Hong-Yan Ling

CHANGES IN microRNA (miR) profile and effects of miR-320 in insulin-resistant 3T3-L1 adipocytes.

1 MicroRNAs (miRNAs) play essential roles in many biological processes. It is known that aberrant miRNA expression contributes to some pathological conditions. However, it is not known whether miRNAs play any role in the development of insulin resistance in adipocytes, a key pathophysiological link between obesity and diabetes. 2 To investigate the function of miRNAs in the development of insulin resistance, using miRNA microarray analysis we compared miRNA expression profiles between normal insulin‐sensitive 3T3‐L1 adipocytes and 3T3‐L1 adipocytes rendered insulin resistant following treatment with high glucose (25 mmol/L) and high insulin (1 µmol/L). Furthermore, adipocytes were transfected with specific antisense oligonucleotides against miRNA‐320 (anti‐miR‐320 oligo) and the effects on the development of insulin resistance were evaluated. 3 We identified 50 upregulated and 29 downregulated miRNAs in insulin‐resistant (IR) adipocytes, including a 50‐fold increase in miRNA‐320 (miR‐320) expression. Using bioinformatic techniques, the p85 subunit of phosphatidylinositol 3‐kinase (PI3‐K) was found to be a potential target of miR‐320. In experiments with anti‐miR‐320 oligo, insulin sensitivity was increased in IR adipocytes, as evidenced by increases in p85 expression, phosphorylation of Akt and the protein expression of the glucose transporter GLUT‐4, as well as insulin‐stimulated glucose uptake. These beneficial effects of anti‐miR‐320 oligo were observed only in IR adipocytes and not in normal adipocytes. 4 In conclusion, the miRNA profile changes in IR adipocytes compared with normal 3T3‐L1 adipocytes. Anti‐miR‐320 oligo was found to regulate insulin resistance in adipocytes by improving insulin–PI3‐K signalling pathways. The findings provide information regarding a potentially new therapeutic strategy to control insulin resistance.

MicroRNA-375 promotes 3T3-L1 adipocyte differentiation through modulation of extracellular signal-regulated kinase signalling

1. Adipocyte hypertrophy and hyperplasia are important processes in the development of obesity. To understand obesity and its associated diseases, it is important to elucidate the molecular mechanisms governing adipogenesis. MicroRNA‐375 has been shown to inhibit differentiation of neurites, and participate in the regulation of insulin secretion and blood homeostasis. However, it is unknown whether miR‐375 plays a role in adipocyte differentiation.

The physiological and pathophysiological roles of adipocyte miRNAs

MicroRNAs (miRNAs) are highly conserved, small, noncoding RNAs that regulate gene expression at the posttranscriptional level. Their actions affect numerous important biological processes, including adipocyte differentiation and function, sugar and lipid metabolism, and insulin production and secretion. Recent reports suggest miRNAs may also be involved in the pathogenic processes of obesity, diabetes, and insulin resistance. In this review, we summarize research progresses on adipocyte miRNAs and their physiological and pathological implications.

Angiopoietin-1 protects myocardial endothelial cell function blunted by angiopoietin-2 and high glucose condition

Aim:To evaluate the effects of angiopoietin-1 (Ang-1) on myocardial endothelial cell function under high glucose (HG) condition.Methods:Mouse heart myocardial endothelial cells (MHMECs) were cultured and incubated under HG (25 mmol/L) or normal glucose (NG, 5 mmol/L) conditions for 72 h. MTT was used to determine cellular viability, and TUNEL assay and caspase-3 enzyme linked immunosorbent assays were used to assay endothelial apoptosis induced by serum starvation. Immunoprecipitation and Western blot analysis were used to analyze protein phosphorylation and expression. Endothelial tube formation was used as an in vitro assay for angiogenesis.Results:Exposure of MHMECs to HG resulted in dramatic decreases in phosphorylation of the Tie-2 receptor and its downstream signaling partners, Akt/eNOS, compared to that under NG conditions. Ang-1 (250 ng/mL) increased Tie-2 activation, inhibited cell apoptosis, and promoted angiogenesis. Ang-1-mediated protection of endothelial function was blunted by Ang-2 (25 ng/mL).Conclusion:Ang-1 activates the Tie-2 pathway and restores hyperglycemia-induced myocardial microvascular endothelial dysfunction. This suggests a protective role of Ang-1 in the ischemic myocardium, particularly in hearts affected by hyperglycemia or diabetes.

Arecoline improves vascular endothelial function in high fructose-fed rats via increasing cystathionine-γ-lyase expression and activating K ATP channels

Aim:To investigate the effect of arecoline, a major component of betel nut, on vascular endothelial function in high fructose-fed rats and the potential mechanisms underlying the effect.Methods:Male Wistar rats were fed a high-fructose or control diet for 16 weeks. At the beginning of week 13, the rats were injected ip with low (0.5 mg·kg−1·d−1), medium (1.0 mg·kg−1·d−1) or high (5.0 mg·kg−1·d−1) doses of arecoline for 4 weeks. At the termination of the treatments, blood was collected, fasting blood glucose (FBG) and serum insulin (FSI) levels were measured, and insulin sensitivity index (ISI) was calculated. The thoracic aortas were isolated and aortic rings were prepared for studying ACh-induced endothelium-dependent vasorelaxation (EDVR). The mRNA and protein expression of cystathionine-γ-lyase (CSE) in the thoracic aortas was analyzed using RT-PCR and Western blot analysis, respectively.Results:In high fructose-fed rats, the levels of FBG and FSI were remarkably increased, whereas the ISI and the mRNA and protein expression of CSE were significantly decreased. ACh-induced EDVR in the aortic rings from high fructose-fed rats was remarkably reduced. These changes were reversed by treatment with high dose arecoline. Pretreatment of the aortic rings rings from high fructose-fed rats with the CSE inhibitor propargylglycine (10 mmol/L) or the ATP-sensitive potassium (KATP) channel blocker glibenclamide (10 mmol/L) abolished the restoration of ACh-induced EDVR by high dose arecoline. On the contrary, treatment with high dose arecoline significantly impaired ACh-induced EDVR in the aortic rings from control rats, and pretreatment with propargylglycine or glibenclamide did not cause further changes.Conclusion:Arecoline treatment improves ACh-induced EDVR in high fructose-fed rats, and the potential mechanism of action might be associated with increase of CSE expression and activation of KATP channels by arecoline.

MiRNA-375 promotes 3T3-L1 adipocyte differentiation via modulation of ERK signaling

1. Adipocyte hypertrophy and hyperplasia are important processes in the development of obesity. To understand obesity and its associated diseases, it is important to elucidate the molecular mechanisms governing adipogenesis. MicroRNA‐375 has been shown to inhibit differentiation of neurites, and participate in the regulation of insulin secretion and blood homeostasis. However, it is unknown whether miR‐375 plays a role in adipocyte differentiation.

MicroRNA-375 promotes 3T3-L1 adipocyte differentiation through modulation of extracellular signal-regulated kinase signalling: MicroRNA-375 and adipocyte differentiation

1. Adipocyte hypertrophy and hyperplasia are important processes in the development of obesity. To understand obesity and its associated diseases, it is important to elucidate the molecular mechanisms governing adipogenesis. MicroRNA‐375 has been shown to inhibit differentiation of neurites, and participate in the regulation of insulin secretion and blood homeostasis. However, it is unknown whether miR‐375 plays a role in adipocyte differentiation.