Abstract
The factors influencing Leydig cell maturity and the acquisition of functional capacity are incompletely defined. Here we analyzed the constant light (LL) influence on Leydig cells’ endocrine function during reproductive maturation. Rats were exposed to LL from P21 to P90. Data were collected at juvenile (P35), peri/pubertal (P42, P49), and adult (P90) stages of life. The results proved the effect of LL on rats’ physiology by changing of bimodal voluntary activity pattern into free-running. Additionally, the peripheral clock in Leydig cells changed in LL condition, indicating disturbed rhythm: the positive element (Bmal1) increased in pre-/pubertal but decreased in the adult period, while negative elements (Per2 and Reverba) were increased. The effects of LL were most prominent in puberty: pituitary genes encoding gonadotropic hormones (Cga, Lhb, Fshb) decreased; serum corticosterone increased, while serum androgens and mass of testicular and sex accessory organs reduced; markers of Leydig cells maturity/differentiation (Insl3, Lhcgr) and steroidogenesis-related genes (Scarb1, Star, Cyp11a1, Cyp17a1) decreased; the steroidogenic and energetic capacity of the Leydig cell mitochondria decreased; the mtDNA copy number reduced, and mitochondrial dynamics markers changed: fusion decreased (Opa1 and Mfn2), and mitophagy increased (Pink1). In adults, the negative effect of LL on mitochondrial function and steroidogenic capacity persists in adult Leydig cells while other parameters reached control values. Altogether, the results indicate that LL slows down Leydig cells’ maturation by reducing the endocrine and energy capacity of cells leading to the delay of reproductive development.
Highlights
Most physiological processes in our body oscillate daily and are synchronized with external environmental changes [1]
Rats that grow up in constant light were 40% less active measured in the period from the sixtieth to the ninetieth postnatal day (Figure 1C)
The weight of the testicles, seminal vesicles, and the ventral and dorsal prostate, which increased with age, were lower during puberty (42nd and 49th days) in rats that grew up in constant light (Figure 1E)
Summary
Most physiological processes in our body oscillate daily and are synchronized with external environmental changes [1]. Almost all hormones essential for life, including reproductive hormones, are secreted in a circadian rhythm. Adequate exposure to environmental cues such as the light/dark cycle is critical to the body physiology’s temporal organization. Growing Up Under Constant Light daily contrasts, including light/darkness contrasts. Many people are not exposed to a strong light/dark cycle spending most of their time indoors with the low light distinction between day and night [2], which can significantly disrupt rhythms, body physiology, and health. How living and growing up in buffered oscillations of external factors, including the light/dark cycle, affects males’ reproductive maturation remains to be clarified
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