[Regulation of miR-24 on vascular endothelial cell function and its role in the development of cardiovascular disease].

microRNA-24 (miR-24) belongs to miR-23~27~24 cluster. It is highly expressed in vascular endothelial cells (VECs), and plays an important role in the regulation of VECs specific gene expression. Recent studies indicate that miR-24 is involved in the regulation of VECs function such as proliferation, apoptosis, angiopoiesis, inflammation, and differentiation. The dysregulation of miR-24 is associated with dysfunction or even damage of VECs, and contributes to the development of cardiovascular disease. In this review, we summarized the molecular mechanisms of miR-24 in regulating VECs function, and its role and importance during the development of cardiovascular disease.

Roles of miRNA-24 in regulating endothelial nitric oxide synthase expression and vascular endothelial cell proliferation.

This study is to investigate the effect of miRNA-24 on endothelial nitric oxide synthase (eNOS) expression and vascular endothelial cell proliferation. Constructed high expression miRNA-24 plasmids were introduced into human umbilical vein endothelial cells (HUVECs) by liposome. Cell numbers were counted by a Hemocytometer, and cell proliferation was detected by MTT assay. The expression levels of eNOS and specificity protein 1 (Sp1) at mRNA and protein levels were, respectively, examined by real-time PCR, immunohistochemistry, and Western blotting. Compared with the control group, endothelial cell proliferation in miRNA-24 group significantly decreased by 64.24 % (6.53 ± 0.11 vs 18.26 ± 0.45, P < 0.01). The expression of eNOS at mRNA and protein levels in miRNA-24 group decreased by 64.21 % (0.34 ± 0.01 vs 0.95 ± 0.02, P < 0.05) and 82.86 % (0.072 ± 0.06 vs 0.42 ± 0.06, P < 0.05), respectively. Meanwhile, the expression of Sp1 at mRNA and protein levels in miRNA-24 group decreased by 64.64 % (0.35 ± 0.01 vs 0.99 ± 0.03, P < 0.05) and 60.34 % (0.23 ± 0.05 vs 0.58 ± 0.07, P < 0.05), respectively. In anti-miRNA-24 group, endothelial cell proliferation decreased by 33.46 % compared with the control group (12.15 ± 0.21 vs 18.26 ± 0.45, P < 0.01), while it increased by 46.25 % compared with the miRNA-24 group (12.15 ± 0.21 vs 6.53 ± 0.11, P < 0.01). The expression of eNOS at mRNA and protein levels in anti-miRNA-24 group decreased by 44.21 % (0.53 ± 0.04 vs 0.95 ± 0.02, P < 0.05) and by 30.95 %(0.29 ± 0.05 vs 0.42 ± 0.06, P < 0.05) compared with the control group, while it increased by 35.84 % (0.53 ± 0.04 vs 0.34 ± 0.01, P < 0.05) and by 75.17 % (0.29 ± 0.05 vs 0.072 ± 0.06, P < 0.05) compared with miRNA-24 group. The expression of Sp1 at mRNA and protein levels in ant-miRNA-24 group decreased by 36.36 % (0.63 ± 0.04 vs 0.99 ± 0.03, P < 0.05) and by 22.41 % (0.45 ± 0.06 vs 0.58 ± 0.07, P < 0.05) compared with the control group, while it increased by 44.44 % (0.63 ± 0.04 vs 0.35 ± 0.01, P < 0.05) and by 48.88 % (0.45 ± 0.06 vs 0.23 ± 0.05, P < 0.05) compared with miRNA-24 group. HUVECs proliferation and eNOS expression are significantly inhibited by miRNA-24. Sp1, which is regulated by miRNA-24, might act as one of the important factors involved in eNOS gene expression.

The effect of nitidine chloride on the proliferation and apoptosis of nasopharyngeal carcinoma cells.

PURPOSE: This study was conducted to investigate the effect of nitidine chloride (NC) on the proliferation and apoptosis of nasopharyngeal carcinoma cell line CNE1, CNE2, TWO3, and C666-1, and to explore its antitumor mechanism. METHODS: NC was dissolved in IMDM medium and cultured with nasopharyngeal carcinoma cell line CNE1, CNE2, TWO3 and C666-1. Cell morphology, cell proliferation, cell apoptosis, p53 mRNA and p53 protein levels were assessed. RESULTS: After incubation with NC for 24 h, typical apoptotic morphology was observed. NC inhibited the proliferation and induced apoptosis of all 4 cell lines in a time-dose dependent manner. p53 mRNA and p53 protein levels were significantly increased. CONCLUSIONS: NC inhibited proliferation and induced apoptosis of nasopharyngeal carcinoma cells with upregulation of p53 gene.

Role of microRNA-21 in regulating 3T3-L1 adipocyte differentiation and adiponectin expression.

MicroRNAs are endogenous small RNAs with a high degree of conservation, participating in a variety of vital activities. In present study, to explore the effect of microRNAs on 3T3-L1 adipocyte differentiation and adiponectin expression, the adipo-related microRNAs were screened and identified by micorRNA microarray. The highly expression plasmid of microRNA-21 with obvious expression up-regulation (miR-21) and its anti-sense (miR-21 inhibitor) were constructed and transfected into 3T3-L1 preadipocytes. The effect of miR-21 on 3T3-L1 adipocyte differentiation was observed, and the protein and mRNA expression level of adiponectin and AP-1 were analyzed. Results showed that, the expression profiles of microRNAs significantly changed during 3T3-L1 adipocyte differentiation. The expression of miR-21 was obviously up-regulated. miR-21 could significantly promote adipocyte differentiation, increase adiponectin mRNA and protein expression, while decrease AP-1 protein level. Meanwhil, miR-21 inhibitor blocked the effects of miR-21 mentioned above. The overexpression of AP-1 could absolutely reverse the stimulatory effect of miR-21 on adiponectin. miR-21 plays an important role in regulating adipocyte differentiation and adiponectin expression by inhibiting AP-1 expression.

Effect of trichosanthin on apoptosis and telomerase activity of nasopharyngeal carcinomas in nude mice.

PURPOSE: To evaluate the effect of trichosanthin (TCS) on telomerase activity and apoptosis in nasopharyngeal carcinoma cells implanted into nude mice. METHODS: Nude mice implanted with CNE1 and CNE2 nasopharyngeal carcinoma cell lines were randomly divided into 3 groups, including TCS group, control group (treatment with saline only), and cyclophosphamide (CTX) group. The weight of mice and the tumor volume were measured. The ultra-microstructural changes were observed by transmission electron microscope. Expression of Bcl-2 and Bax were investigated by immunohistochemistry. Apoptosis of CNE1 and CNE2 cells was determined by the TUNEL method, and telomerase activity by TRAP-ELISA. RESULTS: Compared with the normal control group (saline group), TCS significantly inhibited the growth of both CNE1 and CNE2 tumor cells. CTX also inhibited the growth of both CNE1 and CNE2 tumor cells but this inhibition was slightly slower compared with the TCS. CONCLUSION: TCS suppresses the growth of CNE1 and CNE2 cells lines in vivo. Its anticancer effects were associated with induction of apoptosis and, at least partially, with suppression of telomerase activity.

Intronic microRNA suppresses endothelial nitric oxide synthase expression and endothelial cell proliferation via inhibition of STAT3 signaling.

Intronic microRNA (miRNAs) suppressed the expression of endothelial nitric oxide synthase (eNOS) gene in endothelial cells (ECs). This study was to investigate the role of signal transducer and activator of transcription 3 (STAT3) in the regulation of eNOS expression and vascular EC proliferation by the intronic 27-nucleotide (nt) miRNA derived from the 27-base pair repeats in intron 4 of eNOS gene. A detectable level of the 27-nt miRNA was present in the control ECs. Overexpression of the 27-nt miRNA dramatically suppressed the expression of eNOS and STAT3 at both transcription and translation levels in ECs in association with significant inhibition of EC proliferation. Mutation of the 27-nt miRNA at the 3'-terminal region resulted in substantial reduction of the inhibitory effect of miRNA on eNOS and STAT3 expression, and EC proliferation. Overexpression of active STAT3 significantly reversed the inhibitory effect of the 27-nt miRNA on eNOS expression and EC proliferation. In summary, we demonstrated that the 27-nt intronic miRNA functioned as a negative regulator for the expression of its host gene eNOS and cell proliferation in ECs. The sequence in 3'-terminal region played a key role in the function of the 27-nt miRNA. The regulatory effect of the intronic miRNA on eNOS gene expression was associated with miRNA polymorphisms, and mediated through inhibition of STAT3 signaling in ECs.

Insulin regulation of hepatic gluconeogenesis through phosphorylation of CREB-binding protein.

Hepatic gluconeogenesis is essential for maintenance of normal blood glucose concentrations and is regulated by opposing stimulatory (cyclic adenosine monophosphate, cAMP) and inhibitory (insulin) signaling pathways. The cAMP signaling pathway leads to phosphorylation of cAMP response element-binding (CREB) protein, resulting in recruitment of the coactivators CREB-binding protein (CBP) and p300 and subsequent activation of gluconeogenesis. Insulin signaling leads to phosphorylation of CBP at serine 436, a residue near its CREB-interacting domain, but it is unknown whether this event modulates cAMP signaling. Here, we show in vitro and in 'knock-in' mice that a mutant CBP (S436A) is aberrantly recruited to CREB protein, resulting in inappropriate activation of gluconeogenesis in the fed state and glucose intolerance resulting from increased hepatic glucose production. We propose that insulin signaling may directly regulate many cAMP signaling pathways at the transcriptional level by controlling CBP recruitment.

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. 2. To investigate the role of miR-375 in adipocyte differentiation, we compared the miR-375 expression level between 3T3-L1 pre-adipocytes and adipocytes using miRNA microarray and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis. Furthermore, we evaluated the effects of overexpression or inhibition of miR-375 on 3T3-L1 adipocyte differentiation. 3. In the present study, we found that miR-375 expression was increased after induction of adipogenic differentiation. Overexpression of miR-375 enhanced 3T3-L1 adipocyte differentiation, as evidenced by its ability to increase mRNA levels of both CCAAT/enhancer binding protein-α (C/EBPα) and peroxisome proliferator-activated receptor-γ (PPARγ2), and induction of adipocyte fatty acid-binding protein (aP2) and triglyceride (TG) accumulation. Furthermore, we found overexpression of miR-375 suppressed phosphorylation levels of extracellular signal-regulated kinases 1/2 (ERK1/2). In contrast, anti-miR-375 increased ERK1/2 phosphorylation levels and inhibited mRNA expression of C/EBPα, PPARγ2 and aP2 in 3T3-L1 adipocyte, accompanied by decreased adipocyte differentiation. 4. Taken together, these data suggest that miR-375 promotes 3T3-L1 adipocyte differentiation, possibly through modulating the ERK-PPARγ2-aP2 pathway.

Ursolic Acid Inhibits Breast Cancer Metastasis by Suppressing Glycolytic Metabolism via Activating SP1/Caveolin-1 Signaling.

Breast cancer remains the most common malignancy and the leading causality of cancer-associated mortality among women worldwide. With proven efficacy, Oldenlandia diffusa has been extensively applied in breast cancer treatment in Traditional Chinese Medicine (TCM) for thousands of years. However, the bioactive compounds of Oldenlandia diffusa accounting for its anti-breast cancer activity and the underlying biological mechanisms remain to be uncovered. Herein, bioactivity-guided fractionation suggested ursolic acid as the strongest anti-breast cancer compound in Oldenlandia diffusa. Ursolic acid treatment dramatically suppressed the proliferation and promoted mitochondrial-mediated apoptosis in breast cancer cells while brought little cytotoxicities in nonmalignant mammary epithelial cells in vitro. Meanwhile, ursolic acid dramatically impaired both the glycolytic metabolism and mitochondrial respiration function of breast cancer cells. Further investigations demonstrated that ursolic acid may impair the glycolytic metabolism of breast cancer cells by activating Caveolin-1 (Cav-1) signaling, as Cav-1 knockdown could partially abrogate the suppressive effect of ursolic acid on that. Mechanistically, ursolic acid could activate SP1-mediated CAV1 transcription by promoting SP1 expression as well as its binding with CAV1 promoter region. More meaningfully, ursolic acid administration could dramatically suppress the growth and metastasis of breast cancer in both the zebrafish and mouse xenotransplantation models of breast cancer in vivo without any detectable hepatotoxicity, nephrotoxicity or hematotoxicity. This study not only provides preclinical evidence supporting the application of ursolic acid as a promising candidate drug for breast cancer treatment but also sheds novel light on Cav-1 as a druggable target for glycolytic modulation of breast cancer.

The Value of Geriatric Nutritional Risk Index in Evaluating Postoperative Complication Risk and Long-Term Prognosis in Elderly Colorectal Cancer Patients.

PURPOSE: The geriatric nutritional risk index (GNRI) has been reported as a useful tool for predicting the prognosis of many diseases; however, there is currently little research on the relationship between GNRI and outcomes in elderly colorectal cancer (CRC) patients. This study aimed to explore the value of GNRI in evaluating postoperative complication risk and long-term prognosis in elderly CRC patients. PATIENTS AND METHODS: The medical records of 230 CRC patients aged≥65 years who underwent surgery between January 2012 and December 2014 were retrospectively analyzed. Patients were divided into abnormal and normal GNRI groups by modified binary classification. Logistic regression analysis was used to evaluate the correlation between GNRI and complication risk. The Kaplan-Meier method with log-rank test was used to construct survival curves. The Cox proportional hazard model was used for univariate, multivariate and subgroup survival analyses to assess the relationship between GNRI and long-term prognosis. RESULTS: Multivariate logistic regression analysis showed that GNRI (p = 0.009, HR 2.280, 95% CI: 1.224-4.247) was an independent risk factor for postoperative complications in elderly CRC patients. Kaplan-Meier survival curves revealed that the abnormal GNRI group had significantly lower disease-free survival (DFS; p = 0.005) and overall survival (OS; p=0.007) than the normal GNRI group had, especially in TNM I stage. In multivariate survival analysis, GNRI was an independent prognostic factor for DFS (p = 0.003, HR 1.842, 95% CI: 1.229-2.760) and OS (p = 0.003, HR 1.852, 95% CI: 1.231-2.787). CONCLUSION: GNRI is a simple and effective tool for predicting the risk of postoperative complications and the long-term prognosis of postoperative elderly CRC patients and can provide a scientific basis for early nutrition interventions in elderly CRC patients.

Extracellular vesicles derived from microRNA-150-5p-overexpressing mesenchymal stem cells protect rat hearts against ischemia/reperfusion.

An intriguing area of research has demonstrated the ability of extracellular vesicles (EVs) as biological vehicles for microRNAs (miRNAs) transfer. Mesenchymal stem cells (MSCs) produce large amounts of EVs. Rat models of ischemia/reperfusion (I/R) were established to explore the expression profile of thioredoxin-interacting protein (TXNIP), which was then knocked-down to investigate its effects on myocardial remodeling, followed by detection on myocardial infarction size (MIS), myocardial collagen volume fraction (CVF) and cardiomyocyte apoptosis. MSCs-derived EVs carrying miR-150-5p were cultured with neonatal cardiomyocytes under hypoxia/hypoglycemia condition for in vitro exploration and intramyocardially injected into I/R rats for in vivo exploration. I/R-induced rats presented higher TXNIP levels and lower miR-150-5p levels, along with increased cardiomyocyte apoptosis. miR-150-5p in MSCs was transferred through EVs to cardiomyocytes, leading to suppressed myocardial remodeling, as reflected by smaller MIS and CVF and suppressed cardiomyocyte apoptosis. I/R-treated rats injected with MSCs-derived EVs containing miR-150-5p showed a reduction in myocardial remodeling associated with the downregulation of TXNIP, which may be clinically applicable for treatment of I/R.

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 insulinsensitive 3T3-L1 adipocytes and 3T3-L1 adipocytes rendered insulin resistant following treatment with high glucose (25mmol/L) and high insulin (1 mol/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 insulin­PI3-K signalling pathways. The findings provide information regarding a potentially new therapeutic strategy to control insulin resistance.

[Effect of 27nt-miRNA on the differentiation of mesenchymal stem cells into vascular smooth muscle cells].

To investigate the effect of 27nt-miRNA on the differentiation of mesenchymal stem cells into vascular smooth muscle cells. The highly expression plasmids of 27nt-miRNA and anti-27nt-miRNA, and negative control plasmids were constructed, packaged with lentivirus and transfected into human umbilical cord mesenchymal stem cells (hUCMSCs). Collagen IV was added to induce hUCMSCs differentiation into blood vessel smooth muscle cells (VSMCs). The cell viability was measured by MTT assay. The expression of SMA, SM22α at mRNA and protein levels was determined by RT-PCR, immunocytochemical staining and Western blotting. Compared with the negative control group, the viability of the 27nt-miRNA overexpression group was decreased by 20.48% (P<0.05), and the expression of SMA mRNA and SM22α mRNA and protein was significantly increased (P<0.05); the viability of Anti-27nt-miRNA group was increased 18.07% (P<0.05), and the expression of SMA mRNA and SM22α mRNA and protein was decreased (P<0.05). In summary, 27nt-miRNA promotes mesenchymal stem cells differentiation into vascular smooth muscle cells and inhibits cells viability.

Effects of rosiglitazone on the proliferation of vascular smooth muscle cell induced by high glucose.

AIM: To investigate the effects of the sensitizer rosiglitazone on the proliferation of vascular smooth muscle cell (VSMC) induced by high glucose administration. METHODS: VSMCs were isolated from rat thoracic aortas and cultured in 10% fetal bovine serum (FBS). VSMC proliferation was evaluated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and cell counting. The cell cycle was examined by flow cytometry. The protein expressions of proliferating cell nuclear antigen (PCNA) and matrix metalloproteinases-2 (MMP-2) were evaluated by Western blotting. MMP-2 mRNA expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and gelatinolytic activity was determined by zymography. RESULTS: Promoted VSMC proliferation significantly increased the number of VSMCs in the S phase, the expressions of PCNA and MMP-2, and MMP-2 activity, as well as decreased the proportion of VSMCs in the G(0)/G(1) phase. Rosiglitazone at a concentration of 10 mumol/L markedly inhibited glucose-induced VSMC proliferation (1.869 +/- 0.22 vs 0.820 +/- 0.15, P < 0.01). Concomitantly, rosiglitazone inhibited PCNA expression (0.96 +/- 0.07 vs 0.75 +/- 0.06, P < 0.05) and cell cycle progression from G(0)/G(1) to S phase (the proportion of VSMCs in the G(0)/G(1) and S phase were 69.6 +/- 3.96% vs 84.3 +/- 1.73% and 25.2 +/- 1.73% vs 10.1 +/- 1.42% (P < 0.01), respectively). Furthermore, rosiglitazone significantly decreased MMP-2 mRNA expression (0.98 +/- 0.08 vs 0.71 +/- 0.05, P < 0.05), protein expression (0.80 +/- 0.04 vs 0.64 +/- 0.03, P < 0.05) and MMP-2 activity (320 +/- 25% vs 248 +/- 21%, P < 0.05). CONCLUSION: Rosiglitazone significantly inhibited VSMC proliferation, at least in part by inhibiting high glucose-induced G(1)-->S phase transition, PCNA expression and MMP-2 synthesis.

Increased collagen deposition and elevated expression of connective tissue growth factor in human thoracic aortic dissection.

BACKGROUND: Thoracic aortic dissection (TAD) is characterized by dysregulated extracellular matrix. Little is known about the alterations of collagen and stimulators of collagen synthesis, eg, connective tissue growth factor (CTGF), in patients with TAD. In this study, we examined their roles in TAD. METHODS AND RESULTS: Surgical specimens of the aortic wall of TAD patients (n=10) and controls (n=10) were tested for collagen types I and III and CTGF expression. When compared with controls, protein levels of type I and III collagen and CTGF were significantly increased by 3.2-, 3.7-, and 5.3-fold, respectively (P<0.05 for all). Similar patterns were shown in mRNA levels of type Ialpha and Ialpha2 collagen and CTGF. Using immunohistochemistry and trichrome staining, we also observed elevated levels of collagen in the aortic media and adventitia. Treatment with recombinant human CTGF increased collagen synthesis in cultured aortic smooth muscle cells in a dose- and time-dependent fashion, in which expression of collagens increased from 506+/-108 counts per minute to 2764+/-240 cpm by 50 ng/mL CTGF, and from 30+/-43 cpm to 429+/-102 cpm at 48 hours. CONCLUSIONS: TAD patients exhibited significantly increased expression of aortic collagen types I and III as well as CTGF, which is likely to be responsible for the compromised aortic distensibility and systemic compliance. Because CTGF can increase collagen expression, CTGF may be a new target molecule in the pathogenesis and progression of TAD.

Effect of nuclear actin on endothelial nitric oxide synthase expression.

BACKGROUND: Previously, we showed that the 27nt repeat polymorphism in endothelial nitric oxide synthase (eNOS) intron 4 was associated with altered eNOS mRNA and protein levels, nitric oxide (NO) production and vascular disease risk; the 27-nt repeats had a cis-acting role in eNOS promoter function. In the present study, we investigated nuclear protein that binds the 27nt repeat and mediates eNOS expression. METHODS AND RESULTS: Using 5'-biotin-labeled 27nt DNA duplex and streptavidin-agarose beads pull-down assay and mass spectrometry, we identified that nuclear beta-actin was one of the major 27nt binding proteins. Using the pGL3 reporter vectors containing the 5x27nt repeats as an enhancer in an in vitro transcription assay, we found that exogenous beta-actin significantly increased reporter gene transcription efficiency. The beta-actin's upregulating effect was compromised when exogenous 27nt RNA duplex was added. Furthermore, the eNOS expression was reduced when beta-actin gene was silenced by specific siRNA, and actin overexpression upregulated eNOS expression >3-fold. CONCLUSIONS: Our data demonstrate that beta-actin as a transcription factor stimulates eNOS expression; and the transcriptional effect appears to be 27nt-dependent. Our findings represent a novel molecular mechanism regulating eNOS expression, which could potentially lead to discoveries of eNOS specific pharmaceutical agents, eg, active peptides, with clinical applications.

Spatial reorganization of glycogen synthase upon activation in 3T3-L1 adipocytes.

The dephosphorylation of glycogen synthase is a key step in the stimulation of glycogen synthesis by insulin. To further investigate the hormonal regulation of glycogen synthase activity, enzymatic localization in 3T3-L1 adipocytes was determined by immunocytochemistry and confocal microscopy. In basal cells, glycogen synthase and the protein phosphatase-1-glycogen-targeting subunit, protein targeting to glycogen (PTG), were diffusely distributed throughout the cell. Insulin treatment had no effect on PTG distribution but resulted in a reorganization of glycogen synthase into punctate clusters. Glycogen synthase aggregation was restricted to discrete cellular sites, presumably where glycogen synthesis occurred. Omission of extracellular glucose or substitution with 2-deoxy-glucose blocked the insulin-induced redistribution of glycogen synthase. Addition of the glycogenolytic agent forskolin after insulin stimulation disrupted the clusters of glycogen synthase protein, restoring the immunostaining pattern to the basal state. Conversely, adenoviral-mediated overexpression of PTG resulted in the insulin-independent dephosphorylation of glycogen synthase and a redistribution of the enzyme from the cytosolic- to glycogen-containing fractions. The effects of PTG on glycogen synthase activity were mediated by multisite dephosphorylation, which was enhanced by insulin and 2-deoxy-glucose, and required a functional glycogen synthase-binding domain on PTG. However, PTG overexpression did not induce distinct glycogen synthase clustering in fixed cells, presumably because cellular glycogen levels were increased more than 7-fold under these conditions, resulting in a diffusion of sites where glycogen elongation occurred. Cumulatively, these data indicate that the hormonal regulation of glycogen synthesis rates in 3T3-L1 adipocytes is mediated in part through changes in the subcellular localization of glycogen synthase.

Decreased expression of fibulin-5 correlates with reduced elastin in thoracic aortic dissection.

BACKGROUND: Thoracic aortic aneurysmal diseases are characterized by degeneration of elastin within the aortic wall. Although proteinases, such as matrix metalloproteinase, appear to contribute to elastin degradation, little is known about the role of elastic fiber assembly in such diseases. Fibulin-5 is an extracellular protein that is expressed in the vascular basement membrane and regulates elastic fiber assembly by microfibril machinery. In this study, we examined whether thoracic aortic dissection (TAD) is associated with abnormal fibulin-5 expression. METHODS: Intraoperative aortic samples were obtained from 21 patients with proximal aortic dissection. Control aortic tissue was obtained from 11 organ donors, heart transplant recipients, and patients undergoing coronary artery bypass. An in vitro culture of vascular smooth muscle cells was obtained from 2 TAD patients and 1 control subject. To evaluate elastin expression, we stained tissue sections with Verhoeff-Van Gieson stain. Fibulin-5 messenger RNA (mRNA) expression was determined by quantitative real-time reverse-transcriptase-polymerase chain reaction. RESULTS: Aortic fibulin-5 mRNA and elastin content were decreased in TAD patients, compared with controls (P=.001 and P=.02, respectively). Decreased fibulin-5 expression strongly correlated with decreased amounts and fragmentation of elastin in aortic samples from patients with TAD (r=0.83, P < .0001 and F=20.7, P < .0001 respectively). The fibulin-5 mRNA in aortic vascular smooth muscle cells collected from TAD demonstrated a 38% decrease in expression, compared with the control. CONCLUSIONS: Patients with proximal aortic dissection exhibited significantly decreased expression of aortic fibulin-5. Decreased fibulin-5 may contribute to the pathogenesis of aortic dissection by impairing elastic fiber assembly.