Blood Pressure Circadian Rhythm and Pregnancy Outcomes in High-Fat Diet-Fed Dahl Salt-Sensitive Rat

Maternal obesity is a major risk factor for hypertensive disorders of pregnancy (HDP), a leading cause of maternal and fetal mortality worldwide. Disrupted blood pressure (BP) circadian rhythm may occur in association with obesity and HDP. Yet, the interplay between maternal adiposity and BP rhythm disturbances remains unclear. The high-fat-diet-fed (HFD) Dahl Salt-Sensitive rat (Dahl SS) has been established as a model of adiposity-induced hypertension. However, pregnancy hemodynamics and outcomes in HFD Dahl SS rats have not been investigated. We aimed to elucidate the 24h BP profile and pregnancy outcomes of HFD Dahl SS females. We hypothesized that hypertension would be exacerbated in HFD Dahl SS during pregnancy, along with loss of BP circadian rhythm, fetal growth restriction and perinatal death. Virgin Dahl SS females from Charles River Laboratories were assigned to control diet (CD, 0.3% NaCl, 10% kcal fat) or HFD (0.3% NaCl, 60% kcal fat) at 3 weeks of age (Research Diets, Inc). At 11 weeks of age, radiotelemetry transmitters were implanted (PhysioTel™ HD-S10, Data Sciences International), and systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP) were recorded every 10 min throughout the study (n=5/group). Day of copulation was defined as gestational day (GD) 0. Litter sizes and pup birth weights were assessed on postnatal day (PD) 0. Fixed-effects model with post-hoc Tukey’s tests were used for BP analyses and Student’s t tests were used for litter outcomes (GraphPad Prism 10.3.1). Chi2 periodograms were used to assess presence of MAP circadian rhythms (ClockLab 6). Pre-pregnancy and throughout most of gestation, 24h average SBP, DBP, and MAP were higher in HFD vs CD females (p<0.05). Conversely, 24h average SBP, DBP, and MAP were lower in HFD females at GD19-21 (p<0.05), and not different between groups from GD22 to PD1 (p>0.05). HFD and CD Dahl SS maintained a 24h MAP rhythm pre-pregnancy, and at early- (GD0-7) and mid-gestation (GD7-14) (p<0.05). However, during late gestation (GD14-21), 4/5 HFD females lost MAP circadian rhythmicity compared to 1/5 CD Dahl SS females (Chi2 periodogram; p< 0.05). All animals recovered circadian MAP rhythm at PD0. Litter size, number of stillborn, and PD0 pup birth weights were not different between groups (p>0.05). In conclusion, Dahl SS rats fed a HFD display higher 24h BP average pre-pregnancy and throughout most of gestation, but a lower nadir in the days preceding parturition. This is notably accompanied by a loss of circadian BP rhythm during late gestation. The HFD Dahl SS may be a valuable model to address the interplay of excessive maternal adiposity and BP rhythm disturbances during pregnancy. NIH NHLBI P01 HL152951 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.