Insulin resistance and arterial stiffness in healthy adolescents and young adults

AIMS/HYPOTHESIS

Increased arterial stiffness is a risk factor for adverse cardiovascular events in adults with obesity-related insulin resistance (IR) or type 2 diabetes mellitus. Adolescents with type 2 diabetes have stiffer vessels. Whether stiffness is increased in obesity/IR in youth is not known. We sought to determine if IR was a determinant of arterial stiffness in youth, independent of obesity and cardiovascular risk factors.

METHODS

We measured cardiovascular risk factors, IR, adipocytokines and arterial stiffness (brachial artery distensibility [BrachD], pulse wave velocity [PWV]) and wave reflection (augmentation index [AIx]) in 343 adolescents and young adults without type 2 diabetes (15-28 years old, 47% male, 48% non-white). Individuals <85th percentile of BMI were classified as lean (n = 232). Obese individuals were grouped by HOMA index as not insulin resistant (n = 46) or insulin resistant (n = 65) by the 90th percentile for HOMA for lean. Mean differences were evaluated by ANOVA. Multivariate models evaluated whether HOMA was an independent determinant of arterial stiffness.

RESULTS

Risk factors deteriorated from lean to obese to obese/insulin resistant (all p ≤ 0.017). Higher AIx, lower BrachD and higher PWV indicated increased arterial stiffness in obese and obese/insulin-resistant participants. HOMA was not an independent determinant. Age, sex, BMI and BP were the most consistent determinants, with HDL-cholesterol playing a role for BrachD and leptin for PWV (AIx R²= 0.34; BrachD R² = 0.37; PWV R² = 0.40; all p ≤ 0.02).

CONCLUSIONS/INTERPRETATION

Although IR is associated with increased arterial stiffness, traditional cardiovascular risk factors, especially obesity and BP, are the major determinants of arterial stiffness in healthy young people.

Highly efficient virus resistance mediated by artificial microRNAs that target the suppressor of PVX and PVY in plants

MicroRNAs (miRNAs) processed from nuclear-encoded transcripts control expression of target transcripts by directing cleavage or translational inhibition. Artificial miRNAs (amiRNAs) that exploit this endogenous gene silencing mechanism can be designed to target any gene of interest and provide a highly specific approach for effective post-transcriptional gene silencing (PTGS) in plants. Here, using Arabidopsis thaliana miR159a, miR167b and miR171a precursors as backbones, we designed two types of amiRNA targeting sequence that encode the silencing suppressor HC-Pro of Potato virus Y (PVY) and the TGBp1/p25 (p25) of Potato virus X (PVX). The detected amiRNAs efficiently inhibited HC-Pro and p25 gene expression and conferred highly specific resistance against PVY or PVX infection in transgenic Nicotiana tabacum; this resistance was also maintained under conditions of increased viral pressure. Moreover, resistance was strongly influenced by the complementarity between the target sequence and amiRNA, and was well correlated to amiRNA expression level; the expression level of amiRNAs was also well related to the precursor backbones. We further showed that transgenic N. tabacum developed highly effective resistance to both PVY and PVX through expression of a dimeric amiRNA precursor. Together, our findings indicate that transgenic plants with multiple virus-specific resistance can be obtained through co-expression of several amiRNAs targeting multiple viruses.

Combination of hsa-miR-375 and hsa-miR-142-5p as a predictor for recurrence risk in gastric cancer patients following surgical resection

BACKGROUND

Recurrence is a major factor leading to treatment failure and death in gastric cancer (GC) patients following surgical resection. Importantly, the prediction of recurrence is critical in improving clinical outcomes. We isolated a group of microRNAs (miRNAs) and evaluated their usefulness as prognostic markers for the recurrence of GC.

PATIENTS AND METHODS

A total of 65 GC patients were selected for systematic analysis, 29 patients with recurrence and 36 patients without recurrence. Firstly, miRNAs microarray and bioinformatics methods were used to characterize classifiers from primary tumor samples (n = 8). Following, we validated these predictors both in frozen fresh and paraffin-embedded tissue samples (n = 57) using quantitative PCR.

RESULTS

We have identified 17 differential miRNAs including 10 up-regulated and 7 down-regulated miRNAs in recurrence group. Using k-top scoring pairs (k-TSP) method, we further ascertained hsa-miR-375 and hsa-miR-142-5p as a classifier to recognize recurrence and nonrecurrence cases both in the training and test samples. Moreover, we validated this classifier in 34 frozen fresh tissues and 38 paraffin-embedded tissues with consistent sensitivity and specificity with training set; among them, 15 cases were matched. A high frequency recurrence and poor survival were observed in GC cases with high level of hsa-miR-375 and low level of hsa-miR-142-5p (P < 0.001). In addition, we evaluated that hsa-miR-375 and hsa-miR-142-5p were involved in regulating target genes in several oncogenic signal pathways, such as TP53, MAPK, Wnt and vascular endothelial growth factor.

CONCLUSION

Our results indicate that the combination of hsa-miR-375 and hsa-miR-142-5p as a predictor of disease progression has the potential to predict recurrence risk for GC patients.

Characterization of immortalized mesenchymal stem cells derived from foetal porcine pancreas

Islet replacement therapy is limited by shortage of donor islet cells. Usage of islet cells derived from porcine pancreatic stem cells (PSCs) is currently viewed as the most promising alternative for human islet transplantation. However, PSCs are rare and have a finite proliferative lifespan. In this study, we isolated and established an immortalized mesenchymal stem cell (MSC) line derived from foetal porcine pancreas, by transfecting human telomerase reverse transcriptase (hTERT) and called these immortalized pancreatic mesenchymal stem cells (iPMSCs). The iPMSCs have been cultured for more than 80 passages and have capacity to differentiate into neurons, cardiomyocytes, germ cells and islet-like cells, analysed by morphology, RT-PCR, western blotting, immunofluorescence, immunocytochemistry and transplantation assay. Islets derived from iPMSCs reversed hyperglycaemia in streptozotocin-induced diabetic mice and secreted insulin and C-peptide in vitro. These results demonstrated that iPMSCs might provide unlimited resources for islet replacement therapy and models for functional cell differentiation.

Purkinje cell-specific knockout of the protein phosphatase PP2B impairs potentiation and cerebellar motor learning

Cerebellar motor learning is required to obtain procedural skills. Studies have provided supportive evidence for a potential role of kinase-mediated long-term depression (LTD) at the parallel fiber to Purkinje cell synapse in cerebellar learning. Recently, phosphatases have been implicated in the induction of potentiation of Purkinje cell activities in vitro, but it remains to be shown whether and how phosphatase-mediated potentiation contributes to motor learning. Here, we investigated its possible role by creating and testing a Purkinje cell-specific knockout of calcium/calmodulin-activated protein-phosphatase-2B (L7-PP2B). The selective deletion of PP2B indeed abolished postsynaptic long-term potentiation in Purkinje cells and their ability to increase their excitability, whereas LTD was unaffected. The mutants showed impaired "gain-decrease" and "gain-increase" adaptation of their vestibulo-ocular reflex (VOR) as well as impaired acquisition of classical delay conditioning of their eyeblink response. Thus, our data indicate that PP2B may indeed mediate potentiation in Purkinje cells and contribute prominently to cerebellar motor learning.

Diphenhydramine modulates cytokines and induces apoptosis in experimental acute pancreatitis

In this study, we investigated the therapeutic potential of diphenhydramine (DPH), a H(1) receptor antagonist, on taurocholate-induced acute pancreatitis and the underlying mechanisms involved. Rats were randomly divided into sham-operated, model, DPH-treated, octreotide-treated and the DPH plus octreotide combination therapy groups (n = 30 per group). Animals were sacrificed 3, 6 and 24 h after modeling and drug administration (n = 10 per time point) and sera, pancreas and lungs were harvested for further studies. DPH and octreotide monotherapy relieved histopathological injuries in multiple organs when compared to the model group. Combination therapy (DPH + octreotide) demonstrated better therapeutic potential than monotherapy. Data indicated that combination therapy had a better ability to reduce average mortality rates in rats, decrease the number of inflammatory cells, attenuate necrosis, upregulate the levels of amylase, TNF-alpha and IL-8 and downregulate the levels of IL-10 in the serum. Moreover, enhanced expression of Bax in the pancreas and lung were recorded suggesting a pro-apoptotic mechanism involved in the therapeutic potential of DPH. Our study demonstrated the therapeutic potential of DPH in acute pancreatitis and suggested a novel strategy for clinical management of this disease.

Diversity of chromosomal karyotypes in maize and its relatives

Maize is a highly diverse species on the gene sequence level. With the recent development of methods to distinguish each of the 10 pairs of homologues in somatic root tip spreads, a wide collection of maize lines was subjected to karyotype analysis to serve as a reference for the community and to examine the spectrum of chromosomal features in the species. The core nested association mapping progenitor collection and additional selections of diversity lines were examined. Commonly used inbred lines were included in the analysis. The centromere 4 specific repeat and ribosomal RNA loci were invariant. The CentC centromere repeat exhibited extensive differences in quantity on any particular chromosome across lines. Knob heterochromatin was highly variable with locations at many sites in the genome. Lastly, representative examples from other species in the genus Zea (teosintes) were examined, which provide information on the evolution of chromosomal features.

A systems engineering approach to validation of a pulmonary physiology simulator for clinical applications

Physiological simulators which are intended for use in clinical environments face harsh expectations from medical practitioners; they must cope with significant levels of uncertainty arising from non-measurable parameters, population heterogeneity and disease heterogeneity, and their validation must provide watertight proof of their applicability and reliability in the clinical arena. This paper describes a systems engineering framework for the validation of an in silico simulation model of pulmonary physiology. We combine explicit modelling of uncertainty/variability with advanced global optimization methods to demonstrate that the model predictions never deviate from physiologically plausible values for realistic levels of parametric uncertainty. The simulation model considered here has been designed to represent a dynamic in vivo cardiopulmonary state iterating through a mass-conserving set of equations based on established physiological principles and has been developed for a direct clinical application in an intensive-care environment. The approach to uncertainty modelling is adapted from the current best practice in the field of systems and control engineering, and a range of advanced optimization methods are employed to check the robustness of the model, including sequential quadratic programming, mesh-adaptive direct search and genetic algorithms. An overview of these methods and a comparison of their reliability and computational efficiency in comparison to statistical approaches such as Monte Carlo simulation are provided. The results of our study indicate that the simulator provides robust predictions of arterial gas pressures for all realistic ranges of model parameters, and also demonstrate the general applicability of the proposed approach to model validation for physiological simulation.

Nanocrystalline diamond microelectrode arrays fabricated on sapphire technology for high-time resolution of quantal catecholamine secretion from chromaffin cells

The quantal release of oxidizable molecules can be successfully monitored by means of polarized carbon fiber microelectrodes (CFEs) positioned in close proximity to the cell membrane. To partially overcome certain CFE limitations, mainly related to their low spatial resolution and lack of optical transparency, we developed a planar boron-doped nanocrystalline diamond (NCD) prototype, grown on a transparent sapphire wafer. Responsiveness to applied catecholamines as well as the electrochemical and optical properties of the NCD-based device were first characterized by cyclic voltammetry and optical transmittance measurements. By stimulating chromaffin cells positioned on the device with external KCl, well-resolved quantal exocytotic events could be detected either from one NCD microelectrode, or simultaneously from an array of four microelectrodes, indicating that the chip is able to monitor secretory events (amperometric spikes) from a number of isolated chromaffin cells. Spikes detected by the planar NCD device had comparable amplitudes, kinetics and vesicle diameter distributions as those measured by conventional CFEs from the same chromaffin cell.