Microvascular dysfunction: a potential mechanism in the pathogenesis of obesity-associated insulin resistance and hypertension

Treatment strategy for type 2 diabetes from the perspective of systemic vascular protection and insulin resistance

This paper provides an update on the mechanisms of vascular impairment associated with insulin resistance and the pathogenesis of diabetic nephropathy and peripheral artery disease (PAD). It also considers the optimal treatment strategies for systemic vascular protection in light of recent findings. This area is of major clinical importance given the ongoing global epidemic of type 2 diabetes and the pivotal role played by insulin resistance in the mechanism of vascular impairment that manifests as macroangiopathy and microangiopathy. Timely diagnosis and intervention is critical in patients with systemic arteriosclerotic disease. Therefore, treatment strategies are aimed not only at targeting the presenting pathology, but also at reducing the risk of cardiovascular events. These efforts can help reduce the risk of both cardiovascular events and mortality. Treatment for PAD includes pharmacotherapy, endovascular treatment, and vascular reconstruction, along with exercise therapy. Because PAD can cause ischemia in the lower extremities, typical drug approaches include use of vasodilators and antiplatelet agents. Beraprost sodium and cilostazol are common choices in Japan, and their risks and benefits are discussed. Of note, beraprost has several therapeutic properties, including vascular endothelial protection, and antiplatelet and anti-inflammatory effects, in addition to vasodilatory activity. In patients with PAD, these activities improve the pathological process in the lower extremities and reduce the incidence of systemic vascular events. Recent preclinical findings indicate that beraprost improves not only ischemic extremities through its vasodilatory properties, but also reduces the insulin resistance which affects vascular endothelium. In this way, beraprost may contribute to an overall systemic vascular protective action. The use of agents, such as beraprost, which are capable of improving insulin resistance and resulting vascular endothelial function at an earlier disease stage, may ultimately contribute to increasing the life expectancy of patients with PAD.

Peripheral vascular response to inspiratory breath hold in paediatric homozygous sickle cell disease

New Findings

• What is the central question of this study?

Autonomic nervous dysfunction is implicated in complications of sickle cell anaemia (SCA). In healthy adults, a deep inspiratory breath hold (IBH) elicits rapid transient SNS- mediated vasoconstriction detectable using Laser Doppler Flux (LDF) assessment of the finger-tip cutaneous micovasculature.

• What is the main finding and its importance?

We demonstrate significantly increased resting peripheral blood flow and sympathetic activity in African children with SCA compared to sibling controls and increased sympathetic stimulation in response to vasoprovocation with DIG.

This study is the first to observe an inverse association between resting peripheral blood flow and haemoglobin oxygen saturation (SpO2). These phenomena may be an adaptive response to the hypoxic exposure in SCA.

There is increasing evidence that autonomic dysfunction in adults with homozygous sickle cell (haemoglobin SS) disease is associated with enhanced autonomic nervous system-mediated control of microvascular perfusion. However, it is unclear whether such differences are detectable in children with SS disease. We studied 65 children with SS disease [38 boys; median age 7.2 (interquartile range 5.1–10.6) years] and 20 control children without symptoms of SS disease [8 boys; 8.7 (5.5–10.8) years] and recorded mean arterial blood pressure (ABP) and daytime haemoglobin oxygen saturation (). Cutaneous blood flux at rest (RBF) and during the sympathetically activated vasoconstrictor response to inspiratory breath hold (IBH) were measured in the finger pulp of the non-dominant hand using laser Doppler fluximetry. Local factors mediating flow motion were assessed by power spectral density analysis of the oscillatory components of the laser Doppler signal. The RBF measured across the two study groups was negatively associated with age (r=−0.25, P < 0.0001), ABP (r=−0.27, P= 0.02) and daytime (r=−0.30, P= 0.005). Children with SS disease had a higher RBF (P= 0.005) and enhanced vasoconstrictor response to IBH (P= 0.002) compared with control children. In children with SS disease, higher RBF was associated with an increase in the sympathetic interval (r=−0.28, P= 0.022). The SS disease status, daytime and age explained 22% of the variance in vasoconstrictor response to IBH (P < 0.0001). Our findings suggest that blood flow and blood flow responses in the skin of young African children with SS disease differ from those of healthy control children, with increased resting peripheral blood flow and increased sympathetic stimulation from a young age in SS disease. They further suggest that the laser Doppler flowmetry technique with inspiratory breath hold manoeuvre appears to be robust for use in young children with SS disease, to explore interactions between , ABP and autonomic function with clinical complications, e.g. skin ulceration.

Spotlight issue: Microcirculation—from a clinical perspective

This spotlight issue of Microcirculation contains five articles written from a clinical perspective on the role of microcirculatory abnormalities in the pathogenesis of cardiovascular disease. The reviews address issues such as the impact of modifiable (life style and environmental risk factors) and non modifiable (age) on microvascular form and function; inter- and intra-cell signaling pathways underlying microvascular dysfunction; microvascular assessment as a prognostic tool in clinical practice; and the potential impact of targeted therapeutic intervention on microvascular health. The articles also describe and evaluate methodological approaches to the assessment of microvascular function in organs such as the skin, retina, muscle and adipose tissue, and provide a perspective on how such approaches might be employed in future in disease risk stratification in large epidemiological studies. This timely edition of the journal Microcirculation highlights that while there is currently no identified unifying mechanism to explain the association between microvascular phenotype and susceptibility to disease, there is accumulating evidence that deficits in microvascular structure and function may be an early and important prodromal indicator and risk determinant in a wide range of chronic non-communicable disorders, including cardiovascular and metabolic disease.