Impaired skin microvascular function in children, adolescents, and young adults with type 1 diabetes

The Impact of Disease Duration on Microcirculatory Dysfunction in Young Patients with Uncomplicated Type 1 Diabetes

This study aimed to evaluate the earliest changes in the structure and function of the peripheral microcirculation using capillaroscopy and transcutaneous oxygen pressure measurement in children and adolescents with type 1 diabetes mellitus at baseline and during post-occlusive reactive hyperemia (PORH) in the function of diabetes duration. Sixty-seven patients with type 1 diabetes mellitus (T1D), aged 8 to 18 years, and twenty-eight age- and sex-matched healthy subjects were included in the analysis. Diabetic patients were divided into subgroups based on median disease duration. The subgroups differed in chronological age, lipid levels, and thyroid hormones. Capillaroscopy was performed twice: at baseline and then again after the PORH test. Transcutaneous oxygen pressure also was recorded under baseline conditions during and after the PORH test. Comparison of capillaroscopy and transcutaneous oxygen pressure parameters at rest and after the PORH showed no statistically significant difference between the subgroups. This remained true after adjusting for variables that differentiated the two subgroups. However, in the group of patients with long-standing diabetes, significant negative correlations were observed between the Coverage value after the PORH test and capillary reactivity with TcPO2_zero (biological zero). Significant positive correlations were also found between distance after the PORH test and TcPO2_zero. The results of our study indicate that in patients with a shorter duration of diabetes, the use of multiple tests provides a better characterization of the structure and function of microcirculation because the onset of dysfunction does not occur at the same time in all the tests.

Reproducibility of Laser Doppler Flowmetry in gingival microcirculation. A study on six different protocols

OBJECTIVES

Laser Doppler Flowmetry (LDF) is a non-invasive technique for the assessment of tissue blood flow, but increased reproducibility would facilitate longitudinal studies. The aim of the study was to assess the interday reproducibility of Laser Doppler Flowmetry (LDF) at rest, at elevated local temperatures, and with the use of the vasodilator Methyl Nicotinate (MN) in six interconnected protocols for the measurement of the blood supply to the microvascular bed of the gingiva.

METHODS

Ten healthy volunteers were included. Interweek LDF measurements with custom-made acrylic splints were performed. Six protocols were applied in separate regions of interest (ROI): 1; basal LDF, 2; LDF with thermoprobe 42 °C, 3; LDF with thermoprobe 45 °C, 4; LDF with thermoprobe 42 °C and MN, 5; LDF with thermoprobe 45 °C and MN and 6; LDF with MN.

RESULTS

Intra-individual reproducibility was assessed by the within-subject coefficient of variation (wCV) and the intraclass correlation coefficient (ICC). Basal LDF measurements demonstrated high reproducibility with wCV 11.1 in 2 min and 10.3 in 5 min. ICC was 0.9 and 0.92. wCV after heat and MN was 4.9-10.3 and ICC 0.82-0.93. The topically applied MN yielded increased blood flow.

CONCLUSION

This is the first study evaluating the reproducibility of basal LDF compared to single or multiple vasodilatory stimuli in gingiva. Multiple collector fibers probe and stabilizing acrylic splints are recommended. Vasodilatory stimulation showed a tendency toward higher reproducibility. Furthermore, MN yields vasodilation in gingiva.

Wireless Dynamic Light Scattering Sensors Detect Microvascular Changes Associated With Ageing and Diabetes

This article presents clinical results of wireless portable dynamic light scattering sensors that implement laser Doppler flowmetry signal processing. It has been verified that the technology can detect microvascular changes associated with diabetes and ageing in volunteers. Studies were conducted primarily on wrist skin. Wavelet continuous spectrum calculation was used to analyse the obtained time series of blood perfusion recordings with respect to the main physiological frequency ranges of vasomotions. In patients with type 2 diabetes, the area under the continuous wavelet spectrum in the endothelial, neurogenic, myogenic, and cardio frequency ranges showed significant diagnostic value for the identification of microvascular changes. Aside from spectral analysis, autocorrelation parameters were also calculated for microcirculatory blood flow oscillations. The groups of elderly volunteers and patients with type 2 diabetes, in comparison with the control group of younger healthy volunteers, showed a statistically significant decrease of the normalised autocorrelation function in time scales up to 10 s. A set of identified parameters was used to test machine learning algorithms to classify the studied groups of young controls, elderly controls, and diabetic patients. Our conclusion describes and discusses the classification metrics that were found to be most effective.

Insulin-induced vasoconstriction is prevalent in muscle microvasculature of otherwise healthy persons with type 1 diabetes

Insulin's microvascular actions and their relationship to insulin's metabolic actions have not been well studied in adults with type 1 diabetes mellitus (T1DM). We compared the metabolic and selected micro- and macrovascular responses to insulin by healthy adult control (n = 16) and subjects with T1DM (n = 15) without clinical microvascular disease. We measured insulin's effect on 1) skeletal muscle microvascular perfusion using contrast-enhanced ultrasound (CEU), 2) arterial stiffness using carotid-femoral pulse-wave velocity (cfPWV) and radial artery pulse wave analysis (PWA), and 3) metabolic insulin sensitivity by the glucose infusion rate (GIR) during a 2-h, 1 mU/min/kg euglycemic-insulin clamp. Subjects with T1DM were metabolically insulin resistant (GIR = 5.2 ± 0.7 vs. 6.6 ± 0.6 mg/min/kg, P < 0.001). Insulin increased muscle microvascular blood volume and flow in control (P < 0.001, for each) but not in subjects with T1DM. Metabolic insulin sensitivity correlated with increases of muscle microvascular perfused volume (P < 0.05). Baseline measures of vascular stiffness did not differ between groups. However, during hyperinsulinemia, cfPWV was greater (P < 0.02) in the T1DM group and the backward pulse wave pressure declined with insulin only in controls (P < 0.03), both indices indicating that insulin-induced vascular relaxation in controls only. Subjects with T1DM have muscle microvascular insulin resistance that may precede clinical microvascular disease.NEW & NOTEWORTHY Using contrast ultrasound and measures of vascular stiffness, we compared vascular and metabolic responses to insulin in patients with type 1 diabetes with age-matched controls. The patients with type 1 diabetes demonstrated both vascular and metabolic insulin resistance with more than half of the patients with diabetes having a paradoxical vasoconstrictive vascular response to insulin.

Diabetes and climate change: current evidence and implications for people with diabetes, clinicians and policy stakeholders

Climate change will be a major challenge for the world's health systems in the coming decades. Elevated temperatures and increasing frequencies of heat waves, wildfires, heavy precipitation and other weather extremes can affect health in many ways, especially if chronic diseases are already present. Impaired responses to heat stress, including compromised vasodilation and sweating, diabetes-related comorbidities, insulin resistance and chronic low-grade inflammation make people with diabetes particularly vulnerable to environmental risk factors, such as extreme weather events and air pollution. Additionally, multiple pathogens show an increased rate of transmission under conditions of climate change and people with diabetes have an altered immune system, which increases the risk for a worse course of infectious diseases. In this review, we summarise recent studies on the impact of climate-change-associated risk for people with diabetes and discuss which individuals may be specifically prone to these risk conditions due to their clinical features. Knowledge of such high-risk groups will help to develop and implement tailored prevention and management strategies to mitigate the detrimental effect of climate change on the health of people with diabetes.

Endothelial dysfunction in subfertile women with polycystic ovary syndrome

RESEARCH QUESTION

Is there an association between post-occlusive reactive hyperaemia (PORH) and ovarian stimulation in women with normoandrogenaemic polycystic ovary syndrome (PCOS)?

DESIGN

Women eligible for IVF at an academic fertility centre were invited to join this prospective study. Microvascular endothelial function was measured as PORH by laser Doppler flowmetry (LDF) before and after ovarian stimulation. Metabolic characteristics, hormone profiles and biochemical markers were analysed.

RESULTS

Thirty-four normoandrogenaemic women with PCOS and 36 normoandrogenaemic women without PCOS were included. The PCOS group displayed higher C-reactive protein levels and insulin resistance (P = 0.048 and P = 0.025, respectively). No significant difference was found in microcirculatory function between the groups at baseline. After ovarian stimulation, PORH was enhanced in the control group (slope 7.1 ± 3.3 versus 9.7 ± 4.5; P = 0.007; peak flow 30.7 ± 16.3 versus 43.5 ± 17.3, P = 0.008; however, the PCOS group experienced a blunting response to supraphysiological hormone status (slope 8.2 ± 5.1 versus 7.2 ± 4.3, P = 0.212; peak flow, 38.8 ± 19.4 versus 37.0 ± 21.8, P = 0.895).

CONCLUSIONS

Impaired microcirculatory function could be found using a non-invasive LDF technique in normoandrogenaemic women with PCOS undergoing IVF, indicating early changes in vascular endothelial dysfunction. Future observational studies should clarify whether PORH measurement might help predict IVF prognosis or obstetric complications.

Human temperature regulation under heat stress in health, disease, and injury

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Effects of Normal Reference Range of Phosphorus and Corresponding PTH on Endothelial Function in CKD Patients

Introduction

Endothelial dysfunction commonly occurs in chronic kidney disease (CKD) patients and increases the risk for cardiovascular disease. Among CKD patients, biomarkers involved in the pathogenesis of CKD-mineral bone disorder (CKD-MBD), such as phosphorus, parathyroid hormone, and fibroblast growth factor 23, are associated with endothelial dysfunction. We investigated whether these biomarkers induce endothelial dysfunction in CKD patients with normal phosphorus levels.

Methods

This cross-sectional study examined CKD patients with normal phosphorus levels; patients with an estimated glomerular filtration rate (eGFR) &lt;15 or who were under dialysis were excluded. Iontophoresis with laser doppler flowmetry (ILDF) and peripheral arterial tonometry were performed to assess endothelial function in 85 patients. Pearson's correlation coefficient, multiple regression, and mediation analyses were performed to examine the association between CKD-MBD biomarkers and endothelial dysfunction.

Results

Endothelial dysfunction was observed in all subjects with a low response to ILDF and 27% of subjects according to peripheral arterial tonometry. Acetylcholine (Ach)-induced ILDF was significantly associated with eGFR (r = 0.22, P = 0.04), intact parathyroid hormone (iPTH; r = −0.46, P &lt; 0.01), and VCAM-1 (r = −0.36, P &lt; 0.01). The reactive hyperemia index (RHI) was significantly related to phosphorus levels (r = 0.32, P &lt; 0.01) and iPTH (r = −0.39, P = 0.02). After adjusting for eGFR, iPTH and VCAM-1 remained independent factors for predicting endothelial dysfunction measured using Ach-induced ILDF. In addition, iPTH and phosphorus levels were independent predictors for endothelial dysfunction measured using RHI in the eGFR-adjusted model. Mediation analyses showed that the individual indirect effects of iPTH were significantly affected ILDF and RHI.

Conclusion

Serum levels of phosphorus and iPTH are associated with endothelial dysfunction, even in CKD patients with normal phosphorus levels.

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.

Nitric oxide-dependent micro- and macrovascular dysfunction occurs early in adolescents with type 1 diabetes

Arterial stiffness and endothelial dysfunction are both reported in children with type 1 diabetes (DM1) and may predict future cardiovascular events. In health, nitric oxide (NO) relaxes arteries and increases microvascular perfusion. The relationships between NO-dependent macro- and microvascular functional responses and arterial stiffness have not been studied in adolescents with DM1. Here, we assessed macro- and microvascular function in DM1 adolescents and age-matched controls at baseline and during an oral glucose challenge (OGTT). DM1 adolescents (n = 16) and controls (n = 14) were studied before and during an OGTT. At baseline, we measured: 1) large artery stiffness using both aortic augmentation index (AI) and carotid-femoral pulse wave velocity (cfPWV); 2) brachial flow-mediated dilation (FMD) and forearm endothelial function using postischemic flow velocity (PIFV); and 3) forearm muscle microvascular blood volume (MBV) using contrast-enhanced ultrasound. Following OGTT, AI, cfPWV, and MBV were reassessed at 60 min and MBV again at 120 min. Within individual and between-group, comparisons were made by paired and unpaired t tests or repeated measures ANOVA. Baseline FMD was lower (P = 0.02) in DM1. PWV at 0 and 60 min did not differ between groups. Baseline AI did not differ between groups but declined with OGTT only in controls (P = 0.02) and was lower than DM1 at 60 min (P < 0.03). Baseline MBV was comparable in DM1 and control groups, but declined in DM1 at 120 min (P = 0.01) and was lower than the control group (P < 0.03). There was an inverse correlation between plasma glucose and MBV at 120 min (r = -0.523, P < 0.01). No differences were noted between groups for V̇O2max (mL/min/kg), body fat (%), or body mass index (BMI). NO-dependent macro- and microvascular function, including FMD and AI, and microvascular perfusion, respectively, are impaired early in the course of DM1, precede increases of arterial stiffness, and may provide an early indicator of vascular risk.NEW & NOTEWORTHY This is the first study to show that type 1 diabetes impairs multiple nitric oxide-dependent vascular functions.

Pathophysiological Association between Diabetes Mellitus and Endothelial Dysfunction

Endothelial dysfunction plays a critical role in atherosclerosis progression, leading to cardiovascular complications. There are significant associations between diabetes mellitus, oxidative stress, and endothelial dysfunction. Oxidative stress is increased by chronic hyperglycemia and acute glucose fluctuations induced by postprandial hyperglycemia in patients with diabetes mellitus. In addition, selective insulin resistance in the phosphoinositide 3-kinase/Akt/endothelial nitric oxide (NO) synthase pathway in endothelial cells is involved in decreased NO production and increased endothelin-1 production from the endothelium, resulting in endothelial dysfunction. In a clinical setting, selecting an appropriate therapeutic intervention that improves or augments endothelial function is important for preventing diabetic vascular complications. Hypoglycemic drugs that reduce glucose fluctuations by decreasing the postprandial rise in blood glucose levels, such as glinides, α-glucosidase inhibitors and dipeptidyl peptidase 4 inhibitors, and hypoglycemic drugs that ameliorate insulin sensitivity, such as thiazolidinediones and metformin, are expected to improve or augment endothelial function in patients with diabetes. Glucagon-like peptide 1 receptor agonists, metformin, and sodium-glucose cotransporter 2 inhibitors may improve endothelial function through multiple mechanisms, some of which are independent of glucose control or insulin signaling. Oral administration of antioxidants is not recommended in patients with diabetes due to the lack of evidence for the efficacy against diabetic complications.

A Cross-Talk between the Erythrocyte L-Arginine/ADMA/Nitric Oxide Metabolic Pathway and the Endothelial Function in Subjects with Type 2 Diabetes Mellitus

(1) Background: Type-2-diabetes-mellitus (DM) is one the most important cardiovascular-risk-factors. Among many molecules regulating vascular tone, nitric oxide appears to be the most pivotal. Although micro- and macrovascular-abnormalities are extensively studied, the alterations in the nitric-oxide-metabolic-pathway require further investigations. Additionally, the role of erythrocytes in the vascular tone regulation has not been extensively explored. The aim of this study was to evaluate the endothelial-function and the nitric-oxide-metabolic-pathway in erythrocytes and plasma of diabetic individuals. (2) Methods: A total of 80 subjects were enrolled in this cross-sectional study, including 35 patients with DM and 45 healthy individuals. The endothelial-function was evaluated in response to different stimuli. (3) Results: In the DM group, decreased Arginine and citrulline concentrations in the plasma compartment with reduced Arginine/ADMA and ADMA/DMA-ratios were observed. Preserved nitric-oxide-metabolism in erythrocytes with reduced citrulline level and significantly higher NO-bioavailability were noted. Significant endothelial dysfunction in DM individuals was proved in response to the heat-stimulus. (4) Conclusions: DM patients at an early stage of disease show significant differences in the nitric-oxide-metabolic-pathway, which are more pronounced in the plasma compartment. Erythrocytes constitute a buffer with a higher nitric-oxide-bioavailability, less affected by the DM-related deviations. Patients at an early-stage of DM reveal endothelial-dysfunction, which could be diagnosed earlier using the laser-Doppler-flowmetry.

Changes in the profile of circulating HDL subfractions in severe obese adolescents following a weight reduction program

BACKGROUND AND AIMS

Epidemiological studies show that obese adolescents are candidates to suffer cardiovascular pathologies in adulthood. In order to detect subfractions with a diagnostic value for future cardiovascular disorders, we analyzed the complete lipoprotein profile of severely obese adolescents.

METHODS AND RESULTS

Twenty-eight obese adolescents free from comorbidities were admitted into a weight reduction program. Anthropometric parameters were monitored. The circulating lipoproteins and glycemia were measured at the beginning and at the end of the study by conventional blood analysis as well as by using lipoprotein electrophoresis. Twenty-one puberty-matched normal-weight adolescents were recruited as controls. After 4 months, participants improved anthropometric parameters. Blood analysis indicated that circulating lipoproteins were in the healthy range during intervention. Nevertheless, results obtained from lipoprotein electrophoresis showed a significant increase in the large high-density lipoprotein subfraction in the obese population at the end of intervention, but significantly lower than normal-weight counterparts. In addition, intermediate- and low-density lipoprotein subfractions were in the healthy range in controls and in obese adolescents during intervention.

CONCLUSIONS

Altogether, it seems that the obese adolescents with no comorbidities do not develop a clear dyslipidemia. However, low values of large high-density lipoprotein subfractions could be considered as candidate predictors to develop cardiovascular disease in the future. For this reason, diet and exercise are key tools to fight against this pathology.

REGISTRATION NUMBER FOR CLINICAL TRIALS

ISRCTN99414527.

Type I interferons as key players in pancreatic β-cell dysfunction in type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by pancreatic islet inflammation (insulitis) and specific pancreatic β-cell destruction by an immune attack. Although the precise underlying mechanisms leading to the autoimmune assault remain poorly understood, it is well accepted that insulitis takes place in the context of a conflicting dialogue between pancreatic β-cells and the immune cells. Moreover, both host genetic background (i.e., candidate genes) and environmental factors (e.g., viral infections) contribute to this inadequate dialogue. Accumulating evidence indicates that type I interferons (IFNs), cytokines that are crucial for both innate and adaptive immune responses, act as key links between environmental and genetic risk factors in the development of T1D. This chapter summarizes some relevant pathways involved in β-cell dysfunction and death, and briefly reviews how enteroviral infections and genetic susceptibility can impact insulitis. Moreover, we present the current evidence showing that, in β-cells, type I IFN signaling pathway activation leads to several outcomes, such as long-lasting major histocompatibility complex (MHC) class I hyperexpression, endoplasmic reticulum (ER) stress, epigenetic changes, and induction of posttranscriptional as well as posttranslational modifications. MHC class I overexpression, when combined with ER stress and posttranscriptional/posttranslational modifications, might lead to sustained neoantigen presentation to immune system and β-cell apoptosis. This knowledge supports the concept that type I IFNs are implicated in the early stages of T1D pathogenesis. Finally, we highlight the promising therapeutic avenues for T1D treatment directed at type I IFN signaling pathway.

Vascular Effects of ACE (Angiotensin-Converting Enzyme) Inhibitors and Statins in Adolescents With Type 1 Diabetes

An increased albumin-creatinine ratio within the normal range can identify adolescents at higher risk of developing adverse cardio-renal outcomes as they progress into adulthood. Utilizing a parallel randomized controlled trial and observational cohort study, we characterized the progression of vascular phenotypes throughout this important period and investigated the effect of ACE (angiotensin-converting enzyme) inhibitors and statins in high-risk adolescents. Endothelial function (flow-mediated dilation and reactive hyperemia index) and arterial stiffness (carotid-femoral pulse wave velocity) were assessed in 158 high-risk participants recruited to a randomized, double-blind placebo-controlled 2×2 factorial trial (randomized, placebo-controlled trial) of ACE inhibitors and/or statins in adolescents with type 1 diabetes (AdDIT [Adolescent Type 1 Diabetes cardio-renal Intervention Trial]). Identical measures were also assessed in 215 lower-risk individuals recruited to a parallel observational study. In the randomized, placebo-controlled trial, high-risk patients randomized to ACE inhibitors had improved flow-mediated dilation after 2 to 4 years of follow-up (mean [95% CI]: 6.6% [6.0-7.2] versus 5.3% [4.7-5.9]; P=0.005), whereas no effect was observed following statin use (6.2% [5.5-6.8] versus 5.8% [5.1-6.4]; P=0.358). In the observational study, patients classed as high-risk based on albumin-creatinine ratio showed evidence of endothelial dysfunction at the end of follow-up (flow-mediated dilation=4.8% [3.8-5.9] versus 6.3% [5.8-6.7] for high-risk versus low-risk groups; P=0.015). Neither reactive hyperemia index nor pulse wave velocity were affected by either treatment (P>0.05 for both), but both were found to increase over the duration of follow-up (0.07 [0.03-0.12]; P=0.001 and 0.5 m/s [0.4-0.6]; P<0.001 for reactive hyperemia index and pulse wave velocity, respectively). ACE inhibitors improve endothelial function in high-risk adolescents as they transition through puberty. The longer-term protective effects of this intervention at this early age remain to be determined. Registration- URL: https://www.clinicaltrials.gov; Unique identifier NCT01581476.

Increased Intraplatelet ADMA Level May Promote Platelet Activation in Diabetes Mellitus

Background

Antiplatelet therapy has become a standard therapeutic approach in the secondary prevention of cardiovascular system disorders of thrombotic origin. Patients with concomitant diabetes mellitus (DM) obtain fewer benefits from this treatment. Hence, the pathophysiology of altered platelet function in response to glucose metabolism impairment should be of particular interest.

Objectives

The aim of our study was to verify if the platelet expression of the asymmetric dimethylarginine (ADMA) in diabetic patients differs in comparison to the nondiabetic ones. The correlation of platelet-ADMA with platelet activation and aggregation as well as with other risk factors was also investigated. Material and Methods. A total of 61 subjects were enrolled in this study, including thirty-one type 2 diabetic subjects without diabetes-related organ damage. Physical examination was followed by blood collection with an assessment of platelet aggregation, traditional biochemical cardiovascular risk factors, and evaluation of nitric oxide bioavailability parameters in plasma and thrombocytes. Subsequently, the assessment of endothelial function using Peripheral Arterial Tonometry and Laser Doppler Flowmetry (LDF) was performed.

Results

In the DM group, elevated concentration of intraplatelet ADMA and higher ADMA/SDMA ratio compared to the control group was observed. It was accompanied by higher ADP-mediated platelet aggregation and lower microvascular response to a local thermal stimulus measured by LDF in the diabetes group.

Conclusions

Type 2 diabetes is related to higher intraplatelet concentration of asymmetric dimethylarginine (ADMA), which may result in impaired platelet-derived nitric oxide synthesis and subsequent increased platelet activity, as assessed by the ADP-induced aggregation. Laser Doppler Flowmetry, compared to EndoPAT 2000, appears to be a more sensitive indicator of the impaired microvasculature vasodilation in diabetics without the presence of clinically significant target organ damage.

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.

Inhibition of NFAT Signaling Restores Microvascular Endothelial Function in Diabetic Mice

Central to the development of diabetic macro- and microvascular disease is endothelial dysfunction, which appears well before any clinical sign but, importantly, is potentially reversible. We previously demonstrated that hyperglycemia activates nuclear factor of activated T cells (NFAT) in conduit and medium-sized resistance arteries and that NFAT blockade abolishes diabetes-driven aggravation of atherosclerosis. In this study, we test whether NFAT plays a role in the development of endothelial dysfunction in diabetes. NFAT-dependent transcriptional activity was elevated in skin microvessels of diabetic Akita (Ins2 ^+/- ) mice when compared with nondiabetic littermates. Treatment of diabetic mice with the NFAT blocker A-285222 reduced NFATc3 nuclear accumulation and NFAT-luciferase transcriptional activity in skin microvessels, resulting in improved microvascular function, as assessed by laser Doppler imaging and iontophoresis of acetylcholine and localized heating. This improvement was abolished by pretreatment with the nitric oxide (NO) synthase inhibitor l-N ^G-nitro-l-arginine methyl ester, while iontophoresis of the NO donor sodium nitroprusside eliminated the observed differences. A-285222 treatment enhanced dermis endothelial NO synthase expression and plasma NO levels of diabetic mice. It also prevented induction of inflammatory cytokines interleukin-6 and osteopontin, lowered plasma endothelin-1 and blood pressure, and improved mouse survival without affecting blood glucose. In vivo inhibition of NFAT may represent a novel therapeutic modality to preserve endothelial function in diabetes.

Early Endothelial Dysfunction in Type 1 Diabetes Is Accompanied by an Impairment of Vascular Smooth Muscle Function: A Meta-Analysis

Background: A large yet heterogeneous body of literature exists suggesting that endothelial dysfunction appears early in type 1 diabetes, due to hyperglycemia-induced oxidative stress. The latter may also affect vascular smooth muscles (VSM) function, a layer albeit less frequently considered in that pathology. This meta-analysis aims at evaluating the extent, and the contributing risk factors, of early endothelial dysfunction, and of the possible concomitant VSM dysfunction, in type 1 diabetes. Methods: PubMed, Web of Sciences, Cochrane Library databases were screened from their respective inceptions until October 2019. We included studies comparing vasodilatory capacity depending or not on endothelium (i.e., endothelial function or VSM function, respectively) in patients with uncomplicated type 1 diabetes and healthy controls. Results: Fifty-eight articles studying endothelium-dependent function, among which 21 studies also assessed VSM, were included. Global analyses revealed an impairment of standardized mean difference (SMD) (Cohen's d) of endothelial function: -0.61 (95% CI: -0.79, -0.44) but also of VSM SMD: -0.32 (95% CI: -0.57, -0.07). The type of stimuli used (i.e., exercise, occlusion-reperfusion, pharmacological substances, heat) did not influence the impairment of the vasodilatory capacity. Endothelial dysfunction appeared more pronounced within macrovascular than microvascular beds. The latter was particularly altered in cases of poor glycemic control [HbA_1c > 67 mmol/mol (8.3%)]. Conclusions: This meta-analysis not only corroborates the presence of an early impairment of endothelial function, even in response to physiological stimuli like exercise, but also highlights a VSM dysfunction in children and adults with type 1 diabetes. Endothelial dysfunction seems to be more pronounced in large than small vessels, fostering the debate on their relative temporal appearance.

Plasma Copeptin and Risk of Lower-Extremity Amputation in Type 1 and Type 2 Diabetes

OBJECTIVE

Diabetes is the leading cause of nontraumatic lower-extremity amputations (LEAs). Identification of patients with foot ulcers at risk for amputation remains clinically challenging. Plasma copeptin, a surrogate marker of vasopressin, is associated with the risk of cardiovascular and renal complications in diabetes.

RESEARCH DESIGN AND METHODS

We assessed the association between baseline plasma copeptin and risk of LEA during follow-up in four cohorts of people with type 1 (GENESIS, n = 503, and GENEDIAB, n = 207) or type 2 diabetes (DIABHYCAR, n = 3,101, and SURDIAGENE, n = 1,452) with a median duration of follow-up between 5 and 10 years. Copeptin concentration was measured in baseline plasma samples by an immunoluminometric assay.

RESULTS

In the pooled cohorts with type 1 diabetes (n = 710), the cumulative incidence of LEA during follow-up by increasing tertiles (tertile 1 [TER1], TER2, and TER3) of baseline plasma copeptin was 3.9% (TER1), 3.3% (TER2), and 10.0% (TER3) (P = 0.002). Cox regression analyses confirmed the association of copeptin with LEA: hazard ratio (HR) for 1 SD increment of log[copeptin] was 1.89 (95% CI 1.28-2.82), P = 0.002. In the pooled cohorts of type 2 diabetes (n = 4,553), the cumulative incidence of LEA was 1.1% (TER1), 2.9% (TER2), and 3.6% (TER3) (P < 0.0001). In Cox regression analyses, baseline plasma copeptin was significantly associated with LEA: HR for 1 SD increment of log[copeptin] was 1.42 (1.15-1.74), P = 0.001. Similar results were observed in the cohort with type 2 diabetes for lower-limb revascularization (HR 1.20 [95% CI 1.03-1.39], P = 0.02).

CONCLUSIONS

Baseline plasma copeptin is associated with cumulative incidence of LEA in cohorts of people with both type 1 and type 2 diabetes and may help to identify patients at risk for LEA.

The impact of autoimmune thyroiditis on skin microcirculation in children with non-complicated type 1 diabetes mellitus

BACKGROUND

The impairment of endothelial function in type 1 diabetes mellitus (DM1) is considered as the basis of microvascular complications. In DM1 patients autoimmune thyroiditis is a frequent comorbidity which may be responsible for further deterioration of microcirculation function. In studies investigating the relationship between cardiovascular risk factors and microvascular function, skin microcirculation is widely used. The aim of our study was to evaluate the impact of coexisting autoimmune thyroiditis on skin microcirculation in children with type I diabetes mellitus.

SUBJECTS

The study group consisted of 25 pediatric DM1 patients, 25 pediatric patients with type 1 diabetes and autoimmune thyroiditis (DM1 + AIT) and 29 control subjects matched for age and gender. The DM1 and DM1 + AIT patients were also matched for age at onset of DM and diabetes duration.

METHODS

Performed capillaroscopy studies employed non-selective stimuli such as post-occlusive reactive hyperemia (PORH) and venous occlusion (VO) tests. The relative area covered by capillaries (coverage) and the distance between capillaries were assessed. These measurements were performed before tests as well as after PORH and VO.

RESULTS

Coverage at baseline, after PORH and VO and distance after VO differ significantly between control subjects and the group DM1 + AIT. The coverage at baseline, after PORH and VO were significantly smaller in DM1 + AIT compared with the control group. Post-hoc analysis after controlling for lipids levels showed that differences between the DM1 + AIT and control group were remained only for coverage at baseline and after VO. Significant differences between DM1 + AIT and DM1 and control group for coverage after VO were also presented.

CONCLUSIONS

Coexisting autoimmune thyroiditis significantly deteriorates skin microcirculation function in pediatric non-complicated type 1 diabetic patients. This process is independent of patient age, diabetes duration and age of diabetes onset.

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.

Microvascular endothelial dysfunction during cardiopulmonary bypass in surgery for correction of cyanotic and acyanotic congenital heart disease

OBJECTIVE

To evaluate endothelium-dependent microvascular reactivity during cardiopulmonary bypass (CPB) in surgery for the correction of cyanotic and acyanotic congenital heart disease (CHD) in children and infants using laser Doppler perfusion monitoring (LDPM).

METHODS

This cross-sectional observational study included one hundred consecutive acyanotic (AC, n = 61) and cyanotic (C, n = 39) pediatric patients scheduled for cardiac surgery for correction of CHD. The endothelium-dependent microvascular vasodilation of the skin of the forehead was evaluated using a single-point LDPM coupled with local thermal hyperemia (LTH).

RESULTS

LTH induced significant increases in microvascular conductance both in AC and C patients after the induction of anesthesia, during CPB and after weaning from CPB. Nevertheless, the vasodilation induced by LTH was significantly blunted during CPB when compared with values obtained after the induction of anesthesia both in AC and C patients. Microvascular endothelial reactivity nearly normalized after the discontinuation of CPB.

CONCLUSION

The evaluation of systemic microvascular reactivity on the forehead skin of infants and children using LDPM appears to be a valuable tool for optimizing microvascular perfusion during CPB in pediatric cardiac surgery.

Cardiac and Vascular Target Organ Damage in Pediatric Hypertension

Atherosclerosis begins in youth and is associated with the presence of numerous modifiable cardiovascular (CV) risk factors, including hypertension. Pediatric hypertension has increased in prevalence since the 1980s but has plateaued in recent years. Elevated blood pressure levels are associated with impairments to cardiac and vascular structure and both systolic and diastolic function. Blood pressure-related increases in left ventricular mass (LVM) and abnormalities in cardiac function are associated with hard CV events in adulthood. In addition to cardiac changes, key vascular changes occur in hypertensive youth and adults. These include thickening of the arteries, increased arterial stiffness, and decreased endothelial function. This review summarizes the epidemiologic burden of pediatric hypertension, its associations with target organ damage (TOD) of the cardiac and vascular systems, and the impact of these adverse CV changes on morbidity and mortality in adulthood.

Skin vasoconstriction as a heat conservation thermoeffector

Cold exposure stimulates heat production and conservation to protect internal temperature. Heat conservation is brought about via reductions in skin blood flow. The focus, here, is an exploration of the mechanisms, particularly in humans, leading to that cutaneous vasoconstriction. Local skin cooling has several effects: (1) reduction of tonic nitric oxide formation by inhibiting nitric oxide synthase and element(s) downstream of the enzyme, which removes tonic vasodilator effects, yielding a relative vasoconstriction; (2) translocation of intracellular alpha-2c adrenoceptors to the vascular smooth-muscle cell membrane, enhancing adrenergic vasoconstriction; (3) increased norepinephrine release from vasoconstrictor nerves; and (4) cold-induced vasodilation, seen more clearly in anastomoses-rich glabrous skin. Cold-induced vasodilation occurs in nonglabrous skin when nitric oxide synthase or sympathetic function is blocked. Reflex responses to general body cooling complement these local effects. Sympathetic excitation leads to the increased release of norepinephrine and its cotransmitter neuropeptide Y, each of which contributes significantly to the vasoconstriction. The contributions of these two transmitters vary with aging, disease and, in women, reproductive hormone status. Interaction between local and reflex mechanisms is in part through effects on baseline and in part through removal of the inhibitory effects of nitric oxide on adrenergic vasoconstriction.

Diabetic Microvascular Disease: An Endocrine Society Scientific Statement

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Post-occlusive reactive hyperaemia of skin microvasculature and foot complications in type 2 diabetes

AIMS

Diabetes-related microvascular disease has been implicated in the development of foot ulceration and amputation. Assessment of microvascular function may be effective in identifying those at risk of diabetic foot complications. We investigated the relationship between active or previous foot complication and post-occlusive reactive hyperaemia (PORH) measured by laser-Doppler fluxmetry (LDF) in people with type 2 diabetes.

METHODS

PORH measures were obtained from the hallux apex in 105 people with type 2 diabetes. Associations were investigated between active or previous foot complication and PORH measures: time to peak (TtPeak) and peak as a percentage of baseline (P%BL). Multinomial logistic regression was used to determine the association of PORH with the likelihood of active foot ulcer or previous foot complication.

RESULTS

For each second increase in TtPeak, the likelihood of a participant having a history of foot complication is increased by 2% (OR=1.019, p=0.01). This association was not reflected in people with an active foot ulcer (OR=1.003, p=0.832). P%BL was not found to be significantly different between those with a current or previous foot complication and those without (p=0.404).

CONCLUSIONS

This investigation in a cohort with type 2 diabetes has demonstrated that longer TtPeak is associated with history of diabetic foot complications.

Endothelial dysfunction during long-term follow-up in children with STEC hemolytic-uremic syndrome

BACKGROUND

Shiga-toxin-producing Escherichia coli (STEC)-associated hemolytic-uremic syndrome (HUS) is a major cause of acute kidney injury (AKI), especially in children. Its long-term outcome with respect to endothelial damage remains largely elusive.

METHODS

This was a cross-sectional study in 26 children who had suffered from STEC-HUS in the past and achieved a complete recovery of renal function (eGFR >90 ml/min/1.73 m²). Skin microcirculation after local heating was assessed by laser Doppler fluximetry, carotid-femoral pulse wave velocity (PWV), carotid intima media thickness (cIMT), 24-h ambulatory blood pressure, and angiopoietin (Ang) 1 and 2 serum levels after a median follow-up period of 6.1 years. The results were compared to those of healthy controls.

RESULTS

All patients were normotensive, mean eGFR was 102 (range 91-154) ml/min/1.73 m², and 13 of the 26 patients showed albuminuria. Endothelial dysfunction was present in 13 patients, and the mean serum Ang2/Ang1 ratio was increased compared to healthy children (each p < 0.05). In contrast, mean values for PWV and cIMT in the patients did not differ from those of the controls. Endothelial dysfunction was significantly associated with younger age at STEC-HUS manifestation, time after HUS, and presence of albuminuria.

CONCLUSION

The results of this study highlight the need for long-term follow-up of STEC-HUS patients even after complete recovery of eGFR and lack of hypertension with respect to microvascular damage.

Skin microvascular function in patients with type 1 diabetes: An observational study from the onset of diabetes

BACKGROUND

The development of disturbances in skin microcirculation in type 1 diabetes is not well characterised. We assessed skin microcirculation longitudinally from the onset of diabetes up to 29 years of duration to investigate when such disturbances start.

MATERIAL AND METHODS

Seventeen adult patients with type 1 diabetes participated. Skin microvascular function in digit IV of the left hand was investigated by laser Doppler fluxmetry (LDF, arbitrary units [AU]). LDF was carried out at rest and following one-min arterial occlusion. Time to peak LDF (s) and percentage increase of LDF (post-occlusive reactive hyperaemia, PRH%) were determined. Retinopathy was assessed from fundus photographs or ophthalmoscopic recordings.

RESULTS

Skin microvascular function remained normal during the first five years. Compared with baseline and a non-diabetic reference group, time to peak LDF was prolonged after 7-9 years of diabetes ( p < 0.01). PRH% was lower than in the reference group after 7-9 years ( p < 0.01), and lower than baseline after 24-29 years of diabetes ( p < 0.05). All but one patient developed retinopathy and the first signs were found after 10 years of diabetes.

CONCLUSIONS

Functional disturbances in total skin microcirculation were observed after seven years in patients with type 1 diabetes and preceded diabetic complications such as retinopathy.

Relationships Between Type 2 Diabetes, Neuropathy, and Microvascular Dysfunction: Evidence From Patients With Cryptogenic Axonal Polyneuropathy

OBJECTIVE

This study investigated whether the relationship between neuropathy and microvascular dysfunction in patients with type 2 diabetes is independent of diabetes-related factors. For this purpose, we compared skin microvascular function in patients with type 2 diabetes with that of patients with cryptogenic axonal polyneuropathy (CAP), a polyneuropathy of unknown etiology.

RESEARCH DESIGN AND METHODS

Cross-sectional information was collected from 16 healthy controls (HCs), 16 patients with CAP, 15 patients with type 2 diabetes with polyneuropathy (DPN), and 11 patients with type 2 diabetes without polyneuropathy. Axonal degeneration was assessed with skin biopsy and nerve conduction studies. Microvascular skin vasodilation was measured using laser Doppler fluxmetry combined with iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP).

RESULTS

Patients with CAP and DPN demonstrated a similar decrease in intraepidermal nerve fiber density and sural sensory nerve action potential compared with HCs. The vasodilator response to ACh was similar among patients with CAP (relative mean difference based on log values 13.3%; 95% CI -35.0 to 97.7%; P = 0.652) but was lower in the patients with diabetes with neuropathy (157.5%; 42.0-366.7%; P = 0.003) and without neuropathy (174.2%; 44.2-421.3%; P = 0.003) compared with HCs. No significant differences were found between the groups of patients with diabetes (P = 0.845). The vasodilator response to SNP was not significantly different among the groups (P = 0.082).

CONCLUSIONS

In this study, endothelium-dependent vasodilation was reduced in patients with type 2 diabetes regardless of the presence of polyneuropathy, whereas microvascular vasodilation was normal in patients with CAP. These data suggest that in type 2 diabetes, neuropathy does not contribute to impaired microvascular endothelium-dependent vasodilation and vice versa. In addition, this study suggests that impaired microvascular vasodilation does not contribute to CAP.

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.

Neurovascular microcirculatory vasodilation mediated by C-fibers and Transient receptor potential vanilloid-type-1 channels (TRPV 1) is impaired in type 1 diabetes

Microvascular dysfunction may have an early onset in type 1 diabetes (T1D) and can precede major complications. Our objectives were to assess the endothelial-dependent (acetylcholine, ACh; and post-occlusive hyperemia, PORH), non-endothelial-dependent (sodium nitroprusside, SNP) and neurovascular-dependent (local heating, LH and current induced vasodilation, CIV) microcirculatory vasodilation in T1D patients compared with matched control subjects using a laser speckle contrast imager. Seventeen T1D patients - matched with 17 subjects according to age, gender, Body-Mass-Index, and smoking status - underwent macro- and microvascular investigations. The LH early peak assessed the transient receptor potential vanilloid type 1 channels (TRPV1) mediated vasodilation, whereas the plateau assessed the Nitirc-Oxyde (NO) and endothelium-derived hyperpolarizing factor (EDHF) pathways. PORH explored sensory nerves and (EDHF), while CIV assessed sensory nerves (C-fibers) and prostaglandin-mediated vasodilation. Using neurological investigations, we observed that C-fiber and A-delta fiber functions in T1D patients were similar to control subjects. PORH, CIV, LH peak and plateau vasodilations were significantly decreased in T1D patients compared to controls, whereas there was no difference between the two groups for ACh and SNP vasodilations. Neurovascular microcirculatory vasodilations (C-fibers and TRPV 1-mediated vasodilations) are impaired in TD1 patients whereas no abnormalities were found using clinical neurological investigations. Clinicaltrials: No. NCT02538120.

Assessing the evidence: Exploring the effects of exercise on diabetic microcirculation

Diabetes mellitus (DM) is associated with cardiovascular complications. Impairment of glycemic control induces noxious glycations, an increase in oxydative stress and dearangement of various metabolic pathways. DM leads to dysfunction of micro- and macrovessels, connected to metabolic, endothelial and autonomic nervous system. Thus, assessing vascular reactivity might be one of the clinical tools to evaluate the impact of harmful effects of DM and potential benefit of treatment; skin and skeletal muscle microcirculation have usually been tested. Physical exercise improves vascular dysfunction through various mechanisms, and is regarded as an additional effective treatment strategy of DM as it positively impacts glycemic control, improves insulin sensitivity and glucose uptake in the target tissues, thus affecting glucose and lipid metabolism, and increases the endothelium dependent vasodilation. Yet, not all patients respond in the same way so titrating the exercise type individualy would be desirable. Resistance training has, apart from aerobic one, been shown to positively correlate to glycemic control, and improve vascular reactivity. It has been prescribed in various forms or in combination with aerobic training. This review would assess the impact of different modes of exercise, the mechanisms involved, and its potential positive and negative effects on treating patients with Type I and Type II DM, focusing on the recent literature.

Type 1 diabetes modulates cyclooxygenase- and nitric oxide-dependent mechanisms governing sweating but not cutaneous vasodilation during exercise in the heat

Both cyclooxygenase (COX) and nitric oxide synthase (NOS) contribute to sweating, whereas NOS alone contributes to cutaneous vasodilation during exercise in the heat. Here, we evaluated if Type 1 diabetes mellitus (T1DM) modulates these responses. Adults with (n = 11, 25 ± 5 yr) and without (n = 12, 24 ± 4 yr) T1DM performed two bouts of 30-min cycling at a fixed rate of heat production of 400 W in the heat (35°C); each followed by a 20- and 40-min recovery period, respectively. Sweat rate and cutaneous vascular conductance (CVC) were measured at four intradermal microdialysis sites treated with either 1) lactated Ringer (vehicle control site), 2) 10 mM ketorolac (nonselective COX inhibitor), 3) 10 mM N^G-nitro-l-arginine methyl ester (nonselective NOS inhibitor), or 4) a combination of both inhibitors. In nondiabetic adults, separate and combined inhibition of COX and NOS reduced exercise sweat rate (P ≤ 0.05), and the magnitude of reductions were similar across sites. In individuals with T1DM, inhibition of COX resulted in an increase in sweat rate of 0.10 ± 0.09 and 0.09 ± 0.08 mg ·: min^-1 ·: cm^-2 for the first and second exercise bouts, respectively, relative to vehicle control site (P ≤ 0.05), whereas NOS inhibition had no effect on sweating. In both groups, NOS inhibition reduced CVC during exercise (P ≤ 0.05), although the magnitude of reduction did not differ between the nondiabetic and T1DM groups (exercise 1: -28 ± 10 vs. -23 ± 8% max, P = 0.51; exercise 2: -31 ± 12 vs. -24 ± 10% max, P = 0.38). We show that in individuals with T1DM performing moderate intensity exercise in the heat, NOS-dependent sweating but not cutaneous vasodilation is attenuated, whereas COX inhibition increases sweating.

Abnormalities of vascular structure and function in pediatric hypertension

Hypertension is associated with adverse cardiovascular (CV) events in adults. Measures of vascular structure and function, including increased carotid intima-media thickness (cIMT) and elevated arterial stiffness predict hard CV events in adulthood. Newer data suggest that abnormalities in target organ damage are occurring in adolescents and young adults with high blood pressure. In this review, we discuss the techniques for measuring vascular dysfunction in young people and the evidence linking blood pressure levels to this type of target organ damage.

Acute dairy milk ingestion does not improve nitric oxide-dependent vasodilation in the cutaneous microcirculation

In epidemiological studies, chronic dairy milk consumption is associated with improved vascular health and reduced age-related increases in blood pressure. Although milk protein supplementation augments conduit artery flow-mediated dilation, whether or not acute dairy milk intake may improve microvascular function remains unclear. We hypothesised that dairy milk would increase direct measurement of endothelial nitric oxide (NO)-dependent cutaneous vasodilation in response to local skin heating. Eleven men and women (61 (sem 2) years) ingested two or four servings (473 and 946 ml) of 1 % dairy milk or a rice beverage on each of 4 separate study days. In a subset of five subjects, an additional protocol was completed after 473 ml of water ingestion. Once a stable blood flow occurred, 15 mm-N G -nitro-l-arginine methyl ester was perfused (intradermal microdialysis) to quantify NO-dependent vasodilation. Red-blood-cell flux (RBF) was measured by laser-Doppler flowmetry, and cutaneous vascular conductance (CVC=RBF/mean arterial pressure) was calculated and normalised to maximum (%CVCmax; 28 mm-sodium nitroprusside). Full expression of cutaneous vasodilation was not different among dairy milk, rice beverage and water, and there was no effect of serving size on the total vasodilatory response. Contrary to our hypothesis, NO-dependent vasodilation was lower for dairy milk than rice beverage (D: 49 (sem 5), R: 55 (sem 5) %CVCmax; P<0·01). Acute dairy milk ingestion does not augment NO-dependent vasodilation in the cutaneous microcirculation compared with a rice beverage control.

Exercise and Repeated Testing Improves Accuracy of Laser Doppler Assessment of Microvascular Function Following Shortened (1-minute) Blood Flow Occlusion

OBJECTIVES

To determine whether stability/accuracy of post-occlusive LDF following shortened, one-minute blood flow occlusion, increases in the post-exercise state or by averaging multiple measurements.

METHODS

Six healthy adults (3F) underwent LDF eight times at rest and following exercise, assessing post-occlusive (one-minute occlusion) reactive hyperemia in the cutaneous microcirculation of the forefinger. Measured variables included: pre- and post-occlusion steady-state perfusion (Plat1, Plat2), maximum post-occlusive perfusion (Max), PkT, and the ratio Max/Plat1.

RESULTS

Stability/accuracy of all variables improved performing measurements after exercise (p < 0.05 Plat 1, Plat 2, Max and Max/Plat1). PkT and Max/Plat 1 displayed the greatest accuracy at rest (26.6 ± 5.1% and 26.6 ± 4.4% average difference, %Diff, of single measurements from individual "true" means, respectively); for these variables, %Diff improved to 19.5 ± 5.3 and 17.6 ± 2.1, respectively, following exercise. Overall, averaging multiple measurements performed at rest also improved stability/accuracy in all variables. This improvement was comparable to that obtained with a single measurement following exercise.

CONCLUSIONS

A standardized exercise stimulus prior to testing significantly improves stability/accuracy of LDF following shortened, one-minute blood flow occlusion. Our results suggest the possibilities of broader applications of exercise to optimize measurements from a variety of skin perfusion methodologies.

Prehypertension in adolescents with cardiovascular risk: a comparison between type 1 diabetic patients and overweight subjects

BACKGROUND

Adolescents with type 1 diabetes and obesity present higher cardiovascular risk and ambulatory blood pressure measurements (ABPM) has been shown to predict vascular events, especially by identifying the nondipper status. The aim of our observational cross-sectional study conducted in adolescents with type 1 diabetes, overweight subjects and healthy controls was to assess mean blood pressure parameters to identify subclinical cardiovascular risk.

METHODS

The study included adolescents patients with type 1 diabetes followed in our Pediatric Department in University of Catania between January 2011 and 2013. A total of 60 patients were enrolled, and 48 (32 male and 16 female) completed the study. For each subject we performed systolic and diastolic Ambulatory Blood Pressure Measurements (ABPM) during wakefulness and sleep recording blood pressure every 30 min for 24 h with the Tonoport V/2 GE CardioSoft V6.51 device. We compared the data of patients with those of overweight subjects and healthy controls.

RESULTS

ABPM revealed no significant difference between type 1 diabetic patients and overweight subjects in 24 h Systolic, 24 h Diastolic, Day-time Systolic, Night-time systolic and Day-time Diastolic blood pressure values but significantly different values in Night-time Diastolic blood pressure values (p < 0.001). We found significant differences between type 1 diabetic patients and healthy controls in all 24 h Systolic (p < 0.001), 24 h Diastolic (p < 0.01), Day-time Systolic (p < 0.01), Night-time Systolic (p < 0.001), Day-time Diastolic (p < 0.05) and Night-time Diastolic (p < 0.001) blood pressure values. We detected hypertension in 12/48 (25%) type 1 diabetic patients and in 10/48 overweight subjects (p = 0.62; OR 1.2; CI 0.48-3.29), whereas no-one of healthy controls presented hypertension (p < 0.001). We observed nondipper pattern in 40/48 (83.3%) type 1 diabetic patients, in 33/48 (68.8%) overweight subjects (p = 0.094; OR 2.27; CI 0.85-6.01), and in 16/48 (33.3%) of healthy controls (p < 0.001; OR 10; CI 3.79-26.3).

CONCLUSIONS

ABPM studies might help to define a subset of patients at increased risk for the development of hypertension. In evaluating blood pressure in type 1 diabetes and overweight subjects, ABPM should be used since a reduced dipping can indicate incipient hypertension.

Swimming training attenuates the morphological reorganization of the myocardium and local inflammation in the left ventricle of growing rats with untreated experimental diabetes

Diabetic cardiomyopathy is associated with cardiac remodeling, myocardial dysfunction, low-grade inflammation, and reduced cardiac adiponectin in patients with type 1 diabetes mellitus (T1DM). Alternatively, physical exercise is an important strategy for the management of diabetes. This study aimed to investigate the influence of low-intensity swimming training in cardiac cytokines, structural remodeling, and cardiomyocyte contractile dysfunction in growing rats with untreated experimental DM. Thirty-day-old male Wistar rats were divided into four groups (n=14, per group): sedentary control (SC), exercised control (EC), sedentary diabetic (SD), and exercised diabetic (ED). Diabetes was induced by streptozotocin (60 mg kg(-1), i.p.). Animals from exercised groups swam (5 days/week, 90 min/day, loading up to 5% body weight around the animal's chest) for 8 weeks. The left ventricle (LV) was removed for molecular, morphological, and cardiomyocyte mechanical analysis. Diabetic animals presented cardiac remodeling with myocardial histoarchitectural disorganization, fibrosis, and necrosis. The capillary density was lower in diabetic animals. LV cardiomyocytes from diabetic animals exhibited more prolonged time to the peak of contraction and time to half relaxation than those from control animals. The cardiac levels of interleukin 10, nitric oxide, and total and high molecular weight (HMW) adiponectin were significantly decreased in diabetic animals. Exercise training reduced the level of TNF-α, increased capillary density, and attenuated the histopathological parameters assessed in diabetic rats. In conclusion, the cardiac structural remodeling coexists with reduced levels of total and HMW adiponectin, inflammation, and cardiomyocyte contractility dysfunction in experimental DM. More important, low-intensity swimming training attenuates part of these pathological changes, indicating the beneficial role for exercise in untreated T1DM.

Effects of non-supervised low intensity aerobic excise training on the microvascular endothelial function of patients with type 1 diabetes: a non-pharmacological interventional study

Background

The aim of the present study was to evaluate changes in microvascular density and reactivity in patients with type 1 diabetes (T1D) resulting from low intensity chronic exercise training.

Methods

This study included 22 (34 ± 7 years) consecutive outpatients with T1D and disease duration > 6 years. We used intravital video-microscopy to measure basal skin capillary density and capillary recruitment using post-occlusive reactive hyperemia (PORH) in the dorsum of the fingers. Endothelium-dependent and -independent vasodilation of the skin microcirculation was evaluated in the forearm with a laser Doppler flow monitoring (LDF) system in combination with acetylcholine and sodium nitroprusside iontophoresis, PORH and local thermal hyperemia.

Results

The basal mean capillary density (MCD) after exercise training was significantly higher than before exercise (134 ± 25 vs. 119 ± 19 capillaries/mm², respectively; P = 0.0013). MCD during PORH was also higher after exercise (140 ± 26 vs. 121 ± 24 capillaries/mm², respectively; P < 0.0001). Endothelium-dependent capillary recruitment during PORH was also significantly higher after exercise (140 ± 26 vs. 134 ± 25 capillaries/mm², respectively; P < 0.0012). There were no significant changes in skin microvascular reactivity after exercise as investigated using LDF.

Conclusions

Our results showed that low intensity aerobic exercise, performed four times per week for 12 weeks by patients with T1D, induces significant increases in microvascular density and endothelial-dependent capillary reactivity.

Trial registration

ClinicalTrials.gov NCT02441504. Registered 7 May 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0191-9) contains supplementary material, which is available to authorized users.

Lower-extremity amputation as a marker for renal and cardiovascular events and mortality in patients with long standing type 1 diabetes

Background

We evaluated the risks of renal and cardiovascular complications, and mortality associated with lower extremity amputation (LEA) in patients with type 1 diabetes.

Methods

We studied two cohorts of people with long standing type 1 diabetes: GENEDIAB (n = 456) and GENESIS (n = 611). Subsets of the cohorts (n = 260, n = 544) were followed for 9 and 5 years, respectively. Outcomes were the incidence of end stage renal disease (ESRD), myocardial infarction, stroke and mortality during follow-up. Analyses were performed in pooled cohorts.

Results

The prevalence of LEA at baseline was 9.3 % (n = 99). A positive history of LEA was associated with the baseline prevalence of established (OR 4.50, 95 % CI 2.33–8.91, p < 0.0001) and advanced diabetic nephropathy (OR 5.50, 95 % CI 2.89–10.78, p < 0.0001), ESRD (OR 2.86, 95 % CI 1.43–5.50, p = 0.004), myocardial infarction (OR 3.25, 95 % CI 1.68–6.15, p = 0.0006) and stroke (OR 3.88, 95 % CI 1.67–8.72, p = 0.002, adjusted for sex, age, and cohort membership). A positive history of LEA at baseline was associated with the incidence during follow-up of ESRD (HR 2.69, 95 % CI 1.17–6.20, p = 0.02), and myocardial infarction (HR 3.53, 95 % CI 1.79–6.97, p = 0.0001). History of LEA was also associated with increased risk for all-cause (HR 3.55, 95 % CI 2.05–6.16, p < 0.0001), cardiovascular (HR 3.30, 95 % CI 1.36–8.02, p = 0.008), infectious disease (HR 5.18, 95 % CI 1.13–23.84, p = 0.03) and other-cause mortality (HR 2.81, 95 % CI 1.09–7.26, p = 0.03). History of LEA at baseline was associated with a 40 % reduction in the duration of survival in the subset of patients who died during follow-up. Population attributable risk of the history of LEA at baseline for total mortality during follow-up was 0.31.

Conclusions

Patients with LEA have a higher risk of ESRD, myocardial infarction and cardiovascular and non-cardiovascular mortality. Our results highlight the importance of LEA as a key-predictor for major vascular events and premature death in type 1 diabetic patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0322-0) contains supplementary material, which is available to authorized users.

Body temperature regulation in diabetes

The effects of type 1 and type 2 diabetes on the body's physiological response to thermal stress is a relatively new topic in research. Diabetes tends to place individuals at greater risk for heat-related illness during heat waves and physical activity due to an impaired capacity to dissipate heat. Specifically, individuals with diabetes have been reported to have lower skin blood flow and sweating responses during heat exposure and this can have important consequences on cardiovascular regulation and glycemic control. Those who are particularly vulnerable include individuals with poor glycemic control and who are affected by diabetes-related complications. On the other hand, good glycemic control and maintenance of aerobic fitness can often delay the diabetes-related complications and possibly the impairments in heat loss. Despite this, it is alarming to note the lack of information regarding diabetes and heat stress given the vulnerability of this population. In contrast, few studies have examined the effects of cold exposure on individuals with diabetes with the exception of its therapeutic potential, particularly for type 2 diabetes. This review summarizes the current state of knowledge regarding the impact of diabetes on heat and cold exposure with respect to the core temperature regulation, cardiovascular adjustments and glycemic control while also considering the beneficial effects of maintaining aerobic fitness.