MiRNA-27a mediates insulin resistance in 3T3-L1 cells through the PPARγ

Experimental cell models of insulin resistance: overview and appraisal

Insulin resistance, a key factor in the development of type 2 diabetes mellitus (T2DM), is defined as a defect in insulin-mediated control of glucose metabolism in tissues such as liver, fat and muscle. Insulin resistance is a driving force behind various metabolic diseases, such as T2DM, hyperlipidemia, hypertension, coronary heart disease and fatty liver. Therefore, improving insulin sensitivity can be considered as an effective strategy for the prevention and treatment of these complex metabolic diseases. Cell-based models are extensively employed for the study of pathological mechanisms and drug screening, particularly in relation to insulin resistance in T2DM. Currently, numerous methods are available for the establishment of in vitro insulin resistance models, a comprehensive review of these models is required and can serve as an excellent introduction or understanding for researchers undertaking studies in this filed. This review examines and discusses the primary methods for establishing and evaluating insulin resistance cell models. Furthermore, it highlights key issues and suggestions on cell selection, establishment, evaluation and drug screening of insulin resistance, thereby providing valuable references for the future research efforts.

BACE1 inhibition via miR-6838-5p overexpression inhibits insulin resistance and the immune response in HFD-induced obesity in mice model

CONTEXT

Obesity is a chronic inflammatory disorder, which promotes the progression of metabolic disorders. MicroRNA (miR)-6838-5p is dysregulated and participates in the progression of several disorder models.

OBJECTIVE

To explore the role and mechanism of miR-6838-5p in insulin resistance.

METHODS

Mice were fed with high-fat diet (HFD) to construct an obesity animal model. The role of miR-6838-5p was evaluated by insulin tolerance test (ITT), glucose tolerance test (GTT), homeostasis model assessment of insulin resistance (HOMA-IR) analysis, enzyme-linked immunosorbent assay (ELISA) and western blot assays. The potential target of miR-6838-5p was screened through the starBase online website and confirmed by the luciferase assay.

RESULTS

HFD supply induced a prominent increase in the body weight, white adipose tissue (WAT) weight, the area under the curve (AUC) of GTT and ITT, HOMA-IR, the serum level of insulin and the serum concentrations and relative protein levels of interleukin (IL)-1β, IL-6 and monocyte chemoattractant protein-1 (MCP-1) accompanied with reduced levels of IL-10 in mice. The level of miR-6838-5p was reduced in HFD-fed mice. Upregulation of miR-6838-5p partly reversed the above-mentioned indicators. Moreover, miR-6838-5p directly targeted to β-site amyloid precursor protein cleaving enzyme1 (BACE1) and negatively regulated the BACE1 expression. Downregulation of BACE1 improved insulin sensitivity and inflammatory mediators release involving in AKT/GSK3β signaling pathway in HFD-fed mice. Besides, overexpression of BACE1 counteracted the depressant role of miR-6838-5p overexpression in insulin resistance and inflammatory factors release in HFD-fed mice.

CONCLUSION

MiR-6838-5p/BACE1 axis regulated insulin resistance and inflammatory factors release in HFD-fed mice.

Astragaloside IV Regulates Insulin Resistance and Inflammatory Response of Adipocytes via Modulating CTRP3 and PI3K/AKT Signaling

INTRODUCTION

Emerging evidence showed that adipocytes are important regulators in controlling insulin resistance in type 2 diabetes mellitus (T2DM). So far, compounds isolated from natural plants have been widely studied for their roles in alleviating T2DM-associated complications. This work evaluated the actions of astragaloside IV (AS-IV) on insulin resistance and inflammatory biomarker expression in adipocytes and explored the potential mechanisms.

METHODS

Glucose consumption of the adipocytes was determined by a glucose assay kit; the mRNA expression levels of glucose transporter type 4 (GLUT-4), interleukin-6 (IL-6), TNF-α and C1q tumor necrosis factor-related protein 3 (CTRP3) were measured by quantitative real-time PCR (qRT-PCR); the protein levels were determined by western blot assay and enzyme-linked immunosorbent assay.

RESULTS

AS-IV concentration-dependently increased glucose consumption in the insulin resistance adipocytes. Further qRT-PCR results showed that AS-IV concentration-dependently reduced adipocyte IL-6 and TNF-α expression. Moreover, GLUT-4 expression in adipocytes was also significantly upregulated by AS-IV. Furthermore, we found that AS-IV concentration-dependently increased CTRP3 expression in adipocytes. CTRP3 silence decreased glucose consumption, upregulated IL-6 and TNF-α expression and downregulated GLUT-4 mRNA expression in 200 µM AS-IV-treated adipocytes. Moreover, AS-IV treatment enhanced the activity of phosphoinositide 3-kinase (PI3K)/AKT signaling in adipocytes, which was markedly attenuated by CTRP3 silencing. Importantly, inhibition of PI3K/AKT signaling also attenuated AS-IV induced an increase in glucose consumption and GLUT-4 expression and a decrease in IL-6 and TNF-α expression of adipocytes.

CONCLUSIONS

Collectively, our data indicated that AS-IV attenuated insulin resistance and inflammation in adipocytes via targeting CTRP3/PI3K/Akt signaling.