q000378:metabolism; D012016:Reference Values
D019344:Lactic Acid; D019289:Pyruvic Acid; D005947:Glucose