Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C061

Oral Communications

Can the modulation of adenosine and/or ATP signaling in the carotid body be used to treat type 2 diabetes?

J. F. Sacramento1, C. S. Prego1, S. V. Conde1

1. CEDOC, NOVA Medical School|Faculdade Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal.

Our group have described that carotid body (CB) is involved in the genesis and maintenance of insulin resistance and glucose intolerance, since carotid sinus nerve (CSN) resection prevents and reverses these pathological features in prediabetes animal models (1,2). We have also showed that CB is overactivated in prediabetes animal models (1,3), which agrees with the observed increase in CSN basal activity in high-fat (HF) rats (3). Knowing that adenosine and ATP are key mediators in the CB, mediating the CSN hypoxic response (4), the aim of this work was to investigate the role of adenosine and ATP in the CB/CSN overactivity induced by HF diet. Two groups of 8-9 weeks male Wistar rats were used: control (chow diet) and the HF group (60% lipid-rich diet, 21 days). After this period, insulin sensitivity was evaluated. To perform the ex vivo recordings of the CSN activity, animals were anesthetized with pentobarbital sodium (60 mg/kg ip) and the carotid bifurcation was removed and the CB-CSN was dissected and transferred to a recording chamber superfused (37οC) with Tyrode bicarbonate equilibrated with normoxia (20%O2+5%CO2). CSN activity was identified and confirmed by its response to hypoxia (0%O2). The effect of ZM241385 (300nM; A2 antagonist), SCH58261 (20nM; selective A2A antagonist), suramin (50μM; P2 receptor antagonist) and AF-353 (0.3 and 1μM; P2X3 antagonist) on the CSN activity in normoxia and hypoxia (0 and 5%O2)-evoked CSN action potentials was evaluated. Animals were killed by an intracardiac overdose of pentobarbital sodium (60mg/kg i.p.). HF diet increased basal CSN activity (CTL=1.56±0.24Hz/s; HF=3.11±0.55Hz/s; p<0.05). In control rats basal CSN discharge did not change with adenosine antagonists. However in HF animals, CSN basal activity decreased by 34.85 (p<0.05) and 48.21% (p<0.05) with SCH58261 and ZM241385, respectively. Also, suramin and AF-353 did not change basal CSN activity. ZM241385 decreased the response to hypoxia (0%O2) by 43.84 (p<0.01) and 52.10% (p<0.05), in both control and HF group. Suramin decreased the chemosensory response to hypoxia (0% O2) by 59.42 (p<0.01) and 59.72% (p<0.05), in both control and HF group, respectively. ZM241385 application plus suramin decreased the CSN response to hypoxia (0%O2) by 80.57 (p<0.001) and 72.73% (p<0.05), in both control and HF group. As expected, AF-353 showed a higher effect in decreasing CSN chemosensory in response to 0%O2 than to 5%O2, an effect that was dose dependent [0%O2: 0.3μM decreased 71.07 (p<0.01) and 1μM (p<0.001) decreased 89.75%; 5%O2: 0.3μM decreased 57.98 (p<0.01) and 1μM decreased 72.92% (p<0.01)]. We conclude that adenosine, more than ATP, is involved in the CSN overactivation induced by the HF diet, mainly via A2A receptors. Additionally, in control animals ATP contribute more than adenosine to generate CSN activity in intense hypoxias. Our results suggest that the modulation of adenosine signaling in the CB can be a therapeutic target for type 2 diabetes.

Where applicable, experiments conform with Society ethical requirements