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Food Availability Regulates Circadian Blood Pressure Rhythms in Rats
Author(s) -
Rhoads Megan K.,
Jin Chunhua,
Pollock David M.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.06579
Subject(s) - circadian rhythm , blood pressure , rhythm , clock , circadian clock , period (music) , medicine , endocrinology , food intake , chronobiology , biology , physiology , zoology , physics , acoustics
Blood pressure (BP) changes throughout the day and follows a circadian rhythm that is believed to be controlled by so‐called clock genes. Loss of BP reductions during the sleep period are associated with increased risk of cardiovascular and renal disease. Recent human studies suggest that timing of food intake can affect BP. Therefore, the aim of our study was to determine if food availability affects blood pressure rhythms in the absence of light cues in rats with functional and dysfunctional molecular clocks. Individually housed Bmal1KO rats (n=4) and littermate controls (n=6) were implanted with DSI HD‐S10 telemetry transmitters at 10 weeks of age. Data were collected for 2 minutes every 10 minutes at 1000 samples/second. Animals were given ad lib access to food and water in a 12:12 light/dark (LD) cycle for 2 weeks to establish normal BP rhythms. After 2 weeks, animals were placed in constant darkness (DD) with ad lib food and water for 4 weeks. Food availability was then restricted to 12 hours per day (CT 14.5 to CT 2.5, CT=clock time) under DD conditions (DD‐TRF, TRF=time restricted feeding) for 1 week. Cosinor analysis was performed to determine period, amplitude and phase of activity and systolic blood pressure (SBP) rhythms. In LD conditions, period, amplitude, and phase of SBP and activity were similar between Bmal1KO and control rats. After 4 weeks of DD, control rats had SBP rhythms that peaked at CT 19.9±0.3 hours while Bmal1KO rats had SBP rhythms that peaked at CT 12.0±1.8 hours (p<0.05) indicating a significant change in acrophase. SBP amplitude and period were similar in both groups under DD conditions. For locomotor activity, period was shortened in Bmal1KO rats in DD compared to control rats (control: 24.1±0.01 hours vs. Bmal1‐KO: 23.8±0.08 hours). In DD‐TRF, control rats have SBP rhythms that peak at CT 20.69± 0.44 hours, when food was available. However, SBP rhythms of Bmal1 rats peaked at CT 13.94±3.4 hours. SBP amplitude, period, and activity period were similar between groups during DD‐TRF. These results suggest that food availability and the molecular clock contribute to the timing of systolic blood pressure rhythms in rats.