Related Experiment Video
Updated: Apr 16, 2026
Measurement of Insulin- and Contraction-Stimulated Glucose Uptake in Isolated and Incubated Mature Skeletal Muscle from Mice
Published on: May 16, 2021
Glucose uptake during contraction in isolated skeletal muscles from neuronal nitric oxide synthase μ knockout mice
Yet Hoi Hong1, Tony Frugier2, Xinmei Zhang3
1College of Health and Biomedicine and Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia; Department of Physiology, Faculty of Medicine, University of Malaya, Malaysia;
Abstract:
Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation is observed in individuals with Type 2 diabetes compared with healthy individuals. Therefore, NO appears to play an important role in mediating muscle glucose uptake during contraction. In this study, we investigated the involvement of neuronal NOSμ (nNOSμ), the main NOS isoform activated during contraction, on skeletal muscle glucose uptake during ex vivo contraction. Extensor digitorum longus muscles were isolated from nNOSμ(-/-) and nNOSμ(+/+) mice. Muscles were contracted ex vivo in a temperature-controlled (30°C) organ bath with or without the presence of the NOS inhibitor N(G)-monomethyl-l-arginine (L-NMMA) and the NOS substrate L-arginine. Glucose uptake was determined by radioactive tracers. Skeletal muscle glucose uptake increased approximately fourfold during contraction in muscles from both nNOSμ(-/-) and nNOSμ(+/+) mice. L-NMMA significantly attenuated the increase in muscle glucose uptake during contraction in both genotypes. This attenuation was reversed by L-arginine, suggesting that L-NMMA attenuated the increase in muscle glucose uptake during contraction by inhibiting NOS and not via a nonspecific effect of the inhibitor. Low levels of NOS activity (~4%) were detected in muscles from nNOSμ(-/-) mice, and there was no evidence of compensation from other NOS isoform or AMP-activated protein kinase which is also involved in mediating muscle glucose uptake during contraction. These results indicate that NO regulates skeletal muscle glucose uptake during ex vivo contraction independently of nNOSμ.
Insights
Nitric oxide (NO) is crucial for muscle glucose uptake during exercise. This study found that NO, not the specific neuronal NOSμ isoform, regulates this process in skeletal muscle contraction.
Area of Science:
- Exercise Physiology
- Molecular Biology
- Metabolic Regulation
Background:
- Nitric oxide synthase (NOS) inhibition reduces skeletal muscle glucose uptake during exercise.
- This effect is more pronounced in individuals with Type 2 diabetes.
- Neuronal NOSμ (nNOSμ) is the primary NOS isoform activated during muscle contraction.
Purpose of the Study:
- To investigate the role of nNOSμ in skeletal muscle glucose uptake during ex vivo contraction.
- To determine if nNOSμ is essential for nitric oxide-mediated glucose uptake during muscle activity.
Main Methods:
- Isolated extensor digitorum longus muscles from nNOSμ knockout and wild-type mice were used.
- Muscles were contracted ex vivo in an organ bath with or without NOS inhibitor (L-NMMA) and L-arginine.
- Radioactive tracers measured glucose uptake.
Main Results:
- Skeletal muscle glucose uptake increased fourfold during contraction in both genotypes.
- L-NMMA significantly attenuated this increase, an effect reversed by L-arginine.
- nNOSμ knockout muscles showed minimal residual NOS activity without compensatory mechanisms.
Conclusions:
- Nitric oxide regulates skeletal muscle glucose uptake during contraction independently of the nNOSμ isoform.
- These findings highlight a broader role for NO in muscle metabolism during exercise.
