Microvascular complications of impaired glucose tolerance

Lipid and inflammatory markers for the prediction of coronary artery disease: A multi-marker approach

BACKGROUND

Many studies have investigated the clinical accuracy of single lipid and inflammatory markers. In contrast, few have evaluated their potential for the detection of CAD using a multi-marker approach.

METHODS

The concentrations of lipid, lipoproteins, apolipoproteins, high sensitivity C-reactive protein (hs-CRP) and fibrinogen were measured by standard laboratory methods. Apolipoprotein (a) [apo(a)] phenotyping was performed by sodium dodecylsulphate-gel electrophoresis and immunoblotting. The lipid tetrad index (LTI) and the lipid pentad index (LPI) were calculated. Clinical accuracy of the examined parameters, indexes and a logistic regression model was assessed using receiving operative characteristic (ROC) curve analysis.

RESULTS

Logistic regression analysis indicated that non-HDL-c, hs-CRP, HDL-c and Lp(a) were significant independent predictors for CAD. The AUC for this model (0.802) was higher than AUCs for any single marker or index tested.

CONCLUSIONS

We conclude that the performance of a logistic regression model for CAD prediction warrants its use in clinical practice.

Predicting glucose intolerance with normal fasting plasma glucose by the components of the metabolic syndrome

BACKGROUND

Surprisingly, it is estimated that about half of type 2 diabetics remain undetected. The possible causes may be partly attributable to people with normal fasting plasma glucose (FPG) but abnormal postprandial hyperglycemia. We attempted to develop an effective predictive model by using the metabolic syndrome (MeS) components as parameters to identify such persons.

SUBJECTS AND METHODS

All participants received a standard 75-g oral glucose tolerance test, which showed that 106 had normal glucose tolerance, 61 had impaired glucose tolerance, and 6 had diabetes-on-isolated postchallenge hyperglycemia. We tested five models, which included various MeS components. Model 0: FPG; Model 1 (clinical history model): family history (FH), FPG, age and sex; Model 2 (MeS model): Model 1 plus triglycerides, high-density lipoprotein cholesterol, body mass index, systolic blood pressure and diastolic blood pressure; Model 3: Model 2 plus fasting plasma insulin (FPI); Model 4: Model 3 plus homeostasis model assessment of insulin resistance. A receiver-operating characteristic (ROC) curve was used to determine the predictive discrimination of these models.

RESULTS

The area under the ROC curve of the Model 0 was significantly larger than the area under the diagonal reference line. All the other 4 models had a larger area under the ROC curve than Model 0. Considering the simplicity and lower cost of Model 2, it would be the best model to use. Nevertheless, Model 3 had the largest area under the ROC curve.

CONCLUSION

We demonstrated that Model 2 and 3 have a significantly better predictive discrimination to identify persons with normal FPG at high risk for glucose intolerance.

Alterations in liver sinusoidal endothelium in a baboon model of type 1 diabetes

AIMS/HYPOTHESIS

Diabetes mellitus is associated with extensive vascular pathology, yet little is known about its long-term effects on liver sinusoidal endothelial cells (LSECs). Potential diabetic changes in LSECs are important because of the role played by fenestrations in the LSECs in hepatic disposition of lipoproteins.

MATERIALS AND METHODS

Surgical liver biopsies for electron microscopy and immunohistochemistry were obtained from baboons with long-standing streptozotocin-induced, insulin-treated diabetes mellitus and compared with those from age-matched control animals.

RESULTS

There was an increase in the thickness of LSECs (170 +/- 17 vs 123 +/- 10 nm, p < 0.01). Fenestrations in LSECs, as determined by overall porosity, were markedly reduced (1.4 +/- 0.1% vs 2.6 +/- 0.2%, p < 0.01). Increased numbers of stellate cells were seen on electron microscopy, and this finding was corroborated by increased smooth muscle actin expression. Diabetes mellitus was also associated with increased endothelial production of von Willebrand factor and caveolin-1.

CONCLUSIONS/INTERPRETATION

Diabetes mellitus in the non-human primate is associated with marked changes in LSECs, including a reduction in fenestrations. Such changes provide an additional and novel mechanism for impaired hepatic lipoprotein clearance and post-prandial hyperlipidaemia in diabetes mellitus.

The dynamics of glucose metabolism under calcineurin inhibitors in the first year after renal transplantation in nonobese patients

BACKGROUND

The incidence of glucose metabolism disturbances after transplantation often is based on the use of hypoglycemic agents and not on the results of glucose tolerance tests (GTTs), which may camouflage the real incidence. A lack of information also exists regarding the profile of glucose metabolism during the first year after transplant.

METHODS

Oral GTT along with insulin measurements and drugs pharmacokinetics were prospectively performed at days 30, 60, 180, and 360 after transplant to diagnose disturbances of glucose metabolism after renal transplantation, in nonobese patients receiving either tacrolimus (n=55) or cyclosporine (n=29), along with mycophenolate mofetil and steroids.

RESULTS

The incidence of impaired glucose tolerance or diabetes mellitus reached a peak at 60 days and decreased at 1 year. It could not be adequately diagnosed using fasting plasma glucose in a decreased abnormal (>99 ng/mL) range. In both groups, insulin secretion, evaluated by the Homeostasis Model Assesment (HoMA-beta), decreased (P<0.005) from the condition of normal GTT (101+/-56%) to impaired glucose tolerance (72+/-35%) and diabetes mellitus (54+/-25%). In the cyclosporine group, insulin secretion was normal and stable throughout the study period, but in the tacrolimus group, insulin secretion recovered over time and was inversely correlated with tacrolimus exposure. Insulin resistance (HoMA-IR) did not change.

CONCLUSIONS

This study shows the need to perform an oral GTT at 60 days and at the end of the first year of renal transplantation to adequately diagnose impaired glucose metabolism.

Adiponectin deficiency increases leukocyte-endothelium interactions via upregulation of endothelial cell adhesion molecules in vivo

This study reports on what we believe are novel mechanism(s) of the vascular protective action of adiponectin. We used intravital microscopy to measure leukocyte-endothelium interactions in adiponectin-deficient (Ad(-/-)) mice and found that adiponectin deficiency was associated with a 2-fold increase in leukocyte rolling and a 5-fold increase in leukocyte adhesion in the microcirculation. Measurement of endothelial NO (eNO) revealed that adiponectin deficiency drastically reduced levels of eNO in the vascular wall. Immunohistochemistry demonstrated increased expression of E-selectin and VCAM-1 in the vascular endothelium of Ad(-/-) mice. Systemic administration of the recombinant globular adiponectin domain (gAd) to Ad(-/-) mice significantly attenuated leukocyte-endothelium interactions and adhesion molecule expression in addition to restoring physiologic levels of eNO. Importantly, prior administration of gAd also protected WT mice against TNF-alpha-induced leukocyte-endothelium interactions, indicating a pharmacologic action of gAd. Mechanistically, blockade of eNOS with N(omega)-nitro-L-arginine methyl ester ( L-NAME) abolished the inhibitory effect of gAd on leukocyte adhesion, demonstrating the obligatory role of eNOS signaling in the antiinflammatory action of gAd. We believe this is the first demonstration that gAd protects the vasculature in vivo via increased NO bioavailability with suppression of leukocyte-endothelium interactions. Overall, we provide evidence that loss of adiponectin induces a primary state of endothelial dysfunction with increased leukocyte-endothelium adhesiveness.

A population-based study of coeliac disease, neurodegenerative and neuroinflammatory diseases

BACKGROUND

It has been suggested that coeliac disease (CD) is associated with several neurological diseases. However, the evidence of such an association is inconclusive as earlier research has often been based on small numbers with retrospective data collection.

AIM

To use Cox regression to examine the risk of neurological disease in individuals with CD.

METHODS

Through Swedish national registers we identified some 14 000 individuals with a diagnosis of CD (1964-2003) and 70 000 reference individuals matched for age, sex, calendar year and county.

RESULTS

Coeliac disease was associated with later polyneuropathy [hazard ratio (HR) = 3.4; 95% CI = 2.3-5.1]. We found no statistically significant association between CD and subsequent multiple sclerosis (HR = 0.9; 95% CI = 0.3-2.3), Parkinson's disease (HR = 1.2; 95% CI = 0.8-1.9), Alzheimer's disease (HR = 1.5; 95% CI = 0.9-2.6), hereditary ataxia (HR = 1.3; 95% CI = 0.5-3.6), the symptom ataxia (HR = 1.9; 95% CI = 0.6-6.2), Huntington's disease (HR = 1.7; 95% CI = 0.3-8.6), myasthenia gravis (HR = 0.8; 95% CI = 0.2-3.8) or spinal muscular atrophy (HR = 0.5; 95% CI = 0.1-3.8). Prior polyneuropathy was associated with subsequent CD (odds ratio = 5.4; 95% CI = 3.6-8.2).

CONCLUSIONS

The association between CD and polyneuropathy indicates shared risks. We suggest that individuals with polyneuropathy routinely undergo screening for CD. There is no notable association between CD and other neurological outcomes investigated in this study.

Impaired glucose tolerance: A possible contributor to left ventricular hypertrophy and diastolic dysfunction

BACKGROUND

Approximately 40% of patients with heart failure have preserved left ventricular systolic function with latent diastolic dysfunction associated with left ventricular hypertrophy, suggesting that diastolic dysfunction participates in the pathophysiology of heart failure. However, the cause or prerequisite status of diastolic dysfunction has not been resolved. This study was designed to investigate whether impaired glucose tolerance is related to left ventricular hypertrophy and abnormal diastolic function.

METHODS

An age/sex-matched study was performed in subjects who underwent health screening, including both a 75-g oral glucose tolerance test and Doppler echocardiography. Using the WHO criteria, the subjects were classified into the diabetic group (n=112, 77 men/35 women, mean aged: 57.3+/-7.6 years), the impaired glucose tolerance group (n=226, 155 men/71 women, mean aged 56.8+/-7.5 years), and the normal glucose tolerance group (n=639, 438 men/201 women, mean aged 56.7+/-7.5 years). The subjects had no symptoms or signs of chronic heart failure.

RESULTS

There were no significant differences of ejection fraction, fractional shortening, and left ventricular dimensions among the three groups. However left ventricular mass was larger in the impaired glucose tolerance and the diabetic groups compared with the normal group, while the mitral E/A wave ratio was lower in the impaired glucose tolerance and the diabetic groups compared with the normal group even after adjustment for the values of blood pressure and body mass index and left ventricular mass.

CONCLUSIONS

These results suggest that impaired glucose tolerance is a possible contributor to left ventricular hypertrophy and diastolic dysfunction.

Effects of flavonoids on the expression of the pro-inflammatory response in human monocytes induced by ligation of the receptor for AGEs

Increasing evidence has shown advanced glycation end products (AGEs) receptor ligation (RAGE) to be an important part of complex interactions of the oxidative stress and pro-inflammatory responses. In this study, flavonoids were used to monitor the protective effects against the oxidative damage and inflammation mediated by AGEs in human monocytes. S100B (RAGE ligand) treatment in human THP-1 monocytic cells (THP-1) significantly increased gene expression of the pro-inflammatory cytokines TNF-alpha and IL-1beta; chemokines MCP-1 and IP-10; adhesion factors platelet endothelial cell adhesion molecule (PECAM-1) and beta2-integrin; and pro-inflammatory cyclooxygenase-2 (COX-2). S100B treatment with quercetin and catechin in THP-1 cells had inhibitory effects on the expression of pro-inflammatory genes and protein levels. Quercetin and catechin could regulate S100B-activated oxidant stress-sensitive pathways through blocking p47phox protein expression. Treatment with quercetin and catechin could eliminate reactive oxygen species (ROS) to reduce oxidative stress stimulated by S100B in THP-1 cells. Quercetin and catechin also showed different regulatory abilities on mitogen-activated protein kinase (MAPK) signaling pathways by inhibiting protein expression in S100B-stimulated inflammatory responses in THP-1 cells. This study suggests that quercetin and catechin may be of benefit for diabetic vascular complications due to its antioxidant abilities against AGE-mediated oxidative stress through oxidative stress-sensitive and oxidative stress-responsive signaling pathways, which lead to inflammation in human monocytes.

Prevalence-dependent decision limits for the early detection of type 2 diabetes mellitus in venous blood, venous plasma and capillary blood during glucose challenge

BACKGROUND

The glycemia decision limits recommended by WHO/ADA for type 2 diabetes detection are derived from clinical signs in advanced stages of the disease. Since insulin secretion patterns and sensitivitity are impaired at the beginning of type 2 diabetes, this stage may be better suited to identify decision limits with higher diagnostic efficiency than those currently applied.

METHODS

Oral glucose tolerance tests were performed in 300 subjects. Glucose concentrations were measured at 30-min intervals in venous plasma, venous blood and capillary blood. Insulin concentrations in venous plasma, an insulin sensitivity index and body mass index were used to indicate a type 2 diabetic state. A multiple logistic regression procedure was "trained" using only subjects "clearly" considered to be non-diseased or diseased based on an oral glucose tolerance test according to WHO criteria. This insulin algorithm was applied to the whole study group, leading to definitive classification into the non-diseased or the diseased group. This a posteriori classification was used to identify cutoff values with the highest diagnostic efficiency.

RESULTS

The diagnostic efficiency was significantly higher when decision limits lower than the WHO recommendations for glucose concentrations were applied in a preselected subpopulation and in all three sample systems tested, e.g., 9.49 mmol/L (171 mg/dL) for venous plasma and 8.94 mmol/L (161 mg/dL) for capillary blood in the 2-h post-load state. The optimized and WHO 2-h cutoff values corresponded to a disease prevalence of 28% and approximately 5% (20% in the fasting state), respectively. Diagnostic efficiency was higher in the 2-h post-load than in the fasting state. Combining fasting values with 2-h post-load values did not further improve the diagnostic efficiency. Glucose concentrations determined from capillary blood were as efficient as those from venous blood or plasma. The number of diabetic subjects detected differed considerably between capillary blood and venous plasma for the WHO/ADA cutoff values, but not for the optimized cutoff values.

CONCLUSIONS

The efficiency of type 2 diabetes diagnosis can be improved by optimizing cutoff values according to disease prevalence. Unexpectedly, the optimized 2-h post-load cutoff was lower for capillary blood than for venous plasma. It is proposed to identify a risk group e.g., by characteristics of the metabolic syndrome in which the 2-h post-challenge concentration is determined using lower cut-off values than presently recommended.

Oxidative burden in prediabetic and diabetic individuals: evidence from plasma coenzyme Q(10)

AIM

Individuals with diabetes and prediabetes are at risk of vascular injury. However, the exact mechanisms are unclear. The mitochondria mobile electron carrier coenzyme Q(10) (CoQ(10)) is a potent lipophilic antioxidant. We hypothesize that oxidative stress, detectable as changes in plasma CoQ(10) concentrations and composition, plays an important role in vascular disease in diabetes.

METHODS

We measured plasma CoQ(10) concentrations (including reduced ubiquinol and oxidized ubiquinone subfractions) in 60 subjects with normal glucose tolerance [NGT; fasting plasma glucose (FPG) < 5.5 mmol/l], 63 with impaired fasting glucose (IFG; FPG 5.6-6.9 mmol/l) and 69 with Type 2 diabetes (DM; FPG > 6.9 mmol/l).

RESULTS

In men and women, the total CoQ(10)/total cholesterol ratio was reduced in DM (mean +/-sd) [male (M) 0.09 +/- 0.04; female (F) 0.07 +/- 0.04] compared with NGT (0.29 +/- 0.08; 0.21 +/- 0.07) and IFG (0.27 +/- 0.07; 0.23 +/- 0.07) (DM vs. NGT and IFG P = 0.001). A stepwise reduction in the plasma ubiquinol fraction (ubiquinol/total CoQ10) was observed from NGT (M 0.93 +/- 0.06; F 0.95 +/- 0.06) compared with IFG (0.43 +/- 0.25; 0.41 +/- 0.15) and DM (0.24 +/- 0.11; F 0.29 +/- 0.16) (DM vs. IFG vs. NGT P = 0.001). In contrast, the plasma ubiquinone/ubiquinol ratio increased from NGT (M 0.08 +/- 0.07, F 0.06 +/- 0.08) to IFG (2.14 +/- 1.84, 1.75 +/- 1.04) to DM (4.77 +/- 4.88, 3.81 +/- 3.71) (DM vs. IFG vs. NGT P = 0.001). These differences remained after adjusting for age, body mass index and FPG.

CONCLUSIONS

The change in CoQ(10) with increasing FPG concentration suggests an increase in oxidative burden, already evident in the prediabetic IFG individuals. This increase in oxidative stress might contribute to the increased risk of vascular disease.

Endothelial Progenitor Cell Release into Circulation Is Triggered by Hyperoxia-Induced Increases in Bone Marrow Nitric Oxide

Endothelial progenitor cells (EPC) are known to contribute to wound healing, but the physiologic triggers for their mobilization are often insufficient to induce complete wound healing in the presence of severe ischemia. EPC trafficking is known to be regulated by hypoxic gradients and induced by vascular endothelial growth factor-mediated increases in bone marrow nitric oxide (NO). Hyperbaric oxygen (HBO) enhances wound healing, although the mechanisms for its therapeutic effects are incompletely understood. It is known that HBO increases nitric oxide levels in perivascular tissues via stimulation of nitric oxide synthase (NOS). Here we show that HBO increases bone marrow NO in vivo thereby increasing release of EPC into circulation. These effects are inhibited by pretreatment with the NOS inhibitor l-nitroarginine methyl ester (l-NAME). HBO-mediated mobilization of EPC is associated with increased lower limb spontaneous circulatory recovery after femoral ligation and enhanced closure of ischemic wounds, and these effects on limb perfusion and wound healing are also inhibited by l-NAME pretreatment. These data show that EPC mobilization into circulation is triggered by hyperoxia through induction of bone marrow NO with resulting enhancement in ischemic limb perfusion and wound healing.

Recent clinical advances in diabetic polyneuropathy

PURPOSE OF REVIEW

Recent dramatic increases in the incidence and prevalence of diabetes make an understanding of chronic symmetric sensorimotor diabetic polyneuropathy, the most common and problematic of chronic diabetic complications, essential for a wide range of medical practitioners.

RECENT FINDINGS

The demonstration of neuropathic dysfunction in patients with prediabetes or impaired glucose tolerance emphasizes the susceptibility of peripheral nerve fibers, especially small A delta fibers and C fibers, to relatively mild, short-duration hyperglycemia. New testing can reveal peripheral nerve dysfunction prior to clinical neuropathic symptoms and signs. In the absence of effective medications to halt or reverse nerve damage or promote nerve regeneration, early diagnosis of diabetic polyneuropathy, followed by tight glycemic control with diet and exercise, offers the best opportunity to prevent progressive symptoms of sensory loss, pain, autonomic dysfunction, ulcerations, and amputations. Some patients with impaired glucose tolerance have a reversal of neuropathic features with tight glycemic control. Nonpharmacologic therapies for neuropathic pain in diabetic polyneuropathy appear promising.

SUMMARY

Tight glycemic control, especially early in diabetes, is the best approach to minimizing the prevalence and severity of diabetic polyneuropathy and makes research into the deleterious effects of even mild hyperglycemia imperative.

Therapy insight: neurological complications of prediabetes

Stroke and peripheral neuropathy are recognized neurological complications of diabetes. Increasing epidemiological evidence also implicates the prediabetic state of impaired glucose tolerance (IGT) as a risk factor for cerebrovascular events and peripheral neuropathy. Data linking IGT to cognitive decline or deficits, however, are less robust. IGT is one component of metabolic syndrome, together with central obesity, hypertension, hypertriglyceridemia and reduced HDL. Each component of metabolic syndrome is an independent risk factor for stroke, but hyperglycemia might be more important than other components in the pathogenesis of neuropathy. Goal-driven diet and exercise regimens, together with pharmacological treatment of hyperlipidemia and hypertension, reduce stroke risk, but the effect of these interventions on neuropathy has not been fully explored.

Postprandial hyperglycemia alters inflammatory and hemostatic parameters

Glucose or glucose derived products are increased in blood during the postprandial phase and are, to a certain extent, related to meal composition. Glucose and glucose derived products such as advanced glycation end products (AGEs) can be formed in the intracellular compartment but can also be absorbed as AGEs or AGE precursors present in food. Glucose, glucose metabolites and AGEs alter endothelial cell functions, induce adhesion molecule overexpression (ICAM-1, VCAM), cytokine release (IL-6, MCP-1) and tissue factor production. Tumor necrosis factor alpha systemic level is increased during the postprandial phase as are augmented C reactive protein and fibrinogen level. Hyperglycemia induced an increase in plasminogen activator inhibitor, and shortened fibrinogen half life. Hyperglycemia and AGEs provoked an oxidant stress. The formation of reactive oxygen intermediates perturbates NO (Nitric oxide) formation and are deleterious for cell functions. All the modifications observed in the postprandial phase are not too deleterious but their iterative characteristics may lead to vascular dysfunction.

Increased cyclooxygenase-2 expression and prostaglandin-mediated dilation in coronary arterioles of patients with diabetes mellitus

Based on findings of experimental models of diabetes mellitus (DM) showing increased expression of vascular cyclooxygenase-2 (COX-2), we hypothesized that in patients with DM changes in COX-2-dependent prostaglandin synthesis affect vasomotor responses of coronary arterioles. Arterioles were dissected from the right atrial appendages obtained at the time of cardiac surgery of patient with DM(+) or without documented diabetes DM(-). Isolated arterioles (89+/-15 microm in diameter) were cannulated and pressurized (at 80 mm Hg), and changes in diameter were measured with video microscopy. After spontaneous tone developed [DM(-): 32+/-7%; DM(+): 37+/-5%; P=NS], arteriolar responses to bradykinin were investigated. Dilations to bradykinin (0.1 nmol/L to 1 micromol/L) were significantly (P<0.05) greater in DM(+) than DM(-) patients (10 nmol/L: 77+/-10% versus 38+/-14%). In both groups, dilations were similar to the NO-donor, sodium nitroprusside. In arterioles of DM(+), but not those of DM(-), patients' bradykinin-induced dilations were reduced by the nonselective COX inhibitor indomethacin or by the selective COX-2 inhibitor NS-398 (DM(+) at 10 nmol/L: to 20+/-4% and 29+/-7%, respectively). Correspondingly, a marked COX-2 immunostaining was detected in coronary arterioles of DM(+), but not in those of DM(-) patients. We conclude that in coronary arterioles of diabetic patients bradykinin induces enhanced COX-2-derived prostaglandin-mediated dilation. These findings are the first to show that in humans diabetes mellitus increases COX-2 expression and dilator prostaglandin synthesis in coronary arterioles, which may serve to increase dilator capacity and maintain adequate perfusion of cardiac tissues.

Undiagnosed dysglycaemia and inflammation in cardiovascular disease

BACKGROUND

Cardiovascular (CV) disease is associated with increased levels of glucose, but the prevalence of dysglycaemia in CV diseases is not fully known. The study examined the prevalence of unknown dysglycaemia and its association with inflammation in Caucasian patients with ischaemic vascular complications, i.e. coronary artery disease (CAD), cerebrovascular disease (CVD) and peripheral artery disease (PAD).

MATERIALS AND METHODS

This case-controlled study involved 149 patients (mean age 68 years) hospitalized for CAD, PAD or CVD and 59 control-subjects (CTR) free from CV-disease. The prevalence of dysglycaemia according to WHO/ADA criteria (impaired fasting glycaemia, impaired glucose tolerance or diabetes mellitus) was assessed by a 75-g oral glucose tolerance test. Inflammatory parameters were analyzed in fasting samples.

RESULTS

Dysglycaemia was found in 49%, 55% and 57% of patients with CAD, CVD and PAD, respectively; all were significantly higher than among the controls (29%). The odds ratio (95% CI) for being dysglycaemic were 1.7 (1.04-2.77), 1.9 (1.19-3.06) and 2.0 (1.25-3.19) for CAD, CVD and PAD, respectively. Inflammatory markers (the total leucocyte count, soluble tumour necrosis factor-receptor type I, C-reactive protein) were elevated in patient groups and tended to increase with increasing blood glucose levels in all groups. The levels of the anti-inflammatory cytokine transforming growth factor-beta1 and insulin-like growth factor binding protein 3 were lowered in patients with CAD and, in patients with PAD, the former was inversely related to the levels of the blood glucose.

CONCLUSIONS

Undiagnosed dysglycaemia was common in patients with ischaemic CV manifestations regardless of vascular bed involved. Inflammation was associated in a dosage-related manner to glucose levels.

Insulin-status-dependent modulation of FoF1 ATPase activity in rat kidney mitochondria

The early and late effects of alloxan-diabetes and insulin treatment on kinetic properties of mitochondrial FoF1 ATPase were examined. Diabetic state resulted in significant decrease in the activity while insulin treatment caused hyper-stimulation. In control animals the enzyme activity resolved in three kinetic components. In diabetic condition only component I and II were present. With insulin treatment component III was restored but component II was abolished. Diabetic state and insulin treatment had varied effects on Km values of the three components, whereas the Vmax values were generally on the higher side. Evaluation of the AppKcat/Km values revealed that diabetic state resulted in increased catalytic efficiency; insulin treatment brought back these values to normality. Temperature kinetics studies indicated that the phase transition temperature decreased significantly in the diabetic and insulin-treated diabetic animals. The energy of activation in low temperature range increased in the diabetic animals. Insulin treatment corrected the Arrhenius pattern at early stage of diabetes; at late stage the pattern was reversed. The results are suggestive of subtle insulin-status-dependent alterations in membrane structure - function relationships.

Non-invasive methods and stimuli for evaluating the skin's microcirculation

Vessels in the skin are arranged into superficial and deep horizontal plexuses and they are involved in thermoregulation, oxygen and nutritional support. The skin has a large number of functions and broad appeal spanning basic mechanistic and clinical research. Indeed, the skin can be used as a marker of normal and impaired vascular control and, owing to its accessibility and frequent involvement, is easy to investigate non-invasively. A large number of non-invasive methods are available for investigating the skin, ranging from those that permit the visualisation of microvessels, to those that monitor blood flow or one of its derivatives (e.g., skin temperature and transcutaneous oxygen). Such methods can be combined with non-invasive, dynamic stimuli (e.g., the use of cold or warm stimuli, activation of the peripheral nervous system or local neuronal systems, and the topical application of vasoactive drugs) and this potentially enables the differentiation of underlying disorders (e.g., primary from secondary Raynaud's phenomenon) and also to quantify changes over time or following intervention. The present article outlines the non-invasive methods and dynamic tests that can be used to investigate the microcirculation of the skin.

Insulin-status-dependent modulation of FoF1-ATPase activity in rat liver mitochondria

Early and late effects of alloxan diabetes and insulin treatment on mitochondrial membrane structure and function were evaluated by studying the kinetic properties of mitochondrial membrane marker enzyme FoF1-ATPase and its modulation by membrane lipid/phospholipid composition and membrane fluidity. Under all experimental conditions the enzyme displayed three kinetically distinguishable components. In 1 wk-old diabetic animals the enzyme activity was unchanged; however, K(m) and V(max) of component I increased and K(m) of component II decreased. Insulin treatment resulted in lowering of K(m) and V(max) of components II and Ill. One-mon diabetic state resulted in decreased enzyme activity, whereas insulin treatment caused hyperstimulation. K(m) of components I and II decreased together with decreased V(max) of all the components. Insulin treatment restored the K(m) and V(max) values. In late-stage diabetes the catalytic efficiency of components I and II increased; insulin treatment had drastic adverse effect. Binding pattern of ATP was unchanged under all experimental conditions. Diabetic state resulted in progressive decrease in energy of activation in the low temperature range (E(L)). Insulin treatment lowered the energy of activation in the high temperature range (E(H)) without correcting the E(L) values. The phase transition temperatures increased in diabetic state and were not corrected by insulin treatment. Long-term diabetes lowered the total phospholipid content and elevated the cholesterol content; insulin treatment had partial restorative effect. The membrane fluidity decreased in general in diabetic condition and was not corrected by insulin treatment at late stage. Regression analysis studies suggest that specific phospholipid classes and/or their ratios may play a role in modulation of the enzyme activity.

Constant and intermittent high glucose enhances endothelial cell apoptosis through mitochondrial superoxide overproduction

BACKGROUND

It has been previously shown that hyperglycemia enhances free radical production, inducing oxidative damage, which in its turn activates the death pathways implicated in cell apoptosis and necrosis. But the possible involvement of this pathway in the hyperglycemia-induced apoptosis of endothelial cells has not yet been reported.

METHODS

To verify a possible connection between mitochondrial ROS production and apoptosis induced by both stable and oscillating high glucose, SOD, MnTBAP and TTFA was added to HUVEC cell culture medium. We measured nitrotyrosine and 8OHdG as oxidative stress parameters and Bcl-2 expression and Caspase-3 expression and activity as apoptosis indicators.

RESULTS

Our results show that hyperglycemia, both stable or oscillating, increases oxidative stress and endothelial cell apoptosis through ROS overproduction at the mitochondrial transport chain level.

CONCLUSION

The prevention of mitochondrial oxidative damage seems to be a future important therapeutic strategy in diabetes.

Heme oxygenase-1 enhances renal mitochondrial transport carriers and cytochrome C oxidase activity in experimental diabetes

Up-regulation of heme oxygenase (HO-1) by either cobalt protoporphyrin (CoPP) or human gene transfer improves vascular and renal function by several mechanisms, including increases in antioxidant levels and decreases in reactive oxygen species (ROS) in vascular and renal tissue. The purpose of the present study was to determine the effect of HO-1 overexpression on mitochondrial transporters, cytochrome c oxidase, and anti-apoptotic proteins in diabetic rats (streptozotocin, (STZ)-induced type 1 diabetes). Renal mitochondrial carnitine, deoxynucleotide, and ADP/ATP carriers were significantly reduced in diabetic compared with nondiabetic rats (p < 0.05). The citrate carrier was not significantly decreased in diabetic tissue. CoPP administration produced a robust increase in carnitine, citrate, deoxynucleotide, dicarboxylate, and ADP/ATP carriers and no significant change in oxoglutarate and aspartate/glutamate carriers. The increase in mitochondrial carriers (MCs) was associated with a significant increase in cytochrome c oxidase activity. The administration of tin mesoporphyrin (SnMP), an inhibitor of HO-1 activity, prevented the restoration of MCs in diabetic rats. Human HO-1 cDNA transfer into diabetic rats increased both HO-1 protein and activity, and restored mitochondrial ADP/ATP and deoxynucleotide carriers. The increase in HO-1 by CoPP administration was associated with a significant increase in the phosphorylation of AKT and levels of BcL-XL proteins. These observations in experimental diabetes suggest that the cytoprotective mechanism of HO-1 against oxidative stress involves an increase in the levels of MCs and anti-apoptotic proteins as well as in cytochrome c oxidase activity.

Do retinopathy signs in non-diabetic individuals predict the subsequent risk of diabetes?

BACKGROUND/AIMS

Isolated retinopathy signs are common in non-diabetic individuals and have been shown to be associated with impaired glucose metabolism. In a cohort of people without diabetes, the association of these retinopathy signs and subsequent development of diabetes were examined.

METHODS

A population based cohort study of 7992 people aged 49-73 years without diabetes was conducted. Retinal photographs of these participants were evaluated for the presence of retinopathy signs according to a standardised protocol. Incident cases of diabetes were identified prospectively.

RESULTS

After a follow up of 3 years, 291 (3.6%) people developed incident diabetes. In the total cohort, retinopathy was not significantly associated with incident diabetes (4.7% v 3.6%, multivariable adjusted odds ratio (OR) 1.1, 95% confidence intervals (CI), 0.7 to 1.9). However, among participants with a positive family history of diabetes, retinopathy was associated with incident diabetes (10.4% v 4.8%, multivariable adjusted OR 2.3, 95% CI, 1.0 to 5.3). Among participants without a family history of diabetes, retinopathy was not associated with incident diabetes

CONCLUSIONS

In individuals with a family history of diabetes, retinopathy signs predict subsequent risk of clinical diabetes.

Differential inhibition by hyperglycaemia of shear stress- but not acetylcholine-mediated dilatation in the iliac artery of the anaesthetized pig

Clinical hyperglycaemia affects vascular endothelial function, but the effect on shear stress-induced arterial dilatation has not yet been established. We hypothesized that hyperglycaemia would inhibit this response via impaired glycocalyx mechanotransduction. Experiments were carried out in the anaesthetized pig in which pressure, blood flow and diameter of the left iliac artery were measured at two sites: proximal (d1) and distal (d2). Infusion of glucose, sufficient to raise blood glucose to 16-30 mm along the whole length of the artery, attenuated the shear stress-dependent dilatation in both sections of the artery with preservation of the responses to acetylcholine. The distal site was then isolated using snares and the lumen exposed to blood containing 25-35 mm glucose for 20 min. In the control situation, after exposure of both sections to normoglycaemia (5.7 mm glucose), both sections of artery showed increases in diameter in response to shear stress and acetylcholine. Hyperglycaemia attenuated the shear stress-dependent dilatation in the distal section only (P < 0.25), but not the response to acetylcholine. It is concluded from these results that the hyperglycaemia-impaired dilatation is consistent with loss of mechanotransducing properties of the endothelial glycocalyx by hyperglycaemia. These findings offer a possible explanation for the increased incidence of vascular disease in diabetic patients.

Influence of obesity and insulin resistance on left atrial size in children

BACKGROUND

Left atrial (LA) enlargement has been linked to obesity and insulin resistance in adults.

OBJECTIVE

The purpose of this study was to determine the association in children between LA area and: (i) different components of the metabolic syndrome including obesity (OB), measures of body mass index (BMI) and waist circumference (WC), homeostasis model assessment-insulin resistance (HOMA-IR, proinsulin), and blood pressure (BP); and (ii) left ventricular mass (LVM) and diastolic function, measured using echo Doppler.

METHODS AND RESULTS

Eighty-four (44 females) subjects, [40 OB (BMI>95%), 28 overweight (BMI>85%)], 16 non-OB (BMI<85%)] aged 9+/-2.24 yrs were matched for sex and age. BMI, WC, BP, Tanner stage, and Mode M, 2-dimensional and Doppler transmitral echocardiography were assessed. A standard oral glucose tolerance test (OGTT) was done, measuring glucose, insulin, and proinsulin concentrations. Hypertension was only present in OB subjects (25%). Significant univariate association (p<0.001) was found between LA area and height (r=0.52), age (r=0.45), Tanner stage (r=0.45), BMI (r=0.66), WC (r=0.70), systolic BP (r=0.52), diastolic BP (r=0.53), proinsulin (r=0.36), and HOMA-IR (r=0.36). In the multivariate regression analysis, independent variables were entered in a stepwise fashion: initially, gender (p=0.006) and Tanner stage (p=0.011) were still significant independent correlates of LA area after adjusting for age, gender, and Tanner stage. Subsequently, incorporation of WC showed that WC (p=0.018) was a significant independent correlate of LA area. A larger model constructed to test the significance of adjustment factors, including WC, BP, LVM, and HOMA-IR showed that WC (p<0.001) was the only significant independent variable.

CONCLUSION

LA enlargement is present in childhood and is related to abdominal OB and insulin resistance, suggesting that children with central OB are at increased risk for cardiovascular disease.

Characterisation of morbidity in a UK, hospital based, obesity clinic

AIM

To identify clinical features which predict those most at risk of co-morbidities within an obesity clinic.

METHODS

Children attending an obesity clinic had fasting glucose, insulin, and lipids measured prior to a standard oral glucose tolerance test (OGTT). History and examination established birth weight, family history of type 2 diabetes/obesity, pubertal status, and presence of acanthosis nigricans. Central and total fat mass was estimated by bio-impedance.

RESULTS

Of the 126 children evaluated, 10.3% (n = 13) had impaired glucose tolerance (IGT); the majority (n = 11) of these would not have been identified on fasting glucose alone. Those with IGT were more likely to have a parental history of type 2 diabetes (relative risk 3.5). IGT was not associated with acanthosis nigricans. Twenty five per cent (n = 19) of those evaluated (n = 75) had evidence of the "metabolic syndrome" (MS). HDL cholesterol and triglyceride levels were related to insulin sensitivity (HOMA-R); HDL cholesterol was also related to birth weight SDS. We observed a trend for those with MS to have a lower birth weight SDS. The severity of obesity did not influence the likelihood of IGT or MS.

CONCLUSIONS

Significant numbers of obese children have associated co-morbidities. Analysis of fasting blood glucose samples alone is not satisfactory to adequately evaluate glucose homoeostasis. The overall level of obesity does not predict co-morbidities. Special attention should be given to those with parental diabetes and a history of low birth weight who are more likely to have IGT and abnormal lipid profiles respectively.

Is There a Rationale for Insulin Therapy in Pre-Diabetic Individuals?

Type 2 diabetes mellitus is usually preceded by impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG), which are often referred to as pre-diabetes. Individuals with IGT demonstrate beta-cell dysfunction, insulin resistance, and increased hepatic glucose production; IGT and IFG are risk factors for both diabetes and cardiovascular disease. Type 2 diabetes is associated with micro- and macrovascular complications that lead to excessive mortality and morbidity and the risk of microvascular complications extends to people with pre-diabetes. Maintaining good glycemic control in type 2 diabetes can reduce the risk of developing chronic disease-associated complications. Most individuals who develop type 2 diabetes appear to pass through a stage of IFG or IGT; thus, early intervention (lifestyle and/or pharmacologic) in individuals with pre-diabetes may help prevent cardiovascular disease and the development of type 2 diabetes.The use of exogenous insulin treatment offers the potential to reduce the cardiovascular risk in individuals with type 2 diabetes or pre-diabetes through effective reductions in blood glucose and lipid levels, and in the associated tissue damage resulting from their chronic elevations. However, there are barriers associated with insulin initiation in both type 2 diabetes and pre-diabetes (e.g. hypoglycemia, weight gain, the possible unpredictable action of long-acting insulin, and the need for injections). Insulin glargine, with its flat time-action profile, near 24-hour duration of action, reduced risk of hypoglycemia, and improved glycemic control compared with insulin suspension isophane (neutral protamine hagedorn [NPH] insulin), may help to overcome some of these barriers.Initial results from a small study have indicated the feasibility of treating individuals with pre-diabetes to near-normoglycemia using a regimen of low-dose insulin glargine plus caloric restriction. This is being followed up in the ongoing ORIGIN (Outcomes Reduction with Initial Glargine INtervention) study, which will investigate whether treatment to near-normoglycemia with insulin glargine in individuals with IGT, IFG, or new-onset type 2 diabetes can reduce cardiovascular morbidity and mortality compared with conventional management of these conditions, and whether the rate of progression to type 2 diabetes can be similarly reduced.Further studies are needed to investigate the potential benefits of insulin therapy in individuals with pre-diabetes.

Metabolic effects of the incretin mimetic exenatide in the treatment of type 2 diabetes

Interventional studies have demonstrated the impact of hyperglycemia on the development of vascular complications associated with type 2 diabetes, which underscores the importance of safely lowering glucose to as near-normal as possible. Among the current challenges to reducing the risk of vascular disease associated with diabetes is the management of body weight in a predominantly overweight patient population, and in which weight gain is likely with many current therapies. Exenatide is the first in a new class of agents termed incretin mimetics, which replicate several glucoregulatory effects of the endogenous incretin hormone, glucagon-like peptide-1 (GLP-1). Currently approved in the US as an injectable adjunct to metformin and/or sulfonylurea therapy, exenatide improves glycemic control through multiple mechanisms of action including: glucose-dependent enhancement of insulin secretion that potentially reduces the risk of hypoglycemia compared with insulin secretagogues; restoration of first-phase insulin secretion typically deficient in patients with type 2 diabetes; suppression of inappropriately elevated glucagon secretion to reduce postprandial hepatic output; and slowing the rate of gastric emptying to regulate glucose appearance into the circulation. Clinical trials in patients with type 2 diabetes treated with subcutaneous exenatide twice daily demonstrated sustained improvements in glycemic control, evidenced by reductions in postprandial and fasting glycemia and glycosylated hemoglobin (HbA(1c)) levels. Notably, improvements in glycemic control with exenatide were coupled with progressive reductions in body weight, which represents a distinct therapeutic benefit for patients with type 2 diabetes. Acute effects of exenatide on beta-cell responsiveness along with significant reductions in body weight in patients with type 2 diabetes may have a positive impact on disease progression and potentially decrease the risk of associated long-term complications.

Metabolic syndrome increases endogenous carbon monoxide production to promote hypertension and endothelial dysfunction in obese Zucker rats

Vascular heme oxygenase (HO) metabolizes heme to form carbon monoxide (CO). Increased heme-derived CO inhibits nitric oxide synthase and can contribute to hypertension via endothelial dysfunction in Dahl salt-sensitive rats. Obese Zucker rats (ZR) are models of metabolic syndrome. This study tests the hypothesis that endogenous CO formation is increased and contributes to hypertension and endothelial dysfunction in obese ZR. Awake obese ZR showed increased respiratory CO excretion, which was lowered by HO inhibitor administration [zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG) 25 micromol.kg(-1).24 h(-1) ip]. In awake obese ZR, chronically instrumented with femoral arterial catheters, blood pressure was elevated but was decreased by the HO inhibitor ZnDPBG. Body weight, blood glucose, glycated hemoglobin, plasma insulin, total and LDL cholesterol, oxidized LDL, and triglyceride levels were elevated in obese ZR, and, except for LDL cholesterol, were unchanged by HO inhibition. Total HO-1 protein levels were not different between lean and obese ZR aortas. In vitro experiments used isolated skeletal muscle arterioles with constant pressure and no flow, or constant midpoint, but altered endpoint pressures to establish graded levels of luminal flow. In obese ZR arterioles, responses to ACh and flow were attenuated. Acute in vitro pretreatment with an HO inhibitor, chromium mesoporphyrin, enhanced ACh and flow-induced dilation and abolished the differences between groups. Furthermore, exogenous CO prevented the restoration of flow-induced dilation by the HO inhibitor in obese ZR arterioles. These results suggest that HO-derived CO production is increased and promotes hypertension and arteriolar endothelial dysfunction in obese ZR with metabolic syndrome independent of affecting metabolic parameters.

Inflammation is more persistent in type 1 diabetic mice

Whether diabetes enhances or diminishes the host response to bacteria has been controversial. To determine how diabetes alters the inflammatory response, we inoculated P. gingivalis into the scalps of mice rendered diabetic with multiple low-dose streptozotocin treatment. On day 1, a moderate to severe inflammatory infiltrate was noted in both the diabetic and normoglycemic mice. After 3 days, the inflammatory infiltrate was significantly higher in the diabetic compared with the control group (P < 0.05). The mRNA expression of chemokines macrophage inflammatory protein-2 and monocyte chemoattractant protein-1 was strongly and similarly induced 3 hrs and 1 day post-inoculation. By day 3, the levels were reduced in normoglycemic mice but remained significantly higher in the diabetic group (P < 0.05). To determine whether persistent inflammation was specific for the streptozotocin-induced diabetic model, we directly compared the expression of TNF-alpha in streptozotocin-induced and db/db diabetic mice, which developed type 2 diabetes. Both exhibited prolonged TNF-alpha expression compared with controls. These results suggest that diabetes alters bacteria-host interactions by prolonging the inflammatory response.

Review article: hepatic steatosis and insulin resistance

Hepatic steatosis may be both an adaptive phenomenon and an example of lipotoxicity. Its prevalence ranks in the same order of magnitude of insulin resistance in the general population. Studies support the finding that hepatic steatosis is secondary to insulin resistance and not vice versa. A steatotic liver will further contribute to the development of insulin resistance through impaired clearance of insulin from the portal blood, creating a vicious cycle. Insulin resistance is the leading force in the pathogenesis and natural history of non-alcoholic fatty liver disease. Dysfunction of energetic homeostasis and the interaction of adiponectin, leptin and tumour necrosis factor-alpha are key events in the pathogenesis of steatosis and insulin resistance. Insulin resistance represents the frame within which hepatic and extrahepatic non-alcoholic fatty liver disease-related clinical manifestations are to be anticipated and interpreted.

Integrated Management of Patients with Diabetes Mellitus and Ischemic Heart Disease: PCI, CABG, and Medical Therapy

Modern coronary revascularization strategies are based on studies performed in the 1970s and 1980s that compared coronary artery bypass surgery with standard medical therapy available at the time. Studies comparing surgical and percutaneous revascularization followed, demonstrating similar long-term outcome among thousands of randomized patients. The largest of these trials, the Bypass Angioplasty Revascularization Investigation (BARI), cast doubt on the generalizability of these findings to all subgroups, finding that patients with diabetes mellitus and multivessel disease had worse long-term outcome with an initial strategy of percutaneous transluminal coronary angioplasty (PTCA). Indeed, patients with diabetes mellitus are at increased risk for cardiovascular morbidity and mortality, while the benefit of standard therapies in these patients is attenuated by the underlying metabolic abnormalities and significant comorbidities associated with the diabetic state. However, surgical and percutaneous revascularization techniques continue to evolve. Similarly, modern medical therapy is markedly superior to that available during these early studies, with demonstrable benefit in primary and secondary prevention of vascular events in both diabetic and nondiabetic patients. Ongoing trials will define the impact of current treatment modalities in this important and growing population.

Effect of ascorbic acid on microcirculation in patients with Type II diabetes: a randomized placebo-controlled cross-over study

Manifestations of vascular disease, including microvascular changes, constitute the major part of the morbidity and mortality in diabetic patients. Oxidative stress has been suggested to play an important role in the vascular dysfunction of diabetic patients. Furthermore, epidemiological observations indicate a beneficial effect of an increased dietary intake of antioxidants. The present study tested the hypothesis that the antioxidant ascorbic acid influences microcirculatory function in patients with Type II diabetes. Patients with Type II diabetes were treated with 1 g of ascorbic acid three times a day for 2 weeks in a randomized placebo-controlled double-blind cross-over design. Microvascular reactivity was assessed by vital capillaroscopy and PRH (post-occlusive reactive hyperaemia). hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-1ra (interleukin-1 receptor antagonist) and ox-LDL (oxidized low-density lipoprotein) were analysed. The results showed no significant change in microvascular reactivity assessed after 2 weeks of ascorbic acid treatment. TtP (time to peak) was 12.0+/-3.3 s before and 11.2+/-3.5 s after ascorbic acid (n=17). In comparison, TtP was 11.5+/-2.9 s before and 10.6+/-2.8 s after placebo (not significant). IL-1ra, IL-6, hs-CRP and ox-LDL did not change significantly after ascorbic acid, neither as absolute or relative values. In conclusion, in contrast with some studies reported previously, we could not demonstrate an effect of continuous oral treatment with ascorbic acid on microvascular reactivity assessed at the level of individual capillaries. Furthermore, we found no indication of an effect on inflammatory cytokines or ox-LDL.

Progression of vascular and neural dysfunction in sciatic nerves of Zucker diabetic fatty and Zucker rats

We have examined the progression of vascular and neural deficits in Zucker rats, Zucker diabetic fatty (ZDF) diabetic rats, and age-matched lean ZDF rats from 8 to 40 wk of age. Both the ZDF diabetic and Zucker rats were glucose intolerant at 8 wk of age. The Zucker rats did not become hyperglycemic but were hyperinsulinemic through 32 wk of age. All ZDF diabetic rats became hyperglycemic by 8 wk of age. Through their life span, serum free fatty acids and triglycerides levels were significantly higher in Zucker and ZDF diabetic rats compared with age-matched lean ZDF rats. After 24 and 28 wk of age, endoneurial blood flow was significantly decreased in ZDF diabetic and Zucker rats. Motor nerve conduction velocity was significantly decreased after 12-14 wk of age in ZDF diabetic rats and at 32 wk of age in Zucker rats. ACh-mediated vascular relaxation of epineurial arterioles of the sciatic nerve was impaired after 8-10 wk of age in ZDF diabetic rats and after approximately 16 wk of age in Zucker rats. In contrast, vascular relaxation mediated by calcitonin gene-related peptide was impaired significantly after 28 wk of age in ZDF diabetic rats but not impaired in Zucker rats up to 40 wk of age. Markers of oxidative stress were differentially elevated in ZDF diabetic rats and Zucker rats. These data indicate that vascular and neural dysfunction develops in both Zucker and ZDF diabetic rats but at different rates, which may be the result of hyperglycemia.

Effect of hepatic lipase -514C->T polymorphism and its interactions with apolipoprotein C3 -482C->T and apolipoprotein E exon 4 polymorphisms on the risk of nephropathy in chinese type 2 diabetic patients

OBJECTIVE

Triglyceride-rich lipoprotein particles may promote the progression of diabetic nephropathy. Patients with diabetic nephropathy have increased plasma triglycerides and reduced activity of hepatic lipase (HL), which hydrolyzes triglycerides. We hypothesized that the HL -514C-->T polymorphism, which reduces HL expression, and its interactions with polymorphisms in apolipoprotein (apo) E and apoC3 increase the risk of diabetic nephropathy.

RESEARCH DESIGN AND METHODS

In a case-control study involving 374 Chinese type 2 diabetic patients with and 392 without diabetic nephropathy, we genotyped the HL -514C-->T, apoE exon 4, and apoC3 -482C-->T polymorphisms.

RESULTS

HL -514T-containing genotypes (T+) were associated with diabetic nephropathy (OR = 1.7, P = 0.0009). Adjustment by multiple logistic regression for hypertension, triglycerides, sex, non-HDL cholesterol, BMI, smoking, and alcohol intake did not diminish the association (OR = 1.8, P = 0.003). The association between HL T+ genotypes and diabetic nephropathy appeared stronger in diabetic patients with apoC3 -482 non-TT genotypes (OR = 1.9, P = 0.003) or apoE epsilon2 or epsilon4 alleles (OR = 2.2, P = 0.005). Subjects with HL TT exhibited trends toward increased triglyceride and non-HDL cholesterol levels compared with CC carriers.

CONCLUSIONS

HL T+ genotypes might increase the risk of developing diabetic nephropathy by slowing clearance of triglyceride-rich remnant lipoproteins. In concert with other risk factors (e.g., hyperglycemia), lipid abnormalities may damage the kidneys and endothelium, where reduced binding sites for lipases may precipitate a vicious cycle of dyslipidemia, proteinuria, and nephropathy.

High glucose evokes an intrinsic proapoptotic signaling pathway in mesangial cells

BACKGROUND

In response to chronic hyperglycemia, microvascular cells undergo stress and injury, which can lead to cell death. We characterized a proapoptotic signaling pathway whereby high glucose evokes an intrinsic, caspase-9-dependent mechanism of cell death in human mesangial cells.

METHODS

Biochemical (caspase activity, cytochrome-c release, etc.) and morphologic (chromatin condensation and nuclear segmentation) features of apoptotic cell death were assessed in cultured human mesangial cells exposed to high glucose, a risk factor for mesangial cell injury and diabetic glomerulosclerosis. Proapoptotic signaling was also analyzed in the db/db murine model of kidney injury in diabetes.

RESULTS

Incubation in high glucose caused cytotoxicity and apoptosis in mesangial cells. High glucose stimulated mitochondrial release of cytochrome-c, cleavage of procaspase-9, and caspase-9 enzyme activity, suggesting an intrinsic pathway of proapoptotic signaling. In contrast, caspase-8 was unaffected by high glucose. A cell-permeable, caspase-9-selective inhibitor blocked caspase-3 activation and prevented chromatin condensation and nuclear segmentation in cells treated with high glucose. To determine whether an intrinsic signaling pathway occurs in the diabetic kidney in vivo, apoptosis was investigated in diabetic 8- and 16-week db/db murine kidneys. Effector caspases-3 and -7 were activated in diabetic db/db kidneys but not in age-matched nondiabetic db/m controls. At 16 weeks, apoptotic cells in db/db glomeruli were identified on the basis of nuclear segmentation and DNA fragmentation. Apoptosis of glomerular cells correlated with expansion of the mesangial matrix and with worsening of albuminuria. Consistent with an intrinsic signaling pathway, caspase-9 cleavage was elevated only in db/db kidneys, whereas activation of caspase-8 and caspase-12 was undetectable.

CONCLUSION

These findings support the hypothesis that hyperglycemia evokes an intrinsic pathway of proapoptotic signaling in mesangial cells. In addition, these results point to an important role for the intrinsic pathway in microvascular injury in the diabetic kidney in vivo.

Putative roles of kinin receptors in the therapeutic effects of angiotensin 1-converting enzyme inhibitors in diabetes mellitus

The role of endogenous kinins and their receptors in diabetes mellitus is being confirmed with the recent developments of molecular and genetic animal models. Compelling evidence suggests that the kinin B(2) receptor is organ-protective and partakes to the therapeutic effects of angiotensin 1-converting enzyme inhibitors (ACEI) and angiotensin AT(1) receptor antagonists. Benefits derive primarily from vasodilatory, antihypertensive, antiproliferative, antihypertrophic, antifibrotic, antithrombotic and antioxidant properties of kinin B(2) receptor activation. Mechanisms include the formation of nitric oxide and prostacyclin and the inhibition of NAD(P)H oxidase activity involving classical and novel signalling pathways. Kinin B(2) receptor also ameliorates insulin resistance by increasing glucose uptake and supply, and by inducing glucose transporter-4 translocation either directly or through phosphorylation of insulin receptor. The kinin B(1) receptor, which is induced by the cytokine network, growth factors and hyperglycaemia, mediates hyperalgesia, vascular hyperpermeability and leukocytes infiltration in diabetic animals. However, emerging data highlight reno- and cardio-protective effects mediated by kinin B(1) receptor under chronic ACEI therapy in diabetes mellitus. Thus, the Janus-faced of kinin receptors needs to be taken into account in future drug development. For instance, locally acting kinin B(1)/B(2) receptor agonists if used in a safe therapeutic window may represent a more rationale strategy in the prevention and management of diabetic complications. Because kinin B(2) receptor antagonists may further increase insulin resistance, the persisting dogma that restricts the development of kinin receptor analogues to antagonists (that is still relevant to abrogate pain and inflammation) needs to be revisited.

Bimodality of 2-h plasma glucose distributions in whites: the Rancho Bernardo study

OBJECTIVE

Several studies have shown a bimodal curve in the distribution of glucose in populations with a high prevalence of type 2 diabetes, but bimodality has not been reported among whites of Northern European ancestry. It is not clear whether this difference reflects the lower prevalence of diabetes, obscuring a second mode, or implies a more fundamental difference between whites and nonwhites. We investigate this issue by studying glucose distributions in older white patients.

RESEARCH DESIGN AND METHODS

A study of diabetes was conducted among older community-dwelling white residents of a suburban Southern California community between 1984 and 1987. Two-hour plasma glucose data were collected from 2,326 older white men and women aged 23-92. To investigate bimodality of glucose distributions, we fit unimodal and bimodal normal models to 2-h plasma glucose concentrations transformed by the Box-Cox family of transformations.

RESULTS

We found that the bimodal normal mixture model fit the data significantly better than the unimodal skewed distribution model for both sexes and all age-groups except those > or =80 years. The cut points separating the two modes were generally within the 11.1- to 13.6-mmol/l range.

CONCLUSIONS

The bimodality of glucose distributions among whites, combined with previous findings, indicates that this phenomenon may be universal. A smaller second mode in our study compared with other studies suggests that whites have diabetes susceptibility but may require more obesity to demonstrate it. With increasing obesity in the U.S., the predicted epidemic of diabetes may affect all ethnic groups including whites.

Epidemiology of diabetes mellitus and associated cardiovascular risk factors: focus on human immunodeficiency virus and psychiatric disorders

Type 2 diabetes mellitus and obesity have reached epidemic proportions in many developing and developed nations, leading to talk of the "twin epidemics." The latest projections from the International Diabetes Federation suggest that 190 million people worldwide currently have type 2 diabetes. In addition, > or = 300 million people worldwide have impaired glucose tolerance (IGT). These statistics represent an epidemic of major proportions--possibly the largest epidemic in human history--in terms of glucose intolerance and cardiovascular disease (CVD) risk because individuals with IGT are at substantially higher risk for diabetes and CVD than are members of the general population. Along with IGT, the metabolic syndrome comprises other major CVD risk factors, including insulin resistance, central obesity, and dyslipidemia; insulin resistance has been implicated as the single most common cause of the syndrome. Although the exact prevalence of the metabolic syndrome is unknown, the syndrome is widespread among adults in developed nations, becoming more prevalent with age. Epidemiologic data suggest that in patients with schizophrenia or affective disorders, both diabetes and obesity are 1.5 to 2.0 times more prevalent than in the general population. Furthermore, because adverse effects of certain therapies for human immunodeficiency virus (HIV) infection and psychiatric disorders increase the risk for developing diabetes, obesity, and the metabolic syndrome, such therapies should be carefully chosen, particularly considering CVD risk. Appropriate therapy may be determined via screening of patients for levels of fasting blood glucose and lipids, as well as other CVD risk factors, before initiating use of second-generation antipsychotic agents or highly active antiretroviral therapy.

Diabetic Neuropathies

Diabetes mellitus is associated with a wide spectrum of neuropathy syndromes, ranging from a mild asymptomatic distal sensory neuropathy to a severe disabling radiculoplexus neuropathy. As the pathophysiology of these separate conditions is better understood, classification of the various phenotypes becomes important because of treatment implications. Here we provide a short summary of the history of the classification of diabetic neuropathies and try to describe the most common forms classified according to their presumed pathophysiology. We have tried to include epidemiological data where available, as well as histopathology of nerve in several diabetic neuropathies.

Blood glucose and heart failure in nondiabetic patients

OBJECTIVE

Nondiabetic patients were studied to determine whether increasing blood glucose is associated with subsequent incidence of heart failure.

RESEARCH DESIGN AND METHODS

Baseline morning blood glucose determinations were evaluated with respect to subsequent heart failure using records from 20,810 nondiabetic patients. The onset of heart failure >1 year after initial glucose determinations was evaluated for patients who had 2-12 years of care. Patients were excluded if they had ever had the diagnosis of diabetes, had a diagnosis of heart failure <1 year after initial blood glucose determinations, had a blood glucose determination >125 mg/dl, or used corticosteroids, loop diuretics, insulin, or oral hypoglycemics.

RESULTS

Of the 20,810 patients studied, 916 patients developed heart failure over a total analysis time of 71,890 years at risk. Higher baseline morning glucose levels were associated with increased heart failure from 3.5% (glucose <90 mg/dl) to 3.8% (90-99 mg/dl) to 4.8% (100-109 mg/dl) to 6% (110-125 mg/dl) over a mean 4- to 5-year evaluation period. The incidence rate increased from 7.5 cases per 1,000 person-years (glucose <90 mg/dl) to 8.4 (90-99 mg/dl, NS) to 11.1 (100-109 mg/dl, P < 0.001) to 13.7 (110-125 mg/dl, P < 0.0001), an 83% increase in heart failure if baseline glucose was >109 mg/dl compared with <90 mg/dl. A Cox proportionate hazards model including age, sex, BMI, creatinine, hypertension, lipids, smoking, medications, and coronary disease showed a progressive increase in hazard ratio from 1.25 (glucose 90-99 mg/dl, P < 0.05) to 1.46 (100-109 mg/dl, P < 0.001) to 1.55 (110-125 mg/dl, P < 0.001) compared with glucose <90 mg/dl. Kaplan-Meier analysis showed increased glucose- associated risk with time.

CONCLUSIONS

Patients with higher baseline blood glucose levels in the absence of diabetes and after adjustment for covariants have a significantly increased risk of heart failure.

Short‐term hyperglycemia produces oxidative damage and apoptosis in neurons

Dorsal root ganglia neurons in culture die through programmed cell death when exposed to elevated glucose, providing an in vitro model system for the investigation of the mechanisms leading to diabetic neuropathy. This study examines the time course of programmed cell death induction, regulation of cellular antioxidant capacity, and the protective effects of antioxidants in neurons exposed to hyperglycemia. We demonstrate that the first 2 h of hyperglycemia are sufficient to induce oxidative stress and programmed cell death. Using fluorimetric analysis of reactive oxygen species (ROS) production, in vitro assays of antioxidant enzymes, and immunocytochemical assays of cell death, we demonstrate superoxide formation, inhibition of aconitase, and lipid peroxidation within 1 h of hyperglycemia. These are followed by caspase-3 activation and DNA fragmentation. Antioxidant potential increases by 3-6 h but is insufficient to protect these neurons. Application of the antioxidant alpha-lipoic acid potently prevents glucose-induced oxidative stress and cell death. This study identifies cellular therapeutic targets to prevent diabetic neuropathy. Since oxidative stress is a common feature of the micro- and macrovascular complications of diabetes, the present findings have broad application to the treatment of diabetic patients.

Postprandial hyperglycemia and diabetes complications: is it time to treat?

Increasing evidence suggests that the postprandial state is a contributing factor to the development of atherosclerosis. In diabetes, the postprandial phase is characterized by a rapid and large increase in blood glucose levels, and the possibility that the postprandial "hyperglycemic spikes" may be relevant to the onset of cardiovascular complications has recently received much attention. Epidemiological studies and preliminary intervention studies have shown that postprandial hyperglycemia is a direct and independent risk factor for cardiovascular disease (CVD). Most of the cardiovascular risk factors are modified in the postprandial phase in diabetic subjects and directly affected by an acute increase of glycemia. The mechanisms through which acute hyperglycemia exerts its effects may be identified in the production of free radicals. This alarmingly suggestive body of evidence for a harmful effect of postprandial hyperglycemia on diabetes complications has been sufficient to influence guidelines from key professional scientific societies. Correcting the postprandial hyperglycemia may form part of the strategy for the prevention and management of CVDs in diabetes.

Insulin resistance does not diminish eNOS expression, phosphorylation, or binding to HSP-90

Previously, using an animal model of syndrome X, the obese Zucker rat (OZR), we documented impaired endothelium-dependent vasodilation. The aim of this study was to determine whether reduced expression or altered posttranslational regulation of endothelial nitric oxide synthase (eNOS) underlies the vascular dysfunction in OZR rats. There was no significant difference in the relative abundance of eNOS in hearts, aortas, or skeletal muscle between lean Zucker rats (LZR) and OZR regardless of age. There was no difference in eNOS mRNA levels, as determined by real-time PCR, between LZR and OZR. The inability of insulin resistance to modulate eNOS expression was also documented in two additional in vivo models, the ob/ob mouse and the fructose-fed rat, and in vitro via adenoviral expression of protein tyrosine phosphatase 1B in endothelial cells. We next investigated whether changes in the acute posttranslational regulation of eNOS occurs with insulin resistance. Phosphorylation of eNOS at S632 (human S633) and T494 was not different between LZR and OZR; however, phosphorylation of S1176 was significantly enhanced in OZR. Phosphorylation of S1176 was not different in the ob/ob mouse or in fructose-fed rats. The association of heat shock protein 90 with eNOS, a key regulatory step controlling nitric oxide and aberrant O2−production, was not different between OZR and LZR. Taken together, these results suggest that changes in eNOS expression or posttranslation regulation do not underlie the vascular dysfunction seen with insulin resistance and that other mechanisms, such as altered localization, reduced availability of cofactors, substrates, and the elevated production of O2−, may be responsible.

Short-term peaks in glucose promote renal fibrogenesis independently of total glucose exposure

Postprandial hyperglycemia is implicated as a risk factor predisposing to vascular complications. This study was designed to assess recurrent short-term increases in glucose on markers of renal fibrogenesis. Human renal cortical fibroblasts were exposed to fluctuating short-term (2 h) increases to 15 mM d-glucose, three times a day over 72 h, on a background of 5 mM d-glucose. To determine whether observed changes were due to fluctuating osmolality, identical experiments were undertaken with cells exposed to l-glucose. Parallel experiments were performed in cells exposed to 5 mM d-glucose and constant exposure to either 15 or 7.5 mM d-glucose. Fluctuating d-glucose increased extracellular matrix, as measured by proline incorporation (P < 0.05), collagen IV (P < 0.005), and fibronectin production (P < 0.001), in association with increased tissue inhibitor of matrix metalloproteinase (MMP) (P < 0.05). Sustained exposure to 15 mM d-glucose increased fibronectin (P < 0.001), in association with increased MMP-2 (P = 0.01) and MMP-9 activity (P < 0.05), suggestive of a protective effect on collagen matrix accumulation. Transforming growth factor-beta(1) (TGF-beta(1)) mRNA was increased after short-term (90 min) exposure to 15 mM glucose (P < 0.05) and after 24-h exposure to 7.5 mM ? (P < 0.05). Normalization of TGF-beta(1) secretion occurred within 48 h of constant exposure to an elevated glucose. Fluctuating l-glucose also induced TGF-beta(1) mRNA and a profibrotic profile, however, to a lesser extent than observed with exposure to fluctuating d-glucose. The results suggest that exposure to fluctuating glucose concentrations increases renal interstitial fibrosis compared with stable elevations in d-glucose. The effects are, in part, due to the inherent osmotic changes.