Microvascular autoregulation in children and adolescents with type 1 diabetes mellitus

A 5-Week Guided Active Play Program Modulates Skin Microvascular Reactivity in Healthy Children

PURPOSE

Children's poor levels of physical activity (PA) participation and early-onset vascular aging are identified as global health challenges. Children's guided activity play (GAP)-based PA programs have emerged as effective strategies to improve cardiovascular risk factors and health-related fitness. This study proposes to investigate whether GAP improves children's cutaneous microvascular reactivity and health-related fitness.

METHODS

Children's (n = 18; 9.8 [1.5] y) PA during a 5-week (4 d/wk; 1 h/d) GAP program was assessed (accelerometry) with preassessments and postassessments for anthropometric, musculoskeletal fitness, blood pressure, estimated aerobic power, and cutaneous microvascular reactivity.

RESULTS

PA averaged 556 (132) kcal·week-1 at 34.7% (7.5%) time at moderate to vigorous intensity. Resting heart rate (-9.5%) and diastolic blood pressure (-7.8%) were reduced without changes in health-related fitness indices. Cutaneous microvascular reactivity to sodium nitroprusside iontophoresis increased the average perfusion (+36.8%), average cutaneous vascular conductance (+30%), the area under the curve (+28.8%), and a faster rise phase (+40%) of perfusion (quadratic modeling; P ≤ .05). Chi-square and crosstabulation analysis revealed significant association between children's PA levels and sodium nitroprusside average perfusion levels, where children with PA levels ≥205.1 kcal.55 minute-1 were overrepresented in the medium/high levels of sodium nitroprusside perfusion.

CONCLUSION

A 5-week GAP modified the microvascular reactivity in children without changes in body mass, musculoskeletal fitness, or estimated aerobic power.

The Role of Cutaneous Microcirculatory Responses in Tissue Injury, Inflammation and Repair at the Foot in Diabetes

Diabetic foot syndrome is one of the most costly complications of diabetes. Damage to the soft tissue structure is one of the primary causes of diabetic foot ulcers and most of the current literature focuses on factors such as neuropathy and excessive load. Although the role of blood supply has been reported in the context of macro-circulation, soft tissue damage and its healing in the context of skin microcirculation have not been adequately investigated. Previous research suggested that certain microcirculatory responses protect the skin and their impairment may contribute to increased risk for occlusive and ischemic injuries to the foot. The purpose of this narrative review was to explore and establish the possible link between impairment in skin perfusion and the chain of events that leads to ulceration, considering the interaction with other more established ulceration factors. This review highlights some of the key skin microcirculatory functions in response to various stimuli. The microcirculatory responses observed in the form of altered skin blood flow are divided into three categories based on the type of stimuli including occlusion, pressure and temperature. Studies on the three categories were reviewed including: the microcirculatory response to occlusive ischemia or Post-Occlusive Reactive Hyperaemia (PORH); the microcirculatory response to locally applied pressure such as Pressure-Induced Vasodilation (PIV); and the interplay between microcirculation and skin temperature and the microcirculatory responses to thermal stimuli such as reduced/increased blood flow due to cooling/heating. This review highlights how microcirculatory responses protect the skin and the plantar soft tissues and their plausible dysfunction in people with diabetes. Whilst discussing the link between impairment in skin perfusion as a result of altered microcirculatory response, the review describes the chain of events that leads to ulceration. A thorough understanding of the microcirculatory function and its impaired reactive mechanisms is provided, which allows an understanding of the interaction between functional disturbances of microcirculation and other more established factors for foot ulceration.

Microcirculatory assessment of vascular diseases

The term "microcirculation" refers to the terminal vascular network of the body, which includes arterioles, capillaries, venules as well as initial lymphatic vessels. Additionally, it insinuates to their unique function in thermoregulation, fluid balance, maintenance of cellular exchange, and metabolism. Disturbances of microvascular function were identified to precede macrovascular involvement in the presence of cardiovascular risk factors and is the hallmark of terminal disease stages like critical limb or acral ischemia. Nevertheless, despite its obvious significance in vascular medicine assessment of microvascular function became increasingly neglected in the clinical institutions during the last decades and seems to play a subordinary role in medical education. We therefore provide an overview over relevant and clinically practicable methods to assess microcirculation in vascular medicine with critical estimations of their pros and cons and their perspectives in the future.

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.

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 function in women with former gestational diabetes: A cohort study

OBJECTIVE

In the long term, diabetes mellitus is potentially associated with the occurrence of microvascular damage. This study sought to assess whether a history of prior gestational diabetes mellitus is associated with long-term effects on the women's microcirculation.

METHODS

Within the scope of a long-term follow-up of the 'Viennese Post-Gestational Diabetes Project', women with prior gestational diabetes mellitus as well as women with previous pregnancy but with no history of gestational diabetes mellitus (controls) were enrolled in this cross-sectional study. Microvascular function was assessed by post-occlusive reactive hyperaemia using laser Doppler fluxmetry. Baseline perfusion, biological zero, peak perfusion, time to peak and recovery time were recorded and compared between both groups.

RESULTS

Microvascular function was assessed in 55 women with prior gestational diabetes mellitus (46.1 ± 4.6 years) and 32 women with previous pregnancy but without prior gestational diabetes mellitus (42.9 ± 5.3 years). The mean period of time between delivery and the assessment of microvascular function was 16.2 ± 5.2 years in women with prior gestational diabetes mellitus group and 14.2 ± 4.8 years in controls. Regarding microvascular function, baseline perfusion, biological zero, peak perfusion, time to peak and recovery time did not differ between women with prior gestational diabetes mellitus and controls (all p > 0.05).

CONCLUSION

In the long term, microvascular function appears not to be impaired in women with prior gestational diabetes mellitus.

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 endothelial dysfunction in adolescents and young adults with type 1 diabetes mellitus using a non-invasive heat stimulus

BACKGROUND

Microvascular dysfunction is a key event in the development of atherosclerosis, which predates the clinical manifestations of vascular disease including stroke and myocardial infarction. Dysfunction of the microvasculature can be measured as a decreased microperfusion in response to heat.

OBJECTIVE

We sought to evaluate the microvasculature using heat among adolescents and young adults with type 1 diabetes (T1D) compared to healthy non-diabetic controls. We hypothesized that youth with T1D would have impaired microvascular function measured as decreased perfusion.

METHODS

We studied 181 adolescents and young adults with T1D and 96 age-, race-, and sex-matched healthy controls (mean age 19 yr). Patients were seen at an in-person study visit where demographics, anthropometrics, and laboratory data was obtained. Skin microvascular perfusion was measured on the volvar surface of the right forearm using a standard laser flow Doppler. Measurements were taken at baseline and after heating to 44° C.

RESULTS

Youth with T1D had decreased microvascular perfusion as measured by lower percent change of perfusion units (1870 ± 945 vs. 2539 ± 1255, p < 0.01) and percent change in area under the curve (1870 ± 945 vs. 2539 ± 1255, p < 0.01) compared to controls. Glycosylated hemoglobin A1c (HbA1c) was found to be an independent determinant of microvascular function (p < 0.05).

CONCLUSIONS

Adolescents and young adults with T1D have evidence of microvascular dysfunction that can be detected using heat, a non-invasive physiologic stimulus. HbA1c appears to play an independent role in determining microvascular perfusion suggesting tight glycemic control is probably important for the development of vascular disease.

Holographic laser Doppler imaging of microvascular blood flow

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radio frequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radio frequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.

Impact of age and gender on microvascular function

BACKGROUND

Microcirculatory function can be assessed by postocclusive reactive hyperaemia (PORH) using laser Doppler fluxmetry. Previous studies have shown that PORH reveals microvascular damage at an early stage. In particular, at younger ages, PORH might depend on age and gender. To implement PORH into a larger scale of clinical studies, one has to be aware of the influence of age and gender on microcirculation. The aim of this study was to assess the impact of age and gender on microcirculatory function during adolescence.

MATERIALS AND METHODS

Within the scope of an epidemiological project, 896 children and adolescents underwent assessment of PORH by laser Doppler fluxmetry. Microcirculatory parameters during PORH (baseline perfusion, biological zero, peak perfusion, time to peak perfusion and recovery time) were analysed in relation to age (by tertiles) and gender.

RESULTS

Baseline perfusion, biological zero and peak perfusion were lower in children/adolescents in the upper age tertile (12·3-18·1 years) than in the middle (9·8-12·2 years) and lower (4·3-9·7 years) age tertiles (P < 0·0001). In the total of participants, baseline perfusion, biological zero and peak perfusion were higher in males than in females (P < 0·0001). Analysing microcirculatory parameters as a function of age and gender, the sex differences were only apparent in the upper and the middle age tertiles, but not in the lower.

CONCLUSIONS

During adolescence, PORH is a function of age. At higher age, microvascular reactivity considerably depends on gender, whereas no sex differences are present at younger ages.

Impaired skin microcirculation in paediatric patients with type 1 diabetes mellitus

Aims/hypothesis

We used Laser Doppler Fluximetry (LDF) to define "normal" endothelial function in a large cohort of healthy children and adolescents and to evaluate skin microcirculation in paediatric patients with type 1 diabetes mellitus.

Methods

LDF was performed in 102 healthy children (12.8 ± 3.3 years of age; 48 male) and 68 patients (12.9 ± 3.3 years of age; 33 male). Duration of disease was 5.0 ± 3.97 years. Each participant sequentially underwent three stimulation protocols (localized thermal hyperaemia with localized warming to maximum 40°C, iontophoretic delivery of pilocarpine hydrochloride (PCH) and sodium nitroprusside (SNP)). The maximum relative increase in skin blood flow and the total relative response, i.e. the area under the curve (AUC) to each stimulus (AUC_heat, AUC_PCH, AUC_SNP) was determined. In addition, the area of a right-angled triangle summarizing the time to and the amplitude of the first peak, which represents the axon reflex mediated neurogenic vasodilation (ARR) was calculated.

Results

In healthy controls, AUC_heat, AUC_PCH, AUC_SNP, and ARR turned out to be independent of sex, age, and anthropometric values. Per parameter the 10th percentile generated from data of healthy controls was used as the lower threshold to define normal endothelial function. Diabetic patients showed significantly reduced vasodilatative response to either physical or pharmacological stimulation with SNP, whereas the response to PCH was comparable in both cohorts. In patients compared to controls i) a significantly higher frequency of impaired vasodilatation in response to heat and SNP was noted and ii) vascular response was classified as pathological in more than one of the parameters with significantly higher frequency.

Conclusions/interpretation

Skin microvascular endothelial dysfunction is already present in about 25% of paediatric type 1 diabetic patients suffering from type 1 diabetes for at least one year. Future studies are needed to assess the predictive value of endothelial dysfunction in the development of long-term (cardio)vascular comorbidity in these patients.

Endothelial progenitor cells are related to glycemic control in children with type 1 diabetes over time

OBJECTIVE

The risk of cardiovascular death before the age of 40 is 20-fold higher in patients with type 1 diabetes mellitus (T1DM). Endothelial progenitor cells (EPCs) predict cardiovascular morbidity and mortality in patients without diabetes. We hypothesized that EPCs are modified in children with T1DM and are related to characteristics of T1DM such as glycemic control.

RESEARCH DESIGN AND METHODS

Children (n = 190; 156 T1DM subjects and 34 control subjects) were included in an observational cohort study and matched for age and sex. EPCs were enumerated by flow cytometry at the beginning (cross-sectional) and 1 year later (longitudinal). To analyze changes of variables during the observation, Δ values were calculated.

RESULTS

EPCs were significantly reduced in T1DM children versus control subjects (609 ± 359 vs. 1,165 ± 484, P < 0.001). Multivariate regression modeling revealed that glycated hemoglobin A1c (HbA1c) was the strongest independent predictor of EPCs (β = -0.355, P < 0.001). Overall glycemic control at the beginning and end of study did not differ (7.8 ± 1.2 vs. 7.8 ± 1.2 relative %, P = NS), but we observed individual HbA1c changes of -4.30/+3.10 relative %. The strongest EPC increase was observed in the patients with the most favorable HbA1c lowering during the 1-year follow-up. Accordingly, the strongest EPC decrease was demonstrated in the patients with the strongest HbA1c worsening during the time period.

CONCLUSIONS

This is the first prospective study demonstrating diminished EPCs in children with T1DM. The association of better glycemic control with an increase in EPC numbers within 1 year suggests that a reduction of the high cardiovascular disease burden might be mediated likewise.

Familial hypercholesterolemia affects microvascular autoregulation in children

OBJECTIVE

Familial hypercholesterolemia (FH) impairs macrovascular endothelial function in childhood and causes an increase of cardiovascular risk in later life. Whether microvascular function is affected in children with FH is unknown. The aim of this study was to investigate the impact of FH on microvascular autoregulation in children by post occlusive reactive hyperemia (PORH).

METHODS

PORH of the skin was assessed using laser Doppler fluxmetry. Baseline perfusion, biological zero, defined as no-flow laser Doppler signal during suprasystolic occlusion, peak perfusion after release of suprasystolic occlusion, as well as time to peak perfusion and recovery time, defined as time until baseline perfusion is resumed, were measured in 16 children, who were diagnosed with FH according to current guidelines, and in 91 healthy controls.

RESULTS

In children with FH, peak perfusion was higher (FH: 1.60±0.68 vs. controls: 1.26±0.50 AU [arbitrary units], p=0.02), recovery time was longer (110±42.61 vs. 83.18±35.08 s, p=0.01) and biological zero was lower than in controls (0.12±0.04 vs. 0.18±0.05 AU, p<0.001). Baseline perfusion and time to peak were not different between children with FH and controls (baseline perfusion: 0.43±0.21 vs. 0.38±0.15 AU, p=0.18; time to peak: 15.44±12.25 vs. 18.18±17.79 s, p=0.56).

CONCLUSION

For the first time the present study reveals an impact of FH on microvascular autoregulation in children: the differences of PORH between children with FH and controls indicate an affected autoregulation of microvascular blood flow in FH, which has its onset in childhood.