Association between dietary phosphate intake and skeletal muscle energetics in adults without cardiovascular disease

Highly bioavailable inorganic phosphate (Pi) is present in large quantities in the typical Western diet and represents a large fraction of total phosphate intake. Dietary Pi excess induces exercise intolerance and skeletal muscle mitochondrial dysfunction in normal mice. However, the relevance of this to humans remains unknown. The study was conducted on 13 individuals without a history of cardiopulmonary disease (46% female, 15% Black participants) enrolled in the pilot-phase of the Dallas Heart and Mind Study. Total dietary phosphate was estimated from 24-h dietary recall (ASA24). Muscle ATP synthesis was measured at rest, and phosphocreatinine (PCr) dynamics was measured during plantar flexion exercise using 7-T 31P magnetic resonance (MR) spectroscopy in the calf muscle. Correlation was assessed between dietary phosphate intake normalized to total caloric intake, resting ATP synthesis, and PCr depletion during exercise. Higher dietary phosphate intake was associated with lower resting ATP synthesis (r = -0.62, P = 0.03), and with higher levels of PCr depletion during plantar flexion exercise relative to the resting period (r = -0.72; P = 0.004). These associations remain significant after adjustment for age and estimated glomerular filtration rate (both P < 0.05). High dietary phosphate intake was also associated with lower serum Klotho levels, and Klotho levels are in turn associated with PCr depletion and higher ADP accumulation post exercise. Our study suggests that higher dietary phosphate is associated with reduced skeletal muscle mitochondrial function at rest and exercise in humans providing new insight into potential mechanisms linking the Western diet to impaired energy metabolism.NEW & NOTEWORTHY This is the first translational research study directly demonstrating the adverse effects of dietary phosphate on muscle energy metabolism in humans. Importantly, our data show that dietary phosphate is associated with impaired muscle ATP synthesis at rest and during exercise, independent of age and renal function. This is a new biologic paradigm with significant clinical dietary implications.

Management of Resistant Hypertension-An Update

This JAMA Internal Medicine Clinical Insights review provides an update on the current recommendations for resistant hypertension management.

HDL-C and apolipoprotein A-I are independently associated with skeletal muscle mitochondrial function in healthy humans

Prior animal and cell studies have demonstrated a direct role of high-density lipoprotein (HDL) and apolipoprotein A-I (ApoA-I) in enhancing skeletal muscle mitochondrial function and exercise capacity. However, the relevance of these animal and cell investigations in humans remains unknown. Therefore, a cross-sectional study was conducted in 48 adults (67% female, 8% Black participants, age 39 ± 15.4 yr old) to characterize the associations between HDL measures, ApoA-I, and muscle mitochondrial function. Forearm muscle oxygen recovery time (tau) from postexercise recovery kinetics was used to assess skeletal muscle mitochondrial function. Lipoprotein measures were assessed by nuclear magnetic resonance. HDL efflux capacity was assessed using J774 macrophages, radiolabeled cholesterol, and apolipoprotein B-depleted plasma both with and without added cyclic adenosine monophosphate. In univariate analyses, faster skeletal muscle oxygen recovery time (lower tau) was significantly associated with higher levels of HDL cholesterol (HDL-C), ApoA-I, and larger mean HDL size, but not HDL cholesterol efflux capacity. Slower recovery time (higher tau) was positively associated with body mass index (BMI) and fasting plasma glucose (FPG). In multivariable linear regression analyses, higher levels of HDL-C and ApoA-I, as well as larger HDL size, were independently associated with faster skeletal muscle oxygen recovery times that persisted after adjusting for BMI and FPG (all P < 0.05). In conclusion, higher levels of HDL-C, ApoA-I, and larger mean HDL size were independently associated with enhanced skeletal muscle mitochondrial function in healthy humans.NEW & NOTEWORTHY Our study provides the first direct evidence supporting the beneficial role of HDL-C and ApoA-I on enhanced skeletal muscle mitochondrial function in healthy young to middle-aged humans without cardiometabolic disease.

Preventing cognitive decline by reducing BP target (PCOT): A randomized, pragmatic, multi-health systems clinical trial

BACKGROUND

Growing evidence suggests that intensive lowering of systolic blood pressure (BP) may prevent mild cognitive impairment (MCI) and dementia. However, current guidelines provide inconsistent recommendations regarding optimal BP targets, citing safety concerns of excessive BP lowering in the diverse population of older adults. We are conducting a pragmatic trial to determine if an implementation strategy to reduce systolic BP to <130 and diastolic BP to <80 mmHg will safely slow cognitive decline in older adults with hypertension when compared to patients receiving usual care.

METHODS

The Preventing Cognitive Decline by Reducing BP Target Trial (PCOT) is an embedded randomized pragmatic clinical trial in 4000 patients from two diverse health-systems who are age ≥ 70 years with BP >130/80 mmHg. Participants are randomized to the intervention arm or usual care using a permuted block randomization within each health system. The intervention is a combination of team-based care with clinical decision support to lower home BP to <130/80 mmHg. The primary outcome is cognitive decline as determined by the change in the modified Telephone Interview for Cognitive Status (TICS-m) scores from baseline. As a secondary outcome, patients who decline ≥3 points on the TICS-m will complete additional cognitive assessments and this information will be reviewed by an expert panel to determine if they meet criteria for MCI or dementia.

CONCLUSION

The PCOT trial will address the effectiveness and safety of hypertension treatment in two large health systems to lower BP targets to reduce risk of cognitive decline in real-world settings.

Potassium Magnesium Citrate Is Superior to Potassium Chloride in Reversing Metabolic Side Effects of Chlorthalidone

BACKGROUND

Thiazide diuretics (TD) are the first-line treatment of hypertension because of its consistent benefit in lowering blood pressure and cardiovascular risk. TD is also known to cause an excess risk of diabetes, which may limit long-term use. Although potassium (K) depletion was thought to be the main mechanism of TD-induced hyperglycemia, TD also triggers magnesium (Mg) depletion. However, the role of Mg supplementation in modulating metabolic side effects of TD has not been investigated. Therefore, we aim to determine the effect of potassium magnesium citrate (KMgCit) on fasting plasma glucose and liver fat by magnetic resonance imaging during TD therapy.

METHODS

Accordingly, we conducted a double-blinded RCT in 60 nondiabetic hypertension patients to compare the effects of KCl versus KMgCit during chlorthalidone treatment. Each patient received chlorthalidone alone for 3 weeks before randomization. Primary end point was the change in fasting plasma glucose after 16 weeks of KCl or KMgCit supplementation from chlorthalidone alone.

RESULTS

The mean age of subjects was 59±11 years (30% Black participants). Chlorthalidone alone induced a significant rise in fasting plasma glucose, and a significant fall in serum K, serum Mg, and 24-hour urinary citrate excretion (all P<0.05). KMgCit attenuated the rise in fasting plasma glucose by 7.9 mg/dL versus KCl (P<0.05), which was not observed with KCl. There were no significant differences in liver fat between the 2 groups.

CONCLUSIONS

KMgCit is superior to KCl, the common form of K supplement used in clinical practice, in preventing TD-induced hyperglycemia. This action may improve tolerability and cardiovascular safety in patients with hypertension treated with this drug class.

Diagnostic performance of the adrenal vein to inferior vena cava aldosterone ratio in classifying the subtype of primary aldosteronism

Adrenal vein sampling (AVS) is the standard procedure for distinguishing unilateral primary aldosteronism (PA) from bilateral PA. In cases where only one adrenal vein is successfully cannulated, it has been suggested that subtype classification can be determined based on the ratio of the concentration of aldosterone between the adrenal vein and the inferior vena cava (AV/IVC index). However, diagnostic performance of the ipsilateral versus contralateral AV/IVC index in predicting lateralization has not been directly compared. In a retrospective cohort of 133 patients with confirmed PA who underwent successful AVS, the performance of the AV/IVC index to predict laterality was evaluated and the area under the receiver operating characteristic (AUROC) curves was calculated. In detecting left unilateral PA (n = 47), the AUROC of the right AV/IVC index (RAV/IVC) was significantly higher than the AUROC of the left AV/IVC (LAV/IVC) index (0.967 vs. 0.871, p = 0.008). In detecting right unilateral PA (n = 30), the AUROC of the LAV/IVC index tended to be higher than that of the RAV/IVC index, but the difference did not reach statistical significance (0.966 vs. 0.906, p = 0.08). In detecting left unilateral PA, the sensitivities of the RAV/IVC and LAV/IVC indices were 83% and 46%, respectively, while the specificities of both were above 90%. In detecting right unilateral PA, the sensitivities of the LAV/IVC and RAV/IVC indices were 80% and 43%, respectively, while the specificities of both were above 90%. The AV/IVC index has superior diagnostic performance in detecting contralateral unilateral PA compared to ipsilateral unilateral PA.

Recruitment methods and yield rates for a multisite clinical trial exploring risk reduction for Alzheimer's disease (rrAD)

INTRODUCTION

The risk reduction for Alzheimer's disease (rrAD) trial was a multisite clinical trial to assess exercise and intensive vascular pharmacological treatment on cognitive function in community-dwelling older adults at increased risk for Alzheimer's disease.

METHODS

Eligibility, consent, and randomization rates across different referral sources were compared. Informal interviews conducted with each site's project team were conducted upon study completion.

RESULTS

Initially, 3290 individuals were screened, of whom 28% were eligible to consent, 805 consented to participate (87.2% of those eligible), and 513 (36.3% of those consented) were randomized. Emails sent from study site listservs/databases yielded the highest amount (20.9%) of screened individuals. Professional referrals from physicians yielded the greatest percentage of consented individuals (57.1%). Referrals from non-professional contacts (ie, friends, family; 75%) and mail/phone contact from a site (73.8%) had the highest yield of randomization.

DISCUSSION

Professional referrals or email from listservs/registries were most effective for enrolling participants. The greatest yield of eligible/randomized participants came from non-professional and mail/phone contacts. Future trials should consider special efforts targeting these recruitment approaches.

Highlights

Clinical trial recruitment is commonly cited as a significant barrier to advancing our understanding of cognitive health interventions.The most cited referral source was email, followed by interviews/editorials on the radio, television, local newspapers, newsletters, or magazine articles.The referral method that brought in the largest number of contacts was email but did not result in the greatest yield of consents or eligible participants.The sources that yielded the greatest likelihood of consent were professional referrals (ie, physician), social media, and mail/phone contact from study site.The greatest yield of eligible/randomized participants came from non-professional contacts and mail/phone contact from a site.Findings suggest that sites may need to focus on more selective referral sources, such as using contact mailing and phone lists, rather than more widely viewed recruitment sources, such as social media or TV/radio advertisements.

Utility of standing office blood pressure in detecting hypertension in healthy adults

Current guidelines recommend office blood pressures (BP) be taken in a seated position when screening for hypertension (HTN). Seated BP is known to have limited accuracy in detecting high BP, while the utility of standing BP in diagnosing HTN is unknown. We conducted a cross-sectional study to determine the incremental value of standing BP in diagnosing HTN. Seated, standing, and 24-h ambulatory BPs (ABPM) were obtained in adults without known cardiovascular disease, HTN, or BP medication use. Presence of HTN was defined by the 2017 ACC/AHA and the 2023 ESH HTN guidelines based on ABPM. Area under the receiver-operating-characteristic curve (AUROC) was used to evaluate the diagnostic accuracy of seated and standing BP. Sensitivity and specificity of standing BP was determined using cut-offs derived from Youden's Index, while sensitivity and specificity of seated BP was determined using the cut-off of 130/80 mmHg and by 140/90 mmHg. Among 125 participants (mean age 49 ± 17 years; 62% female; 24% Black), 33.6% of them had HTN. Sensitivity and specificity of seated systolic BP (SBP) was 43% and 92%, respectively. Cut-offs selected by Youden's index for standing SBP/diastolic BP (DBP) were 124/81 mmHg according to the 2017 ACC/AHA HTN guidelines, and 123.5/83.5 mmHg according to the 2023 ESH HTN guidelines. Sensitivity and specificity of standing SBP was 71% and 67%, respectively. The AUROC of standing SBP (0.81 [0.71-0.92]) was significantly higher than seated SBP (0.70 [0.49-0.91]), when HTN was defined as average 24-h SBP ≥ 125 mmHg. Moreover, the addition of standing to seated SBP (0.80 [0.68-0.92]) improved HTN detection when compared to seated SBP. These patterns were consistent for both the 2017 ACC/AHA and the 2023 ESH definitions for HTN. In summary, standing BP, alone or in combination with seated BP, outperformed seated BP alone in diagnosing HTN in adults.

Blockade of endogenous insulin receptor signaling in the nucleus tractus solitarius potentiates exercise pressor reflex function in healthy male rats

Insulin not only regulates glucose and/or lipid metabolism but also modulates brain neural activity. The nucleus tractus solitarius (NTS) is a key central integration site for sensory input from working skeletal muscle and arterial baroreceptors during exercise. Stimulation of the skeletal muscle exercise pressor reflex (EPR), the responses of which are buffered by the arterial baroreflex, leads to compensatory increases in arterial pressure to supply blood to working muscle. Evidence suggests that insulin signaling decreases neuronal excitability in the brain, thus antagonizing insulin receptors (IRs) may increase neuronal excitability. However, the impact of brain insulin signaling on the EPR remains fully undetermined. We hypothesized that antagonism of NTS IRs increases EPR function in normal healthy rodents. In decerebrate rats, stimulation of the EPR via electrically induced muscle contractions increased peak mean arterial pressure (MAP) responses 30 min following NTS microinjections of an IR antagonist (GSK1838705, 100 μM; Pre: Δ16 ± 10 mmHg vs. 30 min: Δ23 ± 13 mmHg, n = 11, p = .004), a finding absent in sino-aortic baroreceptor denervated rats. Intrathecal injections of GSK1838705 did not influence peak MAP responses to mechano- or chemoreflex stimulation of the hindlimb muscle. Immunofluorescence triple overlap analysis following repetitive EPR stimulation increased c-Fos overlap with EPR-sensitive nuclei and IR-positive cells relative to sham operation (p < .001). The results suggest that IR blockade in the NTS potentiates the MAP response to EPR stimulation. In addition, insulin signaling in the NTS may buffer EPR stimulated increases in blood pressure via baroreflex-mediated mechanisms during exercise.

Hypertension in Patients Treated With In-Center Maintenance Hemodialysis: Current Evidence and Future Opportunities: A Scientific Statement From the American Heart Association

Nearly 500 000 individuals are treated with maintenance hemodialysis for kidney failure in the United States, and roughly half will die of cardiovascular causes. Hypertension, an important and modifiable risk factor for cardiovascular disease, is observed in >80% of patients treated with maintenance hemodialysis. The pathophysiology of hypertension in patients treated with maintenance hemodialysis is multifactorial and differs from that seen in other patient populations. Factors that contribute to hypertension in patients treated with hemodialysis include volume overload, arterial stiffness, enhanced activity of the sympathetic nervous and renin-angiotensin-aldosterone systems, endothelial dysfunction, and use of erythropoietin-stimulating agents. This scientific statement reviews the current evidence on defining, diagnosing, and treating hypertension in patients treated with maintenance hemodialysis and highlights opportunities for future investigation, including studies on blood pressure targets and treatment strategies.

Neural discharge of muscle afferents and pressor response to mechanical stimulation are associated with muscle deformation velocity in rats

Skeletal muscle reflexes play a crucial role in determining the magnitude of the cardiovascular response to exercise. However, evidence supporting an association between the magnitude of the pressor response and velocity of muscle deformation has remained to be elucidated. Thus, we investigated the impact of different muscle deformation rates on the neural discharge of muscle afferents as well as pressor and sympathetic responses in Sprague-Dawley rats. In an ex vivo muscle-nerve preparation, action potentials elicited by sinusoidal mechanical stimuli (137 mN) at different frequencies (0.01, 0.05, 0.1, 0.2, and 0.25 Hz) were recorded in mechanosensitive group III and IV fibers. The afferent response magnitude to sine-wave stimulation significantly varied at different frequencies (ANOVA, P=0.025). Specifically, as compared to 0.01 Hz (0.83±0.96 spikes/s), the response magnitudes were significantly greater at 0.20 Hz (4.07±5.04 spikes/s, P=0.031) and 0.25 Hz (4.91±5.30 spikes/s, P=0.014). In an in vivo decerebrated rat preparation, renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) responses to passive stretch (1kg) of hindlimb skeletal muscle at different velocities of loading (slow, medium, fast) was measured. Pressor responses to passive stretch were significantly associated with velocity of muscle deformation (ANOVA, P<0.001); The MAP response to fast stretch (Δ 56±12 mmHg) was greater than slow (Δ 33±11 mmHg, P=0.006) or medium (Δ 30±11 mmHg, P<0.001). Likewise, the RSNA response was related to deformation velocity (ANOVA, P=0.024). These findings suggest that muscle neural afferent discharge and the cardiovascular response to mechanical stimulation are associated with muscle deformation velocity.

Antagonism of TRPV4 channels partially reduces mechanotransduction in rat skeletal muscle afferents

Mechanical distortion of working skeletal muscle induces sympathoexcitation via thin fibre afferents, a reflex response known as the skeletal muscle mechanoreflex. However, to date, the receptor ion channels responsible for mechanotransduction in skeletal muscle remain largely undetermined. Transient receptor potential vanilloid 4 (TRPV4) is known to sense mechanical stimuli such as shear stress or osmotic pressure in various organs. It is hypothesized that TRPV4 in thin-fibre primary afferents innervating skeletal muscle is involved in mechanotransduction. Fluorescence immunostaining revealed that 20.1 ± 10.1% of TRPV4 positive neurons were small dorsal root ganglion (DRG) neurons that were DiI-labelled, and among them 9.5 ± 6.1% of TRPV4 co-localized with the C-fibre marker peripherin. In vitro whole-cell patch clamp recordings from cultured rat DRG neurons demonstrated that mechanically activated current amplitude was significantly attenuated after the application of the TRPV4 antagonist HC067047 compared to control (P = 0.004). Such reductions were also observed in single-fibre recordings from a muscle-nerve ex vivo preparation where HC067047 significantly decreased afferent discharge to mechanical stimulation (P = 0.007). Likewise, in an in vivo decerebrate rat preparation, the renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) responses to passive stretch of hindlimb muscle were significantly reduced by intra-arterial injection of HC067047 (ΔRSNA: P = 0.019, ΔMAP: P = 0.002). The findings suggest that TRPV4 plays an important role in mechanotransduction contributing to the cardiovascular responses evoked by the skeletal muscle mechanoreflex during exercise. KEY POINTS: Although a mechanical stimulus to skeletal muscle reflexively activates the sympathetic nervous system, the receptors responsible for mechanotransduction in skeletal muscle thin fibre afferents have not been fully identified. Evidence suggests that TRPV4 is a mechanosensitive channel that plays an important role in mechanotransduction within various organs. Immunocytochemical staining demonstrates that TRPV4 is expressed in group IV skeletal muscle afferents. In addition, we show that the TRPV4 antagonist HC067047 decreases the responsiveness of thin fibre afferents to mechanical stimulation at the muscle tissue level as well as at the level of dorsal root ganglion neurons. Moreover, we demonstrate that intra-arterial HC067047 injection attenuates the sympathetic and pressor responses to passive muscle stretch in decerebrate rats. These data suggest that antagonism of TRPV4 attenuates mechanotransduction in skeletal muscle afferents. The present study demonstrates a probable physiological role for TRPV4 in the regulation of mechanical sensation in somatosensory thin fibre muscle afferents.

Greater resting muscle sympathetic nerve activity reduces cold pressor autonomic reactivity in older women, but not older men

Previous work demonstrates augmented muscle sympathetic nerve activity (MSNA) responses to the cold pressor test (CPT) in older women. Given its interindividual variability, however, the influence of baseline MSNA on CPT reactivity in older adults remains unknown. Sixty volunteers (60-83y; 30 women) completed testing where MSNA (microneurography), blood pressure (BP), and heart rate (HR) were recorded during baseline and a 2-min CPT (~4°C). Participant data were terciled by baseline MSNA (n=10/group); comparisons were made between the high baseline men (HM) and women (HW), and low baseline men (LM) and women (LW). By design, HM and HW, vs. LM and LW, had greater baseline MSNA burst frequency (37±5 and 38±3 vs. 9±4 and 15±5 bursts/min) and burst incidence (59±14 and 60±8 vs. 16±10 and 23±7 bursts/100hbs; both P<0.001). However, baseline BP and HR were not different between the groups (all P>0.05). During the CPT, there were no differences in the increase in BP and HR (all P>0.05). Conversely, ΔMSNA burst frequency was lower in HW vs. LW (8±9 vs. 22±12 bursts/min; P=0.012) yet was similar in HM vs. LM (17±12 vs. 19±10 bursts/min, P=0.994). Further, ΔMSNA burst incidence was lower in HW vs. LW (9±13 vs. 28±16 bursts/100hbs; P=0.020), with no differences between HM vs. LM (21±17 vs. 31±17 bursts/100hbs; P=0.455). Our findings suggest that heightened baseline activity in older women attenuates the typical CPT-mediated increase in MSNA without changing cardiovascular reactivity. While the underlying mechanisms remain unknown, altered sympathetic recruitment or neurovascular transduction may contribute to these disparate responses.

Evaluation of noise regression techniques in resting-state fMRI studies using data of 434 older adults

Subject motion is a well-known confound in resting-state functional MRI (rs-fMRI) and the analysis of functional connectivity. Consequently, several clean-up strategies have been established to minimize the impact of subject motion. Physiological signals in response to cardiac activity and respiration are also known to alter the apparent rs-fMRI connectivity. Comprehensive comparisons of common noise regression techniques showed that the "Independent Component Analysis based strategy for Automatic Removal of Motion Artifacts" (ICA-AROMA) was a preferred pre-processing technique for teenagers and adults. However, motion and physiological noise characteristics may differ substantially for older adults. Here, we present a comprehensive comparison of noise-regression techniques for older adults from a large multi-site clinical trial of exercise and intensive pharmacological vascular risk factor reduction. The Risk Reduction for Alzheimer's Disease (rrAD) trial included hypertensive older adults (60-84 years old) at elevated risk of developing Alzheimer's Disease (AD). We compared the performance of censoring, censoring combined with global signal regression, non-aggressive and aggressive ICA-AROMA, as well as the Spatially Organized Component Klassifikator (SOCK) on the rs-fMRI baseline scans from 434 rrAD subjects. All techniques were rated based on network reproducibility, network identifiability, edge activity, spatial smoothness, and loss of temporal degrees of freedom (tDOF). We found that non-aggressive ICA-AROMA did not perform as well as the other four techniques, which performed table with marginal differences, demonstrating the validity of these techniques. Considering reproducibility as the most important factor for longitudinal studies, given low false-positive rates and a better preserved, more cohesive temporal structure, currently aggressive ICA-AROMA is likely the most suitable noise regression technique for rs-fMRI studies of older adults.

Comparison of Pharmacy Refill Data With Chemical Adherence Testing in Assessing Medication Nonadherence in a Safety Net Hospital Setting

Background Pharmacy fill data are a practical tool for assessing medication nonadherence. However, previous studies have not compared the accuracy of pharmacy fill data to measurement of plasma drug levels, or chemical adherence testing (CAT). Methods and Results We performed a cross-sectional study in patients with uncontrolled hypertension in outpatient clinics in a safety net health system. Plasma samples were obtained for measurement of common cardiovascular drugs, including calcium channel blockers, thiazide diuretics, beta blockers, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, and statins, using liquid chromatography mass spectrometry. Proportion of days covered (PDC), a method for tracking pharmacy fill data, was calculated via linkages with Surescripts, and its diagnostic test characteristics were compared with CAT. Among 77 patients with uncontrolled hypertension, 13 (17%) were nonadherent to at least 1 antihypertensive drug and 23 (37%) were nonadherent to statins by CAT. PDC was significantly lower in the nonadherent versus the adherent group by CAT only among patients prescribed an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker or statin (all P<0.05) but not in patients prescribed other drug classes. The sensitivity and specificity of PDC in detecting nonadherence to angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and statin drugs by CAT were 75% to 82% and 56% to 79%, respectively. The positive predictive value of PDC in detecting nonadherence was only 11% to 27% for antihypertensive drugs and 45% for statins. Conclusions PDC is useful in detecting nonadherence to angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and statins but has limited usefulness in detecting nonadherence to calcium channel blockers, beta blockers, or thiazide diuretics and has a low positive predictive value for all drug classes.

Renal denervation in the antihypertensive arsenal - knowns and known unknowns

Even though it has been more than a decade since renal denervation (RDN) was first used to treat hypertension and an intense effort on researching this therapy has been made, it is still not clear how RDN fits into the antihypertensive arsenal. There is no question that RDN lowers blood pressure (BP), it does so to an extent at best corresponding to one antihypertensive drug. The procedure has an excellent safety record. However, it remains clinically impossible to predict whose BP responds to RDN and whose does not. Long-term efficacy data on BP reduction are still unconvincing despite the recent results in the SPYRAL HTN-ON MED trial; experimental studies indicate that reinnervation is occurring after RDN. Although BP is an acceptable surrogate endpoint, there is complete lack of outcome data with RDN. Clear indications for RDN are lacking although patients with resistant hypertension, those with documented increase in activity of the sympathetic system and perhaps those who desire to take fewest medication may be considered.

Abstract P208: Utility Of Standing Office Blood Pressure In Assessing Blood Pressure Control In Patients With Autonomic Failure

Current guidelines recommend blood pressure (BP) target based on office BP taken in a seated position for hypertensive patients. However, the accuracy of standing BP measurements for determining blood pressure control in patients with autonomic (ATF) is unknown.We measured BP in seated and standing positions in 47 hypertensive and normotensive adults with ATF. Office BP was measured in the seated position 3 times and after standing for 3 minutes. Adequate BP control was defined by 24-hour ambulatory SBP/DBP of < 125/75 mmHg. Area under receiver operator characteristic curve (AUROC) was calculated to determine accuracy of seated and standing BP in assessing BP control. Bayes factor (BF) was used to assess the significance of the difference between AUROC of seated and standing BP. Sensitivity and specificity of standing BP in determining blood pressure control was derived using cut-off points derived from Youden’s Index.Prevalence of HTN was 72% (34/47) and the mean age was 71 ± 11 years. Sensitivity and specificity of seated SBP was 65% and 73%, respectively. Optimal cutoffs selected by Youden’s index for standing SBP/DBP was 104/83 mmHg. Sensitivity and specificity of standing SBP was 96% and 64%, respectively. The AUROC of standing SBP was significantly higher when compared to seated SBP alone, when controlled SBP was defined as 24-Hr SBP < 125 mmHg (BF > 3). Similarly, when controlled SBP was defined as daytime SBP < 130 mmHg, the AUROC of 3 rd standing was significantly higher when compared to seated SBP alone or in combination (BF > 3).In conclusion, standing SBP is more useful than seated SBP in assessing BP control in patients with ATF.

Abstract P011: Usefulness Of Standing Office Blood Pressure In Detecting Hypertension In Untreated Adults

Clinical guidelines recommend office blood pressures (BP) to be taken in a seated position. However, the accuracy of standing BP measurements for diagnosing hypertension (HTN) has not been investigated. We assessed BP in both seated and standing positions in 125 healthy adults not on anti-HTN medications. HTN was defined by 24-hour ambulatory SBP/DBP of ≥ 125/75 mmHg. Area under receiver operator characteristic curve (AUROC) was calculated to determine accuracy of seated and standing BP in diagnosing HTN. Bayes factor (BF) was used to assess the significance of the difference between AUROC of seated and standing BP. Sensitivity and specificity of standing BP in diagnosing HTN was derived using cut-off points derived from Youden’s Index. Our cohort’s mean age was 49 ± 17 years, with 62% female (77 of 125), and 24% Black (30 of 125). Prevalence of HTN was 33.6% (42 of 125). Sensitivity and specificity of seated SBP was 43% and 92%, respectively. Optimal cutoffs selected by Youden’s index for standing SBP/DBP was 124/81 mmHg. Sensitivity and specificity of standing SBP was 74% and 65%, respectively. The AUROC of standing SBP was significantly higher than seated SBP (BF =11.8), when HTN was defined as 24-Hr SBP ≥ 125 mmHg (Fig 1). Similarly, when HTN was defined as 24-Hr DBP ≥ 75 mmHg or daytime DBP ≥ 80 mmHg, the AUROC of standing DBP was higher than seated DBP (all BF >3). The addition of standing to seated BP improved HTN detection than seated BP alone based on 24-Hr SBP/DBP ≥ 125/75 mmHg or daytime SBP/DBP ≥ 130/80 mmHg (all BF >3). In conclusion, standing office BPs both alone and in combination with seated BPs, outperformed seated BPs in diagnosing hypertension in untreated adults.

Abstract P209: Ambulatory Arterial Stiffness Index In Detecting Autonomic Failure

Previous studies have shown standard deviation (SD) of daytime ambulatory systolic BP (DaySBP) as a screening tool for detecting autonomic failure. While ambulatory arterial stiffness index (AASI) has shown to be a predictor of cardiovascular morbidity and mortality, the usefulness of AASI in detecting the presence of autonomic failure has not been investigated.

We assessed AASI in 336 hypertensive and normotensive adults with and without autonomic failure (ATF). Area under receiver operator characteristic curve (AUROC) was calculated to determine accuracy of AASI in detecting ATF. Bayes factor (BF) was used to assess the significance of the difference between AUROC of AASI compared to SD daytime SBP and AASI combined with SD daytime SBP compared to SD daytime SBP alone. Sensitivity and specificity of AASI in detecting autonomic failure was derived using cut-off points from Youden’s Index.

Prevalence of ATF in our cohort was 14 % (47/336). The prevalence of HTN was 55 % (184/336). The mean age of the ATF group was higher than the control group (71 ± 11 vs. 61 ± 14 years, respectively, p < 0.05). The mean AASI of ATF patients was higher than control group (0.58 ± 0.11 vs. 0.51 ± 0.15, respectively, p < 0.05). The AUROC of AASI in ATF detection was not significantly higher than SD daytime SBP (BF =0.12). Sensitivity and specificity of AASI was 87 % and 43 %, respectively. The optimal cutoff for AASI selected by Youden’s index was 0.48. The addition of AASI to SD daytime SBP significantly improved ATF detection compared to AASI alone (BF > 3, Fig 1).

In conclusion, AASI in combination with SD DaySBP significantly outperformed AASI alone in detecting autonomic failure in patients with or without HTN.

Dapagliflozin Attenuates Sympathetic and Pressor Responses to Stress in Young Prehypertensive Spontaneously Hypertensive Rats

BACKGROUND

SGLT2i (sodium-glucose cotransporter 2 inhibitor), a class of anti-diabetic medications, is shown to reduce blood pressure (BP) in hypertensive patients with type 2 diabetes. Mechanisms underlying this action are unknown but SGLT2i-induced sympathoinhibition is thought to play a role. Whether SGLT2i reduces BP and sympathetic nerve activity (SNA) in a nondiabetic prehypertension model is unknown.

METHODS

Accordingly, we assessed changes in conscious BP using radiotelemetry and alterations in mean arterial pressure and renal SNA during simulated exercise in nondiabetic spontaneously hypertensive rats during chronic administration of a diet containing dapagliflozin (0.5 mg/kg per day) versus a control diet.

RESULTS

We found that dapagliflozin had no effect on fasting blood glucose, insulin, or hemoglobin A_1C levels. However, dapagliflozin reduced BP in young (8-week old) spontaneously hypertensive rats as well as attenuated the age-related rise in BP in adult spontaneously hypertensive rat up to 17-weeks of age. The rises in mean arterial pressure and renal SNA during simulated exercise (exercise pressor reflex activation by hindlimb muscle contraction) were significantly reduced after 4 weeks of dapagliflozin (Δmean arterial pressure: 10±7 versus 25±14 mm Hg, Δrenal SNA: 31±17% versus 68±39%, P<0.05). Similarly, rises in mean arterial pressure and renal SNA during mechanoreflex stimulation by passive hindlimb stretching were also attenuated by dapagliflozin. Heart weight was significantly decreased in dapagliflozin compared with the control group.

CONCLUSIONS

These data demonstrate a novel role for SGLT2i in reducing resting BP as well as the activity of skeletal muscle reflexes, independent of glycemic control. Our study may have important clinical implications for preventing hypertension and hypertensive heart disease in young prehypertensive individuals.

MEN2B Masquerading as Postural Orthostatic Tachycardia Syndrome

Multiple endocrine neoplasia type 2B is a genetic disorder characterized by pheochromocytoma, medullary thyroid carcinoma, and marfanoid features. Although hypertension and stress cardiomyopathy are known cardiovascular complications of pheochromocytoma, clinical presentation maybe subtle. Elevation in heart rate and lightheadedness induced by catecholamine excess may mimic clinical features of postural orthostatic tachycardia syndrome, as shown in our case report. (Level of Difficulty: Advanced.)

Renal Nerve Activity and Arterial Depressor Responses Induced by Neuromodulation of the Deep Peroneal Nerve in Spontaneously Hypertensive Rats

Hypertension is a main cause of death in the United States with more than 103 million adults affected. While pharmacological treatments are effective, blood pressure (BP) remains uncontrolled in 50–60% of resistant hypertensive subjects. Using a custom-wired miniature electrode, we previously reported that deep peroneal nerve stimulation (DPNS) elicited acute cardiovascular depressor responses in anesthetized spontaneously hypertensive rats (SHRs). Here, we further study this effect by implementing a wireless system and exploring different stimulation parameters to achieve a maximum depressor response. Our results indicate that DPNS consistently induces a reduction in BP and suggests that renal sympathetic nerve activity (RSNA) is altered by this bioelectronic treatment. To test the acute effect of DPNS in awake animals, we developed a novel miniaturized wireless microchannel electrode (w-μCE), with a Z-shaped microchannel through which the target nerves slide and lock into the recording/stimulation chamber. Animals implanted with w-μCE and BP telemetry systems for 3 weeks showed an average BP of 150 ± 14 mmHg, which was reduced significantly by an active DPNS session to 135 ± 8 mmHg (p &lt; 0.04), but not in sham-treated animals. The depressor response in animals with an active w-μCE was progressively returned to baseline levels 14 min later (164 ± 26 mmHg). This depressor response was confirmed in restrained fully awake animals that received DPNS for 10 days, where tail-cuff BP measurements showed that systolic BP in SHR lowered 10% at 1 h and 16% 2 h after the DPNS when compared to the post-implantation baseline. Together, these results support the use of DPN neuromodulation as a possible strategy to lower BP in drug-resistant hypertension.

Influence of Age and Estradiol on Sympathetic Nerve Activity Responses to Exercise in Women

INTRODUCTION

Postmenopausal women (PMW) display exaggerated increases in blood pressure (BP) during exercise, yet the mechanism(s) involved remain unclear. Moreover, research on the impact of menopausal changes in estradiol on cardiovascular control during exercise are limited. Herein, we tested the hypothesis that sympathetic responses during exercise are augmented in PMWcompared with young women (YW), and estradiol administration attenuates these responses.

METHODS

Muscle sympathetic nerve activity (MSNA) and mean arterial pressure (MAP) were measured in 13 PMW (58 ± 1 yr) and 17 YW (22 ± 1 yr) during 2 min of isometric handgrip. Separately, MSNA and BP responses were measured during isometric handgrip in six PMW (53 ± 1 yr) before and after 1 month of transdermal estradiol (100 μg·d-1). A period of postexercise ischemia (PEI) to isolate muscle metaboreflex activation followed all handgrip bouts.

RESULTS

Resting MAP was similar between PMW and YW, whereas MSNA was greater in PMW (23 ± 3 vs 8 ± 1 bursts per minute; P < 0.05). During handgrip, the increases in MSNA (PMW Δ16 ± 2 vs YW Δ6 ± 1 bursts per minute; P < 0.05) and MAP (PMW Δ18 ± 2 vs YW Δ12 ± 2 mm Hg; P < 0.05) were greater in PMW and remained augmented during PEI. Estradiol administration decreased resting MAP but not MSNA in PMW. Moreover, MSNA (PMW (-E2) Δ27 ± 8 bursts per minute versus PMW (+E2) Δ12 ± 5 bursts per minute; P < 0.05) and MAP (Δ31 ± 8 mm Hg vs Δ20 ± 6 mm Hg; P < 0.05) responses during handgrip were attenuated in PMW after estradiol administration. Likewise, MAP responses during PEI were lower after estradiol.

CONCLUSIONS

These data suggest that PMW exhibit an exaggerated MSNA and BP response to isometric exercise, due in part to heightened metaboreflex activation. Furthermore, estradiol administration attenuated BP and MSNA responses to exercise in PMW.

Insulin potentiates the response to capsaicin in dorsal root ganglion neurons in vitro and muscle afferents ex vivo in normal healthy rodents

Systemic insulin administration evokes sympathoexcitatory actions, but the mechanisms underlying these observations are unknown. We reported that insulin sensitizes the response of thin-fibre primary afferents, as well as the dorsal root ganglion (DRG) that subserves them, to mechanical stimuli. However, little is known about the effects of insulin on primary neuronal responses to chemical stimuli. TRPV1, whose agonist is capsaicin (CAP), is widely expressed on chemically sensitive metaboreceptors and/or nociceptors. The aim of this investigation was to determine the effects of insulin on CAP-activated currents in small DRG neurons and CAP-induced action potentials in thin-fibre muscle afferents of normal healthy rodents. Additionally, we investigated whether insulin potentiates sympathetic nerve activity (SNA) responses to CAP. In whole-cell patch-clamp recordings from cultured mice DRG neurons in vitro, the fold change in CAP-activated current from pre- to post-application of insulin (n = 13) was significantly (P < 0.05) higher than with a vehicle control (n = 14). Similar results were observed in single-fibre recording experiments ex vivo as insulin potentiated CAP-induced action potentials compared to vehicle controls (n = 9 per group, P < 0.05). Furthermore, insulin receptor blockade with GSK1838705 significantly suppressed the insulin-induced augmentation in CAP-activated currents (n = 13) as well as the response magnitude of CAP-induced action potentials (n = 9). Likewise, the renal SNA response to CAP after intramuscular injection of insulin (n = 8) was significantly (P < 0.05) greater compared to vehicle (n = 9). The findings suggest that insulin potentiates TRPV1 responsiveness to CAP at the DRG and muscle tissue levels, possibly contributing to the augmentation in sympathoexcitation during activities such as physical exercise. KEY POINTS: Evidence suggests insulin centrally activates the sympathetic nervous system, and a chemical stimulus to tissues activates the sympathetic nervous system via thin fibre muscle afferents. Insulin is reported to modulate putative chemical-sensitive channels in the dorsal root ganglion neurons of these afferents. In the present study, it is demonstrated that insulin potentiates the responsiveness of thin fibre afferents to capsaicin at muscle tissue levels as well as at the level of dorsal root ganglion neurons. In addition, it is demonstrated that insulin augments the sympathetic nerve activity response to capsaicin in vivo. These data suggest that sympathoexcitation is peripherally mediated via insulin-induced chemical sensitization. The present study proposes a possible physiological role of insulin in the regulation of chemical sensitivity in somatosensory thin fibre muscle afferents.

Medication Adherence and Blood Pressure Control: A Scientific Statement From the American Heart Association

The widespread treatment of hypertension and resultant improvement in blood pressure have been major contributors to the dramatic age-specific decline in heart disease and stroke. Despite this progress, a persistent gap remains between stated public health targets and achieved blood pressure control rates. Many factors may be important contributors to the gap between population hypertension control goals and currently observed control levels. Among them is the extent to which patients adhere to prescribed treatment. The goal of this scientific statement is to summarize the current state of knowledge of the contribution of medication nonadherence to the national prevalence of poor blood pressure control, methods for measuring medication adherence and their associated challenges, risk factors for antihypertensive medication nonadherence, and strategies for improving adherence to antihypertensive medications at both the individual and health system levels.

Arteriovenous Fistula Maturation, Functional Patency, and Intervention Rates

Importance

National initiatives have emphasized the use of autogenous arteriovenous fistulas (AVFs) for hemodialysis, but their purported benefits have been questioned.

Objective

To examine AVF usability, longer-term functional patency, and remedial procedures to facilitate maturation, manage complications, or maintain patency in the Hemodialysis Fistula Maturation (HFM) Study.

Design, Setting, and Participants

The HFM Study was a multicenter (n = 7) prospective National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases cohort study performed to identify factors associated with AVF maturation. A total of 602 participants were enrolled (dialysis, kidney failure: 380; predialysis, chronic kidney disease [CKD]: 222) with AVF maturation ascertained for 535 (kidney failure, 353; CKD, 182) participants.

Interventions

All clinical decisions regarding AVF management were deferred to the individual centers, but remedial interventions were discouraged within 6 weeks of creation.

Main Outcomes and Measures

In this case series analysis, the primary outcome was unassisted maturation. Functional patency, freedom from intervention, and participant survival were summarized using Kaplan-Meier analysis.

Results

Most participants evaluated (n = 535) were men (372 [69.5%]) and had diabetes (311 [58.1%]); mean (SD) age was 54.6 (13.6) years. Almost two-thirds of the AVFs created (342 of 535 [64%]) were in the upper arm. The AVF maturation rates for the kidney failure vs CKD participants were 29% vs 10% at 3 months, 67% vs 38% at 6 months, and 76% vs 58% at 12 months. Several participants with kidney failure (133 [37.7%]) and CKD (63 [34.6%]) underwent interventions to facilitate maturation or manage complications before maturation. The median time from access creation to maturation was 115 days (interquartile range [IQR], 86-171 days) but differed by initial indication (CKD, 170 days; IQR, 113-269 days; kidney failure, 105 days; IQR, 81-137 days). The functional patency for the AVFs that matured at 1 year was 87% (95% CI, 83.2%-90.2%) and at 2 years, 75% (95% CI, 69.7%-79.7%), and there was no significant difference for those receiving interventions before maturation. Almost half (188 [47.5%]) of the AVFs that matured had further intervention to maintain patency or treat complications.

Conclusions and Relevance

The findings of this study suggest that AVF remains an accepted hemodialysis access option, although both its maturation and continued use require a moderate number of interventions to maintain patency and treat the associated complications.

Abstract P133: Prevalence Of Medication Non-adherence Via Therapeutic Drug Monitoring In Patients With Uncontrolled Hypertension Treated At A Safety Net Hospital

Background: Medication nonadherence presents one of the greatest challenges to hypertension management. Previous studies from our group have shown therapeutic drug monitoring (TDM), biochemical monitoring of drug levels, is more accurate than self-report, detailed questionnaires, or prescription fill rate in detecting nonadherence. Prior studies have also shown a prevalence of nonadherence from 45% to 80% among insured patients with uncontrolled hypertension despite having been prescribed a multi-drug regimen. Previous studies have not assessed adherence to antihypertensive drugs in a safety net population by TDM.

Methods: We performed a cross-sectional study in patients with uncontrolled hypertension in the primary care Internal Medicine and Cardiology Clinics at Parkland Health& Hospital System (PHHS). Patients with BP of 130/80 mmHg, prescribed ≥2 antihypertensive medications, and self-reporting medication adherence were enrolled after informed consent. Plasma samples were obtained for measurement of 44 cardiovascular drugs using liquid chromatography mass spectrometry.

Results: Among 77 patients with uncontrolled hypertension (57% female, 65% Black, 12% Hispanic), 13 (17%) were nonadherent to at least one anti-hypertensive drug by TDM. There was no difference in baseline characteristics between the two groups. The adherent and nonadherent groups had similar systolic (146±13 vs 148±18, p=0.67) and diastolic (83±9 vs 88±10 mmHg, p=0.13) BP. All patients had either medical insurance or some form of prescription financial assistance. 15 patients had prescription financial assistance, while 62 patients had medical insurance. Nonadherence rates for patients on financial assistance programs did not significantly differ from patients with medical insurance (13% vs 18%, p>0.999).

Conclusions: We found a surprisingly low prevalence of anti-hypertensive medication nonadherence in this uncontrolled hypertension population despite many barriers to treatment. Our study suggests a lesser role of medication nonadherence in uncontrolled hypertension in the safety net population.

Abstract MP23: Arterial Depressor Responses Induced By Neuromodulation Of Deep Peroneal Nerve In Spontaneously Hypertensive Rats

Hypertension affects nearly half of the US population but only 43% achieved blood pressure control with medication alone. Medical devices for hypertension include implantable lead electrodes that stimulate the carotid baroreceptors with promising results, albeit with significant adverse complications. To address these limitations, we have proposed the use of deep peroneal nerve stimulation (DPNS), which elicited a depressor response in anesthetized, breathing supported, spontaneously hypertensive rats (SHR). In this study, we further define the electrical stimulation parameters that optimize the DPNS depressor response, and demonstrated that increasing the pulse duration from 0.15 ms to 1ms, of 1.0 mA pulses at 2 Hz for 10 sec, significantly reduced the mean arterial pressure (MAP) by 8±4 mmHg (p<0.005; n=4) in this animal model. DPNS also caused an immediate increase in renal nerve activity (RNA; p< 0.004, n=5), which may represent afferent sensory axons from the kidney, although this possibility needs to be further investigated. In a separate cohort of anesthetized SHR animals, breathing spontaneously, we demonstrated that optimal DPNS stimulation reduced the MAP from 121±3 to 108±4; p=0.02; n=10). To confirm if DPNS is able to evoke a depressor response in fully awake SHR animals, we developed a novel miniaturized wireless microchannel electrode (w-μCE) with a L-shaped microchannel, through which the DPN slides and locks into a recording/stimulation chamber, causing no discomfort to the animal during locomotion. Two weeks after implantation of the w-μCE neural stimulation device, animals were movement-retrained to received wireless DPNS for 10 min daily for 2 weeks. Blood pressure was measured by tail-cuff at baseline, 10 days after device implantation, and 1 and 2-hr 15 days after DPNS. After two weeks of DPNS, the acute neuromodulation treatment reduced the initial systolic BP of 154±20 mmHg to 127±7 and 119±2 mmHg at 1 and 2 hr; respectively (p< 0.001, n=15-19 measurements; n=2 animals). These results provide evidence of the effectiveness and reliability of DPN neuromodulation as a possible treatment for drug-resistant hypertension.

Differential effects of eplerenone versus amlodipine on muscle metaboreflex function in hypertensive humans

Numerous studies have demonstrated that sympathetic nervous system overactivation during exercise in hypertensive rodents and humans is due, in part, to an exaggerated reflex response known as the exercise pressor reflex. Our prior studies have implicated a key role of mineralocorticoid receptor activation in mediating an augmented exercise pressor reflex in spontaneously hypertensive rats, which is mitigated by blockade with eplerenone. However, the effect of eplerenone on exercise pressor reflex has not been assessed in human hypertension. Accordingly, the authors performed a randomized crossover study to compare the effects of eplerenone to another antihypertensive drug from a different class amlodipine on sympathetic nerve activity (SNA) in 14 patients with uncomplicated hypertension. The authors found that amlodipine unexpectedly augmented the increase in SNA during the second minute of isometric handgrip, which persisted into the post‐exercise circulatory arrest period (∆ SNA, from rest of 15 ± 2 vs. 9 ± 2 vs. 10 ± 2 bursts/min, amlodipine vs. baseline vs. eplerenone, respectively, p < .01), suggesting an exaggerated muscle metaboreflex function. Eplerenone did not alter sympathetic responses to exercise or post‐exercise circulatory arrest in the same hypertensive individuals. In conclusions, our studies provide the first direct evidence for a potentially unfavorable potentiation of muscle metaboreflex by amlodipine during isometric handgrip exercise in hypertensive patients whereas eplerenone has no significant effect. Our study may have clinical implications in terms of selection of antihypertensive agents that have the least detrimental effects on sympathetic neural responses to isometric exercise.

Evidence of Reduced Efferent Renal Sympathetic Innervation After Chemical Renal Denervation in Humans

BACKGROUND

Renal denervation (RDN) is effective at lowering blood pressure. However, it is unknown if ablative procedures elicit sympathetic denervation of the kidneys in humans. The aim of this investigation was to assess sympathetic innervation of the renal cortex following perivascular chemical RDN, which may be particularly effective at ablating perivascular efferent and afferent nerves.

METHODS

Seven hypertensive patients (4F:3M; 50-65 years) completed PET-CT sympathetic neuroimaging of the renal cortex using 11C-methylreboxetine (11C-MRB, norepinephrine transporter ligand) and 6-[18F]-fluorodopamine (18F-FDA; substrate for the cell membrane norepinephrine transporter) before and 8 weeks after chemical RDN (Peregrine System Infusion Catheter, Ablative Solutions; n = 4; 2F:2M) or control renal angiography (n = 3; 2F:1M). Patients completed physiological phenotyping including 24-hour ambulatory blood pressure, hemodynamics, muscle sympathetic nerve activity, and 24-hour urine collection.

RESULTS

RDN decreased 11C-MRB-derived radioactivity by ~30% (Δ  11C-MRB/chamber: -0.95 a.u. confidence interval (CI): -1.36 to -0.54, P = 0.0002), indicative of efferent RDN. In contrast, 18F-FDA-derived radioactivity increased (Δ  18F-FDA/chamber: 2.72 a.u. CI: 0.73-4.71, P = 0.009), consistent with reduced vesicular turnover. Controls showed no change in either marker. Ambulatory systolic pressure decreased in 3 of 4 patients (-9 mm Hg CI: -27 to 9, P = 0.058), and central systolic pressure decreased in all patients (-23 mm Hg CI: -51 to 5, P = 0.095).

CONCLUSIONS

These results are the first to show efferent sympathetic denervation of the renal cortex following RDN in humans. Further studies of mechanisms underlying variable blood pressure lowering in the setting of documented RDN may provide insights into inconsistencies in clinical trial outcomes.

CLINICAL TRIALS REGISTRATION

Trial Number NCT03465917.

The Impact of Insulin Resistance on Cardiovascular Control During Exercise in Diabetes

Patients with diabetes display heightened blood pressure response to exercise, but the underlying mechanism remains to be elucidated. There is no direct evidence that insulin resistance (hyperinsulinemia or hyperglycemia) impacts neural cardiovascular control during exercise. We propose a novel paradigm in which hyperinsulinemia or hyperglycemia significantly influences neural regulatory pathways controlling the circulation during exercise in diabetes.