miR-93-5p promotes insulin resistance to regulate type 2 diabetes progression in HepG2 cells by targeting HGF

Molecular mechanism of microRNA-mediated hypoglycemic effect of whole grain highland barley

As a non-coding RNA, microRNA (miRNA) has been proven to play an important role in the development and progression of type 2 diabetes mellitus (T2DM). Highland barley is a whole grain from the Tibetan areas of China. Our previous studies have demonstrated its hypoglycemic effect. To further explore the underlining molecular mechanism, we investigated the effect of highland barley intervention on liver miRNA expression profiles in diabetic mice. Our results showed that ten differentially expressed miRNA among different groups were identified and their target genes were predicted. Remarkably, many glycometabolism-associated genes, including Foxo3, Nras, Rptor, Igf1r, Tsc2 and Braf, were negatively regulated by miR-122-5p, miR-503-5p, miR-455-5p and miR-210-3p, respectively. Pathway enrichment analysis revealed these target genes were mainly involved in AMPK, MAPK and FOXO signaling pathways. Thereby, these miRNA and mRNA were validated using qRT-PCR, and the results were consistent with the small RNA-seq and expectations. Highland barley could regulate the MAPK, AMPK, and FOXO signaling pathways by regulating critical miRNA-mRNA pairs, e.x. miR-210-3p-Tsc2/Braf, miR-122-5p-Foxo3, and miR-455-5p-Igf1r, thereby improving blood glucose metabolism in diabetic mice. The present study preliminarily explored the hypoglycaemic effects of highland barley based on transcriptomics, and more detailed and in-depth studies on this topic are needed in the future.

CircRNA-SCAF8 promotes vascular endothelial cell pyroptosis by regulating the miR-93-5p/TXNIP axis

OBJECTIVES

To investigate the role and mechanism of circRNA-SR-related CTD associated factor 8 (SCAF8) in regulating endothelial cell pyroptosis in high glucose environment.

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and divided into six groups. The normal control group and high glucose control group were cultured in cell culture medium with 5 and 33 mmol/L glucose, respectively. The RNA control group, circRNA-SCAF8 inhibition group, miR-93-5p overexpression group and miR-93-5p inhibition group were added with non-functional siRNA, circRNA-SCAF8 inhibitor, miR-93-5p overexpression molecule and miR-93-5p inhibitor in high glucose environment, respectively. Cell viability and pyroptosis were detected by cell counting kit-8 (CCK-8) assay, flow cytometry and Hoechst 33342/propidium iodide fluorescence double staining. Western blotting and enzyme-linked immunosorbent assay were used to detect the expression of pyroptosis-related factors including apoptosis-associated speck-like protein containing a CARD (ASC), cysteine aspartic acid specific protease-1 (caspase-1) and Gasdermin D (GSDMD), NOD like receptor protein 3 (NLRP-3), thioredoxin interacting proteins (TXNIP), IL-18 and IL-1β. The expression of circRNA-SCAF8, miR-93-5p and TXNIP was detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Fluorescence in situ hybridization (FISH) was used to locate circRNA-SCAF8 and miR-93-5p. Dual luciferase assay was used to verify the targeted regulatory relationship between miR-93-5p and upstream and downstream molecules.

RESULTS

Compared with the RNA control group, the cell survival rate of circRNA-SCAF8 inhibition group and miR-93-5p overexpression group increased (both P<0.01), the pyroptosis decreased (both P<0.01), and the expressions of pyroptosis-related factors such as TXNIP, NLRP-3, caspase-1, GSDMD, ASC, IL-18 and IL-1β were significantly decreased (all P<0.05). The expression of miR-93-5p was significantly increased after inhibition of circRNA-SCAF8 (P<0.01), and the expression of circRNA-SCAF8 tended to decrease after overexpression of miR-93-5p, but with no statistical significance (P>0.05). Dual luciferase assay showed that miR-93-5p downre-gulated circRNA-SCAF8 expression by binding to the 3 ´ UTR region of circRNA-SCAF8, and miR-93-5p downregulated TXNIP expression by binding to the 3 ´ UTR region of TXNIP. FISH showed that circRNA-SCAF8 and miR-93-5p were both located in the cytoplasm and were highly associated in the cells. qRT-PCR showed that the relative expression of TXNIP increased or decreased after overexpression or inhibition of miR-93-5p compared with the RNA control group, respectively (both P<0.05), suggesting that miR-93-5p could regulate TXNIP gene expression.

CONCLUSIONS

CircRNA-SCAF8/miR-93-5p/TXNIP axis is involved in the regulation of pyroptosis in HUVECs under high glucose.

25-hydroxyvitamin D3 inhibits oxidative stress and ferroptosis in retinal microvascular endothelial cells induced by high glucose through down-regulation of miR-93

BACKGROUND

The decrease of vitamin D plays a critical role in diabetes mellitus (DM)-induced oxidative stress and vascular endothelial injury. Therefore, we investigated the effect and mechanism of 25-hydroxyvitamin D3 (25 (OH) D3) on oxidative stress and ferroptosis induced by high glucose in human retinal microvascular endothelial cells (hRMVECs). And the objective of this paper was to propose a new strategy for the prevention and treatment of diabetic retinopathy (DR).

METHODS

First, hRMVECs were transfected with mimics NC or miR-93. After that, cells were treated with 100 nM / 500 nM 25 (OH) D3 and then cultured in a high glucose (30 mM) environment. Subsequently, qRT-PCR was employed to detect the expression level of miR-93; CCK-8 for the proliferation of cells in each group; biochemical tests for the level of intracellular reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH) and ferrous ion (Fe²⁺); and Western blot for the expression of ferroptosis-related proteins glutathione peroxidase 4 (GPX4) and SLC7A11).

RESULTS

Under a high glucose environment, 25 (OH) D3 at 100 nM/500 nM could significantly promote the proliferation of hRMVECs, remarkably decrease the level of intracellular ROS/MDA, and up-regulate the level of GSH. Besides, 25 (OH) D3 greatly reduced Fe²⁺ level in the cells while increased protein level of GPX4 and SLC7A11. Subsequently, we found that high glucose induced miR-93 expression, while 25 (OH) D3 markedly decreased high glucose-induced miR-93 overexpression. Furthermore, overexpression of miR-93 inhibited the functions of 25 (OH) D3 by activating ROS (ROS and MDA were up-regulated while GSH was down-regulated) and inducing Fe²⁺ (Fe²⁺ level was up-regulated while GPX4 and SLC7A11 level was down-regulated) in cells.

CONCLUSION

25 (OH) D3 may inhibit oxidative stress and ferroptosis in hRMVECs induced by high glucose via down-regulation of miR-93.

Faecalibacterium prausnitzii Improves Lipid Metabolism Disorder and Insulin Resistance in Type 2 Diabetic Mice

Purpose: Additional effective therapeutic strategies for Type 2 diabetes (T2D) patients are urgently needed. Gut microbiota plays an important role in T2D development and is a promising treatment strategy for T2D patients. Faecalibacterium prausnitzii (F. prausnitzii) is regarded as one of the most important bacterial indicators for a healthy gut, but the mechanisms of its anti-diabetic properties are still unclear. Methods and Results: The abundance of F. prausnitzii in feces of patients with T2D was detected by using qPCR. The effects of F. prausnitzii on glucose homeostasis, insulin resistance (IR), dyslipidemia, hepatic steatosis and inflammation were investigated in type 2 diabetic (T2D) db/db mice. We also investigated F. prausnitzii in people. Our results showed that the abundance of F. prausnitzii was significantly lower in T2D patients compared to healthy subjects. In T2D mice, we found that F. prausnitzii treatment significantly decreased fasting blood glucose and IR index, indicating improved glucose intolerance as well as IR. Furthermore, based on evaluation of lipid-regulating enzyme activities and proinflammatory cytokine levels, F. prausnitzii was not only able to improve inflammation in both adipose tissue and liver, but also ameliorate hepatic steatosis through inhibiting the activity of hepatic lipogenic enzymes. Conclusion: These results suggested that F. prausnitzii might serve as a therapeutic option for T2D by improved IR, lipid metabolism and inflammation.

Experimental Approaches to Diabetes Mellitus

One of the most common health problems today, diabetes is a serious, chronic, and complex disease characterized by high blood glucose levels. Nowadays, experimental diabetes models are being developed to study existing diabetes in depth, to improve diabetes medications, or to develop new medications. The protocols developed to date to create an experimental diabetes model are finalized in different time intervals and depending on various factors. With these models, which can be designed in vivo and in vitro, a picture similar to type 1 and type 2 diabetes can be created. In this review, we aimed to present the methodology, advantages, and disadvantages of all currently used experimental diabetes models in the light of current literature.

CircRNA hsa_circ_0071336 is associated with type 2 diabetes through targeting the miR-93-5p/GLUT4 axis

Glucose transporter 4 (GLUT4) is a dominant regulator of whole-body glucose homeostasis. Accumulating evidence has shown that circular RNAs (circRNAs) play significant roles in the pathogenesis of disease. The aim of the present study was to identify the circRNA that can be used as a novel biomarker for type 2 diabetes (T2D) through regulating GLUT4. Based on previous microarray analysis comparing T2D cases and healthy controls, hsa_circ_0071336, which was predicted to be a regulator of GLUT4 by acting as a competitive endogenous RNAs (ceRNA) to sponge miR-93-5p, was selected for further validation. The clinical significance of circulating hsa_circ_0071336 was investigated in a large independent cohort. The results showed that circulating hsa_circ_0071336 was significantly downregulated in blood in T2D and had a high diagnostic accuracy for discriminating T2D and impaired fasting glucose (IFG) from healthy controls. Low expression of circ_0071336 was an independent predictor of T2D, IFG and insulin resistance. A luciferase reporter assay and western-blot analysis indicated that miR-93-5p was a direct target of hsa_circ_0071336, and miR-93-5p may negatively regulate the expression of GLUT4. The expression levels of hsa_circ_007136 were negatively related to miR-93-5p expression and positively correlated with the mRNA expression of GLUT4 in adipose tissues. In conclusion, hsa_circRNA_0071336 can be considered as a potential novel and stable biomarker for T2D and its early detection. hsa_circ_0071336 regulates the GLUT4 expression by sponging miR-93-5p and maybe involved in the pathogenesis of T2D. These findings may unveil new targets for the prevention, diagnosis and treatment of T2D.

Transcriptome analysis to reveal the mechanism of the effect of Echinops latifolius polysaccharide B on palmitate-induced insulin-resistant

Hepatic insulin resistance is a crucial pathological process in type 2 diabetes mellitus (T2DM) associated with visceral adiposity and metabolic disorders. Echinops latifolius polysaccharide B (ETPB), a polysaccharide extracted from Echinops latifolius Tausch, increases insulin sensitivity in the high-fat diet-fed and STZ induced SD rat model and even prevented hepatic metabolic disorders. However, the mechanism by which ETPB improves carbohydrate and lipid metabolisms in the liver with insulin resistance remains largely unknown. In the present work, an lnsulin resistance cell model (IR-HepG2) was established. Glucose consumption, glycogen content, triglycerides (TG), and free fatty acids (FFAs) levels were detected. The result revealed that the intervention of ETPB significantly increased glucose consumption and glycogen synthesis and reduced FFAs and TG production in IR-HepG2 cells. Further, we also employed RNA-seq to identify differentially expressed miRNAs (DEMs) and mRNAs (DEGs) with a fold change of ≥ 1.5 and p-value of <0.05. Finally, we identified 1028, 682, 382, 1614, 519 and 825 DEGs, and 71, 113, 94, 68, 52 and 38 DEMs in different comparisons, respectively. Based on a short time-series expression miner (STEM) analysis, six profiles were chosen for further analysis. Seventeen insulin resistance-associated dynamic DEGs were identified during ETPB stimulation. Based on these dynamic DEGs, the related miRNAs were acquired from DEMs, and an integrated miRNA-mRNA regulatory network was subsequently constructed. Besides, some DEGs and DEMs were validated using qPCR. This study provides transcriptomic evidence of the molecular mechanism involved in HepG2 insulin resistance, leading to the discovery of miRNA-based target therapies for ETPB.

Taxifolin and Sorghum Ethanol Extract Protect against Hepatic Insulin Resistance via the miR-195/IRS1/PI3K/AKT and AMPK Signalling Pathways

This study aimed to evaluate the effects of taxifolin and sorghum ethanol extract on free fatty acid (FFA)-induced hepatic insulin resistance. FFA treatment decreased glucose uptake by 16.2% compared with that in the control, whereas taxifolin and sorghum ethanol extract increased the glucose uptake. Additionally, taxifolin and sorghum ethanol extract increased the expression of p-PI3K, p-IRS1, p-AKT, p-AMPK, and p-ACC in FFA-induced hepatocytes. Furthermore, FFA treatment increased the expression of miR-195. However, compared with the FFA treatment, treatment with taxifolin and sorghum ethanol extract decreased miR-195 expression in a dose-dependent manner. Taxifolin and sorghum ethanol extract enhanced p-IRS1, p-PI3K, p-AMPK, p-AKT, and p-ACC expression by suppressing miR-195 levels in miR-195 mimic- or inhibitor-transfected cells. These results indicate that taxifolin and sorghum ethanol extract attenuate insulin resistance by regulating miR-195 expression, which suggests that taxifolin and sorghum ethanol extract may be useful antidiabetic agents.