MicroRNA-27a is a key modulator of cholesterol biosynthesis

Abstract

Hypercholesterolemia is a strong predictor of cardiovascular diseases. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase gene (Hmgcr) coding for the rate-limiting enzyme in the cholesterol biosynthesis pathway is a crucial regulator of plasma cholesterol levels. However, the post-transcriptional regulation of Hmgcr remains poorly understood. The main objective of this study was to explore the role of miRNAs in the regulation of Hmgcr expression.Systematic in silico predictions and experimental analyses reveal that miR-27a specifically interacts with the Hmgcr 3'-untranslated region in murine and human hepatocytes. Moreover, our data shows that Hmgcr expression is inversely correlated with miR-27a levels in various cultured cell lines, human and rodent tissues. Actinomycin D chase assays and relevant experiments demonstrate that miR-27a regulates Hmgcr by translational attenuation followed by mRNA degradation. Early Growth Response 1 (Egr1) regulates miR-27a expression under basal and cholesterol-modulated conditions. miR-27a augmentation via tail-vein injection of miR-27a mimic in high cholesterol diet-fed Apoe -/mice shows down-regulation of hepatic Hmgcr and plasma cholesterol levels. Pathway and gene expression analyses show that miR-27a also targets several other genes (apart from Hmgcr) in cholesterol biosynthesis pathway. Taken together, miR-27a emerges as a key regulator of cholesterol biosynthesis and has therapeutic potential for clinical management of hypercholesterolemia.Sterol-regulatory element-binding protein 1; PVDF, polyvinylidene difluoride; ERAD, ER-associated protein degradation; SCAP, SREBP cleavage activated protein.the respective LOD scores. We also compared mouse and rat Hmgcr gene sequences (GenBank accession no: NM_008255 and NM_013134.2, respectively) using mVISTA browser.In silico predictions of potential miRNA binding sites in Hmgcr-3′UTR and putative miRNA targets in the cholesterol biosynthesis pathway.Putative miRNA binding sites in mouse Hmgcr (Hmgcr)-3'UTR sequence (NCBI reference number: NM_008255.2) were predicted using various bioinformatic algorithms [viz. miRWalk, miRanda, TargetScan, PITA, RNA22 and RNAhybrid (Table S2)]. Since, a large number of miRNAs were predicted by these online tools, we selected only those miRNAs that were predicted by at least five algorithms. Further, differences in hybridization free energy indicating the stability of the microRNA-mRNA interaction was determined computationally by two online tools called PITA and RNAhybrid. The lower or more negative ∆∆G value predicted by PITA indicates stronger binding of the microRNA to the given site; as a rule of thumb, sites having ∆∆G values below -10 are likely to be functional and selected for experimental validation. RNAhybrid calculates the minimum free energy (∆G) of hybridization between target mRNA and miRNA. An RNAhybrid ∆G score of less than -20 kcal/mol is a strong indicator for interactions of a miRNA with target mRNA. In each case, the minimum number of nucleotides in seed sequence was selected as ...

The Role of microRNAs in Metabolic Syndrome-Related Oxidative Stress

“…Other miRNAs implicated in potential therapy of hypercholesterolemia are miR-27a and miR-30c. First of them was injected via tail vein into Apoe-/- mice subjected to high cholesterol diet and suggested to diminish plasma lipid levels along with hepatic levels of HMGCR [ 334 ]. Further, miR-27a was proved to directly target HMGCR via translational repression and mRNA decay.…”

“…Moreover, it was observed that hypoxia, a sign of liver damage, induced binding of early growth response protein 1 (Egr1) to promoter regions of miR-27a, leading to its induction, to mediate the downregulation of HMGCR. Finally, increase of miR-27a and decrease of HMGCR were found in livers of three mice models of MetS [ 334 ]. Further, C57BL/6J mice with diet-induced hypercholesterolemia showed also amelioration of hypercholesterolemia, yet upon delivery of miR-30c mimic to the liver due to decrease of hepatic lipoprotein production but not LDL clearance [ 335 ].…”

Increased small extracellular vesicle secretion after chemotherapy via upregulation of cholesterol metabolism in acute myeloid leukaemia

“…Doxorubicin treatment in breast cancer was reported to increase levels of intracellular cholesterol [ 21 ]. Chemotherapy resistant leukaemia cells down-regulate miR-27a expression which was known as a key regulator of cholesterol homoeostasis [ 22 , 23 ]. Metabolism of intracellular cholesterol is tightly regulated by complex multi-step networks.…”

Bone marrow deficiency of mRNA decaying protein Tristetraprolin increases inflammation and mitochondrial ROS but reduces hepatic lipoprotein production in LDLR knockout mice

“…These cell-derived exosomes contain numerous miRNAs, which can be taken up into neighboring or distant cell types including hepatocytes to modulate their function [ 73 ]. Moreover, previous studies demonstrated that miR-27a can interacts with the HMG-CoA reductase 3′ untranslated region in murine and human hepatocytes and downregulate its expression [ 74 ]. Therefore, we believe that the miR-27a within the exosomes presumably secreted from TTP deficient bone marrow derived macrophages as the exosome dock on the hepatocyte modulate the hepatocyte lipid metabolism and downregulate the HMG-CoA reductase mRNA.…”