Sympathetic transduction in humans: recent advances and methodological considerations.

Ever since their origin more than one half-century ago, microneurographic recordings of sympathetic nerve activity have significantly advanced our understanding of the generation and regulation of central sympathetic outflow in human health and disease. For example, it is now appreciated that a myriad of disease states exhibit chronic sympathetic overactivity, a significant predictor of cardiovascular morbidity and mortality. Although microneurographic recordings allow for the direct quantification of sympathetic outflow, they alone do not provide information with respect to the ensuing sympathetically mediated vasoconstriction and blood pressure (BP) response. Therefore, the study of vascular and/or BP responses to sympathetic outflow (i.e., sympathetic transduction) has now emerged as an area of growing interest within the field of neural cardiovascular control in human health and disease. To date, studies have primarily examined sympathetic transduction under two distinct paradigms: when reflexively evoking sympatho-excitation through the induction of a laboratory stressor (i.e., sympathetic transduction during stress) and/or following spontaneous bursts of sympathetic outflow occurring under resting conditions (i.e., sympathetic transduction at rest). The purpose of this brief review is to highlight how our physiological understanding of sympathetic transduction has been advanced by these studies and to evaluate the primary analytical techniques developed to study sympathetic transduction in humans. We also discuss the framework by which the assessment of sympathetic transduction during stress reflects a fundamentally different process relative to sympathetic transduction at rest and why findings from investigations using these different techniques should be interpreted as such and not necessarily be considered one and the same.

Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise.

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.

Augmented resting beat-to-beat blood pressure variability in young, healthy, non-Hispanic black men.

NEW FINDINGS: What is the central question of this study? The prevalence of hypertension in black individuals exceeds that in other racial groups. Despite this well-known heightened risk, the underlying contributory factors remain incompletely understood. We hypothesized that young black men would exhibit augmented beat-to-beat blood pressure variability compared with white men and that black men would exhibit augmented total peripheral resistance variability. What is the main finding and its importance? We demonstrate that young, healthy black men exhibit greater resting beat-to-beat blood pressure variability compared with their white counterparts, which is accompanied by greater variability in total peripheral resistance. These swings in blood pressure over time might contribute to the enhanced cardiovascular risk profile in black individuals. ABSTRACT: The prevalence of hypertension in black (BL) individuals exceeds that in other racial groups. Recently, resting beat-to-beat blood pressure (BP) variability has been shown to predict cardiovascular risk and detect target organ damage better than ambulatory BP monitoring. Given the heightened risk in BL individuals, we hypothesized young BL men would exhibit augmented beat-to-beat BP variability compared with white (WH) men. Furthermore, given studies reporting reduced vasodilatation and augmented vasoconstriction in BL individuals, we hypothesized that BL men would exhibit augmented variability in total peripheral resistance (TPR). In 45 normotensive men (24 BL), beat-to-beat BP (Finometer) was measured during 10-20 min of quiet rest. Cardiac output and TPR were estimated (Modelflow method). Despite similar resting BP, BL men exhibited greater BP standard deviation (e.g. systolic BP SD; BL, 7.1 ± 2.2 mmHg; WH, 5.4 ± 1.5 mmHg; P = 0.006) compared with WH men, which was accompanied by a greater TPR SD (P = 0.003), but not cardiac output SD (P = 0.390). Other traditional measures of variability provided similar results. Histogram analysis indicated that BL men exhibited a greater percentage of cardiac cycles with BPs higher (> +10 mmHg higher) and lower (< -8 mmHg lower) than mean systolic BP compared with WH men (interaction, P < 0.001), which was accompanied by a greater percentage of cardiac cycles with high/low TPR (P < 0.001). In a subset of subjects (n = 30), reduced sympathetic baroreflex sensitivity was associated with augmented BP variability (r = -0.638, P < 0.001), whereas cardiac baroreflex sensitivity had no relationship (P = 0.447). Herein, we document an augmented beat-to-beat BP variability in young BL men, which coincided with fluctuations in vascular resistance and reduced sympathetic BRS.

Racial disparities in cardiovascular disease risk: mechanisms of vascular dysfunction.

Cardiovascular disease (CVD) accounts for a third of all deaths in the United States making it the leading cause of morbidity and mortality. Although CVD affects individuals of all races/ethnicities, the prevalence of CVD is highest in non-Hispanic black (BL) individuals relative to other populations. The mechanism(s) responsible for elevated CVD risk in the BL population remains incompletely understood. However, impaired vascular vasodilator capacity and exaggerated vascular vasoconstrictor responsiveness are likely contributing factors, both of which are present even in young, otherwise healthy BL individuals. Within this review, we highlight some historical and recent data, collected from our laboratories, of impaired vascular function, in terms of reduced vasodilator capacity and heightened vasoconstrictor responsiveness, in the peripheral and cerebral circulations in BL individuals. We provide data that such impairments may be related to elevated oxidative stress and subsequent reduction in nitric oxide bioavailability. In addition, divergent mechanisms of impaired vasodilatory capacity between BL men and women are discussed. Finally, we propose several directions where future research is needed to fill in knowledge gaps, which will allow for better understanding of the mechanisms contributing to impaired vascular function in this population. Ultimately, this information will allow for better lifestyle and therapeutic approaches to be implemented in an effort to minimize the increased CVD burden in the BL population.

Attenuated forearm vascular conductance responses to rhythmic handgrip in young African-American compared with Caucasian-American men.

Previous studies have demonstrated that African-American (AA) individuals have heightened vasoconstrictor and reduced vasodilator responses under resting conditions compared with Caucasian-American (CA) individuals. However, potential differences in vascular responses to exercise remain unclear. Therefore, we tested the hypothesis that, compared with CA subjects, AA subjects would present an attenuated increase in forearm vascular conductance (FVC) during rhythmic handgrip exercise. Forearm blood flow (FBF; duplex Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography) were measured in healthy young CA ( n = 10) and AA ( n = 10) men during six trials of rhythmic handgrip performed at workloads of 4, 8, 12, 16, 20, and 24 kg. FVC (calculated as FBF/MAP), FBF, and MAP were similar between groups at rest (FVC: 63 ± 7 ml·min-1·100 mmHg-1 in CA subjects vs. 62 ± 7 ml·min-1·100 mmHg-1 in AA subjects, P = 0.862). There was an intensity-dependent increase in FVC during exercise in both groups; however, AA subjects presented lower FVC (interaction P < 0.001) at 8-, 12-, 16-, 20-, and 24-kg workloads (e.g., 24 kg: 324 ± 20 ml·min-1·100 mmHg-1 in CA subjects vs. 241 ± 21 ml·min-1·100 mmHg-1 in AA subjects, P < 0.001). FBF responses to exercise were also lower in AA subjects (interaction P < 0.001), whereas MAP responses did not differ between groups (e.g., ∆MAP at 24 kg: +19 ± 2 mmHg in CA subjects vs. +19 ± 2 mmHg in AA subjects, interaction P = 0.950). These findings indicate lower hyperemic responses to rhythmic handgrip exercise in AA men compared with CA men. NEW & NOTEWORTHY It is known that African-American individuals have heightened vasoconstriction and reduced vasodilation under resting conditions compared with Caucasian-American individuals. Here, we identified that the hyperemic response to moderate and high-intensity rhythmic handgrip exercise was lower in healthy young African-American men.

Relationship-focused vs. Structural Activities in Medical Home Measurement in Pediatrics.

Objectives The Family-Centered Medical Home (FCMH) has become a model of effective and efficient primary care. However, efforts to measure the FCMH may ignore its complexity. We sought to determine whether U.S. primary care pediatricians view structure-focused and relationship-focused practice activities of the FCMH as distinct constructs and how these constructs are associated with practice functions. Methods We analyzed data from the 2012 American Academy of Pediatrics Periodic Survey of Fellows #79 (n = 572) addressing opinions and practice activities related to the FCMH. Through a modified Delphi expert process, we selected items believed to be primarily structure-focused and items that were relationship-focused. Confirmatory factor analysis was used to test whether these constructs were distinct. Separate structural equation models assessed whether structure-focused and relationship-focused activities predicted three broader survey items: (1) interest in FCMH; (2) application for FCMH recognition; and (3) whether a team meets to discuss FCMH improvements. Results The initial two-factor model did not fit well, but improved with movement of two items from the structure to the relationship-focused group. The two factors correlated at r = 0.70. Respondents with increased relationship-focused activities had statistically higher odds of having medium/high interest in FCMH, and having a team meet to discuss FCMH improvements. Respondents with increased structure-focused activities also had higher odds of having team meetings to discuss FCMH improvements, but lower odds of applying for FCMH recognition. Conclusions for Practice The FCMH is multi-dimensional, with relationship- and structure-focused activities differentially linked to pediatrician reports of broader FCMH functions.

Impaired carotid baroreflex control of arterial blood pressure in multiple sclerosis.

Multiple sclerosis (MS), a progressive neurological disease, can lead to impairments in the autonomic control of cardiovascular function. We tested the hypothesis that individuals with relapsing-remitting MS (n = 10; 7 females, 3 males; 13 ± 4 yr from diagnosis) exhibit impaired carotid baroreflex control of blood pressure and heart rate compared with sex, age, and body weight-matched healthy individuals (CON: n = 10; 7 females, 3 males). At rest, 5-s trials of neck pressure (NP; +40 Torr) and neck suction (NS; -60 Torr) were applied to simulate carotid hypotension and hypertension, respectively, while mean arterial pressure (MAP; finger photoplethysmography), heart rate (HR), cardiac output (CO; Modelflow), and total vascular conductance (TVC) were continuously measured. In response to NP, there was a blunted increase in peak MAP responses (MS: 5 ± 2 mmHg) in individuals with MS compared with healthy controls (CON: 9 ± 3 mmHg; P = 0.005), whereas peak HR responses were not different between groups. At the peak MAP response to NP, individuals with MS demonstrated an attenuated decrease in TVC (MS, -10 ± 4% baseline vs. CON, -15 ± 4% baseline, P = 0.012), whereas changes in CO were similar between groups. Following NS, all cardiovascular responses (i.e., nadir MAP and HR and percent changes in CO and TVC) were not different between MS and CON groups. These data suggest that individuals with MS have impaired carotid baroreflex control of blood pressure via a blunted vascular conductance response resulting in a diminished ability to increase MAP in response to a hypotensive challenge.

Carotid baroreflex control of heart rate is enhanced, while control of mean arterial pressure is preserved during whole body heat stress in young healthy men.

Whole body heat stress (WBH) results in numerous cardiovascular alterations that ultimately reduce orthostatic tolerance. While impaired carotid baroreflex (CBR) function during WBH has been reported as a potential reason for this decrement, study design considerations may limit interpretation of previous findings. We sought to test the hypothesis that CBR function is unaltered during WBH. CBR function was assessed in 10 healthy male subjects (age: 26 ± 3; height: 185 ± 7 cm; weight: 82 ± 10 kg; BMI: 24 ± 3 kg/m2; means ± SD) using 5-s trials of neck pressure (+45, +30, and +15 Torr) and neck suction (-20, -40, -60, and -80 Torr) during normothermia (NT) and passive WBH (Δ core temp ∼1°C). Analyses of stimulus response curves (four-parameter logistic model) for CBR control of heart rate (CBR-HR) and mean arterial pressure (CBR-MAP), as well as separate two-way ANOVA of the hypotensive and hypertensive stimuli (factor 1: thermal condition, factor 2: chamber pressure), were performed. For CBR-HR, maximal gain was increased during WBH (-0.73 ± 0.11) compared with NT (-0.39 ± 0.04, mean ± SE, P = 0.03). In addition, the CBR-HR responding range was increased during WBH (33 ± 5) compared with NT (19 ± 2 bpm, P = 0.03). Separate analysis of hypertensive stimulation revealed enhanced HR responses during WBH at -40, -60, and -80 Torr (condition × chamber pressure interaction, P = 0.049) compared with NT. For CBR-MAP, both logistic analysis and separate two-way ANOVA revealed no differences during WBH. Therefore, in response to passive WBH, CBR control of heart rate (enhanced) and arterial pressure (no change) is well preserved.

Elevated peripheral blood mononuclear cell-derived superoxide production in healthy young black men.

Several studies have demonstrated that blacks exhibit elevations in systemic oxidative stress. However, the source(s) and mechanism(s) contributing to the elevation in oxidative stress remain unclear. Given that peripheral blood mononuclear cells (PBMCs) can be a major source of NADPH oxidase-derived superoxide production, we tested the hypothesis that young black men demonstrate greater superoxide production and NADPH oxidase expression in PBMCs compared with whites. PBMCs were freshly isolated from whole blood in young normotensive black (n = 18) and white (n = 16) men. Intracellular superoxide production in PBMCs was measured using dihydroethidium fluorescence, protein expression of NADPH oxidase subunits, gp91(phox) (membranous) and p47(phox) (cytosolic) in PBMCs were assessed using Western blot analysis, and plasma protein carbonyls were measured as a marker of systemic oxidative stress. Black men showed elevated intracellular superoxide production (4.3 ± 0.5 vs. 2.0 ± 0.6 relative fluorescence units; black men vs. white men, P < 0.05), increased protein expression for gp91(phox) and p47(phox) (e.g., p47(phox): 1.1 ± 0.2, black men vs. 0.4 ± 0.1, white men, P < 0.05) in PBMCs and higher circulating protein carbonyl levels (22 ± 4 vs. 14 ± 2 nmol/ml; black men vs. white men, P < 0.05). Interestingly, a positive family history of hypertension in black men did not further enhance PBMC-derived intracellular superoxide production or NADPH oxidase subunit protein expression. These findings indicate that black men exhibit greater resting PBMC-derived superoxide production and an upregulation of the NADPH oxidase pathway with a possible contribution to increases in systemic oxidative stress.

Combined facial heating and inhalation of hot air do not alter thermoeffector responses in humans.

The influence of thermoreceptors in human facial skin on thermoeffector responses is equivocal; furthermore, the presence of thermoreceptors in the respiratory tract and their involvement in thermal homeostasis has not been elucidated. This study tested the hypothesis that hot air directed on the face and inhaled during whole body passive heat stress elicits an earlier onset and greater sensitivity of cutaneous vasodilation and sweating than that directed on an equal skin surface area away from the face. Six men and two women completed two trials separated by ∼1 wk. Participants were passively heated (water-perfused suit; core temperature increase ∼0.9°C) while hot air was directed on either the face or on the lower leg (counterbalanced). Skin blood flux (laser-Doppler flowmetry) and local sweat rate (capacitance hygrometry) were measured at the chest and one forearm. During hot-air heating, local temperatures of the cheek and leg were 38.4 ± 0.8°C and 38.8 ± 0.6°C, respectively (P = 0.18). Breathing hot air combined with facial heating did not affect mean body temperature onsets (P = 0.97 and 0.27 for arm and chest sites, respectively) or slopes of cutaneous vasodilation (P = 0.49 and 0.43 for arm and chest sites, respectively), or the onsets (P = 0.89 and 0.94 for arm and chest sites, respectively), or slopes of sweating (P = 0.48 and 0.65 for arm and chest sites, respectively). Based on these findings, respiratory tract thermoreceptors, if present in humans, and selective facial skin heating do not modulate thermoeffector responses during passive heat stress.

Comparative outcomes after treatment of peri-implant, periprosthetic, and interprosthetic femur fractures: which factors increase mortality risk?

Objectives: To compare mortality rates between patients treated surgically for periprosthetic fractures (PPF) after total hip arthroplasty (THA), total knee arthroplasty (TKA), peri-implant (PI), and interprosthetic (IP) fractures while identifying risk factors associated with mortality following PPF. Design: Retrospective. Setting: Single, Level II Trauma Center. Patients/Participants: A retrospective review was conducted of 129 consecutive patients treated surgically for fractures around a pre-existing prosthesis or implant from 2013 to 2020. Patients were separated into 4 comparison groups: THA, TKA, PI, and IP fractures. Intervention: Revision implant or arthroplasty, open reduction and internal fixation (ORIF), intramedullary nailing (IMN), percutaneous screws, or a combination of techniques. Main Outcome Measurements: Primary outcome measures include mortality rates of different types of PPF, PI, and IP fractures at 1-month, 3-month, 6-month, 1-year, and 2-year postoperative. We analyzed risk factors associated with mortality aimed to determine whether treatment type affects mortality. Results: One hundred twenty-nine patients were included for final analysis. Average follow-up was similar between all groups. The overall 1-year mortality rate was 1 month (5%), 3 months (12%), 6 months (13%), 1 year (15%), and 2 years (22%). There were no differences in mortality rates between each group at 30 days, 90 days, 6 months, 1 year, and 2 years (P-value = 0.86). A Kaplan-Meier survival curve demonstrated no difference in survivorship up to 2 years. Older than 65 years, history of hypothyroidism and dementia, and discharge to a skilled nursing facility (SNF) led to increased mortality. There was no survival benefit in treating patients with PPFs with either revision, ORIF, IMN, or a combination of techniques. Conclusion: The overall mortality rates observed were 1 month (5%), 3 months (12%), 6 months (13%), 1 year (15%), and 2 years (22%), and no differences were found between each group at all follow-up time points. Patients aged 65 and older with a history of hypothyroidism and/or dementia discharged to an SNF are at increased risk for mortality. From a mortality perspective, surgeons should not hesitate to choose the surgical treatment they feel most comfortable performing. Level of Evidence: Level III.

Does a delay to surgery for preoperative echocardiogram affect outcomes in patients with hip fracture?

Introduction: Delay to surgery >24 hours has been shown to correlate with mortality rates in patients with hip fracture when left untreated. Many of these patients have multiple comorbidities, including aortic stenosis (AS), and undergo workup for operative clearance, which may delay time to surgery. The purpose of this study was to examine whether preoperative echocardiogram workup affects time to surgery, complications, and mortality after operative fixation for hip fracture. Methods: Our institutional hip fracture registry was retrospectively reviewed for inclusion over a 3-year period. Patients who had a preoperative echocardiogram (yECHO) for operative clearance were compared with those who did not (nECHO). Demographic data, time to surgery, overall complication rate, and mortality at 30 days, 90 days, and 1 year were collected. Results: Two cohorts consisted of 136 yECHO patients (45.8%) and 161 nECHO patients (54.2%). Thirty-two yECHO patients (23.5%) had AS. Patients in the yECHO cohort were more likely to have a complication for any cause compared with nECHO patients (25.7% vs. 10.6%, P = 0.01) and have a higher mortality rate at 1 year (38.9% vs. 17.4%, P = 0.001). There was no association found between AS and all-cause complication (P = 0.54) or 30-day (P = 0.13) or 90-day mortality rates (P = 0.79). However, patients with AS had a significantly higher mortality rate at 1 year (45.8% vs. 25.1%, P = 0.03). Conclusion: This study reinforces the benefits of ensuring less than a 24-hour time to surgery in the setting of a hip fracture and identifies an area of preoperative management that can be further optimized to prevent unnecessary prolongation in time to surgery. Patients with known aortic stenosis are not associated with increased 30-day or 90-day mortality or all-cause complications. Surgical delays in the yECHO cohort were attributed to preoperative medical assessments, including echocardiograms and the management of comorbidities. Therefore, the selective utilization of preoperative echocardiograms is needed and should be reserved to ensure they have a definitive role in guiding the perioperative care of patients with hip fracture. Level of Evidence: III.

Using the Equatorial Talar Line as a Radiographic Predictor of Sanders Type 3 and 4 Calcaneus Fractures and Lateral Wall Blowout.

OBJECTIVE: To assess the equatorial talar line (ETL) as a sensitive radiographic parameter to predict Sanders type III and IV fractures and the presence of lateral wall blowout. METHODS: Reliability of the ETL was assessed using the intraclass correlation coefficient (ICC) and receiver operating curve (ROC) to predict sensitivity. Using lateral ankle radiographs, raters determined whether the calcaneal tuberosity was "above" (predicting Sanders type I or II) or "below" (predicting Sanders type III or IV and lateral wall blowout). RESULTS: In determining the "above" or "below" location of the ETL, the calculated ICC was 1.0 for each session. As a predictor of Sanders fracture classification type, the calculated ICC was 0.93 for the first session and 0.89 for the second session for an overall ICC of 0.91. As a predictor of Sanders fracture type, ROC analysis yielded an overall sensitivity of 0.82. As a predictor of lateral wall blowout, ROC analysis yielded an overall sensitivity of 0.81. CONCLUSION: The ETL is a reproducible radiographic parameter that can be reliably used to crudely predict between Sanders type I or II (ETL is "above") and Sanders type III or IV (ETL is "below") calcaneus fractures as well as the presence of lateral wall blowout.

Child Advocacy in Action: If Not You, Who? If Not now, When?

The notion that the physician has a responsibility to both the patient in their care and the community in which they reside has been a source of inspiration and tension within the profession for centuries. The profession of Pediatrics has uniquely incorporated advocacy into its training programs and will likely continue to incorporate advocacy into its professional standards for the foreseeable future. In this article, we review the history of advocacy within the profession, outline the skills needs for successful child health advocacy and offer examples of how advocacy combined with pediatric practice has improved the lives of children.

Comparison of Outcomes After Reverse Total Shoulder Arthroplasty in Patients With Proximal Humerus Fractures Versus Rotator Cuff Arthropathy.

INTRODUCTION: Indications for reverse total shoulder arthroplasty (rTSA) has expanded to encompass complex proximal humerus fractures (PHFs) in recent years. The purpose of this study was to report and assess whether PHF patients treated with rTSA could achieve similar functional outcomes and short-term survivorship to patients who underwent rTSA for rotator cuff arthropathy (RTCA). METHODS: All consecutive patients with a preoperative diagnosis of PHF or RTCA, 18 years or older, treated with rTSA at a single academic institution between 2018 and 2020 with a minimum 2-year follow-up were retrospectively reviewed. Primary outcomes were survivorship defined as revision surgery or implant failure analyzed using the Kaplan-Meier survival curve, and functional outcomes, which included Quick Disabilities of the Arm, Shoulder, and Hand, and range of motion (ROM) were compared at multiple follow-up time points up to 2 years. Secondary outcomes were patient demographics, comorbidities, surgical data, length of hospital stay, and discharge disposition. RESULTS: A total of 48 patients were included: 21 patients (44%) were diagnosed with PHF and 27 patients (56%) had RTCA. The Kaplan-Meier survival rate estimates at 3 years were 90.5% in the PHF group and 85.2% in the RTCA group. No differences in revision surgery rates between the two groups (P = 0.68) or survivorship (P = 0.63) were found. ROM was significantly lower at subsequent follow-up time points in multiple planes (P < 0.05). A greater proportion of patients in the PHF group received cement for humeral implant fixation compared with the RTCA group (48% versus 7%, P = 0.002). The mean length of hospital stay was longer in PHF patients compared with RTCA patients (2.9 ± 3.8 days versus 1.6 ± 1.8 days, P = 0.13), and a significantly lower proportion of PHF patients were discharged home (67% versus 96%, P = 0.015). CONCLUSION: The rTSA implant survivorship at 3 years for both PHF and RTCA patients show comparable results. At the 2-year follow-up, RTCA patients treated with rTSA were found to have better ROM compared with PHF patients.

Dual regulation of miR-375 and CREM genes in pancreatic beta cells.

MicroRNA-375 (miR-375) is upregulated in the islets of some diabetics and is correlated with poor outcome. Previous work in our laboratory showed that cyclic adenosine monophosphate (cAMP) reduces miR-375 expression and could provide a way to restore normal miR-375 levels, however the transcription repression mechanism is unknown. Using a chromatin immunoprecipitation assay we show that cAMP response element modulator (CREM) binds to the miR-375 promoter 3-fold above background and we find that CREM represses transcription from the miR-375 promoter 1.8-fold. While investigating miR-375 target genes we discovered that several microRNA:mRNA target prediction algorithms listed human CREM as a target gene of miR-375. The predicted binding site is conserved in primates but not in other species. We found that indeed miR-375 binds to the predicted site on human CREM and represses translation of a green fluorescent protein reporter gene by 30%. These findings suggest a primate-specific double-negative feedback loop, a mechanism that would keep these important ß-cell regulators in check.