Microvascular responsiveness in obesity: implications for therapeutic intervention

Impaired Capillary Recruitment Capacity in Obesity: A Subgroup Analysis of Prospective Observational Study on Anesthesia Effects

BACKGROUND This subgroup analysis of prospective observational research, involving 71 participants, compared the effects of anesthesia on microvascular reactivity in obese vs lean individuals using near-infrared spectroscopy and vascular occlusion tests. The correlation between the body mass index (BMI) and microvascular reactivity under general anesthesia was also investigated. MATERIAL AND METHODS This study enrolled adult patients classified as American Society of Anesthesiologists physical status I or II, undergoing elective surgery under general anesthesia. The microcirculatory variables measured before (Tpre) and 30 min following the induction of anesthesia (Tpost) were as follows: baseline tissue oxygen saturation (StO₂), occlusion slope (∇occl), and recovery slope (∇recov). The patients were grouped according to their BMI (lean [BMI <25 kg/m²] vs obese [BMI ≥25 kg/m²]). Data are presented as medians and interquartile ranges. RESULTS There were 43 patients in the lean group and 28 in the obese group. At Tpre, baseline StO2, ∇occl, and ∇recov were not different between the 2 groups (P=0.860, 0.659, and 0.518, respectively). At Tpost, the baseline StO₂ and ∇occl were not different between the 2 groups (P=0.343 and 0.791); however, the ∇recov was lower in the obese group than in the lean group (3.245 [2.737, 3.977] vs 4.131 [3.491, 4.843], P=0.003). At Tpost, BMI showed a moderate correlation with ∇recov (correlation coefficient: -0.319, P=0.007). CONCLUSIONS In obese patients, capillary recruitment capacity during general anesthesia is compromised compared to lean patients.

The weight of obesity in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is one of the most frequently diagnosed primary conditions of the heart muscle. It is considered to be inherited, caused by genetic mutations encoding for sarcomere proteins. The marked heterogeneity in clinical manifestations and natural course of the disease, even among family members sharing the same genetic mutation, has raised the question of non-genetic environmental factors contributing to the phenotype. Obesity has been associated with worse cardiovascular outcomes in the general population. Its prevalence is increased in hypertrophic cardiomyopathy, and the two conditions share some similar pathophysiological and clinical characteristics. In this review, we aim to summarise the effects of obesity in the cardiac phenotype, the symptoms and management in patients with hypertrophic cardiomyopathy.

Evaluation of systemic endothelial-dependent and endothelial-independent microvascular reactivity in metabolically healthy obesity: An observational study

BACKGROUND

Metabolically healthy obesity (MHO), a phenotype of obesity considered to be of lower cardiovascular risk, is still a controversial concept. This study aimed to investigate the presence of subclinical systemic microvascular dysfunction in individuals with MHO.

METHODS

This was a cross-sectional study in which 112 volunteers were allocated into three groups: metabolically healthy normal weight (MHNW), MHO, or metabolically unhealthy obesity (MUO). Obesity was defined as a body mass index (BMI) ≥ 30 kg/m². MHO was defined as the absence of any component of metabolic syndrome, except waist circumference. Microvascular reactivity was evaluated using cutaneous laser speckle contrast imaging.

RESULTS

Mean age was 33.2 ± 7.66 years. The median BMI in the MHNW, MHO and MUO groups was 23.6, 32.8, and 35.8 kg/m², respectively. Baseline microvascular conductance values were lower in the MUO group (0.25 ± 0.08 APU/mmHg) than in MHO (0.30 ± 0.10 APU/mmHg) and MHNW groups (0.33 ± 0.12 APU/mmHg) (P = 0.0008). There were no significant differences regarding endothelial-dependent (acetylcholine stimulation or postocclusive reactive hyperemia) or endothelial-independent (sodium nitroprusside stimulation) microvascular reactivity among the groups.

CONCLUSIONS

Individuals with MUO had lower baseline systemic microvascular flow than those with MHNW or MHO, but endothelium-dependent or endothelium-independent microvascular reactivity were not changed in any of the groups. The relatively young age of the study population, the low frequency of class III obesity, or the strict definition of MHO (absence of any metabolic syndrome criteria) might account for the lack of difference of microvascular reactivity among MHNW, MHO or MUO.

Role of Perivascular Adipose Tissue in Aorta Reactivity from Obese and Hyperglycemic CD-1 Mice: New Insights into Perivascular Adipose Tissue

Background: Perivascular adipose tissue (PVAT) plays an essential role in cardiovascular homeostasis. However, during obesity and diabetes, its role in vascular tone regulation is unclear. This study aimed to evaluate the function of the PVAT on aorta reactivity in the lean and cafeteria (CAF) diet-induced obese-hyperglycemic mice model. Methods: Aorta reactivity to phenylephrine, KCl, and acetylcholine was analyzed in lean (n = 6) and obese mice (n = 6). Also, nitric oxide (NO-) and cyclooxygenase participation, in the presence (n = 6) and absence (n = 6) of PVAT, were examined in the aortas. Results: After a CAF diet for 19 weeks, obese mice showed increased body weight, glucose intolerance, and hypercholesterolemia concerning lean mice. Vascular reactivity to phenylephrine was reduced significantly in the aorta of obese mice. In contrast, the contraction produced by KCl (80 mM) was increased in the aorta of obese mice independent of PVAT. Acetylcholine-induced vasorelaxation diminished in the aortas of obese mice in the presence of PVAT. Nonselective inhibition of cyclooxygenases likely shows that PVAT and endothelium release vasorelaxant prostanoids. Conclusions: The results suggest that PVAT modulates aorta reactivity by releasing NO-, decreasing the α₁-adrenergic response to phenylephrine, and probably releasing vasorelaxant prostanoids. The data suggest that PVAT regulates the vascular smooth muscle and endothelial function in a CAF diet-induced obese-hyperglycemic mice model.

Evaluation of Fibrosis Markers as a Potential Method for Diagnosing Non-Obstructive Coronary Artery Disease in Patients with Stable Coronary Artery Disease

Aim. To study the levels of fibrosis markers in patients with stable coronary artery disease (CAD) and various types of coronary artery (CA) lesions (obstructive and non-obstructive), to identify possible differences for diagnosing the types of coronary obstruction.

Material and methods. The observational study included three groups of patients: with non-obstructive (main group, coronary artery stenosis <50%; n=20) and obstructive (comparison group, hemodynamically significant coronary artery stenosis according to the results of coronary angiography; n=20) CAD and healthy volunteers (control group; n=40). Transforming growth factor beta 1 (TGF-β1) and matrix metalloproteinase 9 (MMP-9) levels were measured in plasma by enzyme immunoassay. According to the results of echocardiography, all patients included in the study were divided into four groups depending on the type of myocardial remodeling.

Results. TGF-β1 levels were significantly higher in patients with obstructive CAD (p=0.008) than in patients with non-obstructive CAD and healthy volunteers (p <0.001). There were no significant differences between the main and control groups (p>0.05). There were no statistically significant differences in TGF-β1 levels depending on the type of left ventricular remodeling (p=0.139). The maximum level of MMP-9 was in the group with obstructive coronary disease and significantly differed from the main group (p <0.001) and the control group (p=0.04).

Conclusio. The maximum levels of TGF-β1 and MMP-9 were found in the group with obstructive coronary artery disease. The levels of these biomarkers in the main group were statistically different from the values obtained in the control group. Thus, considering the pathogenesis of the development of non-obstructive CAD, the use of fibrosis markers TGF-β1 and MMP-9 may be promising for diagnosing the severity of CA obstruction.

The Impact of Obesity on the Regulation of Muscle Blood Flow during Exercise in Patients with Heart Failure with a Preserved Ejection Fraction

Obesity is now considered a primary comorbidity in heart failure with preserved ejection fraction (HFpEF) pathophysiology, mediated largely by systemic inflammation. While there is accumulating evidence for a disease-related dysregulation of blood flow during exercise in this patient group, the role of obesity in the hemodynamic response to exercise remain largely unknown. Small muscle mass handgrip (HG) exercise was utilized to evaluate exercising muscle blood flow in non-obese (BMI < 30 kg/m²,n=14) and obese (BMI > 30 kg/m²,n=40) patients with HFpEF. Heart rate (HR), stroke index (SI), cardiac index (CI), mean arterial pressure (MAP), forearm blood flow (FBF) and vascular conductance (FVC) were assessed during progressive intermittent HG exercise (15-30-45% maximal voluntary contraction, MVC). Blood biomarkers of inflammation (C-reactive protein (CRP) and Interleukin-6 (IL-6)) were also determined. Exercising FBF was reduced in obese patients with HFpEF at all work rates (15%: 304±42 vs. 229±15ml/min; 30%: 402±46 vs. 300±18ml/min; 45%: 484±55 vs. 380±23ml/min, non-obese vs. obese, p=0.025), and was negatively correlated with BMI (R=-.47, p<0.01). In contrast, no differences in central hemodynamics (HR, SI, CI, MAP) were found between groups. Proinflammatory biomarkers were markedly elevated in obese patients (CRP: 2133±418 vs. 4630±590ng/ml, p=0.02; IL-6: 2.9±0.3 vs. 5.2±0.7pg/ml, p = 0.04, non-obese vs. obese), and both biomarkers were positively correlated with BMI (CRP: R=0.40, p=0.03; IL-6: R=0.57, p<0.01). Together, these findings demonstrate the presence of obesity and an accompanying milieu of systemic inflammation as important factors in the dysregulation of exercising muscle blood flow in patients with HFpEF.

Delivery of miRNAs to the adipose organ for metabolic health

Despite the increasing prevalence of obesity and diabetes, there is no efficient treatment to combat these epidemics. The adipose organ is the main site for energy storage and plays a pivotal role in whole body lipid metabolism and energy homeostasis, including remodeling and dysfunction of adipocytes and adipose tissues in obesity and diabetes. Thus, restoring and balancing metabolic functions in the adipose organ is in demand. MiRNAs represent a novel class of drugs and drug targets, as they are heavily involved in the regulation of many cellular and metabolic processes and diseases, likewise in adipocytes. In this review, we summarize key regulatory activities of miRNAs in the adipose organ, discuss various miRNA replacement and inhibition strategies, promising delivery systems for miRNAs and reflect the future of novel miRNA-based therapeutics to target adipose tissues with the ultimate goal to combat metabolic disorders.

Oxidative Stress and Vascular Damage in the Context of Obesity: The Hidden Guest

The vascular system plays a central role in the transport of cells, oxygen and nutrients between different regions of the body, depending on the needs, as well as of metabolic waste products for their elimination. While the structure of different components of the vascular system varies, these structures, especially those of main arteries and arterioles, can be affected by the presence of different cardiovascular risk factors, including obesity. This vascular remodeling is mainly characterized by a thickening of the media layer as a consequence of changes in smooth muscle cells or excessive fibrosis accumulation. These vascular changes associated with obesity can trigger functional alterations, with endothelial dysfunction and vascular stiffness being especially common features of obese vessels. These changes can also lead to impaired tissue perfusion that may affect multiple tissues and organs. In this review, we focus on the role played by perivascular adipose tissue, the activation of the renin-angiotensin-aldosterone system and endoplasmic reticulum stress in the vascular dysfunction associated with obesity. In addition, the participation of oxidative stress in this vascular damage, which can be produced in the perivascular adipose tissue as well as in other components of the vascular wall, is updated.

Endothelial dysfunction and inflammation in patients with non-obstructive coronary arteries

Aim To determine levels of markers for endothelial dysfunction and inflammation, endothelin-1, E-selectin, and tumor necrosis factor α (TNF-α) in patients with ischemic heart disease (IHD) and non-obstructive and obstructive coronary artery (CA) disease.Material and methods This study included 32 patients with verified IHD and non-obstructive (main group, n=19) and obstructive (comparison group, n=13) CA disease. Endothelial dysfunction was diagnosed by photoplethysmography and videocapillaroscopy. Serum concentrations of endothelin-1, E-selectin, and TNF- α were measured in all patients.Results Patients with non-obstructive CA disease showed a tendency towards more pronounced endothelial dysfunction (alternative stiffness index, 7.8 m /s [6.35; 9.08]; reflection index, 36.95 % [23.4; 52.65]; capillary density following reactive hyperemia, 54.33 cap /mm2 [48.92; 75.83]; capillary density following venous occlusion, 74.33 cap /mm2 [67.83; 93.00]) compared to the comparison group (alternative stiffness index, 9.05 m/s [7.08; 10.58]; reflection index, 28.25 % [23.35; 53.75]; capillary density following reactive hyperemia, 66.83 cap /mm2 [50.83; 78.67]; capillary density following venous occlusion, 87.0 cap /mm2 [77.58; 78.67]), although statistically significant differences were not found. Concentration of endothelin-1 was significantly higher in the IHD group with non-obstructive CA disease (0.45 ng/ml [0.28;0.65]) compared to patients with CA atherosclerotic stenosis (0.35 ng/ml [0.25; 0.38], p=0.035). Concentrations of E-selectin did not significantly differ between the groups (main group, 21.1 ng/ml [18.45; 35.03]; comparison group, 28.55 ng/ml [19.08; 35.01], p=0.29). In both groups, concentrations of TNF-α did not exceed the lower threshold of sensitivity (&lt;2.3 pg/ml).Conclusion Endothelial dysfunction and increased endothelin-1 in patients with non-obstructive CA disease along with inflammation may additionally contribute to the pathogenesis of IHD in the absence of hemodynamically significant CA stenoses. Too low level of TNFα in both groups prevented us from using it as a diagnostic marker. Further study is needed that would include a greater number of patients and a search for alternative markers.

Association Between Obesity and Microvascular Diseases in Patients With Type 2 Diabetes Mellitus

This study aimed to evaluate the association between obesity, evaluated by fat mass index (FMI) with the risk of microvascular diseases in patients with type 2 diabetes mellitus (T2DM) and compare the magnitude of associations of FMI, body mass index (BMI), and waist circumference (WC) with the risk of microvascular diseases. We performed a post-hoc analysis of the Action to Control Cardiovascular Risk in Diabetes study. The primary microvascular outcomes of the present study included chronic kidney disease (CKD) progression, retinopathy, and neuropathy. Cox proportional-hazards models were performed to evaluate the association of FMI with microvascular diseases. A discordant analysis was performed to compare the magnitude of associations of FMI, BMI, and WC with the risk of microvascular diseases. Our study included 10,251 T2DM participants with a median of 5 years (interquartile range, 4.2-5.7) of follow-up. A total of 6,184 participants developed CKD progression, 896 participants had retinopathy, and 3,213 participants developed neuropathy (Michigan Neuropathy Screening Instrument, >2.0). After the confounding factors were adjusted for, patients in the highest FMI quartile had a higher risk of CKD progression (HR: 1.26, 95%CI: 1.16-1.36) and neuropathy (HR: 1.93, 95% CI: 1.74-2.15), except for retinopathy (HR: 1.17, 95% CI: 0.96-1.43), than those in the lowest quartile. Discordant analyses found that FMI and WC are better in identifying individuals with obesity-related risk of neuropathy, compared with BMI; neither is better in identifying individuals with obesity-related risk of CKD progression and retinopathy. Obesity is associated with CKD progression and neuropathy in T2DM participants. Further randomized trials are needed to test whether obesity control can improve the outcomes of T2DM participants with CKD or neuropathy. FMI and WC are more useful in identifying obesity-related risk of neuropathy compared with BMI in T2DM patients.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov, NCT00000620.

Oxidative Stress in Ischemic Heart Disease

One of the novel interesting topics in the study of cardiovascular disease is the role of the oxidation system, since inflammation and oxidative stress are known to lead to cardiovascular diseases, their progression and complications. During decades of research, many complex interactions between agents of oxidative stress, oxidation, and antioxidant systems have been elucidated, and numerous important pathophysiological links to na number of disorders and diseases have been established. This review article will present the most relevant knowledge linking oxidative stress to vascular dysfunction and disease. The review will focus on the role of oxidative stress in endotheleial dysfunction, atherosclerosis, and other pathogenetic processes and mechanisms that contribute to the development of ischemic heart disease.

ESC Working Group on Coronary Pathophysiology and Microcirculation position paper on 'coronary microvascular dysfunction in cardiovascular disease'

Although myocardial ischaemia usually manifests as a consequence of atherosclerosis-dependent obstructive epicardial coronary artery disease, a significant percentage of patients suffer ischaemic events in the absence of epicardial coronary artery obstruction. Experimental and clinical evidence highlight the abnormalities of the coronary microcirculation as a main cause of myocardial ischaemia in patients with 'normal or near normal' coronary arteries on angiography. Coronary microvascular disturbances have been associated with early stages of atherosclerosis even prior to any angiographic evidence of epicardial coronary stenosis, as well as to other cardiac pathologies such as myocardial hypertrophy and heart failure. The main objectives of the manuscript are (i) to provide updated evidence in our current understanding of the pathophysiological consequences of microvascular dysfunction in the heart; (ii) to report on the current knowledge on the relevance of cardiovascular risk factors and comorbid conditions for microcirculatory dysfunction; and (iii) to evidence the relevance of the clinical consequences of microvascular dysfunction. Highlighting the clinical importance of coronary microvascular dysfunction will open the field for research and the development of novel strategies for intervention will encourage early detection of subclinical disease and will help in the stratification of cardiovascular risk in agreement with the new concept of precision medicine.

Emerging concepts in metabolically healthy obesity

Obesity is a major risk factor for noncommunicable diseases that is responsible for more than 70% of early deaths in the world. In the 1980's decade, some studies started to describe a "benign" obesity phenotype, named "metabolically healthy obesity" (MHO), which represents obesity without comorbidities such as hypertension, cardiovascular diseases, insulin resistance, diabetes, dyslipidemia or metabolic syndrome. However, it is still unclear if this "benign" obesity phenotype is really favorable or just a transition status to unhealthy obesity and if these subjects presented subclinical levels of cardiovascular risk that are not commonly detected. To further elucidate these issues, the investigation of pathophysiological mechanisms that can increase cardiovascular risk in MHO individuals, such as hormones and cytokines, may offer some responses. In parallel, the evaluation of subclinical cardiovascular derangement, using the systemic microcirculation as a proxy, may be an alternative to anticipate overt cardiovascular disease. Overall, further studies are needed to better understand the pathophysiology of MHO as well as to identify high-risk individuals who deserve more intensive management.

Metabolic syndrome - Evidence-based strategies for patient optimization

With the increasing prevalence of obesity worldwide, it is inevitable that anesthesiologists will encounter patients with metabolic syndrome. Metabolic syndrome encompasses multiple diseases, which include central obesity, hypertension, dyslipidemia, and hyperglycemia. Given the involvement of multiple diseases, metabolic syndrome involves numerous complex pathophysiological processes that negatively impact several organ systems. Some of the organ systems that have been well-documented to be adversely affected include the cardiovascular, pulmonary, and endocrine systems. Metabolic syndrome also leads to prolonged hospital stays, increased rates of infections, a greater need for care after discharge, and overall increased healthcare costs. Several interventions have been suggested to mitigate these negative outcomes ranging from lifestyle modifications to surgeries. Therefore, anesthesiologists should understand metabolic syndrome and formulate management strategies that may modify perianesthetic and surgical risks.

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.

Hypertensive Heart Disease and Obesity: A Review

Metabolic syndrome is an increasingly prevalent constellation of disease processes among the global population. Hypertension and obesity are among the contributing etiologies, and obesity increases the likelihood of hypertensive heart disease by creating a proinflammatory state, as well as increasing sympathetic tone and formation of reactive oxygen species. Hypertensive heart disease is characterized by myocardial fibrosis, which portends higher risk of developing reduced ejection fraction, diastolic dysfunction, ischemia, and arrhythmias, making early diagnosis and treatment essential to the prevention of cardiac events.

Hyperlipidemias and Obesity

The organs require oxygen and other types of nutrients (amino acids, sugars, and lipids) to function, the heart consuming large amounts of fatty acids for oxidation and adenosine triphosphate (ATP) generation.

Perivascular Adipose Tissue as a Relevant Fat Depot for Cardiovascular Risk in Obesity

Obesity is associated with increased risk of premature death, morbidity, and mortality from several cardiovascular diseases (CVDs), including stroke, coronary heart disease (CHD), myocardial infarction, and congestive heart failure. However, this is not a straightforward relationship. Although several studies have substantiated that obesity confers an independent and additive risk of all-cause and cardiovascular death, there is significant variability in these associations, with some lean individuals developing diseases and others remaining healthy despite severe obesity, the so-called metabolically healthy obese. Part of this variability has been attributed to the heterogeneity in both the distribution of body fat and the intrinsic properties of adipose tissue depots, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, hormonal control, thermogenic ability, and vascularization. In obesity, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. The adventitial fat layer, also known as perivascular adipose tissue (PVAT), is of major importance. Similar to the visceral adipose tissue, PVAT has a pathophysiological role in CVDs. PVAT influences vascular homeostasis by releasing numerous vasoactive factors, cytokines, and adipokines, which can readily target the underlying smooth muscle cell layers, regulating the vascular tone, distribution of blood flow, as well as angiogenesis, inflammatory processes, and redox status. In this review, we summarize the current knowledge and discuss the role of PVAT within the scope of adipose tissue as a major contributing factor to obesity-associated cardiovascular risk. Relevant clinical studies documenting the relationship between PVAT dysfunction and CVD with a focus on potential mechanisms by which PVAT contributes to obesity-related CVDs are pointed out.

Comparison of retinal vascular geometry in obese and non-obese children

Purpose

Childhood obesity is associated with adult cardiometabolic disease. We postulate that the underlying microvascular dysfunction begins in childhood. We thus aimed to compare retinal vascular parameters between obese and non-obese children.

Methods

This was a cross-sectional study involving 166 children aged 6 to 12 years old in Malaysia. Ocular examination, biometry, retinal photography, blood pressure and body mass index measurement were performed. Participants were divided into two groups; obese and non-obese. Retinal vascular parameters were measured using validated software.

Results

Mean age was 9.58 years. Approximately 51.2% were obese. Obese children had significantly narrower retinal arteriolar caliber (F_(1,159) = 6.862, p = 0.010), lower arteriovenous ratio (F_(1,159) = 17.412, p < 0.001), higher venular fractal dimension (F_(1,159) = 4.313, p = 0.039) and higher venular curvature tortuosity (F_(1,158) = 5.166, p = 0.024) than non-obese children, after adjustment for age, gender, blood pressure and axial length.

Conclusions

Obese children have abnormal retinal vascular geometry. These findings suggest that childhood obesity is characterized by early microvascular abnormalities that precede development of overt disease. Further research is warranted to determine if these parameters represent viable biomarkers for risk stratification in obesity.

Role of Adipose Tissue Endothelial ADAM17 in Age-Related Coronary Microvascular Dysfunction

OBJECTIVE

A disintegrin and metalloproteinase ADAM17 (tumor necrosis factor-α [TNF]-converting enzyme) regulates soluble TNF levels. We tested the hypothesis that aging-induced activation in adipose tissue (AT)-expressed ADAM17 contributes to the development of remote coronary microvascular dysfunction in obesity.

APPROACH AND RESULTS

Coronary arterioles (CAs, ≈90 µm) from right atrial appendages and mediastinal AT were examined in patients (aged: 69±11 years, BMI: 30.2±5.6 kg/m²) who underwent open heart surgery. CA and AT were also studied in 6-month and 24-month lean and obese mice fed a normal or high-fat diet. We found that obesity elicited impaired endothelium-dependent CA dilations only in older patients and in aged high-fat diet mice. Transplantation of AT from aged obese, but not from young or aged, mice increased serum cytokine levels, including TNF, and impaired CA dilation in the young recipient mice. In patients and mice, obesity was accompanied by age-related activation of ADAM17, which was attributed to vascular endothelium-expressed ADAM17. Excess, ADAM17-shed TNF from AT arteries in older obese patients was sufficient to impair CA dilation in a bioassay in which the AT artery was serially connected to a CA. Moreover, we found that the increased activity of endothelial ADAM17 is mediated by a diminished inhibitory interaction with caveolin-1, owing to age-related decline in caveolin-1 expression in obese patients and mice or to genetic deletion of caveolin-1.

CONCLUSIONS

The present study indicates that aging and obesity cooperatively reduce caveolin-1 expression and increase vascular endothelial ADAM17 activity and soluble TNF release in AT, which may contribute to the development of remote coronary microvascular dysfunction in older obese patients.

Cerebrovascular Disease: Consequences of Obesity-Induced Endothelial Dysfunction

Despite the well-known global impact of overweight and obesity in the incidence of cerebrovascular disease, many aspects of this association are still inconsistently defined. In this chapter we aim to present a critical review on the links between obesity and both ischemic and hemorrhagic stroke and discuss its influence on functional outcomes, survival, and current treatments to acute and chronic stroke. The role of cerebrovascular endothelial function and respective modulation is also described as well as its laboratory and clinical assessment. In this context, the major contributing mechanisms underlying obesity-induced cerebral endothelial function (adipokine secretion, insulin resistance, inflammation, and hypertension) are discussed. A special emphasis is given to the participation of adipokines in the pathophysiology of stroke, namely adiponectin, leptin, resistin, apelin, and visfatin.

Enhancement of arterial pulsation during flow-mediated dilation is impaired in the presence of ischemic heart disease

Purpose

The aim of this study is to investigate the relationship between arterial pulse amplitude change under increased shear stress and the presence of ischemic heart disease (IHD).

Methods

This study comprised 31 subjects, including 14 subjects with IHD. We investigated the change in brachial artery pulse amplitude during flow-mediated dilation (FMD) using ultrasonography.

Results

The arterial pulse amplitude increased during FMD in 19 subjects, whereas it decreased in 12 subjects. There was a marked difference in the change in arterial pulse amplitude (the maximum amplitude of the arterial pulse amplitude during FMD/the arterial pulse amplitude at baseline) between subjects with and without IHD (0.98 ± 0.53 and 1.37 ± 0.53, p = 0.028). Furthermore, decreased arterial pulse amplitude during FMD was a significant predictor of IHD after adjustment of age, blood pressure, the presence of each type of coronary risks, the value of FMD and sex (p = 0.0001).

Conclusions

The decrease of arterial pulsation amplitude during FMD was a useful predictive parameter for IHD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2794-0) contains supplementary material, which is available to authorized users.

Obesity Related Coronary Microvascular Dysfunction: From Basic to Clinical Practice

Obesity related coronary microvascular disease is a medical entity which is not yet fully elucidated. The pathophysiological basis of coronary microcirculatory dysfunction consists of a heterogeneous group of disorders with individual morphologic/functional/clinical presentation and prognosis. Coronary microcirculatory changes include mechanisms connected with vascular dysfunction, as well as extravascular and vasostructural changes in responses to neural, mechanical, and metabolic factors. Cardiometabolic changes that include obesity, dyslipidemia, diabetes mellitus type II, and hypertension are associated with atherosclerosis of epicardial coronary arteries and/or microvascular coronary dysfunction, with incompletely understood underlying mechanisms. In obesity, microvascular disease is mediated via adipokines/cytokines causing chronic, subclinical inflammation with (a) reduced NO-mediated dilatation, (b) changed endothelial- and smooth muscle-dependent vasoregulating mechanisms, (c) altered vasomotor control with increased sympathetic activity, and (d) obesity related hypertension with cardiomyocytes hypertrophy and impaired cardiac vascular adaptation to metabolic needs. From a clinical point of view it can present itself in acute or chronic form with different prognosis, as a practice problem for real-life diagnosis and treatment.

Oxidative Stress-Dependent Coronary Endothelial Dysfunction in Obese Mice

Obesity is involved in several cardiovascular diseases including coronary artery disease and endothelial dysfunction. Endothelial Endothelium vasodilator and vasoconstrictor agonists play a key role in regulation of vascular tone. In this study, we evaluated coronary vascular response in an 8 weeks diet-induced obese C57BL/6 mice model. Coronary perfusion pressure in response to acetylcholine in isolated hearts from obese mice showed increased vasoconstriction and reduced vasodilation responses compared with control mice. Vascular nitric oxide assessed in situ with DAF-2 DA showed diminished levels in coronary arteries from obese mice in both basal and acetylcholine-stimulated conditions. Also, released prostacyclin was decreased in heart perfusates from obese mice, along with plasma tetrahydrobiopterin level and endothelium nitric oxide synthase dimer/monomer ratio. Obesity increased thromboxane A2 synthesis and oxidative stress evaluated by superoxide and peroxynitrite levels, compared with control mice. Obese mice treated with apocynin, a NADPH oxidase inhibitor, reversed all parameters to normal levels. These results suggest that after 8 weeks on a high-fat diet, the increase in oxidative stress lead to imbalance in vasoactive substances and consequently to endothelial dysfunction in coronary arteries.

Constrictor prostanoids and uridine adenosine tetraphosphate: vascular mediators and therapeutic targets in hypertension and diabetes

Vascular dysfunction plays a pivotal role in the development of systemic complications associated with arterial hypertension and diabetes. The endothelium, or more specifically, various factors derived from endothelial cells tightly regulate vascular function, including vascular tone. In physiological conditions, there is a balance between endothelium-derived factors, that is, relaxing factors (endothelium-derived relaxing factors; EDRFs) and contracting factors (endothelium-derived contracting factors; EDCFs), which mediate vascular homeostasis. However, in disease states, such as diabetes and arterial hypertension, there is an imbalance between EDRF and EDCF, with a reduction of EDRF signalling and an increase of EDCF signalling. Among EDCFs, COX-derived vasoconstrictor prostanoids play an important role in the development of vascular dysfunction associated with hypertension and diabetes. Moreover, uridine adenosine tetraphosphate (Up4 A), identified as an EDCF in 2005, also modulates vascular function. However, the role of Up4 A in hypertension- and diabetes-associated vascular dysfunction is unclear. In the present review, we focused on experimental and clinical evidence that implicate these two EDCFs (vasoconstrictor prostanoids and Up4 A) in vascular dysfunction associated with hypertension and diabetes.

Upregulation of SK3 and IK1 channels contributes to the enhanced endothelial calcium signaling and the preserved coronary relaxation in obese Zucker rats

Background and Aims

Endothelial small- and intermediate-conductance K_Ca channels, SK3 and IK1, are key mediators in the endothelium-derived hyperpolarization and relaxation of vascular smooth muscle and also in the modulation of endothelial Ca²⁺ signaling and nitric oxide (NO) release. Obesity is associated with endothelial dysfunction and impaired relaxation, although how obesity influences endothelial SK3/IK1 function is unclear. Therefore we assessed whether the role of these channels in the coronary circulation is altered in obese animals.

Methods and Results

In coronary arteries mounted in microvascular myographs, selective blockade of SK3/IK1 channels unmasked an increased contribution of these channels to the ACh- and to the exogenous NO- induced relaxations in arteries of Obese Zucker Rats (OZR) compared to Lean Zucker Rats (LZR). Relaxant responses induced by the SK3/IK1 channel activator NS309 were enhanced in OZR and NO- endothelium-dependent in LZR, whereas an additional endothelium-independent relaxant component was found in OZR. Fura2-AM fluorescence revealed a larger ACh-induced intracellular Ca²⁺ mobilization in the endothelium of coronary arteries from OZR, which was inhibited by blockade of SK3/IK1 channels in both LZR and OZR. Western blot analysis showed an increased expression of SK3/IK1 channels in coronary arteries of OZR and immunohistochemistry suggested that it takes place predominantly in the endothelial layer.

Conclusions

Obesity may induce activation of adaptive vascular mechanisms to preserve the dilator function in coronary arteries. Increased function and expression of SK3/IK1 channels by influencing endothelial Ca²⁺ dynamics might contribute to the unaltered endothelium-dependent coronary relaxation in the early stages of obesity.

Overnutrition, mTOR signaling, and cardiovascular diseases

The prevalence of obesity and associated medical disorders has increased dramatically in the United States and throughout much of the world in the past decade. Obesity, induced by excess intake of carbohydrates and fats, is a major cause of Type 2 diabetes, hypertension, and the cardiorenal metabolic syndrome. There is emerging evidence that excessive nutrient intake promotes signaling through the mammalian target of rapamycin (mTOR), which, in turn, may lead to alterations of cellular metabolic signaling leading to insulin resistance and obesity-related diseases, such as diabetes, cardiovascular and kidney disease, as well as cancer. While the pivotal role of mTOR signaling in regulating metabolic stress, autophagy, and adaptive immune responses has received increasing attention, there remain many gaps in our knowledge regarding this important nutrient sensor. For example, the precise cellular signaling mechanisms linking excessive nutrient intake and enhanced mTOR signaling with increased cardiovascular and kidney disease, as well as cancer, are not well understood. In this review, we focus on the effects that the interaction between excess intake of nutrients and enhanced mTOR signaling have on the promotion of obesity-associated diseases and potential therapeutic strategies involving targeting mTOR signaling.

Microvascular disorders in obese Zucker rats are restored by a rice bran diet

BACKGROUND AND AIM

Nutritional-based approaches aimed to prevent microvascular dysfunction associated to obesity present potential advantages over pharmacological strategies. Our aim was to test whether a rice bran enzymatic extract (RBEE)-supplemented diet could attenuate microvascular alterations in obese rats.

METHODS AND RESULTS

Lean and obese Zucker rats were fed standard diet supplemented or not with 1% and 5% RBEE for 20 weeks. Functional studies were performed in small mesenteric arteries in isometric myograph. Immunoblotting and fluorescence studies were made in arterial homogenates and arterial sections, respectively. RBEE-supplementation restored microvascular function in obese rats through a marked increase in NO and endothelial-derived hyperpolarizing factor contribution by up-regulation of eNOS and calcium-activated potassium channels expression, respectively, in association to a substantial reduction of microvascular inflammation and superoxide anion formation. These data agrees with the beneficial actions of RBEE on dyslipidemia, hyperinsulinemia and hypertension in obesity.

CONCLUSION

The multi-factorial properties of RBEE-diet, especially for restoring the function of small resistance arteries shows this dietary-based approach to be a promising candidate for prevention of microvascular alterations in obesity, which are crucial in cardiovascular events in obese subjects.

Autonomic nerves and perivascular fat: interactive mechanisms

The evidence describing the autonomic innervation of body fat is reviewed with a particular focus on the role of the sympathetic neurotransmitters. In compiling the evidence, a strong case emerges for the interaction between autonomic nerves and perivascular adipose tissue (PVAT). Adipocytes have been shown to express receptors for neurotransmitters released from nearby sympathetic varicosities such as adrenoceptors (ARs), purinoceptors and receptors for neuropeptide Y (NPY). Noradrenaline can modulate both lipolysis (via α2- and β3-ARs) and lipogenesis (via α1- and β3-ARs). ATP can inhibit lipolysis (via P1 purinoceptors) or stimulate lipolysis (via P2y purinoceptors). NPY, which can be produced by adipocytes and sympathetic nerves, inhibits lipolysis. Thus the sympathetic triad of transmitters can influence adipocyte free fatty acid (FFA) content. Substance P (SP) released from sensory nerves has also been shown to promote lipolysis. Therefore, we propose a mechanism whereby sympathetic neurotransmission can simultaneously activate smooth muscle cells in the tunica media to cause vasoconstriction and alter FFA content and release from adjacent adipocytes in PVAT. The released FFA can influence endothelial function. Adipocytes also release a range of vasoactive substances, both relaxing and contractile factors, including adiponectin and reactive oxygen species. The action of adipokines (such as adiponectin) and reactive oxygen species (ROS) on cells of the vascular adventitia and nerves has yet to be fully elucidated. We hypothesise a strong link between PVAT and autonomic fibres and suggest that this poorly understood relationship is extremely important for normal vascular function and warrants a detailed study.

A vascular piece in the puzzle of adipose tissue dysfunction: mechanisms and consequences

In the last years, several studies unravelled many aspects of adipose tissue pathophysiology in metabolic diseases. Some studies suggested hypoxia as one of such aspects, despite the exact mechanisms and pathophysiological significance is still partially unknown. Adipose tissue was shown to be hypoxic in obesity, mainly resulting from adipocyte hypertrophy, leading to increased activation of inflammatory pathways. In animal and cell models, hypoxia-induced inflammation was shown to lead to endocrine alterations and dysmetabolism. However, recent evidences suggest that instead of a simple low oxygenation theory, adipose tissue microvasculature may be regulated by a series of factors, including vasoactive factors like angiotensin II, angiogenesis and glycation, among others. This review summarizes the current knowledge about the role of these factors in the regulation of adipose tissue irrigation and the functional consequences of adipose tissue microvascular dysfunction.

Preserved endothelial function in human obesity in the absence of insulin resistance

Background

Insulin resistance (IR) is frequently associated with endothelial dysfunction and has been proposed to play a major role in cardiovascular disease (CVD). On the other hand, obesity has long been related to IR and increased CVD. However it is not known if IR is a necessary condition for endothelial dysfunction in human obesity, allowing for preserved endothelial function in obese people when absent. Therefore, the purpose of the study was to assess the relationship between IR and endothelial dysfunction in human obesity and the mechanisms involved.

Methods

Twenty non-insulin resistant morbid obese (NIR-MO), 32 insulin resistant morbid obese (IR-MO), and 12 healthy subjects were included. Serum concentrations of glucose, insulin, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), resistin and adiponectin were determined. IR was evaluated by HOMA-index. Endothelium-dependent relaxation to bradykinin (BK) in mesenteric microvessels was assessed in wire myograph.

Results

Serum IL-6, and TNF-α levels were elevated only in IR-MO patients while resistin was elevated and adiponectin reduced in all MO individuals. Mesenteric arteries from IR-MO, but not from NIR-MO subjects displayed blunted relaxation to BK. Vasodilatation was improved in IR-MO arteries by the superoxide scavenger, superoxide dismutase (SOD) or the mitochondrial-targeted SOD mimetic, mito-TEMPO. NADPH oxidase inhibitors (apocynin and VAS2870) and the nitric oxide synthase (NOS) cofactor, tetrahydrobiopterin failed to modify BK-induced vasodilatations. Superoxide generation was higher in vessels from IR-MO subjects and reduced by mito-TEMPO. Blockade of TNF-α with infliximab, but not inhibition of inducible NOS or cyclooxygenase, improved endothelial relaxation and decreased superoxide formation.

Conclusions

Endothelial dysfunction is observed in human morbid obesity only when insulin resistance is present. Mechanisms involved include augmented mitochondrial superoxide generation, and increased systemic inflammation mediated by TNF-α. These findings may explain the different vascular risk of healthy vs unhealthy obesity.

Obesity and statins are both independent predictors of enhanced coronary arteriolar dilation in patients undergoing heart surgery

Background

A paradoxical inverse relationship between body mass index, morbidity and mortality in patients with ischemic heart disease has been noted; but the underlying mechanisms remain unclear. Given that coronary resistance arteries are the primary regulators of myocardial blood flow, we examined the effects of obesity and medication on dilator function in coronary microvessels.

Methods

Bradykinin-induced coronary dilation was assessed by videomicroscopy in ex vivo coronary arterioles obtained from 64 consecutive patients undergoing heart surgery. Multi-variable linear regression and logistic regression were used to investigate the effects of obesity (BMI ≥ 30 kg/M²) and the influences of medications on vessel responses.

Results

In isolated, pressurized (80 mmHg) coronary arterioles of obese and non-obese patient the active (73±4 vs. 79±13 μm) and passive (111 ± 5.5 vs. 118 ± 5.0 μm) diameters were similar. Bradykinin elicited substantial dilation in coronary arterioles, with a similar magnitude in obese and non-obese patients (to 10^-8 M: 55 ± 5% vs. 46 ± 5%, P = 0.20), but with significantly enhanced sensitivity in obesity (EC50: 8.2x10^-9 M vs. 1.9x10^-8 M, respectively, P = 0.03). When adjusted for other risk factors and medications, obesity and statins were determined to be the only positive predictors of enhanced dilation, as assessed with multiple regression analysis. Moreover, obese patients with or without statin exhibited significantly increased coronary dilation to bradykinin, when compared to non-obese patients without statin therapy.

Conclusions

Obesity and statin therapy are independently associated with an enhanced dilator function of coronary arterioles in patients undergoing heart surgery, which may offer a potential mechanism for the better cardiovascular outcome described earlier as the obesity paradox.