CREB‐upregulated lncRNA MEG3 promotes hepatic gluconeogenesis by regulating miR‐302a‐3p‐CRTC2 axis

Abstract

Hepatic gluconeogenesis is the major contributor to hyperglycemia in diabetes. Long noncoding RNA (lncRNA) maternally expressed gene 3 (MEG3) has been shown to promote hepatic insulin resistance; however, the underlying mechanism involving hepatic gluconeogenesis remains unclear. This study aims to investigate the potential role of MEG3 in hepatic gluconeogenesis. Mouse primary hepatocytes were used in this study. Cell transfection was performed for the overexpression or knockdown of specific genes. Expressions of MEG3, miR-302a-3p, CREB-regulated transcriptional coactivator 2 (CRTC2), protein kinase A (PKA), cAMP-response element binding protein (CREB), PPARγ coactivator-1α (PGC-1α), phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pc) were determined by quantitative real-time polymerase chain reaction (qRT-qPCR) and Western blot analysis, respectively. The association among MEG3, miR-302a-3p, and CRTC2 was disclosed by dual-luciferase reporter assay. MEG3 was highly expressed in high glucagontreated mouse primary hepatocytes. CREB-induced MEG3 upregulation increased gluconeogenic gene expression in high glucagon-treated primary hepatocytes, while MEG3 interference led to an opposite effect. MEG3 served as a competing endogenous RNA (ceRNA) to upregulate CRTC2 by targeting miR-302a-3p in primary hepatocytes, thereby increasing PGC-1α-PEPCK/G6Pc. CREB-upregulated MEG3-enhanced hepatic gluconeogenesis via mediating miR-302a-3p-CRTC2 axis, revealing that MEG3 might be a potential target and therapeutic strategy for diabetes. K E Y W O R D SCRTC2, hepatic gluconeogenesis, MEG3, miR-302a-3p

Long Non-coding RNA Maternally Expressed 3 Increases the Expression of Neuron-Specific Genes by Targeting miR-128-3p in All-Trans Retinoic Acid-Induced Neurogenic Differentiation From Amniotic Epithelial Cells

“…Additionally, we analyzed the causes of decreased miR-128-3p expression. We identified the long non-coding RNA (lncRNA) maternally expressed 3 (MEG3) as interacting with miR-128-3p, and previous reports of its up-regulation through a series of gene transcriptions after cAMP pathway activation (Zhao et al, 2006;Zhu et al, 2019). This reinforces our current miR-128-3p biological function proposal.…”

“…We detected a marked increase in intracellular cAMP levels in induced AECs (Figure 6B). The CRE-binding protein CREB was previously shown to enter the nucleus and to combine with CRE to enhance MEG3 transcription, after elevating the concentration of cAMP (Zhao et al, 2006;Zhu et al, 2019). Here, we detected the expression of phosphorylated CREB and total CREB in whole cell lysates using Western blot and immunofluorescence.…”

“…MEG3 can modulate neurogenic differentiation from AECs under ATRA treatment, but the mechanisms underlying this are unclear. Previous work (Zhao et al, 2006;Zhu et al, 2019) described how elevated cAMP levels enhanced endogenous MEG3 expression through cAMP-response element (CRE) directly binding the MEG3 promoter region. We detected the concentration of cAMP after ATRA treatment in AECs using a cAMP assay kit (competitive ELISA, Fluorometric) and combined this with our previous data (Zhao et al, 2004).…”

“…Previous studies have found that MEG3 promoter activity is mainly attributable to a CRE site and demonstrated that proteins from the CREB family directly bind to this site. Additionally, elevated cAMP levels were reported to stimulate transcription from the MEG3 promoter and enhance MEG3 expression (Zhao et al, 2006;Zhu et al, 2019). Another study found that ATRA enhanced intracellular cAMP accumulation and CREB phosphorylation (Suwa et al, 2016).…”

Identification of differentially expressed mRNA and the Hub mRNAs modulated by lncRNA Meg3 as a competing endogenous RNA in brown adipose tissue of mice on a high-fat diet

“…Several lncRNAs, including maternally expressed gene 3 ( Meg3 ), have been identified as ceRNAs implicated in pathophysiological processes of metabolic disorders [ 11 – 13 ]. Meg3 has been shown to serve as a ceRNA to regulate the miR-302a-3p -CRTC2 axis and the miR-214 -ATF4 axis, and promote hepatic insulin resistance [ 11 , 12 ].…”