Noninvasive Assessment of Pulse-Wave Velocity and Flow-Mediated Vasodilation in Anesthetized G?ttingen Minipigs

Few methods for noninvasive assessment of arterial stiffness and endothelial dysfunction in porcine models are available. The aim of this study was to evaluate methods for assessment of arterial stiffness and endothelial dysfunction in anesthetized Göttingen minipigs. Pulse-wave velocity (PWV) was assessed in male Göttingen minipigs (n = 8; age approximately 60 wk) by using applanation tonometry of the carotid and femoral arteries. In addition, flow-mediated vasodilation (FMD) was assessed by using vascular ultrasonography of the brachial artery to evaluate endothelial dysfunction. To evaluate the reproducibility of the methods, minipigs were anesthetized by intravenous infusion of ketamine and midazolam and examined every other day for a total of 3 trials. Neither examination day nor systolic, diastolic, or mean arterial blood pressure statistically influenced PWV or FMD. The median interexamination coefficient of variation was 17% for PWV and 59% for FMD. Measured values of PWV corresponded largely to those in clinically healthy humans, but FMD values were lower than expected for lean, young animals. Although the ketamine–midazolam anesthesia we used has been associated with minor hemodynamic effects in vivo, in vitro studies suggest that both drugs are vasodilatory. Therefore anesthesia might have influenced the endothelial response, contributing to the modest FMD response and the concurrent high coefficients of variation that we noted. We conclude that PWV—but not FMD—showed acceptable interexamination variation for its potential application in porcine models.Abbreviations: FMD, flow-mediated vasodilation; FVI, integrated flow velocity; GTN, glyceryl trinitrate; PWV, pulse-wave velocity; T, transit timeCardiovascular disease has become a global challenge in public health,⁴² and the development and characterization of comparative animal models are of increasing importance. Several animal models of atherosclerosis, including porcine, have been described.^11,12,34 Due to similarities to humans in the anatomy of the cardiovascular system and metabolic physiology, pigs represent a generally useful model in regard to preclinical evaluation and pharmacology.³⁶ Assessment of changes related to atherosclerosis in vivo would be valuable in for example longitudinal assessment of drug effect, but few noninvasive methods for evaluating structural and functional changes in the arteries of pigs are available. In humans, increased arterial stiffness, which occurs with advanced age, also is caused by the pathophysiologic changes associated with atherosclerosis,²⁶ and noninvasive methods for assessing arterial stiffness have been established. The evaluation of pulse-wave velocity (PWV) by using pressure transducers, such as applanation tonometry, is a method recognized as an independent predictor for cardiovascular events in epidemiologic studies.²¹ The method evaluates the velocity with which the pulse wave is propagated through the arterial tree, with arterial stiffness causing increased velocity.^{1,22,29,37,39} Flow-mediated vasodilation (FMD), assessed by vascular ultrasonography, represents a noninvasive evaluation of endothelial-dependent vasodilation. A decrease in vasodilation as a response to increased shear stress has been recognized as a marker of endothelial dysfunction, which precedes the development of atherosclerosis.^5,7 Recent studies have shown that the FMD method is applicable in large animals (that is, dogs and horses) and that a decreased FMD response occurs in dogs with valvular heart disease.^10,15,23,28The aim of this study was to evaluate the reproducibility of methods for assessing arterial stiffness (PWV) and endothelial function (FMD response) in anesthetized Göttingen minipigs, including the influences of arterial blood pressure, heart rate, and room and body temperatures on these methods.     

Analytical Utility of Mass Spectral Binning in Proteomic Experiments by SPectral Immonium Ion Detection (SPIID)

Unambiguous identification of tandem mass spectra is a cornerstone in mass-spectrometry-based proteomics. As the study of post-translational modifications (PTMs) by means of shotgun proteomics progresses in depth and coverage, the ability to correctly identify PTM-bearing peptides is essential, increasing the demand for advanced data interpretation. Several PTMs are known to generate unique fragment ions during tandem mass spectrometry, the so-called diagnostic ions, which unequivocally identify a given mass spectrum as related to a specific PTM. Although such ions offer tremendous analytical advantages, algorithms to decipher MS/MS spectra for the presence of diagnostic ions in an unbiased manner are currently lacking. Here, we present a systematic spectral-pattern-based approach for the discovery of diagnostic ions and new fragmentation mechanisms in shotgun proteomics datasets. The developed software tool is designed to analyze large sets of high-resolution peptide fragmentation spectra independent of the fragmentation method, instrument type, or protease employed. To benchmark the software tool, we analyzed large higher-energy collisional activation dissociation datasets of samples containing phosphorylation, ubiquitylation, SUMOylation, formylation, and lysine acetylation. Using the developed software tool, we were able to identify known diagnostic ions by comparing histograms of modified and unmodified peptide spectra. Because the investigated tandem mass spectra data were acquired with high mass accuracy, unambiguous interpretation and determination of the chemical composition for the majority of detected fragment ions was feasible. Collectively we present a freely available software tool that allows for comprehensive and automatic analysis of analogous product ions in tandem mass spectra and systematic mapping of fragmentation mechanisms related to common amino acids.In mass spectrometry (MS)-based proteomics, protein mixtures are digested into peptides using standard proteases such as trypsin or Lys-C (1). The complex peptide mixture is separated via liquid chromatography (LC) directly coupled to MS, and the eluting peptide ions are electrosprayed into the vacuum of the mass spectrometer, where a peptide mass spectrum is recorded (2). In the mass spectrometer, selected peptide ions are fragmented, most commonly through the collision of peptide molecular ions with inert gas molecules in a technique referred to as either collision-induced dissociation (CID)¹ or collisionally activated dissociation (3, 4). During this energetic collision, some of the deposited kinetic energy is converted into internal energy, which results in peptide bond breakage and fragmentation of the molecular peptide ion into sequence-specific ions (5). Identification of the analyzed peptide is then performed by scanning the measured peptide mass and list of fragment masses against a protein sequence database (6). Overall this approach provides a rapid and sensitive means of determining the primary sequence of peptides.During the fragmentation step, various types of fragment ions can be observed in the MS/MS spectrum. Their occurrence depends on the primary sequence of the investigated peptide, the amount of internal energy deposited, how the energy was introduced, the charge state, and other factors (7). Low-energy dissociation conditions as observed in ion trap CID mainly generate fragment ions containing sequence-specific amino acid information about the investigated peptides (8). This occurs because the energy deposited during this fragmentation method primarily facilitates the fragmentation of precursor ions yielding single peptide bond fragmentation between individual amino acids (9).With faster activation methods, such as beam-type/quadrupole CID (10), generated fragments can undergo further collisions. Multiple bonds can thereby be fragmented, giving rise to internal sequence ions, which in combination with regular b- and y-type cleavage produce specific amino-immonium ions (11). These immonium ions appear in the very low m/z range of the MS/MS spectrum, and for the majority of naturally occurring amino acids such immonium ions are unique for that particular residue (12, 13). Exceptions for this are the leucine/isoleucine and lysine/glutamine pairs, which produce immonium ions with the same chemical mass. Overall, immonium ions can confirm the presence of certain amino acid residues in a peptide, whereas information regarding the position or the stoichiometry of these amino acid residues cannot be ascertained. Because tryptic peptides on average contain 9 to 12 amino acids, they frequently contain many different residues; as a result, the analytical information hidden in the regular amino acid immonium ions might be limited. However, immonium ions can be used to support peptide sequence assignment during proteomic database searching (14).Contrary to the 20 naturally occurring residues, many amino acids can be modified by various post-translational modifications (PTMs), and these PTM-bearing residues can themselves generate unique immonium ions—the so-called diagnostic ions. The two most prominent examples are phosphorylation of tyrosine and acetylation of lysine residues (15), which generate diagnostic ions at m/z = 216.0424 and m/z = 126.0917, respectively. Thus, the presence of these unique ions in a MS/MS spectrum can unequivocally identify the sequenced peptide as harboring a given PTM. Evidently, knowledge regarding modification-specific diagnostic ions is of great importance for the identification and validation of modified peptides in MS-based proteomics (16, 17). Additionally, such PTM-specific information can be informative in targeted proteomics approaches facilitating MS/MS precursor ion scanning (18) and become valuable in post-acquisition analysis involving extracted ion chromatograms for specific m/z values. Moreover, information regarding diagnostic ions can be a powerful addition to analytical approaches such as selected reaction monitoring, a targeted technique that relies on ion-filtering capabilities to comprehensively study peptides and PTMs (19).Currently only a minor subset of modified amino acids has been investigated for diagnostic ions, primarily because of the lack of unbiased methods for mapping such ions in large-scale proteomics experiments. The identification of diagnostic ions is a labor-intensive endeavor, requiring manual interpretation of large numbers of MS/MS spectra for proper validation of low-mass fragmentation ions. As a result, most studies on diagnostic ions have been performed on a few selected synthetic peptides, as the interrogation of larger biological datasets has not been feasible (15, 20).Here we describe a proteomic approach utilizing a novel algorithm based upon binning of tandem mass spectra for fast and automated mapping of analogously occurring product ions. The developed algorithm is completely independent of instrument type and fragmentation technique employed, but it performs more favorably under experimental conditions that augment the generation of immonium ions. As a result, the performance of the algorithm is benchmarked on data derived from LTQ Orbitrap Velos and Q Exactive mass spectrometers, which exhibit improved HCD performance (21–23). HCD has proven to be a powerful fragmentation technique, particularly for PTM analysis (24, 25), as no low mass detection cutoff is observed as compared with fragmentation experiments on ion trap mass spectrometers (26). Moreover, the beam-type energy deposited during HCD fragmentation allows for improved generation of both immonium and other sequence-related ions relative to CID (27, 28). Additionally, HCD experiments are performed at very high resolution, yielding high mass accuracy (<10 ppm) on all detected fragment ions, which allows the algorithm to utilize very narrow mass binning and hence easily determine the exact chemical composition of any novel detected ions.Briefly, the algorithm takes all significantly identified MS/MS spectra and bins them together in discrete mass bins. As commonly occurring ions, such as immonium and diagnostic ions, will have same chemical composition and consequently the same m/z, they will cluster in the same mass bins, whereas sequence-specific fragment ions will scatter across the binned mass range. For validation of the presented approach, we mapped known and novel diagnostic ions from a variety of PTM-bearing amino acids, demonstrating the sensitivity and specificity of the method. Moreover, we demonstrate that mass spectral binning additionally can be employed for automated mapping of composition-specific neutral losses from large-scale proteomic experiments.     

Integrating genetic data and population viability analyses for the identification of harbour seal (Phoca vitulina) populations and management units

Identification of populations and management units is an essential step in the study of natural systems. Still, there is limited consensus regarding how to define populations and management units, and whether genetic methods allow for inference at the relevant spatial and temporal scale. Here, we present a novel approach, integrating genetic, life history and demographic data to identify populations and management units in southern Scandinavian harbour seals. First, 15 microsatellite markers and model‐ and distance‐based genetic clustering methods were used to determine the population genetic structure in harbour seals. Second, we used harbour seal demographic and life history data to conduct population viability analyses (PVAs) in the vortex simulation model in order to determine whether the inferred genetic units could be classified as management units according to Lowe and Allendorf's (Molecular Ecology, 19, 2010, 3038) ‘population viability criterion’ for demographic independence. The genetic analyses revealed fine‐scale population structuring in southern Scandinavian harbour seals and pointed to the existence of several genetic units. The PVAs indicated that the census population size of each of these genetic units was sufficiently large for long‐term population viability, and hence that the units could be classified as demographically independent management units. Our study suggests that population genetic inference can offer the same degree of temporal and spatial resolution as ‘nongenetic’ methods and that the combined use of genetic data and PVAs constitutes a promising approach for delineating populations and management units.     

Risk of Melanoma in People with HIV/AIDS in the Pre- and Post-HAART Eras: A Systematic Review and Meta-Analysis of Cohort Studies

Objective

Following the introduction of highly active antiretroviral therapy (HAART) the risk of AIDS-defining cancers decreased but incidence of many non-AIDS-defining cancers has reportedly increased in those with HIV/AIDS. Whether melanoma risk has also changed in HIV/AIDS patients post-HAART is unknown and therefore we evaluated this in comparison with the risk before HAART.

Design

Systematic review and meta-analysis.

Methods

We searched Medline, Embase and ISI science citation index databases to April 2013. All cohort studies of patients diagnosed with HIV/AIDS that permitted quantitative assessment of the association with melanoma were eligible. Detailed quality assessment of eligible studies was conducted, focussing particularly on adjustment for ethnicity, a priori considered essential for an unbiased assessment of melanoma risk. Data were pooled using a random effects model.

Results

From 288 articles, we identified 21 that met the inclusion criteria, 13 presenting data for the post-HAART era and 8 for the pre-HAART era. Post-HAART the pooled relative risk (pRR) for the association between HIV/AIDS and melanoma was 1.26 (95% CI, 0.97–1.64) and 1.50 (95% CI 1.12–2.01) among studies that accounted for ethnicity, with evidence of significant heterogeneity (P = 0.004, I² = 55.5). Pre-HAART pRRs were 1.26 (95% CI 1.11–1.43; P_het = 0.82) and 1.28 (95% CI 1.10–1.49) among studies adjusted for ethnicity.

Conclusions

People with HIV/AIDS remain at a significantly increased risk of developing melanoma in the post-HAART era. White skinned people with HIV/AIDS should be screened regularly and counselled against excessive sun exposure.     

Statins Do Not Alter the Incidence of Mesothelioma in Asbestos Exposed Mice or Humans

Mesothelioma is principally caused by asbestos and may be preventable because there is a long latent period between exposure and disease development. The most at-risk are a relatively well-defined population who were exposed as a consequence of their occupations. Although preventative agents investigated so far have not been promising, discovery of such an agent would have a significant benefit world-wide on healthcare costs and personal suffering. Statins are widely used for management of hypercholesterolemia and cardiovascular risk; they can induce apoptosis in mesothelioma cells and epidemiological data has linked their use to a lower incidence of cancer. We hypothesised that statins would inhibit the development of asbestos-induced mesothelioma in mice and humans. An autochthonous murine model of asbestos-induced mesothelioma was used to test this by providing atorvastatin daily in the feed at 100 mg/kg, 200 mg/kg and 400 mg/kg. Continuous administration of atorvastatin did not alter the rate of disease development nor increase the length of time that mice survived. Latency to first symptoms of disease and disease progression were also unaffected. In a parallel study, the relationship between the use of statins and development of mesothelioma was investigated in asbestos-exposed humans. In a cohort of 1,738 asbestos exposed people living or working at a crocidolite mine site in Wittenoom, Western Australia, individuals who reported use of statins did not have a lower incidence of mesothelioma (HR = 1.01; 95% CI = 0.44–2.29, p = 0.99). Some individuals reported use of both statins and non-steroidal anti-inflammatory drugs or COX-2 inhibitors, and these people also did not have an altered risk of mesothelioma development (HR = 1.01; 95% CI = 0.61–1.67, p = 0.97). We conclude that statins do not moderate the rate of development of mesothelioma in either a mouse model or a human cohort exposed to asbestos.     

Learning to Eat Vegetables in Early Life: The Role of Timing,Age and Individual Eating Traits

Vegetable intake is generally low among children, who appear to be especially fussy during the pre-school years. Repeated exposure is known to enhance intake of a novel vegetable in early life but individual differences in response to familiarisation have emerged from recent studies. In order to understand the factors which predict different responses to repeated exposure, data from the same experiment conducted in three groups of children from three countries (n = 332) aged 4–38 m (18.9±9.9 m) were combined and modelled. During the intervention period each child was given between 5 and 10 exposures to a novel vegetable (artichoke puree) in one of three versions (basic, sweet or added energy). Intake of basic artichoke puree was measured both before and after the exposure period. Overall, younger children consumed more artichoke than older children. Four distinct patterns of eating behaviour during the exposure period were defined. Most children were “learners” (40%) who increased intake over time. 21% consumed more than 75% of what was offered each time and were labelled “plate-clearers”. 16% were considered “non-eaters” eating less than 10 g by the 5^th exposure and the remainder were classified as “others” (23%) since their pattern was highly variable. Age was a significant predictor of eating pattern, with older pre-school children more likely to be non-eaters. Plate-clearers had higher enjoyment of food and lower satiety responsiveness than non-eaters who scored highest on food fussiness. Children in the added energy condition showed the smallest change in intake over time, compared to those in the basic or sweetened artichoke condition. Clearly whilst repeated exposure familiarises children with a novel food, alternative strategies that focus on encouraging initial tastes of the target food might be needed for the fussier and older pre-school children.     

Efficacy of High Intensity Exercise on Disease Activity and Cardiovascular Risk in Active Axial Spondyloarthritis: A Randomized Controlled Pilot Study

Background

Physical therapy is recommended for the management of axial spondyloarthritis (axSpA) and flexibility exercises have traditionally been the main focus. Cardiovascular (CV) diseases are considered as a major health concern in axSpA and there is strong evidence that endurance and strength exercise protects against CV diseases. Therefore, the aim of this study was to investigate the efficacy of high intensity endurance and strength exercise on disease activity and CV health in patients with active axSpA.

Methods

In a single blinded randomized controlled pilot study the exercise group (EG) performed 12 weeks of endurance and strength exercise while the control group (CG) received treatment as usual. The primary outcome was the Ankylosing Spondylitis (AS) Disease Activity Score (ASDAS). Secondary outcomes included patient reported disease activity (Bath AS Disease Activity Index [BASDAI]), physical function (Bath AS Functional Index [BASFI]), and CV risk factors measured by arterial stiffness (Augmentation Index [Alx]) and Pulse Wave Velocity [PWV]), cardiorespiratory fitness (VO₂ peak) and body composition. ANCOVA on the post intervention values with baseline values as covariates was used to assess group differences, and Mann Whitney U-test was used for outcomes with skewed residuals.

Results

Twenty-eight patients were included and 24 (EG, n = 10, CG, n = 14) completed the study. A mean treatment effect of −0.7 (95%CI: −1.4, 0.1) was seen in ASDAS score. Treatment effects were also observed in secondary outcomes (mean group difference [95%CI]): BASDAI: −2.0 (−3.6, −0.4), BASFI: −1.4 (−2.6, −0.3), arterial stiffness (estimated median group differences [95% CI]): AIx (%): −5.3 (−11.0, −0.5), and for PVW (m/s): −0.3 (−0.7, 0.0), VO₂ peak (ml/kg/min) (mean group difference [95%CI]: 3.7 (2.1, 5.2) and trunk fat (%): −1.8 (−3.0, −0.6). No adverse events occurred.

Conclusion

High intensity exercise improved disease activity and reduced CV risk factors in patients with active axSpA. These effects will be further explored in a larger trial.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01436942","term_id":"NCT01436942"}}NCT01436942