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Interrelationships between muscle morphology, insulin action, and adiposity
A D Kriketos1, D A Pan, S Lillioja
1Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia.
The American Journal of Physiology
|June 1, 1996
Summary
Leaner individuals with better insulin sensitivity have more oxidative muscle fibers and unsaturated membranes. This suggests muscle fiber type and oxidative capacity play a role in obesity and insulin resistance.
Area of Science:
- Metabolic Health
- Skeletal Muscle Physiology
- Body Composition
Background:
- Insulin resistance and obesity are linked to shifts in muscle fiber types, favoring glycolytic over oxidative fibers.
- These metabolic conditions also correlate with alterations in muscle membrane fatty acid (FA) profiles.
Purpose of the Study:
- To investigate the interrelationships between skeletal muscle fiber type, oxidative capacity, muscle membrane FA composition, insulin action, and obesity.
- To define the role of muscle characteristics in the development of insulin resistance and obesity.
Main Methods:
- Muscle morphology, insulin action, and body fat percentage (pFAT) were assessed in 48 nondiabetic Pima Indian males.
- Muscle oxidative capacity was evaluated using NADH staining and citrate synthase (CS) activity.
- Muscle membrane FA composition was analyzed in relation to fiber type.
Main Results:
- Higher body fat percentage was associated with a greater proportion of type IIb fibers and a lower proportion of type I fibers.
- Increased body fat correlated with reduced muscle oxidative capacity (NADH, CS activity).
- Insulin sensitivity was positively correlated with muscle oxidative capacity (CS activity).
- Muscle fiber type composition was linked to specific fatty acid profiles, such as type I fibers and n-3 FA.
Conclusions:
- Leanness and insulin sensitivity are associated with enhanced skeletal muscle oxidative capacity and greater membrane unsaturation.
- Muscle oxidative capacity and fiber type may influence the development of obesity and insulin resistance, potentially through genetic or environmental factors.