Rapid activation of renal sympathetic activity with onset of high fat diet in rabbits

Abstract

Purpose Short term consumption of a high fat diet (HFD) induces elevated blood pressure (BP), heart rate and renal sympathetic nerve activity (RSNA) which may be the basis for the development of long term obesity related hypertension. In the present study we determined the rapidity of such changes and whether this involved disturbance to other stimuli including airjet stress, hypoxia and baroreflexes. Methods New Zealand White rabbits implanted with telemetry devices for BP and RSNA were placed on a normal or 13.5% HFD. Reflexes and stress responses were examined weekly during the 3-week diet. Results After 1 week on the HFD, rabbits demonstrated 4%, 8% and 30% greater BP, heart rate and RSNA respectively (P < 0.05). By the end of 3 weeks of HFD, BP, heart rate and RSNA were elevated by 10%, 5% and 82% (n=9). Baroreflex curve analysis showed that the increase was independent of baroreceptor inputs and similar to the effects of acute stress. Indeed acute airjet stress induced lesser sympathetic responses suggesting that the pathway was already activated. The sympatho-excitatory responses to hypoxia were similar in the HFD and normal diet groups over the 3-week period of diet. Conclusion Together these results suggest that sympathetic activation occurs within several days of a high fat diet and may be associated with a chronic activation of forebrain pathways mediating the sympathetic responses to acute emotional stress.