Estrogen stimulates SREBP2 expression in hepatic cell lines via an estrogen response element in the SREBP2 promoter

Abstract

ObjectiveHypoestrogenism in women is strongly associated with menopause and it can lead to lipid disorder, which predisposes people to premature cardiovascular disease. However, the mechanism of lipid disorder remains unclear. Sterol regulatory element-binding protein 2 (SREBP2) is the key transcription factor regulating cholesterol metabolism. We hypothesize that estrogen regulates SREBP2 transcription through an estrogen response element (ERE) in the SREBP2 promoter region.MethodsHuman hepatoblastoma cells (HepG2) were treated with dose-dependent concentrations of estradiol (E2) for 24 h. Then, SREBP2 expression was determined via real-time PCR and immunofluorescence. The expressions of the SREBP2 downstream target genes HMGCR and LDLR were determined via real-time PCR. Lipid secretion in the culture media of HepG2 cells was measured using ELISA. Through bioinformatics analysis, we identified high-scoring ERE-like sequences in the SREBP2 gene promoter. Chromatin immunoprecipitation analysis was used to confirm the ERE. DNA fragments of the putative or mutated ERE-like sequence were synthesized and ligated into pGL3-basic plasmid to construct the SREBP2 promoter luciferase reporter systems. SREBP2-Luciferase (SREBP2-Luc), SREBP2-Mutation (SREBP2-Mut) and the blank control were transfected into hepatic cell lines. Luciferase activities were measured using the dual-luciferase reporter assay system. Chromatin immunoprecipitation analysis and the luciferase reporter assay were repeated in human hepatoma cells (HuH-7).ResultsWe found that E2 dose-dependently increased the expression of SREBP2 in HepG2 cells and that the increased levels were blocked when treated with an estrogen receptor-alpha antagonist. Additionally, E2 increased both HMGCR and LDLR expression and lipid secretion in HepG2 cells. Notably, we identified a functional ERE in the SREBP2 gene promoter, to which E2 could specifically bind and induce transcription.ConclusionsAn ERE was identified in the SREBP2 gene promoter. It mediates the regulation of SREBP2 expression by estrogen in hepatocytes. This study provides a mechanism to link cardiovascular disease with estrogen.

Accelerated Ovarian Aging Among Type 2 Diabetes Patients and Its Association With Adverse Lipid Profile

“…Negative associations of E2 with TC and LDL-C has been demonstrated in ERα-deficient models, women with E2 deficiency and postmenopausal women on E2 treatment ( 59 – 65 ), results consistent with our study findings. These protective effects of E2 can be largely attributed to its upregulation of low-density lipoprotein receptors (LDLR) on hepatic cells: 1) through nuclear receptor ER, E2 stimulates the expression of transcription factors related to cholesterol metabolism, which upregulates LDLR expression as a downstream target ( 66 ); 2) through G protein-coupled estrogen receptor, E2 prevents PCSK9-dependent LDLR degradation, thus reducing the levels of TC and LDL-C as well ( 67 ). In terms of gonadotropins, although studies regarding the role of LH in dyslipidemia are scarce, several previous studies addressing the links between FSH and lipid levels in postmenopausal women have demonstrated that higher FSH in postmenopausal women was related to higher levels of both TC and LDL-C, with stronger relations seen in younger compared to older postmenopausal women, which were close to the results of our results ( 29 , 68 ).…”

The Effects of Calina Papaya Leaf Ethanol Extract On Estrus Cycle And Uterus Morphology of Wistar Rats

“…The short estrus phase can be influenced by triterpenoid and saponin compounds contained in the ethanol extract of papaya leaves by hormonal disturbances (Hakameri et al, 2020). Triterpenoids and saponins can bind to estrogen receptors and trigger interactions with Estrogen Response Element (ERE) in triggering the expression of estrogen responsive genes in estrogen synthesis (Men & Zong., 2019). Increased levels of estrogen in the blood that are too high can cause negative feedback, thereby suppressing the ovulation mechanism (Jain et al, 2015;Zhang et al, 2020).…”

Sex‐specific effects of in vitro fertilization on adult metabolic outcomes and hepatic transcriptome and proteome in mouse

“…Likewise, pathway analysis of the liver proteome from a subset of individuals indicates overrepresentation of proteins involved in cholesterol biosynthesis (GO:0045337; FDPS and HMGCS1); we confirmed upregulation of SREBP‐2 and its main targets (ie, HMGCS1 and HMGCR) in the entire cohort. Because estrogen regulates Srebp‐2 transcription through an estrogen response element, 62 our finding of upregulated Esr1 in liver of IVF‐females, suggests that estrogen dynamics are altered in IVF‐females in a way that contributes to dysregulation of cholesterol homeostasis. Our findings lay the groundwork for further interrogating the estrogen‐SREBP‐2 relationship and the interrelated metabolic, endocrine and reproductive effects.…”