Diabetes, Vol 36, Issue 10 1187-1194, Copyright © 1987 by American Diabetes Association
Effects of fasting on plasma glucose and prolonged tracer measurement of hepatic glucose output in NIDDM
H Glauber, P Wallace and G Brechtel
Department of Medicine, University of California, San Diego, La Jolla 92093.
We studied the measurement of hepatic glucose output (HGO) with prolonged
[3-3H]glucose infusion in 14 patients with non-insulin-dependent diabetes
mellitus (NIDDM). Over the course of 10.5 h, plasma glucose concentration
fell with fasting by one-third, from 234 +/- 21 to 152 +/- 12 mg/dl, and
HGO fell from 2.35 +/- 0.18 to 1.36 +/- 0.07 mg . kg-1 . min-1 (P less than
.001). In the basal state, HGO and glucose were significantly correlated (r
= 0.68, P = .03), and in individual patients, HGO and glucose were closely
correlated as both fell with fasting (mean r = 0.79, P less than .01).
Plasma [3-3H]glucose radioactivity approached a steady state only 5-6 h
after initiation of the primed continuous infusion, and a 20% overestimate
of HGO was demonstrated by not allowing sufficient time for tracer labeling
of the glucose pool. Assumption of steady-state instead of non-steady-state
kinetics in using Steele's equations to calculate glucose turnover resulted
in a 9-24% overestimate of HGO. Stimulation of glycogenolysis by glucagon
injection demonstrated no incorporation of [3-3H]glucose in hepatic
glycogen during the prolonged tracer infusion. In a separate study, plasma
glucose was maintained at fasting levels (207 +/- 17 mg/dl) for 8 h with
the glucose-clamp technique. Total glucose turnover rates remained constant
during this prolonged tracer infusion. However, HGO fell to 30% of the
basal value simply by maintaining fasting hyperglycemia in the presence of
basal insulin levels.(ABSTRACT TRUNCATED AT 250 WORDS)