Abstract
Multifunctional peptide oxytocin currently undergoes intensive research due to its
proposed anti-obesity properties. Until now, little is known about regulation of oxytocin
receptor in metabolically active tissues in obesity. The aim of the present study
was to measure expression of oxytocin receptor upon obese phenotype with respect to
the variety among adipose tissue and skeletal muscles with distinct anatomical localisation.
Total homogenates were prepared from epididymal, retroperitoneal and inguinal adipose
tissues as well as quadriceps and soleus muscle from lean and obese Zucker rats. Oxytocin
receptor protein was determined by immunoblot. Interestingly, elevated oxytocin receptor
was observed in epididymal adipose tissue of obese rats in contrast to its downregulation
in subcutaneous and no change in retroperitoneal fat. In lean animals, oxytocin receptor
protein was expressed at similar levels in all adipose depots. This uniformity was
not observed in the case of skeletal muscle in which fibre type composition seems
to be determinant of oxytocin receptor expression. Quadriceps muscle with the predominance
of glycolytic fibres exhibits higher oxytocin receptor expression than almost exclusively
oxidative soleus muscle. Oxytocin receptor protein levels were decreased in both skeletal
muscles analysed upon obese phenotype. The present work demonstrates that even under
identical endocrine circumstances, oxytocin receptor is differentially regulated in
adipose tissue of obese rats depending on fat depot localisation. These results also
imply which tissues may be preferentially targeted by oxytocin treatment in metabolic
disease.
Key words
obesity - oxytocin - metabolic tissues
