Characterization of gene expression in adrenal glands of mice lacking the circadian clock protein PER1

Abstract

The circadian clock regulates a variety of physiological responses throughout a 24‐hour period. At a molecular level, the clock is governed by four core transcription factors, including PER1 and CRY, which are found in every cell in the human body. All reported circadian clock gene KO mice have a blood pressure (BP) phenotype. Aldosterone, a mineralocorticoid hormone and product of the renin‐angiotensin‐aldosterone system (RAAS), is secreted by the adrenal cortex and leads to increased sodium reabsorption by the kidneys in response to low BP or low blood volume. Previously we reported that 129/sv mice lacking the circadian clock gene Per1 had reduced BP and reduced plasma aldosterone levels associated with decreased expression of HSD3B1, a key enzyme in the steroid hormone synthesis pathway. Conversely, we found that male C57BL/6 Per1 KO mice have higher BP than control mice and develop non‐dipping hypertension (a lack of dip in BP during the rest period) on a high salt diet plus mineralocorticoid treatment. Non‐dipping hypertension has been associated with an increased risk for cardiovascular disease in humans. Interestingly, female Per1 KO mice do not develop non‐dipping hypertension on a high salt diet plus mineralocorticoid treatment. The goal of this study was to determine if expression of genes involved in the aldosterone synthesis pathway is altered in C57BL/6 Per1 KO mice. These deviances could explain the BP phenotype observed at the physiological level in male mice. We obtained adrenal glands from male and female WT and Per1 KO mice at noon (midpoint of the mouse rest phase), the same time at which serum was collected for aldosterone measurements. RNA was isolated from these tissues, converted to cDNA, and mRNA levels of genes involved in circadian rhythm and aldosterone synthesis were measured by quantitative real time PCR (qPCR). Preliminary data show that Cry1 is significantly down‐regulated in female Per1 KO mice by about 50% versus WT (n=5/6 per group, p<0.05). Expression of aldosterone synthesis genes CYP11B and HSD3B1 did not appear to be significantly altered in the adrenal tissue of male or female Per1 KO mice compared to WT. In contrast to what was observed with 129/sv Per1 KO, plasma aldosterone levels did not differ between C57BL/6 Per1 KO vs. WT. The observed difference in Cry1 expression suggests that RAAS and the circadian clock may work together in the maintenance of homeostatic BP. In the future we expect to perform similar experiments using male and female WT and Per1 KO mice adrenal tissue collected at a midnight time point in order to further investigate the communication occurring at the molecular level between RAAS and the circadian clock.Support or Funding InformationNIH/NIDDK 1R01DK109570; The Gatorade Trust through the UF Department of MedicineThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.