Increased protein aggregation in Zucker Diabetic Fatty rat brain:identification of key mechanistic targets and the therapeutic application of hydrogen sulfide

Background: Diabetes and particularly high blood glucose levels are implicated in neurodegeneration. One of the hallmarks of neurodegeneration is protein aggregation. We investigated the presence of protein aggregation in the frontal brain of Zucker diabetic fatty (ZDF) rats, an animal model for diabetes. Further, the effect of NaHS in suppressing protein aggregation in cultured brain slices from ZDF was assessed. Results: The levels of protein synthesis, protein/gene expression, autophagy and anti-oxidant defense were evaluated in ZDF and control (Lean) brains. Compared to Lean, ZDF brains displayed a significant increase in protein aggregates, p-tau, fibronectin expression and protein glycosylation. Increased phosphorylation of mTOR and S6 ribosomal protein in ZDF indicated higher protein synthesis, while the increase in ubiquitinated proteins and LC3-I in ZDF brains accompanied by lower LC3-II expression and LC3-II/LC3-I levels indicated the blockage of proteolytic pathways. CBS (cystathionine beta synthase) protein and mRNA expression and thiol group levels in ZDF brains were lower compared to Lean. ZDF brains show a higher level of reactive oxygen species. In vitro NaHS treatment normalized proteostasis while counteracting oxidative stress. Conclusion: Our data demonstrate increased protein synthesis and aggregation in the diabetic ZDF rat brain, which was reversible by NaHS treatment. This is the first report on the potential use of NaHS as a novel strategy against protein aggregation in diabetic brain

Numerical simulation of wave generation in a tank by wall and floor oscillation

Tsunamis occur every year in different seas and oceans around the world. These waves propagate at high speeds in various directions and, if they reach the shore, cause irreparable damage to these areas and their structures and facilities. Therefore, understanding this complex phenomenon and predicting its behavior can reduce the damages. In the present study, numerical simulation studies of the tsunami phenomenon were carried out. The purpose of the study was to predict the tsunami wave characteristics when reaching the coastal area. The use of numerical simulation greatly reduces the cost of laboratory work and can also be used for complex geometries and models. The tsunami waves were considered as viscous fluid by Navier-Stokes equations for shallow water as governing equations with fluid volume fractionation method for simulating water surface in software. Wave generation was created by simulating a tank that fluctuates once to its left wall and once to its bottom. This work was carried out by Fluent software. In the following, the influence of shaking side wall angles on the generated waves is investigated. The simulation results show a significant increase in wave height due to the oscillating wall angle. The effects of the oscillating bottom wall have also been studied. In this thesis, the method of producing and propagating tsunami waves is described and the equations are defined. Also, since the most important issue in dealing with this phenomenon is their control, a method for controlling tsunami waves is presented in this thesis. Finally, a multi-phase method is used to simulate the movement of waves in a tank with a tremor wall. Finally, the obtained results have been compared to the analytical results by Green equation method and there are good agreements between them. The results showed that there is no change in wave height at distant points and with the oblique wall obliquity being increased by 30 degrees, the wave production increases. In addition, the flow and pressure lines also become almost horizontal

Metformin Improves Endothelial Function and Reduces Blood Pressure in Diabetic Spontaneously Hypertensive Rats Independent from Glycemia Control: Comparison to Vildagliptin

Metformin confers vascular benefits beyond glycemia control, possibly via pleiotropic effects on endothelial function. In type-1-diabetes-mellitus (T1DM-)patients metformin improved flow-mediated dilation but also increased prostaglandin(PG)-F-2 alpha, a known endothelial-contracting factor. To explain this paradoxical finding we hypothesized that metformin increased endothelial-vasodilator mediators (e.g. NO and EDHF) to an even larger extent. Spontaneously-hypertensive-rats (SHR) display impaired endothelium-dependent relaxation (EDR) involving contractile PGs. EDR was studied in isolated SHR aortas and the involvement of PGs, NO and EDHF assessed. 12-week metformin 300 mg/kg/day improved EDR by up-regulation of NO and particularly EDHF; it also reduced blood pressure and increased plasma sulphide levels (a proxy for H2S, a possible mediator of EDHF). These effects persisted in SHR with streptozotocin (STZ)-induced T1DM. Vildagliptin (10 mg/kg/day), targeting the incretin axis by increasing GLP-1, also reduced blood pressure and improved EDR in SHR aortas, mainly via the inhibition of contractile PGs, but not in STZ-SHR. Neither metformin nor vildagliptin altered blood glucose or HbA(1c). In conclusion, metformin reduced blood pressure and improved EDR in SHR aorta via up-regulation of NO and particularly EDHF, an effect that was independent from glycemia control and maintained during T1DM. A comparison to vildagliptin did not support effects of metformin mediated by GLP-1

Differential Effects of Long Term FTY720 Treatment on Endothelial versus Smooth Muscle Cell Signaling to S1P in Rat Mesenteric Arteries

The sphingosine-1-phosphate (S1P) analog FTY720 exerts pleiotropic effects on the cardiovascular system and causes down-regulation of S1P receptors. Myogenic constriction is an important mechanism regulating resistance vessel function and is known to be modulated by S1P. Here we investigated myogenic constriction and vascular function of mesenteric arteries of rats chronically treated with FTY720. Wistar rats received FTY720 1mg/kg/daily for six weeks. At termination, blood pressure was recorded and small mesenteric arteries collected for vascular studies in a perfusion set up. Myogenic constriction to increased intraluminal pressure was low, but a sub-threshold dose of S1P profoundly augmented myogenic constriction in arteries of both controls and animals chronically treated with FTY720. Interestingly, endothelial denudation blocked the response to S1P in arteries of FTY720-treated animals, but not in control rats. In acute experiments, presence of FTY720 significantly augmented the contractile response to S1P, an effect that was partially abolished after the inhibition of cyclooxygenase (COX-)-derived prostaglandins. FTY720 down regulated S1P1 but not S1P2 in renal resistance arteries and in cultured human endothelial cells. This study therefore demonstrates the endothelium is able to compensate for the complete loss of responsiveness of the smooth muscle layer to S1P after long term FTY720 treatment through a mechanism that most likely involves enhanced production of contractile prostaglandins by the endothelium

Acute effects of FTY720 on S1P mediated contraction.

<p>Mesenteric arteries of control animals were pre-incubated with 10μM FTY720 for 30 minutes before a dose effect curve to S1P (10nM-10μM) was constructed. S1P mediated contractions were normalized to maximal contractions to 60mM KCl. Pre-incubation with FTY720 (caused a leftward shift of the CR curve to S1P; this could be in part reversed by addition of indomethacin (10μM). n = 6 rats per group, 2 rings per rat. (*p<0.05 EC₅₀ FTY720 vs control).</p