Comparison of laser-Doppler flowmetry with biochemical indicators of endothelial dysfunction related to early microangiopathy in Type 1 diabetic patients

Electronic Cigarette Vaping with Nicotine Causes Increased Thrombogenicity and Impaired Microvascular Function in Healthy Volunteers: A Randomised Clinical Trial

Electronic cigarette (EC) vaping is increasingly popular, despite growing evidence of adverse health effects. To further evaluate the impact of EC use on vascular health, we investigated the effects of brief EC inhalation on flow-dependent thrombus formation and microcirculation in healthy volunteers. The study was performed with a randomised double-blind crossover design. Twenty-two healthy subjects aged between 18 and 45 years with occasional tobacco use were recruited. Subjects inhaled 30 puffs of EC aerosol with and without nicotine on two occasions separated by a wash-out period of at least 1 week. Blood samples were collected at baseline and at 15 and 60 min following exposure and analysed with the Total-Thrombus-formation analysis system evaluating fibrin-rich thrombus formation and platelet thrombus formation in whole blood under flow. Microvascular function was assessed at baseline and 30 min after exposure by laser speckle contrast imaging and iontophoresis of acetylcholine and sodium nitroprusside (SNP) to evaluate the endothelium-dependent and independent pathways of vasodilation. Compared with nicotine free EC aerosol, exposure to EC aerosol with nicotine significantly increased platelet thrombus formation and fibrin-rich thrombus formation at 15 min (p = 0.017 and p = 0.037, respectively) with normalisation after 60 min. Peak SNP-mediated microvascular perfusion, i.e. endothelium-independent vasodilation, was reduced following EC vaping with nicotine compared with baseline (p = 0.006). Thirty puffs of EC aerosol with nicotine increased platelet and fibrin-dependent thrombus formation and reduced microvascular dilatation capacity. No compelling effects of EC vaping without nicotine were observed, indicating nicotine as the main effector. Trial registration: ClinicalTrials.gov Identifier: NCT04175457 URL: https://clinicaltrials.gov/ct2/show/NCT04175457.

The Histamine-Induced Axon-Reflex Response in People With Type 1 Diabetes With and Without Peripheral Neuropathy and Pain: A Clinical, Observational Study

Small nerve fibres are important when studying diabetic peripheral neuropathy (DPN) as they could be first affected. However, assessing their integrity and function adequately remains a major challenge. The aim of this study was to investigate the association between different degrees of DPN, the presence of neuropathic pain, and the intensity of the axon-reflex flare response provoked by epidermal histamine. Eighty adults were included and divided into 4 groups of 20 with type 1 diabetes and: painful DPN (T1DM+PDPN), non-painful DPN (T1DM+DPN), no DPN and no pain (T1DM-DPN), and 20 persons without diabetes or pain (HC). The vasomotor responses were captured by a Full-field Laser Speckle Perfusion Imager. The response was lowest in T1DM+DPN, followed by T1DM+PDPN, T1DM-DPN and HC. The response was significantly reduced in DPN (T1DM+DPN, T1DM+PDPN) compared with people without (T1DM-DPN, HC) (P < .001). The response was also attenuated in diabetes irrespective of the degree of DPN (T1DM+PDPN, T1DM+DPN, T1DM-DPN) (P < .001). There were no differences in the response between painful neuropathy (T1DM+PDPN) and painless DPN (T1DM+DPN) (P = .189). The method can distinguish between groups with and without diabetes and with and without DPN but cannot distinguish between groups with and without painful DPN. PERSPECTIVE: This study describes how diabetes attenuates the axon-reflex response, and how it is affected by neuropathy and pain clarifying previous findings. Furthermore, the study is the first to utilize histamine when evoking the response, thus providing a new and fast alternative for future studies into the pathophysiology of neuropathic pain.

Skin autofluorescence corresponds to microvascular reactivity in diabetes mellitus

Advanced glycation accelerated by chronic hyperglycaemia contributes to the development of diabetic vascular complications throughout several mechanisms. One of these mechanisms is supposed to be impaired microvascular reactivity, that precedes significant vascular changes. The aim of this study was to find an association between advanced glycation, the soluble receptor for AGEs (sRAGE), and microvascular reactivity (MVR) in diabetes. Skin autofluorescence (SAF), which reflects advanced glycation, was assessed by AGE-Reader, MVR was measured by laser Doppler fluxmetry and evaluated together with sRAGE in 43 patients with diabetes (25 Type 1 and 18 Type 2) and 26 healthy controls of comparable age. SAF was significantly higher in patients with diabetes compared to controls (2.4 ± 0.5 vs. 2.0 ± 0.5 AU; p < 0.01). Patients with diabetes with SAF > 2.3 AU presented significantly worse MVR in both post-occlusive reactive hyperaemia (PORH) on the finger and forearm, and thermal hyperaemia (TH), compared to patients with SAF < 2.3 AU. SAF was age dependent in both diabetes (r = 0.41, p < 0.01) and controls (r = 0.45, p < 0.05). There was no association between SAF and diabetes control expressed by glycated haemoglobin. A significant relationship was observed between SAF and sRAGE in diabetes (r = 0.56, p < 0.001), but not in controls. A significant inverse association was found between SAF and MVR on the forearm in diabetes (PORH: r = -0.42, p < 0.01; TH: r = -0.46, p < 0.005). Both advanced glycation expressed by higher SAF or sRAGE and impaired MVR are involved in the pathogenesis of vascular complications in diabetes, and we confirm a strong interplay of these processes in this scenario.

Reactivity of skin microcirculation as a biomarker of cardiovascular events. Pilot study

BACKGROUND

The role of microcirculatory disorders is progressively being accepted in the pathogenesis of cardiovascular diseases.

OBJECTIVE

The purpose of current study is to assess whether we can consider skin microcirculation disorders as a biomarker of cardiovascular events.

METHODS

Group 1 consisted of healthy volunteers (n = 31); group 2 (n = 42) consisted of patients with diseases that increase the risk of cardiovascular events; group 3 (n = 39) included patients with the history of cardiovascular events. Skin microcirculation measurement was performed using laser Doppler flowmetry during the heating test.

RESULTS

LDF parameters reflecting the rapid response of microcirculation to heating ("Slope 120 s" and "Slope 180 s") significantly differed in three groups (p <  0.05). A decrease in the "Slope 180 s" parameter less than 0.5 PU/s is associated with cardiovascular events (sensitivity 69.2%, specificity 66.7%; the area under the ROC curve, 0.667; 95% confidence interval [CI], 0.545-0.788, p = 0.01). Multivariable logistic regression analysis revealed that "Slope 180 s≤0.5 PU/s" was significantly related to cardiovascular events (adjusted odds ratio = 3.9, p = 0.019, CI 95% 1.2-12).

CONCLUSIONS

Reduced reactivity of the skin microcirculation may be useful as a biomarker of severe damage to the cardiovascular system and is promising as a risk factor for cardiovascular events.

Reproducibility and normalization of reactive hyperemia using laser speckle contrast imaging

Background

Impaired perfusion indices signal potential microvascular dysfunction preceding atherosclerosis and other cardiometabolic pathologies. Post-occlusive reactive hyperemia (PORH), a vasodilatory response following a mechanically induced ischemia, is a transient increase in perfusion and can assess microvascular function. The greatest blood flow change corresponding to the first minute of hyperemia (represented by time-to-peak, hyperemic velocity, AUC within 1^st min) has been shown to indicate microvascular dysfunction. However, the reproducibility of these temporal kinetic indices of the PORH response is unknown. Our aim was to examine the inter- and intra-day reproducibility and standardization of reactive hyperemia, with emphasis on the kinetic indices of PORH, using laser speckle contrast imaging (LSCI) technique.

Methods and results

Seventeen healthy adults (age = 24 ± 3 years) completed three PORH bouts over two lab visits. LSCI region of interest was a standardized 10 cm region on the dominant ventral forearm. A 5-min brachial artery occlusion period induced by inflating an arm cuff to 200 mmHg, preceded a 4-min hyperemic period. Inter- and intra-day reliability and reproducibility of cutaneous vascular conductance (LSCI flux / mean arterial pressure) were determined using intraclass correlation (ICC) and coefficient of variation (CV%). Maximal flow and area under the curve standardized to zero perfusion showed intra- and inter-day reliability (ICC > 0.70). Time to maximal flow (TMF) was not reproducible (inter-day CV = 18%). However, alternative kinetic indices such as 1-min AUC and overshoot rate-of-change (ORC), represented as a piecewise function (at 5s, 10s, 15s, and 20s into hyperemia), were reproducible (CV< 11%). Biological zero was a reliable normalization point.

Conclusion

PORH measured with LSCI is a reliable assessment of microvascular function. However, TMF or its derived hyperemic velocity are not recommended for longitudinal assessment. Piecewise ORC and 1-min AUC are reliable alternatives to assess the kinetic response of PORH.

Skin microvascular reactivity correlates to clinical microangiopathy in type 1 diabetes: A pilot study

AIM

The aim of this study was to investigate the correlation between skin microvascular reactivity and clinical microangiopathy in patients with type 1 diabetes.

METHODS

We included 61 patients with type 1 diabetes, that is, 31 patients with and 30 without clinical microangiopathy, and 31 healthy controls. A microangiopathy scoring system was introduced for comparison of data between patients with microangiopathy. Responses to iontophoresis of acetylcholine and sodium nitroprusside were assessed by laser Doppler imaging.

RESULTS

Patients with microangiopathy had reduced acetylcholine- and sodium nitroprusside-mediated flux in forearm skin microcirculation compared to healthy controls (p = 0.03 and p < 0.001, respectively, repeated measures analysis of variance), whereas no significant differences were found between patients without microangiopathy and controls. Skin reactivity was reduced in patients with microangiopathy compared to patients without microangiopathy: 1.43 ± 0.38 versus 1.59 ± 0.39 arbitrary units for acetylcholine-mediated peak flux and 1.44 ± 0.46 versus 1.74 ± 0.34 arbitrary units for sodium nitroprusside-mediated peak flux (p < 0.05 for both). A tendency of gradual decrease in acetylcholine and sodium nitroprusside responses was found in patients with increasing microangiopathy scores.

CONCLUSION

We conclude that skin microvascular reactivity is associated with clinical microangiopathy in patients with type 1 diabetes. Impaired skin microvascular function in type 1 diabetes seems to be multifactorial and involves both endothelial-dependent and endothelial-independent pathways. We introduce a novel microangiopathy score that could easily be used in a clinical setting for comparison of patients with various degrees of microangiopathy.

The relationship between sudomotor function and skin microvascular reactivity in individuals with type 1 diabetes of long duration

AIM

The aim of this study was to assess the relationship between sudomotor function and microvascular perfusion in patients with type 1 diabetes (DM1).

METHODS

We evaluated 415 patients (206 women), with DM1, median age of 41 (IQR: 33-53) years, disease duration of 25 (IQR: 20-32) years. We assessed metabolic control of diabetes and the presence of peripheral and cardiac autonomic neuropathy. Sudomotor function was assessed using Sudoscan device by electrochemical skin conductance (ESC). Microvascular function was measured by laser-Doppler flowmetry with basal perfusion, the peak flow after occlusion (PORHpeak) and THmax which is the percentage change between basal perfusion and the peak flow during thermal hyperemia (TH). The accumulation of advanced glycation end products in the skin was assessed by skin autofluorescence (AF) measurement using AGE Reader. We subdivided patients based on the presence of diabetic peripheral neuropathy (DPN), cardiac autonomic neuropathy (CAN) and according to normal value of ESC.

RESULTS

Patients with abnormal ESC had higher skin AF [2.5 (2.1-2.9) vs 2.1 (1.9-2.5) AU, p < 0.001], lower eGFR [83 (72-96) vs 98 (86-108) ml/min/1.73 m2, p < 0.001], higher basal perfusion [25 (12-81) vs 14 (7-43) PU, p < 0.001], lower THmax [664 (137-1461) vs 1115 (346-1933) %, p = 0.002], higher PORHpeak [104 (59-167) vs 70 (48-135) PU, p < 0.001] as compared to subjects with normal ESC results. We found negative correlation between THmax and TG level (Rs = -0.14, p < 0.005), AF (Rs = -0.19, p = 0.001), vibration perception threshold - VPT (Rs = -0.24, p < 0.001) and positive correlation with HDL level (Rs = 0.14, p = 0.005), Feet ESC (Rs = 0.21, p < 0.001) and Hands ESC (Rs = 0.14, p = 0.004). We found positive correlation between PORHpeak and TG level (Rs = 0.14, p = 0.003), skin AF (Rs = 0.29, p < 0.001), VPT (0.27, p < 0.001) and negative correlation with eGFR (Rs = -0.2, p < 0.001), HDL (Rs = -0.12, p = 0.01), Feet ESC (Rs = -0.27, p < 0.001) and Hand ESC (Rs = -0.16, p = 0.002).

CONCLUSION

Impaired microvascular reactivity is associated with sudomotor dysfunction in patients with type 1 diabetes.

Severe acrocyanosis precipitated by cold agglutinin secondary to infection with Mycoplasma pneumoniae in a pediatric patient

This is the first report describing a severe form of cold agglutinin-induced acrocyanosis with cutaneous necrosis after Mycoplasma infection in a 9-year-old patient without any other severe symptoms and laboratory alterations. We also present the results of two non-invasive methods used to determine the viability of tissues, degree of tissue perfusion impairment, and the responsiveness of the microvasculature. Laser Doppler flowmetry and laser speckle contrast imaging, both suitable to measure tissue blood perfusion non-invasively, have been used in the diagnosis and follow-up of various peripheral vascular diseases. In our patient, we demonstrated remarkably reduced microcirculation before the treatment and a significant perfusion increase in the acral regions after pentoxifylline therapy. The investigational techniques were useful tools to assess and quantify the severity of peripheral perfusion disturbances and to monitor the efficacy of the treatment in our patient.

Impairment of microcirculation and vascular responsiveness in adolescents with primary Raynaud phenomenon

BACKGROUND

Raynaud's phenomenon (RP) is a functional vascular disease, presenting with recurrent episodes of ischemia of extremities in response to cold and emotional stress. Investigating cutaneous microcirculation is an important tool in understanding the complex neuro-immuno-vascular interactions in its pathophysiological mechanisms. Since there is no available data on vascular responsiveness in RP in the paediatric population, we investigated skin perfusion and heat-induced hyperaemia in comparison with clinical severity and laboratory parameters of the disease.

METHODS

Fifty two adolescents (27 patients with primary RP and 25 age-matched healthy controls) were investigated in the study. Patients were divided into two groups according to the symptoms existing within the previous 2 months. Following baseline microcirculation measurement with Laser Doppler flowmetry (Periflux 5000 system), all subjects underwent local heating test at 42 °C and 44 °C. Besides routine laboratory parameters, immune-serological tests and the vasoactive sensory neuropeptides somatostatin and pituitary adenylate-cyclase activating polypeptide (PACAP) were measured.

RESULTS

Baseline perfusion measured in perfusion units (PU) at 32 °C was significantly lower in symptomatic RP patients (97.6 ± 22.4 PU) compared with both healthy volunteers (248.3 ± 23.5 PU, p < 0.001) and RP patients without symptoms (187.4 ± 24.9 PU, p < 0.05). After local heating to 42 °C maximum blood flow was significantly reduced in primary RP participants with current symptoms (358.6 ± 43.9 PU, p < 0.001), but not in asymptomatic ones (482.3 ± 28.7 PU, p > 0.05) when compared with healthy subjects (555.9 ± 28.2 PU). Both the area under the response curve and the latency to reach the maximum flow were significantly increased in both RP groups (symptomatic 164.6 ± 7.4 s, p < 0.001, asymptomatic 236.4 ± 17.4 s, p < 0.001) when compared with the control group (101.9 ± 4.7 s). The heat-induced percentage increase from baseline to maximal blood flow was significantly greater in symptomatic RP adolescents in comparison with healthy ones. Laboratory parameters and neuropeptide plasma levels were not altered in any groups.

CONCLUSION

To our knowledge this is the first study in paediatric population to show altered heat-induced cutaneous hyperaemia responses in relation with the clinical severity and symptomatology.

Pregnancy-associated plasma protein-A is positively correlated with first-trimester skin microvascular reactivity

OBJECTIVE

To investigate the relationship between levels of circulating maternal pregnancy-associated plasma protein-A (PAPP-A) and first-trimester maternal vascular function.

METHODS

This was a cross-sectional study of 53 healthy, non-smoking, nulliparous pregnant women in Stockholm, Sweden. PAPP-A levels and vascular function were assessed during gestational weeks 11-14. Forearm skin microcirculation was investigated by laser Doppler perfusion imaging during iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) to assess endothelium-dependent and -independent microvascular vasodilatation, respectively. Microvascular endothelial function index was calculated as peak ACh/peak SNP. Endothelium-dependent and -independent vasodilatation in the brachial artery was evaluated, respectively, by postischemic hyperemia-induced flow-mediated vasodilatation (FMD) and by response to sublingual intake of glyceryl trinitrate (GTN).

RESULTS

PAPP-A was correlated with skin microvascular endothelial function index (β = 1.008 (95% CI, 0.34-1.68), r²  = 0.17, P = 0.004). PAPP-A also correlated inversely with FMD (β = -0.052 (95% CI, -0.094 to -0.011), r²  = 0.13, P = 0.014) but did not relate to forearm endothelial function index (i.e. FMD/GTN). The results were retained in multivariate analyses including known confounding factors.

CONCLUSIONS

First-trimester endothelium-dependent skin microvascular reactivity was positively related to PAPP-A levels. If confirmed, these novel findings suggest that first-trimester skin microvascular reactivity could be a useful early pregnancy marker of placental function. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Assessment of microvascular endothelial function in type 1 diabetes using laser speckle contrast imaging

OBJECTIVE

To test whether laser speckle contrast imaging (LSCI) coupled with physiological post-occlusive reactive hyperemia (PORH) and pharmacological iontophoresis of acetylcholine (ACh) as local vasodilator stimuli could distinguish between cutaneous microvascular responses of Type 1 Diabetes (T1DM)'s patients with endothelial dysfunction and that of healthy controls.

METHODS

Patients with T1DM aged ≥12years completed a clinical-epidemiological questionnaire. Data detailing patients' such as daily insulin dose, duration of diabetes, and use of pharmaceuticals such as antihypertensive drugs and statins that could interfere with endothelial function were obtained. Vascular reactivity was assessed in the forearm by LSCI and PORH at baseline and during iontophoresis of ACh using increasing anodic currents of 30, 60, 90, 120, 150 and 180μA in 10second intervals.

RESULTS

This study included 50 patients with T1DM and 30 control subjects. The mean resting flux did not differ between patients and control subjects. T1DM patients exhibited endothelial dysfunction upon challenge with physiological or pharmacological stimuli. The microvascular response to both ACh and PORH (i.e., maximum response at peak and amplitude) were significantly reduced in patients with diabetes compared with control subjects (p<0.001).

CONCLUSION

We demonstrated that endothelium-dependent skin microvascular vasodilator responses are significantly impaired in patients with T1DM compared to healthy subjects investigated using LSCI coupled with ACh iontophoresis and PORH. Additionally, we find that LSCI is a promising methodology for studying physiological vascular reactivity in T1DM.

The association between diabetes and dermal microvascular dysfunction non-invasively assessed by laser Doppler with local thermal hyperemia: a systematic review with meta-analysis

Background/Introduction

Diabetes and cardiovascular disease develop in concert with metabolic abnormalities mirroring and causing changes in the vasculature, particularly the microcirculation. The microcirculation can be affected in different parts of the body of which the skin is the most easily accessible tissue.

Purpose

The association between diabetes and dermal microvascular dysfunction has been investigated in observational studies. However, the strength of the association is unknown. Therefore we conducted a systematic review with meta-analysis on the association between diabetes and dermal microvascular dysfunction as assessed by laser Doppler/laser speckle contrast imaging with local thermal hyperaemia as non-invasive indicator of microvascular functionality.

Methods

PubMed and Ovid were  systematically searched for eligible studies through March 2015. During the first selection, studies were included if they were performed in humans and were related to diabetes or glucose metabolism disorders and to dermal microcirculation. During the second step we selected studies based on the measurement technique, measurement location (arm or leg) and the inclusion of a healthy control group. A random effects model was used with the standardised mean difference as outcome measure. Calculations and imputation of data were done according to the Cochrane Handbook.

Results

Of the 1445 studies found in the first search, thirteen cross-sectional studies were included in the meta-analysis, comprising a total of 857 subjects. Resting blood flow was similar between healthy control subjects and diabetes patients. In contrast, the microvascular response to local skin heating was reduced in diabetic patients compared to healthy control subjects [pooled effect of −0.78 standardised mean difference (95% CI −1.06, −0.51)]. This effect is considered large according to Cohen’s effect size definition. The variability in effect size was high (heterogeneity 69%, p < 0.0001). However, subgroup analysis revealed no difference between the type and duration of diabetes and other health related factors, indicating that diabetes per se causes the microvascular dysfunction.

Conclusion

Our meta-analysis shows that diabetes is associated with a large reduction of dermal microvascular function in diabetic patients. The local thermal hyperaemia methodology may become a valuable non-invasive tool for diagnosis and assessing progress of diabetes-related microvascular complications, but standardisation of the technique and quality of study conduct is urgently required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0487-1) contains supplementary material, which is available to authorized users.

Impairments in local heat loss in type 1 diabetes during exercise in the heat

Studies show that vasomotor and sudomotor activities are compromised in individuals with Type 1 diabetes mellitus (T1DM), which could lead to impaired skin blood flow (SkBF) and sweating during heat stress. However, recent work suggests the impairments may only be evidenced beyond a certain level of heat stress.

PURPOSE

We examined T1DM-related differences in heat loss responses of SkBF and sweating during exercise performed at progressive increases in the requirement for heat loss.

METHODS

Sixteen adults (10 males and six females) with (T1DM, n = 8) and without T1DM (control, n = 8) matched for age, sex, body surface area, and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W·m in the heat (35°C and 20% relative humidity). Each rate was performed sequentially for 30 min. Local sweat rate (LSR, ventilated capsule), sweat gland activation (modified iodine paper technique), and sweat gland output were measured on the forearm, upper back, and chest, whereas SkBF (laser Doppler) was measured on the forearm and upper back.

RESULTS

Despite a similar requirement for heat loss, LSR was lower in T1DM on the forearm and chest relative to that in the control. Reductions were measured in the second (forearm: 0.68 ± 0.14 vs 0.85 ± 0.11 mg·min·cm, P = 0.004; chest: 0.58 ± 0.08 vs 0.82 ± 0.12 mg·min·cm, P = 0.046) and third exercise bouts (forearm: 0.75 ± 0.11 vs 0.98 ± 0.12 mg·min·cm, P = 0.005; chest: 0.66 ± 0.1 vs 1.02 ± 0.16 mg·min·cm, P = 0.032). Differences in forearm LSR were the result of a reduction in sweat gland output, whereas the decrease in chest LSR was due to lower sweat gland activation. SkBF did not differ between groups.

CONCLUSIONS

We show that T1DM is associated with impairments in heat dissipation during exercise in the heat, as evidenced by attenuated LSR. However, these differences are only shown beyond a certain requirement for heat loss.

Predictive Potential of Twenty-Two Biochemical Biomarkers for Coronary Artery Disease in Type 2 Diabetes Mellitus

We investigated the potential of a panel of 22 biomarkers to predict the presence of coronary artery disease (CAD) in type 2 diabetes mellitus (DM2) patients. The study enrolled 96 DM2 patients with (n = 75) and without (n = 21) evidence of CAD. We assessed a biochemical profile that included 22 biomarkers: total cholesterol, LDL, HDL, LDL/HDL, triglycerides, glucose, glycated hemoglobin, fructosamine, homocysteine, cysteine, methionine, reduced glutathione, oxidized glutathione, reduced glutathione/oxidized glutathione, L-arginine, asymmetric dimethyl-L-arginine, symmetric dimethyl-L-arginine, asymmetric dimethyl-L-arginine/L-arginine, nitrate plus nitrite, S-nitrosothiols, nitrotyrosine, and n-acetyl-β-glucosaminidase. Prediction models were built using logistic regression models. We found that eight biomarkers (methionine, nitratate plus nitrite, n-acetyl-β-glucosaminidase, BMI, LDL, HDL, reduced glutathione, and L-arginine/asymmetric dimethyl-L-arginine) along with gender and BMI were significantly associated with the odds of CAD in DM2. These preliminary findings support the notion that emerging biochemical markers might be used for CAD prediction in patients with DM2. Our findings warrant further investigation with large, well-designed studies.

Impaired endothelium-dependent skin microvascular function during high-dose atorvastatin treatment in patients with type 1 diabetes

AIMS

The present study investigated the effects of lipid-lowering therapy with atorvastatin on skin microvascular function in patients with type 1 diabetes and dyslipidaemia.

METHODS

Twenty patients received daily treatment with atorvastatin 80 mg or placebo during 2 months in a randomised, double-blind, cross-over study. Forearm skin microcirculation was investigated with laser Doppler perfusion imaging during iontophoresis of acetylcholine and sodium nitroprusside to assess endothelium-dependent and endothelium-independent microvascular reactivity, respectively. Various biochemical markers of endothelial function were also investigated.

RESULTS

Endothelium-dependent microvascular reactivity decreased during atorvastatin (p < 0.001), showing a significant treatment effect compared with placebo (p = 0.04). Atorvastatin treatment was also associated with increased haemoglobin A1C levels from 7.45% to 7.77% (p = 0.008).

CONCLUSIONS

The present study shows impaired endothelium-dependent skin microvascular function during high-dose atorvastatin treatment in patients with type 1 diabetes, thus implicating a risk for deterioration of microvascular function during such therapy in these patients.

Acute hyperglycemia does not impair microvascular reactivity and endothelial function during hyperinsulinemic isoglycemic and hyperglycemic clamp in type 1 diabetic patients

Aims. The aim of this study was to evaluate the effect of acute glycemia increase on microvasculature and endothelium in Type 1 diabetes during hyperinsulinemic clamp. Patients and Methods. Sixteen patients (51 ± 7 yrs) without complications were examined during iso- and hyperglycemic clamp (glucose increase 5.5 mmol·L⁻¹). Insulin, lipid parameters, cell adhesion molecules and fibrinogen were analyzed. Microvascular reactivity (MVR) was measured by laser Doppler flowmetry. Results. Maximum perfusion and the velocity of perfusion increase during PORH were higher in hyperglycemia compared to baseline (47 ± 16 versus 40 ± 16 PU, P < 0.01, and 10.4 ± 16.5 versus 2.6 ± 1.5 PU·s⁻¹, P < 0.05, resp.). Time to the maximum perfusion during TH was shorter and velocity of perfusion increase during TH higher at hyperglycemia compared to isoglycemic phase (69 ± 15 versus 77 ± 16 s, P < 0.05, and 1.4 ± 0.8 versus 1.2 ± 0.7 PU·s⁻¹, P < 0.05, resp.). An inverse relationship was found between insulinemia and the time to maximum perfusion during PORH (r = −0.70, P = 0.007). Conclusion. Acute glycemia did not impair microvascular reactivity in this clamp study in Type 1 diabetic patients. Our results suggest that insulin may play a significant role in the regulation of microvascular perfusion in patients with Type 1 diabetes through its vasodilation effect and can counteract the effect of acute glucose fluctuations.

Early stage detection of conduit artery endothelial dysfunction in patients with type 1 diabetes

Flow-mediated dilatation evaluation using hand skin heating may possibly be more accurate than post-ischaemic hyperaemia to detect conduit artery endothelial dysfunction in type 1 diabetes. We measured in 24 type 1 diabetic patients (n=16 without microangiopathy) and 24 healthy matched subjects radial artery diameter (echotracking), blood flow and mean wall shear stress during heating and post-ischaemic hyperaemia. Compared with controls, flow-mediated dilatation was lower in diabetic patients during post-ischaemic hyperaemia and heating. However, in the subgroup of uncomplicated patients, a decreased flow-mediated dilatation was only apparent during heating (17.1+/-1.6% vs. 24.3+/-0.7%, p<0.05) but not during post-ischaemic hyperaemia (10.1+/-1.1% vs. 10.5+/-0.6%, NS). This was confirmed by the lower slope of the diameter-mean wall shear stress relationship in these patients in the absence of modification in endothelium-independent dilatation. We conclude that hand skin heating permits the early detection of conduit artery endothelial dysfunction in type 1 diabetic patients with normal response to post-ischaemic hyperaemia. This procedure could be useful to investigate the prognostic role of vascular dysfunction and the impact of vasculoprotective treatments in this patient population.

Biomarkers of oxidative stress and endothelial dysfunction in glucose intolerance and diabetes mellitus

OBJECTIVES

To evaluate biomarkers of endothelial dysfunction and oxidative stress in glucose intolerance (GI) compared to overt diabetes (DM2).

DESIGN AND METHODS

140 volunteers including 96 with DM2, 32 with GI and 12 controls (C) were studied. (*)NO metabolites, (*)NO synthase inhibitors, thiols and N-acetyl-beta-glucosaminidase (NAGase) activity were analyzed by chemiluminescence, capillary electrophoresis, ELISA and colorimetric assay, respectively.

RESULTS

(*)NO metabolites were higher in GI (NOx: p=0.03; S-nitrosothiols: p=0.001) and DM2 (p=0.006; p=0.0006) groups in relation to group C, while nitrotyrosine was higher only in the DM2 group in comparison to the other groups. NAGase activity was elevated in GI (p=0.003) and DM2 (p=0.0004) groups in relation to group C, as well as, ADMA (p=0.01; p=0.003) and GSSG (p=0.01; p=0.002).

CONCLUSIONS

(*)NO metabolites, (*)NO synthase inhibitors, thiols and NAGase are biomarkers suitable to indicate endothelial dysfunction and oxidative stress in the early stages of impaired response to insulin.

Improved endothelial function following a 14-month resistance exercise training program in adults with type 2 diabetes

OBJECTIVE

We examined the effect of a 14-month progressive resistance training (PRT) program on endothelial function in both a supervised training (Center) group and non-supervised training (Home) group of patients with type 2 diabetes. We studied 28 men and women with type 2 diabetes who participated in a 14-month PRT involving an initial 2-month supervised program and a 12-month maintenance program.

METHODS

Endothelial function testing was performed through laser doppler flow responses in the skin microcirculation to iontophoresis of acetylcholine (ACh) and sodium nitroprusside (NaNP) and doses of 4, 8 and 16mC were used. Measurements of vascular response (VR), HbA1c, weight and blood pressure were performed at 0, 2 and 14 months.

RESULTS

VR to ACh and NaNP was significantly increased at 14 months compared with baseline in both the Center and Home groups. However, no between-group differences were observed. A significant correlation was observed between HbA1c and VR to ACh at baseline and 8 weeks using 8mC dose of ACh. There was a strong correlation between HbA1c at baseline and VR at 14 months using all three doses of ACh (4mC:r=-0.546, p=0.003, 8mC:r=-0.470, p=0.002, 16mC:r=-0.547, p=0.006).

CONCLUSIONS/INTERPRETATION

Endothelial function is improved following 14 months of PRT in type 2 diabetes both in a supervised and non-supervised program. Strong correlations with HbA1c including initial HbA1c levels suggest that glycemic control may be an important factor in long-term regulation of endothelial function.

Oxidative stress and endothelium influenced by metformin in type 2 diabetes mellitus

OBJECTIVE

Metformin may influence atherogenesis but the mechanisms are not well understood. A pilot study was undertaken to determine whether metformin administration is associated with changes in oxidative stress and endothelial function.

METHODS

Fifteen type 2 diabetic patients were treated for 3 months with metformin (1,700 mg daily) or with a placebo in a crossover study. Laboratory parameters of oxidative stress, fibrinolysis and endothelial function were evaluated both prior to and following the respective treatments. In addition, laser Doppler was used to determine microcirculation changes in the skin.

RESULTS

Increases in serum N-acetyl-beta-glucosaminidase activity (p < 0.05) and plasma malondialdehyde concentration were found following 1 month of metformin administration. Three months of treatment was accompanied by significantly increased plasma malondialdehyde (p < 0.001) and ascorbic acid (p < 0.01) concentrations as well as the alpha-tocopherol/(cholesterol + triglyceride) ratio (p < 0.001). The concentration of tissue plasminogen activator (tPA), vascular cell-adhesion molecules (VCAM) and intercellular cell-adhesion molecules (ICAM) were significantly decreased (p < 0.01) compared with placebo. Microcirculation measured by laser Doppler flowmetry was not significantly changed.

CONCLUSIONS

We conclude that initiation of metformin treatment in type 2 diabetic patients is associated with improved diabetes control as well as with activation of oxidative stress together with antioxidant system. The atherogenic process measured by biochemical indicators is diminished in parallel. Our results show that in short-term metformin administration in type 2 diabetes promotes endothelium effects associated with a complex of metabolic changes.

Oxidant stress, immune dysregulation, and vascular function in type I diabetes

Although high glucose is an important contributor to diabetic vasculopathies, complications still occur in spite of tight glycemic control, suggesting that some critical event prior to or concurrent with hyperglycemia may contribute to early vascular changes. Utilizing previously published and new experimental evidence, this review will discuss how prior to the hyperglycemic state, an imbalance between oxidants and antioxidants may contribute to early vascular dysfunction and set in motion proinflammatory insults that are further amplified as the diabetes develops. This imbalance results from the resetting of the equilibrium between vessel superoxide/H(2)O(2) production and/or decreased antioxidant defenses. Such an imbalance may cause endothelial dysfunction, characterized by abnormal endothelium-dependent vasoreactivity, as the first sign of blood vessel damage, followed by morphological changes of the vessel wall and inflammation. As such, increased oxidant stress in preglycemic states may be a critically central initiating event that underlies the pathogenesis of life-threatening vascular diseases in autoimmune diabetes. This review focuses on the relationship between oxidative stress, immune dysregulation, and vascular injury in type 1 diabetes, and how the discovery of novel pathways of vascular disease in nonobese diabetic mice may direct future studies in patients with type 1 diabetes.

Flow motion pattern differences in the forehead and forearm skin: Age-dependent alterations are not specific for Alzheimer's disease

Oscillations in laser Doppler signals derived from the forehead and forearm skin were analyzed in 77 healthy probands from 4 various age groups (ranging between 15 and 77 years) and 22 late-onset sporadic Alzheimer's disease (AD) patients. A characteristic pattern of oscillations in the microcirculatory blood flux ( approximately 8 cycles/min, 0.13 Hz) was observed in the forehead skin, the occurrence of which correlated inversely with age (r = 0.80). The occurrence of forehead vasomotion pattern was 100% in the teenagers, whereas it was significantly less in the elderly control subjects (32%) and in the AD patients (18%). Forearm reactive hyperemia was provoked by 1-min occlusion of the brachial artery, and the vascular reactivity was calculated. This phenomenon also proved to be age-dependent, but the process was not related to AD. Our results indicate that the lack of forehead vasomotion reflects aging better than does the forearm vasomotion. Both of these functions are preserved in AD.

Reproducibility of different laser Doppler fluximetry parameters of postocclusive reactive hyperemia in human forearm skin

INTRODUCTION

Postocclusive reactive hyperemia in forearm skin is a commonly used model for studying microvascular reactivity function, particularly in the assessment of vascular effect of topically applied pharmacological substances. In this study, we investigated the reproducibility of several different laser-Doppler-derived parameters in the measurement of postocclusive reactive hyperemia at forearm skin in healthy subjects.

METHODS

Eighteen young healthy male volunteers were recruited and studied in a supine position while fasted. Forearm blood flow was occluded at suprasystolic pressure for 3 min. Microvascular perfusion was measured continuously using laser Doppler fluximetry. Parameters studied were maximum increase in hyperemia perfusion (PORHmax), time-to-peak (Tp), amplitude of peak perfusion (PORHpeak), percentage of hyperemic response (PORH%) and mean velocity of the hyperemia increase (PORHmax/Tp). Measurement was performed twice within each study day for 2 study days. Coefficient of variation and intraclass correlation coefficient (ICC; with 95% confidence interval) were calculated for each parameter. An ICC value above 0.75 was interpreted as "excellent reproducibility".

RESULTS

ICC analysis showed that all studied parameters, except for PORH%, demonstrated excellent reproducibility for both within- and between-day measurements. Satisfactory intraday and interday coefficients of variation (<10%) were also obtained for these parameters.

CONCLUSION

Laser-Doppler-derived PORHmax, Tp, PORHpeak and PORHmax/Tp were highly reproducible parameters for measuring microvascular reactivity during reactive hyperemia, with PORHmax shown as the most reproducible index. PORH% is, however, less reproducible. These findings have implications for the use of laser Doppler fluximetry coupled with 3-min-occlusion PORHmax as a useful and reliable noninvasive clinical measurement index of microvascular function.

Markers of endothelial dysfunction in the prediction of coronary artery disease in type 1 diabetes. The Pittsburgh Epidemiology of Diabetes Complications Study

Low-density lipoprotein (LDL) oxidation, the immune response it provokes, and lipoprotein subclasses measured by nuclear magnetic resonance (NMR) spectroscopy have explained some of the enhanced coronary artery disease (CAD) risks in Type 1 diabetes. We examined whether cellular adhesion molecules further improve CAD prediction. Participants were identified from the Epidemiology of Diabetes Complications (EDC) cohort, a 10-year prospective study of childhood-onset Type 1 diabetes. Mean age at baseline was 28 years, and diabetes duration was 19 years. CAD incidence was determined by EDC physician-diagnosed angina, confirmed myocardial infarction (MI), stenosis > or =50%, ischemic ECG, or revascularization. Cases were gender, age, and diabetes duration (+/-3 years) matched with the controls. The samples and risk factors used in the analyses were identified from the earliest exam prior to incidence in the cases. Sixty cases and 72 controls (including 43 pairs) had complete information on all covariates. Cox proportional hazard models with backward elimination and conditional logistic regression (for paired analyses) were conducted. Separate analyses were conducted to examine whether E-selectin related differently to soft (ischemic ECG and angina; n=68) or hard (revascularization, MI, and fatal events; n=37) CAD endpoints. Mean E-selectin concentration was elevated among cases (P=.0009) compared to controls. Adjusting for previously established CAD risk factors, E-selectin remained an independent predictor of CAD (HR=1.07, 95% Cl=1.01-1.15). Multivariable models confirmed the importance of E-selectin as a risk factor of soft (HR=1.13, 95% Cl=1.03-1.24; HRs are per standard deviation increase) but not hard CAD. Study results suggest that E-selectin may enhance CAD prediction beyond traditional risk factors or markers of oxidative stress in Type 1 diabetes.