Pathophysiological role of Amadori-glycated proteins in diabetic microangiopathy

Early and advanced nonenzymatic glycation of proteins are increased in diabetes. Although Amadori-glycated proteins are the major glycated modifications, most studies so far have focused on the role of advanced glycation end-products (AGEs) in diabetes-related vascular complications. It was only recently that the role of Amadori-glycated proteins has come under consideration. Here we review data that point to an important role of Amadori-modified glycated serum proteins in diabetic microangiopathy. Amadori-glycated albumin induces the activation of glomerular mesangial and endothelial cells to a phenotype that may be linked to the pathogenesis of diabetic microangiopathy, that is, by the stimulation of protein kinase C, activation of transforming growth factor beta, and the expression of extracellular matrix proteins. In type 1 diabetic patients, levels of Amadori-glycated proteins are independently associated with nephropathy and retinopathy. Reduction of Amadori-glycated albumin levels in diabetic animal models ameliorates the progression of nephropathy and retinopathy, indicating a causal role of Amadori-glycated proteins in the pathogenesis of diabetic nephropathy and retinopathy. Based on these data, inhibition of Amadori-glycated albumin may be a target for reduction of diabetic vascular complications.     

Chicken HS4 Insulators Have Minimal Barrier Function Among Progeny of Human Hematopoietic Cells Transduced With an HIV1-based Lentiviral Vector

Position effects limit the curative potential of gene transfer strategies for the hemoglobinopathies by inducing clonal variability of transgene expression. We evaluated the mitigating effects of the chicken hypersensitivity site 4 (HS4) insulator among lentiviral vector-transduced human hematopoietic cells. We constructed various lentiviral vectors using a green fluorescent protein (GFP) reporter under the control of a reverse-oriented murine stem cell virus (MSCV)-long-term repeat (LTR) promoter or a reverse-oriented β-globin expression cassette. A full-length HS4, a tandem HS4 core, and a single core insulator were inserted into the 3′ LTR in both forward and reverse orientation. All but the reverse single core insulator significantly decreased titers. All reduced %GFP without increasing mean fluorescence intensity (MFI) among erythroid progeny of transduced human CD34⁺ cells. A lower coefficient of variation (CV) was observed only among progeny of the full-length vector-transduced cells, yet a fivefold reduction in transduction efficiency was observed. In xenografted mice, the single core insulator decreased both the %GFP and the MFI at 4 and 8 weeks after transplantation with no difference in CVs. These data demonstrate that the inclusion of HS4 insulator elements lowers viral titers, reduces efficiency of transduction, and produces minimal effects on transgene expression among human hematopoietic cells in vitro and in vivo.     

Human plasma complement C3 is independently associated with coronary heart disease, but only in heavy smokers (the CODAM study)

Background

Complement C3 is an emerging risk factor for coronary heart disease (CHD) and is particularly increased in the metabolic syndrome. A direct effect of smoking on structure and function of complement C3 has been suggested.

Hypothesis

Smoking behavior may affect the cardiovascular risk that is associated with plasma complement C3.

Methods

The association between plasma C3 and CHD was studied in the CODAM (Cohort on Diabetes and Atherosclerosis Maastricht) study population (n = 562, 61% male) with examination of effect modification by smoking.

Results

The overall prevalence of CHD was 23.3%. Higher plasma C3 levels were associated with a higher CHD prevalence, and there was a significant interaction with heavy smoking (p = 0.01). In never & light smokers, the univariate OR for CHD per 1 s.d. (0.33 g/L) increase in C3 was 1.09 [95% confidence interval (CI) 0.85-1.41] (p = 0.505) whereas in heavy smokers it was 2.05 [1.43-2.93] (p < 0.001). The association in the group of heavy smokers remained significant (OR 2.38 [1.54-3.68], p < 0.001) after adjustment for traditional risk factors for cardiovascular disease and also after further adjustment for other cardiometabolic risk factors, i.e. the metabolic syndrome, CRP and insulin resistance (HOMA2IR) (OR C3 between 2.16 and 2.29, all p ≤ 0.001).

Conclusion

Human plasma complement C3 is associated with prevalent CHD, but only in heavy smokers, and this association is independent of important metabolic cardiovascular risk factors.     

Conformational changes induced in herpes simplex virus DNA polymerase upon DNA binding.

Herpesvirus DNA polymerases are prototypes for alpha-like DNA polymerases and important targets for antiherpesvirus drugs. We have investigated changes in the catalytic subunit of herpes simplex virus DNA polymerase following DNA binding by using the techniques of endogeneous fluorescence quenching and limited proteolysis. The fluorescence studies revealed a reduction in the rate of quenching by acrylamide in the presence of DNA without changes in the wavelength of the emission peak or in the lifetime of the fluorophore, consistent with the possibility of conformational changes. Strikingly, the proteolysis studies revealed that binding to a variety of natural and synthetic DNA and RNA molecules induced the appearance of a new cleavage site for trypsin near residue 1060 of the protein and increased cleavage by trypsin near the center of the protein. The extent of these cleavages correlated with the affinity of the polymerase for these ligands. These data provide strong evidence that binding to nucleic acid polymers induces substantial localized conformational changes in the polymerase. The locations of enhanced tryptic cleavage near sites implicated in substrate recognition and interaction with a processivity factor suggest that the conformational changes are important for catalysis and processivity of this prototype alpha-like DNA polymerase. Inhibition of these changes may provide a mechanism for antiherpesvirus drugs.     

Maternal Obesity Induced by Diet in Rats Permanently Influences Central Processes Regulating Food Intake in Offspring

Hypothalamic systems which regulate appetite may be permanently modified during early development. We have previously reported hyperphagia and increased adiposity in the adult offspring of rodents fed an obesogenic diet prior to and throughout pregnancy and lactation. We now report that offspring of obese (OffOb) rats display an amplified and prolonged neonatal leptin surge, which is accompanied by elevated leptin mRNA expression in their abdominal white adipose tissue. At postnatal Day 30, before the onset of hyperphagia in these animals, serum leptin is normal, but leptin-induced appetite suppression and phosphorylation of STAT3 in the arcuate nucleus (ARC) are attenuated; the level of AgRP-immunoreactivity in the hypothalamic paraventricular nucleus (PVH), which derives from neurones in the ARC and is developmentally dependent on leptin, is also diminished. We hypothesise that prolonged release of abnormally high levels of leptin by neonatal OffOb rats leads to leptin resistance and permanently affects hypothalamic functions involving the ARC and PVH. Such effects may underlie the developmental programming of hyperphagia and obesity in these rats.     

Clustering of metabolic syndrome risk factors and arterial stiffness in young adults: the Northern Ireland Young Hearts Project

OBJECTIVES: This study aimed to investigate whether the clustering of the risk factors of the metabolic syndrome (MetS) is associated with stiffness of central and peripheral arterial segments; whether these associations are similar in men and women; and whether insulin resistance and low-grade inflammation mediate any such associations. BACKGROUND: Increased arterial stiffness may explain, at least in part, the increased cardiovascular and diabetes risk associated with the MetS. However, the mechanisms linking the MetS to an increased arterial stiffness are incompletely understood, and gender differences may exist. METHODS: Cross-sectional analyses of data on 313 young men and women (mean age 23 years) from the Northern Ireland Young Hearts Project. Subjects were categorized according to the number of traits of the MetS; in addition a continuous MetS score was calculated. Arterial stiffness was assessed by measuring pulse wave velocity (PWV) in three arterial segments using a non-invasive optical method. RESULTS: The prevalence of the MetS was similar for men (10.6%) and women (10.5%). After adjustment for potential confounders and other cardiovascular risk factors, PWV of the three arterial segments investigated increased with increasing traits of the MetS in women only. Women with the MetS, as compared to those without risk factors of the syndrome, had greater PWV of the aorto-iliac (+14.0%, P = 0.016), the aorto-radial (+13.2%, P = 0.010) and aorto-dorsalis pedis (+11.8%, P = 0.011) segments. A great deal (up to 75%) of the association between the MetS and aortic-iliac PWV was mediated by heart rate, inflammation markers [C-reactive protein (CRP) and fibrinogen] and insulin resistance [homeostatic model assessment-insulin resistance (HOMA-IR)], whereas these variables did not explain much of the association between the MetS and PWV of the peripheral segments. CONCLUSIONS: Young women with the MetS show increased stiffness of peripheral and central arteries, a mechanism that may explain their increased cardiovascular risk. Low-grade inflammation, insulin resistance and sympathetic activation explain much of the adverse impact of the MetS on central, but not peripheral, arterial stiffness.     

Diagnosis and outcome of renal function in patients with renal artery stenosis: which role have color Doppler sonography and magnetic resonance angiography?

AIM: Minimally invasive diagnostic techniques would be useful in the preoperative diagnosis of patients with hypertension and ischemic renal disease. The aim of our study was to compare color Doppler sonography (CDS), and magnetic resonance angiography (MRA) with the reference standard, digital subtraction angiography (DSA), in the diagnosis of renal artery stenosis. METHODS: Thirty-nine patients with arterial hypertension and monolateral or bilateral renal artery stenosis documented by CDS underwent renal artery MRA and then DSA during corrective percutaneous transluminal angioplasty. CDS and MRA scans were evaluated by 3 independent observers who studied 78 main renal arteries. Stenosis of 70% or more were regarded as significant. Sensitivity, specificity, positive and negative predictive values and two-sided 95% confidence intervals of CDS and MRA for the detection of significant renal artery stenosis were calculated. The statistical significance of the differences in sensitivities between CDS and MRA was assessed by means of the kappa test (< or =1). RESULTS: CDS and MRA, therefore, both achieved 97.6% sensitivity and 100% specificity for diagnosing stenoses at the origin of the renal artery; CDS yielded 100% sensitivity and 97.1% specificity and MRA 87.5% sensitivity and 98.6% specificity for diagnosing stenosis in the intermediate distal segments. CONCLUSIONS: Statistically significant differences between CDS and MRA in the diagnosis of renal artery stenosis have not been observed. However, according to our experience, CDS is the preferred technique because it also provides useful information about the development of kidney disease before correction.     

Variable selection under multiple imputation using the bootstrap in a prognostic study

Background  

Missing data is a challenging problem in many prognostic studies. Multiple imputation (MI) accounts for imputation uncertainty that allows for adequate statistical testing. We developed and tested a methodology combining MI with bootstrapping techniques for studying prognostic variable selection.     

Retrospective attenuation correction of PET data for radiotherapy planning using a free breathing CT.

PURPOSE: To evaluate the image quality of retrospectively attenuation corrected Positron Emission Tomography (PET) scans used for gross tumor volume (GTV) delineation in lung cancer patients. MATERIALS AND METHODS: Data of 13 lymph node positive lung cancer patients were acquired on separate CT and PET scanners under free breathing conditions (for radiotherapy planning). First we determined a protocol for CT/PET registration. Second, we compared the image quality of attenuation-corrected PET images using positron transmission images and CT images, in terms of signal-to-noise ratio (SNR) and lesion-to-background ratio (contrast). RESULTS: The largest differences between manual and automatic CT/PET registration were found in the anterior-posterior direction with a mean of 1.8 mm (SD 1.0 mm). Differences in rotations were always smaller than 1.0 degrees . The attenuation-corrected images using CT showed a larger SNR (mean 30%, SD 17%) and larger contrast (mean 14.0%, SD 8.5%) compared to attenuation-corrected images using positron transmission. For lymph nodes, the mean contrast was 16% (SD 6.4%) larger. CONCLUSIONS: This study demonstrated that attenuation correction based on CT provides a better image quality for GTV delineation than when using positron transmission for attenuation correction. Retrospective attenuation correction of PET scans based on registered CT is a good alternative for a dedicated PET/CT scanner if a free-breathing CT is available, e.g., for radiotherapy planning, and allows the use of CT with diagnostic quality for attenuation correction.     

Mathematical modelling of infection and disease due to Neisseria meningitidis and Neisseria lactamica

BACKGROUND: Invasive meningococcal disease, due to Neisseria meningitidis, is an important cause of morbidity and mortality in young children and adolescents. Nasopharyngeal carriage of meningococci (MC), is most prevalent in young adults whereas carriage of Neisseria lactamica (LC), a related non-pathogenic organism, is most prevalent in young children. The objective of this study was to use modelling techniques to test hypotheses on the processes that govern the incidence of meningococcal disease (MD). METHODS: Deterministic compartmental models were fitted to age structured data sets of MC, LC and MD. RESULTS: The model most consistent with the available data sets is one where LC inhibits MC, an inhibition that lasts for a mean of 4.7 years. The hypothesis that LC also acts as a natural immunogen against MD was consistent with this model. The second peak of MD observed among adolescents could be due to the peak in the acquisition of MC in this age group. CONCLUSIONS: The role of LC as a natural immunogen against asymptomatic and symptomatic meningococcal infection was consistent with available field data. If the introduction of novel meningococcal vaccines into a population changes the prevalence of MC or LC, this could have a substantial impact on the effectiveness of immunization programmes. This paper demonstrates the potential utility of modelling to estimate these effects.