Citations

Introduction: The metabolic syndrome (MetS) leads to cardiac vascular injury, which may reflect in increased retention of endothelial progenitor cells (EPC). Coronary endothelial cell (EC) mitochondria partly regulate vascular function and structure. We hypothesized that chronic mitoprotection would preserve EC mitochondria and attenuate coronary vascular injury and dysfunction in swine MetS. Methods: Pigs were studied after 16 weeks of diet-induced MetS, MetS treated for the last 4 weeks with the mitochondria-targeted peptide elamipretide (ELAM, 0.1mg/kg SC q.d), and lean controls (n=6 each). Coronary artery and sinus blood samples were collected. EC mitochondrial density (electron microscopy), endothelial nitric oxide (eNOS) immunoreactivity (staining), myocardial microvascular density (3D micro-CT), and coronary endothelial function (organ bath) were assessed ex-vivo. The number and arteriovenous gradient of CD34+/KDR+ EPC was calculated by FACS (a negative gradient indicating EPC retention). Results: MetS and MetS+ELAM pigs developed similar MetS (obesity, hyperlipidemia, insulin resistance, and hypertension). EC mitochondrial density decreased in MetS compared to lean, but normalized in MetS+ELAM. ELAM also improved eNOS immunoreactivity, subendocardial microvascular density, and coronary endothelial function. ELAM-induced vasculoprotection was reflected in decreased coronary retention of EPCs. Conclusions: These observations underscore the role of mitochondria in regulating the cardiac circulation in experimental MetS, and the benefits of mitoprotection to preserve EC myocardial microvascular integrity.

Determinants of Intra-renal oxygenation in human RVD are poorly understood. Blood oxygen level-dependent (BOLD) MRI measures deoxyhemoglobin (R2*) to determine cortical and medullary R2* which have focal variations and gradients. We hypothesized that tissue fractional hypoxia (% of axial kidney area with R2*>30s -1 ) would correlate better with tissue perfusion, renal blood flow (RBF), and O2 consumption than using regions of interest (ROI). METHODS: Inpatient studies were performed in EH (n=68 kidneys), and high-grade RVD (n=18 kidneys, 71±5.5% occlusion) before and 3 months after stents. All were treated with ACE/ARB Rx and thiazides during 150 mEq/d Na+ intake. BOLD MR images were obtained at 3T before and after furosemide (20mg IV), and axial images analyzed to estimate R2* levels above 30s -1 (fractional hypoxia) over the entire kidney section. Maximal R2* levels using regions of interest (ROIs) also were determined. Single-kidney cortical and medullary RBF (ml/min) perfusion (ml/min/cc) were determined by MDCT. Results: RBF was lower in kidneys with untreated RVD than EH (285.6±141 vs. 399±159 ml/min p<0.05), as was cortical perfusion (2.58±.63 vs. 3.50±1.05, p<.05 ). Cortical and medullary R2* did not differ, but fractional hypoxia was greater in RVD as compared to EH (18.3±12 vs. 11.5±8.5%, p<.05). Fractional hypoxia was inversely correlated with blood flow (R=-.29, p<.01) and perfusion (R=-.26, p<.01). R2* fell after furosemide (p<0.01) indicating a role for O2 consumption in determining tissue hypoxia. RBF and cortical perfusion increased after stenting (285±141 vs. 318±178 ml/min and 2.58±0.6 vs. 2.9±0.7ml/min/cc, p<0.05) respectively. Fractional hypoxia, but not cortical or medullary R2* based on ROI-methods, decreased in patients 3 months after renal revascularization (18.3 ±12 vs. 10.52%, p<0.05) Conclusions: These data demonstrate for the first time that fractional hypoxia in the kidney is directly related to chronically reduced blood flow and cortical perfusion in human RVD, whereas selective ROI-based measures identified only minor changes in peak R2* gradients between cortex and medulla. The reversibility of fractional hypoxia after stenting supports the use of this new method to identify critical renovascular lesions.

Background: Atherosclerotic renal artery stenosis (ARAS) reduces renal blood flow (RBF) and amplifies regional kidney hypoxia, but their relationship to tissue inflammation and injury markers is poorly understood. We tested the hypothesis that renal injury, reflected by renal vein levels of neutrophil gelatinase associated lipocalin (NGAL) and inflammatory cytokines monocyte chemoattractant protein-1 (MCP-1) would be magnified with severe occlusive vascular disease in humans with ARAS. Methods: Inpatient studies performed in patients with ARAS (n=40, 71.3±11% occlusion by CT angiography) or essential hypertension (EH) (n=30), during fixed Na+ intake and ACE/ARB Rx. Single-kidney cortical and medullary perfusion and RBF were measured using multidetector CT, and glomerular filtration rate (GFR) by iothalamate clearance. Tissue deoxyhemoglobin levels (R2*) and fractional kidney hypoxia (% of axial area with R2*>30/s) were measured by BOLD-MRI at 3T. Results: Single kidney RBF, cortical and medullary perfusion were reduced in the post-stenotic kidney, as was GFR. Renal vein NGAL, MCP-1 and fractional hypoxia were higher in patients with ARAS than EH. NGAL and MCP-1 levels correlated directly with cortical R2* and fractional hypoxia (r = 0.52, P <0 .0001 and r = 0.4, P = 0.0006) and with the degree of artey stenosis (r = 0.37, P = 0.04 and r = 0.35, P = 0.05). GFR correlated inversely with NGAL (r= - 0.5, P <0.0001). Conclusions: Our results demonstrate that elevated renal venous markers of kidney inflammation (MCP-1) and injury (NGAL) in ARAS are correlated with the severity of tissue hypoxia as measured by BOLD MR, suggesting a possible link between kidney inflammation and hypoxia.

Background: Renal hypoxia is a complex function of post-glomerular medullary blood flow, active solute transport and is considered a major risk element for acute kidney injury. Previous studies indicate that sodium balance, diuretic administration and some drugs affect tissue oxygenation. Water loading in younger subjects lowers medullary deoxyhemoglobin. We sought to evaluate the effects of water loading on the day of BOLD imaging in older subjects undergoing protocol evaluation of atherosclerotic renovascular disease (ARVD). METHODS: Inpatient studies were performed in patients with hemodynamically severe ARVD (n=15, Doppler US velocity >270 cm/sec), during 150 mEq Na+ intake and ACE/ARB Rx. Two groups were studied: Group A (n=10) received oral water loading (20 ml/kg), whereas Group B (n=5) had none. Tissue R2* (index of deoxyhemoglobin levels) and fractional kidney hypoxia (medullary estimate) (% of renal coronal area with R2*>20/s) were measured in stenotic kidneys by BOLD-MRI at 3T, before and after IV injection of Furosemide (20gm). RESULTS: Cortical R2* and fractional tissue hypoxia were similar for the 2 groups (P =0.6 and 0.7). Both groups reduced cortical R2* and fractional hypoxia after furosemide injection to the same degree. Table CONCLUSION: These data demonstrate that water loading on the day of BOLD evaluation in older subjects with ARVD does not materially alter cortical or medullary estimates of oxygenation. Our results extend previous studies indicating that water loading in older individuals fails to alter medullary oxygenation unlike alterations in sodium intake, diuretic administration or blockade of the renin-angiotensin system.

Introduction: Coronary vasomotor response is different between males and females. Overall, females have lower coronary flow reserve (CFR) than males due to higher baseline coronary flow than males. Hypothesis: Sex has an essential role in the interaction between age and CFR. Methods: We included 668 patients with nonobstructive coronary artery disease who underwent invasive coronary vasoreactivity testing using intracoronary incremental doses of adenosine (18-72 μg). Changes in CFR (hyperemic flow velocity/baseline flow velocity) with aging were separately analyzed between males (N=207, mean age 53±13 years) and females (N=461, mean age 54±12 years). We further divided patients by age of 53 which is average age of menopause. Results: In males, CFR decreased with aging in younger patients <53 years and tended to decrease in older male patients (all ages [N=207]: r=-0.33, P <0.0001; <53 years [N=99]: r=-0.27, P =0.01; ≥53 years [N=108]: r=-0.17, P =0.07) ( Figure A ). In contrast, CFR did not decrease with aging in younger females <53 years, whereas there was a significant negative correlation between CFR and age in older females ≥53 years (all ages [N=461]: r=-0.15, P =0.001; <53 years [N=211]: r=-0.006, P =0.39; ≥53 years [N=250]: r=-0.25, P <0.0001) ( Figure B ). Baseline microvascular resistance (BMR) was similar between younger and older males ( P =0.30), whereas older females had higher baseline BMR than younger females ( P <0.0001) ( Figure C ). Conclusions: CFR decreased with aging in males and older females, but not in younger females, potentially highlighting the role of protective hormonal differences in maintaining low baseline coronary tone in younger females.

Background: The expansion of adipose mass requires adipocyte precursor cells that originate from multipotent mesenchymal stem cells (MSC). The inflammatory milieu in obesity often involves high levels of tumor necrosis factor (TNF)-α in adipose tissue, but whether this affects MSC function remains unknown. We tested the hypothesis that microenvironmental changes during the evolution of obesity affect MSC function, which may in turn promote obesity. Methods: Domestic pigs were fed with an adipogenic (n=7) or normal (n=7) diet for 16 weeks. Abdominal adipose tissue biopsies were collected at 8, 12, and 16 weeks for histology and MSC culture. Adipose tissue inflammation and MSC levels were evaluated in situ using immunohistochemistry staining for TNF-α, CD34, and Von Willebrand factor (vWF). The adipogenic propensity of MSC was tested in vitro using appropriate differentiation media, with or without supplementation of TNF-α or anti-TNF-α antibody for 3 weeks. Results: Obese pigs had increased body weight and abdominal fat mass (by CT) compared with lean pigs. TNF-α expression in adipose tissue (Figure 1A) was upregulated in obese pigs at 12 and 16 weeks, accompanied by increased numbers of MSC (CD34 + /vWF - ) at 16 weeks. In vitro, MSC derived from obese adipose tissue at 16weeks showed enhanced adipogenesis, which was abolished by anti-TNF-α treatment. Similarly, in lean MSC TNF-α treatment enhanced adipogenesis (Figure 1B). Conclusion: Obesity-induced adipose tissue inflammation may stimulate MSC differentiation into adipocytes, which further increase the adipose tissue mass. Our results support development of anti-inflammatory strategies for obesity management.

Background: Coronary endothelial dysfunction(CED) may reflect loss of vascular integrity and permeability. We aimed to test the hypothesis that CED may be associated with increased risk of bleeding events. Methods: Coronary vascular reactivity was evaluated in 444 patients with non-obstructive coronary arteries by administration of intracoronary acetylcholine during angiography. CED was defined as a ≤ 50% increase in coronary blood flow (CBF) from baseline in response to maximal dose of acetylcholine. After a median follow-up of 7 years, patients were assessed for the occurrence of any significant bleeding events. Results: Of 444 patients, 70.7% (314) were female. Average age was 52.3 years. Of 252 patients with CED, 7.9% (20) developed bleeding events compared to 2.1% (4 of 192) without CED (p=0.004). Patients who developed bleeding events had a lower percent change in CBF vs. those who did not median: (IQR) 14.1 (-28.1, 98.7) vs. 40.0 (-11.0, 103.5); p=0.03 (Figure 1). CED was significantly associated with the development of bleeding in univariate analysis(p=0.004, relative risk: 3.81 CI, 1.32, 10.96). In multivariate analysis CED was an independent predictor of development of bleeding (p=0.01) Conclusions: CED is associated with increased risk of bleeding events. This can be explained by the altered vascular function that is inherent to CED. This study underscores the systemic involvement of the endothelium in vascular disease, and the concept of the ‘vulnerable patient’.

Background A growing body of evidence links coronary artery atherosclerosis and calcification to osteoporosis in women. Coronary endothelial dysfunction (CED) is associated with adverse cardiovascular events. We aimed to study the association of CED and development of osteoporosis. Methods Coronary vascular reactivity was evaluated in 225 women, greater than age 50, with non-obstructive coronary arteries, by administration of intracoronary acetylcholine during diagnostic angiography. CED was defined as <50% increase in coronary blood flow (CBF) from baseline in response to maximal dose. After a median follow-up of 7 years, patients were assessed by a questionnaire for development of osteoporosis. Results The average age of the cohort was 60 years. Of 225 women, 60% (135) had CED. 18.2% (41 of 225 women) developed osteoporosis during follow-up. Women with CED were twice more likely to develop osteoporosis vs. women without CED (23% vs. 11.1%, p=0.024). Women who developed osteoporosis compared to those who did not had a markedly lower response (% change) in CBF: median (IQR)-4.3 (-28.3, 51.7) vs. 39.9 (-8.2, 106.0), p=0.007. In univariate analysis, CED was significantly associated with development of osteoporosis (p=0.024, relative risk 2.07, 95% CI: 1.07, 4.00). Multivariate analysis indicated CED as an independent predictor of osteoporosis (p=0.04). Discussion Endothelial dysfunction may account for or share similar mechanisms with development of osteoporosis in cardiac patients.

Background Elevated plasma ceramides are independent predictors of cardiovascular disease and mortality in patients with advanced epicardial coronary artery disease. Our understanding of plasma ceramides in early epicardial coronary artery disease, however, remains limited. We examined the role of plasma ceramides in early coronary atherosclerosis characterized by coronary endothelial dysfunction. Methods and Results Participants presenting with chest pain and nonobstructive epicardial coronary artery disease underwent coronary endothelial function. Patients (n=90) demonstrated abnormal coronary endothelial function with acetylcholine (≥20% decrease in coronary artery diameter or ≤50% increase in coronary blood flow). A total of 30 controls had normal coronary endothelial function. Concentrations of plasma ceramide 18:0 ( P =0.038), 16:0 ( P =0.021), and 24:0 ( P =0.019) differed between participants with normal and abnormal coronary endothelial function. Ceramide 24:0 (odds ratio [OR], 2.23 [95% CI, 1.07–4.66]; P =0.033) and 16:0 (OR, 1.91×10 6 [95% CI, 11.93–3.07×10 11 ]; P =0.018) were independently associated with coronary endothelial dysfunction. Among participants with endothelium‐dependent coronary dysfunction (n=78), ceramides 16:0 (OR, 5.17×10 5 [95% CI, 2.83–9.44×10 10 ]; P =0.033), 24:0 (OR, 2.98 [95% CI, 1.27–7.00]; P =0.012), and 24:1/24:0 (OR, 4.39×10 −4 [95% CI, 4×10 −7 –0.48]; P =0.030) were more likely to be elevated. Conclusions The current study demonstrated an association between increased circulating ceramide levels and coronary endothelial dysfunction in the absence of epicardial coronary artery disease. This study supports the role of plasma ceramides as a potential biomarker or a therapeutic target for early coronary atherosclerosis in humans.