Penile keloid formation post-circumcision: A case series and review of literature

The formation of penile keloid after circumcision is an uncommon complication. Herein, we report two pediatric cases of large circumferential keloids that developed post-circumcision and were successfully treated by surgical excision and intralesional triamcinolone injections. In addition, we provide a comprehensive review of the reported cases of penile keloids that developed after circumcision in the literature to highlight the various presentations, treatment options, and outcomes for this condition.

Infantile Hemangiomas and Vascular Anomalies

Vascular anomalies represent a diverse group of disorders of abnormal vascular development or proliferation. Vascular anomalies are classified as vascular tumors and vascular malformations. Significant advances have been made in the understanding of the pathogenesis, natural history, and genetics of vascular anomalies, allowing for improvements in management including targeted molecular therapies. Infantile hemangiomas are the most common vascular tumor of childhood and follow a distinct natural history of proliferation and involution. Although benign, infantile hemangiomas can be associated with important complications. The use of beta-blockers has revolutionized the management of infantile hemangiomas. Other vascular tumors include pyogenic granulomas, congenital hemangiomas, and kaposiform hemangioendotheliomas, among others. Vascular malformations are categorized based on the type of involved vessel, including capillary malformations, venous malformations, lymphatic malformations, arteriovenous malformations, and mixed vascular malformations. Expert multidisciplinary management of vascular anomalies is critical to optimize outcomes in these patients. [Pediatr Ann. 2024;53(4):e129-e137.].

Clinical characteristics of infantile hemangiomas with aggressive, persistent, and destructive ulceration

BACKGROUND/OBJECTIVES

Ulceration is a common complication of infantile hemangioma (IH). Severe, persistent ulceration occurs in a minority of patients. This study aims to characterize the clinical features of IH with aggressive ulceration (AU).

METHODS

Multicenter retrospective study of clinical features of IH with AU.

RESULTS

Thirty-five patients with AU were identified and included in the study. The majority of AU occurred in segmental IH (23/35, 65%). Segmental IH with AU were large (≥10 cm2 ; 16/23, 69%, p < .001) with a thin (<3 mm) superficial component (16/23, 69%, p < .001). Localized IH with AU had a thick (>3 mm) superficial component (11/12, 92%, p < .001). All diaper area IH with AU (9/35) were segmental with thin superficial component (100%, p = .02). IH with AU in the head/neck (10/35) were more commonly localized (67%) and mixed (62.5%), while segmental, thick superficial morphology was more common on trunk (9/35) and upper extremities (7/35).

CONCLUSIONS

IH resulting in AU differ in clinical features by anatomic site. Those in the diaper area are nearly always segmental with thin superficial component, whereas other sites tend to be localized, mixed, with thick superficial component. These distinct phenotypes may prove useful in the clinical setting for physicians to identify patterns of IH ulceration with increased risk of aggressive, persistent ulceration.

Characteristics and complications of anogenital infantile hemangiomas: A multicenter retrospective analysis

BACKGROUND

Infantile hemangiomas (IHs) of the anogenital region remain poorly characterized.

OBJECTIVE

To examine the distribution, ulceration rate, and associated congenital anomalies of anogenital IHs.

METHODS

Retrospective study at 8 tertiary referral centers.

RESULTS

A total of 435 infants with an IH of the anogenital region were enrolled (of which, 319 [73%] were girls). Congenital anomalies were present in 6.4% (n = 28) of infants with an anogenital IH. Segmental or partial segmental anogenital IHs ulcerated in 72% (n = 99 of 138) of infants, whereas 45% (n = 133 of 297) of focal anogenital IHs experienced ulceration (P < .001). In a multivariable logistic regression analysis, segmental or partial segmental morphology (adjusted odds ratio [aOR], 2.70; 95% CI, 1.60-4.64), mixed type (aOR, 3.44; 95% CI, 2.01-6.07), and perianal (aOR, 3.01; 95% CI, 1.53-6.12) and buttocks location (aOR, 2.08; 95% CI, 1.17-3.76) had increased odds of ulceration. Segmental or partial segmental IHs of the genitalia were confined to distinct anatomic territories and were predominantly distributed unilaterally, with a linear demarcation at the perineal raphe.

LIMITATIONS

Possible selection bias, given recruitment at tertiary referral centers.

CONCLUSION

This study improves our understanding of high-risk features of anogenital IHs and demonstrates that genital segmental or partial segmental IHs develop within distinct anatomic territories.

KAT6A::EP300 fusion in congenital myeloid sarcoma: Yet another novel molecular marker indicating spontaneous remission?: A case report

RATIONALE

Acute myeloid leukemia (AML)/myeloid sarcoma (MS) is risk-stratified based on cytogenetics. Although most congenital AML/MS have a dismal prognosis, certain genetic variants such as t (8, 16) [KAT6A::cAMP response element-binding protein (CREB) - binding protein fusion] and more recently t (8, 22) [KAT6A::EP300 fusion] have shown spontaneous remissions. KAT6A located on chromosome 8p11 encodes KAT6A protein, a histone/lysine acetyltransferase enzyme. Numerous partner genes associated with KAT6A include cAMP response element-binding protein (CREB) - binding protein (16p13), EP300 (22q13), LEUTX (9q13), NCOA2, NCOA3, and ASXL2.

PATIENT CONCERNS

In this article, we describe an otherwise healthy infant who presented with skin nodules on the face and scalp without any systemic or CNS involvement. A biopsy of the cutaneous lesion was consistent with congenital MS.

DIAGNOSES

Through molecular testing, we found that our patient had the KAT6A::EP300 mutation. This is one of the rare recurrent cytogenetic abnormalities that are linked to congenital AML.

INTERVENTION

Our patient underwent spontaneous remission with watchful waiting.

OUTCOME

Our patient has remained in spontaneous remission for 24 months.

LESSONS

Even though the KAT6A::EP300 mutation in adults is a poor prognostic marker, a similar mutation in congenital AML has a higher likelihood of spontaneous remission. Hence, conservative management might be an initial management strategy for clinically stable patients.

Multicenter retrospective review of pulsed dye laser in nonulcerated infantile hemangioma

BACKGROUND/OBJECTIVES

We sought to describe the experience among members of the Hemangioma Investigator Group with pulsed dye laser (PDL) in the treatment of nonulcerated infantile hemangioma (IH) in pediatric patients in the pre- and post-beta-blocker era.

METHODS

A multicenter retrospective cohort study was conducted in patients with nonulcerated IH treated with laser therapy. Patient demographics, IH characteristics, indications for/timing of laser therapy, as well as laser parameters were collected. Responses to laser therapy were evaluated using a visual analog scale (VAS).

RESULTS

One hundred and seventeen patients with IH were treated with PDL. 18/117 (15.4%) had early intervention (defined as <12 months of life), and 99/117 (84.6%) had late intervention (≥12 months of life). In the late intervention group, 73.7% (73/99) had additional medical management of their IH. The mean age at PDL initiation for the late intervention group was 46.7 ± 35.3 months of life (range 12-172 months) with total number of treatments to maximal clearing of 4.2 ± 2.8 (range 1-17). Those who received propranolol prior to PDL received fewer sessions (1.1 fewer sessions, approaching significance [p = .056]).     On the VAS, there was a mean 85% overall improvement compared to baseline (range 18%-100%), with most improvement noted in erythema and/or telangiectasias. The incidence of adverse effects was 6/99 (6.1%).

CONCLUSIONS

PDL is a useful tool in the treatment of IH, with notable improvement of telangiectasia and erythema and low risk of complications.   PDL is often introduced after the maximal proliferative phase.

The co-occurrence of segmental vitiligo and linear morphea in a pediatric patient and a review of the literature

Linear morphea and segmental vitiligo are both autoimmune diseases that are observed in the pediatric population, with rare reports of their co-existence. We describe a case of linear morphea and segmental vitiligo with an overlapping distribution in a pediatric patient and review the literature. Including our own case, we summarize 10 cases of co-occurring segmental vitiligo and morphea in pediatric patients; most of these lesions follow a blaschkolinear distribution, and none of the patients had autoimmune thyroid disease. Although uncommon, the coexistence of segmental vitiligo and linear morphea within lines of Blaschko can occur, and this case suggests that linear morphea and segmental vitiligo may be disorders related to genetic mosaicism.

Delayed medical care due to transportation barriers among US children with atopic dermatitis

Our objective was to examine the prevalence and predictors of delayed medical care due to transportation barriers among children with atopic dermatitis (AD) living in the United States (US). We analyzed data from the 1998-2018 National Health Interview Survey, a nationally representative survey of US households. In 2018, transport-delayed care was reported for 3.4% of US children with AD, representing approximately 279,000 children annually given the National Health Interview Survey's weighted survey design, and was more common among patients of lower socioeconomic status. Targeted interventions aimed at reducing transportation barriers to healthcare among at-risk AD patients may reduce health disparities related to AD.

Toxic epidermal necrolysis-like acute graft-versus-host disease in pediatric bone marrow transplant patients: Case series and review of the literature

BACKGROUND/OBJECTIVES

Complications of hematopoietic stem cell transplant (HSCT) include acute graft-versus-host disease (aGVHD). Severe cutaneous aGVHD can present with generalized erythroderma, desquamation, and bullae which can mimic toxic epidermal necrolysis (TEN). TEN occurs in response to a culprit medication. Transplant patients are often on many medications, making it difficult to distinguish between the two conditions. Given that TEN-like aGVHD is rare, we describe a case series of pediatric patients and review the literature.

METHODS

This is a multi-institutional case series of children who developed TEN-like aGVHD following bone marrow transplantation. Demographic, clinical, and treatment information was collected.

RESULTS

Ten patients were identified. Median age at transplantation was 8.5 years (range 0.12-17 years). Median time from transplant to first skin symptoms was 35 days (range 6-110 days) and to first TEN-like symptoms was 40 days (range 16-116 days). 7/10 had other organ GVHD involvement. All patients were on concurrent medications at time of first skin symptoms including immunosuppression for GVHD prophylaxis, infection prophylaxis or treatment, and pain medication. Treatments for TEN-like aGVHD included immunosuppression.

CONCLUSIONS

We observe that patients with > or equal to 50% BSA involvement of their skin with TEN-like aGVHD, extracutaneous GVHD, and lack of reepithelization tend to have poor outcomes. Given the rarity of this condition, multidisciplinary care of these patients is important for accurate and timely diagnosis and treatment.

Successful use of telemedicine for evaluation of infantile hemangiomas during the early COVID-19 pandemic: A cross-sectional study

BACKGROUND/OBJECTIVES

The COVID-19 pandemic prompted a rapid expansion in the use of telemedicine. This study aimed to assess the experiences of hemangioma specialists utilizing telemedicine during the COVID-19 pandemic to evaluate and manage infantile hemangiomas (IH), including perceived effectiveness of different modalities and barriers to care delivery.

METHODS

Multicenter cross-sectional study asking providers to describe their experiences using telemedicine for initial evaluation of IH from March to September 2020.

RESULTS

The study included 281 patients from 15 medical centers internationally. Median time from referral to evaluation was 17 days. Median physician confidence in performing evaluations via telemedicine was 95.0 (IQR 90.0-100.0). Most evaluations were performed via video communication with photographs or audio communication with photographs; when not initially available, photographs were requested in 51.4%. Providers preferred follow-up modalities that included photographs.

CONCLUSIONS

Physicians with extensive expertise in managing IH are confident in their abilities to assess and manage IH via telemedicine including initiating treatment in patients without risk factors for beta-blocker therapy. There was a preference for hybrid modalities that included photographs. The data suggest that telemedicine can be effective for managing IH and may decrease wait times and improve specialist reach to underserved areas.

Solitary cutaneous infantile myofibroma as a hallmark of myofibromatosis: Two cases and review of the literature

Infantile myofibroma (IM) commonly presents as a benign cutaneous fibrous tumor in infancy. Although the majority of solitary IM regress without any morbidity, some cases have underlying bone or visceral involvement that can lead to both morbidity and mortality. In this report with review of the literature, we present two cases of solitary cutaneous IM with internal involvement and discuss screening cases of solitary IM with full body imaging.

Skin and Mucosal Manifestations in NEMO Syndrome: A Case Series and Literature Review

OBJECTIVES

To characterize the skin and mucosal findings of NEMO syndrome.

METHODS

Retrospective review of clinical characteristics from a cohort of two families with mutations in IKBKG (the NEMO-encoding gene). A literature review identified 86 studies describing 192 patients with IKBKG mutations whose data were also included.

SETTING

Single center with literature review.

PARTICIPANTS

Patients with mutations in IKBKG from our center and reported in the literature.

MAIN OUTCOMES AND MEASURES

Skin and mucosal characteristics of patients with NEMO syndrome.

RESULTS

In addition to ectodermal dysplasia and recurrent infections, male patients had findings of ichthyosis, palmoplantar keratoderma, and inflammatory skin diseases. Both male and female patients had mucocutaneous ulcers and slow-to-heal chronic wounds. In combination with patients from the literature, 59% (85/144) of males had ectodermal dysplasia with anhidrosis (EDA) features, and 8% and 10% (12/144; 6/63) of males and females had dental findings, respectively. 4% (6/144) of males and 32% (20/63) of females had mucocutaneous ulcers. Ichthyosis/xerosis was present in 15% of males (21/144) but only 2% (1/63) females. Similarly, 13% (18/144) of male patients presented with dermatitis while this was reported in only 2% (1/63) of females.

CONCLUSIONS

Our results both confirm and expand upon the known spectrum of mucocutaneous findings in NEMO syndrome. Further genetic studies are needed to correlate specific mutations to clinical and morphologic subtypes.

Posttraumatic onychoheterotopia: A case and review of the pediatric literature

BACKGROUND

Onychoheterotopia, or ectopic nail, is a rare nail condition in which nail growth occurs in areas other than the distal phalanges. The majority of cases in the literature are noted to be congenital; however, acquired cases have less commonly been described following either acute or chronic trauma.

METHODS

We present a case of acquired onychoheterotopia in a child, with a corresponding literature review of acquired pediatric onychoheterotopia cases for comparison.

RESULTS

There were a total of 10 cases of acquired onychoheterotopia in pediatric patients in the literature. Including our patient, 81.8% (9/11) developed an ectopic nail on the fingers. Crush injury preceded the ectopic nails in 45.5 % (5/11) of cases. Infection occurred in 27.3% (3/11).

CONCLUSIONS

Although the incidence and prevalence of acquired onychoheterotopia are unknown, it seems to be an uncommon phenomenon. From our case and others from the literature, there may be associations with crush injury specifically. Further research will be needed to fully elucidate the pathophysiology and risk factors for ectopic nail growth.

Reliability and Recommended Settings for Pediatric Circumpapillary Retinal Nerve Fiber Layer Imaging Using Hand-Held Optical Coherence Tomography

Purpose

To investigate feasibility and reliability of 3-dimensional full circumpapillary retinal nerve fiber layer (cpRNFL) analysis in children, with and without glaucoma, without the use of sedation and to recommend a protocol for hand-held optical coherence tomography use.

Methods

A cohort of pediatric glaucoma patients and normal children were imaged with hand-held optical coherence tomography to assess the feasibility of obtaining full cpRNFL. Two consecutive scans were acquired in a smaller sample to investigate test–retest repeatability and interassessor reproducibility. The cpRNFL thickness was assessed in four quadrants, at several visual angles from the optic nerve center.

Results

Scanning was attempted in both eyes of 90 children with pediatric glaucoma and 180 controls to investigate feasibility (mean age, 6.98 ± 4.42 years). Scanning was not possible in 68 eyes of glaucoma children mainly owing to nystagmus, unclear optical media, or high refractive errors. Where three-dimensional imaging was possible, success at obtaining full cpRNFL was 67% in children with glaucoma and 89% for controls. Seventeen children with pediatric glaucoma and 34 controls contributed to reliability analysis (mean age, 6.3 ± 3.63 years). For repeatability intraclass correlation coefficients across quadrants ranged from 0.63 to 0.82 at 4° and improved to 0.88 to 0.94 at 6°. Intraclass correlation coefficients for reproducibility were also highest at 6° (>0.97 across all quadrants).

Conclusions

We demonstrate that acquisition and measurement of cpRNFL thickness values using 3-dimensional hand-held optical coherence tomography volumes in awake children is both feasible and reliable and is optimal at 6° from optic nerve center.

Translational Relevance

Our recommended protocol provides guidance on how pediatric optic nerve pathologies are managed by clinicians.

Systemic immunosuppressive therapy for inflammatory skin diseases in children: Expert consensus-based guidance for clinical decision-making during the COVID-19 pandemic

BACKGROUND/OBJECTIVES

The COVID-19 pandemic has raised questions about the approach to management of systemic immunosuppressive therapies for dermatologic indications in children. Change to: Given the absence of data to address concerns related to SARS-CoV-2 infection and systemic immunosuppressive therapies in an evidence-based manner, a Pediatric Dermatology COVID-19 Response Task Force (PDCRTF) was assembled to offer time-sensitive guidance for clinicians.

METHODS

A survey was distributed to an expert panel of 37 pediatric dermatologists on the PDCRTF to assess expert opinion and current practice related to three primary domains of systemic therapy: initiation, continuation, and laboratory monitoring.

RESULTS

Nearly all respondents (97%) reported that the COVID-19 pandemic had impacted their decision to initiate immunosuppressive medications. The majority of pediatric dermatologists (87%) reported that they were pausing or reducing the frequency of laboratory monitoring for certain immunosuppressive medications. In asymptomatic patients, continuing therapy was the most popular choice across all medications queried. The majority agreed that patients on immunosuppressive medications who have a household exposure to COVID-19 or test positive for new infection should temporarily discontinue systemic and biologic medications, with the exception of systemic steroids, which may require tapering.

CONCLUSIONS

The ultimate decision regarding initiation, continuation, and laboratory monitoring of immunosuppressive therapy during the pandemic requires careful deliberation, consideration of the little evidence available, and discussion with families. Consideration of an individual's adherence to COVID-19 preventive measures, risk of exposure, and the potential severity if infected must be weighed against the dermatological disease, medication, and risks to the patient of tapering or discontinuing therapies.

Management of infantile hemangiomas during the COVID pandemic

The COVID-19 pandemic has caused significant shifts in patient care including a steep decline in ambulatory visits and a marked increase in the use of telemedicine. Infantile hemangiomas (IH) can require urgent evaluation and risk stratification to determine which infants need treatment and which can be managed with continued observation. For those requiring treatment, prompt initiation decreases morbidity and improves long-term outcomes. The Hemangioma Investigator Group has created consensus recommendations for management of IH via telemedicine. FDA/EMA-approved monitoring guidelines, clinical practice guidelines, and relevant, up-to-date publications regarding initiation and monitoring of beta-blocker therapy were used to inform the recommendations. Clinical decision-making guidelines about when telehealth is an appropriate alternative to in-office visits, including medication initiation, dosage changes, and ongoing evaluation, are included. The importance of communication with caregivers in the context of telemedicine is discussed, and online resources for both hemangioma education and propranolol therapy are provided.

Rebound Growth of Infantile Hemangiomas After Propranolol Therapy

BACKGROUND AND OBJECTIVES

Propranolol is first-line therapy for problematic infantile hemangiomas (IHs). Rebound growth after propranolol discontinuation is noted in 19% to 25% of patients. Predictive factors for rebound are not completely understood and may alter the management approach. The goal of the study was to describe a cohort of patients with IHs treated with propranolol and to identify predictors for rebound growth.

METHODS

A multicenter retrospective cohort study was conducted in patients with IHs treated with propranolol. Patient demographic characteristics, IH characteristics, and specifics of propranolol therapy were obtained. Episodes of rebound growth were recorded. Patients' responses to propranolol were evaluated through a visual analog scale.

RESULTS

A total of 997 patients were enrolled. The incidence of rebound growth was 231 of 912 patients (25.3%). Mean age at initial rebound was 17.1 months. The odds of rebound among those who discontinued therapy at <9 months was 2.4 (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.3 to 4.5; P = .004) compared with those who discontinued therapy between 12 to 15 months of life. Female gender, location on head and neck, segmental pattern, and deep or mixed skin involvement were associated with rebound on univariate analysis. With multivariate analysis, only deep IHs (OR: 3.3; 95% CI: 1.9 to 6.0; P < .001) and female gender (OR: 1.7; 95% CI: 1.1 to 2.6; P = .03) were associated. Of those with rebound growth, 83% required therapeutic modification including 62% of patients with modifications in their propranolol therapy.

CONCLUSIONS

Rebound growth occurred in 25% of patients, requiring modification of systemic therapy in 15%. Predictive factors for rebound growth included age of discontinuation, deep IH component, and female gender. Patients with these predictive factors may require a prolonged course of therapy.

Papillon-lefevre syndrome with liver abscess

An 8 year old boy presented with fever of unknown origin in whom the diagnosis of liver abscess was made. He also had palmoplantar keratoderma and premature loss of teeth, consistent with the diagnosis of Papillon Lefevre syndrome.

Effects of phonemic awareness instruction on the encoding skills of children with severe speech impairment

PURPOSE

To examine the effects of phoneme-grapheme correspondence and phonemic awareness instruction on the encoding abilities of three pre-reading children with severe speech impairment (SSI).

METHOD

Using a single subject multiple baseline design across behaviours and participants, children received phoneme-grapheme awareness instruction followed by instruction in segmenting, manipulating, and encoding consonant-vowel-consonant (CVC) pseudowords.

RESULTS

Generalization occurred to encoding of novel CVC pseudo- and real words for two of the three participants.

CONCLUSIONS

Results suggest that phoneme-grapheme correspondence and phonemic awareness instruction is effective in developing encoding skills in children with SSI. Findings are consistent with those for other at-risk children.

Prognostic predictors of thalamic hemorrhage

BACKGROUND AND OBJECTIVE

There is no study evaluating the role of clinical, evoked potential and radiological parameters in the prognosis of thalamic hemorrhage employing multivariate logistic regression analysis, thus we aimed to evaluate the role of these parameters in predicting the 3 month outcome following thalamic hemorrhage.

SETTING

Tertiary care referral teaching hospital.

METHODS

Fifty-three patients with CT proven thalamic hematoma were evaluated. Conscious level was assessed using the Glasgow Coma Score (GCS), severity of stroke by the Canadian Neurological Scale (CNS), while muscle tone, tendon reflexes and power were also recorded. Hematoma size and type, and evidence of ventricular extension were obtained from the CT scan. Hematomas were classified as (A) thalamic with postero-lateral extension or (B) thalamic without postero-lateral extension. Central motor conduction to upper limb and median somatosensory evoked potentials (SEP) were recorded. Outcome was defined at 3 months on the basis of the Barthel Index (BI) with good being a BI of 12 or greater and poor a BI of less than 12. Best predictors of outcome were evaluated by single variable logistic regression analysis followed by multivariate logistic regression.

RESULTS

Age ranged between 35 and 85 years; 18 were women. Mean GCS was 10.4 and CNS was 3.9. Thirty-one patients had type A hematomas and 22 type B. The hematoma was small in 5, medium in 35 and large in 13 patients. Ventricular extension was present in 34 patients. Motor evoked potentials were unrecordable in 36 and central motor conduction time was prolonged in 8 patients. Median SEP was unrecordable in 37 and N9-N20 conduction time was prolonged in 2 patients. At 3 months, 8 patients had died, 24 had good and 21 had poor outcome. On univariate logistic regression analysis diabetes mellitus, GCS, pupillary asymmetry, CNS score, type and size of hematoma and motor and somatosensory evoked potentials were significant in relation to outcome. On multivariate logistic regression analysis, the best predictors of outcome at 3 months were the type of hematoma and CNS score.

CONCLUSION

CNS score and CT appearance of hematoma are the best predictors of 3 month outcome following thalamic hemorrhage. The proposed model for outcome assessment is simple and easy to apply and could have wide clinical application.

Hypoglycemia per se stimulates sympathetic neural as well as adrenomedullary activity, but, unlike the adrenomedullary response, the forearm sympathetic neural response is not reduced after recent hypoglycemia

We tested the hypotheses that 1) hypoglycemia per se stimulates the sympathetic neural as well as the adrenomedullary component of the sympathochromaffin system, and 2) sympathetic neural responses to hypoglycemia, like adrenomedullary responses, are reduced after recent hypoglycemia. To this end, we studied 10 healthy young adults on 2 consecutive days on two separate occasions, on one occasion with euglycemia (5.0 mmol/l) and on the other occasion with hypoglycemia (2.8 mmol/l) from 1000 to 1200 and 1400 to 1600 on day 1 of each occasion. On day 2 of each occasion, plasma epinephrine and norepinephrine (NE) concentrations and rates of systemic NE spillover (SNESO) and forearm NE spillover (FNESO) were measured during hyperinsulinemic (12.0 pmol x kg(-1) x min(-1)) euglycemia (5.0 mmol/l) and hypoglycemia (2.8 mmol/l). Compared with values during euglycemia, plasma epinephrine and NE and rates of SNESO and FNESO all increased during hypoglycemia (P < 0.01). After day 1 hypoglycemia, there were reductions during hypoglycemia on day 2 in plasma epinephrine (2,050 +/- 500 vs. 2,960 +/- 400 pmol/l; P < 0.02), plasma NE (1.35 +/- 0.16 vs. 1.92 +/- 0.20 nmol/l; P < 0.01), and SNESO rates (5.13 +/- 0.84 vs. 6.87 +/- 0.81 nmol/min; P < 0.02). However, FNESO rates were unaltered (1.16 +/- 0.25 vs. 1.27 +/- 0.17 pmol x min(-1) x 100 ml tissue(-1). Thus we conclude that 1) hypoglycemia per se stimulates both the sympathetic neural and adrenomedullary components of the sympathochromaffin system and 2) adrenomedullary, but not forearm sympathetic neural, responses to hypoglycemia are reduced after recent hypoglycemia. The extent to which the lower plasma NE levels and reduced SNESO responses to hypoglycemia after day 1 hypoglycemia reflect reduced NE release from the adrenal medullae, sympathetic nerves other than those in the forearm, or both cannot be determined from these data.

Norepinephrine response to exercise at the same relative intensity before and after endurance exercise training

It is well documented that endurance exercise training results in a blunted norepinephrine (NE) response to exercise of a given absolute exercise intensity. However, it is not clear what effect training has on the catecholamine response to exercise of the same relative intensity because previous studies have provided conflicting results. The purpose of the present study was, therefore, to determine the catecholamine response to exercise of the same relative exercise intensity before and after endurance exercise training. Six women and three men [age 28 +/- 8 (SD) yr] performed 10 wk of training. Maximal O2 uptake (VO2 max) was determined during treadmill exercise. Fifteen-minute treadmill exercise bouts were performed at 60, 65, 70, 75, 80, and 85% of VO2 max before and after training. VO2 max was increased by 20% (from 39.2 +/- 7.7 to 46.9 +/- 8.1 ml. kg-1. min-1; P < 0.05) in response to training. Plasma NE concentrations were higher (P < 0.05) during exercise at the same relative intensity after, compared with before, training at 65-85% of VO2 max. Differences between heart rates and plasma epinephrine concentrations after, compared with before, training were not statistically significant. These results provide evidence that the NE response to exercise is dependent on the absolute as well as the relative intensity of the exercise.

Forearm norepinephrine spillover during standing, hyperinsulinemia, and hypoglycemia

Plasma norepinephrine (NE) concentrations are a fallible index of sympathetic neural activity because circulating NE can be derived from sympathetic nerves, the adrenal medullas, or both and because of regional differences in sympathetic neural activity. We used isotope dilution measurements of systemic and forearm NE spillover rates (SNESO and FNESO, respectively) to study the sympathochromaffin system during prolonged standing, hyperinsulinemic euglycemia, and hyperinsulinemic hypoglycemia in healthy humans. Prolonged standing led to decrements in blood pressure without increments in heart rate, the pattern of incipient vasodepressor syncope. FNESO was not increased (0.58 +/- 0.20 to 0. 50 +/- 0.21 pmol. min-1. 100 ml tissue-1), suggesting that the approximately twofold increments in plasma NE and SNESO were derived from sympathetic nerves other than those in the forearm (with a possible contribution from the adrenal medullas). Hyperinsulinemia per se (euglycemia maintained) stimulated sympathetic neural activity, as evidenced by increments in FNESO (0.57 +/- 0.11 to 1.25 +/- 0.25 pmol. min-1. 100 ml tissue-1, P < 0.05), but not adrenomedullary activity. Hypoglycemia per se stimulated adrenomedullary activity (plasma epinephrine from 190 +/- 70 to 1720 +/- 320, pmol/l, P < 0.01). Although SNESO (P < 0.05) and perhaps plasma NE (P < 0.06) were raised to a greater extent during hyperinsulinemic hypoglycemia than during hyperinsulinemic euglycemia, FNESO was not. Thus these data do not provide direct support for the concept that hypoglycemia per se also stimulates sympathetic neural activity.

Absence of the dawn phenomenon and abnormal lipolysis in type 1 (insulin-dependent) diabetic patients with chronic growth hormone deficiency

To determine the role of growth hormone in overnight insulin requirements and lipolysis, five patients with chronic growth hormone deficiency and Type 1 (insulin-dependent) diabetes mellitus and six control patients with diabetes were each studied on two separate nights. Insulin was infused at a variable rate throughout one night to maintain euglycaemia and fixed at 04.00 hours on another. During the variable infusion, euglycaemia was maintained in control patients by a 36% increase in insulin infusion rate between 03.00 and 08.00 hours while a 46% decrease in the rate was required in growth hormone deficient patients (p less than 0.02). Despite this difference, mean free insulin values were equivalent. This finding is suggestive of increased insulin clearance in growth hormone sufficient patients. Glucose levels rose in control and fell in growth hormone deficient patients when insulin infusion rates were fixed at 04.00 hours. Glycerol production and non-esterified fatty acid concentrations were significantly lower in the growth hormone deficient diabetic patients, p less than 0.001, and when normalized with a heparin infusion, had no effect on insulin requirements. We conclude that: (1) growth hormone contributes to the development of the "dawn phenomenon," possibly by increasing insulin clearance (2) growth hormone helps sustain nocturnal lipolysis in Type 1 diabetes and (3) non-esterified fatty acids are not involved in the dawn phenomenon.

Plasma chromogranin A as a marker of sympathochromaffin activity in humans

The extent to which the sympathochromaffin system compared with other endocrine/neuroendocrine tissues contributes to the plasma chromogranin A pool has not been defined. To test the hypothesis that the sympathochromaffin system is the major source of circulating chromogranin A only when that system is activated markedly, we measured chromogranin A concentrations in 200 human plasma samples known to have a broad range of norepinephrine and epinephrine concentrations, reflecting therefore a broad range of sympathochromaffin activity at the time of sampling. Plasma chromogranin A and norepinephrine concentrations were highly correlated when the sympathochromaffin system was activated markedly (cardiac arrest samples, n = 13, r = 0.8392, P less than 0.0005) and when there was release of large amounts of norepinephrine from tumors (pheochromocytoma samples, n = 17, r = 0.8132, P less than 0.001). However, when the sympathochromaffin system was activated less markedly, resulting in plasma catecholamine concentrations that spanned the physiological and lower pathophysiological range (nonpheochromocytoma noncardiac arrest samples, n = 170), correlations between plasma chromogranin A and norepinephrine (r = 0.2877, P less than 0.0001) and epinephrine (r = 0.3814, P less than 0.0001) levels were relatively weak, although still statistically significant. Thus, at basal through moderate stress levels, norepinephrine and epinephrine concentrations accounted for only approximately 10-15% of the variance in plasma chromogranin A levels. We conclude that, although plasma chromogranin A concentrations are a valid marker of sympathochromaffin activity in humans, they are not a sensitive marker under physiological conditions.

Failure of nocturnal hypoglycemia to cause daytime hyperglycemia in patients with IDDM

To test the hypothesis that nocturnal hypoglycemia causes postprandial hyperglycemia the next day (the Somogyi phenomenon) in patients with insulin-dependent diabetes mellitus (IDDM), we studied 10 moderately well controlled patients, who were on their usual therapeutic regimens, from 2000 to 2000 on three occasions. On a control day, samples were obtained without intervention. On another day, nocturnal hypoglycemia was prevented (by intravenous infusion of glucose, if necessary, from 2200 to 0400 to keep plasma glucose levels at greater than 5.6 mM). On another day, nocturnal hypoglycemia was induced (by stepped intravenous insulin infusions between 2200 and 0200 to reduce plasma glucose levels to less than 2.8 mM). After nocturnal hypoglycemia (1.9 +/- 0.2 mM), fasting (0800), morning (0800-1100), afternoon (1200-1500), evening (1600-2000), and entire-day (0800-2000) plasma glucose concentrations were no higher than those after prevention of nocturnal hypoglycemia or sampling only. On the control day, fasting and daytime plasma glucose levels were directly related to the preceding 2200 (r = 0.723, P less than 0.02, and r = 0.762, P = 0.01, respectively) and nocturnal nadir (r = 0.714, P less than 0.02, and r = 0.728, P less than 0.02) plasma glucose concentrations. Daytime plasma glucose levels were unrelated to peak nocturnal plasma glucagon, epinephrine, norepinephrine, growth hormone, or cortisol concentrations. We conclude that nocturnal hypoglycemia does not appear to cause clinically important daytime hyperglycemia in patients representative of most patients with IDDM.

Human tissue adrenergic receptors are not predictive of responses to epinephrine in vivo

To test the hypotheses that adrenergic receptor and adenylate cyclase characteristics of easily accessible circulating cells reflect those of relatively inaccessible extravascular catecholamine target tissues in a subtype-specific fashion and that these characteristics predict responses to catecholamines in vivo, we studied 22 normal humans. Adrenergic receptors and their linked adenylate cyclase systems were measured in mononuclear leukocytes (MNL; beta 2), platelets (alpha 2), skeletal muscle membranes (beta 2), and fat cells (B1 and alpha 2) and compared with the responses to stepped, intravenous epinephrine infusions in vivo. MNL beta 2-adrenergic receptor densities (but not antagonist affinities) were correlated (r = 0.627; P less than 0.01) with skeletal muscle beta 2-adrenergic densities. However, other adrenergic receptor characteristics and basal and maximally stimulated adenosine 3',5'-cyclic monophosphate (cAMP) contents of MNL and all adrenergic receptor characteristics and cAMP contents of platelets were unrelated to the corresponding measurements in skeletal muscle and fat. Furthermore, there were no consistent relationships between tissue adrenergic receptor-adenylate cyclase characteristics and the chronotropic, diastolic depressor, lipolytic, ketogenic, glycemic, or glycogenolytic-glycolytic responses to epinephrine in vivo. Thus the data support the hypothesis that adrenergic receptor densities on circulating cells reflect those of extravascular target tissues in a subtype-specific fashion. On the other hand, the data do not support the hypothesis that physiological interindividual variation of adrenergic receptor characteristics is of sufficient magnitude to alter sensitivity to epinephrine in vivo.

Insulin, glucagon, and catecholamines in prevention of hypoglycemia during fasting

To dissect the mechanisms of the prevention of hypoglycemia during fasting, eight normal humans were studied after overnight and 3-day fasts. Prolonged fasting resulted in the expected decrements in base-line glucose production and plasma glucose, insulin, and C-peptide and increments in plasma glucagon, epinephrine, norepinephrine, growth hormone, and cortisol. After the overnight and 3-day fasts, insulin restoration (0.2 mU.kg-1.min-1) alone resulted in transient decrements in glucose production and only 15 and 19% decrements in plasma glucose, respectively. Selective glucagon deficiency (somatostatin infusion with insulin and growth hormone replacement) resulted in transient decrements in glucose production and additional 24 and 29% decrements in plasma glucose, respectively. Notably, plasma glucose plateaued under both fasting conditions in both instances. Combined alpha- and beta-adrenergic blockade (phentolamine and propranolol infusions) alone had no effect on glycemia under either fasting condition. However, progressive hypoglycemia developed during adrenergic blockade coupled with glucagon deficiency after the overnight fast (85 +/- 2 to 48 +/- 4 mg/dl, P less than 0.001) and after the 3-day fast (65 +/- 2 to 33 +/- 1 mg/dl, P less than 0.001). These were the result of both decrements in glucose production and increments in glucose clearance. Thus we conclude that during fasting 1) the prevention of hypoglycemia is not due solely to decreased insulin secretion. 2) Glucagon plays a primary counterregulatory role. Sympathochromaffin catecholamines are not normally critical but compensate and become critical when glucagon is deficient. Adrenomedullary epinephrine is probably the relevant catecholamine. 3) Other hormones, neurotransmitters, or substrate effects may, or may not, be involved; if they are, they appear to stand low in the hierarchy of glucoregulatory factors.

Increased fat and skeletal muscle beta-adrenergic receptors but unaltered metabolic and hemodynamic sensitivity to epinephrine in vivo in experimental human thyrotoxicosis

Based largely on evidence of increased target tissue beta-adrenergic receptor densities and responsiveness in animal and, to a lesser extent, human tissues, it is often assumed that thyroid hormone excess results in increased sensitivity to catecholamines in vivo, thus explaining several clinical manifestations of thyrotoxicosis. To test the hypothesis that thyrotoxicosis results in increased target tissue beta-adrenergic receptor densities and correspondingly increased metabolic and hemodynamic sensitivity to epinephrine in vivo, we measured these in 10 normal humans before and after administration of triiodothyronine (100 micrograms daily) for 10 d. Thyrotoxicosis increased beta-adrenergic receptor densities in fat (approximately 60%) and skeletal muscle (approximately 30%). Despite increments in beta-adrenergic receptor densities in these and probably other target tissues, metabolic and hemodynamic sensitivity to epinephrine in vivo was unaltered. An apparently adaptive increase in insulin secretion plausibly explains normal glycemic, glycogenolytic/glycolytic, lipolytic, and ketogenic sensitivity to epinephrine in the thyrotoxic state. In view of this striking homeostatic efficiency of the intact individual, the finding of altered adrenergic receptors, even in relevant target tissues, should not be extrapolated to altered sensitivity to catecholamines in vivo in the absence of direct testing of that hypothesis. With respect to the clinical issue, these data suggest that increased sensitivity to catecholamines does not explain clinical manifestations of thyrotoxicosis in humans.

Direct muscarinic cholinergic inhibition of hepatic glucose production in humans

To explore the potential role of the parasympathetic nervous system in human glucoregulatory physiology, responses to the muscarinic cholinergic agonist bethanechol (5.0 mg s.c.) and antagonist atropine (1.0 mg i.v.) were measured in normal humans. There were no changes in the plasma glucose concentration or rates of glucose production or utilization following atropine administration. After bethanechol administration there were no changes in the plasma glucose concentration or fluxes despite increments in plasma glucagon (75 +/- 7 to 103 +/- 10 pg/ml, P less than 0.02). There were no changes in insulin or C-peptide levels. To test the hypothesis that direct muscarinic inhibition of glucose production was offset by an indirect action of the agonist, specifically increased glucagon secretion with consequent stimulation of glucose production, bethanechol was administered while glucagon levels were held constant with the islet clamp technique (somatostatin infusion with insulin, glucagon and growth hormone replacement at fixed rates). Under that condition the muscarinic agonist induced a 25% decrement in the plasma glucose concentration (101 +/- 8 to 75 +/- 8 mg/dl, P less than 0.05). When compared with separate clamp control studies (with placebo rather than bethanechol injection) both the rate of glucose production and the glucose concentration were reduced (P less than 0.05) following bethanechol injection; the rate of glucose utilization was unaltered. Thus, we conclude: Withdrawal of parasympathetic tone does not appear to be an important glucoregulatory process in humans. Direct muscarinic cholinergic inhibition of hepatic glucose production occurs in humans but during generalized muscarinic activation this is offset by an indirect muscarinic action, increased glucagon secretion with consequent stimulation of glucose production. Thus, particularly if regional neuronal firing occurs, the parasympathetic nervous system may play an important role in human glucoregulatory physiology.

Direct relationship between mononuclear leukocyte and lung beta-adrenergic receptors and apparent reciprocal regulation of extravascular, but not intravascular, alpha- and beta-adrenergic receptors by the sympathochromaffin system in humans

To examine putative relationships between adrenergic receptors on accessible circulating cells and relatively inaccessible extravascular catecholamine target tissues, we measured mononuclear leukocyte (MNL) and lung beta-adrenergic receptors and platelet and lung alpha-adrenergic receptors in tissues obtained from 15 patients undergoing pulmonary resection. Plasma catecholamine concentrations were measured concurrently to explore potential regulatory relationships between the activity of the sympathochromaffin system and both intravascular and extravascular adrenergic receptors. MNL and lung membrane beta-adrenergic receptor densities were correlated highly (r = 0.845, P less than 0.001). Platelet alpha 2-adrenergic receptor and lung alpha 1-adrenergic receptor densities were not. Lung alpha 1-adrenergic receptor densities were positively related to plasma norepinephrine (r = 0.840, P less than 0.01) and epinephrine (r = 0.860, P less than 0.01) concentrations; in contrast, lung beta-adrenergic receptor densities were not positively related to plasma catecholamine concentrations (they tended to be inversely related to plasma norepinephrine and epinephrine [r = -0.698, P less than 0.05] levels). This apparent reciprocal regulation of alpha- and beta-adrenergic receptors by the sympathochromaffin system was only demonstrable with adrenergic receptor measurements in the extravascular catecholamine target tissue. Neither MNL beta-adrenergic receptor nor platelet alpha-adrenergic receptor densities were correlated with plasma catecholamine levels. Thus, although measurements of beta-adrenergic receptors on circulating mononuclear leukocytes can be used as indices of extravascular target tissue beta-adrenergic receptor densities (at least in lung and heart), it would appear that extravascular tissues should be used to study adrenergic receptor regulation by endogenous catecholamines in humans. These data provide further support for the concept of up regulation, as well as down regulation, of some adrenergic receptor populations during short-term activation of the sympathochromaffin system in humans.

Plasma glucose concentrations at the onset of hypoglycemic symptoms in patients with poorly controlled diabetes and in nondiabetics

We tested the hypothesis that during decrements in plasma glucose concentration, symptoms of hypoglycemia may occur at higher glucose concentrations in patients with poorly controlled insulin-dependent diabetes mellitus than in persons without diabetes. Symptoms of hypoglycemia and counterregulatory neuroendocrine responses were quantified during hypoglycemic and euglycemic clamp studies in eight patients with insulin-dependent diabetes mellitus selected because their hemoglobin A1 levels were above 10 percent. These data were compared with similar observations in 10 nondiabetic subjects studied previously. Glycemic thresholds--the plasma glucose concentrations during each hypoglycemic clamp study at which a given symptom or biochemical measurement first exceeded its 95 percent confidence interval determined in the euglycemic clamp studies--were calculated for each variable. The mean (+/- SE) glycemic threshold for the symptoms of hypoglycemia was 4.3 +/- 0.3 mmol per liter (78 +/- 5 mg per deciliter) in patients with poorly controlled diabetes--significantly higher (P less than 0.001) than the value of 2.9 +/- 0.1 mmol per liter (53 +/- 2 mg per deciliter) in subjects without diabetes. The mean glycemic thresholds for growth hormone, epinephrine, and cortisol secretions were not significantly different in the two groups. Thus, during decreases in the plasma glucose concentration, patients with poorly controlled insulin-dependent diabetes mellitus may experience symptoms of hypoglycemia at higher plasma glucose concentrations than persons without diabetes. The mechanism underlying this observation remains to be defined.

Glucagon, not insulin, may play a secondary role in defense against hypoglycemia during exercise

The sympathochromaffin system, probably sympathetic neural norepinephrine, plays a primary role in the prevention of hypoglycemia during exercise in humans. Our previous data indicated that changes in pancreatic islet hormones are not normally critical but decrements in insulin, increments in glucagon, or both become critical when catecholamine actions are blocked pharmacologically. To distinguish between the role of insulin and that of glucagon in this secondary line of defense against hypoglycemia during exercise in humans, glucoregulation during moderate exercise (approximately 55% of maximum O2 consumption over 60 min) was studied in people who could not decrease insulin but could increase glucagon, i.e., patients with insulin-dependent diabetes mellitus (IDDM). While receiving constant intravenous infusions of regular insulin, in individualized doses shown to result in stable plasma glucose concentrations of approximately 95 mg/dl before exercise, patients with IDDM were studied under two conditions: 1) a control study (n = 13) and 2) an adrenergic blockade study (propranolol infusion, n = 8). In the control study, mean plasma glucose concentrations did not change (from 95 +/- 2 to 100 +/- 11 mg/dl) during exercise despite constant plasma free insulin levels. In the adrenergic blockade study plasma glucose declined (from 96 +/- 2 to 74 +/- 7 mg/dl, P less than 0.01) but stabilized; hypoglycemia did not occur. Exercise-associated increments in plasma glucagon were comparable in the two studies. These data confirm that decrements in insulin are not critical to the prevention of hypoglycemia during moderate exercise in humans and indicate that compensation for deficient catecholamine action does not require decrements in insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of beta-adrenergic receptors of human skeletal muscle obtained by needle biopsy

Human skeletal muscle beta-adrenergic receptors were characterized by 125I-iodopindolol radioligand-binding studies of homogenates prepared from small muscle samples obtained by percutaneous needle biopsy from the gastrocnemius of six normal subjects. Binding was saturable, reversible, and stereospecific, with typical kinetics and a rank-order potency characteristic of a beta-adrenergic receptor. In saturation-binding studies, the receptor density was 9.7 +/- 1.9 fmol/mg protein, with a dissociation constant of 24 +/- 2.2 pM. Competition studies with selective antagonists revealed a population of receptors exclusively of the beta 2-subtype. Basal and isoproterenol-stimulated adenylate cyclase activities were 79 +/- 22 and 150 +/- 60 pmol adenosine 3',5'-cyclic monophosphate.min-1.mg protein-1, respectively. These results support pharmacological observations of beta-adrenergic receptor-mediated cellular responses in mammalian skeletal muscle. By use of these methods, small quantities of skeletal muscle obtained in this manner can be used to study in vivo beta-adrenergic receptor regulatory phenomena in humans.

Delayed extra-adrenal epinephrine secretion after bilateral adrenalectomy in rats

Regulated systemic extra-adrenal epinephrine secretion has been demonstrated in long-term bilaterally adrenalectomized humans. To determine whether this is demonstrable immediately after adrenalectomy and therefore presumably ongoing when the adrenal medullas are intact or if it develops over time after the adrenal medullas are removed, we measured plasma catecholamine concentrations before and serially after bilateral adrenalectomy with cortical reimplantation in rats. We found plasma epinephrine concentrations to decrease from 244 +/- 41 pg/ml to levels that were not convincingly detectable, using a single-isotope derivative assay with a detection limit of 10 pg/ml, for up to 1 wk after bilateral adrenalectomy with cortical reimplantation. Plasma epinephrine concentrations increased thereafter, becoming detectable in all animals and averaging 31 +/- 6 pg/ml 4 wk after adrenalectomy. Thus extra-adrenal epinephrine secretion appears to be a delayed response to removal of the adrenal medullas and cannot be assumed to be ongoing when the adrenal medullas are intact.

Glycemic thresholds for activation of glucose counterregulatory systems are higher than the threshold for symptoms

To define glycemic thresholds for activation of glucose counterregulatory systems and for symptoms of hypoglycemia, we measured these during stepped reductions in the plasma glucose concentration (in six 10-mg/dl hourly steps) from 90 to 40 mg/dl under hyperinsulinemic clamp conditions, and compared these with the same measurements during euglycemia (90 mg/dl) under the same conditions over 6 h in 10 normal humans. Arterialized venous plasma glucose concentrations were used to calculate glycemic thresholds of 69 +/- 2 mg/dl for epinephrine secretion, 68 +/- 2 mg/dl for glucagon secretion, 66 +/- 2 mg/dl for growth hormone secretion, and 58 +/- 3 mg/dl for cortisol secretion. In contrast, the glycemic threshold for symptoms was 53 +/- 2 mg/dl, significantly lower than the thresholds for epinephrine (P less than 0.001), glucagon (P less than 0.001), and growth hormone (P less than 0.01) secretion. Thus, the glycemic thresholds for activation of glucose counterregulatory systems during decrements in plasma glucose lie within or just below the physiologic plasma glucose concentration range, and are substantially higher than the threshold for hypoglycemic symptoms in normal humans. These findings provide further support for the concept that glucose counterregulatory systems are involved in the prevention, as well as the correction, of hypoglycemia.

Epinephrine is not critical to prevention of hypoglycemia during exercise in humans

We documented stability of plasma glucose concentrations and glucose production and utilization rates, and levels of other metabolic substrates and regulatory factors, during the islet clamp (somatostatin infusion with glucagon and insulin replacement) in the absence of an intervention in five normal humans and further applied this technique to the study of glucoregulation during moderate exercise. Based on previous evidence that sympathochromaffin activation plays a primary role in the prevention of hypoglycemia during exercise, the role of adrenomedullary catecholamines was assessed by exercise (60% of maximum oxygen consumption for 60 min) studies in four bilaterally adrenalectomized, epinephrine-deficient humans under two conditions: control (saline infusion) and islet clamp. Increased glucose utilization and production rates were matched and plasma glucose was unchanged during exercise under both conditions. Thus adrenomedullary catecholamines including epinephrine are not critical to glucoregulation during moderate exercise in humans even when changes in insulin and glucagon are prevented. These findings provide further support for the suggestion that sympathetic neural norepinephrine is the operative catecholamine in the prevention of hypoglycemia during exercise in humans.

Glucoregulation during exercise: hypoglycemia is prevented by redundant glucoregulatory systems, sympathochromaffin activation, and changes in islet hormone secretion

During mild or moderate nonexhausting exercise, glucose utilization increases sharply but is normally matched by increased glucose production such that hypoglycemia does not occur. To test the hypothesis that redundant glucoregulatory systems including sympathochromaffin activation and changes in pancreatic islet hormone secretion underlie this precise matching, eight young adults exercised at 55-60% of maximal oxygen consumption for 60 min on separate occasions under four conditions: (a) control study (saline infusion); (b) islet clamp study (insulin and glucagon held constant by somatostatin infusion with glucagon and insulin replacement at fixed rates before, during and after exercise with insulin doses determined individually and shown to produce normal and stable plasma glucose concentrations prior to each study); (c) adrenergic blockage study (infusions of the alpha- and beta-adrenergic antagonists phentolamine and propranolol); (d) adrenergic blockade plus islet clamp study. Glucose production matched increased glucose utilization during exercise in the control study and plasma glucose did not fall (92 +/- 1 mg/dl at base line, 90 +/- 2 mg/dl at the end of exercise). Plasma glucose also did not fall during exercise when changes in insulin and glucagon were prevented in the islet clamp study. In the adrenergic blockade study, plasma glucose declined initially during exercise because of a greater initial increase in glucose utilization, then plateaued with an end-exercise value of 74 +/- 3 mg/dl (P less than 0.01 vs. control). In contrast, in the adrenergic blockade plus islet clamp study, exercise was associated with glucose production substantially lower than control and plasma glucose fell progressively to 58 +/- 7 mg/dl (P less than 0.001); end-exercise plasma glucose concentrations ranged from 34 to 72 mg/dl. Thus, we conclude that: (a) redundant glucoregulatory systems are involved in the precise matching of increased glucose utilization and glucose production that normally prevents hypoglycemia during moderate exercise in humans. (b) Sympathochromaffin activation, perhaps sympathetic neural norepinephrine release, plays a primary glucoregulatory role by limiting glucose utilization as well as stimulating glucose production. (c) Changes in pancreatic islet hormone secretion (decrements in insulin, increments in glucagon, or both) are not normally critical but become critical when catecholamine action is deficient. (d) Glucoregulation fails, and hypoglycemia can develop, both when catecholamine action is deficient and when changes in islet hormones do not occur during exercise in humans.

External and internal standards in the single-isotope derivative (radioenzymatic) measurement of plasma norepinephrine and epinephrine

In plasma from normal humans (n = 9, 35 samples) and from patients with diabetes mellitus (n = 12, 24 samples) single-isotope derivative (radioenzymatic) plasma norepinephrine and epinephrine concentrations calculated from external standard curves constructed in a normal plasma pool were identical to those calculated from internal standards added to an aliquot of each plasma sample. In plasma from patients with end-stage renal failure receiving long-term dialysis (n = 34, 109 samples), competitive catechol-O-methyltransferase (COMT) inhibitory activity resulted in a systematic error when external standards in a normal plasma pool were used, as reported previously; values so calculated averaged 21% (+/- 12%, SD) lower than those calculated from internal standards. However, when external standard curves were constructed in plasma from a given patient with renal failure and used to calculate that patient's values, or in a renal failure plasma pool and used to calculate all renal failure values, norepinephrine and epinephrine concentrations were not significantly different from those calculated from internal standards. We conclude: (1) External standard curves constructed in plasma from a given patient with renal failure can be used to measure norepinephrine and epinephrine in plasma from that patient; further, external standards in a renal failure plasma pool can be used for assays in patients with end-stage renal failure receiving long-term dialysis. (2) Major COMT inhibitory activity is not present commonly if samples from patients with renal failure are excluded. Thus, it would appear that external standard curves constructed in normal plasma can be used to measure norepinephrine and epinephrine precisely in samples from persons who do not have renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced glycemic responsiveness to epinephrine in insulin-dependent diabetes mellitus is the result of the inability to secrete insulin. Augmented insulin secretion normally limits the glycemic, but not the lipolytic or ketogenic, response to epinephrine in humans

To determine if the enhanced glycemic response to epinephrine in patients with insulin-dependent diabetes mellitus (IDDM) is the result of increased adrenergic sensitivity per se, increased glucagon secretion, decreased insulin secretion, or a combination of these, plasma epinephrine concentration-response curves were determined in insulin-infused (initially euglycemic) patients with IDDM and nondiabetic subjects on two occasions: once when insulin and glucagon were free to change (control study), and again when insulin and glucagon were held constant (islet clamp study). During the control study, plasma C-peptide doubled, and glucagon did not change in the nondiabetic subjects, whereas plasma C-peptide did not change but glucagon increased in the patients. The patients with IDDM exhibited threefold greater increments in plasma glucose, largely the result of greater increments in glucose production. This enhanced glycemic response was apparent with 30-min increments in epinephrine to plasma concentrations as low as 100-200 pg/ml, levels that occur commonly under physiologic conditions. During the islet clamp study (somatostatin infusion with insulin and glucagon replacement at fixed rates), the heightened glycemic response was unaltered in the patients with IDDM, but the nondiabetic subjects exhibited an enhanced glycemic response to epinephrine indistinguishable from that of patients with IDDM. In contrast, the FFA, glycerol, and beta-hydroxybutyrate responses were unaltered. Thus, we conclude the following: Short, physiologic increments in plasma epinephrine cause greater increments in plasma glucose in patients with IDDM than in nondiabetic subjects, a finding likely to be relevant to glycemic control during the daily lives of such patients as well as during the stress of intercurrent illness. Enhanced glycemic responsiveness of patients with IDDM to epinephrine is not the result of increased sensitivity of adrenergic receptor-effector mechanisms per se nor of their increased glucagon secretory response; rather, it is the result of their inability to augment insulin secretion. Augmented insulin secretion, albeit restrained, normally limits the glycemic response, but not the lipolytic or ketogenic responses, to epinephrine in humans.

The human sympathochromaffin system

Hypoglycemia stimulates adrenomedullary epinephrine secretion; standing stimulates sympathetic neural norepinephrine release. In five bilaterally adrenalectomized persons plasma epinephrine, measured with a sensitive single-isotope derivative assay, rose from 15 +/- 2 to 35 +/- 7 pg/ml (P less than 0.02) during hypoglycemia but did not increase during standing. In contrast, plasma norepinephrine rose during standing but not during hypoglycemia. Thus, in humans 1) extra-adrenal epinephrine secretion is regulated and derived from innervated cells other than sympathetic postganglionic neurons; 2) because the plasma levels of epinephrine in adrenalectomized individuals even in response to the potent stimulus of hypoglycemia are below physiological thresholds, any biological actions of extra-adrenal epinephrine in adults must be paracrine rather than endocrine in nature; 3) hypoglycemia does not appear to stimulate the sympathetic nervous system. In view of these findings, we propose that extra-CNS catecholamine-producing tissues be termed the sympathochromaffin system consisting of two components: 1) the sympathetic nervous system that releases the neurotransmitter norepinephrine from its postganglionic neurons, and 2) the chromaffin tissues, including the adrenal medullae, that contain cells that secrete epinephrine, norepinephrine, or dopamine. The plasma epinephrine concentration is a valid measure of its chromaffin tissue (predominantly adrenomedullary) secretion, whereas the plasma norepinephrine concentration is an index of sympathetic neuronal activity under some but not all conditions.

Roles of glucagon and epinephrine in hypoglycemic and nonhypoglycemic glucose counterregulation in humans

Studies of two models of human glucose counterregulation, glucose recovery from insulin-induced hypoglycemia and the transition from exogenous glucose delivery to endogenous glucose production late after glucose ingestion, indicate that the principles of rapid hypoglycemic and nonhypoglycemic glucose counterregulation in these models are the same. 1) Neither is solely explicable on the basis of dissipation of insulin; 2) glucagon plays a primary counterregulatory role in both; 3) epinephrine compensates largely for deficient glucagon secretion in both; and 4) counterregulation fails to occur only in the absence of both glucagon and epinephrine in both. Thus, prevention as well as correction of hypoglycemia is effectively accomplished by redundant glucose counterregulatory systems, primarily glucagon and secondarily epinephrine, coupled with dissipation of insulin in humans. Other hormones, neural mechanisms, or autoregulation may be involved but need not be invoked and are not sufficiently potent to prevent or correct hypoglycemia when both of the key glucose counterregulatory hormones, glucagon and epinephrine, are deficient. Although confirmed in that they predict the impact of disease-related deficiencies of glucagon, epinephrine, or both, the extent to which these principles can be generalized to additional models of glucose counterregulation remains to be established. However, they provide a basis for plausible, testable hypotheses concerning the physiology and pathophysiology of glucose counterregulation.

beta 2- and alpha 2-adrenergic receptors and receptor coupling to adenylate cyclase in human mononuclear leukocytes and platelets in relation to physiological variations of sex steroids

In view of evidence, largely in animals, indicating effects of sex steroids on adrenergic receptors, we measured mononuclear leukocyte (MNL) beta 2-adrenergic receptors and adenylate cyclase sensitivity to stimulation by isoproterenol as well as platelet alpha 2-adrenergic receptors and sensitivity of sodium fluoride-stimulated adenylate cyclase to inhibition by epinephrine in 3 groups of normal humans with physiologically disparate levels of testosterone, estradiol, and progesterone (10 normal men and 10 normal women, the latter sampled in both the follicular and luteal phases of their menstrual cycles). Differences in testosterone, estradiol, and progesterone were as expected; testosterone levels were 10-fold higher in men, and progesterone levels were 20-fold higher in luteal phase women. T4, cortisol , and norepinephrine levels did not differ. Basal plasma epinephrine concentrations were slightly but significantly higher in luteal phase women [34 +/- 5 (+/-SE) pg/ml] than in follicular phase women (16 +/- 3 pg/ml; P less than 0.01) or men (20 +/- 3 pg/ml; P less than 0.05). There were no significant differences among these 3 groups in the densities or affinities of MNL beta 2-adrenergic or platelet alpha 2-adrenergic receptors or in the corresponding MNL and platelet adenylate cyclase sensitivities. Thus, there is not a generalized effect of physiological variations of testosterone, estradiol, and progesterone on adrenergic receptors or adenylate cyclase. To the extent that the adrenergic receptors and adenylate cyclase activities of circulating cells reflect those of extravascular catecholamine target cells, these data provide no support for a role of physiological variations of testosterone, estradiol, or progesterone in the regulation of catecholamine action in humans.

Oral propranolol and metoprolol both impair glucose recovery from insulin-induced hypoglycemia in insulin-dependent diabetes mellitus

To the extent that they have deficient glucagon secretory responses to plasma glucose decrements, as they commonly do, patients with insulin-dependent diabetes mellitus (IDDM) are dependent on epinephrine-mediated beta-adrenergic mechanisms to promote recovery from hypoglycemia. Thus, they are at increased risk for prolonged hypoglycemia if treated with a nonselective beta-adrenergic antagonist such as propranolol. If the hyperglycemic actions of epinephrine are mediated through beta 2-adrenergic mechanisms, therapeutic efficacy (e.g., for hypertension or ischemic heart disease) could be accomplished without increased risk of hypoglycemia by selective beta 1-adrenergic blockade in such patients. However, oral administration of the relatively selective beta 1-adrenergic antagonist metoprolol (100 mg) and of the nonselective beta-adrenergic antagonist propranolol (80 mg) both impaired recovery from insulin-induced hypoglycemia in patients with IDDM. Thus, at a dose of 100 mg, oral metoprolol is not safer than oral propranolol with respect to recovery from hypoglycemia in patients with IDDM.

Epinephrine supports the postabsorptive plasma glucose concentration and prevents hypoglycemia when glucagon secretion is deficient in man

We hypothesized that adrenergic mechanisms support the postabsorptive plasma glucose concentration, and prevent hypoglycemia when glucagon secretion is deficient. Accordingly, we assessed the impact of glucagon deficiency, produced by infusion of somatostatin with insulin, without and with pharmacologic alpha- and beta-adrenergic blockade on the postabsorptive plasma glucose concentration and glucose kinetics in normal human subjects. During somatostatin with insulin alone mean glucose production fell from 1.5 +/- 0.05 to 0.7 +/- 0.2 mg/kg per min and mean plasma glucose declined from 93 +/- 3 to 67 +/- 4 mg/dl over 1 h; glucose production then increased to base-line rates and plasma glucose plateaued at 64-67 mg/dl over 2 h. This plateau was associated with, and is best attributed to, an eightfold increase in mean plasma epinephrine. It did not occur when adrenergic blockade was added; glucose production remained low and mean plasma glucose declined progressively to a hypoglycemic level of 45 +/- 4 mg/dl, significantly (P less than 0.001) lower than the final value during somatostatin with insulin alone. These data provide further support for the concept that maintenance of the postabsorptive plasma glucose concentration is a function of insulin and glucagon, not of insulin alone, and that adrenergic mechanisms do not normally play a critical role. They indicate, however, that an endogenous adrenergic agonist, likely adrenomedullary epinephrine, compensates for deficient glucagon secretion and prevents hypoglycemia in the postabsorptive state in humans. Thus, postabsorptive hypoglycemia occurs when both glucagon and epinephrine are deficient, but not when either glucagon or epinephrine alone is deficient, and insulin is present.