Utilization of glycogen but not plasma glucose is reduced in
individuals with niddm during mild intensity exercise.
Colberg, Sheri R., James M. Hagberg, Steve D. McCole, Joseph M. Zmuda,
Paul D. Thompson, and David E. Kelley.
The Department of Medicine, University of Pittsburgh School of
Medicine and Department of Veterans Affairs Medical Center,
Pittsburgh, Pennsylvania
APStracts 3:0250A, 1996.
To test the hypothesis that substrate utilization during mild
intensity exercise differs in NIDDM compared to nondiabetic subjects,
7 lean healthy subjects (L), 7 obese healthy subjects (O), and 7
individuals with NIDDM were studied during 40 min of mild intensity
cycling (40% of VO2 peak). NIDDM subjects had hyperglycemia
(10.7+1.7mM), and all of the volunteers were untrained (mean VO2 peak
of 23+2 ml/kg-min). Systemic utilization (uptake) of plasma glucose
(G Rd) and plasma FFA were determined using isotope dilution methods
with 3-[3H]-glucose and 9,10-[3H]-palmitate, respectively. Gas
exchange was measured to determine rates of carbohydrate (CHO Ox) and
lipid oxidation (L Ox). During exercise, when CHO Ox was greater than
G Rd, the net oxidation of glycogen was calculated as the difference:
CHO Ox -G Rd. During mild-intensity cycling, RER was similar across
groups (0.87+0.02, 0.85+0.02 and 0.86+0.01; in L, O and NIDDM
respectively), as was CHO Ox (6.4+0.9, 5.4+1.0, and 6.0+0.6 mg/kg
-min), CHO Ox accounted for half of total energy expenditure during
exercise (56+7, 49+6 and 51+3 percent). G Rd increased during
exercise and was greatest in subjects with NIDDM (3.0+0.2, 2.9+0.2
and 4.5+0.4 mg/kg-min in L, O and NIDDM, respectively, p<0.05),
yet G Rd was less than CHO Ox during exercise, indicating net
oxidation of glycogen. Glycogen oxidation was greater in L and O than
in NIDDM subjects (3.4+1.0, 2.5+0.9, and 1.7+0.8 mg/kg-min;
p<0.05). Palmitate utilization and L Ox during exercise did not
differ across groups. In summary, during mild intensity exercise,
untrained NIDDM subjects have rates of carbohydrate and lipid
oxidation which are equivalent to untrained nondiabetic subjects,
though at similar energy expenditure, NIDDM subjects have an
increased utilization of plasma glucose and a decreased oxidation of
muscle glycogen.
Received 15 December 1995; accepted in final form 7 May 1996.
APS Manuscript Number A1313-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96