A Role for the Endothelial Glycocalyx in Regulating Microvascular Permeability in Diabetes Mellitus

Diabetic angiopathy is a major cause of morbidity and mortality in diabetes mellitus. Endothelial dysfunction and associated alterations in blood flow, pressure and permeability are widely accepted phenomena in the diabetic milieu and are understood to lead to microangiopathy. Despite the clinical importance of diabetic microangiopathy, the mechanisms of pathogenesis remain elusive. In particular, much is yet to be understood about the nature of the putative increased permeability with respect to diabetes. Microvessel permeability is intrinsically difficult to measure and a surrogate (solute or solvent flux) is usually reported, the measurement of which is hampered by haemodynamic factors, such as flow rate, hydrostatic pressure gradient, solute concentration and surface area available for exchange. Very few studies describing the measurement of permeability with respect to diabetes have controlled for all these factors. As a result, the nature of the increased microvessel permeability in diabetes mellitus and indeed its causes are poorly understood. Recent studies have shown that hyperglycaemia can alter the glycocalyx structure, and parallel findings have shown that the apparent increase in permeability demonstrated in hyperglycaemia may be due to an increase in the permeability of the vessels to water, and not an increase in protein permeability, an effect attributable to altered glycocalyx. This review focuses on the current understanding of microvascular permeability in terms of the endothelial glycocalyx-fibre-matrix theory, those methods used to determine permeability in the context of diabetes, and the more recent developments in our understanding of elevated microvascular permeability in the diabetic circulation.

High glucose increases angiopoietin-2 transcription in microvascular endothelial cells through methylglyoxal modification of mSin3A

Methylglyoxal is a highly reactive dicarbonyl degradation product formed from triose phosphates during glycolysis. Methylglyoxal forms stable adducts primarily with arginine residues of intracellular proteins. The biologic role of this covalent modification in regulating cell function is not known. Here we report that in mouse kidney endothelial cells, high glucose causes increased methylglyoxal modification of the corepressor mSin3A. Methylglyoxal modification of mSin3A results in increased recruitment of O-GlcNAc-transferase, with consequent increased modification of Sp3 by O-linked N-acetylglucosamine. This modification of Sp3 causes decreased binding to a glucose-responsive GC-box in the angiopoietin-2 (Ang-2) promoter, resulting in increased Ang-2 expression. Increased Ang-2 expression induced by high glucose increased expression of intracellular adhesion molecule 1 and vascular cell adhesion molecule 1 in cells and in kidneys from diabetic mice and sensitized microvascular endothelial cells to the proinflammatory effects of tumor necrosis factor alpha. This novel mechanism for regulating gene expression may play a role in the pathobiology of diabetic vascular disease.

Short-term low-dosage pioglitazone treatment improves vascular dysfunction in patients with type 2 diabetes

Endothelial dysfunction is an early marker of atherosclerosis. Pioglitazone is commonly used in the treatment of type 2 diabetes and has vascular protective effects beyond its hypoglycemic ones. We investigated the vascular effects of short-term, low-dosage pioglitazone in patients with type 2 diabetes. The study included 15 subjects with type 2 diabetes with normoalbuminuria (age, 60.7 +/- 11.9 years; body mass index [BMI], 23.9 +/- 3.3 kg/m2). The patients received pioglitazone at 15 mg daily for 4 weeks. BMI, systolic and diastolic blood pressure, laboratory parameters (fasting plasma glucose, insulin, lipid profile, high-sensitive C-reactive protein [hsCRP], and adiponectin) were assessed at baseline and after treatment. The forearm blood flow (FBF) was measured during reactive hyperemia by strain-gauge plethysmography. Short-term, low-dosage pioglitazone did not improve glycemic control or insulin sensitivity. However, the peak FBF and flow debt repayment (FDR) were markedly improved. There was no correlation of the improvement of peak FBF and FDR with the observed changes of metabolic parameters. However, the increment of adiponectin and decrement of hsCRP were well correlated with the improvement of peak FBF. These results indicate that short-term low-dosage pioglitazone may improve vascular function via increasing adiponectin expression and decreasing low-grade inflammation in type 2 diabetic patients.

Cardiac synchronous and dys-synchronous remodeling in diabetes mellitus

Glucose-mediated impairment of homocysteine (Hcy) metabolism and decrease in renal clearance contribute to hyperhomocysteinemia (HHcy) in diabetes. The Hcy induces oxidative stress, inversely relates to the expression of peroxisome proliferators activated receptor (PPAR), and contributes to diabetic complications. Extracellular matrix (ECM) functionally links the endothelium to the myocyte and is important for cardiac synchronization. However, in diabetes and hyperhomocysteinemia, a "disconnection" is caused by activated matrix metalloproteinase with subsequent accumulation of oxidized matrix (fibrosis) between the endothelium and myocyte (E-M). This contributes to "endothelial-myocyte uncoupling," attenuation of cardiac synchrony, leading to diastolic heart failure (DHF), and cardiac dys-synchronizatrion. The decreased levels of thioredoxin and peroxiredoxin and cardiac tissue inhibitor of metalloproteinase are in response to antagonizing PPARgamma.

Cyclohexenonic long-chain fatty alcohol has therapeutic effects on diabetes-induced angiopathy in the rat aorta

We studied the effects of cyclohexenonic long-chain fatty alcohol (N-hexacosanol) on diabetes-induced angiopathy in the rat aorta. Male Sprague-Dawley rats were divided into 4 groups, a control group and 3 other groups in which diabetes was induced by streptozotocin (50 mg/kg i.p.). Four weeks after the induction of diabetes, the 3 groups received treatment with either vehicle or N-hexacosanol (2 or 8 mg/kg, i.p. every day) for another 4 weeks. To determine the mechanisms of diabetic vascular dysfunction and the effects of N-hexacosanol, we conducted organ bath studies and real-time polymerase chain reaction on muscarinic M(3) receptor, and endothelial and inducible nitric oxide synthase (eNOS and iNOS) mRNAs in the rat aorta. Treatment with N-hexacosanol did not alter the diabetic status, but improved the diabetes-induced hypercontraction produced by norepinephrine and the damaged endothelium-dependent relaxation of the rat aorta induced by acetylcholine. Furthermore, in the diabetic rats, both muscarinic M(3) receptor and iNOS mRNAs were significantly increased, and N-hexacosanol reversed these upregulations. However, the expression of eNOS mRNA showed no change in all groups. These results indicate that N-hexacosanol has beneficial effects on functional dysfunction and reverses the upregulation of muscarinic M(3) receptor and iNOS mRNAs in the diabetic rat aorta.

Retinol binding protein-4 levels and clinical features of type 2 diabetes patients

CONTEXT

Retinol binding protein (RBP)-4 is a recently identified adipocytokine that is associated with insulin resistance.

OBJECTIVES

The aim was to investigate the association between RBP4 and various markers related to insulin resistance and diabetic complications in type 2 diabetic patients. The effect on RBP4 of the addition of pioglitazone to other diabetic medications was also examined. DESIGN, SETTING, PATIENTS, INTERVENTION, AND MAIN OUTCOME MEASURES: RBP4 levels were measured in 101 hospitalized patients with type 2 diabetes and in 22 nonhospitalized control subjects. Endothelial function was evaluated using flow-mediated vasodilatation. In a further 22 nonhospitalized type 2 diabetic patients, pioglitazone (30 mg/d) was administered for 12 wk while other medications for diabetes were continued.

RESULTS

There was a significant elevation of RBP4 levels in diabetic patients compared with healthy subjects. RBP4 showed significant positive correlations with triglyceride, systolic blood pressure, and log urinary albumin excretion, and significant negative correlations with high-density lipoprotein cholesterol and flow-mediated vasodilatation. In stepwise regression analysis, log urinary albumin excretion, triglyceride, and gender showed a significant association with RBP4. RBP4 was significantly elevated in patients with proliferative-diabetic retinopathy compared with nondiabetic retinopathy and simple-diabetic retinopathy patients. The addition of pioglitazone for 12 wk to other diabetic medications the patients were already taking did not affect the serum RBP4 concentration.

CONCLUSIONS

The current study shows that RBP4 is associated with variables related to insulin resistance and diabetic complications. The addition of pioglitazone for 12 wk to other diabetic medications the patients were already taking did not affect serum RBP4 levels.

Altered proximal aortic stiffness and endothelin plasma levels in diabetic patients with end-stage renal disease

Peripheral artery stiffness is altered in diabetic patients with end-stage renal disease (ESRD), whereas few data exist to confirm this trend for proximal aortic stiffness. The pulse wave velocity of the proximal aorta (PWVr) and of the carotid-to-femoral aortic segment (PWVcf) were determined by ultrasound imaging in 160 patients with ESRD (70 diabetic) and in 160 matched control subjects. Also, plasma levels of endothelin, homocysteine, and high-sensitivity C-reactive protein were determined in both groups. Patients with ESRD had increased pulse pressure, left ventricular (LV) end-diastolic diameter, LV mass index, PWVr, and PWVcf compared with control subjects (p < 0.05). Diabetic patients had increased LV mass index, PWVr, and PWVcf compared with nondiabetic patients with ESRD (p < 0.05). Endothelin levels exhibited a strong relation with PWVr (r = 0.32, p < 0.001) and PWVcf (r = 0.33, p < 0.001) measurements in ESRD patients. Multivariate linear regression analysis revealed that age, diabetes, and plasma levels of endothelin were major determinants of increased PWVr measurements in the total ESRD population. After adjustment for age, body surface area, time on dialysis, systolic blood pressure, history of hypertension, and plasma endothelin levels, diabetes was an independent factor associated with PWVr in ESRD subjects. Diabetic patients with ESRD had significantly increased proximal aortic stiffness and significantly altered plasma levels of endothelin as compared with the nondiabetic.

Angiotensin II and endothelin-1 augment the vascular complications of diabetes via JAK2 activation

The JAK/STAT pathway is activated in vitro by angiotensin II (ANG II) and endothelin-1 (ET-1), which are implicated in the development of diabetic complications. We hypothesized that ANG II and ET-1 activate the JAK/STAT pathway in vivo to participate in the development of diabetic vascular complications. Using male Sprague-Dawley rats, we performed a time course study [days 7, 14, and 28 after streptozotocin (STZ) injection] to determine changes in phosphorylation of JAK2, STAT1, and STAT3 in thoracic aorta using standard Western blot techniques. On day 7 there was no change in phosphorylation of JAK2, STAT1, and STAT3. Phosphorylation of JAK2, STAT1, and STAT3 was significantly increased on days 14 and 28 and was inhibited by treatment with candesartan (AT(1) receptor antagonist, 10 mg x kg(-1) x day(-1) orally in drinking water), atrasentan (ET(A) receptor antagonist, 10 mg x kg(-1) x day(-1) orally in drinking water), and AG-490 (JAK2 inhibitor, 5 mg x kg(-1) x day(-1) intraperitoneally). On day 28, treatment with all inhibitors prevented the significant increase in systolic blood pressure (SBP; tail cuff) of STZ-induced diabetic rats (SBP: 157 +/- 9.0, 130 +/- 3.3, 128 +/- 6.8, and 131 +/- 10.4 mmHg in STZ, STZ-candesartan, STZ-atrasentan, and STZ-AG-490 rats, respectively). In isolated tissue bath studies, diabetic rats displayed impaired endothelium-dependent relaxation in aorta (maximal relaxation: 95.3 +/- 3.0, 92.6 +/- 7.4, 76.9 +/- 12.1, and 38.3 +/- 13.1% in sham, sham + AG-490, STZ + AG-490, and STZ rats, respectively). Treatment of rats with AG-490 restored endothelium-dependent relaxation in aorta from diabetic rats at 14 and 28 days of treatment. These results demonstrate that JAK2 activation in vivo participates in the development of vascular complications associated with STZ-induced diabetes.

Endothelial dysfunction and arterial pressure regulation during early diabetes in mice: roles for nitric oxide and endothelium-derived hyperpolarizing factor

We determined whether nitric oxide (NO) counters the development of hypertension at the onset of diabetes in mice, whether this is dependent on endothelial NO synthase (eNOS), and whether non-NO endothelium-dependent vasodilator mechanisms are altered in diabetes in mice. Male mice were instrumented for chronic measurement of mean arterial pressure (MAP). In wild-type mice, MAP was greater after 5 wk of N(omega)-nitro-L-arginine methyl ester (L-NAME; 100 mg x kg(-1) x day(-1) in drinking water; 97 +/- 3 mmHg) than after vehicle treatment (88 +/- 3 mmHg). MAP was also elevated in eNOS null mice (113 +/- 4 mmHg). Seven days after streptozotocin treatment (200 mg/kg iv) MAP was further increased in L-NAME-treated mice (108 +/- 5 mmHg) but not in vehicle-treated mice (88 +/- 3 mmHg) nor eNOS null mice (104 +/- 3 mmHg). In wild-type mice, maximal vasorelaxation of mesenteric arteries to acetylcholine was not altered by chronic L-NAME or induction of diabetes but was reduced by 42 +/- 6% in L-NAME-treated diabetic mice. Furthermore, the relative roles of NO and endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced vasorelaxation were altered; the EDHF component was enhanced by L-NAME and blunted by diabetes. These data suggest that NO protects against the development of hypertension during early-stage diabetes in mice, even in the absence of eNOS. Furthermore, in mesenteric arteries, diabetes is associated with reduced EDHF function, with an apparent compensatory increase in NO function. Thus, prior inhibition of NOS results in endothelial dysfunction in early diabetes, since the diabetes-induced reduction in EDHF function cannot be compensated by increases in NO production.

Synergistic relationship between hyperglycaemia and inflammation with respect to clinical outcomes in non-ST-elevation acute coronary syndromes: analyses from OPUS-TIMI 16 and TACTICS-TIMI 18

AIMS

To investigate the relationship between diabetes and inflammation and the potentially synergistic relationship between hyperglycaemia and inflammation on clinical outcomes in non ST-elevation ACS.

METHODS AND RESULTS

The principal analysis was conducted in 2200 patients in OPUS-TIMI 16 with C-reactive protein data available and then validated in the invasive arm of TACTICS-TIMI 18 (n = 929). In addition, two further inflammatory markers [monocyte chemoattractant protein-1 (MCP-1) and von Willebrand factor (vWF)] were assessed in OPUS-TIMI 16. Diabetic patients had higher C-reactive protein and MCP-1 levels vs. non-diabetic patients in OPUS-TIMI 16 (9 vs. 7.8 mg/L, P = 0.002, and 190.6 vs. 170.8 pg/mL, P = 0.04, respectively), higher C-reactive protein levels in TACTICS-TIMI 18 (6.6 vs. 5.2 mg/L, P = 0.0005), and as expected higher glucose levels in both trials. Stratifying by the median C-reactive protein and diabetes in OPUS-TIMI 16, diabetic patients with C-reactive protein greater than or equal to the median were the highest risk group vs. non-diabetic patients with C-reactive protein less than the median (adjusted HR 1.63, 95% CI 1.20-2.23, P = 0.002). Directionally, similar findings were observed for MCP-1 and vWF in OPUS-TIMI 16 and for C-reactive protein in TACTICS-TIMI 18. After adjustment for diabetes, the risk associated with a 1 mmol/L increase in glucose was greater among those with a C-reactive protein greater than or equal to the median (HR 1.07, 95% CI 1.03-1.11) vs. those with a C-reactive protein less than the median (HR 1.02, 95% CI 0.97-1.06). After multivariable adjustment, the synergistic relationship between glucose and C-reactive protein and clinical outcomes remained statistically significant (P = 0.01). A similar pattern was observed in TACTICS-TIMI 18.

CONCLUSION

Among ACS patients, diabetes was associated with both greater inflammation and higher glucose levels and patients with both hyperglycaemia and inflammation had worse outcomes. Better control of both inflammation and hyperglycaemia should be assessed in future ACS trials as a means to reduce the cardiovascular risk among diabetics.

[Clinical and pathogenetic mechanisms of the formation of complicated course of I type diabetes mellitus in children]

The article presents the review of literature related to the analysis of current theories of the development of complicated I type diabetes mellitus in children. Special attention is given to the mechanisms of formation of late complications and in particular diabetic neuropathies. It is underlined, that the most important in pathogenesis of diabetic involvement of the nervous system is metabolic disorders, oxidizing stress, autoimmune processes. Microangiopathy plays certain role in formation of diabetic neuropathies, leading to disorders of microcirculation and hypoxia of nerves.

CD36 deficiency rescues lipotoxic cardiomyopathy

Obesity-related diabetes mellitus leads to increased myocardial uptake of fatty acids (FAs), resulting in a form of cardiac dysfunction referred to as lipotoxic cardiomyopathy. We have shown previously that chronic activation of the FA-activated nuclear receptor, peroxisome proliferator-activated receptor alpha (PPARalpha), is sufficient to drive the metabolic and functional abnormalities of the diabetic heart. Mice with cardiac-restricted overexpression of PPARalpha (myosin heavy chain [MHC]-PPARalpha) exhibit myocyte lipid accumulation and cardiac dysfunction. We sought to define the role of the long-chain FA transporter CD36 in the pathophysiology of lipotoxic forms of cardiomyopathy. MHC-PPARalpha mice were crossed with CD36-deficient mice (MHC-PPARalpha/CD36-/- mice). The absence of CD36 prevented myocyte triacylglyceride accumulation and cardiac dysfunction in the MHC-PPARalpha mice under basal conditions and following administration of high-fat diet. Surprisingly, the rescue of the MHC-PPARalpha phenotype by CD36 deficiency was associated with increased glucose uptake and oxidation rather than changes in FA utilization. As predicted by the metabolic changes, the activation of PPARalpha target genes involved in myocardial FA-oxidation pathways in the hearts of the MHC-PPARalpha mice was unchanged in the CD36-deficient background. However, PPARalpha-mediated suppression of genes involved in glucose uptake and oxidation was reversed in the MHC-PPARalpha/ CD36-/- mice. We conclude that CD36 is necessary for the development of lipotoxic cardiomyopathy in MHC-PPARalpha mice and that novel therapeutic strategies aimed at reducing CD36-mediated FA uptake show promise for the prevention or treatment of cardiac dysfunction related to obesity and diabetes.

Renal microvascular injury in diabetes: RAGE and redox signaling

Diabetic nephropathy remains a major cause of morbidity and mortality in the diabetic population and is the leading cause of end-stage renal failure in the Western World. Despite current therapeutics including intensified glycemic control and blood pressure lowering agents, renal disease continues to progress relentlessly in diabetic patients, albeit at a lower rate. It is well recognized that metabolic and hemodynamic factors play a central role in accelerating renal disease in diabetes. However, recent experimental studies have suggested that increased generation of reactive oxygen species (ROS) as a result of the diabetic milieu may play a central role in the progression of diabetic microvascular complications. These ROS appear to be generated primarily from mitochondrial sources and via the enzyme, NADPH oxidase. This review focuses on how ROS play a deleterious role in the diabetic kidney and how they are involved in crosstalk among various signaling pathways, ultimately leading to renal dysfunction and structural injury.

Apelin modulates aortic vascular tone via endothelial nitric oxide synthase phosphorylation pathway in diabetic mice

OBJECTIVE

The apelin receptor APJ is a putative receptor protein related to angiotensin (Ang) type 1 receptor. The apelin-APJ system has been implicated in diabetes, but its role in the diabetic vasculature and the mechanisms involved remain unclear. Our aim here was to explore the regulatory role of apelin in the aortic vascular tone in diabetic mice.

METHODS

A Multi Myograph system was used to determine the isometric vessel tone in aortic rings from diabetic db/db and control db/m+ mice. The mRNA, phosphorylation, and protein levels of APJ, Akt, and endothelial nitric oxide synthase (eNOS) were analyzed by reverse transcription-polymerase chain reaction and Western blotting, respectively.

RESULTS

There is depressed expression of APJ, enhanced contractile response to Ang II, and reduced relaxation response to acetylcholine in aortas from db/db mice. Apelin treatment strikingly reversed the altered aortic vascular responsiveness to Ang II and acetylcholine in db/db mice, both of which were abolished by the eNOS inhibitor NG-nitro-L-arginine methyl ester. Finally, in db/db mice, considerable increases in phosphorylation of Akt on serine 473 and of eNOS on serine 1177 were found in aortas pretreated with apelin.

CONCLUSIONS

Apelin treatment modulates the abnormal aortic vascular tone in response to Ang II and acetylcholine by potentiating phosphorylation of Akt and eNOS in diabetic mice, suggesting that the apelin-APJ system might be an important regulator of vascular function in diabetes.

Carnosine and its constituents inhibit glycation of low-density lipoproteins that promotes foam cell formation in vitro

Glycation of low-density lipoprotein (LDL) by reactive aldehydes, such as glycolaldehyde, can result in the cellular accumulation of cholesterol in macrophages. In this study, it is shown that carnosine, or its constituent amino acids beta-alanine and l-histidine, can inhibit the modification of LDL by glycolaldehyde when present at equimolar concentrations to the modifying agent. This protective effect was accompanied by inhibition of cholesterol and cholesteryl ester accumulation in human monocyte-derived macrophages incubated with the glycated LDL. Thus, carnosine and its constituent amino acids may have therapeutic potential in preventing diabetes-induced atherosclerosis.

Antioxidant status in type ii diabetes mellitus patients with or without microvascular complications

Introduction. Lipid peroxidation and antioxidant systems are important factors affecting the metabolism of lipoproteins in diabetes mellitus. Objective. The aim of this study was to investigate the lipid and antioxidant parameters in type II diabetes mellitus patients, and also to determine the effect of diabetic complications on these parameters. Method. Lipid status, Oxidized LDL cholesterol, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and plasminogen activator inhibitor (PAI-1) levels in plasma of 50 type II diabetic patients were measured with commercially available kits. Results. The results showed only statistically significant higher levels of triglycerides (3.12?3.9 mmol/l) in diabetics compared with the controls. Ox-LDL cholesterol (84.7?16.9 mmol/l) and SOD activities (913.4?120.3 U/gHb) in type 2 diabetes mellitus were higher than those of the controls, but there was no statistical significance. On the other hand, in patients with diabetes mellitus and complications, LDL cholesterol, PAI-1, SOD and GSH-Px activities were higher but not significantly than those without complications. Triglycerides and Ox-LDL cholesterol were lower in the group of diabetic patients with complications in comparison to the group without complications. Conclusion. These results indicate that antioxidant status may be affected in type II diabetic patients and that the rise in some enzyme activities could be a compensatory mechanism to prevent tissue damage. Our results suggest that the rise in PAI-1 in type II diabetics with complications may be a good marker of vascular endothelial dysfunction.

Progressive glycosylation of albumin and its effect on the binding of homocysteine may be a key step in the pathogenesis of vascular damage in diabetes mellitus

The majority of diabetes research to date has rightly focussed on the direct effects of hyperglycaemia on tissues and a number of theories relating to the pathogenesis of vascular disease have been proposed. This research is important as until methods are found to achieve glycaemic control in all diabetic patients, prophylactic interventions to prevent vasculopathy will be required. One of the major blood proteins, human albumin is known to be covalently modified by extended incubation with glucose, leading to an impairment of ligand binding. One of the important ligands bound by albumin is homocysteine. There is increasing and compelling clinical, experimental and epidemiological evidence that homocysteine, and in particular the free unbound fraction, is vasculotoxic. If homocysteine binding to albumin is impaired by increasing glycosylation of albumin then either drugs which reduce homocysteine levels (pyridoxine, folic acid and cobalamin) or inhibit glycosylation (aminoguanidines) may be of benefit in the prevention of vascular damage in diabetic patients.

Oxidative DNA damage and augmentation of poly(ADP-ribose) polymerase/nuclear factor-kappa B signaling in patients with Type 2 diabetes and microangiopathy

Although oxidative stress and the subsequent DNA damage is one of the obligatory signals for poly(ADP-ribose) polymerase (PARP) activation and nuclear factor-kappa B (NFkappaB) alterations, these molecular aspects have not been collectively examined in epidemiological and clinical settings. Therefore, this study attempts to assess the oxidative DNA damage and its downstream effector signals in peripheral blood lymphocytes from Type 2 diabetes subjects without and with microangiopathy along with age-matched non-diabetic subjects. The basal DNA damage, lipid peroxidation and protein carbonyl content were significantly (p<0.05) higher in patients with and without microangiopathy compared to control subjects. Formamido Pyrimidine Glycosylase (FPG)-sensitive DNA strand breaks which represents reliable indicator of oxidative DNA damage were also significantly (p<0.001) higher in diabetic patients with (19.41+/-2.5) and without microangiopathy (16.53+/-2.0) compared to control subjects (1.38+/-0.85). Oxidative DNA damage was significantly correlated to poor glycemic control. PARP mRNA expression and PARP activity were significantly (p<0.05) increased in cells from diabetic patients with (0.31+/-0.03 densitometry units; 0.22+/-0.02PARPunits/mgprotein, respectively) and without (0.35+/-0.02; 0.42+/-0.05) microangiopathy compared to control (0.19+/-0.02; 0.11+/-0.02) subjects. Diabetic subjects with and without microangiopathy exhibited a significantly (p<0.05) higher (80%) NFkappaB binding activity compared to control subjects. In diabetic patients, FPG-sensitive DNA strand breaks correlated positively with PARP gene expression, PARP activity and NFkappaB binding activity. This study provides a comprehensive molecular evidence for increased oxidative stress and genomic instability in Type 2 diabetic subjects even prior to vascular pathology and hence reveals a window of opportunity for early therapeutic intervention.

[Oxidative-antioxidative balance disturbance and risk factors as well as vascular complications in patients with diabetes type 2]

Hyperglycemia in patients with type 2 diabetes induces many pathological states, especially in disturbances cells' metabolism, like disorders of oxidative-antioxidative balance. The advantage of reactive oxygen species (ROS) over antioxidants is a cause of oxidative stress and creates an oxidative molecular damage of proteins, lipids, carbohydrates and nucleotides. It causes tissue degeneration, particularly in vascular system. The aim of our study was to evaluate the oxidative-antioxidative balance in patients with type 2 diabetes on the basis of selected parameters of the oxidative stress protein damage: thiol- (SH), carbonyl- (CO) and amino- (NH2) groups as well as advanced oxidation protein product (AOPP), as AOPP/albumin index as well as concentration of low molecular antioxidants (vitamin C, E, urinary acid, bilirubin). The total radical trapping antioxidant parameter (TRAP) was calculated also according to the mathematics formula. We have examined relationship between this parameters and duration of diabetes and vascular complications as well as risk factors like: hypertension, lipid disorders and obesity.

MATERIAL AND METHODS

Fifty-three patients with type 2 diabetes and 21 healthy persons were examined. The concentrations of SH and CO groups, AOPP as well as vitamin C were assessed colorimetrically, NH2 groups fluorimetrically and vitamin E by high-performance liquid chromatography (HPLC) method. The urinary acid and bilirubin were evaluated using routine clinical assays.

RESULTS

In patients with type 2 diabetes in comparison to healthy persons were affirmed: the significantly higher concentration of CO groups and AOPP as well as significantly lower concentration of SH groups; the lower concentration of vitamin C and TRAP value (statistically significant) and vitamin E (NS); the higher level of urinary acid (statistically significant) and bilirubin (NS).

CONCLUSIONS

The measurement of AOPP seems to be the best marker of oxidative stress in patients with type 2 diabetes, because significant increase of AOPP concentration was observed in patients with long-lasting diabetes (more then 10 years) with macroangiopathy, as well as in obese patients and ones with lipid disorders.

β1 antagonist and β2 agonist, celiprolol, restores the impaired endothelial dependent and independent responses and decreased TNFα in rat with type II diabetes

The effect of beta antagonists in the diabetic vascular lesion is controversial. We investigated the effect of celiprolol hydrochloride, a beta1 antagonist and mild beta2 agonist, on the lesions and function in type II male Otsuka Long-Evans Tokushima Fatty (OLETF) diabetic rats. OLETF rats were fed regular chow with or without atenolol (25 mg/kg/day) or celiprolol (100 mg/kg/day) treatment (group DM, no treatment; group DM-a, atenolol treatment; group DM-c, celiprolol treatment), and treatment was continued for 31 days. Separately, normoglycemic control rats, LETO, were prepared as group C. On day 3, endothelial cells of the right internal carotid artery were removed by balloon injury, and the rats were evaluated 4 weeks after balloon injury. The plasma glucose and lipid levels were unchanged throughout the treatment period. Intimal thickening was observed in the right carotid artery in the DM and DM-a groups; however, little thickening was observed in those of DM-c rats. Acetylcholine-induced NO-dependent relaxation in arteries was improved in DM-c rats compared with DM and DM-a rats (maximum relaxation DM 30.8+/-4.5, DM-a 37.4+/-3.9, DM-c 48.8+/-4.6%, *P<0.05 vs. DM for DM-c rats). Tone-related basal NO release and acetylcholine-induced NO-dependent relaxation in the arteries and plasma NO(x) (sum of NO(2)(-) and NO(3)(-)) were greater in DM-c and C groups than in DM and DM-a groups. The serum TNFalpha levels did not increase in DM-c rats compared with those of the DM or DM-a groups, and were comparable with those of group C.

CONCLUSION

In conclusion, Celiprolol improves endothelial function in the arteries of OLETF rats, and further restore it 4 weeks after endothelial denudation in the arteries of OLETF rats. NO and O(2)(-) may have a role in the important underlying mechanisms by reducing the TNFalpha levels.

[Proinsulin C-peptide -- the bioactive peptide with a huge promise]

Proinsulin connecting peptide (C-peptide) has been initially regarded as deprived of biological functions other than correct scaffolding of insulin. This was caused by the lack of evident effect of C-peptide administration to healthy subjects or animals. At present, in view of numerous studies concerning its structure, membrane binding and biological functions, C-peptide seems to constitute a crucial role in the pathogenesis of complications in diabetes mellitus type 1 (DM1). Patients who maintain high remnant insulin secretion (and therefore also of C-peptide) develop complications such as nephropathy, neuropathy and later microangiopathy with a milder clinical course. In this article we have covered molecular and cellular aspects of C-peptide functioning, such as: activation of protein kinase C, Na+,K+- ATP-ase, nitric oxide synthase, MAP and ERK 1/2 kinases, improvement of nerve conduction velocity and interactions with exogenous and endogenous insulin. We also outline the clinical consequences of deficiency of this underestimated peptide along with its potential therapeutical possibilities in the primary and secondary prevention of DM1 complications.

Protein kinase C beta inhibition: A novel therapeutic strategy for diabetic microangiopathy

Biochemical mechanisms involved in hyperglycaemia-induced vascular damage include alterations in cellular signalling by activation of protein kinase C (PKC). Twelve isoforms of PKC have been characterised according to their structure and co-factor requirements. Activation of PKC is mediated primarily through increased release of diacylglycerol (DAG). Adverse effects of PKC and DAG on vascular function include increased permeability, endothelial cell activation, altered blood flow, leukocyte adhesion and abnormal growth factor signalling. A highly selective and orally active PKC-beta isoform-selective inhibitor, ruboxistaurin, has been developed. Initial studies suggest that this agent decreased the development of sight-threatening macular oedema and the occurrence of visual loss. It did not, however, prevent the progression of diabetic retinopathy.

The molecular basis of diabetic microangiopathy

Diabetes mellitus is a chronic disease characterized by hyperglycaemia and carbohydrate, fat and protein metabolism abnormalities, all due to an impairment in insulin homeostasis and a diffuse microangiopathy most involving retina, kidney and nerves. Several mechanisms are altered at a molecular level and interplay to develop the slow but devastating clinical impairments related to microangiopathy. Polyol pathway, advanced glycation endproducts, protein kinase C, hexosamine pathway and oxidative stress are among those mechanisms. Molecular pathways of diabetes from hyperglycaemia to signalling cascades alterations and the most promising strategies for successful therapeutic approaches derived from better knowledge of biochemical mechanisms are treated extensively in the present review.