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Systems genetics has begun to tackle the complexity of insulin resistance by capitalising on computational advances to study high-diversity populations. “Diversity Outbred in Australia (DOz)” is a population of genetically unique mice with profound metabolic heterogeneity. We leveraged this variance to explore skeletal muscle’s contribution to whole-body insulin action through metabolic phenotyping and skeletal muscle proteomics of 215 DOz mice. Linear modelling identified 553 proteins that associated with whole-body insulin sensitivity (Matsuda Index) including regulators of endocytosis and muscle proteostasis. To enrich for causality, we refined this network by focussing on negatively associated, genetically regulated proteins, resulting in a 76-protein fingerprint of insulin resistance. We sought to perturb this network and restore insulin action with small molecules by integrating the Broad Institute Connectivity Map platform andin vitroassays of insulin action using the Prestwick chemical library. These complimentary approaches identified the antibiotic thiostrepton as an insulin resistance reversal agent. Subsequent validation inex vivoinsulin resistant mouse muscle, and palmitate induced insulin resistant myotubes demonstrated potent insulin action restoration, potentially via up-regulation of glycolysis. This work demonstrates the value of a drug-centric framework to validate systems level analysis by identifying potential therapeutics for insulin resistance.

Replacement of pancreatic beta-cells is one of the most promising treatment options for treatment of type 1 diabetes (T1D), even though, toxic immunosuppressive drugs are required. In this study, we aim to deliver allogeneic beta-cell therapies without antirejection drugs using a bioengineered hybrid device that contains microencapsulated beta-cells inside 3D polycaprolactone (PCL) scaffolds printed using melt electrospin writing (MEW). Mouse beta-cell (MIN6) pseudoislets and QS mouse islets are encapsulated in alginate microcapsules, without affecting viability and insulin secretion. Microencapsulated MIN6 cells are then seeded within 3D MEW scaffolds, and these hybrid devices implanted subcutaneously in streptozotocin-treated diabetic NOD/SCID and BALB/c mice. Similar to NOD/SCID mice, blood glucose levels (BGL) are lowered from 30.1 to 4.8 mM in 25-41 days in BALB/c. In contrast, microencapsulated islets placed in prevascularized MEW scaffold 3 weeks after implantation in BALB/c mice normalize BGL (Impact statementThe retrievable 3D printed PCL scaffold we have produced promotes vascularization when implanted subcutaneously and allows seeded microencapsulated insulin-producing cells to normalize blood glucose of diabetic mice for at least 2 months, without the need for antirejection drugs to be administered. The scaffold is scalable for possible human use, but will require modification to ensure that normalization of blood glucose levels can be maintained long term.

OBJECTIVE Several studies support associations between relative leukocyte telomere length (rLTL), a biomarker of biological aging and type 2 diabetes. This study investigates the relationship between rLTL and the risk of glycemic progression in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS In this cohort study, consecutive Chinese patients with type 2 diabetes (N = 5,506) from the Hong Kong Diabetes Register with stored baseline DNA and available follow-up data were studied. rLTL was measured using quantitative PCR. Glycemic progression was defined as the new need for exogenous insulin. RESULTS The mean (SD) age of the 5,349 subjects was 57.0 (13.3) years, and mean (SD) follow-up was 8.8 (5.4) years. Baseline rLTL was significantly shorter in the 1,803 subjects who progressed to insulin requirement compared with the remaining subjects (4.43 ± 1.16 vs. 4.69 ± 1.20). Shorter rLTL was associated with a higher risk of glycemic progression (hazard ratio [95% CI] for each unit decrease [to ∼0.2 kilobases]: 1.10 [1.06–1.14]), which remained significant after adjusting for confounders. Baseline rLTL was independently associated with glycemic exposure during follow-up (β = −0.05 [−0.06 to −0.04]). Each 1-kilobase decrease in absolute LTL was on average associated with a 1.69-fold higher risk of diabetes progression (95% CI 1.35–2.11). Two-sample Mendelian randomization analysis showed per 1-unit genetically decreased rLTL was associated with a 1.38-fold higher risk of diabetes progression (95% CI 1.12–1.70). CONCLUSIONS Shorter rLTL was significantly associated with an increased risk of glycemic progression in individuals with type 2 diabetes, independent of established risk factors. Telomere length may be a useful biomarker for glycemic progression in people with type 2 diabetes.

Aims/hypothesis Few large-scale prospective studies have investigated associations between relative leucocyte telomere length (rLTL) and kidney dysfunction in individuals with type 2 diabetes. We examined relationships between rLTL and incident end-stage kidney disease (ESKD) and the slope of eGFR decline in Chinese individuals with type 2 diabetes. Methods We studied 4085 Chinese individuals with type 2 diabetes observed between 1995 and 2007 in the Hong Kong Diabetes Register with stored baseline DNA and available follow-up data. rLTL was measured using quantitative PCR. ESKD was diagnosed based on the ICD-9 code and eGFR. Results In this cohort (mean ± SD age 54.3 ± 12.6 years) followed up for 14.1 ± 5.3 years, 564 individuals developed incident ESKD and had shorter rLTL at baseline (4.2 ± 1.2 vs 4.7 ± 1.2, p n = 3521). On Cox regression analysis, each ∆∆Ct decrease in rLTL was associated with an increased risk of incident ESKD (HR 1.21 [95% CI 1.13, 1.30], p 1c, lipids, renal function and other risk factors (HR 1.11 [95% CI 1.03, 1.19], p = 0.007). Shorter rLTL at baseline was associated with rapid decline in eGFR (>4% per year) during follow-up (unadjusted OR 1.22 [95% CI 1.15, 1.30], p p = 0.024). Conclusions/interpretation rLTL is independently associated with incident ESKD and rapid eGFR loss in individuals with type 2 diabetes. Telomere length may be a useful biomarker for the progression of kidney function and ESKD in type 2 diabetes. Graphical abstract

Mitochondria play a key role in the normal function of the heart as well as in the pathogenesis of diseases. We report analysis of common genetic variations contributing to mitochondrial and heart functions using an integrative proteomics approach in a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP). We performed a whole heart proteomic analysis in the HMDP (72 strains, n=2-3 mice) and retrieved 840 mitochondrial proteins (quantified in ≥50 strains). High-resolution association mapping on their respective abundance levels identified three trans-acting genetic loci, located on chromosome (chr) 7, chr13 and chr17, that control distinct classes of mitochondrial proteins as well as heart hypertrophy. Follow-up high resolution regional mapping identified NDUFS4, LRPPRC and COQ7 as the candidate genes for chr13, chr17 and chr7 loci, respectively, and both experimental and statistical analyses supported their causal roles. Variations of all three were associated with heart mass in two independent heart stress models, namely, isoproterenol (ISO)-induced heart failure and diet-induced obesity (DIO) models. To identify the aspects of mitochondrial metabolism regulated by these loci, we constructed co-expression protein networks using weighted gene co-expression network analysis (WGCNA). DAVID enrichment analyses of genes regulated by each of the loci revealed that the chr13 locus was highly enriched for complex-I proteins (24 proteins, P = 2.2E-61), the chr17 locus for mitochondrial ribonucleoprotein complex (17 proteins, P = 3.1E-25) and the chr7 locus for ubiquinone biosynthesis (3 proteins, P = 6.9E-05). These results indicate that common variations of certain mitochondrial proteins can act in trans to influence mitochondrial functions and contribute to heart hypertrophy, elucidating mechanisms that may underlie genetic susceptibility to heart failure in human populations.

Background: Mitochondrial DNA (Mt-DNA) copy number (mtDNA-CN) has been proposed as a marker of diabetic kidney disease (DKD) . Most studies are in type 2 diabetes. We determined mtDNA-CN in adults with type 1 diabetes vs. non-diabetic subjects, including associations with complications and risk factors. Methods: Cross-sectional study: 178 T1D adults (mean (SD) age: 38 (14) yrs, 21 (14) yrs T1D, HbA1c: 8.0 (1.5) %, 36% with complications (CX+)) ; 132 non-diabetic adults (CON) (age: 37 (14) yrs, HbA1c: 5.1 (0.4) %) . mtDNA-CN by RT-PCR (ScienCell, Carlsbad, CA) in DNA from whole blood samples. Results: T1D vs. CON: Median (LQ, UQ) mtDNA-CN in T1D vs. CON: 270.8 (189.4, 348.1) vs. 320.5 (264.4, 410.5) ; p Conclusion: T1D per se is associated with lower mtDNA-CN than CON, particularly with DKD. Higher mtDNA-CN in T1D is associated with detectable C-peptide. Age and inflammation related factors are associated with mtDNA-CN. Longitudinal and intervention studies are merited. Disclosure A.S.Januszewski: None. L.Carroll: None. Y.W.Loh: None. D.N.O'neal: None. A.Jenkins: Advisory Panel; Abbott Diabetes, Amgen Inc., Board Member; Insulin for Life , International Diabetes Federation Western Pacific Region, Research Support; JDRF, Medtronic, Mylan N.V., NHMRC Australia.

This paper investigates intonation in the urban dialect of Liverpool, Scouse. Scouse is reported to be part of a group of dialects in the north of the UK where rising contours in declaratives are a traditional aspect of the dialect. This intonation is typologically unusual and has not been the subject of detailed previous research. Here, we present such an analysis in comparison with Manchester, a city less than 40 miles from Liverpool but with a noticeably different prosody. Our analysis confirms reports that rising contours are the most common realization for declaratives in Liverpool, specifically a low rise where final high pitch is not reached until the end of the phrase. Secondly, we consider the origin of declarative rises in Scouse with reference to the literature on new dialect formation. Our demographic analysis and review of previous work on relevant dialects suggests that declarative rises were not the majority variant when Scouse was formed but may have been adopted for facilitating communication in a diverse new community. We highlight this contribution of intonational data to research on phonological aspects of new dialect formation, which have largely considered segmental phonology or timing previously.

Disulfide bonds are a key determinant of protein structure and function, and highly conserved across proteomes. They are particularly abundant in extracellular proteins, including those with critical structural, ligand binding or receptor function. We demonstrate that oxidation of protein disulfides induces polymerization, and results in oxygen incorporation into the former disulfide via thiosulfinate generation. These intermediates, which have half-lives of several hours in vitro, undergo secondary reactions that cleave the disulfide bond, by irreversible hydrolysis to sulfinic and sulfonic acids, or reaction with thiols in a process that yields thiolated proteins (e.g. glutathionylated species in the case of reaction with glutathione). The adducts have been characterized by mass spectrometry (as ions corresponding to the addition of 306 and 712 Da for addition of one and two glutathione molecules, respectively) and immunoblotting. These modifications can be induced by multiple biologically-important oxidants, including HOCl, ONOOH, and H2O2, and on multiple proteins, demonstrating that this is a common disulfide modification pathway. Addition of glutathione to give glutathionylated proteins, can be reversed by reducing systems (e.g. tris(2-carboxyethyl)phosphine), but this does not repair the original disulfide bond. Exposure of human plasma to these modifying agents increases protein glutathionylation, demonstrating potential in vivo relevance. Overall these data provide evidence for a novel and facile route to glutathionylated proteins involving initial oxidation of a disulfide to a thiosulfinate followed by rapid reaction with GSH (‘oxidant-mediated thiol-disulfide exchange’). These data elucidate a novel pathway for protein glutathionylation that may have significant implications for redox biology and cell signaling.

Skeletal muscle and adipose tissue insulin resistance are major drivers of metabolic disease. To uncover pathways involved in insulin resistance, specifically in these tissues, we leveraged the metabolic diversity of different dietary exposures and discrete inbred mouse strains. This revealed that muscle insulin resistance was driven by gene-by-environment interactions and was strongly correlated with hyperinsulinemia and decreased levels of ten key glycolytic enzymes. Remarkably, there was no relationship between muscle and adipose tissue insulin action. Adipocyte size profoundly varied across strains and diets, and this was strongly correlated with adipose tissue insulin resistance. The A/J strain, in particular, exhibited marked adipocyte insulin resistance and hypertrophy despite robust muscle insulin responsiveness, challenging the role of adipocyte hypertrophy per se in systemic insulin resistance. These data demonstrate that muscle and adipose tissue insulin resistance can occur independently and underscore the need for tissue-specific interrogation to understand metabolic disease.

The phosphoinositide 3-kinase (PI3K)-Akt network is tightly controlled by feedback mechanisms that regulate signal flow and ensure signal fidelity. A rapid overshoot in insulin-stimulated recruitment of Akt to the plasma membrane has previously been reported, which is indicative of negative feedback operating on acute timescales. Here, we show that Akt itself engages this negative feedback by phosphorylating insulin receptor substrate (IRS) 1 and 2 on a number of residues. Phosphorylation results in the depletion of plasma membrane-localised IRS1/2, reducing the pool available for interaction with the insulin receptor. Together these events limit plasma membrane-associated PI3K and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) synthesis. We identified two Akt-dependent phosphorylation sites in IRS2 at S306 (S303 in mouse) and S577 (S573 in mouse) that are key drivers of this negative feedback. These findings establish a novel mechanism by which the kinase Akt acutely controls PIP3 abundance, through post-translational modification of the IRS scaffold., eLife digest For the body to work properly, cells must constantly ‘talk’ to each other using signalling molecules. Receiving a chemical signal triggers a series of molecular events in a cell, a so-called ‘signal transduction pathway’ that connects a signal with a precise outcome. Disturbing cell signalling can trigger disease, and strict control mechanisms are therefore in place to ensure that communication does not break down or become erratic. For instance, just as a thermostat turns off the heater once the right temperature is reached, negative feedback mechanisms in cells switch off signal transduction pathways when the desired outcome has been achieved. The hormone insulin is a signal for growth that increases in the body following a meal to promote the storage of excess blood glucose (sugar) in muscle and fat cells. The hormone binds to insulin receptors at the cell surface and switches on a signal transduction pathway that makes the cell take up glucose from the bloodstream. If the signal is not engaged diseases such as diabetes develop. Conversely, if the signal cannot be adequately switched of cancer can develop. Determining exactly how insulin works would help to understand these diseases better and to develop new treatments. Kearney et al. therefore set out to examine the biochemical ‘fail-safes’ that control insulin signalling. Experiments using computer simulations of the insulin signalling pathway revealed a potential new mechanism for negative feedback, which centred on a molecule known as Akt. The models predicted that if the negative feedback were removed, then Akt would become hyperactive and accumulate at the cell’s surface after stimulation with insulin. Further manipulation of the ‘virtual’ insulin signalling pathway and studies of live cells in culture confirmed that this was indeed the case. The cell biology experiments also showed how Akt, once at the cell surface, was able to engage the negative feedback and shut down further insulin signalling. Akt did this by inactivating a protein required to pass the signal from the insulin receptor to the rest of the cell. Overall, this work helps to understand cell communication by revealing a previously unknown, and critical component of the insulin signalling pathway.

Hypochlorous acid (HOCl) is a highly reactive, toxic species generated by neutrophils via the action of myeloperoxidase in order to destroy invading pathogens. However, when HOCl is produced inappropriately, it can damage host tissue and proteins and plays a role in the initiation and progression of disease. Carnosine, a peptide of β-alanine and histidine, has been shown to react rapidly with HOCl yielding monochloramines and can undergo intramolecular transchlorination. The current study examines the kinetics and pH dependence of the reactions of carnosine and novel structural derivatives with HOCl and the occurrence of intra- and intermolecular transchlorination processes. We demonstrate that the transchlorination reactions of carnosine are pH dependent, with intramolecular transfer favored at higher pH. Carcinine, having a structure identical to carnosine though lacking the carboxylic acid group of the histidine residue, reacts with HOCl and forms monochloramines though intramolecular transfer reactions are not observed, and this is supported by computational modeling. Novel analogues with one (carnosine+1) and two (carnosine+2) methylene groups in the alkyl chain of the β-alanine react with HOCl to yield monochloramines that undergo transchlorinations to yield a mixture of mono- and dichloramines. The latter are stable over 24 h. The ability of carnosine and derivatives to react rapidly with HOCl to give long-lived, poorly reactive, species may prevent damage to proteins and other targets at sites of inflammation.

Inter- and intra-molecular crosslinks can generate protein dysfunction, and are associated with protein aggregate accumulation in aged and diseased tissues. Crosslinks formed between multiple amino acid side chains can be reversible or irreversible. Disulfides formed either enzymatically, or as a result of oxidant-mediated reactions, are a major class of reversible crosslinks. Whilst these are commonly generated via oxidation of Cys thiol groups, they are also formed by ‘oxidant-mediated thiol-disulfide reactions’ via initial disulfide oxidation to a thiosulfinate or zwitterionic peroxide, and subsequent reaction with another thiol including those on other proteins. This generates new intermolecular protein-protein crosslinks. Here we demonstrate that photooxidation, or reaction with the biological oxidants HOCl and ONOOH, of the single disulfide present in the major human plasma inflammatory protein, C-reactive protein (CRP) can give rise to reversible disulfide bond formation with human serum albumin (HSA). This occurs in an oxidant dose-, or illumination-time-, dependent manner. These CRP-HSA crosslinks are formed both in isolated protein systems, and in fresh human plasma samples containing high, but not low, levels of CRP. The inter-protein crosslinks which involve Cys36 of CRP and Cys34 of HSA, have been detected by both immunoblotting and mass spectrometry (MS). The yield of protein-protein crosslinks depends on the nature and extent of oxidant exposure, and can be reversed by dithiothreitol and tris(2-carboxyethyl)phosphine hydrochloride. These data indicate that oxidation of disulfide bonds in proteins can be a source of novel inter-protein crosslinks, which may help rationalize the accumulation of crosslinked proteins in aged and diseased tissues., Graphical abstract Image 1, Highlights • C-reactive protein (CRP) is a major acute phase inflammatory protein in human plasma. • Oxidation of the single Cys36-Cys97 disulfide in CRP generates reactive intermediates. • The oxidized disulfide reacts with Cys34 of human serum albumin to forms a new crosslink. • The inter-protein CRP-HSA crosslink has been characterized by immunoblotting and LS-MS/MS. • This novel crosslink may be a long-lived plasma marker of inflammation-induced damage.

Cross-links formed within and between proteins are a major cause of protein dysfunction, and are postulated to drive the accumulation of protein aggregates in some human pathologies. Cross-links can be formed from multiple residues and can be reversible (usually sulfur-sulfur bonds) or irreversible (typically carbon-carbon or carbon-heteroatom bonds). Disulfides formed from oxidation of two Cys residues are widespread, with these formed both deliberately, via enzymatic reactions, or as a result of unintended oxidation reactions. We have recently demonstrated that new protein-glutathione mixed disulfides can be formed through oxidation of a protein disulfide to a thiosulfinate, and subsequent reaction of this species with glutathione. Here we investigate whether similar reactions occur between an oxidized protein disulfide, and a Cys residues on a second protein, to give novel protein cross-links. Singlet oxygen (1O2)-mediated oxidation of multiple proteins (α-lactalbumin, lysozyme, beta-2-microglobulin, C-reactive protein), and subsequent incubation with the Cys-containing protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH), generates inter-protein cross-links as detected by SDS-PAGE, immunoblotting and mass spectrometry (MS). The cross-link yield is dependent on the 1O2 concentration, the presence of the original protein disulfide bond, and the free Cys on GAPDH. MS with 18O-labeling has allowed identification of the residues involved in some cases (e.g. Cys25 from the Cys25-Cys80 disulfide in beta-2-microglobulin, with Cys149 or Cys244 of GAPDH). The formation of these cross-links results in a loss of GAPDH enzymatic activity. These data provide ‘proof-of-concept’ for a novel mechanism of protein cross-link formation which may help rationalize the accumulation of cross-linked proteins in multiple human pathologies., Graphical abstract Image 1, Highlights • Disulfide bonds (DSBs) are critical to protein structure and function. • DSBs are rapidly oxidized by singlet oxygen and other oxidants to reactive intermediates. • These intermediates react with Cys-containing proteins to give new protein-protein cross-links. • This novel disulfide cross-linking pathway affects the functional activity of the proteins. • These cross-links can be diminished by reductants, but this does not repair the DSB damage.

Disulfide bonds play a key function in determining the structure of proteins, and are the most strongly conserved compositional feature across proteomes. They are particularly common in extracellular environments, such as the extracellular matrix and plasma, and in proteins that have structural (e.g. matrix) or binding functions (e.g. receptors). Recent data indicate that disulfides vary markedly with regard to their rate of reaction with two-electron oxidants (e.g. HOCl, ONOOH), with some species being rapidly and readily oxidized. These reactions yielding thiosulfinates that can react further with a thiol to give thiolated products (e.g. glutathionylated proteins with glutathione, GSH). Here we show that these ‘oxidant-mediated thiol-disulfide exchange reactions’ also occur during photo-oxidation reactions involving singlet oxygen (1O2). Reaction of protein disulfides with 1O2 (generated by multiple sensitizers in the presence of visible light and O2), yields reactive intermediates, probably zwitterionic peroxyl adducts or thiosulfinates. Subsequent exposure to GSH, at concentrations down to 2 μM, yields thiolated adducts which have been characterized by both immunoblotting and mass spectrometry. The yield of GSH adducts is enhanced in D2O buffers, and requires the presence of the disulfide bond. This glutathionylation can be diminished by non-enzymatic (e.g. tris-(2-carboxyethyl)phosphine) and enzymatic (glutaredoxin) reducing systems. Photo-oxidation of human plasma and subsequent incubation with GSH yields similar glutathionylated products with these formed primarily on serum albumin and immunoglobulin chains, demonstrating potential in vivo relevance. These reactions provide a novel pathway to the formation of glutathionylated proteins, which are widely recognized as key signaling molecules, via photo-oxidation reactions., Graphical abstract Image 1, Highlights • Disulfide bonds (DSBs) are critical to protein structure and function. • DSBs are rapidly oxidized by singlet oxygen and other oxidants to reactive species. • These DSB-derived intermediates react with GSH to give glutathionylated proteins. • Glutathionylation can be diminished by reductants, but does not repair DSB damage. • Oxidation of human plasma DSBs gives glutathionylated albumin and immunoglobulins.

Few studies have investigated the relationship between rLTL and mortality in patients with type 2 diabetes in a large prospective study, particularly in the Asian population. This study investigates the relationship between rLTL and the risk of death in Chinese patients with type 2 diabetes.Consecutive Chinese patients with type 2 diabetes (N = 5349) from the Hong Kong Diabetes Register with stored baseline DNA and available follow-up data were studied. rLTL was measured using a quantitative polymerase chain reaction. Mortality and clinical outcomes were obtained based on ICD-9 codes.The mean (SD) age of the subjects was 57.5 (13.3) years and mean (SD) follow-up duration was 13.4 (5.5) years. Baseline rLTL was significantly shorter in the 1925 subjects who subsequently died compared with the remaining subjects (4.3 ± 1.2 vs. 4.7 ± 1.2, P 0.001). Shorter rLTL was associated with a higher risk of mortality (HR: 1.19 (1.14-1.23), P 0.001), which remained significant after adjusting for traditional risk factors.Shorter rLTL was significantly associated with an increased risk of all-cause and CVD mortality in patients with type 2 diabetes, independent of established risk factors. Telomere length may be a useful biomarker for mortality risk in patients with type 2 diabetes.

Selenium compounds have been identified as potential oxidant scavengers for biological applications due to the nucleophilicity of Se, and the ease of oxidation of the selenium centre. Previous studies have reported apparent second order rate constants for a number of oxidants (e.g. HOCl, ONOOH) with some selenium species, but these data are limited. Here we provide apparent second order rate constants for reaction of selenols (RSeH), selenides (RSeR′) and diselenides (RSeSeR’) with biologically-relevant oxidants (HOCl, H2O2, other peroxides) as well as overall consumption data for the excited state species singlet oxygen (1O2). Selenols show very high reactivity with HOCl and 1O2, with rate constants > 108 M−1 s−1, whilst selenides and diselenides typically react with rate constants one- (selenides) or two- (diselenides) orders of magnitude slower. Rate constants for reaction of diselenides with H2O2 and other hydroperoxides are much slower, with k for H2O2 being

Telomeres are regions of repetitive nucleotide sequences at the ends of chromosomes. Telomere length is a marker of DNA damage, which is often considered a biomarker for biological ageing, and has also been linked with cardiovascular disease, diabetes, and cancer. Emerging studies have highlighted the role of genetic and environmental factors, and explored the effect of modulating telomere length. We provide an overview of studies to date on diabetes and telomere length, and compare different methods and assays for evaluating telomere length and telomerase activity. We highlight the limitations of current studies and areas that warrant further research to unravel the link between diabetes and telomere length. The value of adding telomere length to clinical risk factors to improve risk prediction of diabetes and related complications also merits further investigation.

Myeloperoxidase produces strong oxidants during the immune response to destroy invading pathogens. However, these oxidants can also cause tissue damage, which contributes to the development of numerous inflammatory diseases. Selenium containing compounds, including selenomethionine (SeMet) and 1,4-anhydro-5-seleno-D-talitol (SeTal), react rapidly with different MPO-derived oxidants to form the respective selenoxides (SeMetO and SeTalO). This study investigates the susceptibility of these selenoxides to undergo reduction back to the parent compounds by intracellular reducing systems, including glutathione (GSH) and the glutathione reductase and thioredoxin reductase systems. GSH is shown to reduce SeMetO and SeTalO, with consequent formation of GSSG with apparent second order rate constants, k2, in the range 103–104 M−1 s−1. Glutathione reductase reduces both SeMetO and SeTalO at the expense of NADPH via formation of GSSG, whereas thioredoxin reductase acts only on SeMetO. The presence of SeMet and SeTal also increased the rate at which NADPH was consumed by the glutathione reductase system in the presence of N-chloramines. In contrast, the presence of SeMet and SeTal reduced the rate of NADPH consumption by the thioredoxin reductase system after addition of N-chloramines, consistent with the rapid formation of selenoxides, but only slow reduction by thioredoxin reductase. These results support a potential role of seleno compounds to act as catalytic scavengers of MPO-derived oxidants, particularly in the presence of glutathione reductase and NADPH, assuming that sufficient plasma levels of the parent selenoether can be achieved in vivo following supplementation., Graphical abstract fx1, Highlights • Selenoxides react with thiols including GSH by a two-step mechanism. • The reaction is proposed to occur via a selenosulfide intermediate. • The thioredoxin reductase system recycles selenomethionine selenoxide. • The glutathione reductase system reduces both N-chloramines and selenoxides. • Selenoxides can increase the reduction of N-chloramines by antioxidant systems.

Objective: Despite therapeutic advances, type 1 diabetes (T1D) is associated with a risk of development of micro- and macrovascular complications. Early treatment of complications is associated with a more favorable prognosis, hence biomarkers to enable early detection and to monitor treatments may be useful. Methods: Plasma (EDTA) samples were obtained from 30 adult (M/F = 20/10) individuals with T1D, age 42±16 years, T1D duration 24±11 years, HbA1c 7.5±1.2% and BMI 26.5±4.0 kg/m2 (15 with microvascular complications (retinopathy or nephropathy) - CX+, and 15 without complications - CX-) and compared with 15 nondiabetic controls (CON, matched age, gender, smoking and BMI). T1D CX+ and CX- individuals were matched for age, gender, diabetes duration, smoking, BMI, HbA1c and insulin therapy modality (CSII/MDI). In these discovery cohort samples, profiling of 754 miRs was done using a high throughput probe based quantitative PCR on nanofluidics Open Array platform . Results were analyzed using independent T test, Mann-Whitney test and classification trees. Statistical analysis was undertaken using R (ver. 3.5.1) and XLStat (ver. 2018.6). Results: Of 754 available miRs on the array, 186 miRs were detectable in plasma. Using an unbiased approach expression of 32 miRs differed significantly in CON vs. T1D and 16 miRs were differentially expressed between CX+ and CX- T1D subjects. Using a Random Forest wrapper algorithm 5 miRs were identified with importance for segregating CX+ vs. CX- status: miR-483-5p, miR-328, miR-1274B, miR-7 and miR-30a-5p. In logistic regression those 5 miRs provided a ROC curve with AUC=0.90 for the CX+ vs. CX- discrimination. Conclusion: In a discovery analysis of well- matched CX+ and CX- selected miRs provided good discrimination between T1D CX status. Validation studies in a larger cohort of cross-sectional and longitudinal samples are in progress. Disclosure A.S. Januszewski: None. E.S. Scott: None. M. Joglekar: None. L. Carroll: None. R. Farr: None. W. Wong: None. D.N. O’Neal: None. C. Karschimkus: None. G. Fulcher: Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Research & Development, Merck Sharp & Dohme Corp., Novo Nordisk Inc. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Research & Development, Merck Sharp & Dohme Corp., Novo Nordisk Inc. Research Support; Self; Novo Nordisk Inc. A. Hardikar: None. A.J. Jenkins: Advisory Panel; Self; Abbott, Australian Diabetes Society, Medtronic. Research Support; Self; Abbott, GlySens Incorporated, Medtronic, Mylan. Speaker’s Bureau; Self; Eli Lilly and Company, Novo Nordisk Inc. Funding Sydney Medical School Foundation; National Health and Medical Research Council of Australia

Type 1 diabetes, characterized by autoimmune destruction of pancreatic beta cells, affects 41 million people worldwide. Beta cell replacement therapies have immense potential as a treatment option because pancreatic progenitors derived from human pluripotent stem cells can provide a near limitless supply of transplantable tissue. The key limitation of this approach is the need for lifelong use of immunosuppressive drugs that have undesirable side effects. Microencapsulation is an option for providing protection for transplanted cells from mechanical stress and immune attack. Traditionally, pluripotent cells are differentiated on a 2D matrix before being transferred into an immunoisolation device. Here, we describe a method of differentiating pluripotent stem cells into pancreatic progenitors while the cells are encapsulated in alginate microspheres. This method provides several advantages including the need for fewer steps compared to the traditional approach, protection against mechanical/physical damage during differentiation in bioreactors, and immune-protection of cells once transplanted into the host.

The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employing high concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2, 20% and 100% O2 atmospheres. Dimerization of Trp was a major pathway under the N2 atmosphere, though this occurred with a low yield (DφTrp = 5.9 × 10−3), probably as a result of extensive back electron transfer reactions between RF•- and Trp(H)•+. The presence of O2 decreased the extent of this back electron transfer reaction, and the extent of Trp dimerization. This difference is attributed to the formation of O2•- (generated via electron transfer from RF•- to O2) which reacts rapidly with Trp• leading to extensive consumption of the parent amino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols, diols) of Trp, as detected by LC-MS. Thus, it appears that the first step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the amino acid and 3RF, with the presence of O2 modulating the subsequent reactions and the products formed, as a result of O2•- formation. These data have potential biological significance as LED systems and RF-based treatments have been proposed for the treatment of pathological myopia and keratitis.

The present work examined the role of Tyr and Trp in oxidative modifications of caseins, the most abundant milk proteins, induced by peroxyl radicals (ROO•). We hypothesized that the selectivity of ROO• and the high flexibility of caseins (implying a high exposure of Tyr and Trp residues) would favor radical-radical reactions, and di-tyrosine (di-Tyr) and di-tryptophan (di-Trp) formation. Solutions of α- and β-caseins were exposed to ROO• from thermolysis and photolysis of AAPH (2,2′-azobis(2-methylpropionamidine)dihydrochloride). Oxidative modifications were examined using electrophoresis, western blotting, fluorescence, and chromatographic methodologies with diode array, fluorescence and mass detection. Exposure of caseins to AAPH at 37 °C gave fragmentation, cross-linking and protein aggregation. Amino acid analysis showed consumption of Trp, Tyr, Met, His and Lys residues. Quantification of Trp and Tyr products, showed low levels of di-Tyr and di-Trp, together with an accumulation of carbonyls indicating that casein aggregation is, at least partly, associated with secondary reactions between carbonyls and Lys and His residues. AAPH photolysis, which generates a high flux of free radicals increased the extent of formation of di-Tyr in both model peptides and α- and β- caseins; di-Trp was only detected in peptides and α-casein. Thus, in spite of the high flexibility of caseins, which would be expected to favor radical-radical reactions, the low flux of ROO• generated during AAPH thermolysis disfavours the formation of dimeric radical-radical cross-links such as di-Tyr and di-Trp, instead favoring other O2-dependent crosslinking pathways such as those involving secondary reactions of initial carbonyl products.

Oxidative damage is a common process in many biological systems and proteins are major targets for damage due to their high abundance and very high rate constants for reaction with many oxidants (both radicals and two-electron species). Tryptophan (Trp) residues on peptides and proteins are a major sink for a large range of biological oxidants as these side-chains have low radical reduction potentials. The resulting Trp-derived indolyl radicals (Trp•) have long lifetimes in some circumstances due to their delocalized structures, and undergo only slow reaction with molecular oxygen, unlike most other biological radicals. In contrast, we have shown previously that Trp• undergo rapid dimerization. In the current study, we show that Trp• also undergo very fast reaction with superoxide radicals, O2•−, with k 1–2 × 109 M−1 s−1. These values do not alter dramatically with peptide structure, but the values of k correlate with overall peptide positive charge, consistent with positive electrostatic interactions. These reactions compete favourably with Trp• dimerization and O2 addition, indicating that this may be a major fate in some circumstances. The Trp• + O2•− reactions occur primarily by addition, rather than electron transfer, with this resulting in high yields of Trp-derived hydroperoxides. Subsequent degradation of these species, both stimulated and native decay, gives rise to N-formylkynurenine, kynurenine, alcohols and diols. These data indicate that reaction of O2•− with Trp• should be considered as a major pathway to Trp degradation on peptides and proteins subjected to oxidative damage.

Selenium is an essential trace element in mammals, with the majority specifically encoded as seleno-L-cysteine into a range of selenoproteins. Many of these proteins play a key role in modulating oxidative stress, via either direct detoxification of biological oxidants, or repair of oxidised residues. Both selenium- and sulphur-containing residues react readily with the wide range of oxidants (including hydrogen peroxide, radicals, singlet oxygen and hypochlorous, hypobromous, hypothiocyanous and peroxynitrous acids) that are produced during inflammation and have been implicated in the development of a range of inflammatory diseases. Whilst selenium has similar properties to sulphur, it typically exhibits greater reactivity with most oxidants, and there are considerable differences in the subsequent reactivity and ease of repair of the oxidised species that are formed. This review discusses the chemistry of low-molecular-mass organoselenium compounds (e.g. selenoethers, diselenides and selenols) with inflammatory oxidants, with a particular focus on the reaction kinetics and product studies, with the differences in reactivity between selenium and sulphur analogues described in the selected examples. These data provide insight into the therapeutic potential of low-molecular-mass selenium-containing compounds to modulate the activity of both radical and molecular oxidants and provide protection against inflammation-induced damage. Progress in their therapeutic development (including modulation of potential selenium toxicity by strategic design) is demonstrated by a brief summary of some recent studies where novel organoselenium compounds have been used as wound healing or radioprotection agents and in the prevention of cardiovascular disease.

Selenium is an essential trace element in mammals, as a result of the requirement for the encoded amino acid seleno-l-cysteine (Sec) that is present in a range of selenoproteins. Selenium is also present in other forms in biological systems, including selenomethionine and inorganic species. While the role of some Sec-containing proteins has yet to be fully resolved, some of these, in particular isoforms of the thioredoxin reductase, glutathione peroxidase and methionine sulfoxide reductases, play key roles in modulating oxidative stress. Consequently, there is considerable interest in the reactions of selenium species with oxidants, the reasons for the biological use of selenium versus sulfur and the potential use of low-molecular-mass selenium species as protective agents against oxidative damage. Here we review the kinetics and mechanisms of the reactions of oxidants produced during inflammation, with low-molecular-mass organoselenium compounds (e.g. selenoethers, diselenides and selenols). While selenium has some similar properties to sulfur, it typically exhibits greater reactivity with oxidants (e.g. hydrogen peroxide, radicals, singlet oxygen and hypochlorous, hypobromous, hypothiocyanous and peroxynitrous acids), and there are considerable differences in the subsequent reactivity and ease of repair of the resulting oxidation products. These data provide important insights for the development of therapeutic compounds.

Free radicals are produced during physiological processes including metabolism and the immune response, as well as on exposure to multiple external stimuli. Many radicals react rapidly with proteins resulting in side-chain modification, backbone fragmentation, aggregation, and changes in structure and function. Due to its low oxidation potential, the indole ring of tryptophan (Trp) is a major target, with this resulting in the formation of indolyl radicals (Trp•). These undergo multiple reactions including ring opening and dimerization which can result in protein aggregation. The factors that govern Trp• dimerization, the rate constants for these reactions and the exact nature of the products are not fully elucidated. In this study, second-order rate constants were determined for Trp• dimerization in Trp-containing peptides to be 2-6 × 108M-1s-1 by pulse radiolysis. Peptide charge and molecular mass correlated negatively with these rate constants. Exposure of Trp-containing peptides to steady-state radiolysis in the presence of NaN3 resulted in consumption of the parent peptide, and detection by LC-MS of up to 4 different isomeric Trp-Trp cross-links. Similar species were detected with other oxidants, including CO3•- (from the HCO3- -dependent peroxidase activity of bovine superoxide dismutase) and peroxynitrous acid (ONOOH) in the presence or absence of HCO3-. Trp-Trp species were also isolated and detected after alkaline hydrolysis of the oxidized peptides and proteins. These studies demonstrate that Trp• formed on peptides and proteins undergo rapid recombination reactions to form Trp-Trp cross-linked species. These products may serve as markers of radical-mediated protein damage, and represent an additional pathway to protein aggregation in cellular dysfunction and disease.

Activated white blood cells generate multiple oxidants in response to invading pathogens. Thus, hypochlorous acid (HOCl) is generated via the reaction of myeloperoxidase (from neutrophils and monocytes) with hydrogen peroxide, and peroxynitrous acid (ONOOH), a potent oxidizing and nitrating agent is formed from superoxide radicals and nitric oxide, generated by stimulated macrophages. Excessive or misplaced production of these oxidants has been linked to multiple human pathologies, including cardiovascular disease. Atherosclerosis is characterized by chronic inflammation and the presence of oxidized materials, including extracellular matrix (ECM) proteins, within the artery wall. Here we investigated the potential of selenium-containing indoles to afford protection against these oxidants, by determining rate constants (k) for their reaction, and quantifying the extent of damage on isolated ECM proteins and ECM generated by human coronary artery endothelial cells (HCAECs). The novel selenocompounds examined react with HOCl with k 0.2-1.0 × 108M-1s-1, and ONOOH with k 4.5-8.6 - × 105M-1s-1. Reaction with H2O2 is considerably slower (k < 0.25M-1s-1). The selenocompound 2-phenyl-3-(phenylselanyl)imidazo[1,2-a]pyridine provided protection to human serum albumin (HSA) against HOCl-mediated damage (as assessed by SDS-PAGE) and damage to isolated matrix proteins induced by ONOOH, with a concomitant decrease in the levels of the biomarker 3-nitrotyrosine. Structural damage and generation of 3-nitroTyr on HCAEC-ECM were also reduced. These data demonstrate that the novel selenium-containing compounds show high reactivity with oxidants and may modulate oxidative and nitrosative damage at sites of inflammation, contributing to a reduction in tissue dysfunction and atherogenesis.

Disulfide bonds, formed from two cysteine (Cys) residues, play a key role in defining and stabilizing protein structures. Whilst the reactions of Cys are well characterized, little is known about oxidation of disulfides, despite their high abundance in some proteins. Recent data indicate that some disulfides are rapidly oxidized by a range of oxidants, with rate constants, k, 105–107 M-1 s-1. Here we show that these reactions yield intermediates, potentially thiosulfinates [RSS(=O)R•], that can undergo further reaction, including disulfide bond cleavage and reaction with another thiol. Thus, oxidation of alpha-lactalbumin, which contains no free Cys residues, by HOCl or ONOOH gives long-lived reactive thiosulfinates that can react with GSH to give a glutathionylated protein, which can be detected by both anti-GSH antibodies and mass spectrometry. The thiosulfinate has a lifetime of many hours allowing glutathionylation to occur hours after initial oxidation. Disulfide oxidation can therefore give rise to long-lived oxidants on proteins that can undergo further reaction with thiols, including GSH and other proteins, to give mixed disulfides and protein dimers. These reactions may play a key role in GSH-dependent cell signaling and tissue damage.

In whole milk, riboflavin, lipids and proteins coexist. When exposed to light or other stressors, excited states of riboflavin (3RF) and lipid-derived peroxyl radicals are generated, which can induce oxidation and crosslinking of caseins, the major milk proteins. The nature of the crosslinks, and the involvement of di-tyrosine (diTyr) and di-tryptophan (diTrp) in these changes is unknown. In this study, we have examined changes in the structure and composition of α- and β- caseins elicited by 3RF and peroxyl radicals (ROO•) derived from thermolysis of AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride). SDS-PAGE, western blotting, fluorescence and UPLC methodologies were employed. Exposure of caseins to AAPH and 3RF resulted in extensive monomer consumption and high levels of protein cross-linking. Trp and Tyr residues were consumed, with the extent of formation of di-Tyr and diTrp dependent on the nature of the oxidant and presence of O2. With 3RF, diTyr and diTrp were primarily generated under an N2-atmosphere, with alternative pathways occurring in the presence of O2. In contrast, with ROO• low yields of diTyr and diTrp were detected, with alternative pathways likely to involve carbonyls and other oxidation products of Trp, Tyr and His mediating protein crosslinking.

Trp is a preferential target for radical reactions due to its low radical reduction potential, and these reactions result in the formation of indolyl radicals (Trp•). Trp• can then undergo reactions, including dimerisation and addition reactions with superoxide (O2•-). The addition of O2•- to Trp• is very rapid, with rate k 1–2 × 109 M-1s-1, and rates correlated with positive peptide charge. The primary product of the reaction are peroxides, and decay products including N-formylkynurenine and kynurenine detected. The dimerization reaction of Trp• has rates of k 2–6 × 108 M -1s-1. Dimerisation of Trp• yield novel dimer products of Trp, with four isomers detected. Oxidation of peptides and proteins by peroxynitrous acid or H2O2 in the presence of bovine superoxide dismutase and carbonate ions, yield Trp dimers that can be isolated through alkaline hydrolysis. These data explore the fates of Trp•, and based on the rate constants, the addition of O2•- should be the preferred pathway. Under conditions where O2•- is limited, Trp dimerization would be favored. The peroxidation and dimerization of Trp could play a major role protein degradation, playing a role in cellular dysfunction and disease.

Hypochlorous acid (HOCl) and N- chloramines are produced by myeloperoxidase (MPO) as part of the immune response to destroy invading pathogens. However, MPO also plays a detrimental role in inflammatory pathologies, including atherosclerosis, as inappropriate production of oxidants, including HOCl and N- chloramines, causes damage to host tissue. Low molecular mass thiol compounds, including glutathione (GSH) and methionine (Met), have demonstrated efficacy in scavenging MPO-derived oxidants, which prevents oxidative damage in vitro and ex vivo . Selenium species typically have greater reactivity toward oxidants compared to the analogous sulfur compounds, and are known to be efficient scavengers of HOCl and other hypohalous acids produced by MPO. In this study, we examined the efficacy of a number of sulfur and selenium compounds to scavenge a range of biologically relevant N -chloramines and oxidants produced by both isolated MPO and activated neutrophils and characterized the resulting selenium-derived oxidation products in each case. A dose-dependent decrease in the concentration of each N -chloramine was observed on addition of the sulfur compounds (cysteine, methionine) and selenium compounds (selenomethionine, methylselenocysteine, 1,4-anhydro-4-seleno- L- talitol, 1,5-anhydro-5-selenogulitol) studied. In general, selenomethionine was the most reactive with N -chloramines ( k 2 0.8–3.4×10 3 M –1 s –1 ) with 1,5-anhydro-5-selenogulitol and 1,4-anhydro-4-seleno- L- talitol ( k 2 1.1–6.8×10 2 M –1 s –1 ) showing lower reactivity. This resulted in the formation of the respective selenoxides as the primary oxidation products. The selenium compounds demonstrated greater ability to remove protein N -chloramines compared to the analogous sulfur compounds. These reactions may have implications for preventing cellular damage in vivo , particularly under chronic inflammatory conditions.

Oxidation, aggregation and accumulation of damaged proteins are key determinants of the shelf life and activity of protein-based medicines and foodstuffs, result in diminished agricultural yields, and are associated with multiple human diseases. Protein aggregation can occur both reversibly (via disulfides from Cys residues) and irreversibly via cross-linking of Tyr phenoxyl radicals. Recent studies have also provided evidence for dimerization of Trp radicals. This may be a major aggregation pathway due to the ease of oxidation (low reduction potential) of the indole ring of Trp. Hypothesis: that Trp radicals rapidly dimerize, generating cross-linked species. Results: Trp radicals generated by pulse radiolysis of free amino acid and peptides, at pH 7.4, undergo dimerization with k ~ 2 – 6 x 108 M-1s-1. These reactions are rapid compared to O 2 addition (k 2 O 2 /CO 3 2– system which generates CO 3 •– . Hydrolysis methods have been developed to allow detection and quantification of these species in complex systems. Conclusions: These studies demonstrate that indolyl radicals formed on Trp residues undergo rapid dimerization to give multiple cross-linked products. These reactions are a feasible mechanism for aggregation and degradation of proteins, and could contribute to protein dysfunction and the accumulation of damaged proteins in multiple diseases.