The Role of mRNA Translation Inhibitor Programmed Cell Death 4 (PDCD4) During Differentiation in Skeletal Muscle Cells

PDCD4 is a downstream substrate of mammalian/mechanistic target of rapamycin complex 1/ S6 ribosomal protein kinase 1 (mTORC1/ S6K1) pathway. It is known as an apoptotic protein, a tumour suppressor and an mRNA translation inhibitor. PDCD4 expression at the onset of differentiation was significantly greater than on Day 0, the time of change from growth to differentiation medium (p<0.05). This observation is corresponding to the mRNA expression (p<0.05). Using the pulse-chase technique, PDCD4 degradation rate was significantly different between Day 0 and Day 1 (p<0.05). Taking together, these imply that PDCD4 abundance during the onset of differentiation is likely regulated at the level of both protein synthesis and degradation. siRNA-mediated knockdown of PDCD4 led to a decrease in myogenic protein abundance during differentiation (p<0.05), and overexpression of PDCD4 stimulated differentiation (p<0.05). My study showed that the regulation of PDCD4 level may help in the management of muscle atrophy

Covariance stability and the 2008 financial crisis: the impact in the portfolio of the 10 biggest companies in BM&FBOVESPA between 2004 e 2012

This study's purpose is to analyse the covariance between the ten biggest participants of the BM&amp;FBovespa stock market to test the influence of the instability in the covariance between assets to the structure of a portfolio of investments of a portfolio composed by this assets. To acomplish that, we check the covariances between the daily returns of the 10 selected stocks before, during and after the 2008 financial crisis. The procedure of this research includes: (1) collection of returns of the selected stocks between 2004 and 2012; (2) the composition of the classical portfolio theory proposed by Markowitz(1952); and (3) the measurement of the effect of the unstable covariance between the 10 selected assets in the maintenance of the portfolio when controlling for return and risk preferences of a hipotetical investor. We find that asset correlations are impacted by the assets covariances that not stable in the whole time set for the study but are specialy sensitive in the financial crisis period. This means that both risk and return of the portfolio will change greatly if the weights are not recalculated from time to time. This suports the idea that portfolio theory might benefit from the development of stability weigthed techniques are developed

Bovine Insulin Filaments Induced by Reducing Disulfide Bonds Show a Different Morphology, Secondary Structure, and Cell Toxicity from Intact Insulin Amyloid Fibrils

AbstractAmyloid fibrils are associated with more than 20 diseases, including Alzheimer's disease and type II diabetes. Insulin is a 51-residue polypeptide hormone, with its two polypeptide chains linked by one intrachain and two interchain disulfide bonds, and has long been known to self-assemble in vitro into amyloid fibrils. We demonstrate here that bovine insulin forms flexible filaments in the presence of a reducing agent, Tris (2-carboxyethyl) phosphine. The insulin filaments, possibly formed due to partial reduction of S-S bonds in insulin molecules, differ from intact insulin fibrils in terms of their secondary structure. The insulin filaments were determined to have an antiparallel β-sheet structure, whereas the insulin fibrils have a parallel β-sheet structure. Of importance, the cell toxicity of the insulin filaments was remarkably lower than that of the insulin fibrils. This finding supports the idea that cell toxicity of amyloids correlates with their morphology. The remarkably low toxicity of the filamentous structure should shed new light on possible pharmacological approaches to the various diseases caused by amyloid fibrils

Differential effects of PDCD4 depletion on protein synthesis in myoblast and myotubes

BACKGROUND: Reduced muscle mass is a hallmark of metabolic diseases like diabetes and cancer. The mammalian (mechanistic) target of rapamycin complex 1/S6 kinase 1 (mTORC1/S6K1) pathway is critical to the regulation of muscle protein synthesis and mass but its mechanism of action is not completely understood. RESULTS: Using L6 myotubes, we characterized the regulation of programmed cell death 4 (PDCD4), a recently described substrate of S6K1. The abundance, but not Ser67 phosphorylation, of PDCD4 was sensitive to amino acid and serum deprivation: values in starved cells were 4.5X of control (P < 0.001). Refeeding had opposite effects. Growth factors, compared to amino acids, appeared more critical in regulating PDCD4 abundance. Furthermore, inhibition of mTORC1 or the proteasome prevented the refeeding-associated decrease in PDCD4 abundance. Amino acid and serum deprivation significantly increased PDCD4 binding to eIF4A (P < 0.05); this was reversed during refeeding. PDCD4 depletion by RNA interference had no significant effect on phenylalanine incorporation into myotube mixed proteins in control cells but further suppressed (30%) this measure in nutrient-deprived cells (P < 0.0005). This was not observed in myoblasts. In starved myotubes, PDCD4 depletion further reduced the association of eIF4G with eIF4E. CONCLUSION: Our data suggest that in myotubes, PDCD4 abundance is sensitive to nutritional manipulation in an mTORC1 and proteasome depended manner. Furthermore, the role of PDCD4 in regulating protein synthesis appears dependent on the developmental state of the cell

Amino acid-induced impairment of insulin sensitivity in healthy and obese rats is reversible

High-protein diets (HPDs) promote weight loss but other studies implicate these diets and their constituent amino acids (AAs) in insulin resistance. We hypothesized that AA-induced insulin resistance is a temporal and reversible metabolic event. L6 myotubes were serum deprived for 4 h and then incubated in AA and/or insulin (100 nmol/L). Another group of cells was incubated overnight in AA + insulin, starved again, and then reincubated with AA and insulin. Mammalian (mechanistic) target of rapamycin complex 1 (mTORC1) signaling and glucose uptake were then measured. Healthy or insulin-resistant rats were gavaged with leucine (0.48 g/kg) and insulin sensitivity was examined. In myotubes, incubation with AA and insulin significantly (P < 0.05) increased the phosphorylation of the mTORC1 substrate ribosomal protein S6 kinase 1 (S6K1, T389) and of insulin receptor substrate 1 (IRS-1, serine residues), but suppressed insulinstimulated glucose uptake by 40% (P < 0.01). These modifications were mTORC1-dependent and were reversible. In vivo, leucine gavage reversibly increased S6K1 phosphorylation and IRS-1 serine phosphorylation 5- to 12- fold in skeletal muscle and impaired insulin tolerance of glucose (P < 0.05) in lean rats. In insulin-resistant rats, the impairment of whole blood glucose and AA metabolism induced by leucine gavage (0.001 < P < 0.05) was more severe than that observed in lean rats; however, the impairment was reversible within 24 h of treatment. If these data are confirmed in long-term studies, it would imply that the use of leucine/HPD in treating metabolic diseases is unlikely to have lasting negative effects on insulin sensitivity

Evaluation of the Subchronic Toxicity of Dietary Administered Equisetum arvense in F344 Rats

Equisetum arvense, commonly known as the field horsetail, has potential as a new functional food ingredient. However, little information is available on its side effects, and the general toxicity of Equisetum arvense has yet to be examined in detail. In the present study, we evaluated the influence of administration in diet at doses of 0, 0.3, 1 and 3% for 13 weeks in male and female F344 rats. No toxicity was detected with reference to clinical signs, body weight, urinalysis, hematology and serum biochemistry data and organ weights. Microscopic examination revealed no histopathological lesions associated with treatment. In conclusion, the no-observed-adverse-effect level (NOAEL) for Equisetum arvense was determined to be greater than 3% in both sexes of F344 rat (males and females: >1.79 g/kg BW/day and >1.85 g/kg BW/day, respectively) under the conditions of the present study

Thoracoscopic esophagectomy was effective in a case of lower esophageal stenosis due to recurrence of achalasia after myotomy 40 years previously

When planning surgery for achalasia, it is important to plan for adequate myotomy and prevention of reflux. However, achalasia may recur if the procedure was inadequate or in patients with a long-term course. The present case is a 68-year-old woman who underwent myotomy of the lower esophageal sphincter 40 years ago, but recently reported difficulty in swallowing. Dilatation of the thoracic esophagus and stenosis of the abdominal esophagus were identified by examination, and the patient was diagnosed with recurrence of achalasia. After percutaneous endoscopic gastrostomy was performed to recover nutritional status, thoracoscopic esophagectomy was carried out. The patient'spost-operative course was uneventful and oral intake was enabled. At the time of writing, there has been no re-recurrence. There is no standard therapy for post-operative recurrence of achalasia. We believe that thoracoscopic esophagectomy for the recurrence of achalasia is a safe and minimally invasive alternative to conventional surgery

Thoracoscopic esophagectomy was effective in a case of lower esophageal stenosis due to recurrence of achalasia after myotomy 40 years previously

When planning surgery for achalasia, it is important to plan for adequate myotomy and prevention of reflux. However, achalasia may recur if the procedure was inadequate or in patients with a long-term course. The present case is a 68-year-old woman who underwent myotomy of the lower esophageal sphincter 40 years ago, but recently reported difficulty in swallowing. Dilatation of the thoracic esophagus and stenosis of the abdominal esophagus were identified by examination, and the patient was diagnosed with recurrence of achalasia. After percutaneous endoscopic gastrostomy was performed to recover nutritional status, thoracoscopic esophagectomy was carried out. The patient'spost-operative course was uneventful and oral intake was enabled. At the time of writing, there has been no re-recurrence. There is no standard therapy for post-operative recurrence of achalasia. We believe that thoracoscopic esophagectomy for the recurrence of achalasia is a safe and minimally invasive alternative to conventional surgery