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Open Access Research

Effect of nitric oxide synthase inhibition on the exchange of glucose and fatty acids in human skeletal muscle

Ilkka Heinonen12*, Bengt Saltin6, Jukka Kemppainen13, Pirjo Nuutila14, Juhani Knuuti1, Kari Kalliokoski1 and Ylva Hellsten5

Author Affiliations

1 Turku PET Centre, PO Box 52, FI-20521, Turku, Finland

2 Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland

3 Department of Clinical Physiology and Nuclear Medicine, University of Turku, Turku, Finland

4 Department of Medicine, Turku University Hospital, University of Turku, Turku, Finland

5 Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark

6 Copenhagen Muscle Research Center, University of Copenhagen, Copenhagen, Denmark

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Nutrition & Metabolism 2013, 10:43  doi:10.1186/1743-7075-10-43

Published: 18 June 2013

Abstract

Background

The role of nitric oxide in controlling substrate metabolism in humans is incompletely understood.

Methods

The present study examined the effect of nitric oxide blockade on glucose uptake, and free fatty acid and lactate exchange in skeletal muscle of eight healthy young males. Exchange was determined by measurements of muscle perfusion by positron emission tomography and analysis of arterial and femoral venous plasma concentrations of glucose, fatty acids and lactate. The measurements were performed at rest and during exercise without (control) and with blockade of nitric oxide synthase (NOS) with NG-monomethyl-l-arginine (L-NMMA).

Results

Glucose uptake at rest was 0.40 ± 0.21 μmol/100 g/min and increased to 3.71 ± 2.53 μmol/100 g/min by acute one leg low intensity exercise (p < 0.01). Prior inhibition of NOS by L-NMMA did not affect glucose uptake, at rest or during exercise (0.40 ± 0.26 and 4.74 ± 2.69 μmol/100 g/min, respectively). In the control trial, there was a small release of free fatty acids from the limb at rest (−0.05 ± 0.09 μmol/100 g/min), whereas during inhibition of NOS, there was a small uptake of fatty acids (0.04 ± 0.05 μmol/100 g/min, p < 0.05). During exercise fatty acid uptake was increased to (0.89 ± 1.07 μmol/100 g/min), and there was a non-significant trend (p = 0.10) for an increased FFA uptake with NOS inhibition 1.23 ± 1.48 μmol/100 g/min) compared to the control condition. Arterial concentrations of all substrates and exchange of lactate over the limb at rest and during exercise remained unaltered during the two conditions.

Conclusion

In conclusion, inhibition of nitric oxide synthesis does not alter muscle glucose uptake during low intensity exercise, but affects free fatty acid exchange especially at rest, and may thus be involved in the modulation of energy metabolism in the human skeletal muscle.

Keywords:
Nitric oxide; Metabolism; Energy substrates; Humans