Abstract
IntroductionIt seems that changes in expression of APJ apelin and vasopressin V1a and V1b receptors may significantly affect action and interactions of these two peptides, can play important role in cardiovascular regulation in different pathophysiological states such obesity. Apelin (APLN) is one of adipokines; its dysregulation has been implicated in obesity and type II diabetes. APLN its receptor APJ are co‐localized with vasopressin (AVP) in paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. It has been suggested that the apelinergic system may play an important role in the regulation of the vasopressinergic neurons activity. Thus, changes in expression of APJ and V1a and V1b receptors may significantly affect action and interactions of these two peptides, and contribute to cardiovascular dysregulation in different pathological states.PurposeThe aim of this project is to test the hypothesis the central dysregulation of APJ and V1a and V1b receptors may affect the apelin‐vasopressin interaction and contribute to changes in the hemodynamic parameters in obesity.MethodsSprague‐Dawley rats were on maintained on high fat diet (HFD) or a normal fat diet (NFD). Animals in experimental groups had intracerebroventricular (ICV) cannula implants for delivery of tested substances and abdominal aorta catheters for measuring mean arterial blood pressure (MABP) and heart rate (HR). Group I rats had ICV infusion of saline (NaCl) or/and V1a receptor antagonist (V1aRANT) or/and apelin‐13 (APLN‐13). Group II rats had ICV infusion of NaCl or/and APJ antagonist (F13A) or/and AVP. Brain tissue was collected from additional groups, for the analyses of mRNA expression and protein level of APJ, V1a, and V1b receptors. Consent was obtained from The Local Animal Research Ethics Committee (37/2015).ResultsInfusion of V1aRANT resulted in a significant decrease in MABP in both NFD and HFD; the decrease was greater in HFD. Infusion of APLN‐13 alone resulted in increased MABP only in NFD rats; this effect was absent when infusion of APLN‐13 was preceded by infusion of V1aRANT. Infusion of APLN‐13 preceded by infusion of V1aRANT resulted in decreased HR only in HFD rats. ICV infusion of F13A resulted in a significant decrease in MABP in both NFD and HFD rats; this decrease was greater in NFD rats. Infusion of AVP resulted in an increase in both MABP and HR only in HFD rats. There was no difference in hypothalamic mRNA expression of APJ and V1b receptors between the NFD and HFD rats. Expression of V1a receptor was significantly lower in HFD rats compared to NFD rats. The protein levels of APJ, V1a, and V1b receptors in the hypothalamus were significantly higher in HFD rats compared to NFD rats.ConclusionThese results provide evidence for the involvement of receptor V1a receptor in the regulation of blood pressure by centrally acting apelin. Furthermore, our studies suggest that the interaction of the apelinergic and vasopressinergic system may play an important role in central regulation of cardiovascular system.Support or Funding InformationFunding: Preludium; National Science Centre (UMO‐2016/21/N/NZ4/03758D).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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