Increased plasma levels of thioredoxin in patients with glucose intolerance

Label-free quantitative proteomics analysis for type 2 diabetes mellitus early diagnostic marker discovery using data-independent acquisition mass spectrometry (DIA-MS)

Type-2 diabetes mellitus (T2DM) therapy requires early diagnosis and complication avoidance. Unfortunately, current diagnostic markers do not meet these needs. Data-independent acquisition mass spectrometry (DIA-MS) offers a solution for clinical diagnosis, providing reliable and precise sample quantification. This study utilized DIA-MS to investigate proteomic differential expression in the serum of recently diagnosed T2DM patients. The study conducted a comparative protein expression analysis between healthy and recently diagnosed T2DM groups (discovery cohort). A candidate protein was then validated using enzyme-linked immune assay (ELISA) on serum samples collected from T2DM patients (n = 87) and healthy control (n = 60) (validation cohort). A total of 1074 proteins were identified, and 90 were significantly dysregulated between the two groups, including 32 newly associated with T2DM. Among these proteins, the expression of S100 calcium-binding protein A6 (S100A6) was validated by ELISA. It showed a significant increase in T2DM samples compared to the control group. It was evaluated as a biomarker using the receiver operating characteristic (ROC) curve, consistent with the DIA-MS results. Novel proteins are reported to be involved in the development and progression of T2DM. Further studies are required to investigate the differential expression of candidate marker proteins in a larger population of T2DM patients.

Free Thiol β2-GPI (β-2-Glycoprotein-I) Provides a Link Between Inflammation and Oxidative Stress in Atherosclerotic Coronary Artery Disease

Objective:

Atherosclerotic coronary artery disease is well recognised as an inflammatory disorder that is also influenced by oxidative stress. β2-GPI (β-2-glycoprotein-I) is a circulating plasma protein that undergoes post-translational modification and exists in free thiol as well as oxidized forms. The aim of this study was to assess the association between these 2 post-translational redox forms of β2-GPI and atherosclerotic coronary artery disease.

Approach and Results:

Stable patients presenting for elective coronary angiography or CT coronary angiography were prospectively recruited. A separate group of patients after reperfused ST-segment–elevation myocardial infarction formed an acute coronary syndrome subgroup. All patients had collection of fasting serum and plasma for quantification of total and free thiol β2-GPI. Coronary artery disease extent was quantified by the Syntax and Gensini scores. A total of 552 patients with stable disease and 44 with acute coronary syndrome were recruited. While total β2-GPI was not associated with stable coronary artery disease, a higher free thiol β2-GPI was associated with its presence and extent. This finding remained significant after correcting for confounding variables, and free thiol β2-GPI was a better predictor of stable coronary artery disease than hs-CRP (high-sensitivity C-reactive protein). Paradoxically, there were lower levels of free thiol β2-GPI after ST-segment–elevation myocardial infarction.

Conclusions:

Free thiol β2-GPI is a predictor of coronary artery disease presence and extent in stable patients. Free thiol β2-GPI was a better predictor than high-sensitivity C-reactive protein.

The role of the thioredoxin/thioredoxin reductase system in the metabolic syndrome: towards a possible prognostic marker?

Mammalian thioredoxin reductase (TrxR) is a selenoprotein with three existing isoenzymes (TrxR1, TrxR2, and TrxR3), which is found primarily intracellularly but also in extracellular fluids. The main substrate thioredoxin (Trx) is similarly found (as Trx1 and Trx2) in various intracellular compartments, in blood plasma, and is the cell's major disulfide reductase. Thioredoxin reductase is necessary as a NADPH-dependent reducing agent in biochemical reactions involving Trx. Genetic and environmental factors like selenium status influence the activity of TrxR. Research shows that the Trx/TrxR system plays a significant role in the physiology of the adipose tissue, in carbohydrate metabolism, insulin production and sensitivity, blood pressure regulation, inflammation, chemotactic activity of macrophages, and atherogenesis. Based on recent research, it has been reported that the modulation of the Trx/TrxR system may be considered as a new target in the management of the metabolic syndrome, insulin resistance, and type 2 diabetes, as well as in the treatment of hypertension and atherosclerosis. In this review evidence about a possible role of this system as a marker of the metabolic syndrome is reported.

Anti-Inflammatory Thioredoxin Family Proteins for Medicare, Healthcare and Aging Care

Human thioredoxin (TRX) is a 12-kDa protein with redox-active dithiol in the active site -Cys-Gly-Pro-Cys-, which is induced by biological stress due to oxidative damage, metabolic dysfunction, chemicals, infection/inflammation, irradiation, or hypoxia/ischemia-reperfusion. Our research has demonstrated that exogenous TRX is effective in a wide variety of inflammatory diseases, including viral pneumonia, acute lung injury, gastric injury, and dermatitis, as well as in the prevention and amelioration of food allergies. Preclinical and clinical studies using recombinant TRX (rhTRX) are now underway. We have also identified substances that induce the expression of TRX in the body, in vegetables and other plant ingredients. Skincare products are being developed that take advantage of the anti-inflammatory and anti-allergic action of TRX. Furthermore, we are currently engaged in the highly efficient production of pure rhTRX in several plants, such as lettuce, grain and rice.

The role of lipid peroxidation in neurological disorders

There has been much evidence demonstrating the involvement of oxidative stress in the pathology of neurological disorders. Moreover, the vulnerability of the central nervous system to reactive oxygen species mediated injury is well established since neurons consume large amounts of oxygen, the brain has many areas containing high iron content, and neuronal mitochondria generate large amounts of hydrogen peroxide. Furthermore, neuronal membranes are rich in polyunsaturated fatty acids, which are particularly susceptible to oxidative stress. Recently, the biological roles of products produced by lipid peroxidation have received much attention, not only for their pathological mechanisms associated with neurological disorders, but also for their practical clinical applications as biomarkers. Here, we discuss the production mechanisms of reactive oxygen species in some neurological disorders, including Alzheimer's disease, Down syndrome, Parkinson's disease, and stroke. We also describe lipid peroxidation biomarkers for evaluating oxidative stress.

Plasma glutaredoxin activity in healthy subjects and patients with abnormal glucose levels or overt type 2 diabetes

Oxidative stress induced by hyperglycemia is a key factor in the pathogenesis of diabetes complications. Glutaredoxin 1(Grx1) is a cytosolic redox protein that catalyzes GSH-dependent thiol redox reactions and reversible protein S-glutathionylation. In humans, Grx1 antigen has previously been detected in plasma; however, it has hitherto been unclear if plasma Grx1 is enzymatically active, which would indicate an extracellular function of the protein. Given that glucose overload damages cells through oxidative stress responses, we investigated whether postprandial hyperglycemia induces changes in extracellular Grx1 in patients with abnormal glucose tolerance and healthy subjects. Using a novel sensitive fluorescent substrate assay, we demonstrated that plasma Grx consists of active protein. Grx antigen, activity and total antioxidant capacity were significantly elevated in patients compared to healthy subjects. In response to oral glucose tolerance test, Grx activity and antioxidant capacity increased significantly in healthy volunteers, however, not to the high levels of the patients. In conclusion, these results indicate an extracellular function of plasma Grx in blood glucose metabolism. Thus, Grx may be a marker of increased oxidative stress during hyperglycemia in healthy subjects and may be a risk marker of progression toward diabetes onset.

Decreased thioredoxin-1 and increased HSP90 expression in skeletal muscle in subjects with type 2 diabetes or impaired glucose tolerance

In diabetes, the endogenous defence systems are overwhelmed, causing various types of stress in tissues. In this study, newly diagnosed or diet-treated type 2 diabetics (T2D) (n = 10) were compared with subjects with impaired glucose tolerance (IGT) (n = 8). In both groups, at resting conditions, blood samples were drawn for assessing metabolic indices and skeletal muscle samples (m. vastus lateralis) were taken for the measurements of cellular defence markers: thioredoxin-1 (TRX-1) and stress proteins HSP72, HSP90. The protein level of TRX-1 was 36.1% lower (P = 0.031) and HSP90 was 380% higher (P < 0.001) in the T2D than in the IGT subjects, with no significant changes in HSP72. However, after the adjustment of both analyses with HOMA-IR only HSP90 difference remained significant. In conclusion, level of TRX-1 in skeletal muscle tissue was lower while that of HSP90 was higher in T2D than in IGT subjects. This may impair antioxidant defence and lead to disruptions of protein homoeostasis and redox regulation of cellular defences. Because HSP90 may be involved in sustaining functional insulin signalling pathway in type 2 diabetic muscles and higher HSP90 levels can be a consequence of type 2 diabetes, our results are potentially important for the diabetes research.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

Cardioprotective effect of selenium via modulation of cardiac ryanodine receptor calcium release channels in diabetic rat cardiomyocytes through thioredoxin system

Increased oxidative stress contributes to heart dysfunction via impaired Ca(2+) homeostasis in diabetes. Abnormal RyR2 function related with altered cellular redox state is an important factor in the pathogenesis of diabetic cardiomyopathy, while its underlying mechanisms remain poorly understood. In the present study, we used a streptozotocin-induced rat model of diabetic cardiomyopathy and tested a hypothesis that diabetes-related alteration in RyR2 function is related with ROS-induced posttranslational modifications. For this, we used heart preparations from either a diabetic rat or a sodium selenate (NaSe)-treated (0.3 mg/kg for 4 weeks) diabetic rat as well as either NaSe- (100 nmol/L) or thioredoxin (Trx; 5 μmol/L)-incubated (30 min) diabetic cardiomyocytes. Experimental approaches included imaging of intracellular free-Ca(2+) ([Ca(2+)]i) under both electrically stimulated and resting Fluo-3-loaded cardiomyocytes. RyR2-mediated SR-Ca(2+) leak was significantly enhanced in diabetic cardiomyocytes, resulting in reduced amplitude and prolonged time courses of [Ca(2+)]i transients compared to those of controls. Both SR-Ca(2+) leak and [Ca(2+)]i transients were normalized by treating diabetic rats with NaSe or by incubating diabetic myocytes with NaSe or Trx. Moreover, exposure of diabetic cardiomyocytes to antioxidants significantly improved [Ca(2+)]i handling factors such as phosphorylation/protein levels of RyR2, amount of RyR2-bound FKBP12.6 and activities of both protein kinase A and CaMKII. NaSe treatment also normalized the oxidative stress/antioxidant defense biomarkers in plasma as well as Trx activity and nuclear factor-κB phosphorylation in the diabetic rat heart. Collectively, these findings suggest that redox modification through Trx-system besides the glutathione system contributes to abnormal function of RyR2s in hyperglycemic cardiomyocytes, presenting a potential therapeutic target for treating diabetics to preserve cardiac function.

Thioredoxin interacting protein is a potential regulator of glucose and energy homeostasis in endogenous Cushing's syndrome

Recent studies have described bone as an endocrine organ regulating glucose metabolism, with insulin signaling regulating osteocalcin secretion and osteocalcin regulating β cell function. We have previously demonstrated increased bone expression of TXNIP in patients with endogenous Cushing's syndrome (CS), and we hypothesized that TXNIP could contribute to the dysregulated glucose metabolism in CS. We studied 33 CS patients and 29 matched controls, with bone biopsies from nine patients, before and after surgical treatment. In vitro, the effect of silencing TXNIP (siTXNIP) in osteoblasts, including its effect on human islet cells, was examined. Our major findings were: (i) The high mRNA levels of TXNIP in bone from CS patients were significantly associated with high levels of glucose and insulin, increased insulin resistance, and decreased insulin sensitivity in these patients. (ii) Silencing TXNIP in osteoblasts enhanced their OC response to insulin and glucose and down-regulated interleukin (IL)-8 levels in these cells. (iii) Conditional media from siTXNIP-treated osteoblasts promoted insulin content and anti-inflammatory responses in human islet cells. We recently demonstrated that the thioredoxin/TXNIP axis may mediate some detrimental effects of glucocorticoid excess on bone tissue in CS. Here we show that alterations in this axis also may affect glucose metabolism in these patients.

Singlet oxygen induced products of linoleates, 10- and 12-(Z,E)-hydroxyoctadecadienoic acids (HODE), can be potential biomarkers for early detection of type 2 diabetes

Current diagnostic tests such as glycemic indicators have limitations for early detection of impaired glucose tolerance (IGT), which leads to diabetes. Oxidative stress induced by various oxidants in a random and destructive manner is considered to play an important role in the pathophysiology of a number of human disorders and diseases such as impaired glucose tolerance. We have developed an improved method for the measurement of in vivo lipid peroxidation, where the presence of 8-iso-prostaglandin F_2α (8-iso-PGF_2α), hydroxyoctadecadienoic acids (HODEs), hydroxyeicosatetraenoic acids (HETEs), and 7-hydroxycholesterol (7-OHCh), as well as their parent molecules, linoleic acid (LA) and cholesterol (Ch), was determined by performing LC-MS/MS (for 8-iso-PGF_2α, HODE, and HETE) and GC-MS (for 7-OHCh, LA, and Ch) after reduction with triphenyl phosphine and saponification by potassium hydroxide. We then applied this method to volunteers (n = 57), including normal type (n = 43), “high-normal” (fasting plasma glucose, 100–109 mg/dL, n = 7), pre-diabetic type (IGT, n = 5), and diabetic type (n = 2) subjects who are diagnosed by performing oral glucose tolerance tests (OGTTs). Several biomarkers in plasma, such as insulin, leptin, adiponectin, interleukin-6, tumor necrosis factor-α, high sensitivity-C-reactive protein, HbA1c, and glucose levels were measured during OGTT. We found that the fasting levels of (10- and 12-(Z,E)- HODE)/LA increased significantly with increasing levels of HbA1c and glucose during OGTT and with insulin secretion and resistance index. In conclusion, 10- and 12-(Z,E)-HODE may be prominent biomarkers for the early detection of IGT and “high-normal” type without OGTT.

TXNIP is highly regulated in bone biopsies from patients with endogenous Cushing's syndrome and related to bone turnover

OBJECTIVE

Patients with endogenous Cushing's Syndrome (CS), as long-time treated patients with exogenous glucocorticoids (GCs), have severe systemic manifestations including secondary osteoporosis and low-energy fractures. The aim of the present study was to investigate the functional role of TXNIP in bone with focus on osteoblast (OB) differentiation and OB-mediated osteoclast activity and function in vitro.

DESIGN AND METHODS

Nine bone biopsies from CS before and after surgical treatment were screened for expressional candidate genes. Microarray analyses revealed that the gene encoding TXNIP ranked among the most upregulated genes. Subsequent in vitro and in vivo studies were performed.

RESULTS

We found that TXNIP gene in bone is downregulated in CS following surgical treatment. Furthermore, our in vivo data indicate novel associations between thioredoxin and TXNIP. Our in vitro studies showed that silencing TXNIP in OBs was followed by increased differentiation and expression and secretion of osteocalcin as well as enhanced activity of alkaline phosphatase. Moreover, treating osteoclasts with silenced TXNIP OB media showed an increased osteoclast activity.

CONCLUSIONS

TXNIP expression in bone is highly regulated during the treatment of active CS, and by GC in bone cells in vitro. Our data indicate that TXNIP may mediate some of the detrimental effects of GC on OB function as well as modulate OB-mediated osteoclastogenesis by regulating the OPG/RANKL ratio.

Reduction of glucose intolerance with high fat feeding is associated with anti-inflammatory effects of thioredoxin 1 overexpression in mice

Aging is associated with reduced ability to maintain normal glucose homeostasis. It has been suggested that an age-associated increase in chronic pro-inflammatory state could drive this reduction in glucoregulatory function. Thioredoxins (Trx) are oxido-reductase enzymes that play an important role in the regulation of oxidative stress and inflammation. In this study, we tested whether overexpression of Trx1 in mice [Tg(TRX1)^+/0] could protect from glucose metabolism dysfunction caused by high fat diet feeding. Body weight and fat mass gains with high fat feeding were similar in Tg(TRX1)^+/0 and wild-type mice; however, high fat diet induced glucose intolerance was reduced in Tg(TRX1)^+/0 mice relative to wild-type mice. In addition, expression of the pro-inflammatory cytokine TNF-α was reduced in adipose tissue of Tg(TRX1)^+/0 mice compared to wild-type mice. These findings suggest that activation of thioredoxins may be a potential therapeutic target for maintenance of glucose metabolism with obesity or aging.

Treatments with sodium selenate or doxycycline offset diabetes-induced perturbations of thioredoxin-1 levels and antioxidant capacity

Diabetes is associated with increased oxidative stress and impaired antioxidant defenses. Thioredoxin-1 (TRX-1) is a cytosolic thiol antioxidant and redox-active protein which plays a vital role in the maintenance of reduced intracellular redox state. In this study, the authors examined whether 4-week treatments with sodium selenate and doxycycline--a metalloproteinase-2 inhibitor which also has antioxidant-like effects--offset perturbations in oxidative stress and antioxidant protection in rat liver and skeletal muscle in streptozotocin-induced diabetes (SID) model. Experimental diabetes decreased TRX-1 levels in skeletal muscle and liver. On the other hand, SID increased oxidative stress marker protein carbonyl levels and decreased oxygen radical absorbance capacity (ORAC), an indicator of antioxidant capacity, in liver. A 4-week treatment of sodium selenate to diabetic rats decreased blood glucose levels moderately, while doxycycline treatment caused a reduction in weight loss of diabetic rats. Both doxycycline and sodium selenate prevented diabetes-induced decrease of TRX-1 levels in skeletal muscle, whereas only doxyxycline was effectively preventing diabetes-induced decrease of TRX-1 in liver. Furthermore, both treatments prevented diabetes-induced altered levels of protein carbonyls and ORAC in liver, and restored free and total protein thiol levels in both skeletal muscle and liver. In conclusion, the data of this study provides further evidence that sodium selenate and doxycycline treatments may control oxidative stress and improve antioxidant defense in diabetes.

Decreased serum levels of thioredoxin in patients with coronary artery disease plus hyperhomocysteinemia is strongly associated with the disease severity

OBJECTIVE

Elevation of homocysteine and thioredoxin (Trx) levels was found in some patients with coronary artery diseases (CAD). However, their correlations with CAD were not clear. Dysfunction of thioredoxin/thioredoxin reductase (TrxR) may cause oxidative stress that is common to CAD. We seek to determine the association among homocysteine, Trx/TrxR and CAD.

METHODS

Serum samples were collected from 150 CAD patients under statin treatment and 122 non-CAD controls. Risk factors for atherosclerosis including homocysteine, lipids and glucose levels were analyzed. Trx/TrxR activities and protein levels were determined using super-insulin assay and Western blot, respectively. One-way ANOVA, Tukey's post hoc test and Spearman's rank correlation coefficient were used for statistical analysis. CAD severity was evaluated by angiographic Gensini score.

RESULTS

Compared with non-CAD group, CAD group had significantly increased TrxR activity (P<0.05) and homocysteine levels (P<0.01), but not Trx activity. After further dividing CAD group using homocysteine below 15 microM as reference, Trx activity decreased significantly in CAD group with high homocysteine, and was inversely associated with homocysteine levels (r=-0.199, P<0.05) that was, however, weakly positively associated with TrxR activity. Neither lipids nor glucose significantly affected Trx/TrxR activity. Association of CAD severity with low Trx plus high homocysteine was strong (r=-0.458, P<0.001), but with high homocysteine alone was rather weak (r=0.125, P=0.225).

CONCLUSION

In CAD patients, high homocysteine levels may cause low Trx activity, which is closely correlated to the extent and severity of CAD.

Redox regulation of cell survival by the thioredoxin superfamily: an implication of redox gene therapy in the heart

Reactive oxygen species (ROS) are the key mediators of pathogenesis in cardiovascular diseases. Members of the thioredoxin superfamily take an active part in scavenging reactive oxygen species, thus playing an essential role in maintaining the intracellular redox status. The alteration in the expression levels of thioredoxin family members and related molecules constitute effective biomarkers in various diseases, including cardiovascular complications that involve oxidative stress. Thioredoxin, glutaredoxin, peroxiredoxin, and glutathione peroxidase, along with their isoforms, are involved in interaction with the members of metabolic and signaling pathways, thus making them attractive targets for clinical intervention. Studies with cells and transgenic animals have supported this notion and raised the hope for possible gene therapy as modern genetic medicine. Of all the molecules, thioredoxins, glutaredoxins, and peroxiredoxins are emphasized, because a growing body of evidence reveals their essential and regulatory role in several steps of redox regulation. In this review, we discuss some pertinent observations regarding their distribution, structure, functions, and interactions with the several survival- and death-signaling pathways, especially in the myocardium.

Thioredoxin in vascular biology: role in hypertension

The thioredoxin (TRX) system consists of TRX, TRX reductase, and NAD(P)H, and is able to reduce reactive oxygen species (ROS) through interactions with the redox-active center of TRX, which in turn can be reduced by TRX reductase in the presence of NAD(P)H. Among the TRX superfamily is peroxiredoxin (PRX), a family of non-heme peroxidases that catalyzes the reduction of hydroperoxides into water and alcohol. The TRX system is active in the vessel wall and functions either as an important endogenous antioxidant or interacts directly with signaling molecules to influence cell growth, apoptosis, and inflammation. Recent evidence implicates TRX in cardiovascular disease associated with oxidative stress, such as cardiac failure, arrhythmia, ischemia reperfusion injury, and hypertension. Thioredoxin activity is influenced by many mechanisms, including transcription, protein-protein interaction, and post-translational modification. Regulation of TRX in hypertensive models seems to be related to oxidative stress and is tissue- and cell-specific. Depending on the models of hypertension, TRX system could be upregulated or downregulated. The present review focuses on the role of TRX in vascular biology, describing its redox activities and biological properties in the media and endothelium of the vessel wall. In addition, the pathopysiological role of TRX in hypertension and other cardiovascular diseases is addressed.

Redox regulation in the extracellular environment

The oxidizing nature of the extracellular environment is vastly different from the highly reducing nature of the intracellular compartment. The redox potential of the cytosolic compartment of the intracellular environment limits disulfide bond formation, whereas the oxidizing extracellular environment contains proteins rich in disulfide bonds. If not for an extracellular antioxidant system to eliminate reactive oxygen and nitrogen species, lipid peroxidation and protein oxidation would become excessive, resulting in cellular damage. Many reviews have focused on the role of intracellular antioxidants in the elimination of oxidative stress, but this one will focus on the coordinated action of both intracellular and extracellular antioxidants in limiting cellular oxidant stress.

Thioredoxin and thioredoxin-binding protein-2 in cancer and metabolic syndrome

Thioredoxin (TRX), a small redox-active multifunctional protein, acts as a potent antioxidant and a redox regulator in signal transduction. TRX expression is elevated in various types of human cancer. Overexpression of TRX introduces resistance to anti-cancer drugs or radiation-induced apoptosis; however, there is no evidence that the incidence of cancer is frequent in TRX-transgenic mice or that the administration of recombinant human TRX enhances tumor growth. Plasma/serum level of TRX is a good marker for oxidative stress-induced various disorders, including metabolic syndrome. Thioredoxin-binding protein-2 (TBP-2), which was originally identified as a negative regulator of TRX, acts as a growth suppressor and a regulator in lipid metabolism. TBP-2 expression is downregulated in various types of human cancer. TBP-2 deficiency induces lipid dysfunction and a phenotype resembling Reye syndrome. Thus, TRX and TBP-2 play important roles in the pathophysiology of cancer and metabolic syndrome by direct interaction or by independent mechanisms.

Differential regulation of thioredoxin and NAD(P)H oxidase by angiotensin II in male and female mice

OBJECTIVE

We hypothesized that downregulation of the antioxidant thioredoxin system contributes to oxidative stress in angiotensin II-induced hypertension. As oestrogen may protect against oxidative stress, we also evaluated whether the thioredoxin system, particularly in the heart, is differentially regulated between females and males.

RESULTS

C57Bl/6 male and intact or ovariectomized female mice were infused with angiotensin II (400 ng/kg per minute for 2 weeks). Systolic blood pressure (SBP) was increased by angiotensin II in both groups week 1 and increased further in males versus females in week 2. Angiotensin II increased SBP from 112 +/- 6 to 143 +/- 9 mmHg in ovariectomized mice. Basal cardiac thioredoxin expression and reductase activity were significantly higher (two to threefold) in females versus males. Angiotensin II increased thioredoxin expression (approximately threefold), thioredoxin reductase activity, nicotinamide adenine dinucleotide phosphate, reduced form (NAD(P)H) oxidase activity and plasma thiobarbituric acid-reducing substances in males but not in females. Angiotensin II increased thioredoxin expression and NAD(P)H oxidase activity in ovariectomized versus control mice. Apurinic/apyrimidinic endonuclease/redox factor 1 (APE/Ref-1) activation, which interacts with thioredoxin to activate inflammatory transcription factors, was increased by angiotensin II only in males.

CONCLUSION

These results demonstrate sex dimorphism with respect to thioredoxin, oxidative stress and inflammation, and suggest the differential regulation of blood pressure, the cardiac thioredoxin system and NAD(P)H oxidase activity by angiotensin II in male and female mice. Whereas angiotensin II increases the activity of thioredoxin reductase and APE/Ref-1, enhances oxidative stress, and amplifies blood pressure elevation in males, it has little effect in females. Such differences may partly relate to the protective actions of oestrogens.

Medical treatment of diabetic retinopathy with somatostatin analogues

Traditional management strategies for retinal neovascularisation accompanying proliferative diabetic retinopathy include photocoagulation laser therapy. The development of preventative pharmacological treatments aimed at replacing or delaying this acute intervention has been an active research area and somatostatin analogues have shown promise in reducing the progression of retinal vascular pathologies. This review summarises the present knowledge on the molecular and cellular mechanisms of neovascularisation, and the rationale for the therapeutic use of somatostatin analogues as well as the results of two key recent clinical trials using octreotide. The potential use of octreotide and other somatostatin analogues in reducing the risk of severe visual impairment in proliferative diabetic retinopathy is discussed and pharmacological treatment regimens are proposed as an additional strategy or a less invasive alternative to laser therapy.

Clinical assessment of endothelial dysfunction: combine and rule

PURPOSE OF REVIEW

To briefly survey the literature for the past 2-3 years on the subject of diagnostic and prognostic markers of endothelial cell dysfunction.

RECENT FINDINGS

Established and emerging techniques to detect endothelial cell dysfunction are divided into two large families: (1) functional and structural markers of endothelial cell dysfunction, and (2) surrogate markers of endothelial cell dysfunction. The first category includes high-resolution Doppler studies of conduit arteries, laser Doppler flowmetry of cutaneous microvasculature, and measurements of arterial stiffness and intima: media thickness. The second category of tests provides brief descriptions of detection of oxidative stress, inflammation, coagulation abnormalities, circulating endothelial cells and microparticles. I also focus on integration of various techniques and some novel genomic, proteomic and metabolomic tests.

SUMMARY

This snapshot of existing and emerging technologies diagnosing endothelial cell dysfunction is intended to provide the foundation for the future (a) development of personalized noninvasive screening of endothelial function, and (b) delineation of preclinical diagnostic biomarkers heralding cardiovascular complications.