Sex difference in triglyceride/fatty acid substrate cycling of rat adipose tissue: indirect regulation by androgens.

Male Sprague-Dawley rats displayed significantly higher rates of triglyceride/fatty acid (TG/FFA) substrate cycling in subcutaneous, perigenital, and mesenteric white adipose tissue, compared to females. To investigate possible regulation via androgens and estrogens, male rats were treated with the androgen antagonist, cyproterone acetate (10 mg daily in subcutaneous injections), or estradiol polyphosphate (0.3 mg intramuscularly, given as a single dose). Estradiol treatment did not affect TG/FFA cycling. Treatment with cyproterone acetate significantly decreased TG/FFA cycling in perigenital (epididymal) tissue. This effect could however largely be ascribed to concomitant inhibition of food intake by cyproterone acetate. The effects of cyproterone acetate on the two axes of TG/FFA cycling (lipolysis and re-esterification) were further studied in vitro. Norepinephrine-stimulated glycerol release from perigenital adipocytes was inhibited, whereas activities of esterification enzymes (GPAT and PPH) was essentially unaffected. We conclude that androgens seem to affect TG/FFA cycling indirectly via the lipolytic axis.