Impaired vascular function during short-term poor glycaemic control in Type 1 diabetic patients

Effects of "metabolic memory" on erectile function in diabetic men: A retrospective case-control study

OBJECTIVE

This study was performed to explore the effects of metabolic memory on diabetic erectile dysfunction (ED), especially the severity and response to treatment.

METHODS

Through medical records and follow-up by telephone, 67 patients meeting the criteria with a clinical diagnosis of ED and a diabetic history of more than 5 years were enrolled for erectile function analysis. They were divided into a glycemic control group, a glycemic non-control group and a metabolic memory group according to glycemic levels and treatments for diabetes in the past 5 years, and they were treated with phosphodiesterase type 5 (PDE5) inhibitors for 4 weeks. Erectile function and efficacy were assessed by the International Index for Erectile Function (IIEF), the Erection Hardness Score (EHS), and the Sexual Encounter Profile (SEP).

RESULTS

The patients in the glycemic control group performed better in erectile function than those in the other groups. The patients in the glycemic control group received a significantly greater score on both the EHS and the five domains of the IIEF than did the patients in the glycemic non-control group and the metabolic memory group (all P < .001). There were also statistically significant differences favoring the glycemic control group (P < .05) in SEP2 and SEP3 success rates. However, there were no significant differences between the metabolic memory group and the glycemic non-control group in these erectile function assessments (P > .05). Significant negative correlations were seen between HbA1c levels at the time of consultation and the scores on the IIEF-EF and the EHS (Pearson r-values of -0.338 with P = .005 and -0.273 with P = .025, respectively). HbA1c levels at the first diagnosis of diabetes mellitus (DM) were also significantly negatively correlated with scores on the IIEF-EF and the EHS with greater Pearson correlation coefficients (Pearson r-values of -0.478 with P < .001 and -0.392 with P = .001, respectively). Significant improvements on each of the erectile function assessments were observed among diabetic patients with ED, but no significant difference in efficacy was observed between each group.

CONCLUSIONS

The phenomenon of metabolic memory did have a significant influence on ED in men with diabetes, associated with the severity of ED but not the response to medical treatment. Early hyperglycemia exposure would have long-term disadvantageous effects on erectile function in diabetic patients with ED, which would be sustained even after the patients achieve better glycemic control.

PATIENTS SUMMARY

In this report, we looked at the erectile functions of 67 patients with a clinical diagnosis of ED and a diabetic history of more than 5 years. We found that early hyperglycemia exposure would have long-term disadvantageous effects on erectile function in diabetic patients with ED, which would be sustained even after the patients achieve better glycemic control. We further found that the effects were associated with the severity of ED but not the response to medical treatment in men with diabetes.

Pituitary adenylate cyclase-activating polypeptide ameliorates vascular dysfunction induced by hyperglycaemia

BACKGROUND

Short-lasting hyperglycaemia occurs frequently in prediabetes and poorly controlled diabetes mellitus leading to vascular damage. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to play a protective role in vascular complications of diabetes; moreover, antioxidant effects of PACAP were also described. Therefore, we hypothesized that PACAP exerts protective effects in short-term hyperglycaemia-induced vascular dysfunctions.

METHODS

After short-term hyperglycaemia, acetylcholine-induced and sodium nitroprusside-induced vascular relaxation of mouse carotid arteries were tested with a myograph with or without the presence of PACAP or superoxide dismutase. Potential direct antioxidant superoxide-scavenging action of pituitary adenylate cyclase-activating peptide was tested with pyrogallol autoxidation assay; furthermore, the effect of pituitary adenylate cyclase-activating peptide or superoxide dismutase was investigated on hyperglycaemia-associated vascular markers.

RESULTS

PACAP administration resulted in reduced endothelial dysfunction after a 1-h hyperglycaemic episode. PACAP was able to restore acetylcholine-induced relaxation of the vessels and improved sodium nitroprusside-induced relaxation. This effect was comparable to the protective effect of superoxide dismutase, but PACAP was unable to directly scavenge superoxide produced by autoxidation of pyrogallol. Endothelial dysfunction was associated with elevated levels of fibroblast growth factor basic, matrix metalloproteinase 9 and nephroblastoma overexpressed gene proteins. Their release was reduced by PACAP administration.

CONCLUSION

These results suggest a strong protective role of PACAP in the vascular complications of diabetes.

VEGF, the underlying factor for metabolic syndrome; fact or fiction?

Metabolic syndrome (MetS) is currently diagnosed by the co-presence of at least three of the five following abnormalities: abdominal obesity, dysglycaemia, elevated serum triglycerides, low high-density cholesterol (HDL) and finally elevated blood pressure. Metabolic syndrome increases the risk of developing cardiovascular disease and diabetes. This review is on the associations between MetS and vascular endothelial growth factor (VEGF). VEGF induces migration and proliferation of endothelial cells (ECs), increases vascular permeability and has a role in tumor growth, adipose tissue expansion, age-related macular degeneration and diabetic retinopathy. Circulating levels of VEGFs are elevated in obese individuals and it has also been suggested that VEGF is secreted from adipose tissues, especially from intra-abdominal adipose tissue. There is abundant evidence to support that poor glycemic control in diabetic patients is associated with increased plasma VEGF, which in turn may cause hypertension and several vascular complications in diabetic patients. Circulating VEGF levels are increased in children and young adults with type 1 diabetes mellitus and middle-aged diabetic patients with proliferative retinopathy. It has been revealed that plasma VEGF increases in patients with hyperlipidemia and may trigger the development of atherosclerosis. It can be concluded that there is a positive association between VEGF and components of MetS. Because of the importance of this relationship, more investigations are needed in this field.

Clinical usefulness of videocapillaroscopy and selected endothelial cell activation markers in people with Type 1 diabetes mellitus complicated by microangiopathy

PURPOSE

Microvascular abnormalities are one of the most important causes of persistent diabetic complications. The aim of our study was to compare microvascular changes examined by nailfold videocapillaroscopy (NVC) examination with serum concentrations of vascular endothelial growth factor (VEGF), soluble thrombomodulin (sTM) and endothelin-1 (ET-1) in people with Type 1 diabetes with and without microangiopathy.

MATERIAL/METHODS

The study included 106 people with Type 1 diabetes and 40 healthy controls. All participants were evaluated by extensive clinical, laboratory and capillaroscopic studies. NVC was performed using a stereomicroscope SZ 4045 (Olympus, Germany). The intensity of morphological changes was graded from 0 to 3. Serum levels of VEGF, sTM and ET-1 were determined by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Morphological changes were observed by NVC in 86 out of 106 (81%) people with Type 1 diabetes mellitus. Severe capillaroscopic changes (score 3) were seen in 32 out of 54 (59%) people with microangiopathy, but in only seven out of 52 (13%) individuals without microangiopathy. Higher serum concentration of VEGF (p<0.001), ET-1 (p<0.001) and sTM (p<0.05) were demonstrated in people with diabetes complicated with microangiopathy compared to healthy controls. Moreover, comparison between people with and without microangiopathic complications showed a significantly higher capillaroscopic score and sTM serum concentration in the group with retinopathy (p<0.001) nephropathy (p<0.001) and neuropathy (p<0.01).

CONCLUSIONS

Our results suggest that abnormalities in NVC may reflect the extent of microvascular involvement and associated with higher VEGF, sTM and ET-1 serum levels, as well as with microangiopathic complications in diabetic people.

Clinical implications of oxidative stress and potential role of natural antioxidants in diabetic vascular complications

AIMS

The possible link between hyperglycaemia-induced oxidative stress (OxS) and diabetic complications is suggested by many in vitro studies. However, not much attention has been paid to the clinical evidence supporting this hypothesis, as well as to their possible therapeutic implications.

DATA SYNTHESIS

Some prospective studies show a direct correlation between an increase in OxS biomarkers and the appearance of diabetes complications. This is consistent with the evidence that any acute increase of glycaemia, particularly post-prandial, and hypoglycaemia causes endothelial dysfunction and inflammation, through the generation of an OxS. However, the detection of free radicals is difficult as they are highly reactive molecules with a short half-life. Instead, the metabolites of OxS are measured. Interventional trials with supplemented antioxidants have failed to show any beneficial effects. Conversely, natural foods show very promising results.

CONCLUSIONS

The "new antioxidant" approach includes the possibility of controlling free radical production and increasing intracellular antioxidant defence, a concept different from the old one, when antioxidant activities implied scavenging the free radicals already produced. A synergistic action in this respect could convincingly be obtained with a balanced 'Mediterranean Diet' (MedD) type. Early intensive glucose control is still the best strategy to avoid OxS and its associated diabetes complications.

Establishment of an Animal Model of Bisphosphonate-Related Osteonecrosis of the Jaws in Spontaneously Diabetic Torii Rats

Background

We evaluated the side effects of bisphosphonate (BP) on tooth extraction socket healing in spontaneously diabetic Torii (SDT) rats, an established model of non-obese type 2 diabetes mellitus, to develop an animal model of BP-related osteonecrosis of the jaws (BRONJ).

Materials and Methods

Male Sprague-Dawley (SD) rats and SDT rats were randomly assigned to the zoledronic acid (ZOL)-treated groups (SD/ZOL or SDT/ZOL) or to the control groups (SD/control or SDT/control). Rats in the SD/ZOL or SDT/ZOL groups received an intravenous bolus injection of ZOL (35 μg/kg) every 2 weeks. Each group consisted of 6 rats each. Twenty-one weeks after ZOL treatment began, the left maxillary molars were extracted. The rats were euthanized at 2, 4, or 8 weeks after tooth extraction, and the total maxillae were harvested for histological and histochemical studies.

Results

In the oral cavity, bone exposure persisted at the tooth extraction site in all rats of the SDT/ZOL group until 8 weeks after tooth extraction. In contrast, there was no bone exposure in SD/control or SDT/control groups, and only 1 of 6 rats in the SD/ZOL group showed bone exposure. Histologically, necrotic bone areas with empty lacunae, microbial colonies, and less invasion by inflammatory cells were observed. The number of tartrate-resistant acid phosphatase-positive osteoclasts was lower in the SDT/ZOL group than in the SD/control group. The mineral apposition rate was significantly lower in the SDT/ZOL group compared with the SD/control group.

Conclusions

This study demonstrated the development of BRONJ-like lesions in rats and suggested that low bone turnover with less inflammatory cell infiltration plays an important role in the development of BRONJ.

Study of ambulatory blood pressure in diabetic children: prediction of early renal insult

Background

Hypertension is a highly prevalent risk factor for cardiovascular disease in patients with type 1 diabetes mellitus. Elevated blood pressure (BP) promotes the development and progression of microvascular complications, eg, nephropathy and retinopathy. The purpose of this study was to identify and detect early BP changes in diabetic children and adolescents, aiming for the early prediction of future renal and cardiovascular disease risk during childhood.

Methods and materials

Ambulatory BP monitoring was undertaken for 40 normotensive type 1 diabetic children with mean age of 11.56±2.82 years, and 24 healthy children as control group with matched age and sex. Albumin/creatinine ratio and glycated hemoglobin were tested. BP indices and standard deviation scores were calculated using reference standards. The data were analyzed by SPSS software version 20 using mean and standard deviations for descriptive data. Correlation and regression analysis tests were used to study relations between BP indices and diabetic parameters.

Results

All parameters of BP z-scores were highly significantly increased in diabetic patients compared with controlled group (P<0.0001). The frequency of non-dipping was greater and highly significant in microalbuminuric diabetic patients (P<0.0001). Regression analysis revealed that BP parameters were significantly related to albumin/creatinine ratio, glycated hemoglobin, insulin dose, and body mass index.

Conclusion

Our observation revealed a clear link between the nocturnal BP and microalbuminuria which mandates BP follow-up via ambulatory BP monitoring with therapeutic intervention to prevent renal and cardiovascular diabetic complications in adulthood.

Protein kinase C-β contributes to impaired endothelial insulin signaling in humans with diabetes mellitus

BACKGROUND

Abnormal endothelial function promotes atherosclerotic vascular disease in diabetes. Experimental studies indicate that disruption of endothelial insulin signaling, through the activity of protein kinase C-β (PKCβ) and nuclear factor κB, reduces nitric oxide availability. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes mellitus.

METHODS AND RESULTS

We measured protein expression and insulin response in freshly isolated endothelial cells from patients with type 2 diabetes mellitus (n=40) and nondiabetic controls (n=36). Unexpectedly, we observed 1.7-fold higher basal endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 in patients with diabetes mellitus (P=0.007) without a difference in total eNOS expression. Insulin stimulation increased eNOS phosphorylation in nondiabetic subjects but not in diabetic patients (P=0.003), consistent with endothelial insulin resistance. Nitrotyrosine levels were higher in diabetic patients, indicating endothelial oxidative stress. PKCβ expression was higher in diabetic patients and was associated with lower flow-mediated dilation (r=-0.541, P=0.02). Inhibition of PKCβ with LY379196 reduced basal eNOS phosphorylation and improved insulin-mediated eNOS activation in patients with diabetes mellitus. Endothelial nuclear factor κB activation was higher in diabetes mellitus and was reduced with PKCβ inhibition.

CONCLUSIONS

We provide evidence for the presence of altered eNOS activation, reduced insulin action, and inflammatory activation in the endothelium of patients with diabetes mellitus. Our findings implicate PKCβ activity in endothelial insulin resistance.

Vascular smooth muscle responsiveness to nitric oxide is reduced in healthy adults with increased adiposity

Vascular smooth muscle responsiveness to nitric oxide, as assessed by nitroglycerin-induced dilation (NID), is impaired in clinical cardiovascular disease, but its relation to adiposity is unknown. We determined the relation of NID to total and abdominal adiposity in healthy adults varying widely in adiposity. In 224 men and women [age, 18-79 years; body mass index (BMI), 16.4-42.2 kg/m(2)], we measured NID (brachial artery dilation to 0.4 mg sublingual nitroglycerin), total body adiposity [BMI and percent body fat (percent BF via dual-energy X-ray absorptiometry)], and indexes of abdominal adiposity [waist circumference (WC) and waist-to-hip ratio (WHR)]. In a subgroup (n = 74), we also measured total abdominal fat (TAF), abdominal visceral fat (AVF), and subcutaneous fat (ASF) using computed tomography. Based on multiple linear regression, NID was negatively related to BMI [part correlation coefficient (r(part)) = -0.19, P = 0.004] and abdominal adiposity (WC, r(part) = -0.22; WHR, r(part) = -0.19; TAF, r(part) = -0.36; AVF, r(part) = -0.36; and ASF, r(part) = -0.30; all P ≤ 0.009) independent of sex, but only tended to be related to total percent BF (r(part) = -0.12, P = 0.07). In a subgroup of subjects with the highest compared with the lowest amount of AVF, NID was 35% lower (P = 0.003). Accounting for systolic blood pressure, HDL cholesterol, glucose, insulin resistance, adiponectin, and brachial artery diameter reduced or abolished some of the relations between NID and adiposity. In conclusion, NID is or tends to be negatively associated with measures of total adiposity (BMI and percent BF, respectively) but is consistently and more strongly negatively associated with abdominal adiposity. Adiposity may influence NID in part via other cardiovascular risk factors.

The emerging challenge in diabetes: the "metabolic memory"

Large randomized studies have established that early intensive glycemic control reduces the risk of diabetic complications, both micro and macrovascular. However, epidemiological and prospective data support a long-term influence of early metabolic control on clinical outcomes. This phenomenon has recently been defined as "metabolic memory." Potential mechanisms for propagating this "memory" may be the production of reactive species unrelated to the presence of hyperglycemia, depending on the previous production of AGEs which can maintain RAGE over-expression, on the level of glycation of mitochondrial proteins and on the amount of mtDNA produced, all conditions able to induce an altered gene expression which may be persistent even when glycemia is normalized. Clinically, the emergence of this "metabolic memory" suggests the need for a very early aggressive treatment aiming to "normalize" the metabolic control and the addition of agents which reduce cellular reactive species and glycation in addition to normalizing glucose levels in diabetic patients in order to minimize long-term diabetic complications.

Impaired flow-mediated dilatation response in uncomplicated Type 1 diabetes mellitus: influence of shear stress and microvascular reactivity

Impaired FMD (flow-mediated dilatation) has traditionally been recognized as an indirect marker of NO bioactivity, occurring in disease states such as DM (diabetes mellitus). Endothelium-dependent FMD is a homoeostatic response to short-term increases in local shear stress. Microvascular dysfunction in DM influences blood flow velocity patterns. We explored the determinants of the FMD response in relation to evoked DSS (diastolic shear stress) and forearm microcirculation haemodynamics by quantifying changes in Doppler flow velocity waveforms between groups. Forty patients with uncomplicated Type 1 DM and 32 controls underwent B-mode and Doppler ultrasound scanning to interrogate the brachial artery. Postischaemic Doppler velocity spectral envelopes were recorded and a wavelet-based time-frequency spectral analysis method was employed to track change in distal microcirculatory haemodynamics. No difference in baseline brachial artery diameter was evident between the groups (4.15 compared with 3.94 mm, P=0.23). FMD was significantly impaired in patients with Type 1 DM (3.95 compared with 7.75%, P<0.001). Endothelium-independent dilatation in response to GTN (glyceryl trinitrate) was also significantly impaired (12.07 compared with 18.77%, P<0.001). DSS (dyn/cm2) was significantly reduced in the patient group (mean 20.19 compared with 29.5, P=0.001). Wavelet interrogation of postischaemic flow velocity waveforms identified significant differences between groups. In conclusion, DSS, microcirculatory function and endothelium-independent vasodilatation in response to GTN are important determinants that impact on the magnitude of FMD response and are impaired in patients with Type 1 DM. Impaired FMD response is multifactorial in origin and cannot be attributed solely to a diminished NO bioavailability.

Alterations in arterial pressure in patients with Type 1 diabetes are associated with long-term poor metabolic control and a more atherogenic lipid profile

AIM

To determine the prevalence of alterations in blood pressure (BP) in patients with Type 1 diabetes who are normoalbuminuric and normotensive; and to evaluate the association with genetic, clinical and metabolic factors. MATERIAL/ METHODS: Normoalbuminuric, normotensive Type 1 diabetic patients (no.=85) had their ambulatory blood pressure monitoring (ABPM) performed over 24 h, together with measurement of HbA1c and lipid profile, polymorphisms of the ACE gene, non-midriatic retinography, and the "historical HbA1c" calculated (mean of all the determinations available on the patient).

RESULTS

Of the 85 patients, a mean of 18.8% had pathologic values of BP over the 24 h, 31.8% during active periods and 22.4% during rest periods; in 42% there was a non-dipper pattern in BP. The patients with alterations of BP had higher body mass index (BMI), higher levels of glycemia and of triglycerides, and decreased levels of HDL cholesterol. The "historical HbA1c" was significantly higher in the patients with the non-dipper pattern (8.6 ± 1.4% vs 7.9 ± 1.4%; p=0.046). Pulse pressure was directly associated with male gender (p=0.006) and with BMI (p=0.001). No differences were detected in the distribution of the polymorphisms of the ACE gene as a function of the BP alterations.

CONCLUSIONS

An elevated number normoalbuminuric, normotensive, Type 1 diabetic patients have alterations in BP detected with ABPM over 24 h, and these are associated with a greater BMI, poor long-term metabolic control and a more atherogenic lipid profile.

Coronary vasoreactivity is not altered in young people with type 1 diabetes

BACKGROUND AND AIM

Abnormal coronary microvascular circulation has been demonstrated in diabetes and is associated with increased rate of cardiovascular events. Our objective was to evaluate coronary vasoreactivity in young people with type 1 diabetes with and without microvascular complications.

METHODS AND RESULTS

Twenty-five type 1 diabetic patients without microvascular complications (DC-), 23 with microvascular complications (DC+), and 18 control subjects (C) were studied. Coronary vasoreactivity was assessed by means of coronary flow reserve (CFR). Blood flow velocity in the left anterior descending coronary artery was measured at rest and after high-dose dipyridamole using transthoracic color-guided pulsed Doppler echocardiography. CFR was defined as the ratio of hyperaemic to resting diastolic peak flow velocities. The three groups had similar cardiac function parameters, and also systolic and diastolic blood pressure at rest, which remained unchanged during dipyridamole infusion. Resting coronary flow velocity was comparable in C, DC-, and DC+ (p=ns). Dipyridamole infusion produced a threefold increase in coronary diastolic peak velocity, which reached similar values in C (0.69±0.16 m/s), DC- (0.69±0.18 m/s), and DC+ (0.66±0.11 m/s). Mean CFR ratio was similar in C (3.33±0.66), DC- (3.30±0.51), and DC+ (3.24±0.60). At multiple linear regression analysis, no association was found between CFR and age, sex, HbA(1c), duration of diabetes, and complications.

CONCLUSION

Coronary vasodilatory function is preserved in young D patients, even those with early microvascular complications, suggesting that coronary vasoreactivity deteriorates at more advanced stages of microvascular complications and/or in the presence of other cardiovascular risk factors.

Effects of a short-term improvement in glycaemic control on skin microvascular dysfunction in Type 1 and Type 2 diabetic patients

AIMS

To investigate whether Type 1 and Type 2 diabetic patients differ in the effects of short-term improvement in glycaemic control on skin microvascular dysfunction.

METHODS

Fourteen Type 1 and 14 Type 2 diabetic patients admitted to hospital to improve glycaemic control were investigated. Two age- and sex-matched groups of non-diabetic subjects served as controls. Capillary blood cell velocity (CBV) was assessed at the dorsal middle phalangeal area of the ring finger at rest and after 3-min arterial occlusion using laser Doppler anemometry.

RESULTS

Comparing the measurements before and after improvement in glycaemic control, there were no significant changes in peak CBV, time to peak CBV and vasomotion amplitudes in Type 1 and Type 2 diabetic patients. On admission to hospital, time to peak CBV was prolonged in Type 1 (20.9 +/- 2.9 vs. 12.3 +/- 1.6 s, P = 0.003) and Type 2 diabetic patients (20.6 +/- 2.6 vs. 11.9 +/- 1.3 s, P = 0.021) compared with control subjects. After improvement in glycaemic control, there was no significant difference in time to peak CBV between Type 1 diabetic patients and their control subjects (17.8 +/- 4.2 vs. 12.3 +/- 1.6 s, P = 0.535). In Type 2 diabetic patients, the time to peak CBV increased non-significantly.

CONCLUSIONS

Short-term improvement in glycaemic control did not appear to reverse microcirculatory dysfunction in Type 1 and Type 2 diabetes. However, there was an improvement of the delayed reactive hyperaemia in Type 1 diabetic patients.

Hypothyroidism is associated with signs of endothelial dysfunction despite 1-year replacement therapy with levothyroxine

OBJECTIVE

Hypothyroidism is associated with elevated cardiovascular risk, not fully explained by classical risk factors. Instead, endothelial dysfunction may link hypothyroidism to atherosclerosis. The effect of levothyroxine substitution on endothelial function has been sparsely studied and the results are unclear. This study tested endothelial function as estimated by concomitant measurements of endothelial dependent vascular dilatory capacity and plasma concentration of von Willebrand factor antigen in patients with hypothyroidism and further examined the impact of subsequent levothyroxine substitution.

DESIGN AND PATIENTS

Sixteen consecutive patients (13 women, 3 men, aged 46 +/- 11 years) with hypothyroidism were included and compared to 16 matched healthy controls (13 women, 3 men, aged 49 +/- 11 years). Patients with hypothyroidism were reexamined after 3, 6 and 12 months of levothyroxine substitution.

MEASUREMENTS

Dilatory responses of the brachial artery to post-ischaemic increased blood flow (endothelium-dependent flow-associated dilatation) and to nitroglycerin (endothelium-independent nitroglycerin induced dilatation) were measured by ultrasound. Plasma concentrations of von Willebrand factor antigen were measured by ELISA.

RESULTS

Flow-associated dilatation was impaired in patients with hypothyroidism as compared to controls (102.7 +/- 3.6 vs. 105.6 +/- 3.8%, P = 0.04) whereas no differences in plasma concentration of von Willebrand factor antigen were found. One year levothyroxine substitution did not improve flow-associated dilatation and was associated with an increase of the plasma von Willebrand factor antigen concentration.

CONCLUSIONS

Hypothyroid patients are characterized by endothelial dysfunction sustained despite long-term levothyroxine substitution and potentially increasing the risk of atherosclerosis. Different estimates of endothelial dysfunction seem unequally influenced by hypothyroidism.

Effect of interactions between C peptide levels and insulin treatment on clinical outcomes among patients with type 2 diabetes mellitus

BACKGROUND

A recently halted clinical trial showed that intensive treatment of type 2 diabetes mellitus was associated with increased mortality. Given the phenotypic heterogeneity of diabetes, therapy targeted at insulin status may maximize benefits and minimize harm.

METHODS

In this longitudinal cohort study, we followed 503 patients with type 2 diabetes who were free of cardiovascular disease from 1996 until data on mortality and cardiovascular outcomes were censored in 2005. Phenotype-targeted therapy was defined as use of insulin therapy in patients with a fasting plasma C peptide level of 0.2 nmol/L or less and no insulin therapy in patients with higher C peptide levels.

RESULTS

The mean age of the cohort was 54.4 (standard deviation 13.1) years, and 56% were women. The mean duration of diabetes was 4.6 years (range 0-35.9 years). Of the 503 patients, 110 (21.9%) had a low C peptide level and 111 (22.1%) were given insulin. Based on their C peptide status, 338 patients (67.2%) received phenotype-targeted therapy (non-insulin-treated, high C peptide level [n = 310] or insulin-treated, low C peptide level [n = 28]), and 165 patients (32.8%) received non-phenotype-targeted therapy (non-insulin-treated, low C peptide level [n = 82] or insulin-treated, high C peptide level [n = 83]). Compared with the insulin-treated, low-C-peptide referent group, the insulin-treated, high-C-peptide group was at a significantly higher risk of cardiovascular events (hazard ratio [HR] 2.85, p = 0.049) and death (HR 3.43, p = 0.043); the risk was not significantly higher in the other 2 groups. These differences were no longer significant after adjusting for age, sex and diabetes duration.

INTERPRETATION

Patients with low C peptide levels who received insulin had the best clinical outcomes. Patients with normal to high C peptide levels who received insulin had the worst clinical outcomes. The results suggest that phenotype-targeted insulin therapy may be important in treating diabetes.

[Endothelial dysfunction in type 1 diabetes]

Vascular complications are the main cause of mortality and morbidity in diabetes. Mechanisms involved in the development of micro and macrovascular disease are complex and partially understood, but invariably begin as a dysfunctional endothelium. Nitric oxide is an important regulator of endothelial function and the impairment of its activity is determinant of the endothelial dysfunction. In type 1 diabetes, many factors like acute, chronic and post-prandial hyperglycemia, as well as the duration of diabetes or autonomic neuropathy and microalbuminuria are associated to endothelial dysfunction. Oxidative stress, polyol pathway activation, protein kinase C activation and the presence of advanced glycation end-products are potential mechanisms involved in the development of endothelial dysfunction. Early detection of endothelial dysfunction has prognostic value for the development of vascular complications and may be important in strategies for primary prevention of cardiovascular endpoints in type 1 diabetes.

Long-term hyperglycaemia impairs vascular smooth muscle cell function in women with type 1 diabetes mellitus

Observations of increased stiffness in the elastic aorta in women with diabetes, but not men, emphasise the need for further analysis regarding early abnormalities in arterial wall properties of women with type 1 diabetes mellitus (DM). Ultrasound was used to study the wall properties of the distal brachial artery (BA) in 37 type 1 diabetic women (aged 22-45 years) without evident complications and in 53 controls (C). Blood samples were drawn for later analysis. Flow-mediated dilatation (FMD) was slightly lower in DM than C, 8.1+/-4.3% vs. 10.3+/-4.9% (p<0.05), and nitrate-mediated dilatation (NMD) was markedly lower, 21.7+/-6.6% vs. 31.4+/-5.7% (p<0.001). Lumen diameter, intima-media thickness and distensibility were similar in DM and C. Insulin-like growth factor (IGF-1) was lower in DM than C, 231+/-65 vs. 349+/-68 ng/ml (p<0.001). Glycosylated haemoglobin (HbA1C) and matrix metalloproteinase (MMP-9) were independent predictors of the reduced NMD in the DM. Brachial artery responsiveness to an exogenous donor of nitric oxide (NO) was markedly reduced in type 1 diabetic women despite only limited reduction in endothelium-dependent dilatation. The negative association between NMD and HbA1C suggests that long-term hyperglycaemia impairs vascular smooth muscle cell function in DM.

Impaired collateral recruitment and outward remodeling in experimental diabetes

OBJECTIVE

In this study, the effect of chronic hyperglycemia on acute ligation-induced collateral vasodilation, on monocyte chemotaxis, and on structural outward remodeling of collaterals was investigated.

RESEARCH DESIGN AND METHODS

Femoral artery ligation was performed 8 weeks after alloxan or saline treatment in New Zealand White rabbits. Angiography was performed directly, 1 and 3 weeks after ligation. These angiographic recordings were used to quantify number of collaterals, lumen, and blood volume index. Reactive hyperemia response was tested by intramuscular laser Doppler measurements. Subsequently, blood was sampled from the aorta for monocyte chemotaxis.

RESULTS

Ligation resulted in markedly lower acute collateral vasodilation in diabetic compared with control rabbits. Also, hyperemic vasodilatory response to local ischemia was impaired in diabetic rabbits. This difference persisted at 1 and 3 weeks after ligation, with a lower number of visible collaterals. In addition, the collateral lumen was markedly lower in diabetic rabbits after the maturation phase. Likewise, a reduced blood volume index in the region of growing collaterals was observed in diabetic animals. The monocyte migration toward vascular endothelial growth factor-A and monocyte chemotactic protein-1 was strongly reduced in diabetic rabbits.

CONCLUSIONS

This study demonstrates that chronic hyperglycemia negatively affects the different phases of arteriogenesis: 1) impaired shear induced vasodilatation; 2) impaired outward collateral growth, reflected in the number of collaterals and blood volume index; and 3) inhibition of monocyte chemotaxis. Impairments were most evident in the acute phase of arteriogenesis. Therapies aimed at restoring acute collateral recruitment, such as vasodilators, may be of interest to improve collateral function in diabetes.

Arterial hypertension determined by ambulatory blood pressure profiles: contribution to microalbuminuria risk in a multicenter investigation in 2,105 children and adolescents with type 1 diabetes

OBJECTIVE

Arterial hypertension is a key player in the development of diabetes complications. We used a nationwide database to study risk factors for abnormal 24-h blood pressure regulation and microalbuminuria in children and adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Ambulatory blood pressure monitoring was performed in 2,105 children and adolescents from 195 pediatric diabetes centers in Germany and Austria. Individual least median squares (LMS)-SD scores were calculated for diurnal and nocturnal systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressure according to normalized values of a reference population of 949 healthy German children. The nocturnal blood pressure reduction (dipping) was calculated for SBP as well as DBP.

RESULTS

In diabetic children, nocturnal blood pressure in particular was significantly elevated (SBP +0.51, DBP +0.58, MAP +0.80 LMS-SD) and dipping of SBP DBP, and MAP was significantly reduced (P < 0.0001). Age, diabetes duration, sex BMI, A1C, and insulin dose were related to altered blood pressure profiles; dipping, however, was only affected by age, female sex, and A1C. The presence of microalbuminuria was associated with nocturnal DBP (P < 0.0001) and diastolic dipping (P < 0.01).

CONCLUSIONS

Our observations revealed a clear link between the quality of metabolic control and altered blood pressure regulation even in pediatric patients with short diabetes duration. Nocturnal blood pressure in particular seems to mainly contribute to diabetes complications such as microalbuminuria.

Contribution of polyol pathway to arteriolar dysfunction in hyperglycemia. Role of oxidative stress, reduced NO, and enhanced PGH(2)/TXA(2) mediation

Hyperglycemia increases glucose metabolism via the polyol pathway, which results in elevations of intracellular sorbitol concentration. Thus we hypothesized that elevated level of sorbitol contributes to the development of hyperglycemia-induced dysfunction of microvessels. In isolated, pressurized (80 mmHg) rat gracilis muscle arterioles (approximately 150 microm), high glucose treatment (25 mM) induced reduction in flow-dependent dilation (from maximum of 39 +/- 2% to 15 +/- 1%), which was significantly mitigated by an aldose reductase inhibitor, zopolrestat (maximum 27 +/- 2%). Increasing doses of sorbitol (10(-10)-10(-4) M) elicited dose-dependent constrictions (maximum 22 +/- 3%), which were abolished by endothelium removal, a prostaglandin H(2)/thromboxane A(2) (PGH(2)/TXA(2)) receptor (TP) antagonist SQ-29548, or superoxide dismutase (SOD) plus catalase (CAT). Incubation of arterioles with sorbitol (10(-7) M) reduced flow-dependent dilations (from maximum of 39 +/- 2% to 20 +/- 1.5%), which was not further affected by inhibition of nitric oxide synthase by N(omega)-nitro-l-arginine methyl ester but was prevented by SOD plus CAT and mitigated by SQ-29548. Nitric oxide donor sodium nitroprusside-induced (10(-9)-10(-6) M) dilations were also decreased in a SQ-29548 and SOD plus CAT-reversible manner, whereas adenosine dilations were not affected by sorbitol exposure. Sorbitol significantly increased arterial superoxide production detected by lucigenin-enhanced chemiluminescence, which was inhibited by SOD plus CAT. Sorbitol treatment also increased arterial formation of 3-nitrotyrosine. We suggest that hyperglycemia by elevating intracellular sorbitol induces oxidative stress, which interferes with nitric oxide bioavailability and promotes PGH(2)/TXA(2) release, both of which affect regulation of vasomotor responses of arterioles. Thus increased activity of the polyol pathway may contribute to the development of microvascular dysfunction in diabetes mellitus.

Telmisartan shows an equivalent effect of vitamin C in further improving endothelial dysfunction after glycemia normalization in type 1 diabetes

OBJECTIVE

Long-lasting hyperglycemia in type 1 diabetic patients induces permanent alterations of endothelial function by increased oxidative stress, even when glycemia is normalized.

RESEARCH DESIGN AND METHODS

In this study, 36 type 1 diabetic patients and 12 control subjects were enrolled. The diabetic patients were divided into three groups. The first group was treated for 24 h with insulin, achieving a near normalization of glycemia. After 12 h of this treatment, vitamin C was added for the remaining 12 h. The second group was treated for 24 h with vitamin C. After 12 h of this treatment, insulin was started, achieving a near normalization of glycemia for the remaining 12 h. The third group was treated for 24 h with both vitamin C and insulin, achieving near normalization of glycemia. The same protocols were performed after 1 month of telmisartan or placebo.

RESULTS

Neither normalization of glycemia nor vitamin C treatment alone was able to normalize endothelial dysfunction or oxidative stress. Combining insulin and vitamin C normalized endothelial dysfunction and decreased oxidative stress to normal levels. Telmisartan significantly improved basal endothelial function and decreased nitrotyrosine plasma levels. In patients treated with telmisartan, a near normalization of both flow-mediated vasodilation and oxidative stress was achieved when glycemia was normalized, whereas adding vitamin C infusion did not show further effect on endothelial function or nitrotyrosine plasma levels.

CONCLUSIONS

These data indicate that combining the normalization of glycemia with an antioxidant can normalize endothelial function in type 1 diabetic patients and that telmisartan works as an antioxidant like vitamin C.

Circulating vascular endothelial growth factor is unaffected by acute hyperglycemia and hyperinsulinemia in type 1 diabetes mellitus

BACKGROUND

Circulating levels of vascular endothelial growth factor (VEGF) may predict microvascular complications in type 1 diabetes mellitus and are elevated when metabolic control is poor. We tested whether serum VEGF is influenced by prevailing glucose and insulin levels.

METHODS

In 15 type 1 diabetic patients, serum VEGF, plasma von Willebrand factor antigen (vWF-Ag), and serum soluble intercellular adhesion molecule-1 (s-ICAM) levels were measured after 210 min of hyperglycemia (blood glucose target 12.0 mmol/l) and hyperinsulinemia (insulin infused at 120 mU/kg/h), alone and in combination. These were then compared with the levels obtained at the end of a 210-min normoglycemic (blood glucose target 5.0 mmol/l) standard insulin clamp (insulin infused at 30 mU/kg/h).

RESULTS

VEGF (p>0.60) as well as vWF-AG (p>0.80) and s-ICAM (p>0.20) remained unchanged at the end of the three intervention periods.

CONCLUSION

These findings suggest that no special precautions, in terms of concurrent measurement of glucose or timing of insulin administration, are necessary when interpreting circulating VEGF in this patient category.

Possible association between diabetes and bisphosphonate-related jaw osteonecrosis

CONTEXT

Bisphosphonate-related osteonecrosis (BON) of the jaws is a newly identified condition for which the exact mechanism involved in its pathogenesis remains obscure.

OBJECTIVE

The objective of the study was to evaluate whether diabetes mellitus (DM) may be a contributing factor in the development of BON.

DESIGN

From 2004 to 2006, 31 patients were diagnosed with BON. The diagnosis of BON was based on the medical and dental history of each patient as well as the observation of clinical signs and symptoms of this pathological process. DM was based on two consecutive fasting blood glucose levels above 7 mmol/liter.

SETTING

The study was completed in the Hebrew University-Hadassah Hospital referral center.

RESULTS

Of the 31 patients with BON, 18 (58%) were found to have DM or impaired fasting glucose. The proportion of diabetic patients was much higher than expected relative to the incidence of DM in the general population (14%) and compared with the proportion of diabetic patients in a control group of oncological patients treated with bisphosphonates and without BON (12%) (P = 0.00003).

CONCLUSIONS

This finding indicates that DM may be a risk factor for BON and that DM patients treated with bisphosphonates should be carefully monitored. We discuss here the bone metabolic pathways characteristic of DM patients and the way in which these pathways can augment the effects of bisphosphonates.

Simultaneous control of hyperglycemia and oxidative stress normalizes endothelial function in type 1 diabetes

OBJECTIVE

Previous studies have shown that in type 1 diabetes endothelial dysfunction persists even when glycemia is normalized. Moreover, oxidative stress has recently been demonstrated to be the mediator of hyperglycemia-induced endothelial dysfunction.

RESEARCH DESIGN AND METHODS

Thirty-six type 1 diabetic patients and 12 control subjects were enrolled. The diabetic patients were divided into three groups. The first group was treated for 24 h with insulin, achieving a near-normalization of glycemia. After 12 h of this treatment, vitamin C was added for the remaining 12 h. The second group was treated for 24 h with vitamin C. After 12 h of this treatment, insulin was started, with achievement of near-normalization of glycemia for the remaining 12 h. The third group was treated for 24 h with both vitamin C and insulin, achieving near-normalization of glycemia.

RESULTS

Neither normalization of glycemia nor vitamin C treatment alone was able to normalize endothelial dysfunction or oxidative stress. However, a combination of insulin and vitamin C normalized endothelial dysfunction and decreased oxidative stress to normal levels.

CONCLUSIONS

This study suggests that long-lasting hyperglycemia in type 1 diabetic patients induces permanent alterations in endothelial cells, which may contribute to endothelial dysfunction by increased oxidative stress even when hyperglycemia is normalized.

Concanavalin A, but not glycated albumin, increases subendothelial deposition of von Willebrand factor in vitro

Diabetes is associated with augmentation of prothrombogenic von Willebrand factor (vWF) content in plasma. Earlier, the author and colleagues have shown that high glucose and insulin do not appreciably influence deposition of vWF into the subendothelial extracellular matrix (SECM) produced by cultured human umbilical vein endothelial cells (HUVECs). In the present work, the author used this model to test the effects of nonenzymatically glycated albumin (Glyc-HSA) and two lectins, concanavalin A (ConA) and wheat germ agglutinin (WGA), on vWF deposition into the SECM. First-passage HUVECs were seeded into gelatin-coated 96-well plates and cultured for 6 to 7 days. HSA or Glyc-HSA (at concentrations 25, 50, and 100 microg/mL), and WGA or ConA (4, 8, and 16 microg/mL) were added 3 h after seeding. Cell viability was tested by the MTT method. To determine vWF contents in the SECM, HUVECs were detached by treatment with NH4OH and the residual material was used as a solid phase in an enzyme-linked immunosorbent assay (ELISA)-like assay with primary (anti-vWF) and secondary (peroxidase-conjugated) antibodies. Addition of Glyc-HSA did not essentially influence VWF contents in the SECM (A490 was 0.226 versus 0.268 at 0 and 100 microg/mL, respectively; p > .05, n = 16). Cultivation in the presence of WGA led to the deterioration of cell viability, which was accompanied by a significant decrease of vWF in the SECM (0.248 versus 0.128 at 0 and 16 microg/mL, respectively; p < .001, n = 16). ConA did not influence viability of HUVECs, but this lectin at all concentrations consistently increased the deposition of vWF (up to 164% relative to control, p <.001; n = 16). These data indicate that endothelial carbohydrate determinants and corresponding ligands (namely, mannose-specific lectins) may be involved in the regulation of production and deposition of vWF.

Reciprocal relationships between abnormal metabolic parameters and endothelial dysfunction

PURPOSE OF REVIEW

Endothelial dysfunction plays a crucial role in the pathogenesis of atherosclerosis and related cardiovascular diseases. Glucotoxicity, lipotoxicity, and inflammation all independently contribute to development of both endothelial dysfunction and insulin resistance. We review pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance and recent insights from therapeutic interventions to improve both metabolic and vascular function.

RECENT FINDINGS

Shared causal factors such as glucotoxicity, lipotoxicity, and inflammation interact at multiple levels creating reciprocal relationships between insulin resistance and endothelial dysfunction that help to explain frequent clustering of metabolic and cardiovascular disorders. Metabolic abnormalities implicated in the development of insulin resistance, including hyperglycemia, elevated levels of free fatty acids, accumulation of advanced glycation end products, dyslipidemias, and decreased levels of adiponectin, also contribute importantly to endothelial dysfunction. Diet, exercise, cardiovascular drugs, and insulin sensitizers simultaneously improve endothelium-dependent vascular function, reduce inflammation, and improve insulin sensitivity by both distinct and interrelated mechanisms.

SUMMARY

Pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance contribute to clustering of metabolic and cardiovascular diseases represented by the metabolic syndrome. Therapeutic interventions that target endothelial dysfunction or insulin resistance often simultaneously improve both metabolic and vascular function.

Flow-associated dilatory capacity of the brachial artery is intact in early autosomal dominant polycystic kidney disease

BACKGROUND/AIMS

Autosomal dominant polycystic kidney disease is associated with endothelial dysfunction of resistance arteries. This study tested whether endothelial dysfunction is also present in the conduit arteries in patients with preserved renal function.

METHODS

Twenty-seven patients (9 females and 18 males, age 36 +/- 10 years) with polycystic kidney disease and normal renal function were compared to 27 healthy controls. The dilatory responses of the brachial artery to postischemic increased blood flow [endothelium-dependent flow-associated dilatation (FAD)] and to nitroglycerin [endothelium-independent nitroglycerin-induced dilatation (NID)] were measured by external ultrasound. Plasma concentrations of the stable end products of nitric oxide nitrate/nitrite (NOx) and of the endothelial markers vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1, E-selectin and von Willebrand factor antigen were also measured.

RESULTS

No differences in FAD or NID were found between patients and controls (104.6 +/- 4.2 vs. 105.3 +/- 3.9%, mean +/- SD, p = 0.55, and 117.0 +/- 8.4 vs. 117.5 +/- 7.6%, p = 0.75). However, the plasma concentration of VCAM-1 was elevated and the plasma concentration of NOx was reduced in patients with polycystic kidney disease.

CONCLUSION

Biochemical markers confirm an association between polycystic kidney disease and endothelial dysfunction. However, a normal FAD of the brachial artery suggests that the endothelial dysfunction does not involve the conduit arteries.