Interrelationships between muscle morphology, insulin action and
adiposity.
Kriketos, A. D., D. A. Pan, S. Lillioja, G. J. Cooney, L. A. Baur, M.
R. Milner, J. R. Sutton, A. B. Jenkins, C. Bogardus, and L. H.
Storlien.
Department of Endocrinology, Royal Prince Alfred Hospital, Sydney
NSW 2050, Departments of Medicine and Biomedical Science, University
of Sydney, Sydney NSW 2006 and Department of Biomedical Science,
University of Wollongong, Wollongong NSW 2522, Australia, and
Clinical Diabetes and Nutrition Section, NIDDK NIH, Phoenix, Arizona
85016, USA
APStracts 2:0349R, 1995.
There is evidence that insulin resistance and obesity are associated
with relative increases in the proportion of glycolytic, Type 2b
muscle fibers and decreases in the proportion of oxidative, Type 1
fibers. Futhermore, insulin resistance and obesity are associated
with the fatty acid (FA) profile of structural membrane lipids. The
present study was undertaken to define the interrelationships between
muscle fiber type and oxidative capacity, muscle membrane FA
composition and insulin action and obesity. Muscle morphology,
insulin action and body fat content were measured in 48 male, non
-diabetic Pima Indians. Percent body fat (determined by
hydrodensitometry; pFAT) correlated negatively with the percentage
(%) of Type 1 fibers (r = -0.44, p = 0.002) and positively with the %
of Type 2b fibers (r = 0.40, p = 0.005). Consistent with this, pFAT
was also significantly related to the oxidative capacity of muscle as
assessed by NADH staining (r = -0.47, p = 0.0007) and citrate
synthase (CS) activity (r = -0.43, p = 0.008). Insulin action was
correlated with oxidative capacity (CS; r = 0.41, p = 0.01) and
weakly with % of Type 2b fibers (r = -0.29, p = 0.05). In addition,
relationships were shown between muscle fiber type and FA composition
(eg. % of Type 1 fibers related to n-3 FA; r = 0.37, p = 0.01). Thus
leaness and insulin sensitivity are associated with increased
oxidative capacity and unsaturation of membranes in skeletal muscle.
Present studies provide support for the hypothesis that muscle
oxidative capacity and fiber type may play either a genetically
determined or environmentally modified role in the development of
obesity and insulin resistance.
Received 21 August 1995; accepted in final form 11 December 1995.
APS Manuscript Number R520-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95