Relation of blunted dilation of the brachial artery in insulin-dependent diabetes mellitus to microalbuminuria

Effects of sodium-glucose cotransporter 2 inhibitors, mineralocorticoid receptor antagonists, and their combination on albuminuria in diabetic patients

AIMS

Diabetes mellitus (DM) is the leading cause of chronic kidney disease. Albuminuria is associated with an increased risk of cardiovascular mortality. Sodium-glucose cotransporter 2 inhibitors (SGLT2-Is) and mineralocorticoid receptor antagonists (MRAs) protect against albuminuria; however, their combined effects on albuminuria are unclear. We performed a network meta-analysis to investigate the effects of SGLT2-Is, MRAs and their combination on albuminuria in type 2 DM.

METHODS

We systematically searched PubMed, Medline, EMBASE and the Cochrane Library from inception up to 20 November 2022. We selected randomized control and crossover trials that compared MRAs, SGLT2-Is, MRAs + SGLT2-Is, or a placebo in patients with type 2 DM with a urinary albumin-creatinine ratio (UACR) ≥30 mg/g creatinine. The primary outcome was the change in the UACR.

RESULTS

This meta-analysis analysed 17 studies with 34 412 patients. The use of combination treatment with SGLT2-Is and MRAs was associated with lower albuminuria compared with the use of SGLT2-Is, MRAs, or the placebo alone [mean difference (95% CI): -34.19 (-27.30; -41.08), -32.25 (-24.53; -39.97) and -65.22 (-57.97; -72.47), respectively]. Treatment with SGLT2-Is or MRAs alone caused a significant reduction in UACR compared with the placebo [mean difference (95% CI): -31.03 (-28.35; -33.72) and -32.97 (-29.68; -36.27), respectively]. The effects of MRAs on the UACR are comparable with those of SGLT2-Is. Sensitivity analyses showed similar results.

CONCLUSION

Combination therapy with SGLT2-Is and MRAs was associated with lower albuminuria in patients with type 2 DM compared with monotherapy with SGLT2-Is or MRAs alone.

Endothelial Dysfunction and Its Clinical Implications

Endothelial dysfunction (ED) plays a substantial role in the pathogenesis of atherosclerosis and some other vascular diseases. ED has been demonstrated in patients with hypercholesterolemia, diabetes, smoking, hypertension, and in patients with atherosclerotic disease. Besides classical risk factors, ED is affected by chronic inflammatory diseases and acute infections, particularly viral diseases. Causes of ED include oxidative stress, inflammation, and shear stress, which decrease the bioavailability of nitric oxide. Markers of ED have been sought, particularly circulating markers. Using these tests, it is possible to evaluate the response to harmful effects of risk factors and the effects of treatment on vessel wall function. Endothelial dysfunction is significantly and directly correlated with the occurrence of cardiac events and the risk of cardiac events increase as ED worsens. Because endothelial function plays a central role in atherogenesis it became a therapeutic target. Endothelial dysfunction is reversible and its improvement may be achieved by elimination of risk factors, inhibitors of endothelium-derived contracting factors (angiotensin-converting enzyme), smoking cessation, lipid-lowering drugs, diet, and physical exercise. By reversing ED, it is possible to restore vascular function.

Endothelial Function in Patients With Continuous-Flow Left Ventricular Assist Devices

The endothelium plays a crucial role in maintaining cardiovascular homeostasis. Shear stress generated by flowing blood regulates the release of substances that provide adequate tissue perfusion. The extent of damage to endothelial cells depends on locally disturbed shear stress caused by the deteriorated flow. Patients with heart failure have reduced cardiac output, which results in reduced blood flow and negative shear stress. Reduced shear stress also affects microcirculation and reduces tissue perfusion. Consequently, the production of free oxygen radicals is increased and bioavailability of nitric oxide is additionally decreased. Therefore, endothelial dysfunction is involved in the progression of heart failure and cardiovascular events. Left ventricular assist devices (LVAD) are used for the treatment of patients with advanced heart failure. Older pulsatile flow LVADs were mostly substituted by continuous-flow LVADs (cf-LVADs). Despite the advantages of the cf-LVADs, the loss of pulsatility leads to different complications on the micro- and macrovascular levels. One of the pathogenetic mechanisms of cardiovascular complications with cf-LVADs may be endothelial dysfunction, which after the implantation of the device does not improve and may even deteriorate. In contrast, the pulsatile pattern of LVADs on blood flow could preserve endothelial function.

Treatment of Essential Arterial Hypertension with Enalapril Does Not Result in Normalization of Endothelial Dysfunction of the Conduit Arteries

It is assumed that endothelial dysfunction due to arterial hypertension could be improved or even normalized by antihypertensive treatment. The present study was designed to explore that assumption in patients with essential hypertension treated with an angiotensin-converting enzyme (ACE) inhibitor-enalapril. Twenty-eight patients (mean age: 55.1 years) who fulfilled the following criteria were included: essential arterial hypertension present for more than 2 years, monotherapy with enalapril for at least 1 year, adequate treatment (blood pressure in the last year <140/90 mm Hg) and absence of other factors (smoking, hypercholesterolemia, diabetes, obesity), which could importantly influence endothelial function. The flow-mediated (endothelium-dependent) dilation (FMD) of the brachial artery was assessed by high-resolution ultrasound and compared with that of 22 age-matched healthy normotensive controls. The patients and controls did not differ in regard to body mass index, lipids, and plasma glucose and insulin; there were no smokers. FMD of the brachial artery was significantly decreased in patients in comparison to controls (7.9% vs 13.5%, p<0.01). FMD in patients was inversely correlated with the duration of hypertension ( r =-0.52, p<0.01) and with both systolic ( r =-0.72, p<0.01) and diastolic ( r =-0.43, p<0.05) blood pressure (measured after temporary withdrawal of treatment). This study showed that the adequate control of blood pressure achieved with enalapril is not followed by normalization of endothelial function, measured by FMD of the brachial artery.

Capillary Rarefaction Associates with Albuminuria: The Maastricht Study

Albuminuria may be a biomarker of generalized (i.e., microvascular and macrovascular) endothelial dysfunction. According to this concept, endothelial dysfunction of the renal microcirculation causes albuminuria by increasing glomerular capillary wall permeability and intraglomerular pressure, the latter eventually leading to glomerular capillary dropout (rarefaction) and further increases in intraglomerular pressure. However, direct evidence for an association between capillary rarefaction and albuminuria is lacking. Therefore, we examined the cross-sectional association between the recruitment of capillaries after arterial occlusion (capillary density during postocclusive peak reactive hyperemia) and during venous occlusion (venous congestion), as assessed with skin capillaroscopy, and albuminuria in 741 participants of the Maastricht Study, including 211 participants with type 2 diabetes. Overall, 57 participants had albuminuria, which was defined as a urinary albumin excretion ≥30 mg/24 h. After adjustment for potential confounders, participants in the lowest tertile of skin capillary recruitment during postocclusive peak reactive hyperemia had an odds ratio for albuminuria of 2.27 (95% confidence interval, 1.07 to 4.80) compared with those in the highest tertile. Similarly, a comparison between the lowest and the highest tertiles of capillary recruitment during venous congestion yielded an odds ratio of 2.89 (95% confidence interval, 1.27 to 6.61) for participants in the lowest tertile. In conclusion, lower capillary density of the skin microcirculation independently associated with albuminuria, providing direct support for a role of capillary rarefaction in the pathogenesis of albuminuria.

In patients with idiopathic venous thrombosis, interleukin-10 is decreased and related to endothelial dysfunction

The aim of this study was to evaluate the levels of anti-inflammatory interleukin-10 and pro-inflammatory cytokines and their relationship to endothelial function in patients with idiopathic venous thrombosis. Forty-nine eligible patients of both sexes with idiopathic venous thrombosis and 48 matched control subjects were studied. Levels of inflammatory markers were determined. Endothelial function was evaluated by ultrasound measurement of the flow mediated dilatation (FMD) of the brachial artery. Compared to the control group, patients with idiopathic venous thrombosis had significantly lower levels of interleukin-10 1.81 pg/ml (1.53-2.21) versus 2.71 pg/ml (1.84-3.65), p < 0.001. Patients also had increased levels of pro-inflammatory cytokines: interleukin-6 2.37 pg/ml (1.59-4.09) versus 2.03 pg/ml (1.49-2.59), p = 0.025, interleukin-8 3.53 pg/ml (2.94-5.30) versus 2.25 pg/ml (1.77-2.90), p < 0.001. Furthermore, decreased FMD was observed in patients: 5.0% (3.9-6.9) versus 12.7% (10.8-15.6), p < 0.001. FMD was related to levels of interleukin-10 (r = 0.33, p = 0.001) and was inversely related to pro-inflammatory cytokines interleukin-6 (r = -0.34, p = 0.001) and interleukin-8 (r = -0.43, p < 0.001). Patients with idiopathic venous thrombosis have decreased levels of IL-10 and increased levels of pro-inflammatory cytokines. This imbalance indicates that in the stable phase of the disease, patients have an increased systemic inflammatory response. This inflammatory response could be the consequence of the disease, but most probably is involved in the pathogenesis of venous thrombosis.

Impairment of the vasodilatation capability of the brachial artery in patients with idiopathic venous thrombosis

AIM

Determination of the functional capability of the peripheral arteries is increasingly used as an early marker of vessel disease. The aim of this study was to evaluate flow-mediated (FMD) and glyceryl trinitrate-mediated (NMD) dilation of the brachial artery in patients with idiopathic venous thrombosis (VT).

METHODS

Flow-mediated brachial artery dilatation and the dilatation response to glyceryl trinitrate were measured using high-resolution ultrasound in 97 subjects (49 eligible patients of both sexes, mean age 51.5 ± 14.6 years, with idiopathic venous thrombosis, and 48 age-matched healthy controls).

RESULTS

Compared to the control group, FMD was significantly reduced in the group of patients with idiopathic venous thrombosis -4.9% (95% CI 1.1-8.7%) vs. 12.7% (95% CI 7.8-17.6%), p<0.001. Patients also had diminished NMD of the brachial artery -12.5% (95% CI 6.6-18.4%) vs. 18.5% (95% CI 10.1-26.9%), p<0.001. In patients, significantly higher levels of circulatory markers (P-selectin, von Willebrand factor) of endothelial dysfunction were registered.

CONCLUSIONS

Idiopathic venous thrombosis is associated with impaired flow- and GTN-mediated vasodilatory response of the brachial artery. This may suggest involvement of the functional deterioration of the vessel wall in the pathogenesis of idiopathic VT and indicate a relationship between VT and atherothrombosis.

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

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

The association of acute exercise-induced ischaemia with systemic vasodilator function in patients with peripheral arterial disease

Abstract

Patients with peripheral arterial disease (PAD) frequently experience ischaemic attacks of the affected tissues during exercise. The present study assesses the association of transient exercise-induced leg ischaemia with vasodilator function of the clinically unaffected brachial artery over the course of 4 hours. Thirty male patients with symptomatic PAD and 14 age- and sex-matched healthy controls were included in the study. They performed a treadmill exercise until intolerable exercise-induced ischaemic pain occurred in the affected lower extremity, or for at most 10 min. Flow-mediated dilation (FMD) of the brachial artery was measured at baseline, 30 minutes, 2 hours and 4 hours after exercise. Baseline FMD values were significantly diminished in patients (7.03 ± 1.99% vs 8.22 ± 1.60% in controls, p = 0.009). A significant decrease in FMD was observed in patients after exercise (at 30 minutes: 3.92 ± 1.78% vs 7.03 ± 1.99% at baseline, p < 0.001; at 2 hours: 6.36 ± 2.12% vs 7.03 ± 1.99% at baseline, p = 0.005), followed by a gradual return to its baseline value, whereas FMD in controls non-significantly increased after exercise. The difference in the pattern of FMD change over time between patients and controls was significant ( p < 0.001). This study shows that in PAD patients ischaemia during intermittent claudication is related to a transitory functional deterioration of the distant arteries. This indicates the harmful systemic effects of repeated ischaemic attacks during exercise and might explain the generalized and advanced nature of atherosclerotic disease in PAD patients.

Endothelial dysfunction in post-myocardial infarction patients with various expressions of risk factors

It has not been established yet whether patients who suffer myocardial infaction (MI) in the absence of classic risk factors also have endothelial dysfunction (ED), as has been shown for patients with risk factors, and if so, to what extent it is manifested. Young male patients in the stable phase after MI were included in the study. At the time of MI, 20 patients had high and 21 patients low expression of risk factors. The control group consisted of 35 healthy age-matched males. ED was estimated by ultrasound measurement of the endothelium-dependent dilation of the brachial artery, induced by the reactive hyperemia test. Compared to the control group, the level of endothelium-dependent vasodilation was significantly reduced in both groups of patients (controls: 9.1% +/- 5.6%; patients with high risk: 5.5% +/- 5.1%; patients with low risk: 5.6 +/- 3.5 %; ANOVA, p<.01). There was no difference between both groups of patients. These results showed that ED is not associated or due only to classic risk factors. It appears that ED may occur and precede development of atherosclerosis in the absence of classic risk factors. These novel findings can have important clinical implications.

Microalbuminuria and endothelial dysfunction: emerging targets for primary prevention of end-organ damage

A minor increase in urinary albumin excretion (microalbuminuria) is known to predict adverse renal and cardiovascular events in diabetic and hypertensive patients. Recent intriguing findings show that microalbuminuria is an early and sensitive marker of future cardiovascular events even in healthy subjects. The mechanisms linking microalbuminuria with end-organ damage have not been fully explained yet; however, generalized endothelial dysfunction might play an important role. Prevailing experimental and clinical data suggest that generalized endothelial dysfunction, frequently characterized by decreased nitric oxide bioavailability, actually precedes the development of microalbuminuria. This review summarizes the current knowledge about the intricate relationship between microalbuminuria and endothelial dysfunction. On the basis of the current evidence, we propose that microalbuminuria and endothelial dysfunction are an emerging target for primary prevention strategies in cardiovascular disease. In near future, dietary components improving nitric oxide bioavailability, such as cocoa-derived flavanols may play important role in these preventive strategies.

Endothelial dysfunction: a comprehensive appraisal

The endothelium is a thin monocelular layer that covers all the inner surface of the blood vessels, separating the circulating blood from the tissues. It is not an inactive organ, quite the opposite. It works as a receptor-efector organ and responds to each physical or chemical stimulus with the release of the correct substance with which it may maintain vasomotor balance and vascular-tissue homeostasis. It has the property of producing, independently, both agonistic and antagonistic substances that help to keep homeostasis and its function is not only autocrine, but also paracrine and endocrine. In this way it modulates the vascular smooth muscle cells producing relaxation or contraction, and therefore vasodilatation or vasoconstriction. The endothelium regulating homeostasis by controlling the production of prothrombotic and antithrombotic components, and fibrynolitics and antifibrynolitics. Also intervenes in cell proliferation and migration, in leukocyte adhesion and activation and in immunological and inflammatory processes. Cardiovascular risk factors cause oxidative stress that alters the endothelial cells capacity and leads to the so called endothelial "dysfunction" reducing its capacity to maintain homeostasis and leads to the development of pathological inflammatory processes and vascular disease.

There are different techniques to evaluate the endothelium functional capacity, that depend on the amount of NO produced and the vasodilatation effect. The percentage of vasodilatation with respect to the basal value represents the endothelial functional capacity. Taking into account that shear stress is one of the most important stimulants for the synthesis and release of NO, the non-invasive technique most often used is the transient flow-modulate "endothelium-dependent" post-ischemic vasodilatation, performed on conductance arteries such as the brachial, radial or femoral arteries. This vasodilatation is compared with the vasodilatation produced by drugs that are NO donors, such as nitroglycerine, called "endothelium independent". The vasodilatation is quantified by measuring the arterial diameter with high resolution ultrasonography. Laser-Doppler techniques are now starting to be used that also consider tissue perfusion.

There is so much proof about endothelial dysfunction that it is reasonable to believe that there is diagnostic and prognostic value in its evaluation for the late outcome. There is no doubt that endothelial dysfunction contributes to the initiation and progression of atherosclerotic disease and could be considered an independent vascular risk factor. Although prolonged randomized clinical trials are needed for unequivocal evidence, the data already obtained allows the methods of evaluation of endothelial dysfunction to be considered useful in clinical practice and have overcome the experimental step, being non-invasive increases its value making it use full for follow-up of the progression of the disease and the effects of different treatments.

Vascular reactivity in diabetes mellitus

Cardiovascular disease is responsible for 70% of the deaths in diabetes mellitus. Endothelial dysfunction occurs early in atherosclerosis and can now be assessed accurately and reproducibly by noninvasive means. Hyperglycemia, insulin resistance, microvascular complications, and coexistent conditions have been shown to impair endothelial function in diabetes. Resistance to insulin's vasodilatory effect and increased free radical generation are probable mechanisms responsible for the endothelial dysfunction in this state. Improvement in glycemic control, insulin and insulin sensitizers, cholesterol lowering, hypolipidemic agents, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers have improved clinical cardiovascular outcomes and have also been shown to improve endothelial function. Strategies designed to assess and improve endothelial function may be further beneficial in terms of cardiovascular outcomes in diabetes mellitus, and need to be tested in a clinical setting.

Endothelial dysfunction in the pathogenesis of atherosclerosis

Healthy endothelium plays a central role in cardiovascular control. Therefore, endothelial dysfunction (ED), which is characterized by an imbalance between relaxing and contracting factors, procoagulant and anticoagulant substances, and between proinflammatory and antiinflammatory mediators, may play a particularly significant role in the pathogenesis of atherosclerosis. Endothelial dysfunction is closely related to different risk factors of atherosclerosis, and to their intensity and duration. The involvement of risk factors in ED is also supported by results of interventions studies that showed regression of ED with treatment of risk factors. Because risk factors are commonly accompanied by decreased bioavailability of nitric oxide, the common denominator whereby different risk factors cause ED is most probably increased oxidative stress. Endothelial dysfunction may promote atherogenesis through different mechanisms such as increased adherence of monocytes, macrophages, and enhanced permeability of the endothelial layer. Further, ED probably plays an important role in the growth of atherosclerotic lesions and in the development of thrombotic complications in late stages of the disease. Because ED is a key underlying factor in the atherosclerotic process, markers of endothelial abnormalities have been sought. Detection of ED is based on tests of endothelium-dependent vasomotion (dilation capability of peripheral and coronary arteries) and on circulating markers of endothelial function (endothelin-1, von Willebrand factor, tissue plasminogen activator, plasminogen activator inhibitor, and adhesion molecules). Using these tests it is possible to follow the dose response of harmful effects of risk factors, and the effects of preventive procedures on vessel wall function.