Additional evidence that transaldolase exchange, isotope discrimination during the triose-isomerase reaction, or both occur in humans: effects of type 2 diabetes.
OBJECTIVE
To determine whether deuterium enrichment on carbons 5 and 3 (C5/C3) in plasma glucose is influenced by processes other than gluconeogenesis and, if so, whether these processes are altered by type 2 diabetes.


METHODS
In this study, 10 obese diabetic and 10 obese nondiabetic subjects were infused intravenously with [3,5-(2)H(2)] galactose enriched at a C5-to-C3 ratio of 1.0 as well as the enrichment of deuterium on C5 and C3 of plasma glucose, measured with nuclear magnetic resonance using the acetaminophen glucuronide method.


RESULTS
The ratio of deuterium enrichment on C5 and C3 of glucose was <1 (P < 0.001) in all of the diabetic and nondiabetic subjects, resulting in a means +/- SE C5-to-C3 ratio that did not differ between groups (0.81 +/- 0.01 vs. 0.79 +/- 0.01, respectively).


CONCLUSIONS
That the C5-to-C3 glucose ratio is <1 indicates that transaldolase exchange, selective retention of deuterium at the level of the triose-isomerase reaction, or both occur in humans. This also indicates that the net effect of these processes on the C5-to-C3 ratio is the same in people with and without type 2 diabetes. The possible effects of transaldolase exchange or selective retention of deuterium (or tritium) at the level of the triose-isomerase reaction on tracee labeling and tracer metabolism should be considered when the deuterated water method is used to measure gluconeogenesis or [3-(3)H] glucose is used to measure glucose turnover in humans.
Division of Endocrinology, Diabetes, Metabolism & Nutrition, Mayo Clinic College of Medicine, Rochester, MN, USA.
Rita
R
Basu
Visvanthan
V
Chandramouli
William
W
Schumann
Ananda
A
Basu
Bernard R
BR
Landau
Robert A
RA
Rizza
D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D003903:Deuterium / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications / Q000201:enzymology*; D005690:Galactose / Q000378:metabolism; D005934:Glucagon / Q000097:blood; D005943:Gluconeogenesis; D006801:Humans; D007328:Insulin / Q000097:blood; D007553:Isotope Labeling / Q000379:methods; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000201:enzymology*; D012016:Reference Values; D014153:Transaldolase / Q000378:metabolism*; D014305:Triose-Phosphate Isomerase / Q000378:metabolism*
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D005934:Glucagon; D003903:Deuterium; D014153:Transaldolase; D014305:Triose-Phosphate Isomerase; D005690:Galactose