Analysis of the clock proteins in the hypothalamic-pituitary-gonadal axis and the relation with female reproductive senescence

Abstract

Aging is the result of cumulative, progressive, intrinsic, and deleterious functional and structural changes that usually begin to manifest in reproductive maturity, although their genesis may have been earlier. The reproductive function in female organisms is controlled by both the hypothalamic-pituitary-gonadal axis and the biological clock, both of which are fundamental for the outgrowth of the GnRH/LH peak and ovulation. "Clock genes", such as Period (Per1 and Per2), are part of the biological machinery of the biological clock and interact by inhibiting the transcription of the Bmal1 and Clock genes, which stimulate the expression of the former, forming a self-regulating feedback loop. Expression circadian of the Per 1 gene occurs in GnRH neurons and the expression of all cognates of the clock genes was detected in the pituitary gonadotrophs. Studies from the 1990s and early 2000 have shown that deterioration in hypothalamic functions is a crucial element in reproductive decline and that the capacity of the circadian temporal clock of the brain in conducting diurnal neurochemical events is reduced with advancing age. A study conducted by us showed that during the aging of Wistar rats during the period of persistent diestrus, the content of GnRH and noradrenaline remained low and unchanged at the times analyzed (10, 14 and 18 h) as well as the plasma concentration of LH, when compared with adult animals. However, we observed a higher activity of noradrenergic neurons of the preoptic area (APO) and locus coeruleus (LC) and higher and variable plasma concentrations of estradiol and progesterone in older animals (NICOLA et al., 2016). Our purpose is to analyze the clock proteins in the hypothalamic-pituitary-gonad axis and the possible correlation with reproductive senescence, in order to measure aging by measuring changes in physiological traces, or biomarkers, that are important for normal functioning. We will study in rats in the natural periestropause: 1- Kiss1 gene expression in the APO and arcuate nucleus (ARC), PER1, ReverbA, BMAL1, in the HPG axis; 2- VIP and AVP in SCN during the reproductive aging of Wistar females. This evaluation will be performed using RT-PCR and qPCR techniques for target genes and Western blotting for proteins whose genes are expressed significantly. (AU)