ETB receptor-mediated vasodilation is regulated by estradiol in young women.

The endothelin-B (ETB) receptor is a key regulator of vascular endothelial function in women. We have previously shown that the ETB receptor mediates vasodilation in young women, an effect that is lost after menopause. However, the direct impact of changes in estradiol (E2) on ETB receptor function in women remains unclear. Therefore, the purpose of this study was to test the hypothesis that E2 exposure modulates ETB receptor-mediated dilation in young women. Fifteen young women (24 ± 4 yr, 24 ± 3 kg/m2) completed the study. Endogenous sex hormone production was suppressed with daily administration of a gonadotropin-releasing hormone antagonist (GnRHant; Ganirelix) for 10 days; E2 (0.1 mg/day, Vivelle-Dot patch) was added back on days 4-10. We measured vasodilation in the cutaneous microcirculation (microvascular endothelial function) via local heating (42°C) on day 4 (GnRHant) and day 10 (GnRHant + E2) using laser Doppler flowmetry coupled with intradermal microdialysis during perfusions of lactated Ringer's (control) and ETB receptor antagonist (BQ-788, 300 nM). During GnRHant, vasodilatory responses to local heating were enhanced with ETB receptor blockade (control: 83 ± 9 vs. BQ-788: 90 ± 5%CVCmax, P = 0.004). E2 administration improved vasodilation in the control site (GnRHant: 83 ± 9 vs. GnRHant + E2: 89 ± 8%CVCmax, P = 0.036). Furthermore, cutaneous vasodilatory responses during ETB receptor blockade were blunted after E2 administration (control: 89 ± 8 vs. BQ-788: 84 ± 8%CVCmax, P = 0.047). These data demonstrate that ovarian hormones, specifically E2, modulate ETB receptor function and contribute to the regulation of microvascular endothelial function in young women.NEW & NOTEWORTHY The endothelin-B (ETB) receptor mediates vasodilation in young women, an effect lost following menopause. It is unclear whether these alterations are due to aging or changes in estradiol (E2). During endogenous hormone suppression (GnRH antagonist), blockade of ETB receptors enhanced cutaneous microvascular vasodilation. However, during E2 administration, blockade of ETB receptors attenuated vasodilation, indicating that the ETB receptor mediates dilation in the presence of E2. In young women, ETB receptors mediate vasodilation in the presence of E2, an effect that is lost when E2 is suppressed.

Predicting Cardiometabolic Risk From Visceral Abdominal Adiposity in Persons With Chronic Spinal Cord Injury.

Persons with spinal cord injury (SCI) have increased adiposity that may predispose to cardiovascular disease compared to those who are able-bodied (AB). The purpose of this study was to determine the relationships between dual energy X-ray absorptiometry (DXA)-derived visceral adipose tissue (VAT) and biomarkers of lipid metabolism and insulin resistance in persons with chronic SCI. A prospective observational study in participants with chronic SCI and age- and gender-matched AB controls. The study was conducted at a Department of Veterans Affairs Medical Center and Private Rehabilitation Hospital. The quantification of DXA-derived VAT volume (VATvol) and blood-derived markers of lipid and carbohydrate metabolism were determined in 100 SCI and 51 AB men. The VATvol was acquired from a total body DXA scan and analyzed using iDXA enCore CoreScan software (GE Lunar). Blood samples were collected for the serum lipid profile and plasma and glucose concentrations, with the latter two values used to calculate a measure of insulin resistance. In the SCI and AB groups, VAT% was significantly correlated with most cardiometabolic biomarkers. The results of the binary logistic regression analysis revealed that participants who had a VATvol above the cutoff value of 1630 cm3 were 3.1-, 4.8-, 5.6-, 19.2-, and 16.7-times more likely to have high serum triglycerides (R2N= 0.09, p = 0.014), low serum high density lipoprotein cholesterol (R2N = 0.16, p < 0.001), HOMA2-IR (R2N = 0.18, p < 0.001), metabolic syndrome (R2N = 0.25, p < 0.001), and a 10-yr Framingham Risk Score ≥ 10% (R2N = 0.16, p = 0.001), respectively, when compared to participants below this VATvol cutoff value. Our findings reveal that persons with chronic SCI have a higher VATvol than that of AB controls, and VATvol correlates directly with biomarkers of lipid and carbohydrate metabolism that are strong predictors of cardiometabolic disorders.

Blood lipid markers are associated with hippocampal viscoelastic properties and memory in humans.

Age-related memory loss shares similar risk factors as cardiometabolic diseases including elevated serum triglycerides (TGs) and low-density lipoprotein cholesterol (LDL-C) and reduced high-density lipoprotein cholesterol (HDL-C). The mechanisms linking these aberrant blood lipids to memory loss are not completely understood but may be partially mediated by reduced integrity of the hippocampus (HC), the primary brain structure for encoding and recalling memories. In this study, we tested the hypothesis that blood lipid markers are independently associated with memory performance and HC viscoelasticity-a noninvasive measure of brain tissue microstructural integrity assessed by high-resolution magnetic resonance elastography (MRE). Twenty-six individuals across the adult lifespan were recruited (14 M/12 F; mean age: 42 ± 15 y; age range: 22-78 y) and serum lipid profiles were related to episodic memory and HC viscoelasticity. All subjects were generally healthy without clinically abnormal blood lipids or memory loss. Episodic memory was negatively associated with the TG/HDL-C ratio. HC viscoelasticity was negatively associated with serum TGs and the TG/HDL-C ratio, independent of age and in the absence of associations with HC volume. These data, although cross-sectional, suggest that subtle differences in blood lipid profiles in healthy adults may contribute to a reduction in memory function and HC tissue integrity.

Administration of Denosumab Preserves Bone Mineral Density at the Knee in Persons With Subacute Spinal Cord Injury: Findings From a Randomized Clinical Trial.

Persons with neurologically motor-complete spinal cord injury (SCI) have a marked loss of bone mineral density (BMD) of the long bones of the lower extremities, predisposing them to fragility fractures, especially at the knee. Denosumab, a commercially available human monoclonal IgG antibody to receptor activator of nuclear factor-κB ligand (RANKL), may provide an immunopharmacological solution to the rapid progressive deterioration of sublesional bone after SCI. Twenty-six SCI participants with subacute motor-complete SCI were randomized to receive either denosumab (60 mg) or placebo at baseline (BL), 6, and 12 months. Areal bone mineral density (aBMD) by dual energy x-ray absorptiometry (DXA) at 18 months at the distal femur was the primary outcome and aBMD of the proximal tibia and hip were the secondary outcomes analyzed in 18 of the 26 participants (denosumab, n = 10 and placebo, n = 8). The metrics of peripheral QCT (pQCT) were the exploratory outcomes analyzed in a subsample of the cohort (denosumab, n = 7 and placebo n = 7). The mean aBMD (±95% CI) for the denosumab versus the placebo groups demonstrated a significant group × time interactions for the following regions of interest at BL and 18 months: distal femoral metaphysis = mean aBMD 1.187; 95% CI, 1.074 to 1.300 and mean aBMD 1.202; 95% CI, 1.074 to 1.329 versus mean aBMD 1.162; 95% CI, 0.962 to 1.362 and mean aBMD 0.961; 95% CI, 0.763 to 1.159, respectively (p < 0.001); distal femoral epiphysis = mean aBMD 1.557; 95% CI, 1.437 to 1.675 and mean aBMD 1.570; 95% CI, 1.440 to 1.700 versus mean aBMD 1.565; 95% CI, 1.434 to 1.696 and mean aBMD 1.103; 95% CI, 0.898 to 1.309, respectively (p = 0.002); and proximal tibial epiphysis = mean aBMD 1.071; 95% CI, 0.957 to 1.186 and mean aBMD 1.050; 95% CI, 0.932 to 1.168 versus mean aBMD 0.994; 95% CI, 0.879 to 1.109 and mean aBMD 0.760; 95% CI, 0.601 to 0.919, respectively (p < 0.001). Analysis of pQCT imaging revealed a continued trend toward significantly greater loss in total volumetric BMD (vBMD) and trabecular vBMD at the 4% distal tibia region, with a significant percent loss for total bone mineral content. Thus, at 18 months after acute SCI, our findings show that denosumab maintained aBMD at the knee region, the site of greatest clinical relevance in the SCI population. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Cardiometabolic risk factors are associated with immune cell mitochondrial respiration in humans.

Modifiable cardiometabolic risk factors induce the release of proinflammatory cytokines and reactive oxygen species from circulating peripheral blood mononuclear cells (PBMCs), resulting in increased cardiovascular disease risk and compromised immune health. These changes may be driven by metabolic reprogramming of PBMCs, resulting in reduced mitochondrial respiration; however, this has not been fully tested. We aimed to determine the independent associations between cardiometabolic risk factors including BMI, blood pressure, fasting glucose, and plasma lipids with mitochondrial respiration in PBMCs isolated from generally healthy individuals (n = 21) across the adult lifespan (12 men/9 women; age, 56 ± 21 yr; age range, 22-78 yr; body mass index, 27.9 ± 5.7 kg/m2; blood pressure, 123 ± 16/72 ± 10 mmHg; glucose, 90 ± 14 mg/dL; low-density lipoprotein cholesterol (LDL-C), 111 ± 22 mg/dL; and high-density lipoprotein cholesterol (HDL-C), 62 ± 16 mg/dL). PBMCs were isolated from whole blood by density-dependent centrifugation and used to assess mitochondrial function by respirometry. Primary outcomes included basal and maximal oxygen consumption rate (OCR), which were subsequently used to determine spare respiratory capacity and OCR metabolic potential. After we corrected for systolic blood pressure (SBP), diastolic blood pressure (DBP), and blood glucose, LDL-C was negatively associated with maximal respiration (r = -0.56, P = 0.016), spare respiratory capacity (r = -0.58, P = 0.012), and OCR metabolic potential (r = -0.71, P = 0.0011). In addition, SBP was negatively associated with OCR metabolic potential (r = -0.62, P = 0.0056) after we corrected for DBP, blood glucose, and LDL-C. These data suggest a link between blood cholesterol, SBP, and mitochondrial health that may provide insight into how cardiometabolic risk factors contribute to impaired immune cell function.NEW & NOTEWORTHY Independent of other cardiometabolic risk factors, low-density lipoprotein cholesterol, and systolic blood pressure were found to be negatively associated with several parameters of mitochondrial respiration in peripheral blood mononuclear cells of healthy adults. These data suggest that low-density lipoprotein cholesterol and systolic blood pressure may induce metabolic reprogramming of immune cells, contributing to increased cardiovascular disease risk and impaired immune health.

Altered endothelial ETB receptor expression in postmenopausal women.

The endothelin system plays an important role in mediating vascular function. The endothelin-B receptor (ETBR) on endothelial cells mediates vasodilation via nitric oxide production. The vasodilatory effect of the ETBR is lost following menopause and may contribute to impaired vascular endothelial function in postmenopausal women (PMW). However, it is unclear if these functional changes are due to changes in ETBR expression on the endothelium. Therefore, the purpose of this study was to test the hypothesis that endothelial cell ETBR expression is lower in PMW compared with young women (YW). Primary endothelial cells were harvested from the antecubital vein of healthy PMW (n = 15, 60 ± 6 yr) and YW (n = 15, 22 ± 2 yr). Cells were identified as endothelial cells by staining for vascular endothelial cadherin, and nuclear integrity was assessed using 4',6-diamidino-2-phenylindole (DAPI). Within those cells, ETBR was quantified using immunocytochemistry; fluorescence intensity was measured in 30 cells and averaged for each participant. Endothelial function was assessed using brachial artery flow-mediated dilation (FMD). Endothelial cell ETBR expression was lower in PMW [0.46 ± 0.11 arbitrary units (AU)] compared with YW (0.58 ± 0.14 AU; P = 0.02). Furthermore, significant correlations between ETBR expression and FMD (r = 0.47, P < 0.01), total cholesterol (r = -0.38, P = 0.04), and LDL cholesterol (r = -0.39, P = 0.03) were observed. These data demonstrate that endothelial cell ETBR expression is attenuated in PMW. These novel findings provide additional insight into the mechanisms underlying vascular endothelial dysfunction in PMW.NEW & NOTEWORTHY Our study provides novel data demonstrating attenuated endothelial ETBR expression in postmenopausal women. Furthermore, our data extend current knowledge by demonstrating a positive relation between ETBR expression and brachial artery flow-mediated dilation. These findings provide additional mechanistic insight into vascular endothelial dysfunction in postmenopausal women.

Fenofibrate therapy to lower serum triglyceride concentrations in persons with spinal cord injury: A preliminary analysis of its safety profile.

Context: Fenofibrate is used to treat elevated serum triglyceride (TG) concentrations (e.g. ≥150 mg/dl). The lipoprotein profile of most individuals with spinal cord injury (SCI) would not satisfy conventional criteria to initiate lipid-lowering therapies. Serum TG concentrations of 115 and 137 mg/dl were recently identified as potential intervention thresholds for persons with a SCI proximal to the 4th and below the 5th thoracic vertebrae, respectively. Fenofibrate therapy has not been tested for safety in persons with SCI. Methods: An open-label trial was performed in 15 persons with SCI to determine the safety profile of 4 months of once-daily fenofibrate (145 mg tablet) treatment when initiated using modified intervention thresholds. Fasting blood tests and a review of systems were performed monthly to determine changes in liver and kidney function, as well as overall health status. Results: Fifteen subjects participated and 4 had an adverse event (e.g. 2 with gastrointestinal distress; 2 with elevated liver enzymes). Three subjects discontinued the trial within the first month and one participant remained in the trial with no further adverse events. Two participants were discontinued from fenofibrate after 2 months after not responding to treatment, as per protocol, and 10 participants completed the 4-month trial without experiencing an adverse event. Conclusion: In persons with SCI, 4 months of fenofibrate therapy initiated at lower threshold serum TG concentrations did not result in an increased incidence of adverse events compared to that reported in the general population. Fenofibrate therapy appears to be well tolerated in persons with SCI.

A Four Month Randomized Controlled Trial on the Efficacy of Once-daily Fenofibrate Monotherapy in Persons with Spinal Cord Injury.

An open-label, randomized clinical trial of once-daily fenofibrate monotherapy administered for 2- (Mo2) and 4- (Mo4) months using modified intervention thresholds for triglyceride (TG) was performed in persons with chronic spinal cord injury (SCI). Fenofibrate (145 mg tablet) was self-administered daily in 10 persons with SCI for 4 months with monthly blood testing to quantify the lipoprotein profile (e.g., serum TG, LDL-C, and HDL-C concentrations). Eight SCI participants were control subjects. In comparison to the control group, the treatment group at Mo2 had a 40% (±12%; p < 0.05) reduction in serum TG concentration, a 28% (±21%; p < 0.05) increase in HDL-C and 14% (±20%; p < 0.05) decline in LDL-C. In the same comparison at Mo4, the treatment group maintained a 40% (±20%; p < 0.05) reduction in serum TG concentration, had an 18% in reduction in LDL-C (±12%; p < 0.05) and a 23% (±23%; p < 0.05) increase in HDL-C. Fenofibrate monotherapy for Mo2 and Mo4 initiated in persons with SCI resulted in a robust and favorable change in the serum lipoprotein profile and ratios, suggesting reduced risk for cardiovascular disease.

Progressive Sublesional Bone Loss Extends into the Second Decade After Spinal Cord Injury.

OBJECTIVE: The rate of areal bone mineral density (aBMD) loss at the knee (distal femur (DF) and proximal tibia ) and hip (femoral neck (FN) and total hip (TH)) was determined in persons with traumatic spinal cord injury (SCI) who were stratified into subgroups based on time since injury (TSI). DESIGN: Cross-sectional retrospective review. SETTING: Department of Veterans Affairs Medical Center and Private Rehabilitation Hospital. PARTICIPANTS: Data on 105 individuals with SCI (TSI ≤12 months, n = 19; TSI 1-5 years, n = 35; 6-10 years, n = 19; TSI 11-20 years, n = 16; TSI >20 years, n = 15) and 17 able-bodied reference (ABref) controls. INTERVENTIONS: NA Main Outcome Measures: The knee and hip aBMD values were obtained by dual energy X-ray absorptiometry (GE Lunar iDXA) using standard clinical software for the proximal femur employed in conjunction with proprietary research orthopedic knee software applications. Young-normal (T-score) and age-matched (Z-scores) standardized scores for the FN and TH were obtained using the combined GE Lunar/National Health and Nutrition Examination Survey (NHANES III) combined reference database. RESULTS: When groups were stratified and compared as epochs of TSI, significantly lower mean aBMD and reference scores were observed as TSI increased, despite similar mean ages of participants among the majority of TSI epoch subgroups. Loss in aBMD occurred at the distal femur (DF), proximal tibia (PT), FN, and TH with 46%, 49%, 32%, and 43% of the variance in loss, respectively, described by the exponential decay curves with a time to steady state (tss) occurring at 14.6, 11.3, 14, and 6.2 years, respectively, after SCI. CONCLUSIONS: Sublesional bone loss after SCI was marked and occurred as an inverse function of TSI. For aBMD at the hip and knee, tss extended into the second decade after SCI.

Establishing a threshold to predict risk of cardiovascular disease from the serum triglyceride and high-density lipoprotein concentrations in persons with spinal cord injury.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: This report identified the serum triglyceride (TG) concentrations in persons with spinal cord injury (SCI) and able-bodied (AB) individuals that the serum high-density lipoprotein cholesterol (HDL-C) equaled 40 mg/dl, a concentration below which is an independent risk factor for coronary artery disease. METHODS: Retrospective analysis was performed on 578 participants: 223 with SCI at or proximal to the 4th thoracic vertebrae (↑T4), 178 with SCI at or distal to the 5th thoracic vertebrae (↓T5), and 177 AB. Different statistical modeling approaches identified the intersecting serum TG concentration with a serum HDL-C concentration equal to 40 mg/dl. Participants were dichotomized into subgroups by TG concentration exceeding (supra) or falling below (sub) the intersecting value and the TG/HDL-C ratios were compared. RESULTS: Linear regression analysis revealed that the serum TG concentration that intersects with serum HDL-C concentration at 40 mg/dl was 121 mg/dl in SCI ↑T4 and 137 mg/dl in SCI ↓T5 group. A ROC curve identified the optimal TG concentration as 115 mg/dl in SCI ↑T4 and 137 mg/dl in SCI ↓T5 group with the latter concentration being similar to the AB group (e.g., 137 mg/dl). The TG/HDL-C ratios in the respective ↑T4, ↓T5, and AB supra and subgroups were similar within each group. CONCLUSIONS: A lower TG concentration appears to be associated with dyslipidemia in persons with SCI than AB individuals. These findings should prompt clinicians to screen for and consider instituting lifestyle or pharmacological interventions at lower TG concentrations to reduce risk of CVD.

Bronchodilator effects of ipratropium bromide and albuterol sulfate among subjects with tetraplegia.

OBJECTIVE: In addition to lung volume restriction, persons with chronic tetraplegia demonstrate obstructive airway physiology evinced by pharmacologically-induced bronchodilation. We previously found independent evidence that anticholinergic agents (ipratropium bromide; IB) and beta-2 adrenergic agonists (albuterol sulfate; AS) were associated with significant bronchodilation in subjects with tetraplegia as determined via spirometry or body plethysmography. Direct comparison of these two classes of agents has received little attention. METHODS: Twelve subjects with chronic tetraplegia completed single dose treatment on alternate days with nebulized IB or AS. Patients underwent pre- and 30-minute post-bronchodilator spirometry, body plethysmography, and impulse oscillation system (IOS) in accordance with established protocols. RESULTS: Spirometry and specific airway conductance revealed significant bronchodilator responsiveness following both IB and AS. As determined by increases in specific airway conductance post-bronchodilator, IB tended toward greater bronchodilation than AS (71% vs. 47%). IOS revealed a greater reduction in central airway resistance (R20) following IB compared to AS (22% vs. 9%, P < 0.01). A greater number of subjects exhibited a clinically significant reduction in R20 following IB compared to AS (58% vs. 8%, P < 0.01). CONCLUSION: Among subjects with tetraplegia, both IB and AS elicit significant bronchodilation, although the magnitude of the bronchodilator response is greater following IB. This lends support to theory of overriding cholinergic airway tone in tetraplegia. The IOS findings further suggest that the predominant site of action of IB is upon the larger central airways congruent with findings in able-bodied subjects.

Delivery of neostigmine and glycopyrrolate by iontophoresis: a nonrandomized study in individuals with spinal cord injury.

STUDY DESIGN: Phase I Clinical Trial. OBJECTIVES: In this proof-of-principle study, the effectiveness and safety of transdermal administration of neostigmine/glycopyrrolate to elicit a bowel movement was compared to intravenous administration in patients with spinal cord injury. SETTING: James J. Peters Veterans Affairs Medical Center (Bronx, NY). METHODS: Individuals were screened for responsiveness (Physical Response) to intravenous neostigmine (0.03 mg/kg)/glycopyrrolate (0.006 mg/kg). Intravenous neostigmine/glycopyrrolate responders (Therapeutic Response) were administered low-dose transdermal neostigmine/glycopyrrolate [(0.05 mg/kg)/(0.01 mg/kg)] by iontophoresis. Non-responders to low-dose transdermal neostigmine/glycopyrrolate were administered high-dose transdermal neostigmine/glycopyrrolate [(0.07 mg/kg)/(0.014 mg/kg)] by iontophoresis. Bowel movement, bowel evacuation time, and cholinergic side effects were recorded. Visits were separated by 2 to 14 days. RESULTS: Eighteen of 25 individuals (72.0%) had a bowel movement (20 ± 22 min) after intravenous neostigmine/glycopyrrolate. Of these 18 individuals, 5 individuals experienced a bowel movement with low-dose transdermal neostigmine/glycopyrrolate. Another five individuals had a bowel movement after high-dose transdermal neostigmine/glycopyrrolate administration. Fewer side effects were observed in individuals who received neostigmine/glycopyrrolate transdermally compared to those who were administered intravenous neostigmine/glycopyrrolate. CONCLUSIONS: Transdermal administration of neostigmine/glycopyrrolate by iontophoresis appears to be a practical, safe, and effective approach to induce bowel evacuation in individuals with spinal cord injury.

Cutaneous microvascular perfusion responses to insulin iontophoresis are differentially affected by insulin resistance after spinal cord injury.

NEW FINDINGS: What is the central question of this study? What impact does insulin resistance have on cutaneous perfusion responses to insulin iontophoresis in vascular beds with markedly reduced or functionally ablated sympathetic nervous system vasomotor function resulting from spinal cord injury? What is the main finding and its importance? Persons with spinal cord injury have sublesional microvascular endothelial dysfunction, as indicated by a blunted cutaneous perfusion response to acetylcholine iontophoresis, and the presence of insulin resistance has a further confounding effect on endothelium-mediated changes to cutaneous perfusion in the lower extremities. Endothelium-mediated mechanisms that regulate skin blood flow might play an integral role in optimizing skin perfusion in vascular beds with sympathetic nervous system vasomotor impairment, such as in spinal cord injury (SCI). Insulin is a vasoactive hormone and second messenger of nitric oxide that facilitates endothelium-mediated dilatation. The effects of insulin resistance (IR) on sublesional cutaneous perfusion responses to insulin provocation have yet to be described in persons with SCI. Persons with SCI and an able-bodied (AB) cohort were divided into subgroups based upon fasting plasma insulin concentration cut-offs for IR (≥13.13 mIU ml-1 ) or insulin sensitivity (IS; <13.13 mIU ml-1 ), as follows: AB, IS (ABIS, n = 21); SCI, IS (SCIS, n = 21); AB, IR (ABIR, n = 9); and SCI, IR (SCIR, n = 11). Laser Doppler flowmetry characterized peak blood perfusion unit (BPU) responses (percentage change from baseline) to insulin, acetylcholine or placebo iontophoresis in the lower extremities; BPU responses were log10 transformed to facilitate comparisons, and the net insulin response (NetIns) BPU response was calculated (insulin minus placebo BPU response). The NetIns was significantly greater in both IS groups compared with their corresponding IR group. The acetylcholine-mediated BPU responses in the SCI subgroups were significantly lower than those in the ABIS group. The proportional BPU responses of NetIns to acetylcholine in the IS cohorts (i.e. ABIS and SCIS) were significantly greater (P < 0.05) than that of each IR subgroup. The presence of IR has a confounding effect on sublesional microvascular endothelium-mediated cutaneous perfusion responses to provocation. Preservation of endothelial sensitivity to its agonists appears to be an important modifiable risk factor to optimize cutaneous perfusion in the lower extremities of persons with SCI.