Hydrochloride pioglitazone protects diabetic rats against podocyte injury through preserving glomerular podocalyxin expression

Pioglitazone Enhances β-Arrestin2 Signaling and Ameliorates Insulin Resistance in Classical Insulin Target Tissues

INTRODUCTION

Pioglitazone is a thiazolidinedione oral antidiabetic agent. This study aimed to investigate the effects of pioglitazone as insulin sensitizer on β-arrestin2 signaling in classical insulin target tissues.

METHODS

Experiments involved three groups of mice; the first one involved mice fed standard chow diet for 16 weeks; the second one involved mice fed high-fructose, high-fat diet (HFrHFD) for 16 weeks; and the third one involved mice fed HFrHFD for 16 weeks and received pioglitazone (30 mg/kg/day, orally) in the last four weeks of feeding HFrHFD.

RESULTS

The results showed significant improvement in the insulin sensitivity of pioglitazone-treated mice as manifested by significant reduction in the insulin resistance index. This improvement in insulin sensitivity was associated with significant increases in the β-arrestin2 levels in the adipose tissue, liver, and skeletal muscle. Moreover, pioglitazone significantly increased β-arrestin2 signaling in all the examined tissues as estimated from significant increases in phosphatidylinositol 4,5 bisphosphate and phosphorylation of Akt at serine 473 and significant decrease in diacylglycerol level.

CONCLUSION

To the best of our knowledge, our work reports a new mechanism of action for pioglitazone through which it can enhance the insulin sensitivity. Pioglitazone increases β-arrestin2 signaling in the adipose tissue, liver, and skeletal muscle of HFrHFD-fed mice.

Co-delivery of p38α MAPK and p65 siRNA by novel liposomal glomerulus-targeting nano carriers for effective immunoglobulin a nephropathy treatment

Glomerulonephritis related renal failure is a frequent cause of end-stage renal disease, and immunoglobulin A nephropathy (IgAN) is the most frequent type of primary glomerulonephritis. As damage induced by IgAN mostly attributes to inflammation responses, inhibiting inflammation in glomerulus can protect normal renal function and delay the onset of renal failure. Hence, reducing levels of p38 MAPK and p65 which are essential regulators in p38 MAPK and NF-κB related inflammation responses could be effective against IgAN. Here, we rationally designed and constructed size- and surface charge- dependent glomerulus-targeting liposomal nanoparticles which are loaded with both p38α MAPK and p65 siRNA. Experiments show that our nanoparticles successfully crossed fenestrated endothelium, accumulated in mesangial cells and endothelial cells, efficiently silenced p38α MAPK and p65 genes, and eventually alleviated proteinuria, inflammation and excessive extracellular matrix deposition in mouse IgAN models. This siRNA co-delivery system thus represents a promising treatment option for IgAN and offers a versatile platform for other glomerular problems. Our work also highlights a novel strategy of glomerulus-targeting and an encouraging therapeutic route for other inflammatory diseases.

Long noncoding RNA ENSRNOG00000037522 is involved in the podocyte epithelial‑mesenchymal transition in diabetic rats

Diabetic nephropathy (DN) is one of the most common complications associated with type I and II diabetes mellitus. Long noncoding RNAs (lncRNAs) have been implicated in various physiological and pathological processes, and recent evidence has demonstrated that they are involved in the process of the epithelial-mesenchymal transition (EMT). In the present study, the potential functions of lncRNA ENSRNOG00000037522 during the EMT process in DN were investigated. The results identified that the level of the lncRNA ENSRNOG00000037522 was significantly increased in kidney tissues collected from rats with streptozocin (STZ)-induced DN accompanied by impairment of the glomerular podocytes. It was further demonstrated that the silencing of lncRNA ENSRNOG00000037522 by small interfering RNA transfection partially restored the podocyte function. In addition, knockdown of lncRNA ENSRNOG00000037522 repaired the damage to the podocytes via regulating vimentin, podocalyxin-like 1 and nephrin expression. In conclusion, the current results demonstrated that lncRNA ENSRNOG00000037522 serves a pivotal role in the podocyte EMT in DN.

Pioglitazone Ameliorates Smooth Muscle Cell Proliferation in Cuff-Induced Neointimal Formation by Both Adiponectin-Dependent and -Independent Pathways

The aim of this study is to elucidate to what degree adiponectin is involved in TZD-mediated amelioration of neointimal formation. We investigated the effect of 3- or 8-weeks' pioglitazone on cuff-induced neointimal formation in adiponectin-deficient (APN-KO) and wild-type (WT) mice. Pioglitazone for 3 weeks reduced neointimal formation in the WT mice with upregulation of the plasma adiponectin levels, but failed to reduce neointimal formation in the APN-KO mice, suggesting that pioglitazone suppressed neointimal formation by adiponectin-dependent mechanisms. Pioglitazone for 3 weeks suppressed vascular smooth muscle cell (VSMC) proliferation and increased AdipoR2 expression in the WT mice. In vitro, globular adiponectin activated AMPK through both AdipoR1 and AdipoR2, resulting in the inhibition of VSMC proliferation. Interestingly, 8-weeks' pioglitazone was reduced neointimal formation in APN-KO mice to degree similar to that seen in the WT mice, suggesting that pioglitazone can also suppress neointimal formation via a mechanism independent of adiponectin. Pioglitazone for 8 weeks completely abrogated the increased VSMC proliferation, along with a reduction of cyclin B1 and cyclin D1 expressions and cardiovascular risk profile in the APN-KO mice. In vitro, pioglitazone suppressed these expressions, leading to inhibition of VSMC proliferation. Pioglitazone suppresses neointimal formation via both adiponectin-dependent and adiponectin-independent mechanisms.