P-636 Effects of maternal circadian rhythm changes: intergenerational influences on testicular steroidogenesis in offspring
Authors: Gorgulu M , Tas G  G , Sati L 
Published: July 2024

Abstract

Study question
Do alterations in the maternal circadian rhythm during pregnancy and lactation result in changes to the male offspring’s testicular steroidogenesis intergenerationally?

Summary answer
The expression of proteins associated with steroidogenesis is altered due to maternal circadian rhythm changes during pregnancy and lactation periods.

What is known already
Circadian rhythms impact diverse physiological processes, including reproduction. Several clock genes have been linked to reproductive function. However, there is a complex interaction between hormones, fertility, and the circadian clock. It has been shown that disruption of the circadian clock machinery has negative effects on reproductive biology. Current literature indicates a potential relationship between the circadian clock, testicular steroidogenic-related gene expression profiles, and testosterone synthesis. Steroidogenesis involves a complex cascade of enzymatic reactions. An increasing body of evidence from animal studies suggests a relationship between maternal chronodisruption and long-term offspring health and fertility.

Study design, size, duration
Male offspring from pregnant Wistar rats (n = 60) were exposed to control (12 hours light/12 hours dark), short day (SD) (8 hours light/16 hours dark), or long day (LD) periods (16 hours light/8 hours dark) during only pregnancy, only lactation, or both periods (n = 6/group) categorized as control, SD pregnancy (SD-P), SD lactation (SD-L), SD pregnancy and lactation (SD-P+L), LD pregnancy (LD-P), LD lactation (LD-L), LD pregnancy and lactation (LD-P+L) groups.

Participants/materials, setting, methods
The expression of critical components of testicular steroidogenesis, including steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (cytochrome p450scc), 17-beta hydroxysteroid dehydrogenase 3 (HSD17B3), androgen receptor (AR), and luteinizing hormone receptor (LHR), was analyzed in the testis by counting the percentage of positively-stained Leydig cells and ImageJ analysis of immunohistochemistry and western blot. Serum FSH, LH, and testosterone hormones were measured at four zeitgeber time (ZT) points (ZT0, ZT6, ZT12, and ZT18) using ELISA.

Main results and the role of chance
All of these testicular steroidogenic enzymes were localized in the Leydig cell, and AR was predominantly observed in the Sertoli cell. Although there are no significant differences between the groups in terms of immunolocalization patterns, the expressions of p450scc and AR proteins were significantly decreased in the SD-P and SD-L groups compared to the control group (p &lt; 0.001). In addition, western blot data indicated a decreased expression of p450scc in the SD-P+L group. However, an increased expression of HSD17B3 was detected in both SD-P+L and LD-P+L groups compared to the control group (p = 0.003, p &lt; 0.001, respectively). Among the steroidogenesis-related proteins evaluated, the protein expression levels of StAR and LHR proteins were not altered. FSH showed a statistically significant increase in the LD-L (ZT0), SD-P+L (ZT12), LD-L (ZT12), and LD-P+L (ZT18) groups when compared to the corresponding control groups at the respective time points (p &lt; 0.05). In contrast, LH levels decreased significantly in the LD-P+L (ZT0) group (p &lt; 0.05). Nevertheless, no statistical difference was determined for testosterone levels between groups.

Limitations, reasons for caution
Most studies on circadian rhythm have used rodent models. Results from animal models are often informative. However, there is a limitation in the appropriate translation of findings in rodents to human studies.

Wider implications of the findings
The effects triggered by maternal chronodisruption can be intergenerationally transmitted, potentially affecting offspring health. Our results indicate alterations in the expression of proteins involved in testicular steroidogenesis and time-point-dependent changes in the FSH and LH hormone levels due to maternal circadian rhythm changes, further supporting the potential implications for offspring.

Trial registration number
This work was supported by research grants from the Scientific and Technological Research Council of Turkey (TUBITAK) (SBAG 219S636) and Akdeniz University, The Scientific Research Projects Coordination Unit (TYL-2018-3580).