Background: Consumption of a high fat diet (HFD) by rabbits results in rapidly increased blood pressure (BP), heart rate (HR) and renal sympathetic activity (RSNA). We determined how early these changes occurred and whether they were related to changes in cardiovascular and neural circadian rhythms.
Methods: Rabbits were meal-fed a 13.5% HFD and BP, HR and RSNA were measured daily via implanted telemeters in the home cage for 3 weeks and for 1 week after return to a normal diet.
Results: Baseline BP, HR and RSNA over 24h were 71±1mmHg, 205±4b/min and 7±1nu. Circadian rhythms were entrained to the feeding cycle, but not the light dark cycle, and values increased from the preprandial minimum to the postprandial maximum by 4±1mmHg, 51±6b/min and 1.6±0.6nu. Within 2 days of commencing a HFD, 24h BP, HR and RSNA had increased by 2%, 18% and 22% respectively, and the preprandial minimum was elevated by 79-127%. This inhibition was maintained for 3 weeks during the HFD and accounted for all of the hypertension and 50% of the RSNA activation. The circadian rhythms of BP and HR, but not RSNA, switched to being synchronised with the light-dark cycle and BP and HR were higher during the dark period for 3 weeks of HFD. Resumption of a normal diet for 1 week did not reverse the light cycle entrainment nor did it alter the inhibition of the BP preprandial dip but the HR pattern was progressively restored.
Conclusion: Hypertension induced by a HFD and mediated by rapid changes in sympathetic nerve activity is due to the immediate (within 2 days) and continued loss of preprandial dipping. This has implications for obese patients in whom non-dipping is associated with greatly increased risk of metabolic and cardiovascular disease.
Disclosures: None