Evidence that Food Intake Controls Diurnal Blood Pressure Rhythm in Mice

Blood pressure exhibits a 24‐hour rhythm and peaks in the beginning of the active period in both human and rodents. Previous studies suggested that timing of food intake plays pivotal roles in regulating many physiological processes, such as lipid metabolism, sleep‐wake cycle, immune responsiveness, and even blood pressure. However, whether blood pressure and kidney function is altered by changing feeding time remains largely unknown. The current study was designed to test the hypothesis that feeding during the inactive period (reverse feeding or RF) disrupts blood pressure and kidney function in mice. Male C57Bl/6J mice (12–16 weeks old, n=6) were placed in metabolic cages and had free access to food and water for 3 days, followed by a 6‐day RF with free access to water. Food and water intake, as well as urine output were monitored twice per day at the beginning of active and inactive periods (AP and IP, respectively). Blood pressure was recorded via telemetry transmitters. As expected, we found that mean arterial pressure (MAP) was significantly higher in AP compared to IP when mice were fed ad libitum (114 ± 1 vs. 96 ± 1 mmHg, respectively, p<0.01). However, RF led to an inversion of diurnal MAP (98 ± 5 vs. 112 ± 2 mmHg, p=0.02). Similar effects were observed in heart rate (ad libitum, 659 ± 12 vs. 548 ± 16 bpm, p=0.03; RF, 484 ± 48 vs. 613 ± 22 bpm, p=0.02). In contrast, RF did not alter diurnal rhythm in urine output (ad libitum, 1.0 ± 0.2 vs. 0.2 ± 0.1 ml/12hr, p<0.01; RF, 1.4 ± 0.1 vs. 0.7 ± 0.1 ml/12hr, p<0.01). However, diurnal rhythm in urinary sodium excretion was dampened after RF (ad libitum, 7.3 ± 0.8 vs. 1.0 ± 0.2 mEq/12hr, p<0.01; RF, 6.5 ± 0.8 vs. 4.5 ± 0.7 mEq/12hr, p=0.08). Similarly, diurnal rhythm in urinary potassium excretion was abolished (ad libitum, 7.0 ± 0.9 vs. 0.8 ± 0.2 mEq/12hr, p<0.01; RF, 4.8 ± 0.7 vs. 5.3 ± 0.7 mEq/12hr, p=0.97). We also measured urinary excretion of aldosterone by ELISA and found that its diurnal rhythm remained intact after RF (ad libitum, 990 ± 142 vs. 370 ± 38 pg/12hr, p=0.01; RF, 856 ± 181 vs. 204 ± 42 pg/12hr, p=0.01). These data suggest that RF inverts diurnal blood pressure rhythm and differentially modifies diurnal excretion of water and electrolytes in mice. Support or Funding Information Funded by an AHA pre‐doctoral fellowship (18PRE33990345) to DZ and NHLBI P01 HL136267 to DMP. We appreciate Drs. Celso and Elise Gomez‐Sanchez's help with the aldosterone assay. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .