Long Non-Coding RNA TUG1 Attenuates Insulin Resistance in Mice with Gestational Diabetes Mellitus via Regulation of the MicroRNA-328-3p/SREBP-2/ERK Axis.

BACKGROUND: Long non-coding RNAs (lncRNAs) have been illustrated to contribute to the development of gestational diabetes mellitus (GDM). In the present study, we aimed to elucidate how lncRNA taurine upregulated gene 1 (TUG1) influences insulin resistance (IR) in a high-fat diet (HFD)-induced mouse model of GDM. METHODS: We initially developed a mouse model of HFD-induced GDM, from which islet tissues were collected for RNA and protein extraction. Interactions among lncRNA TUG1/microRNA (miR)-328-3p/sterol regulatory element binding protein 2 (SREBP-2) were assessed by dual-luciferase reporter assay. Fasting blood glucose (FBG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR), HOMA pancreatic ß-cell function (HOMA-ß), insulin sensitivity index for oral glucose tolerance tests (ISOGTT) and insulinogenic index (IGI) levels in mouse serum were measured through conducting gain- and loss-of-function experiments. RESULTS: Abundant expression of miR-328 and deficient expression of lncRNA TUG1 and SREBP-2 were characterized in the islet tissues of mice with HFD-induced GDM. LncRNA TUG1 competitively bound to miR-328-3p, which specifically targeted SREBP-2. Either depletion of miR-328-3p or restoration of lncRNA TUG1 and SREBP-2 reduced the FBG, FINS, HOMA-ß, and HOMA-IR levels while increasing ISOGTT and IGI levels, promoting the expression of the extracellular signal-regulated kinase (ERK) signaling pathway-related genes, and inhibiting apoptosis of islet cells in GDM mice. Upregulation miR-328-3p reversed the alleviative effects of SREBP-2 and lncRNA TUG1 on IR. CONCLUSION: Our study provides evidence that the lncRNA TUG1 may prevent IR following GDM through competitively binding to miR-328-3p and promoting the SREBP-2-mediated ERK signaling pathway inactivation.

miR-335-5p induces insulin resistance and pancreatic islet ß-cell secretion in gestational diabetes mellitus mice through VASH1-mediated TGF-ß signaling pathway.

Multiple studies have reported different methods in treating gestational diabetes mellitus (GDM); however, the relationship between miR-335-5p and GDM still remains unclear. Here, this study explores the effect of miR-335-5p on insulin resistance and pancreatic islet ß-cell secretion via activation of the TGFß signaling pathway by downregulating VASH1 expression in GDM mice. The GDM mouse model was established and mainly treated with miR-335-5p mimic, miR-335-5p inhibitor, si-VASH1, and miR-335-5p inhibitor + si-VASH1. Oral glucose tolerance test (OGTT) was conducted to detect fasting blood glucose (FBG) fasting insulin (FINS). The OGTT was also used to calculate a homeostasis model assessment of insulin resistance (HOMA-IR). A hyperglycemic clamp was performed to measure the glucose infusion rate (GIR), which estimated ß-cell function. Expressions of miR-335-5p, VASH1, TGF-ß1, and c-Myc in pancreatic islet ß-cells were determined by RT-qPCR, western blot analysis, and insulin release by ELISA. The miR-335-5p mimic and si-VASH1 groups showed elevated blood glucose levels, glucose area under the curve (GAUC), and HOMA-IR, but a reduced GIR and positive expression of VASH1. Overexpression of miR-335-5p and inhibition of VASH1 contributed to activated TGFß1 pathway, higher c-Myc, and lower VASH1 expressions, in addition to downregulated insulin and insulin release levels. These findings provided evidence that miR-335-5p enhanced insulin resistance and suppressed pancreatic islet ß-cell secretion by inhibiting VASH1, eventually activating the TGF-ß pathway in GDM mice, which provides more clinical insight on the GDM treatment.

Protective effect of sRAGE on fetal development in pregnant rats with gestational diabetes mellitus.

To investigate the protective effect of secretory receptor for advanced glycation endproducts (sRAGE) on the fetal development using rat model of gestational diabetes mellitus (GDM). The model of pregnant rats with intrauterine hyperglycemia was established by intraperitoneal injection of 25 mg/kg streptozotocin (STZ). Rats with established GDM were randomly grouped, and the pregnant rats in the experimental group were subsequently injected with recombinant sRAGE protein (5 mg/kg, in 0.2 mL PBS) at tail vein every 24 h, while the rats in control group were injected with the same dosage of albumin solution. Blood glucose, serum levels of advanced glycation endproducts (AGEs), and levels of RAGE protein in brain and heart tissues of pregnant rats were measured at 3, 13, and 19 days postconception. At 19 days fetuses were delivered by cesarean section, number of fetuses, their weight and placental weights were recorded, and fetal malformations and defects were analyzed visually and pathologically. The expression level of RAGE, NOX2, MCP-1, p65, VCAM-1, and VEGF mRNA in placenta was evaluated by real-time PCR. p65 protein localization was detected by immunohistochemistry in fetal brain and heart tissue sections. We analyzed the correlation between AGEs and RAGE level and the development of fetal rats, and the protective effect of blocking AGEs-RAGE pathway on the fetal development in the rat model of GDM was investigated. (1) The concentration of blood glucose and AGEs in serum of pregnant rats with GDM was significantly higher than in control group (p < 0.05), with strong correlation between blood glucose and levels of AGEs (r = 0.693, p < 0.05). (2) While both the number of fetuses and placental wet weight in pregnant rat model of GDM were similar to control group, pups from GDM group exhibited higher incidence of developmental abnormalities and higher average weight (p < 0.05). sRAGE treatment slightly but not significantly reduced the probability of the fetal developmental defects, as compared to GDM group. (3) p65, a part of the NF-kB heterodimeric complex, was localized to cell nuclei in the fetal tissues of pups delivered by GDM rats, while sRAGE treatment partially restored cytoplasmic localization of p65, similarly to control tissues. Increased incidence of fetal developmental defects observed in offsprings of pregnant rats with GDM had significant correlation with the level of AGEs in serum of pregnant rats and expression levels of RAGE protein in tissues. GDM resulted in upregulation of mRNA expression of several pro-inflammatory and ROS-inducing genes in placental tissues of pregnant rats. Elevated blood glucose, serum AGEs levels, and increased gene expression are attenuated by intravenous sRAGE treatment. sRAGE appears to reduce the activity of NF-κB in fetal tissues, thus potentially having a protective effect on fetal development.