The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) plays a critical role in Ca2+ homeostasis via sequestration of this ion into the sarco/endoplasmic reticulum. The activity of this pump is inhibited by oxidants and impaired in ageing tissues and cardiovascular disease. We have shown previously that the myeloperoxidase- (MPO) derived oxidants HOCl and HOSCN target thiols and mediate cellular dysfunction. As SERCA contains Cys residues critical to ATPase activity, we hypothesized that HOCl and HOSCN might inhibit SERCA activity, via thiol oxidation, and increase cytosolic Ca2+ levels in human coronary artery endothelial cells (HCAEC). Exposure of sarcoplasmic reticulum vesicles to pre-formed or enzymatically-generated HOCl and HOSCN resulted in a concentration-dependent decrease in ATPase activity; this was also inhibited by the SERCA inhibitor thapsigargin. Decomposed HOSCN and incomplete MPO enzyme systems did not decrease activity. Loss of ATPase activity occurred concurrently with oxidation of SERCA Cys residues and protein modification. Exposure of HCAEC, with or without external Ca2+, to HOSCN or HOCl, resulted in a time- and concentration-dependent increase in intracellular Ca2+ under conditions that did not result in immediate loss of cell viability. Thapsigargin, but not inhibitors of plasma membrane or mitochondrial Ca2+ pumps/channels, completely attenuated the increase in intracellular Ca2+ consistent with a critical role for SERCA in maintaining endothelial cell Ca2+ homeostasis. Angiotensin II pre-treatment potentiated the effect of HOSCN at low concentrations. MPO-mediated modulation of intracellular Ca2+ levels may exacerbate endothelial dysfunction, a key early event in atherosclerosis, and be more marked in smokers due to their higher SCN− levels.
Myeloperoxidase; calcium; oxidation; thiols; sarco/endoplasmic reticulum Ca2+-ATPase (SERCA); hypochlorous acid; hypothiocyanous acid
Since crystallins in the human lens do not turnover, they are susceptible to modification by reactive molecules over time. Methylation is a major post-translational lens modification, however the source of the methyl group is not known and the extent of modification across all crystallins has yet to be determined. Sites of methylation in human lens proteins were determined using HPLC/mass spectrometry following digestion with trypsin. The overall extent of protein methylation increased with age, and there was little difference in the extent of modification between soluble and insoluble crystallins. Several different cysteine and histidine residues in crystallins from adult lenses were found to be methylated with one cysteine (Cys 110 in γD crystallin) at a level approaching 70%, however, methylation of crystallins was not detected in fetal or newborn lenses. S-adenosylmethionine (SAM) was quantified at significant (10–50 μM) levels in lenses, and in model experiments SAM reacted readily with N-α-tBoc-cysteine and N-α-tBoc-histidine, as well as βA3-crystallin. The pattern of lens protein methylation seen in the human lens was consistent with non-enzymatic alkylation. The in vitro data shows that SAM can act directly to methylate lens proteins and SAM was present in significant concentrations in human lens. Thus, non-enzymatic methylation of crystallins by SAM offers a possible explanation for this major human lens modification.
methylation; post-translational modification; age; lens protein
To compare the incidence of cardiovascular events and mortality in patients with type 2 diabetes mellitus treated with sitagliptin or non-sitagliptin comparators.
A post hoc assessment of cardiovascular safety in 14,611 patients was performed by pooling data from 25 double-blind studies, which randomised patients at baseline to sitagliptin 100 mg/day or a non-sitagliptin comparator (i.e., non-exposed). Included studies were limited to those at least 12 weeks in duration (range: 12 to 104 weeks). Patient-level data were used in this analysis of major adverse cardiovascular events (MACE) including ischaemic events and cardiovascular deaths. Analyses were performed in three cohorts: the entire 25-study cohort, the cohort from placebo-controlled portions of studies (n=19), and the cohort from studies comparing sitagliptin to a sulphonylurea (n=3).
In the entire cohort analysis, 78 patients had at least 1 reported MACE-related event, with 40 in the sitagliptin group and 38 in the non-exposed group. The exposure-adjusted incidence rate was 0.65 per 100 patient-years in the sitagliptin group and 0.74 in the non-exposed group (incidence rate ratio = 0.83 [95% confidence interval (CI): 0.53, 1.30]). In the analysis comparing sitagliptin to placebo, the exposure-adjusted incidence rate was 0.80 per 100-patient-years with sitagliptin and 0.76 with placebo (incidence rate ratio = 1.01 [95% CI: 0.55, 1.86]). In the analysis comparing sitagliptin to sulphonylurea, the exposure-adjusted incidence rate was 0.00 per 100 patient-years with sitagliptin and 0.86 with sulphonylurea (incidence rate ratio = 0.00 [95% CI: 0.00, 0.31]).
A pooled analysis of 25 randomised clinical trials does not indicate that treatment with sitagliptin increases cardiovascular risk in patients with type 2 diabetes mellitus. In a subanalysis, a higher rate of cardiovascular-related events was associated with sulphonylurea relative to sitagliptin.
Myeloperoxidase (MPO) forms reactive oxidants including hypochlorous and hypothiocyanous acids (HOCl and HOSCN) under inflammatory conditions. HOCl causes extensive tissue damage and plays a role in the progression of many inflammatory-based diseases. Although HOSCN is a major MPO oxidant, particularly in smokers, who have elevated plasma thiocyanate, the role of this oxidant in disease is poorly characterized. HOSCN induces cellular damage by targeting thiols. However, the specific targets and mechanisms involved in this process are not well defined. We show that exposure of macrophages to HOSCN results in the inactivation of intracellular enzymes, including creatine kinase (CK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In each case, the active-site thiol residue is particularly sensitive to oxidation, with evidence for reversible inactivation and the formation of sulfenyl thiocyanate and sulfenic acid intermediates, on treatment with HOSCN (less than fivefold molar excess). Experiments with DAz-2, a cell-permeable chemical trap for sulfenic acids, demonstrate that these intermediates are formed on many cellular proteins, including GAPDH and CK, in macrophages exposed to HOSCN. This is the first direct evidence for the formation of protein sulfenic acids in HOSCN-treated cells and highlights the potential of this oxidant to perturb redox signaling processes.
Myeloperoxidase; Hypothiocyanous acid; Sulfenic acid; Protein oxidation; Macrophage; Free radicals
To assess the efficacy and safety of MK-0941, a glucokinase activator (GKA), when added to stable-dose insulin glargine in patients with type 2 diabetes.
RESEARCH DESIGN AND METHODS
In this double-blind study, 587 patients taking stable-dose insulin glargine (±metformin ≥1,500 mg/day) were randomized (1:1:1:1:1) to MK-0941 10, 20, 30, or 40 mg or matching placebo t.i.d. before meals (a.c.). This study included an initial 14-week, dose-ranging phase followed by a 40-week treatment phase during which patients were to be uptitrated as tolerated to 40 mg (or placebo) t.i.d. a.c. The primary efficacy end point was change from baseline in A1C at Week 14.
At Week 14, A1C and 2-h postmeal glucose (PMG) improved significantly versus placebo with all MK-0941 doses. Maximal placebo-adjusted least squares mean changes from baseline in A1C (baseline A1C 9.0%) and 2-h PMG were −0.8% and −37 mg/dL (−2 mmol/L), respectively. No significant effects on fasting plasma glucose were observed at any dose versus placebo. By 30 weeks, the initial glycemic responses noted at 14 weeks were not sustained. MK-0941 at one or more doses was associated with significant increases in the incidence of hypoglycemia, triglycerides, systolic blood pressure, and proportion of patients meeting criteria for predefined limits of change for increased diastolic blood pressure.
In patients receiving stable-dose insulin glargine, the GKA MK-0941 led to improvements in glycemic control that were not sustained. MK-0941 was associated with an increased incidence of hypoglycemia and elevations in triglycerides and blood pressure.
In type 2 diabetes mellitus (T2DM), progressive loss of beta cell function over time requires treatment intensification and eventually initiation of insulin for many patients. Relative to metformin, a greater rate of decline in beta cell function over time has been observed with sulfonylurea treatment. The present study examined the association between initial monotherapy with metformin or sulfonylurea and subsequent initiation of insulin in older subjects with T2DM.
In a retrospective cohort study using the GE electronic medical record database, eligible subjects with T2DM included those ≥65 years who received their first prescription of sulfonylurea or metformin as initial monotherapy between January 1, 2003 to December 31, 2008. The follow-up period lasted to the end of 2009 or the subject’s latest data available. Insulin initiation was determined by prescription records. Logistic regression analysis evaluated the likelihood of insulin addition. A Cox regression model estimated time to initiation of insulin. Differences in baseline characteristics were controlled for using propensity score matching.
Overall, 12,036 subjects were included in the analysis. Mean age was 75 years and 50% were male. Subjects who initiated with sulfonylurea had a significantly (P < 0.001) higher incidence of insulin addition (2.8% vs. 1.4%) compared to those initiated with metformin within 1 year of follow-up. The likelihood of initiating insulin was higher in subjects initiated with sulfonylurea than with metformin (adjusted odds ratio 1.82, 95% confidence interval [CI] 1.40–2.38; P < 0.001). Sulfonylurea use was also significantly associated with a shorter time to insulin use compared to metformin (adjusted hazards ratio 2.10, 95% CI 1.83–2.39; P < 0.001).
In a cohort of older subjects with T2DM initiating antihyperglycemic therapy, new users of sulfonylurea monotherapy were more likely to receive insulin therapy and received it earlier than those starting with metformin.
Elderly; Insulin therapy; Metformin; Sulfonylurea; Type 2 diabetes
To identify reasons why primary care physicians (PCPs) do not treat older patients newly diagnosed with type 2 diabetes mellitus (T2DM) with antihyperglycemic agents following diagnosis.
US PCPs were surveyed via the internet regarding their reasons for not treating patients aged >65 years diagnosed with T2DM and had not yet initiated antihyperglycemic therapy for ≥6 months after diagnosis. PCPs were requested to provide relevant clinical information for untreated older patients and select applicable reasons for not initiating treatment from a list of 35 possibilities, grouped into five categories.
A total of 508 PCPs completed the online survey and provided complete clinical data for 770 patients. The reasons provided by the first-ranked physician for not initiating antihyperglycemic therapy were related to diet and exercise (57.5%); mild hyperglycemia (23.8%); patient’s concerns (13.4%); concerns about antihyperglycemic agents (3.0%); and comorbidities and polypharmacy (2.3%). The “diet and exercise” category was the most common first-ranked non-treatment reason, regardless of recent hemoglobin A1c (HbA1c) stratum. Reasons within the “patient’s concerns,” “concerns related to antihyperglycemic agents,” and “comorbidities and polypharmacy” categories tended to be selected more often as first-ranked reasons by physicians for patients with higher HbA1c values. Of the 158 patients whose physicians planned to initiate antihyperglycemic therapy within the next month, 54.4% already had a most recent HbA1c value above their physician-stated threshold for treatment initiation.
In the PCPs studied, there was a tendency to select appropriate reasons for non-treatment with antihyperglycemic agents given their patients’ glycemic status. However, there was inertia related to the initiation of pharmacological therapy in some older patients with newly diagnosed T2DM. Important factors included physicians’ perceptions of “mild” hyperglycemia and the HbA1c threshold for using antihyperglycemic agents.
Antihyperglycemic agents; Clinical inertia; Elderly; Non-treatment; Type 2 diabetes mellitus
To assess the factors associated with antihyperglycaemic medication initiation in UK patients with newly diagnosed type 2 diabetes.
In a retrospective cohort study, patients with newly diagnosed type 2 diabetes were identified during the index period of 2003-2005. Eligible patients were ≥ 30 years old at the date of the first observed diabetes diagnosis (referred to as index date) and had at least 2 years of follow-up medical history (N = 9,158). Initiation of antihyperglycaemic medication (i.e., treatment) was assessed in the 2-year period following the index date. Adjusted Cox regression models were used to examine the association between time to medication initiation and patient age and other factors.
Mean (SD) HbA1c at diagnosis was 8.1% (2.3). Overall, 51% of patients initiated antihyperglycaemic medication within 2 years (65%, 55%, 46% and 40% for patients in the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively). Among the treated patients, median (25th, 75th percentile) time to treatment initiation was 63 (8, 257) days. Of the patients with HbA1c ≥ 7.5% at diagnosis, 87% initiated treatment within 2 years. These patients with a higher HbA1c also had shorter time to treatment initiation (adjusted hazard ratio (HR) = 2.44 [95% confidence interval (CI): 1.61, 3.70]; p < 0.0001). Increasing age (in years) was negatively associated with time to treatment initiation (HR = 0.98 [95% CI: 0.97, 0.99]; p < 0.001). Factors significantly associated with shorter time to treatment initiation included female gender and use of cardiovascular medications at baseline or initiated during follow up.
In this UK cohort of patients with newly diagnosed type 2 diabetes, only 51% had antihyperglycaemic medication initiated over a 2-year period following diagnosis. Older patients were significantly less likely to have been prescribed antihyperglycaemic medications. Elevated HbA1c was the strongest factor associated with initiating antihyperglycaemic medication in these patients.
Clinical inertia; Age; Type 2 diabetes mellitus; Antihyperglycaemic medication
Elevated MPO (myeloperoxidase) levels are associated with multiple human inflammatory pathologies. MPO catalyses the oxidation of Cl−, Br− and SCN− by H2O2 to generate the powerful oxidants hypochlorous acid (HOCl), hypobromous acid (HOBr) and hypothiocyanous acid (HOSCN) respectively. These species are antibacterial agents, but misplaced or excessive production is implicated in tissue damage at sites of inflammation. Unlike HOCl and HOBr, which react with multiple targets, HOSCN targets cysteine residues with considerable selectivity. In the light of this reactivity, we hypothesized that Sec (selenocysteine) residues should also be rapidly oxidized by HOSCN, as selenium atoms are better nucleophiles than sulfur. Such oxidation might inactivate critical Sec-containing cellular protective enzymes such as GPx (glutathione peroxidase) and TrxR (thioredoxin reductase). Stopped-flow kinetic studies indicate that seleno-compounds react rapidly with HOSCN with rate constants, k, in the range 2.8×103–5.8×106 M−1·s−1 (for selenomethionine and selenocystamine respectively). These values are ~6000-fold higher than the corresponding values for H2O2, and are also considerably larger than for the reaction of HOSCN with thiols (16-fold for cysteine and 80-fold for selenocystamine). Enzyme studies indicate that GPx and TrxR, but not glutathione reductase, are inactivated by HOSCN in a concentration-dependent manner; k for GPx has been determined as ~5×105 M−1·s−1. Decomposed HOSCN did not induce inactivation. These data indicate that selenocysteine residues are oxidized rapidly by HOSCN, with this resulting in the inhibition of the critical intracellular Sec-dependent protective enzymes GPx and TrxR.
eosinophil peroxidase; glutathione peroxidase; hypothiocyanous acid (HOSCN); myeloperoxidase (MPO); selenium; thiocyanate; thioredoxin reductase; DTNB, 5,5′-dithiobis-(2-nitrobenzoic acid); DTT, dithiothreitol; Fmoc, fluoren-9-ylmethoxycarbonyl; GPx, glutathione peroxidase; GR, glutathione reductase; LPO, lactoperoxidase; MetSeO, methionine selenoxide; MPO, myeloperoxidase; RBC, red blood cell; Sec, selenocysteine; SeMet, selenomethionine; t-BOOH, t-butyl hydroperoxide; TNB, 5-thio-2-nitrobenzoic acid; TrxR, thioredoxin reductase; UPLC, ultra-performance liquid chromatography
Older patients with newly diagnosed type 2 diabetes mellitus are less likely to receive antihyperglycaemic therapy compared to their younger counterparts. The purpose of this study was to assess the reasons of general practitioners (GPs) for not treating younger and older patients with newly diagnosed type 2 diabetes mellitus with antihyperglycaemic agents.
In a survey conducted between November 2009 and January 2010, 358 GPs from the United Kingdom selected reasons for not initiating antihyperglycaemic therapy in younger (< 65 years) and older (≥65 years) patients with newly diagnosed type 2 diabetes mellitus and untreated with any antihyperglycaemic agent for at least six months following diagnosis. Thirty-six potential reasons were classified into four major categories: Mild hyperglycaemia, Factors related to antihyperglycaemic agents, Comorbidities and polypharmacy, and Patient-related reasons. Reasons for non-treatment were compared between younger (n = 1, 023) and older (n = 1, 005) patients.
Non-treatment reasons related to Mild hyperglycaemia were selected more often by GPs for both younger (88%) and older (86%) patients than those in other categories. For older patients, Factors related to antihyperglycaemic agents (46% vs. 38%) and Comorbidities and polypharmacy (33% vs. 19%), both including safety-related issues, were selected significantly (p < 0.001) more often by GPs. No between-group difference was observed for the Patient-related reasons category. The GP-reported HbA1c threshold for initiating antihyperglycaemic therapy was significantly (p < 0.001) lower for younger patients (mean ± standard deviation: 7.3% ± 0.7) compared to older patients (7.5% ± 0.9).
GPs selected reasons related to Mild hyperglycaemia for non-treatment of their untreated patients with newly diagnosed type 2 diabetes mellitus, despite nearly one-third of these patients having their most recent HbA1c value ≥7%. The findings further suggest that safety-related issues may influence the non-treatment of older patients with type 2 diabetes mellitus.
Polycystic ovary syndrome (PCOS) is a common female endocrine disorder of heterogeneous clinical presentation, high disease burden, and unknown aetiology. The disease and associated conditions cluster in families, suggesting that PCOS may be the reproductive consequence of underlying chronic disease susceptibility.
To determine whether parents of young women with PCOS were more likely to have a history of diabetes or cardiovascular disease in later adult life.
Design, Setting and Participants
Structured interviews with 715 members of a cohort constructed by tracing female infants born at a single general hospital in Adelaide between 1973 and 1975. Participants were asked whether they had a pre-existing medical diagnosis of PCOS, and whether each parent had ever had high blood pressure, high cholesterol, diabetes, stroke, or heart disease. Maternal high blood pressure during pregnancy was taken from the medical record of the pregnancy with the study participant.
Results and Conclusions
Mothers of women with PCOS were more likely than mothers of other women to have any cardiovascular disease (RR 1.78, 95% CI 1.29, 2.47), and nearly twice as likely to have high blood pressure (RR 1.95, 95% CI 1.38, 2.76). Fathers of women with PCOS were more than twice as likely to have heart disease (RR 2.36, 95% CI 1.44, 3.88) and over four times as likely to have had a stroke (RR 4.37, 95% CI 1.97, 9.70). Occurrence of cardiovascular disease in both mother and father are associated with the risk of PCOS in daughters. Further detailed study is required to elucidate the precise pathways that may be causally related to the observations.
During atherosclerosis monocyte-derived macrophages accumulate cholesteryl esters from low-density lipoproteins (LDLs) via lectin-like oxidised LDL receptor-1 (LOX-1) and class AI and AII (SR-AI, SR-AII) and class B (SR-BI, CD36) scavenger receptors. Here we examined the hypothesis that hyperglycaemia may modulate receptor expression and hence lipid accumulation in macrophages. Human monocytes were matured into macrophages in 30 versus 5 mM glucose and receptor expression and lipid accumulation quantified. High glucose elevated LOX1 mRNA, but decreased SR-AI, SR-BI, LDLR, and CD36 mRNA. SR-BI and CD36 protein levels were decreased. Normo- and hyperglycaemic cells accumulated cholesteryl esters from modified LDL to a greater extent than control LDL, but total and individual cholesteryl ester accumulation was not affected by glucose levels. It is concluded that, whilst macrophage scavenger receptor mRNA and protein levels can be modulated by high glucose, these are not key factors in lipid accumulation by human macrophages under the conditions examined.
Some oral antihyperglycemic agents may increase risk of hypoglycemia and thereby reduce patient quality of life. Our objective was to assess the impact of the severity and frequency of self-reported hypoglycemia on health-related quality of life (HRQoL) among patients with type 2 diabetes treated with oral antihyperglycemic agents.
A follow-up survey was conducted in participants with self-reported type 2 diabetes treated with oral antihyperglycemic agents from the US National Health and Wellness Survey 2007. Data were collected on the severity and frequency of hypoglycemic episodes in the 6 months prior to the survey, with severity defined as mild (no interruption of activities), moderate (some interruption of activities), severe (needed assistance of others), or very severe (needed medical attention). HRQoL was assessed using the EuroQol-5D Questionnaire (EQ-5D) US weighted summary score (utility) and Worry subscale of the Hypoglycemia Fear Survey (HFS). Of the participants who completed the survey (N = 1,984), mean age was 58 years, 57% were male, 72% reported an HbA1c <7.0%, and 50% reported treatment with a sulfonylurea-containing regimen. Hypoglycemic episodes were reported by 63% of patients (46% mild, 37% moderate, 13% severe and 4% very severe). For patients reporting hypoglycemia, mean utility score was significantly lower (0.78 versus 0.86, p < 0.0001) and mean HFS score was significantly higher (17.5 versus 6.2, p < 0.0001) compared to patients not reporting hypoglycemia. Differences in mean scores between those with and without hypoglycemia increased with the level of severity (mild, moderate, severe, very severe) for utility (0.03, 0.09, 0.18, 0.23) and HFS (6.1, 13.9, 20.1, 25.6), respectively. After adjusting for age, gender, weight gain, HbA1c, microvascular complications, and selected cardiovascular conditions, the utility decrement was 0.045 (by level of severity: 0.009, 0.055, 0.131, 0.208), and the HFS increase was 9.6 (by severity: 5.3, 12.4, 17.6, 23.2). HRQoL further decreased with greater frequency of hypoglycemic episodes.
Self-reported hypoglycemia is independently associated with lower HRQoL, and the magnitude of this reduction increases with both severity and frequency of episodes in patients with type 2 diabetes treated with oral antihyperglycemic agents.
Increased protein glycation in people with diabetes may promote atherosclerosis. This study examined the effects of non-enzymatic glycation on the association of lipid-free apolipoproteinA-I (apoA-I) with phospholipid, and cholesterol efflux from lipid-loaded macrophages to lipid-free and lipid-associated apoA-I. Glycation of lipid-free apoA-I by methylglyoxal and glycolaldehyde resulted in Arg, Lys and Trp loss, advanced glycation end-product formation and protein cross-linking. The association of apoA-I glycated by glucose, methylglyoxal or glycolaldehyde with phospholipid multilamellar vesicles was impaired in a glycating agent dose-dependent manner, with exposure of apoA-I to both 30 mM glucose (42% decrease in kslow) and 3 mM glycolaldehyde (50% decrease in kfast, 60% decrease in kslow) resulting is significantly reduced affinity. Cholesterol efflux to control or glycated lipid-free apoA-I, or discoidal reconstituted HDL containing glycated apoA-I (drHDL), was examined using cholesterol-loaded murine (J774A.1) macrophages treated to increase expression of ATP binding cassette transporters A1 (ABCA1) or G1 (ABCG1). Cholesterol efflux from J774A.1 macrophages to glycated lipid-free apoA-I via ABCA1 or glycated drHDL via an ABCG1-dependent mechanism was unaltered, as was efflux to minimally modified apoA-I from people with Type 1 diabetes, or controls. Changes to protein structure and function were prevented by the reactive carbonyl scavenger aminoguanidine. Overall these studies demonstrate that glycation of lipid-free apoA-I, particularly late glycation, modifies its structure, its capacity to bind phospholipids and but not ABCA1- or ABCG1-dependent cholesterol efflux from macrophages.
To investigate the effects of non-enzymatic glycation on the anti-inflammatory properties of apolipoprotein (apo) A-I.
Methods and Results
Rabbits were infused with saline, lipid-free apoA-I from normal subjects (apoA-IN), lipid-free apoA-I non-enzymatically glycated by incubation with methylglyoxal (apoA-IGlyc in vitro), non-enzymatically glycated lipid-free apoA-I from subjects with diabetes (apoA-IGlyc in vivo), discoidal reconstituted HDL containing phosphatidylcholine and apoA-IN, (A-IN)rHDL, or apoA-IGlyc in vitro, (A-IGlyc in vitro)rHDL. At 24 h post-infusion, acute vascular inflammation was induced by inserting a non-occlusive, periarterial carotid collar. The animals were sacrificed 24 h post-collar insertion. The collars caused intima/media neutrophil infiltration and increased endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). ApoA-IN infusion decreased neutrophil infiltration and VCAM-1 and ICAM-1 expression by 89, 90 and 66%, respectively. The apoA-IGlyc in vitro infusion decreased neutrophil infiltration by 53%, but did not reduce VCAM-1 or ICAM-1 expression. ApoA-IGlyc in vivo did not inhibit neutrophil infiltration or adhesion molecule expression. (A-IGlyc in vitro)rHDL also inhibited vascular inflammation less effectively than (A-IN)rHDL. The reduced anti-inflammatory properties of non-enzymatically glycated apoA-I were attributed to a reduced ability to inhibit nuclear factor-κB activation and reactive oxygen species formation.
Non-enzymatic glycation impairs the anti-inflammatory properties of apoA-I.
apoA-I; inflammation; HDL; adhesion molecules; neutrophils; NF-κB; reactive oxygen species
Background. Advanced glycation end-products (AGEs) and their receptors are prominent contributors to diabetic kidney disease. Methods. Flow cytometry was used to measure the predictive capacity for kidney impairment of the AGE receptors RAGE, AGE-R1, and AGE-R3 on peripheral blood mononuclear cells (PBMCs) in experimental models of type 2 diabetes (T2DM) fed varied AGE containing diets and in obese type 2 diabetic and control human subjects. Results. Diets high in AGE content fed to diabetic mice decreased cell surface RAGE on PBMCs and in type 2 diabetic patients with renal impairment (RI). All diabetic mice had elevated Albumin excretion rates (AERs), and high AGE fed dbdb mice had declining Glomerular filtration rate (GFR). Cell surface AGE-R1 expression was also decreased by high AGE diets and with diabetes in dbdb mice and in humans with RI. PBMC expression of AGE R3 was decreased in diabetic dbdb mice or with a low AGE diet. Conclusions. The most predictive PBMC profile for renal disease associated with T2DM was an increase in the cell surface expression of AGE-R1, in the context of a decrease in membranous RAGE expression in humans, which warrants further investigation as a biomarker for progressive DN in larger patient cohorts.
The potent oxidants hypochlorous acid (HOCl) and hypobromous acid (HOBr) are produced extracellularly by myeloperoxidase, following release of this enzyme from activated leukocytes. The subendothelial extracellular matrix is a key site for deposition of myeloperoxidase and damage by myeloperoxidase-derived oxidants, with this damage implicated in the impairment of vascular cell function during acute inflammatory responses and chronic inflammatory diseases such as atherosclerosis. The heparan sulfate proteoglycan perlecan, a key component of the subendothelial extracellular matrix, regulates important cellular processes and is a potential target for HOCl and HOBr. It is shown here that perlecan binds myeloperoxidase via its heparan sulfate side chains and that this enhances oxidative damage by myeloperoxidase-derived HOCl and HOBr. This damage involved selective degradation of the perlecan protein core without detectable alteration of its heparan sulfate side chains, despite the presence of reactive GlcNH2 resides within this glycosaminoglycan. Modification of the protein core by HOCl and HOBr (measured by loss of immunological recognition of native protein epitopes and the appearance of oxidatively-modified protein epitopes) was associated with an impairment of its ability to support endothelial cell adhesion, with this observed at a pathologically-achievable oxidant dose of 425 nmol oxidant/mg protein. In contrast, the heparan sulfate chains of HOCl/HOBr-modified perlecan retained their ability to bind FGF-2 and collagen V and were able to promote FGF-2-dependent cellular proliferation. Collectively, these data highlight the potential role of perlecan oxidation, and consequent deregulation of cell function, in vascular injuries by myeloperoxidase-derived HOCl and HOBr.
oxidation; heparan sulfate; perlecan; myeloperoxidase; inflammation
There is considerable interest in the role that mammalian heme peroxidase enzymes, primarily myeloperoxidase, eosinophil peroxidase and lactoperoxidase, may play in a wide range of human pathologies. This has been sparked by rapid developments in our understanding of the basic biochemistry of these enzymes, a greater understanding of the basic chemistry and biochemistry of the oxidants formed by these species, the development of biomarkers that can be used damage induced by these oxidants in vivo, and the recent identification of a number of compounds that show promise as inhibitors of these enzymes. Such compounds offer the possibility of modulating damage in a number of human pathologies. This reviews recent developments in our understanding of the biochemistry of myeloperoxidase, the oxidants that this enzyme generates, and the use of inhibitors to inhibit such damage.
myeloperoxidase; hypochlorous acid; chloramines; protein oxidation; neutrophil
Background and Aims
The resurgence of malaria, particularly in the developing world, is considerable and exacerbated by the development of single-gene multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by the World Health Organization, now include the use of antimalarial compounds derived from Artemisia annua – in particular, the use of artemisinin-based ingredients. Despite our limited knowledge of its mode of action or biosynthesis there is a need to secure a supply and enhance yields of artemisinin. The present study aims to determine how plant biomass can be enhanced while maximizing artemisinin concentration by understanding the plant's nutritional requirements for nitrogen and potassium.
Experiments were carried out, the first with differing concentrations of nitrogen, at 6, 31, 56, 106, 206 or 306 mg L−1 being applied, while the other differing in potassium concentration (51, 153 or 301 mg L−1). Nutrients were supplied in irrigation water to plants in pots and after a growth period biomass production and leaf artemisinin concentration were measured. These data were used to determine optimal nutrient requirements for artemisinin yield.
Nitrogen nutrition enhanced plant nitrogen concentration and biomass production successively up to 106 mg N L−1 for biomass and 206 mg N L−1 for leaf nitrogen; further increases in nitrogen had no influence. Artemisinin concentration in dried leaf material, measured by HPLC mass spectroscopy, was maximal at a nitrogen application of 106 mg L−1, but declined at higher concentrations. Increasing potassium application from 51 to 153 mg L−1 increased total plant biomass, but not at higher applications. Potassium application enhanced leaf potassium concentration, but there was no effect on leaf artemisinin concentration or leaf artemisinin yield.
Artemisinin concentration declined beyond an optimal point with increasing plant nitrogen concentration. Maximization of artemisinin yield (amount per plant) requires optimization of plant biomass via control of nitrogen nutrition.
Artemisia; fertigation; malaria; nitrogen; nutrition; potassium
MPO (myeloperoxidase) catalyses the oxidation of chloride, bromide and thiocyanate by hydrogen peroxide to HOCl (hypochlorous acid), HOBr (hypobromous acid) and HOSCN (hypothiocyanous acid) respectively. Specificity constants indicate that SCN− is a major substrate for MPO. HOSCN is also a major oxidant generated by other peroxidases including salivary, gastric and eosinophil peroxidases. While HOCl and HOBr are powerful oxidizing agents, HOSCN is a less reactive, but more specific, oxidant which targets thiols and especially low pKa species. In the present study we show that HOSCN targets cysteine residues present in PTPs (protein tyrosine phosphatases) with this resulting in a loss of PTP activity for the isolated enzyme, in cell lysates and intact J774A.1 macrophage-like cells. Inhibition also occurs with MPO-generated HOCl and HOBr, but is more marked with MPO-generated HOSCN, particularly at longer incubation times. This inhibition is reversed by dithiothreitol, particularly at early time points, consistent with the reversible oxidation of the active site cysteine residue to give either a cysteine–SCN adduct or a sulfenic acid. Inhibition of PTP activity is associated with increased phosphorylation of p38a and ERK2 (extracellular-signal-regulated kinase 2) as detected by Western blot analysis and phosphoprotein arrays, and results in altered MAPK (mitogen-activated protein kinase) signalling. These data indicate that the highly selective targeting of some protein thiols by HOSCN can result in perturbation of cellular phosphorylation and altered cell signalling. These changes occur with (patho)physiological concentrations of SCN− ions, and implicate HOSCN as an important mediator of inflammation-induced oxidative damage, particularly in smokers who have elevated plasma levels of SCN−.
cell signalling; hypothiocyanous acid (HOSCN); mitogen-activated protein kinase (MAPK); myeloperoxidase; p38; protein tyrosine phosphatase; thiol; DTT, dithiothreitol; ECL, enhanced chemiluminescence; ERK, extracellular-signal-regulated kinase; HOBr, hypobromous acid; HOCl, hypochlorous acid; HOSCN, hypothiocyanous acid; HRP, horseradish peroxidase; LPO, lactoperoxidase; MAPK, mitogen-activated protein kinase; MKK, MAPK kinase; MPO, myeloperoxidase; PTP, protein tyrosine phosphatase
The heparan sulfate (HS) proteoglycan perlecan is a major component of basement membranes, plays a key role in extracellular matrix (ECM) structure, interacts with growth factors and adhesion molecules, and regulates the adhesion, differentiation and proliferation of vascular cells. Atherosclerosis is characterized by chronic inflammation and the presence of oxidized materials within lesions, with the majority of protein damage present on ECM, rather than cell, proteins. Weakening of ECM structure plays a key role in lesion rupture, the major cause of heart attacks and strokes. In this study peroxynitrite, a putative lesion oxidant, is shown to damage perlecan structurally and functionally. Exposure of human perlecan to peroxynitrite decreases recognition by antibodies raised against both the core protein and heparan sulfate chains; dose-dependent formation of 3-nitrotyrosine was also detected. These effects were modulated by bicarbonate and reaction pH. Oxidant exposure resulted in aggregate formation, consistent with oxidative protein crosslinking. Peroxynitrite treatment modified functional properties of perlecan that are dependent on both the protein core (decreased binding of human coronary artery endothelial cells), and the HS chains (diminished fibroblast growth factor-2 (FGF-2) receptor-mediated proliferation of Baf-32 cells). The latter is consistent with a decrease in FGF-2 binding to the HS chains of modified perlecan. Immunofluorescence of advanced human atherosclerotic lesions provided evidence for the presence of perlecan and extensive formation of 3-nitrotyrosine epitopes within the intimal region; these materials showing marked co-localization. These data indicate that peroxynitrite induces major structural and functional changes to perlecan and that damage to this material occurs within human atherosclerotic lesions.
ABTS, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid); dONOO, decomposed peroxynitrite; ECM, extracellular matrix; FGF-2, fibroblast growth factor 2; HCAEC, human coronary artery endothelial cells; HS, heparan sulfate; HSPG, heparan sulfate proteoglycan; MTT, 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan; 3-nitroTyr, 3-nitrotyrosine; ONOO-, peroxynitrous acid anion; ONOOH, peroxynitrous acid; TCA, trichloroacetic acid; Atherosclerosis; Extracellular matrix; Perlecan; Peroxynitrite; Heparan sulfate proteoglycans; Plaque rupture; Cell adhesion; Cell proliferation; Inflammation
While menarche indicates the beginning of a woman's reproductive life, relatively little is known about the association between age at menarche and subsequent morbidity and mortality. We aimed to examine the effect of lower age at menarche on all-cause mortality in older Australian women over 15 years of follow-up.
Data were drawn from the Australian Longitudinal Study of Ageing (n = 1,031 women aged 65-103 years). We estimated the hazard ratio (HR) associated with lower age at menarche using Cox proportional hazards models, and adjusted for a broad range of reproductive, demographic, health and lifestyle covariates.
During the follow-up period, 673 women (65%) died (average 7.3 years (SD 4.1) of follow-up for decedents). Women with menses onset < 12 years of age (10.7%; n = 106) had an increased hazard of death over the follow-up period (adjusted HR 1.28; 95%CI 0.99-1.65) compared with women who began menstruating aged ≥ 12 years (89.3%; n = 883). However, when age at menarche was considered as a continuous variable, the adjusted HRs associated with the linear and quadratic terms for age at menarche were not statistically significant at a 5% level of significance (linear HR 0.76; 95%CI 0.56 - 1.04; quadratic HR 1.01; 95%CI 1.00-1.02).
Women with lower age at menarche may have reduced survival into old age. These results lend support to the known associations between earlier menarche and risk of metabolic disease in early adulthood. Strategies to minimise earlier menarche, such as promoting healthy weights and minimising family dysfunction during childhood, may also have positive longer-term effects on survival in later life.
Sitagliptin, a highly selective dipeptidyl peptidase-4 inhibitor, is the first in a new class of oral antihyperglycemic agents (AHAs) for the treatment of patients with type 2 diabetes. Type 2 diabetes is a life-long disease requiring chronic treatment and management. Therefore, robust assessment of the long-term safety and tolerability of newer therapeutic agents is of importance. The purpose of this analysis was to assess the safety and tolerability of sitagliptin by pooling 12 large, double-blind, Phase IIb and III studies up to 2 years in duration. Methods: This analysis included 6139 patients with type 2 diabetes receiving either sitagliptin 100 mg/day (N = 3415) or a comparator agent (placebo or an active comparator) (N = 2724; non-exposed group). The 12 studies from which this pooled population was drawn represent the double-blind, randomized, Phase IIB and III studies that included patients treated with the clinical dose of sitagliptin (100 mg/day) for at least 18 weeks up to 2 years and that were available in a single safety database as of November 2007. These 12 studies assessed sitagliptin as monotherapy, initial combination therapy with metformin, or add-on combination therapy with other oral AHAs (metformin, pioglitazone, sulfonylurea, sulfonylurea + metformin, or metformin + rosiglitazone). Patients in the non-exposed group were taking placebo, pioglitazone, metformin, sulfonylurea, sulfonylurea + metformin, or metformin + rosiglitazone. This safety analysis used patient-level data from each study to evaluate clinical and laboratory adverse experiences.
For clinical adverse experiences, the incidence rates of adverse experiences overall, serious adverse experiences, and discontinuations due to adverse experiences were similar in the sitagliptin and non-exposed groups. The incidence rates of specific adverse experiences were also generally similar in the two groups, with the exception of an increased incidence rate of hypoglycemia observed in the non-exposed group. The incidence rates of drug-related adverse experiences overall and discontinuations due to drug-related adverse experiences were higher in the non-exposed group, primarily due to the increased incidence rate of hypoglycemia in this group. For cardiac- and ischemia-related adverse experiences (including serious events), there were no meaningful between-group differences. No meaningful differences between groups in laboratory adverse experiences, either summary measures or specific adverse experiences, were observed.
In patients with type 2 diabetes, sitagliptin 100 mg/day was well tolerated in clinical trials up to 2 years in duration.
The oocyst wall of apicomplexan parasites protects them from the harsh external environment, preserving their survival prior to transmission to the next host. If oocyst wall formation could be disrupted, then logically, the cycle of disease transmission could be stopped, and strategies to control infection by several organisms of medical and veterinary importance such as Eimeria, Plasmodium, Toxoplasma, Cyclospora, and Neospora could be developed. Here, we show that two tyrosine-rich precursor glycoproteins, gam56 and gam82, found in specialized organelles (wall-forming bodies) in the sexual stage (macrogamete) of Eimeria maxima are proteolytically processed into smaller glycoproteins, which are then incorporated into the developing oocyst wall. The identification of high concentrations of dityrosine and 3,4-dihydroxyphenylalanine (DOPA) in oocyst extracts by high-pressure liquid chromatography, together with the detection of a UV autofluorescence in intact oocysts, implicates dityrosine- and possibly DOPA-protein cross-links in oocyst wall hardening. In addition, the identification of peroxidase activity in the wall-forming bodies of macrogametes supports the hypothesis that dityrosine- and DOPA-mediated cross-linking might be an enzyme-catalyzed event. As such, the mechanism of oocyst wall formation in Eimeria, is analogous to the underlying mechanisms involved in the stabilization of extracellular matrices in a number of organisms, widely distributed in nature, including insect resilin, nematode cuticles, yeast cell walls, mussel byssal threads, and sea urchin fertilization membranes.