ABSTRACT
Isoliquiritigenin (ISL) is an active chalcone compound isolated from licorice. It possesses anti-inflammatory and anti-oxidative activities. In our previous study, we uncovered a great potential of ISL in treatment of type 2 diabetes mellitus (T2DM). Therefore, this study aims to reveal the mechanism underlying the alleviatory effects of ISL on T2DM-induced glycolipid metabolism disorder. High-fat-high-sugar diet (HFD) combined with intraperitoneal injection of streptozotocin (STZ) were used to establish T2DM mice model. All animal experiments were carried out with approval of the Committee of Ethics at Beijing University of Chinese Medicine. HepG2 cells were used in in vitro experiments, and sodium palmitate (SP) was applied to establish insulin resistance (IR) model cells. The effects of ISL on body weight, fasting blood glucose levels, and pathological changes in the livers of mice were examined. Enzyme-linked immune sorbent assay (ELISA) and real-time quantitative PCR (RT-qPCR) were applied to detect the regulatory effects of ISL on key targets involved in glucolipid metabolism. Additionally, molecular docking and analytical dynamics simulation methods were used to analyze the interaction between ISL and key target protein. The results indicate that ISL significantly downregulates the transcriptional levels and inhibits the activities of key enzymes involved in gluconeogenesis, including pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and fructose-1, 6-bisphosphatase (FBP). It also downregulates the transcriptional and protein levels of hepatocyte nuclear factor 4α (HNF4α) and cAMP response element binding protein (CREB), the two transcriptional factors involved in gluconeogenesis. Thus, ISL inhibits hepatic gluconeogenesis in T2DM mice. In addition, ISL reduces total cholesterol (TC) and triglyceride (TG) levels in the livers of T2DM mice. Moreover, ISL downregulates the mRNA levels of lipogenesis genes and upregulates those of genes involved in fatty acid oxidation, lipid uptake, and lipid export. In conclusion, ISL suppresses hepatic gluconeogenesis, promotes lipolysis, and restrains lipogenesis in T2DM mice, thereby improving the abnormal glycolipid metabolism caused by T2DM.
ABSTRACT
Isoliquiritigenin (ISL) is a flavonoid compound isolated from licorice. It possesses excellent antioxidant and anti-diabetic activities. This study aims to investigate the molecular mechanism underlying the alleviatory effect of ISL on energy metabolism imbalance caused by type 2 diabetes mellitus (T2DM). 8-week-old male C57BL/6J mice were used in in vivo experiments. The high-fat-high-glucose diet combined with intraperitoneal injection of streptozotocin was applied to establish T2DM animal model. All animal experiments were performed in accordance with the Institutional Guidelines of Laboratory Animal Administration issued by the Committee of Ethics at Beijing University of Chinese Medicine. HepG2 cells were used in in vitro experiments. Enzyme-linked immunosorbent assay (ELISA) and real-time quantitative polymerase chain reaction (RT-qPCR) were used to examine the protein and mRNA levels of mitochondrial function-related targets. The levels of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in HepG2 cells were measured by the flow cytometry. Additionally, the molecular docking of ISL and key target proteins was analyzed. It was found that ISL significantly inhibited the activity of mitochondrial respiratory chain complex I and increased the protein levels of uncoupling protein 2 (UCP2) in the livers of mice and HepG2 cells. It also obviously decreased the ROS levels and increased the MMP levels in cultured HepG2 cells. In addition, ISL promoted mitochondrial biogenesis by activating proliferator-activated receptor gamma co-activator 1α (PGC-1α) and enhanced mitophagy by upregulating Parkin. It also improved mitochondrial fusion by increasing the mRNA and protein levels of mitofusin 2 (MFN2). In conclusion, ISL alleviates energy metabolism imbalance caused by T2DM through suppression of excessive mitochondrial oxidative phosphorylation and promotion of mitochondrial biogenesis, mitophagy, and fusion.
ABSTRACT
<p><b>OBJECTIVE</b>To predict orthologous sequences of the GENCODE-identified 13 562 human long non-coding RNAs (lncRNA) in 16 mammalian genomes and construct a lncRNA database LongMan for lncRNA studies.</p><p><b>METHODS</b>The exon structures of a total of 13 562 human lncRNAs were analyzed using RNAfold, and their orthologous sequences were searched against 16 mammalian genomes using Infernal. The potential orthologous genes, transposons and splicing signals of human lncRNAs were predicted to construct a lncRNA database with a updating mechanism.</p><p><b>RESULTS</b>and</p><p><b>CONCLUSION</b>The lncRNA database LongMan we constructed, which currently contains 133 646 orthologous lncRNAs, provides information of the sequences, alignments, transposons, and species-specific insertions and deletions and allows database search on combinatorial conditions, graphic display and data download. As the first large-scale mammalian orthologous lncRNA database, LongMan has important values in future comparative and functional studies of lncRNAs.</p>