LH Induces De Novo Cholesterol Biosynthesis via SREBP Activation in Granulosa Cells During Ovulation in Female Mice

Abstract

In the liver, the sterol response element binding protein (SREBP) and the SREBP cleavage-activated protein (SCAP) complex upregulates cholesterol biosynthesis by gene induction of de novo cholesterol synthetic enzymes (Hmgcr, Cyp51, and Dhcr7). Insulin induced gene 1 (INSIG1) negatively regulates cholesterol biosynthesis by the inhibition of de novo cholesterol biosynthetic gene expression. In the ovary, cholesterol is de novo synthesized; however, the roles of SREBP and its regulators (SCAP and INSIG1) are not well understood. In this study, when immature mice were treated with gonadotropins (eCG followed by hCG), eCG induced and hCG maintained the expression of SREBP-1a, -2, and SCAP granulosa cells, whereas INSIG1 expression was dramatically downregulated after hCG injection. Downregulation of INSIG1 led to generate the SREBPs active form and translocate the SREBPs active form to nuclei. Inhibition of generation of the SREBPs active form by fatostatin or Scap siRNA in both in vivo and in vitro significantly decreased the expressions of de novo cholesterol biosynthetic enzymes, cholesterol accumulation, and progesterone (P4) production compared to control group. Fatostatin treatment inhibited the ovulation and increased the formation of abnormal corpus luteum which trapped the matured oocyte in the corpus luteum, however, the phenomenon was abolished by P4 administration. The results showed that decreasing INSIG1 level after hCG stimulation activated SREBP-induced de novo cholesterol biosynthesis in granulosa cells of preovulatory follicles, which is essential for P4 production and the rupture of matured oocyte during ovulation process.

Transcriptional profiling of the developing rat ovary following intrauterine exposure to the endocrine disruptors diethylstilbestrol and ketoconazole

“…While its role during gonad development is not clearly established, several potassium channels are known to participate in the regulation of progesterone secretion (Kim et al 2020 ). Dhcr7 encodes an enzyme involved in the cholesterol biosynthesis (Nakanishi et al 2021 ). It has been identified as a biomarker of exposure to KTZ and DES in human adult ovarian cortex cultures (Li T et al Unpublished).…”

Effects of scoparone on non-alcoholic fatty liver disease revealed by RNA sequencing

“…shown that SREBP-1c and SREBP cleavage-activating protein (SCAP) complex induce cholesterol biosynthesis in the liver by upregulating the gene expressions of cholesterol synthases (Hmgcr, Cyp51 and Dhcr7) (32). Besides, SREBP-1c regulates the transcription of downstream lipid synthesis-related genes Acaca and Fasn (33).…”

Pre‐culture with transferrin‐Fe3+ before in vitro maturation improves the developmental competence of porcine oocytes matured in vitro

“…Reverse transcription was performed as recently described. 16 Briefly, isolated total RNA (5 ng/μL) was reverse-transcribed using 500 ng of poly-dT (Promega) and 0.25 U of avian myeloblastosis virus reverse transcriptase (Promega) for 75 min at 42°C and for 5 min at 95°C. Real-time PCR analysis was performed as we described recently.…”

“…Real-time PCR analysis was performed as we described recently. 16 Briefly, cDNA and primers were added to the KAPA SYBER FAST Universal qPCR kit (Kapa Biosystems) to give a total reaction volume of 15 μL. PCR was then performed using the MiniOpticon Real-Time PCR Detection Systems (Bio-Rad).…”