Good glycaemic control reduces oxidation and glycation end-products in collagen of diabetic rats

Summary Blood glucose control plays a prominent role in the aetiology of diabetic complications. Recent data support the hypothesis that non-enzymatic pathways (glycation and oxidation) are involved in the pathogenesis of tissue damage in diabetes mellitus. In this study the level of pentosidine, a marker of glycation, and the intensity of collagen-linked fluorescence glycation (370/440 and 335/385 nm) and oxidation-related (356/460 and 390/460 nm), have been examined in spontaneously diabetic rats with good and poor glycaemic control. Pentosidine increased dramatically in rats with poor control, and slightly in those with good control. At the end of the study, after 6 months of diabetes, pentosidine levels were 13 ± 5 and 2.1 ± 0.5 pmol/mg collagen, respectively (control rats: 1.1 ± 0.1 pmol/mg collagen). A similar pattern was observed for both glycation or oxidation-related fluorescence. The group of rats with poor control always showed elevated average values when compared to rats with good control, with a relative increase of over 200 %. The results emphasize the role of good glycaemic control in preventing the growth of glycation or oxidation end-products in collagen. On comparison between the general mean level of all glycated haemoglobin and the mean pentosidine level of the three groups, a very good exponential correlation was found (r = 0.993, p < 0.001). The fluorescence values presented a less strong relationship, but a correlation with glycaemic control was still present. If the post-translational modifications of proteins play a leading role in the pathogenesis of complications it is possible to conclude that strict glycaemic control, obtained by accurate insulin therapy can prevent them by inhibiting the non-enzymatic modification of proteins and delaying their accumulation in collagen. The therapeutic implications are obvious. [Diabetologia (1996) 39: 1440–1447] Received: 23 March 1996 and in final revised form: 29 August 1996     

The impact of antiviral therapy for HCV on kidney disease: a systematic review and meta-analysis

BackgroundControversy persists about the role of hepatitis C as a risk factor for developing kidney disease in the general population. Some authors have evaluated the effect of antiviral therapy for HCV on the risk of kidney disease.Study Aims and DesignA systematic review of the published medical literature was performed to assess whether antiviral therapy for HCV has an independent impact on kidney survival in the adult general population. A random effects model was used to generate an overall estimate of the risk of kidney disease after anti-HCV therapy across the published studies. Meta-regression and stratified analysis were also carried out.ResultsFifteen studies were eligible (n = 356, 285 patients) and separate meta-analyses were conducted according to the outcome. Pooling studies based on viral responses (n = 7; 34,763 individual patients) demonstrated a relationship between sustained viral response and lower frequency of kidney disease; the overall estimate for adjusted risk of kidney disease was 2.50 (95% CI, 1.41; 4.41) (p = 0.0016) and between-study heterogeneity was found (p-value by Q test = 0.004). Aggregation of studies comparing treated vs untreated cohorts (n = 8, n = 333,312 patients) revealed an association between anti-HCV therapy and lower risk of kidney disease. The overall estimate for adjusted risk of kidney disease across the eight studies was 0.39 (95% CI, 0.25; 0.612) (p = 0.0001). Meta-regression showed that the effectiveness of antiviral therapy in reducing the frequency of kidney disease diminishes as cirrhosis (p = 0.02) and HBV infection (p = 0.0001) increase among HCV-infected individuals.ConclusionsAntiviral therapy for HCV lowers the risk of kidney disease among HCV-infected individuals. Studies to understand the mechanisms underlying this association are ongoing.     

Tau pathology modulates Pin1 post-translational modifications and may be relevant as biomarker

A prerequisite to dephosphorylation at Ser–Pro or Thr–Pro motifs is the isomerization of the imidic peptide bond preceding the proline. The peptidyl-prolyl cis/trans isomerase named Pin1 catalyzes this mechanism. Through isomerization, Pin1 regulates the function of a growing number of targets including the microtubule-associated tau protein and is supposed to be deregulated Alzheimer's disease (AD). Using proteomics, we showed that Pin1 is posttranslationally modified on more than 5 residues, comprising phosphorylation, N-acetylation, and oxidation. Although Pin1 expression remained constant, Pin1 posttranslational two-dimensional pattern was modified by tau overexpression in a tau-inducible neuroblastoma cell line, in our THY-Tau22 mouse model of tauopathy as well as in AD. Interestingly, in all of these systems, Pin1 modifications were very similar. In AD brain tissue when compared with control, Pin1 is hyperphosphorylated at serine 16 and found in the most insoluble hyperphosphorylated tau fraction of AD brain tissue. Furthermore, in all tau pathology conditions, acetylation of Pin1 may also contribute to the differences observed. In conclusion, Pin1 displays several posttranslational modifications, which are specific in tauopathies and may be useful as biomarker.     

Fabrication and statistical optimization of surface engineered PLGA nanoparticles for naso-brain delivery of ropinirole hydrochloride: in-vitro–ex-vivo studies

Ropinirole hydrochloride (RPN), a nonergot dopamine D₂-agonist used in the management of Parkinson’s disease, has poor oral bioavailability (52%) due to extensive hepatic metabolism. The intent of present research work was aimed at design and statistical optimization of RPN-loaded poly (lactic-co-glycolic acid) (PLGA)-based biodegradable nanoparticles (NPs) surface modified using natural emulsifier, vitamin E (d-α-tocopheryl polyethylene glycol 1000 succinate [TPGS]) for direct nose-to-brain delivery in order to avoid hepatic first-pass metabolism, and improve therapeutic efficacy with sustained drug release. RPN-NPs were prepared by modified nanoprecipitation technique and optimized using 2³ factorial design of experiment. The effect of polymer and emulsifier concentration was evaluated on particle size and entrapment efficiency (EE%). Formulation PL₆ was considered as desirable with highest EE% (72.3?±?6.1%), PS (279.4?±?1.8?nm), zeta potential (?29.4?±?2.6?mV), and cumulative drug diffusion of 96.43?±?3.1% in 24?h. The ANOVA results for the dependent variables demonstrated that the model was significant (p value?<?0.05) for response variables. Histopathological study of optimized batch (PL₆) demonstrated good retention of NPs with no severe signs of damage on the integrity of nasal mucosa. Differential scanning calorimetry revealed the absence of any chemical interaction between RPN, PLGA, and TPGS while SEM study confirmed spherical shape of optimized NPs. Accelerated stability studies of freeze-dried optimized batch demonstrated negligible change in the average PS and EE% after storage at 25?±?2?°C/60?±?5% (relative humidity (RH) for the period of three months. The promising results of optimized batch suggested practicability of investigated system for enhancement of bioavailability and brain targeting of CNS acting drugs like RPN.     

Modification of Polyurethane with Polyethylene Glycol–Corn Trypsin Inhibitor for Inhibition of Factor Xlla in Blood Contact

Abstract

In previous work using gold as a model substrate, we showed that modification of surfaces with poly(ethylene glycol) (PEG) and corn trypsin inhibitor (CTI) rendered them protein resistant and inhibitory against activated factor XII. Sequential attachment of PEG followed by CTI gave superior performance compared to direct attachment of a preformed PEG-CTI conjugate. In the present work, a sequential method was used to attach PEG and CTI to a polyurethane (PU) substrate to develop a material with applicability for blood-contacting medical devices. Controls included surfaces modified only with PEG and only with CTI. Surfaces were characterized by water contact angle and X-ray photoelectron spectroscopy. The surface density of CTI was in the range of a monolayer and was higher on the PU substrate than on gold reported previously. Biointeractions were investigated by measuring fibrinogen adsorption from buffer and plasma, factor XIIa inhibition and plasma clotting time. Both the PU–PEG surfaces and the PU–PEG–CTI surfaces showed low fibrinogen adsorption from buffer and plasma, indicating that PEG retained its protein resistance when conjugated to CTI. Although the CTI density was lower on PU–PEG–CTI than on PU modified only with CTI, PU–PEG–CTI exhibited greater factor XIIa inhibition and a longer plasma clotting time, suggesting that PEG facilitates the interaction of CTI with factor XIIa. Thus sequential attachment of PEG and CTI may be a useful approach to improve the thromboresistance of PU surfaces.     

Grafting antibiofilm polymer hydrogel film onto catheter by SARA SI-ATRP

Abstract

Catheters are widely used and play an important role in medicine. However, catheter-associated infection is prevalent even under stringent sterile conditions. Biofilms are formed when bacteria populate the surfaces of catheters. This makes the biofilm resistant to antibiotics. Hence, it is imperative for there to be an inherently antifouling and anti-bacterial catheter to mitigate the formation of biofilm. This paper aims to outline the synthesis of non-leachable anti-biofilm and anti-bacterial cationic film coatings through direct polymerization using supplemental activator and reducing agent surface initiated atom transfer radical polymerization (SARA SI-ATRP). Three crosslinked cationic coatings comprising of Diallyl dimethyl ammonium chloride (DADMAC), or ε-poly-L-lysine HCl methacrylic acid (EPL-MA) together with a crosslinker (polyethylene glycol dimethacrylate, PEGDMA) were investigated. These non-leachable covalently linked coatings with DADMAC can achieve more than 2 log reduction (99.0%) with Methicillin-resistant Staphylococcus aureus (MRSA) and 1.25 log reduction (94.4%) with Vancomycin resistant Enterococcus (VRE) in in vitro studies.     

Radio-frequency plasma treatment improves the growth and attachment of endothelial cells on poly(methyl methacrylate) substrates: implications in tissue engineering

The aim of this study was to improve the biocompatibility of poly(methyl methacrylate) (PMMA) substrates for possible applications in corneal prostheses or in micro-carrier cell culture systems. PMMA substrates were exposed to radio-frequency (RF) argon and nitrogen plasmas for 5 and 10 min each. The PMMA films were examined by Fourier transform infrared (FT-IR) spectroscopy, to characterize the surface changes after plasma exposure. Plasma treatment in general was found to decrease the water contact angle of PMMA, thus increasing its hydrophilicity. There was also an associated increase in the work of adhesion of plasma-treated PMMA substrates. PMMA substrates exhibited differential properties towards endothelial cell (CPA-47) growth. The untreated PMMA surface did not support endothelial growth, compared with both polystyrene (TCPS) and plasma-treated PMMA, while plasma (PL):PMMA exhibited growth rates slightly lower than the TCPS control, as assessed by [³H]thymidine incorporation profiles. The compatibility and growth supportive properties of PL: PMMA were further confirmed by an MTT assay, which showed preserved cellular viability and mitochondrial activity of the cells. Confocal microscopic visualization of cells with fluorescence-labeled vimentin showed normal organization of the cytoskeletal fibers, indicating appropriate attachment to the substrate. Cells growing on PL:PMMA maintained their functionality, as seen from Factor VIII expression. Taken collectively, the findings of this study point out the suitability of RF plasma treatment in inducing desirable changes in PMMA substrates, so as to improve their ability to support the growth and attachment of endothelial cells.     

Effects of O-GlcNAcylation on functional mitochondrial transfer from astrocytes

Mitochondria may be transferred from cell to cell in the central nervous system and this process may help defend neurons against injury and disease. But how mitochondria maintain their functionality during the process of release into extracellular space remains unknown. Here, we report that mitochondrial protein O-GlcNAcylation is a critical process to support extracellular mitochondrial functionality. Activation of CD38-cADPR signaling in astrocytes robustly induced protein O-GlcNAcylation in mitochondria, while oxygen-glucose deprivation and reoxygenation showed transient and mild protein modification. Blocking the endoplasmic reticulum – Golgi trafficking with Brefeldin A or slc35B4 siRNA reduced O-GlcNAcylation, and resulted in the secretion of mitochondria with decreased membrane potential and mtDNA. Finally, loss-of-function studies verified that O-GlcNAc-modified mitochondria demonstrated higher levels of neuroprotection after astrocyte-to-neuron mitochondrial transfer. Collectively, these findings suggest that post-translational modification by O-GlcNAc may be required for supporting the functionality and neuroprotective properties of mitochondria released from astrocytes.     

Diuretic-induced hyponatremia and osteoporotic fractures in patients admitted to the emergency department

Objective

Hyponatremia is a complication of diuretic treatment and has been recently identified as a novel factor associated with osteoporosis and fractures. The impact of diuretic-associated electrolyte disorders on osteoporotic fractures (OF) has rarely been studied systematically.

Design and setting

We conducted a study in patients presenting to the emergency department at the University Hospital Bern. In this retrospective case series analysis of prospectively gathered data, over a 2-year period we identified 10,823 adult (≥50 years) outpatients with a measured baseline serum sodium, at admission to the hospital. OF patients were compared to a control group without fractures using standard statistical methods.

Results

Four hundred and eighty (5%) patients had 547 OF. The OF group had a higher mean age (73 vs. 68 years, p < 0.0001), smaller proportion of men (37% vs. 58%, p < 0.0001), higher hospitalisation rate (83% vs. 62%, p < 0.0001) and longer hospital stay (8 vs. 6 days, p < 0.0001). Any diuretic agent (p < 0.0001), loop diurietics (p = 0.02), spironolactone (p = 0.02) and amiloride (p < 0.01) were used significantly more in OF patients, but not thiazides (p = 0.68). The prevalence of hyponatremia increased significantly (p < 0.0001) with the number of diuretics taken. Advanced age (odds ratio [OR] 1.04, p < 0.0001), hyponatremia (OR 1.46, p = 0.011) higher serum creatinine (OR 1.53, p = 0.0001), furosemide use alone (OR 1.40, p = 0.01) and co-treatment with amiloride (OR 2.22, p = 0.02) were associated with a higher risk for OF.

Conclusions

This study highlights the clinical association of hyponatremia during the use of certain diuretics (i.e. furosemide or in combination, i.e. amiloride) with an increased risk of osteoporosis associated fractures. Although evidence-based data is currently lacking a pragmatic approach concerning hyponatremia monitoring and correction appears reasonable in selected groups of patients.