Conversion from Tacrolimus to Cyclosporine A Improves Glucose Tolerance in HCV-Positive Renal Transplant Recipients

Background

Calcineurin-inhibitors and hepatitis C virus (HCV) infection increase the risk of post-transplant diabetes mellitus. Chronic HCV infection promotes insulin resistance rather than beta-cell dysfunction. The objective was to elucidate whether a conversion from tacrolimus to cyclosporine A affects fasting and/or dynamic insulin sensitivity, insulin secretion or all in HCV-positive renal transplant recipients.

Methods

In this prospective, single-center study 10 HCV-positive renal transplant recipients underwent 2h-75g-oral glucose tolerance tests before and three months after the conversion of immunosuppression from tacrolimus to cyclosporine A. Established oral glucose tolerance test-based parameters of fasting and dynamic insulin sensitivity and insulin secretion were calculated. Data are expressed as median (IQR).

Results

After conversion, both fasting and challenged glucose levels decreased significantly. This was mainly attributable to a significant amelioration of post-prandial dynamic glucose sensitivity as measured by the oral glucose sensitivity-index OGIS [422.17 (370.82–441.92) vs. 468.80 (414.27–488.57) mL/min/m2, p = 0.005), which also resulted in significant improvements of the disposition index (p = 0.017) and adaptation index (p = 0.017) as markers of overall glucose tolerance and beta-cell function. Fasting insulin sensitivity (p = 0.721), insulinogenic index as marker of first-phase insulin secretion [0.064 (0.032–0.106) vs. 0.083 (0.054–0.144) nmol/mmol, p = 0.093) and hepatic insulin extraction (p = 0.646) remained unaltered. No changes of plasma HCV-RNA levels (p = 0.285) or liver stiffness (hepatic fibrosis and necroinflammation, p = 0.463) were observed after the conversion of immunosuppression.

Conclusions

HCV-positive renal transplant recipients show significantly improved glucose-stimulated insulin sensitivity and overall glucose tolerance after conversion from tacrolimus to cyclosporine A. Considering the HCV-induced insulin resistance, HCV-positive renal transplant recipients may benefit from a cyclosporine A-based immunosuppressive regimen.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT02108301","term_id":"NCT02108301"}}NCT02108301     

Porphyrin binding and distortion and substrate specificity in the ferrochelatase reaction: the role of active site residues

The specific insertion of a divalent metal ion into tetrapyrrole macrocycles is catalyzed by a group of enzymes called chelatases. Distortion of the tetrapyrrole has been proposed to be an important component of the mechanism of metallation. We present the structures of two different inhibitor complexes: (1) N-methylmesoporphyrin (N-MeMP) with the His183Ala variant of Bacillus subtilis ferrochelatase; (2) the wild-type form of the same enzyme with deuteroporphyrin IX 2,4-disulfonic acid dihydrochloride (dSDP). Analysis of the structures showed that only one N-MeMP isomer out of the eight possible was bound to the protein and it was different from the isomer that was earlier found to bind to the wild-type enzyme. A comparison of the distortion of this porphyrin with other porphyrin complexes of ferrochelatase and a catalytic antibody with ferrochelatase activity using normal-coordinate structural decomposition reveals that certain types of distortion are predominant in all these complexes. On the other hand, dSDP, which binds closer to the protein surface compared to N-MeMP, does not undergo any distortion upon binding to the protein, underscoring that the position of the porphyrin within the active site pocket is crucial for generating the distortion required for metal insertion. In addition, in contrast to the wild-type enzyme, Cu²⁺-soaking of the His183Ala variant complex did not show any traces of porphyrin metallation. Collectively, these results provide new insights into the role of the active site residues of ferrochelatase in controlling stereospecificity, distortion and metallation.     

Refinement of a Quantitative Structure–Activity Relationship Model for Prediction of Cell-Penetrating Peptide Based Transfection Systems

Cell-penetrating peptide (CPP) based transfection systems (PBTS) are a promising class of drug delivery vectors. CPPs are short mainly cationic peptides capable of delivering cell non-permeant cargo to the interior of the cell. Some CPPs have the ability to form non-covalent complexes with oligonucleotides for gene therapy applications. In this study, we use quantitative structure–activity relationships (QSAR) , a statistical method based on regression data analysis. Here, an fragment QSAR (FQSAR) model is developed to predict new peptides based on standard alpha helical conformers and Assisted Model Building with Energy Refinement molecular mechanics simulations of previous peptides. These new peptides were examined for plasmid transfection efficiency and compared with their predicted biological activity. The best predicted peptides were capable of achieving plasmid transfection with significant improvement compared to the previous generation of peptides. Our results demonstrate that FQSAR model refinement is an efficient method for optimizing PBTS for improved biological activity.     

Cell-penetrating peptides split into two groups based on modulation of intracellular calcium concentration

Cell-penetrating peptides (CPPs) promote the uptake of different cargo molecules, e.g. therapeutic compounds, making the harnessing of CPPs a promising strategy for drug design and delivery. However, the internalization mechanisms of CPPs are still under discussion, and it is not clear how cells compensate the disturbances induced by peptides in the plasma membrane. In this study, we demonstrate that the uptake of various CPPs enhances the intracellular Ca(2+) levels in Jurkat and HeLa cells. The elevated Ca(2+) concentration in turn triggers plasma membrane blebbing, lysosomal exocytosis, and membrane repair response. Our results indicate that CPPs split into two major classes: (i) amphipathic CPPs that modulate the plasma membrane integrity inducing influx of Ca(2+) and activating downstream responses starting from low concentrations; (ii) non-amphipathic CPPs that do not evoke changes at relevant concentrations. Triggering of the membrane repair response may help cells to replace distorted plasma membrane regions and cells can recover from the influx of Ca(2+) if its level is not drastically elevated.     

Differential responses of soil bacteria,fungi, archaea and protists to plant species richness and plant functional group identity

Plants are known to influence belowground microbial community structure along their roots, but the impacts of plant species richness and plant functional group (FG) identity on microbial communities in the bulk soil are still not well understood. Here, we used 454‐pyrosequencing to analyse the soil microbial community composition in a long‐term biodiversity experiment at Jena, Germany. We examined responses of bacteria, fungi, archaea, and protists to plant species richness (communities varying from 1 to 60 sown species) and plant FG identity (grasses, legumes, small herbs, tall herbs) in bulk soil. We hypothesized that plant species richness and FG identity would alter microbial community composition and have a positive impact on microbial species richness. Plant species richness had a marginal positive effect on the richness of fungi, but we observed no such effect on bacteria, archaea and protists. Plant species richness also did not have a large impact on microbial community composition. Rather, abiotic soil properties partially explained the community composition of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), archaea and protists. Plant FG richness did not impact microbial community composition; however, plant FG identity was more effective. Bacterial richness was highest in legume plots and lowest in small herb plots, and AMF and archaeal community composition in legume plant communities was distinct from that in communities composed of other plant FGs. We conclude that soil microbial community composition in bulk soil is influenced more by changes in plant FG composition and abiotic soil properties, than by changes in plant species richness per se.     

Cocoa extract protects against early alcohol-induced liver injury in the rat

Oxidants have been shown to be involved in alcohol-induced liver injury. This study was designed to determine whether cocoa flavonoid extract, composed mostly of epicatechin and epicatechin oligomers, protects against early alcohol-induced liver injury in rats. Male Wistar rats were fed high-fat liquid diets with or without ethanol (10-14 g/kg per day) and cocoa extract (400 mg/kg per day) continuously for 4 weeks using an enteral feeding protocol. Mean body weight gains ( approximately 4 g/day) were not significantly different between treatment groups. Cocoa extract did not affect average daily urine ethanol concentrations ( approximately 200mg/dL). After 4 weeks, serum alanine amino transferase levels of the ethanol group were increased nearly fourfold (110+/-16 IU/L) compared to control values (35+/-3 IU/L); this effect of ethanol was blocked by cocoa extract (60+/-6 IU/L). Additionally, enteral ethanol caused severe fat accumulation, mild inflammation, and necrosis in the liver; cocoa extract significantly blunted these changes. Increases in liver TNFalpha protein levels caused by ethanol were completely blocked by cocoa extract. Further, ethanol significantly increased the accumulation of protein adducts of 4-hydroxynonenal, a product of lipid peroxidation serving as an index of oxidative stress; again this was counteracted by the addition of cocoa extract. These results indicate that dietary flavanols such as those found in cocoa can prevent early alcohol-induced liver injury.     

PRO-C3-Levels in Patients with HIV/HCV-Co-Infection Reflect Fibrosis Stage and Degree of Portal Hypertension

Background

Liver-related deaths represent the leading cause of mortality among patients with HIV/HCV-co-infection, and are mainly related to complications of fibrosis and portal hypertension. In this study, we aimed to evaluate the structural changes by the assessment of extracellular matrix (ECM) derived degradation fragments in peripheral blood as biomarkers for fibrosis and portal hypertension in patients with HIV/HCV co-infection.

Methods

Fifty-eight patients (67% male, mean age: 36.5 years) with HIV/HCV-co-infection were included in the study. Hepatic venous pressure gradient (HVPG) was measured in forty-three patients. The fibrosis stage was determined using FIB4 -Score. ECM degraded products in peripheral blood were measured using specific ELISAs (C4M, MMP-2/9 degraded type IV collagen; C5M, MMP-2/9 degraded type V collagen; PRO-C3, MMP degraded n-terminal propeptide of type III collagen).

Results

As expected, HVPG showed strong and significant correlations with FIB4-index (r_s = 0.628; p = 7*10⁻⁷). Interestingly, PRO-C3 significantly correlated with HVPG (r_s = 0.354; p = 0.02), alanine aminotransferase (r_s = 0.30; p = 0.038), as well as with FIB4-index (r_s = 0.3230; p = 0.035). C4M and C5M levels were higher in patients with portal hypertension (HVPG>5 mmHg).

Conclusion

PRO-C3 levels reflect liver injury, stage of liver fibrosis and degree of portal hypertension in HIV/HCV-co-infected patients. Furthermore, C4M and C5M were associated with increased portal pressure. Circulating markers of hepatic ECM remodeling might be helpful in the diagnosis and management of liver disease and portal hypertension in patients with HIV/HCV coinfection.     

Evaluation of microarray data normalization procedures using spike-in experiments

Background  

Recently, a large number of methods for the analysis of microarray data have been proposed but there are few comparisons of their relative performances. By using so-called spike-in experiments, it is possible to characterize the analyzed data and thereby enable comparisons of different analysis methods.