The association of SPARC with hypertension and its function in endothelial-dependent relaxation.

BACKGROUND AND AIMS: Secreted protein acidic and rich in cysteine (SPARC) is involved in the pathological processes of many metabolic diseases. However, studies on the relevance of SPARC to hypertension and its involvement in endothelial function are scarce. In this study, we aim to explore the relevance of SPARC to hypertension and investigate its role in endothelium-dependent relaxation (EDR). METHODS: 110 patients who met the criteria were recruited as participants. Serum SPARC concentrations were determined by Luminex assay. The correlation between SPARC levels and hypertension was analyzed. After treatment with SPARC ex vivo or in vivo, endothelial-dependent relaxation (EDR) was measured by wire myography. Western blotting was performed to detect the expression of proteins relevant to endothelial function. RESULTS: Our results showed that serum SPARC levels were significantly higher in the hypertensive group and were positively associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Functional results demonstrated that SPARC dramatically impaired EDR and induced the excess production of reactive oxygen species (ROS) in endothelial cells. Further experimental results confirmed that SPARC reduced angiotensin-converting enzyme 2 (ACE2) expression and ACE2 overexpression or activation completely abolished the impairing effect of SPARC on endothelial function. CONCLUSIONS: The present study reveals the correlation between elevated SPARC and hypertension and confirms its adverse effect on endothelial function, helping establish a comprehensive understanding of hypertension-related endothelial dysfunction in a new scope.

Realizing reversible phase transformation of shape memory ceramics constrained in aluminum.

Small-scale shape memory ceramics exhibit superior shape memory or superelasticity properties, while their integration into a matrix material and the subsequent attainment of their reversible tetragonal-monoclinic phase transformations remains a challenge. Here, cerium-doped zirconia (CZ) reinforced aluminum (Al) matrix composite is fabricated, and both macroscopic and microscopic mechanical tests reveal more than doubled compressive strength and energy absorbance of the composites as compared with pure Al. Full austenitization in the CZ single-crystal clusters is achieved when they are constrained by the Al matrix, and reversible martensitic transformation triggered by thermal or stress stimuli is observed in the composite micro-pillars without causing fracture in the composite. These results are interpreted by the strong geometric confinement offered by the Al matrix, the robust CZ/Al interface and the local three-dimensional particle network/force-chain configuration that effectively transfer mechanical loads, and the decent flowability of the matrix that accommodates the volume change during phase transformation.

Transforming growth factor (TGF)-ß1-induced miR-133a inhibits myofibroblast differentiation and pulmonary fibrosis.

Transforming growth factor (TGF)-ß1, a main profibrogenic cytokine in the progression of idiopathic pulmonary fibrosis (IPF), induces differentiation of pulmonary fibroblasts to myofibroblasts that produce high levels of collagen, leading to concomitantly loss of lung elasticity and function. Recent studies implicate the importance of microRNAs (miRNAs) in IPF but their regulation and individual pathological roles remain largely unknown. We used both RNA sequencing and quantitative RT-PCR strategies to systematically study TGF-ß1-induced alternations of miRNAs in human lung fibroblasts (HFL). Our data show that miR-133a was significantly upregulated by TGF-ß1 in a time- and concentration-dependent manner. Surprisingly, miR-133a inhibits TGF-ß1-induced myofibroblast differentiation whereas miR-133a inhibitor enhances TGF-ß1-induced myofibroblast differentiation. Interestingly, quantitative proteomics analysis indicates that miR-133a attenuates myofibroblast differentiation via targeting multiple components of TGF-ß1 profibrogenic pathways. Western blot analysis confirmed that miR-133a down-regulates TGF-ß1-induced expression of classic myofibroblast differentiation markers such as ɑ-smooth muscle actin (ɑ-SMA), connective tissue growth factor (CTGF) and collagens. miRNA Target Searcher analysis and luciferase reporter assays indicate that TGF-ß receptor 1, CTGF and collagen type 1-alpha1 (Col1a1) are direct targets of miR-133a. More importantly, miR-133a gene transferred into lung tissues ameliorated bleomycin-induced pulmonary fibrosis in mice. Together, our study identified TGF-ß1-induced miR-133a as an anti-fibrotic factor. It functions as a feed-back negative regulator of TGF-ß1 profibrogenic pathways. Thus, manipulations of miR-133a expression may provide a new therapeutic strategy to halt and perhaps even partially reverse the progression of IPF.

Comparative proteomic study reveals 17ß-HSD13 as a pathogenic protein in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is characterized by a massive accumulation of lipid droplets (LDs). The aim of this study was to determine the function of 17ß-hydroxysteroid dehydrogenase-13 (17ß-HSD13), one of our newly identified LD-associated proteins in human subjects with normal liver histology and simple steatosis, in NAFLD development. LDs were isolated from 21 human liver biopsies, including 9 cases with normal liver histology (group 1) and 12 cases with simple steatosis (group 2). A complete set of LD-associated proteins from three liver samples of group 1 or group 2 were determined by 2D LC-MS/MS. By comparing the LD-associated protein profiles between subjects with or without NAFLD, 54 up-regulated and 35 down-regulated LD-associated proteins were found in NAFLD patients. Among them, 17ß-HSD13 represents a previously unidentified LD-associated protein with a significant up-regulation in NAFLD. Because the 17ß-HSD family plays an important role in lipid metabolism, 17ß-HSD13 was selected for validating the proteomic findings and exploring its role in the pathogenesis of NAFLD. Increased hepatic 17ß-HSD13 and its LD surface location were confirmed in db/db (diabetic) and high-fat diet-fed mice. Adenovirus-mediated hepatic overexpression of human 17ß-HSD13 induced a fatty liver phenotype in C57BL/6 mice, with a significant increase in mature sterol regulatory element-binding protein 1 and fatty acid synthase levels. The present study reports an extensive set of human liver LD proteins and an array of proteins differentially expressed in human NAFLD. We also identified 17ß-HSD13 as a pathogenic protein in the development of NAFLD.

Palmitic acid acutely stimulates glucose uptake via activation of Akt and ERK1/2 in skeletal muscle cells.

Chronic exposure to saturated fatty acids can cause insulin resistance. However, the acute effects of fatty acids are not clear and need to be elucidated because plasma fatty acid concentrations fluctuate postprandially. Here, we present the acute effects of palmitate (PA) on skeletal muscle cells and their underlying molecular mechanisms. Immuno-fluorescence results showed that PA rapidly induced GLUT4 translocation and stimulated glucose uptake in rat skeletal muscle cell line L6. Phosphorylation of AMP-activated protein kinase (AMPK), Akt, and extracellular signal-related kinase1/2 (ERK1/2) was enhanced by PA in a time-dependent manner. Cell surface-bound PA was sufficient to stimulate Akt phosphorylation. The inhibitors of PI3 kinase (PI3K), AMPK, Akt, and ERK1/2 could decrease PA-induced glucose uptake, and PI3K inhibitor decreased AMPK, Akt, and ERK1/2 phosphorylation. Weakening AMPK activity reduced phosphorylation of Akt but not ERK1/2, and Akt inhibitor could not affect ERK1/2 activation either. Meanwhile, ERK1/2 inhibitors had no effect on Akt phosphorylation. Taken together, our data suggest that PA-mediated glucose uptake in skeletal muscle cells may be stimulated by the binding of PA to cell surface and followed by PI3K/AMPK/Akt and PI3K/ERK1/2 pathways independently.

Oleate blocks palmitate-induced abnormal lipid distribution, endoplasmic reticulum expansion and stress, and insulin resistance in skeletal muscle.

Pathological elevation of plasma fatty acids reduces insulin sensitivity. Although several regulation pathways have been reported, the molecular mechanisms of insulin sensitivity remain elusive, especially in skeletal muscle where most glucose is consumed. This study focuses on how two major dietary fatty acids affect insulin signaling in skeletal muscle cells. Palmitic acid (PA) not only reduced insulin-stimulated phosphorylation of Akt but also induced endoplasmic reticulum (ER) expansion and ER stress. Relieving ER stress using 4-phenyl butyric acid blocked PA-mediated protein kinase R-like ER kinase phosphorylation and ER expansion and reversed the inhibitory effect of PA on insulin-stimulated Akt phosphorylation. Importantly, oleic acid (OA) could also recover PA-reduced Akt phosphorylation and abolish both PA-mediated ER expansion and ER stress. The competition between these two fatty acids was further verified in rat skeletal muscle using venous fatty acid infusion. (3)H-labeled PA was converted mainly to active lipids (phospholipids and diacylglycerol) in the absence of OA, but to triacylglycerol in the presence of OA. Subcellular triacylglycerol and adipocyte differentiation-related protein from PA-treated cells cofractionated with the ER in the absence of OA but switched to the low-density fraction in the presence of OA. Taken together, these data suggest that the PA-mediated lipid composition and localization may cause ER expansion and consequently cause ER stress and insulin resistance in skeletal muscle.

Involvement of adenosine monophosphate-activated protein kinase in morphine-induced cardioprotection.

BACKGROUND: Adenosine monophosphate-activated protein kinase (AMPK) orchestrates the regulation of energy-generating and -consuming pathways, and protects the heart against ischemic injury and apoptosis. Recent progress shed light on various factors, including adiponectin, MIF, H11K, and metformin in the activation of AMPK. It is uncertain whether the activation of AMPK is contributed to cardioprotection of opioids. Here we show that morphine, an exogenous non-peptide opioid receptor agonist, can modulate the activation of the cardioprotective AMPK pathway during ischemia and exert anti-apoptotic effects through AMPK. METHODS: Isolated rat hearts were perfused on a constant pressure Langendorff system and subjected to 30 min of global ischemia followed by 60 min of reperfusion. The hearts received vehicles, morphine, a combination of morphine and compound C, a combination of morphine and STO609, a combination of morphine and BAPTA-AM at the onset of ischemia. Hemodynamics parameters, infarct size, release of intracellular creatine kinase, expression of AMPK, and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling staining were analyzed. RESULTS: Morphine significantly increased phosphorylation level of Thr172 site on AMPK, left ventricular function, and reduced infarct size as a percentage of the area at risk (IS/AAR from 63% ± 7% to 40% ± 5%), release of intracellular creatine kinase (from 319 ± 46 to 156 ± 42IU/60 min/gdw), apoptosis ratio (from 16% ± 2% to 5% ± 1.4%) during reperfusion in comparison with the control group. A inhibitor of AMPK, compound C abrogated phosphorylation of AMPK induced by morphine, the improvement in myocardial function, and the reduction of IS/AAR (58% ± 6%), release of intracellular creatine kinase (270 ± 40IU/60 min/gdw), apoptosis ratio (13% ± 1.5%). A Ca(2+)/calmodulin-dependent protein kinase kinase inhibitor STO609 and a chelator of intracellular Ca(2+) stores BAPTA-AM also abolished the cardioprotection of morphine. CONCLUSIONS: Morphine can ameliorate myocardial contractile dysfunction and limit infarct size following ischemia and reperfusion by a mechanism involving activation of AMPK, and activate AMPK by Ca(2+)-CaMKKß-dependent phosphorylation.