Dissociation between adipose nitric oxide synthase expression and tissue metabolism

Area of Science:

• Metabolic research
• Obesity research
• Physiology

Background:

• Nitric oxide synthase (NOS) expression is elevated in the adipose tissue of obese individuals.
• The functional significance of this increased NOS expression in obesity remains unclear.

Purpose of the Study:

• To investigate adipose tissue metabolism differences between obese men with varying levels of endothelial NOS (eNOS) or inducible NOS (iNOS) expression.
• To compare lipolysis and tissue perfusion in relation to NOS expression in obese versus lean men.

Main Methods:

• Prospective study involving 14 obese and 8 lean healthy men.
• Microdialysis was used in abdominal subcutaneous adipose tissue and vastus lateralis.
• Perfusion with nitric oxide synthase inhibitors (L-NAME/D-NAME) and incremental isoproterenol concentrations.

Main Results:

• Adipose tissue glycerol release (lipolysis) and perfusion were similar in obese men with high or low eNOS/iNOS expression.
• Nitric oxide inhibition did not affect lipolysis in obese subjects but augmented it in lean subjects.
• Lean men showed a left-shifted dose-response curve for isoproterenol-stimulated lipolysis compared to obese men.

Conclusions:

• Variations in adipose tissue eNOS and iNOS mRNA expression have minimal impact on lipolysis and perfusion.
• The reduced resting lipolysis observed in obese individuals is not attributable to a tonic nitric oxide effect.