Cardiovascular Journal of Africa • SAHS Biennial Congress 2024 27 AFRICA Submission ID: 1638 Introduction Postmenopausal shift workers exhibit a heightened risk of cardiometabolic disorders. The risk is likely due to the dual impact of decreased estrogen concentrations associated with menopause and circadian misalignment resulting from irregular light exposure schedules. However, the combined effect of shiftwork-induced circadian misalignment and estrogen decline on cardiometabolic health remains poorly understood, particularly in individuals with pre-existing conditions like hypertension. The present study aimed to investigate whether circadian misalignment worsens cardiometabolic parameters in estrogen-deficient female spontaneously hypertensive rats (SHR). Methods Circadian misalignment was induced by a 10-week chronic phase shift (CPS) protocol, and estrogen deficiency was induced by ovariectomy. Female spontaneously hypertensive rats (SHR) (n=36) were either ovariectomized or sham-operated at 7 weeks old. Subsequently, they were exposed to either the chronic phase shift (CPS) or the control light (ctr light) schedule (n=9 per group) for 10 weeks. Body mass, food and water intake, blood pressure, and fasting blood glucose concentrations were measured throughout the 10-week intervention. An oral glucose tolerance test (OGTT) was performed 3 days before intervention completion. The ventricular systolic and diastolic function were assessed by echocardiography on the day of the 10-week intervention completion. Finally, organ masses were measured, and low-density lipoprotein (LDL) concentrations were determined using ELISA (enzyme-linked immunosorbent assay). Results Ovariectomized rats were heavier and had greater food intake and organ masses than sham-operated rats. When normalized to body mass, the food intake and organ masses were lower than in sham-operated rats. Ovariectomized rats had greater left ventricular (LV) dimensions and reduced LV contraction than sham-operated rats. The cardiometabolic parameters measured were similar between the CPS and control light rats, except for a greater water intake and a reduced liver mass in CPS rats. When normalized to body mass, sham-operated rats had a greater water intake than the ovariectomized rats. No interaction between ovariectomy and CPS was demonstrated. Conclusion Our findings indicate that estrogen deficiency impairs systolic function in female SHR, and circadian misalignment does not worsen cardiometabolic parameters in estrogen-deficient female SHR. However, circadian misalignment may still influence other physiological pathways in female SHR, warranting further investigation. Name: Presenting Author Information Article Category Abstract Title Integrated Molecular Physiology Research Initiative, The Wits Health Consortium, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa 1448621@students.wits.ac.za English Abstract Students - Currently enrolled postgraduate students Dissociation of circadian misalignment and estrogen deficiency on cardiometabolic health in female spontaneously hypertensive rats Author Affiliation: Email: Refentshe Amandu’s Nthlane Science Theme Basic Upload your slides or pictures illustrating the case Nthlane Refentshe Amandu’s Illustration of Case: Figures Figure 1.1: The 10-week intervention study design. The rats were assigned to either the control light (left) or the chronic phase shift (CPS) (right) schedules. The control lightexposed rats were maintained on a 12/12-hour light/dark cycle with lights on at 7 a.m. and lights off at 7 p.m. everyday. Whereas the CPS protocol-exposed rats were maintained on a 12/12-hour light/dark cycle reversed every 7 days (lights on at 7 p.m. and lights off at 7 a.m., followed by 7 days of control lighting schedule). The black and white bars above the panels indicate the duration of periods of light (day) and darkness (night), respectively. Data represented as a heat map and expressed as mean, with the light phase <200 lux and dark phase = 0 lux. Figure 1.2: Changes in weekly body mass in female SHR. Body mass measurements were taken weekly, starting from the week of surgery (Sx) and continuing through the 10-week intervention period (week 0 to 10). The dotted line at week 0 separates the pre-intervention period (baseline) from the 10-week CPS intervention period. A significant increase in body mass was observed in all groups overtime. There was a significant effect of estrogen deficiency on body mass. Data expressed as mean ± SD, n=9 per group. Ctr Light, control lighting; CPS, chronic phase shift; Ovx, ovariectomy, Sx, pre-surgery body mass. ###, p<0.0001 change overtime; ***, p<0.0001 vs shamoperated groups. POSTER PRESENTATION
RkJQdWJsaXNoZXIy NDIzNzc=