Microvascular function relates to insulin sensitivity and blood pressure in normal subjects

Impacts of Physical Inactivity Models on Endothelial Function: A Systematic Review

BACKGROUND

Endothelial dysfunction is associated with cardiovascular disease and cardiac events. Numerous studies demonstrate that a reduction in physical activity/exercise levels are associated with poor endothelial function. Yet, these studies use a plethora of models to mimic reduced activity levels which may have widely different results on endothelial function. It is pertinent to collectively review these articles to provide a comprehensive understanding of the impact of reduced activity on vascular health, as endothelial function is one of many factors that influences vascular tone.

OBJECTIVE

The purpose of this systematic review is to examine and synthesize the current literature regarding the effects of acutely (≤ ~ 2 months) reducing physical activity on endothelial function.

METHODS

This systematic review contains a search of two databases (PubMed, Web of Science) conducted by two reviewers. After screening and review, the search yielded 20 studies that were appraised and reviewed.

RESULTS

Articles were separated into four categories based on the type of inactivity intervention: reduction in daily physical activity interventions, detraining (removal of exercise) interventions, bed rest interventions, and immobilization interventions. Acute physical inactivity interventions were largely shown to reduce upper and lower limb artery flow-mediated dilation and lower limb microvascular function.

CONCLUSION

The results indicate that those studies with increased time spent in inactivity, as well as increased severity of inactivity, were more likely to have negative endothelial function outcomes. Future research should examine differences in the severity of physical inactivity interventions regarding endothelial function.

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.

Diabetic microvascular disease in non-classical beds: the hidden impact beyond the retina, the kidney, and the peripheral nerves

Diabetes microangiopathy, a hallmark complication of diabetes, is characterised by structural and functional abnormalities within the intricate network of microvessels beyond well-known and documented target organs, i.e., the retina, kidney, and peripheral nerves. Indeed, an intact microvascular bed is crucial for preserving each organ's specific functions and achieving physiological balance to meet their respective metabolic demands. Therefore, diabetes-related microvascular dysfunction leads to widespread multiorgan consequences in still-overlooked non-traditional target organs such as the brain, the lung, the bone tissue, the skin, the arterial wall, the heart, or the musculoskeletal system. All these organs are vulnerable to the physiopathological mechanisms that cause microvascular damage in diabetes (i.e., hyperglycaemia-induced oxidative stress, inflammation, and endothelial dysfunction) and collectively contribute to abnormalities in the microvessels' structure and function, compromising blood flow and tissue perfusion. However, the microcirculatory networks differ between organs due to variations in haemodynamic, vascular architecture, and affected cells, resulting in a spectrum of clinical presentations. The aim of this review is to focus on the multifaceted nature of microvascular impairment in diabetes through available evidence of specific consequences in often overlooked organs. A better understanding of diabetes microangiopathy in non-target organs provides a broader perspective on the systemic nature of the disease, underscoring the importance of recognising the comprehensive range of complications beyond the classic target sites.

Hamid A, Ugusman A. Effects of Piper sarmentosum Roxb. on hypertension and diabetes mellitus: A systematic review and meta-analysis

Hypertension and diabetes mellitus are among the most prevalent diseases affecting people from all walks of life. Medicinal herbs have garnered interest as potential agents for the prevention and treatment of diabetes mellitus and hypertension due to their multiple beneficial effects. Piper sarmentosum Roxb. (PS) is an edible medicinal plant that has been traditionally used in Asia for treating hypertension and diabetes mellitus. This review is aimed to provide comprehensive information from the literature on the effects of PS on hypertension and diabetes mellitus. A computerized database search was performed on Scopus, PubMed and Web of Science databases with the following set of keywords: Piper sarmentosum AND diabetes mellitus OR diabetic OR diabetes OR hyperglyc*emia OR blood glucose OR HbA1c OR glycated h*emoglobin OR h*emoglobin A1c OR hyperten* OR blood pressure. A total of 47 articles were screened and 14 articles published between the years 1998 until 2021 were included for data extraction, comprising of six articles on antihypertensive and eight articles on antidiabetic effects of PS. These studies consist of two in vitro studies and eleven in vivo animal studies. Meta-analysis of three studies on hypertension showed that PS versus no treatment significantly lowered the systolic blood pressure with mean difference (MD) -39.84 mmHg (95% confidence interval (CI) -45.05, -34.62; p < 0.01), diastolic blood pressure with MD -26.68 mmHg (95% CI -31.48, -21.88; p < 0.01), and mean arterial pressure with MD -30.56 mmHg (95% CI -34.49, -26.63; p < 0.01). Most of the studies revealed positive effects of PS against hypertension and diabetes mellitus, suggesting the potential of PS as a natural source of antidiabetic and antihypertensive agents.

Role of Caveolae in the Development of Microvascular Dysfunction and Hyperglycemia in Type 2 Diabetes

In type 2 diabetes (T2D) microvascular dysfunction can interfere with tissue glucose uptake thereby contributing to the development of hyperglycemia. The cell membrane caveolae orchestrate signaling pathways that include microvascular control of tissue perfusion. In this study, we examined the role of caveolae in the regulation of microvascular vasomotor function under the condition of hyperglycemia in T2D patients and rodent models. Human coronary arterioles were obtained during cardiac surgery from T2D patients, with higher perioperative glucose levels, and from normoglycemic, non-diabetic controls. The coronary arteriole responses to pharmacological agonists bradykinin and acetylcholine were similar in T2D and non-diabetic patients, however, exposure of the isolated arteries to methyl-β-cyclodextrin (mβCD), an agent known to disrupt caveolae, reduced vasodilation to bradykinin selectively in T2D subjects and converted acetylcholine-induced vasoconstriction to dilation similarly in the two groups. Dilation to the vascular smooth muscle acting nitric oxide donor, sodium nitroprusside, was not affected by mβCD in either group. Moreover, mβCD reduced endothelium-dependent arteriolar dilation to a greater extent in hyperglycemic and obese db/db mice than in the non-diabetic controls. Mechanistically, when fed a high-fat diet (HFD), caveolin-1 knockout mice, lacking caveolae, exhibited a significantly reduced endothelium-dependent arteriolar dilation, both ex vivo and in vivo, which was accompanied by significantly higher serum glucose levels, when compared to HFD fed wild type controls. Thus, in T2D arterioles the role of caveolae in regulating endothelium-dependent arteriole dilation is altered, which appears to maintain vasodilation and mitigate the extent of hyperglycemia. While caveolae play a unique role in microvascular vasomotor regulation, under the condition of hyperglycemia arterioles from T2D subjects appear to be more susceptible for caveolae disruption-associated vasomotor dysfunction and impaired glycemic control.

Microvessel Density: Integrating Sex-Based Differences and Elevated Cardiovascular Risks in Metabolic Syndrome

Metabolic syndrome (MetS) is a complex pathological state consisting of metabolic risk factors such as hypertension, insulin resistance, and obesity. The interconnectivity of cellular pathways within various biological systems suggests that each individual component of MetS may share common pathological sources. Additionally, MetS is closely associated with vasculopathy, including a reduction in microvessel density (MVD) (rarefaction) and elevated risk for various cardiovascular diseases. Microvascular impairments may contribute to perfusion-demand mismatch, where local metabolic needs are insufficiently met due to the lack of nutrient and oxygen supply, thus creating pathological positive-feedback loops and furthering the progression of disease. Sexual dimorphism is evident in these underlying cellular mechanisms, which places males and females at different levels of risk for cardiovascular disease and acute ischemic events. Estrogen exhibits protective effects on the endothelium of pre-menopausal women, while androgens may be antagonistic to cardiovascular health. This review examines MetS and its influences on MVD, as well as sex differences relating to the components of MetS and cardiovascular risk profiles. Finally, translational relevance and interventions are discussed in the context of these sex-based differences.

Resistive index of ophthalmic artery as an imaging biomarker of hypertension-related vascular and kidney damage

Aim: Resistive index of ophthalmic artery (RI-OA) is associated with atherosclerotic diseases. The aim of this study was to evaluate the association of RI-OA and hypertension-related vascular and kidney damage. Materials and methods: Two-hundred and eighty hypertensive patients underwent evaluation of RI-OA, carotid atherosclerosis and level of 24 h albuminuria. Results: Albuminuria and carotid atherosclerosis were positively associated with RI-OA independently of other cardiovascular risk factors. Receiver-operating characteristic curve analysis allowed us to calculate a cut-off value of RI-OA >0.625, which would be suspicious about the existence of atherosclerotic disease. Conclusion: The ophthalmic vascular circulation allows to study connections between macro- and microcirculation in vivo. RI-OA could be a useful marker for a better stratification of the risk of developing kidney and cardiovascular disease.

Skin oxygenation impairment is associated with increased total cholesterol level in children with short-lasting type 1 diabetes mellitus

INTRODUCTION

Transcutaneous oxygen pressure (tcPO2) is a non-invasive method of measuring skin oxygenation that may reflect its superficial perfusion. Skin microvasculature may be impaired in patients with late onset of type 1 diabetes (DM1). However, its condition in children has not been fully determined.

AIM

To compare tcPO2 in children with short-lasting non-complicated DM1 and age-matched healthy controls with regard to concomitant vascular risk factors.

MATERIAL AND METHODS

The study group consisted of 51 paediatric patients aged 14.9 (8.4-18.0) years with short-lasting DM1 without clinical evidence of diabetic micro- or macroangiopathy and 28 control subjects aged 14.8 (11.3-17.7) years. TcPO2 was tested prior, during and after applying post-occlusive reactive hyperaemia (PORH) test in standardized conditions. Biochemical parameters were assessed and then compared between the groups.

RESULTS

TcPO2 at maximal ischemia during PORH was higher in the DM1 patients than in healthy controls (2.4 (0.7-18.8) vs. 1.6 (0.4-12.0), p = 0.002). No differences were found regarding the tcPO2 measurements recorded prior to ischemia or after recovery. In DM1, concentrations of total cholesterol, triglycerides, HbA1c and TSH were significantly higher than in healthy controls. The fT4 levels were significantly lower in the DM1 group. After adjusting for lipid levels, no differences in tcPO2 were found, and a multivariate analysis showed the cholesterol levels have a significant impact on tcPO2 response to maximal ischemia.

CONCLUSIONS

Our results indicate that increased lipid levels are responsible for the impaired skin response to ischemic stimuli in short-lasting DM1. This supports the importance of aggressive lipid control in prevention of early onset microangiopathy in those patients.

Obesity-Related Inflammation and Endothelial Dysfunction in COVID-19: Impact on Disease Severity

The coronavirus disease 2019 (COVID-19) pandemic has put into evidence another pandemic – obesity. Currently, several studies have documented the association between obesity and COVID-19 severity. The mechanisms underlying the increased risk of complications and mortality in obese patients with COVID-19 are of diverse nature. Inflammation plays a central role in obesity. Metabolic alterations seen in obese patients are related to an inflammatory response, and several studies report elevated levels of circulating inflammatory cytokines in obese patients. Also, deregulated expression of adipokines, such as leptin and resistin, increase the expression of vascular adhesion molecule 1 and intercellular adhesion molecule 1 that contribute to increased vascular leukocyte adhesiveness and additional oxidative stress. Additionally, it is now recognized that the chronic impairment of systemic vascular endothelial function in patients with cardiovascular and metabolic disorders, including obesity, when intensified by the detrimental effects of SARS-CoV-2 over the endothelium, may explain their worse outcomes in COVID-19. In fact, vascular endothelial dysfunction may contribute to a unfavorable response of the endothelium to the infection by SARS-CoV-2, whereas alterations in cardiac structure and function and the prothrombotic environment in obesity may also provide a link to the increased cardiovascular events in these patients.

The Relation between Body Mass Index and Retinal Photoreceptor Morphology and Microvascular Changes Measured with Adaptive Optics (rtx1) High-Resolution Imaging

Background

Overweight and obese patients are at risk for diabetes, cardiovascular disorders, and microvascular complications. The rtx1^TM (Imagine Eyes, France) is a microscope that allows near histological visualizations of cones and retinal microcirculation.

Objective

This study analysed the cones and retinal microvascular changes in a group of 47 healthy women with different BMI values. Participants were divided into 2 groups: the BMI group (28 women with BMI >/25) and the control group (19 lean women with BMI <25).

Results

The lumen and diameter of retinal arteries were not significantly different between groups. There were significant differences in the thickness of arteriole walls. The WLR and WCSA values differed significantly between the control and BMI groups (for WLR 0.25 ± 0.03 vs. 0.29 ± 0.03, p < 0.001; for WCSA 4136.7 ± 1140.0 vs. 5217.3 ± 944.0, respectively, p < 0.001). In healthy eyes, cone density and morphology were not affected by weight.

Conclusions

Retinal image analysis with rtx1 offers a novel noninvasive measurement of early changes in retinal vasculature that are not detectable during routine clinical examination. Abnormalities of retinal arterioles found by rtx1™examination should be considered as a strong risk factor for cardiovascular changes resulting from overweight and obesity.

Postpartum microvascular functional alterations following severe preeclampsia

Preeclampsia is associated with adverse maternal health outcomes later in life. Vascular endothelial dysfunction has been previously described following preeclampsia. We hypothesized that microvascular endothelial dysfunction associated with preeclampsia persists postpartum and may identify those at greatest risk of future cardiovascular disease. The objective of this study was to examine postpartum microvascular endothelial function in women after a pregnancy complicated by preeclampsia. Women with previous preeclampsia (n = 30) and normotensive controls (n = 30) between 6 mo and 5 yr postpartum were recruited. Severity of preeclampsia [severe (n = 16) and mild (n = 14)] was determined by standardized chart review. Microvascular reactivity in the forearm was measured with laser speckle contrast imaging, coupled with iontophoresis; endothelium-dependent and endothelium-independent vasodilation was induced with 1% acetylcholine and sodium nitroprusside solutions, respectively. A postocclusive reactive hyperemia test assessed vasodilatory response following three minutes of suprasystolic (200 mmHg) occlusion with a mechanized cuff. Women with prior severe preeclampsia exhibited significantly higher vasodilation to acetylcholine and sodium nitroprusside compared to controls (P < 0.01; P = 0.03) and prior mild preeclampsia (P = 0.03; P < 0.01). Neither the degree of postocclusive reactive hyperemia (P = 0.98), nor time to return halfway to baseline [OR = 1.026 (0.612, 1.72); P = 0.92], differed between preeclampsia and controls. In conclusion, severe preeclampsia is associated with heightened postpartum microvascular endothelium-dependent and endothelium-independent vasoreactivity. These changes, or a common antecedent, may be linked to postpartum alterations in vascular function that predispose women to disease after preeclampsia. Further investigation should identify the contributing mechanism and the degree to which it could be amenable to medical intervention.NEW & NOTEWORTHY We examine maternal microvascular function after preeclampsia, identifying heightened endothelium-dependent and endothelium-independent microvascular reactivity following severe disease. Our study represents a noteworthy addition to the existing literature with the use of a novel imaging modality, vascular perturbation, postpartum time point, and patient population with differentiation of preeclampsia into severe and nonsevere subtypes. These results represent a novel addition to the growing clinical and academic understanding of maternal health outcomes following preeclampsia.

Greater Lower Limb Fatigability in People with Prediabetes than Controls

INTRODUCTION

The study purpose was to compare perceived fatigability and performance fatigability after high-velocity contractions with knee extensor muscles between people with prediabetes, people with type 2 diabetes (T2D), and controls without diabetes matched for age, body mass index, and physical activity.

METHODS

Twenty people with prediabetes (11 men, 9 women: 63.1 ± 6.0 yr, 26.9 ± 4.2 kg·m, 8030 ± 3110 steps per day), 39 with T2D (23 men, 16 women: 61.2 ± 8.5 yr, 29.4 ± 6.4 kg·m, 8440 ± 4220 steps per day), and 27 controls (13 men, 14 women: 58.1 ± 9.4 yr, 27.3 ± 4.3 kg·m, 8400 ± 3000 steps per day) completed the Fatigue Impact Scale as a measure of perceived fatigability and a fatigue protocol including 120 maximal-effort, high-velocity concentric contractions (MVCC; 1 contraction/3 s) with the knee extensors using a submaximal load (30% maximum) to quantify performance fatigability. Electrical stimulation was used to assess voluntary activation and contractile function of the knee extensor muscles before and after the fatigue protocol.

RESULTS

Fatigue Impact Scale scores were not different between people with prediabetes, people with T2D, and controls (12.5 ± 15.1, 18.3 ± 22.7, and 12.6 ± 18.6, respectively; P = 0.517). However, people with prediabetes had greater reductions in MVCC power during the fatigue protocol than did controls (31.8% ± 22.6% vs 22.1% ± 21.1%, P < 0.001), and both groups had lesser reductions than the T2D group (44.8% ± 21.9%, P < 0.001). Similarly, the prediabetes group had larger reductions in electrically evoked twitch amplitude than the control group (32.5% ± 24.9% vs 21.3% ± 33.0%, P < 0.001), but lesser reductions than those with T2D (44.0% ± 23.4%, P < 0.001). For all three groups, a greater decline in MVCC power was associated with larger reductions of twitch amplitude (r = 0.350, P < 0.001).

CONCLUSION

People with prediabetes have greater performance fatigability of the knee extensors due to contractile mechanisms compared with controls, although less performance fatigability than that of people with T2D.

Differential Effect of the Metabolic Syndrome on the Incidence of Retinal Vein Occlusion in the Korean Population: A Nationwide Cohort Study

Purpose

To investigate the impact of the metabolic syndrome (METS) on the incidence of retinal vein occlusion (RVO).

Methods

This is a retrospective cohort study using Korean National Health Insurance System data. 23,153,600 subjects without previous history of RVO underwent a National Health Screening Program examination between 2009 and 2012. They were monitored for RVO development (registration of diagnostic code for RVO) until 2015. Presence of METS was defined using the data from the National Health Screening Program examination according to the revised criteria of the National Cholesterol Education Program Adult Treatment Panel III. A multivariate adjusted Cox regression analysis was used to reveal hazard ratios and 95% confidence interval for RVO development in the presence of METS.

Results

The age of the subjects was 47.64 ± 13.51 years. In this cohort, 11,747,439 (50.7%) were male, 11,406,161 (49.3%) were female, and 6,398,071 subjects (27.6%) were diagnosed with METS. The overall incidence of RVO was 0.947 per 1000 person-years. The adjusted hazard ratio of RVO in the presence of METS was 1.458 (95% confidence interval, 1.440–1.475; P < 0.001) after adjusting for age, sex, smoking status, alcohol consumption, physical activity, and income. Among all of the criteria for METS diagnosis, elevated blood pressure was the greatest risk for RVO development (adjusted hazard ratio, 1.610; 95% confidence interval, 1.589–1.631; P < 0.001).

Conclusions

METS and each of diagnostic criteria was associated with an increased risk of RVO development. Elevated blood pressure seems to be especially important factors for RVO development.

Translational Relevance

Our results provide information about the link between METS and RVO.

Tribbles Homolog 3-Mediated Vascular Insulin Resistance Contributes to Hypoxic Pulmonary Hypertension in Intermittent Hypoxia Rat Model

This study aimed to investigate the role of vascular insulin resistance (VIR) and Tribbles homolog 3 (TRIB3) in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH). Rats were subjected to low air pressure and low oxygen intermittently for 4 weeks to induce HPH. The mean right ventricular pressure (mRVP), mean pulmonary arterial pressure (mPAP), and right ventricular index (RVI) were significantly increased in HPH rats. Pulmonary arteries from HPH rats showed VIR with reduced vasodilating effect of insulin. The protein levels of peroxisome proliferator-activated receptor gamma (PPARγ), phosphoinositide 3-kinase (PI3K), phosphorylations of Akt, and endothelial nitric oxide (NO) synthase (eNOS) were decreased, and TRIB3 and phosphorylated extracellular signal-regulated protein kinases (ERK1/2) were increased in pulmonary arteries of HPH rats. Early treatment of pioglitazone (PIO) partially reversed the development of HPH, improved insulin-induced vasodilation, and alleviated the imbalance of the insulin signaling. The overexpression of TRIB3 in rat pulmonary arterial endothelial cells (PAECs) reduced the levels of PPARγ, PI3K, phosphorylated Akt (p-Akt), and phosphorylated eNOS (p-eNOS) and increased p-ERK1/2 and the synthesis of endothelin-1 (ET-1), which were further intensified under hypoxic conditions. Moreover, TRIB3 knockdown caused significant improvement in Akt and eNOS phosphorylations and, otherwise, a reduction of ERK1/2 activation in PAECs after hypoxia. In conclusion, impaired insulin-induced pulmonary vasodilation and the imbalance of insulin-induced signaling mediated by TRIB3 upregulation in the endothelium contribute to the development of HPH. Early PIO treatment improves vascular insulin sensitivity that may help to limit the progression of hypoxic pulmonary hypertension.

Influence of Macitentan on the Vascular Tone and Recruitment of Finger Capillaries Under Hypobaric Hypoxia in High Altitude

Betge, Stefan, Stefan Drinda, Thomas Neumann, Laura Bäz, Alexander Pfeil, Christian Schulze, Ralf Mrowka, Christian Jung, and Marcus Franz. Influence of macitentan on the vascular tone and recruitment of finger capillaries under hypobaric hypoxia in high altitude. High Alt Med Biol. 21:336-345, 2020. Introduction: Acute normobaric (NH) and hypobaric hypoxia (HH) has effects on the vascular tone of larger arteries and may have effects on the microcirculation. These effects may be noninvasively detectable by automated devices. A part of these effects may be mediated by endothelin (ET) and should be influenced by macitentan (MAC), a dual endothelin receptor antagonist (ERA). Methods: We used photoplethysmographic sensors, fingertip volume sensors, nailfold capillaroscopy, and laser Doppler probes at rest and after a 5-minute forearm ischemia in healthy study subjects under NH, under HH, and under HH plus a single dose of MAC. Results: NH at simulated 4000 m led to increased heart rates (HR) and pulse wave velocities (PWV) and reduced augmentation index (AIX). The values for the AIX showed a high SD and differed between the used devices. At simulated 5500 m, only baseline mean value (BMV; EndoPAT) showed a further change, indicating less filled capillaries of the fingertips. HH (2978 m) increased HR, blood pressure values, and PWV. Focusing on the microcirculation of the fingertips, HH reduced the BMV and the nailfold capillary density and the postischemic capillary recruitment. MAC had no effect on the BMV, but antagonized the effects of HH on the nailfold capillaries and led to a strongly increased postischemic diameter of the arterial limbs. Concordantly, the postischemic blood flow velocity increment, measured through ultrasound Doppler, was increased at ALT+MAC. Conclusions: The BMV may be a parameter for changes of the microcirculation of the finger tips. A single dose of MAC blocked hypoxia-induced capillary rarefaction and enhanced postischemic hyperemia of the fingertips. These results indicate the importance of ET-1 for the regulation of the microcirculation under hypoxia. The German Registry of Clinical Studies (DRKS) ID: 00005459.

Degree of Blood Pressure Control and Incident Diabetes Mellitus in Chinese Adults With Hypertension

Background

The association between blood pressure (BP) control and incident diabetes mellitus remains unknown. We aim to investigate the association between degree of time‐averaged on‐treatment systolic blood pressure (SBP) control and incident diabetes mellitus in hypertensive adults.

Methods and Results

A total of 14 978 adults with hypertension without diabetes mellitus at baseline were included from the CSPPT (China Stroke Primary Prevention Trial). Participants were randomized double‐masked to daily enalapril 10 mg and folic acid 0.8 mg or enalapril 10 mg alone. BP measurements were taken every 3 months after randomization. The primary outcome was incident diabetes mellitus, defined as physician‐diagnosed diabetes mellitus, or use of glucose‐lowering drugs during follow‐up, or fasting glucose ≥126 mg/dL at the exit visit. Over a median of 4.5 years, a significantly higher risk of incident diabetes mellitus was found in participants with time‐averaged on‐treatment SBP 130 to <140 mm Hg (10.3% versus 7.4%; odds ratio [OR], 1.37; 95% CI, 1.15‒1.64), compared with those with SBP 120 to <130 mm Hg. Moreover, the risk of incident diabetes mellitus increased by 24% (OR, 1.24; 95% CI, 1.00‒1.53) and the incidence of regression to normal fasting glucose (<100 mg/dL) decreased by 29% (OR, 0.71; 95% CI, 0.57‒0.89) in participants with intermediate BP control (SBP/diastolic blood pressure, 130 to <140 and/or 80 to <90 mm Hg), compared with those with a tight BP control of <130/<80 mm Hg. Similar results were found when the time‐averaged BP were calculated using the BP measurements during the first 6‐ or 24‐month treatment period, or in the analysis using propensity scores.

Conclusions

In this non‐diabetic, hypertensive population, SBP control in the range of 120 to <130 mm Hg, compared with the 130 to <140 mm Hg, was associated with a lower risk of incident diabetes mellitus.

Titrating Growth Hormone Dose to High-Normal IGF-1 Levels Has Beneficial Effects on Body Fat Distribution and Microcirculatory Function Despite Causing Insulin Resistance

To clarify the mechanism underlying the described U-shaped relation of both low and high levels of IGF-1 with cardiovascular disease this study explores the effect of decreasing and increasing growth hormone dose in GH deficient adults on (micro)vascular function, body composition and insulin resistance. In this randomized clinical trial, thirty-two subjects receiving GH therapy with an IGF-1 concentration between -1 and 1 SD score (SDS) for at least one year were randomized to receive either a decrease (IGF-1 target level of -2 to -1 SDS) or an increase of their daily GH dose (IGF-1 target level of 1 to 2 SDS) for a period of 24 weeks. Microvascular endothelium (in)dependent vasodilatation and vasomotion, vascular stiffness by pulse wave analysis, and HOMA-IR were measured. At the end of the study 30 subjects (65.6% men, mean age 46.6 (SD 9.9) years) were analyzed. There was a favorable effect of increasing the IGF-1 level on waist circumference compared to decreasing the IGF-1 level (p=0.05), but a detrimental effect on insulin resistance (p=0.03). Decreasing IGF-1 level significantly lowered the endothelial domain of vasomotion (p=0.03), whereas increasing IGF-1 level increased the contribution of the neurogenic domain (p=0.05). This change was related to the favorable change in waist circumference. In conclusion, increasing IGF-1 levels was beneficial for body composition but detrimental with respect to insulin resistance. The contribution of the neurogenic vasomotion domain increased in parallel, and could be explained by the favorable change in waist circumference.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT01877512.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

Microcirculatory Improvement Induced by Laparoscopic Sleeve Gastrectomy Is Related to Insulin Sensitivity Retrieval

AIMS

Microvascular dysfunction is a potential factor explaining the association of obesity, insulin resistance, and vascular damage in morbidly obese subjects. The purpose of the study was to evaluate possible determinants of microcirculatory improvement 1 year after laparoscopic sleeve gastrectomy (LSG) intervention.

METHODS

Thirty-seven morbidly obese subjects eligible for bariatric surgery were included in the study. Post-occlusive reactive hyperemia (PORH) of the forearm skin was measured as area of hyperemia (AH) by laser-Doppler flowmetry before LSG and after a 1-year follow-up.

RESULTS

After intervention, we observed a significant reduction in BMI, HOMA index, HbA1c, and a significant increase of AH in all patients after surgery; this variation was significant only in those patients having insulin resistance or prediabetes/diabetes. Although significant correlation between the increase of AH and the reduction of both BMI, HOMA index, and HbA1c was observed, BMI was the only independent predictor of AH variation after LSG at the linear regression analysis.

CONCLUSIONS

Our study shows that LSG intervention is correlated with a significant improvement in the microvascular function of morbidly obese subjects; this improvement seems to be related to the baseline degree of insulin-resistance and to the retrieval of insulin-sensitivity post-intervention.

The presence of cerebral white matter lesions and lower skin microvascular perfusion predicts lower cognitive performance in type 1 diabetes patients with retinopathy but not in healthy controls-A longitudinal study

OBJECTIVE

Cognitive impairments in type 1 diabetes may result from hyperglycemia-associated cerebral microangiopathy. We aimed to identify cerebral microangiopathy and skin microvascular dysfunction-as a surrogate marker for generalized microvascular function-as predictors of cognitive performance over time.

METHODS

In this prospective cohort study, 25 type 1 diabetes patients with proliferative retinopathy and 25 matched healthy controls underwent neurocognitive testing at baseline and after follow-up (3.8 ± 0.8 years). At baseline, 1.5-T cerebral magnetic resonance imaging was used to detect WML and cerebral microbleeds. Skin capillary perfusion was assessed by means of capillary microscopy.

RESULTS

In type 1 diabetes patients, but not in healthy controls, the presence of WML (ß = -0.419; P = 0.037) as well as lower skin capillary perfusion (baseline: ß = 0.753; P < 0.001; peak hyperemia: ß = 0.743; P = 0.001; venous occlusion: ß = 0.675; P = 0.003; capillary recruitment: ß = 0.549; P = 0.022) at baseline was associated with lower cognitive performance over time, independent of age, sex, HbA1c, and severe hypoglycemia. The relationship between WML and lower cognitive performance was significantly reduced after adjusting for capillary perfusion.

CONCLUSIONS

These data fit the hypothesis that cerebral microangiopathy is a manifestation of generalized microvascular dysfunction, leading to lower cognitive performance.

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.

Risk of developing type 2 diabetes according to blood pressure levels and presence or absence of hypertensive treatment: the Saku study

The aim was to investigate the risk of developing type 2 diabetes according to blood pressure (BP) levels and presence or absence of hypertensive treatment. This 5-year cohort study comprised 3508 Japanese adults aged 30-74 years without diabetes who had undergone a medical checkup including a 75-g oral glucose tolerance test (OGTT) between April 2008 and March 2009 at Saku Central Hospital. Participants receiving antihypertensive treatment were categorized into controlled hypertension ( < 140/90 mmHg) or uncontrolled hypertension ( ≥ 140/90 mmHg) groups. Participants not receiving antihypertensive treatment were categorized: optimal BP ( < 120/80 mmHg), normal BP (120-129/80-84 mmHg), high-normal BP (130-139/85-89 mmHg), grade I hypertension (140-159/90-99 mmHg), and grade II/III hypertension ( ≥ 160/100 mmHg). Hazard ratios and 95% confidence intervals for the incidence of type 2 diabetes as defined by the 75-g OGTT were estimated using multivariable-adjusted Cox proportional hazard models in reference to optimal BP. During an average of 4.4 years of follow-up, 295 participants developed type 2 diabetes. Those with high-normal BP, grade I hypertension, grade II/III hypertension, and uncontrolled hypertension were at significantly higher risk for developing type 2 diabetes, with hazard ratios (95% confidence intervals) of 1.53 (1.03-2.29), 1.53 (1.02-2.32), 2.19 (1.01-4.77), and 1.81 (1.10-2.99), respectively. In conclusion, compared with those with optimal BP, individuals with BP ≥ 130/85 mmHg not receiving antihypertensive treatment and uncontrolled hypertensives with BP ≥ 140/90 mmHg receiving antihypertensive treatment were at a significantly higher risk for developing type 2 diabetes.

Microvascular Dysfunction and Hyperglycemia: A Vicious Cycle With Widespread Consequences

Microvascular and metabolic physiology are tightly linked. This Perspective reviews evidence that 1) the relationship between hyperglycemia and microvascular dysfunction (MVD) is bidirectional and constitutes a vicious cycle; 2) MVD in diabetes affects many, if not all, organs, which may play a role in diabetes-associated comorbidities such as depression and cognitive impairment; and 3) MVD precedes, and contributes to, hyperglycemia in type 2 diabetes (T2D) through impairment of insulin-mediated glucose disposal and, possibly, insulin secretion. Obesity and adverse early-life exposures are important drivers of MVD. MVD can be improved through weight loss (in obesity) and through exercise. Pharmacological interventions to improve MVD are an active area of investigation.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Regulation of voltage-gated potassium channels in vascular smooth muscle during hypertension and metabolic disorders

Voltage-gated potassium (KV ) channels are key regulators of vascular smooth muscle contractility and vascular tone, and thus have major influence on the microcirculation. KV channels are important determinants of vascular smooth muscle membrane potential (Em ). A number of KV subunits are expressed in the plasma membrane of smooth muscle cells. Each subunit confers distinct kinetics and regulatory properties that allow for fine control of Em to orchestrate vascular tone. Modifications in KV subunit expression and/or channel activity can contribute to changes in vascular smooth muscle contractility in response to different stimuli and in diverse pathological conditions. Consistent with this, a number of studies suggest alterations in KV subunit expression and/or function as underlying contributing mechanisms for small resistance artery dysfunction in pathologies such as hypertension and metabolic disorders, including diabetes. Here, we review our current knowledge on the effects of these pathologies on KV channel expression and function in vascular smooth muscle cells, and the repercussions on (micro)vascular function.

Effects of aerobic interval training on arterial stiffness and microvascular function in patients with metabolic syndrome

The authors determined the effect of high-intensity aerobic interval training on arterial stiffness and microvascular dysfunction in patients with metabolic syndrome with hypertension. Applanation tonometry was used to measure arterial stiffness and laser Doppler flowmetry to assess microvascular dysfunction before and after 6 months of stationary cycling (training group; n = 23) in comparison to a group that remained sedentary (control group; n = 23). While no variable improved in controls, hypertension fell from 79% (59%-91%) to 41% (24%-61%) in the training group, resulting in lower systolic and diastolic pressures than controls (-12 ± 3 and -6 ± 2 mm Hg, P < .008). Arterial stiffness declined (-17% augmentation index, P = .048) and reactive hyperemia increased (20%, P = .028) posttreatment in the training group vs controls. Blood constituents associated with arterial stiffness and a prothrombotic state (high-sensitivity C-reactive protein, fibrinogen, platelets, and erythrocytes) remained unchanged in the training and control groups. In summary, 6 months of an intense aerobic exercise program reduced both arterial stiffness and microvascular dysfunction in patients with metabolic syndrome despite unchanged blood-borne cardiovascular risk factors. Training lowers blood flow resistance in central and peripheral vascular beds in a coordinated fashion, resulting in clinically relevant reductions in hypertension.

Assessing Microvascular Function in Humans from a Chronic Disease Perspective

Microvascular dysfunction (MVD) is considered a crucial pathway in the development and progression of cardiometabolic and renal disease and is associated with increased cardiovascular mortality. MVD often coexists with or even precedes macrovascular disease, possibly due to shared mechanisms of vascular damage, such as inflammatory processes and oxidative stress. One of the first events in MVD is endothelial dysfunction. With the use of different physiologic or pharmacologic stimuli, endothelium-dependent (micro)vascular reactivity can be studied. This reactivity depends on the balance between various mediators, including nitric oxide, endothelin, and prostanoids, among others. The measurement of microvascular (endothelial) function is important to understand the pathophysiologic mechanisms that contribute to MVD and the role of MVD in the development and progression of cardiometabolic/renal disease. Here, we review a selection of direct, noninvasive techniques for measuring human microcirculation, with a focus on methods, interpretation, and limitations from the perspective of chronic cardiometabolic and renal disease.

Supplementation of selenium, vitamin E, chromium and betaine above recommended levels improves lactating performance of sows over summer

Heat stress (HS) exacerbates the body weight loss of lactating sows and reduces litter weight gain. Selenium (Se), vitamin E (VE), chromium (Cr) and betaine have been shown to ameliorate symptoms of HS, and yeast nucleotides and mannan oligosaccharides have been reported to improve lactational performance and immune response in pigs. Therefore, a combination of these nutrients may improve lactational performance of sows in summer. The effects of two nutritionally enhanced diets on lactational performance of sows in summer were investigated in two experiments. In experiment 1, we compared the effects of a nutritionally fortified diet (0.4 ppm Se, 95 IU/kg VE, 0.4 ppm Cr and 0.2% betaine; named as SVCB diet) with the NRC 2012 standard diet (0.15 ppm Se, 44 IU/kg VE) on lactational performance of sows in summer. Results showed that the SVCB diet reduced body weight loss (P = 0.039) and tended to reduce backfat loss (P = 0.075) of sows without affecting feed intake, while litter weight gain was not influenced. In experiment 2, we further enhanced the nutrients in the SVCB diet (0.8 ppm Se, 1% yeast nucleotides, and 0.1% mannan oligosaccharides; named as SNM diet). Results showed that the SNM diet did not improve feed intake of sows, farrowing performance, or litter weight gain compared with the SVCB diet, but increased body weight loss of the third parity sows (P = 0.037). Overall, a combined supplementation of Se, VE, Cr, and betaine above the NRC recommended levels can reduce mobilisation of body reserve of lactating sows in summer.

Acute effects of coffee on skin blood flow and microvascular function

OBJECTIVE

Studies on the acute effects of coffee on the microcirculation have shown contradicting results. This study aimed to investigate if intake of caffeine-containing coffee changes blood flow and microvascular reactivity in the skin.

METHODS

We measured acute changes in cutaneous vascular conductance (CVC) in the forearm and the tip of the finger, the microvascular response to transdermal iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) and post-occlusive reactive hyperemia (PORH) in the skin, after intake of caffeinated or decaffeinated coffee.

RESULTS

Vasodilatation during iontophoresis of ACh was significantly stronger after intake of caffeinated coffee compared to after intake of decaffeinated coffee (1.26±0.20PU/mmHg vs. 1.13±0.38PU/mmHg, P<0.001). Forearm CVC before and after PORH were not affected by caffeinated and decaffeinated coffee. After intake of caffeinated coffee, a more pronounced decrease in CVC in the fingertip was observed compared to after intake of decaffeinated coffee (-1.36PU/mmHg vs. -0.52PU/mmHg, P=0.002).

CONCLUSIONS

Caffeine, as ingested by drinking caffeinated coffee acutely improves endothelium-dependent microvascular responses in the forearm skin, while endothelium-independent responses to PORH and SNP iontophoresis are not affected. Blood flow in the fingertip decreases markedly during the first hour after drinking caffeinated coffee compared to decaffeinated coffee.

The Link Between Adipose Tissue Renin-Angiotensin-Aldosterone System Signaling and Obesity-Associated Hypertension

Obese individuals frequently develop hypertension, which is for an important part attributable to renin-angiotensin-aldosterone system (RAAS) overactivity. This review summarizes preclinical and clinical evidence on the involvement of dysfunctional adipose tissue in RAAS activation and on the renal, central, and vascular mechanisms linking RAAS components to obesity-associated hypertension.

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.

High folate and low vitamin B12 status during pregnancy is associated with gestational diabetes mellitus

BACKGROUND & AIMS

B-vitamins and homocysteine may contribute to the development of gestational diabetes mellitus (GDM), but existing studies are inconsistent. We examined the cross-sectional associations of plasma folate, vitamins B6, B12, and homocysteine concentrations with GDM and glycemia in a sample of multi-ethnic Asian pregnant women.

METHODS

Plasma concentrations of folate, vitamins B6, B12, homocysteine and glucose were measured at 26-weeks' gestation in 913 pregnant women. GDM was diagnosed using the 1999 World Health Organization criteria. Associations were examined with linear or logistic regression, adjusted for confounders and stratified by ethnicity.

RESULTS

Higher plasma folate was associated with higher 2-h glucose and higher odds of GDM [0.15 (0.02, 0.23) per 1-SD increment in folate, OR 1.29 (1.00, 1.60)], mainly among Indian mothers. Higher plasma vitamin B12 and homocysteine were associated with lower fasting and 2-h glucose, and lower odds of GDM [-0.04 (-0.07, -0.01) per 1-SD increment in B12 and -0.09 (-0.18, -0.003) respectively, OR: 0.81 (0.68, 0.97); -0.05 (-0.08, -0.02) per 1-SD increment in homocysteine and -0.12 (-0.21, -0.02) respectively, OR: 0.76 (0.62, 0.92)]. The highest odds of GDM were observed among women with combined vitamin B12 insufficiency and high folate concentration [OR: 1.97 (1.05, 3.68)]. An association between higher vitamin B6 and higher 2-h glucose shifted towards null adjusting for other B-vitamins.

CONCLUSIONS

Higher maternal folate coupled with vitamin B12 insufficiency was associated with higher GDM risk. This finding has potential implications for antenatal supplement recommendations but will require confirmation in future studies.

Effects of chromium supplementation on physiology, feed intake, and insulin related metabolism in growing pigs subjected to heat stress

Improving insulin sensitivity may reduce impacts of heat stress (HS) in pigs by facilitating heat dissipation. Chromium (Cr) has been reported to improve insulin sensitivity in pigs. Therefore, the aim of this experiment was to investigate whether Cr supplementation can mitigate HS in growing pigs. Thirty-six gilts were randomly assigned to 2 diets containing 0 (control) or 400 ppb Cr. After 14 d the supplemented pigs were allocated to either 8 d thermoneutral (20°C constant; TN) or cyclic HS (35°C, 0900 h to 1700 h) conditions and continued their respective diet (n = 9 per group). Growth performance was recorded during the 14-d supplementation period. The physiological responses to HS were monitored by measuring respiration rate, rectal temperature, blood gas chemistry, and feed intake during thermal exposure. Kinetics of plasma glucose, insulin and NEFA were studied by intravenous glucose tolerance test (IVGTT) on d 8 of thermal treatment. Results showed Cr alleviated the HS-increased rectal temperature (P < 0.05) and respiration rate (P < 0.01) at 1300 h and 1600 h during thermal exposure. However, Cr did not mitigate the reduction in average daily feed intake which was reduced by 35% during HS or the HS-induced respiratory alkalosis. Chromium tended to increase average daily gain (0.86 vs. 0.95 kg, P = 0.070) during the 14-d supplementation under TN conditions before thermal exposure, which might be associated with the potential of Cr in improving overall insulin sensitivity, as evidenced by a reduced insulin resistance index calculated by Homeostatic Model Assessment (HOMA-IR; 0.65 vs. 0.51, P = 0.013) and a tendency of reduced fasting plasma insulin concentration (1.97 vs. 1.67 μU/mL, P = 0.094). Heat stress decreased the acute insulin releasing rate (P = 0.012) and consequently slowed glucose clearance rate (P = 0.035) during IVGTT. Besides, HS enlarged the values of area under the curve of NEFA during IVGTT (P < 0.01), indicating a reduced lipid mobilization. In conclusion, HS reduced insulin response to IVGTT. Chromium supplementation exhibited a potential in improving insulin sensitivity and mitigating HS symptoms in growing pigs.

Improvement in Retinal Capillary Rarefaction After Valsartan Treatment in Hypertensive Patients

Decreased capillary density influences vascular resistance and perfusion. The authors aimed to investigate the influence of the renin-angiotensin receptor blocker valsartan on retinal capillary rarefaction in hypertensive patients. Retinal vascular parameters were measured noninvasively and in vivo by scanning laser Doppler flowmetry before and after 4 weeks of treatment with valsartan in 95 patients with hypertension stage 1 or 2 and compared with 55 healthy individuals. Retinal capillary rarefaction was determined with the parameters intercapillary distance (ICD) and capillary area (CapA). In hypertensive patients, ICD decreased (23.4±5.5 μm vs 21.5±5.6 μm, P<.001) and CapA increased (1564±621 vs 1776±795, P=.001) after valsartan treatment compared with baseline. Compared with healthy normotensive controls (ICD 20.2±4.2 μm, CapA 1821±652), untreated hypertensive patients showed greater ICD (P<.001) and smaller CapA (P=.019), whereas treated hypertensive patients showed no difference in ICD (P=.126) and CapA (P=.728). Therapy with valsartan for 4 weeks diminished capillary rarefaction in hypertensive patients.

Microvascular Dilator Function in Athletes: A Systematic Review and Meta-analysis

PURPOSE

Despite the growing research interest in vascular adaptations to exercise training over the last few decades, it remains unclear whether microvascular function in healthy subjects can be further improved by regular training. Herein, we sought to systematically review the literature and determine whether microvascular dilator function is greater in athletes compared to age-matched healthy untrained subjects.

METHODS

We conducted a systematic search of MEDLINE, Cochrane, EMBASE, and Web of Science since their inceptions until October 2013 for articles evaluating indices of primarily microvascular endothelium-dependent or endothelium-independent dilation (MVEDD and MVEID, respectively) in athletes. A meta-analysis was performed to determine the standardized mean difference (SMD) in MVEDD and MVEID between athletes and age-matched controls. Subgroup analyses were used to study potential moderating factors.

RESULTS

Thirty-six studies were selected after systematic review, comprising 521 athletes (506 endurance-trained and 15 endurance- and strength-trained) and 496 age-matched control subjects. After data pooling, athletes presented higher MVEDD (31 studies; SMD, 0.47; P < 0.00001) and MVEID (14 studies; SMD, 0.51; P < 0.00001) compared with the control subjects. Similar results were observed in young (younger than 40 yr) and master (older than 55 yr) athletes when analyzed separately.

CONCLUSION

Both young and master athletes present enhanced microvascular function compared with age-matched untrained but otherwise healthy subjects. These data provide evidence of a positive association between exercise training and microvascular function in the absence of known underlying cardiovascular disease.

Targeting inflammation in the prevention of cardiovascular disease in patients with inflammatory arthritis

Patients with inflammatory arthritis have increased risk of cardiovascular diseases (CVDs) compared with the general population. Subclinical carotid atherosclerosis and increased arterial stiffness are also common in these patients, which may serve as surrogate end points for cardiovascular (CV) events in clinical trials. Although exact mechanisms are still unclear, persistent systemic inflammation in patients with inflammatory arthritis may contribute to the development of CVD. Dysregulated innate immunity pathways in these patients may also play a role in accelerating atherosclerosis. During the last decade, effective suppression of inflammation by biological disease-modifying antirheumatic drugs has improved the disease outcome dramatically in patients with inflammatory arthritis. Growing evidence suggests that antitumor necrosis factor (TNF) therapy may prevent CVD in patients with rheumatoid arthritis. Nonetheless, data on non-TNF biologics are limited. Whether anti-TNF therapy may prevent CVD in patients with spondyloarthritis also remained unclear. In this review, we summarized the effect of both anti-TNF and non-TNF biologics on the CV system, including traditional CVD risk factors, endothelial function, arterial stiffness, subclinical atherosclerosis, and clinical CVD in patients with inflammatory arthritis.

Acute Thermotherapy Prevents Impairments in Cutaneous Microvascular Function Induced by a High Fat Meal

We tested the hypothesis that a high fat meal (HFM) would impair cutaneous vasodilation, while thermotherapy (TT) would reverse the detrimental effects. Eight participants were instrumented with skin heaters and laser-Doppler (LD) probes and tested in three trials: control, HFM, and HFM + TT. Participants wore a water-perfused suit perfused with 33°C (control and HFM) or 50°C (HFM + TT) water. Participants consumed 1 g fat/kg body weight. Blood samples were taken at baseline and two hours post-HFM. Blood pressure was measured every 5-10 minutes. Microvascular function was assessed via skin local heating from 33°C to 39°C two hours after HFM. Cutaneous vascular conductance (CVC) was calculated and normalized to maximal vasodilation (%CVCmax). HFM had no effect on initial peak (48 ± 4 %CVCmax) compared to control (49 ± 4 %CVCmax) but attenuated the plateau (51 ± 4 %CVCmax) compared to control (63 ± 4 %CVCmax, P < 0.001). Initial peak was augmented in HFM + TT (66 ± 4 %CVCmax) compared to control and HFM (P < 0.05), while plateau (73 ± 3 % CVCmax) was augmented only compared to the HFM trial (P < 0.001). These data suggest that HFM negatively affects cutaneous vasodilation but can be minimized by TT.

The role of insulin in the vascular contributions to age-related dementia

In addition to its well-known role in energy metabolism in the body, insulin is a vasoactive hormone that regulates peripheral and cerebral blood flow and neuronal function. Vascular and metabolic dysfunctions are emerging risk factors for Alzheimer's disease (AD) and age-related dementias, and recent evidence suggests that the two pathways are constitutive and interrelated. As a result, an emphasis on correcting metabolic disorders is emerging as an important strategy in the treatment and prevention of age-related cognitive impairment and AD. We review the evidence regarding the unique and interactive effects of vascular and metabolic disorders in pathological brain aging, with special consideration of the role of insulin dysregulation in promoting AD pathologic processes and vascular brain injury. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Exercise intensity modulates capillary perfusion in correspondence with ACE I/D modulated serum angiotensin II levels

During exercise the renin-angiotensin system is stimulated. We hypothesized that the increase in serum angiotensin II (AngII) levels after exercise is dependent on exercise intensity and duration and secondly that people with the ACE-II genotype will show a higher increase in AngII serum levels. We also assumed that perfusion of upper limbs is transiently reduced with maximal cycling exercise and that subjects with the ACE-II compared to the ACE-ID/DD genotype will have a higher capillary perfusion due to lower AngII levels. Ten healthy subjects completed a maximal exercise test, a 12-min exercise test at ventilatory threshold and a 3-min test at the respiratory compensation point. AngII serum levels and capillary recruitment of the skin in the third finger were measured before and after exercise and breath-by-breath gas exchange during exercise was assessed. Baseline levels of AngII levels were lower prior to the 3-min test which took place on average 5 days after the last exercise. A two-fold increase compared to baseline levels was found for AngII only immediately after the 3-min test and not after the maximal exercise test and 12-min of exercise. Subjects without the I allele showed a decrease in AngII values after the maximal test in contrast to subjects with the ACE-II/ID genotype. Subjects with the ACE-II genotype had a 1.8 times significant higher capillary perfusion in the finger after exercise. A trend was observed for a 34.3% decreased capillary recruitment in the ACE-ID/DD genotype after exercise. We conclude that the rise in AngII after exercise is intensity dependent and that variability in serum AngII and capillary perfusion is related to the ACE I/D polymorphism.

Sleep quality and duration are related to microvascular function: the Amsterdam Growth and Health Longitudinal Study

Sleep and sleep disorders are related to cardiovascular disease, and microvascular function is an early cardiovascular disease marker. Therefore, the relationship of sleep (measured in sleep quality and duration) with microvascular function was examined in healthy adults. Sleep quality was assessed with the validated Sleep Wake Experience List (SWEL) questionnaire. Duration of sleep was self-reported in an additional question. Microvascular function was measured using nailfold capillaroscopy. Linear regression analyses were used to examine the relationship between sleep and microvascular function. Potential confounders included physical activity, smoking, blood pressure, body mass index and several biochemical parameters. Analyses were performed in 259 participants (116 men). For women reporting insufficient (<7 h) sleep duration, microvascular function (post-ischaemic capillary recruitment) was significantly lower (b = -11.17; P = 0.04) compared to women reporting sufficient sleep duration. There was no relationship between sleep quality and microvascular function in females. In males, a trend towards lower capillary recruitment was found in those reporting a combination of poor sleep quality and insufficient duration (b = -7.54; P = 0.09), compared to those reporting good sleep quality as well as sufficient duration. This study suggests an association between sleep and microvascular function. Which aspects of sleep exactly affect microvascular function, and if indeed the association is different between males and females in other samples, needs further research.

Nonobese Young Females with Polycystic Ovary Syndrome have Nutritive Microvascular Dysfunction: A Pilot Study

OBJECTIVE

To investigate nutritive microvascular function in young nonobese females with polycystic ovary syndrome (PCOS) and to correlate microvascular reactivity with sex steroids, inflammatory markers, and metabolic variables.

METHODS

Fourteen nonobese females with PCOS (24.6 ± 2.7 years, body mass index [BMI] 23.7 ± 3.1 kg/m2) and 13 age- and BMI-matched controls (22.8 ± 2.3 years, 22.5 ± 3.4kg/m2) underwent anthropometric, hormonal, and microvascular evaluations. The main outcome measures were capillary density, red blood cell velocity (RBCV) at resting and peak during postocclusive reactive hyperemia (RBCVmax), and time taken to reach RBCVmax (TRBCVmax).

RESULTS

Subjects with PCOS had lower RBCV and higher TRBCVmax compared to controls, respectively (0.237 [0.220-0.324] vs. 0.362 [0.297-0.382] mm/s, P<.01) and (5 [5-6] vs. 4 [3-5] s, P<.05]. The free androgen index (FAI) and sex hormone-binding globulin (SHBG) level were different between groups. FAI correlated to RBCVmax (ρ = -0.49, P<.05) and to TRBCVmax (ρ = 0.41, P<.05). SHBG correlated with RBCVmax (ρ = 0.52, P<.01) while estradiol (E2) levels correlated with RBCV (ρ = 0.80, P<.001) and RBCVmax (ρ = 0.46, P<.05).

CONCLUSION

Microvascular dysfunction characterized by reduced RBCVmax and prolonged TRBCVmax was present in young, nonobese PCOS subjects. FAI was associated with observed impairments, suggesting a possible common mechanism linking sex hormones and microvascular dysfunction.

Cardiovascular responses to the ingestion of sugary drinks using a randomised cross-over study design: Does glucose attenuate the blood pressure-elevating effect of fructose?

Overconsumption of sugar-sweetened beverages has been implicated in the pathogenesis of CVD. The objective of the present study was to elucidate acute haemodynamic and microcirculatory responses to the ingestion of sugary drinks made from sucrose, glucose or fructose at concentrations similar to those often found in commercial soft drinks. In a randomised cross-over study design, twelve young healthy human subjects (seven men) ingested 500 ml tap water in which was dissolved 60 g of either sucrose, glucose or fructose, or an amount of fructose equivalent to that present in sucrose (i.e. 30 g fructose). Continuous cardiovascular monitoring was performed for 30 min before and at 60 min after ingestion of sugary drinks, and measurements included beat-to-beat blood pressure (BP) and impedance cardiography. Additionally, microvascular endothelial function testing was performed after iontophoresis of acetylcholine and sodium nitroprusside using laser Doppler flowmetry. Ingestion of fructose (60 or 30 g) increased diastolic and mean BP to a greater extent than the ingestion of 60 g of either glucose or sucrose (P< 0.05). Ingestion of sucrose and glucose increased cardiac output (CO; P< 0.05), index of contractility (P< 0.05) and stroke volume (P< 0.05), but reduced total peripheral resistance (TPR; P< 0.05), which contrasts with the tendency of fructose (60 and 30 g) to increase resistance. Microvascular endothelial function did not differ in response to the ingestion of various sugary drinks. In conclusion, ingestion of fructose, but not sucrose, increases BP in healthy human subjects. Although sucrose comprises glucose and fructose, its changes in TPR and CO are more related to glucose than to fructose.

Body mass index is related to microvascular vasomotion, this is partly explained by adiponectin

OBJECTIVE

obesity-related microvascular dysfunction, including alterations in rhythmic changes in vascular diameter, so-called 'vasomotion', may be important in the clustering of obesity with other cardiovascular risk factors. Adipokines have been suggested to play a role in obesity-related vascular dysfunction. Alterations in vasomotion have been found using extreme body mass index (BMI) phenotypes. Whether these alterations can be translated to the general population is unknown. The aim was to retrospectively investigate relationships between BMI, vasomotion and adipokines in a population-based cohort.

METHODS

Adiposity, vasomotion, adiponectin and leptin were determined in 94 apparently healthy participants (age 42 years, 46 men, mean BMI 25·5 ± 3·8 kg/m(2) ) of the Amsterdam Growth and Health Longitudinal Study (AGHLS). Vasomotion was assessed via wavelet analysis of skin laser Doppler flowmetry (LDF).

RESULTS

BMI was associated with the neurogenic domain of the vasomotion spectrum (β -0·011, P = 0·046), adiponectin (β -0·18, P = 0·028) and leptin (β 2·22, P < 0·0001). Adiponectin was positively associated with the neurogenic domain of vasomotion (β 0·016, P = 0·019). Leptin did not show any significant relationship with vasomotion. The association between BMI and the neurogenic domain of the vasomotion spectrum was partly explained by adiponectin.

CONCLUSIONS

The association between adiposity and microvascular vasomotion also applies to the normal population and is partly explained by adiponectin.

Proliferative retinopathy in type 1 diabetes is associated with cerebral microbleeds, which is part of generalized microangiopathy

OBJECTIVE We investigated whether proliferative diabetic retinopathy in type 1 diabetic patients can be generalized to cerebral small vessel disease and whether it is associated with impaired peripheral microvascular function. RESEARCH DESIGN AND METHODS Thirty-three patients with proliferative diabetic retinopathy (PDR+), 34 patients without proliferative diabetic retinopathy, and 33 controls underwent magnetic resonance imaging to assess cerebral microangiopathy (cerebral microbleeds) and ischemic damage (white matter hyperintensities and lacunes). Peripheral microvascular function, i.e., skin capillary density and capillary recruitment, was assessed by capillary microscopy. RESULTS Cerebral microbleeds, but not ischemic damage, were more prevalent in PDR+ patients versus the other groups (P < 0.05). A trend was found across groups for the lowest baseline capillary density in PDR+ patients (P for trend = 0.05). In individuals with microbleeds, capillary recruitment was impaired compared with those without microbleeds (P = 0.04). CONCLUSIONS In PDR+ patients, cerebral microbleed prevalence was higher and seems part of generalized microangiopathy that may affect the skin and the brain.