title: Specific role of dietary fat in modifying cardiovascular and locomotor activity 24-h rhythms.
abstract: Meal-fed conscious rabbits normally exhibit postprandial elevation in blood pressure, heart rate (HR) and locomotor activity, which is abolished by consumption of a high-fat diet (HFD). Here, we assessed whether the cardiovascular changes are attributable to the increased caloric intake due to greater fat content or to hyperphagia. Rabbits were meal-fed during the baseline period then maintained on either an ad libitum normal fat diet (NFD) or ad libitum HFD for 2 weeks. Blood pressure, HR and locomotor activity were measured daily by radio-telemetry alongside food intake and body weight. Caloric intake in rabbits given a NFD ad libitum rose 50% from baseline but there were no changes in cardiovascular parameters. By contrast, HR increased by 10% on the first day of the ad libitum HFD (p < 0.001) prior to any change in body weight while blood pressure increased 7% after 4 d (p < 0.01) and remained elevated. Baseline 24-h patterns of blood pressure and HR were closely associated with mealtime, characterised by afternoon peaks and morning troughs. When the NFD was changed from meal-fed to ad libitum, blood pressure and HR did not change but afternoon activity levels decreased (p < 0.05). By contrast, after 13 d ad libitum HFD, morning HR, blood pressure and activity increased by 20%, 8% and 71%, respectively. Increased caloric intake specifically from fat, but not as a result of hyperphagia, appears to directly modulate cardiovascular homeostasis and circadian patterns, independent of white adipose tissue accumulation.
authors.affiliation: Neuropharmacology Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, Victoria , Australia .
authors.forename: Benjamin
authors.initials: B
authors.lastname: Barzel
authors.forename: Kyungjoon
authors.initials: K
authors.lastname: Lim
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Burke
authors.forename: James A
authors.initials: JA
authors.lastname: Armitage
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Head
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D002940:Circadian Rhythm / Q000502:physiology*; D004041:Dietary Fats / Q000378:metabolism*; D004435:Eating / Q000502:physiology; D002149:Energy Intake / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000503:physiopathology*; D011817:Rabbits
chemical_list: D004041:Dietary Fats
keywords: 24-h rhythm; blood pressure; heart rate; high-fat diet; obesity; rabbits