Switching to Weekly Lonapegsomatropin from Daily Somatropin in Children with Growth Hormone Deficiency: The fliGHt Trial

INTRODUCTION

The phase 3 fliGHt Trial evaluated the safety and tolerability of once-weekly lonapegsomatropin, a long-acting prodrug, in children with growth hormone deficiency (GHD) who switched from daily somatropin therapy to lonapegsomatropin.

METHODS

This multicenter, open-label, 26-week phase 3 trial took place at 28 sites across 4 countries (Australia, Canada, New Zealand, and the USA). The trial enrolled 146 children with GHD, 143 of which were previously treated with daily somatropin. All subjects received once-weekly lonapegsomatropin 0.24 mg human growth hormone/kg/week. The primary outcome measure was safety and tolerability of lonapegsomatropin over 26 weeks. Secondary outcome measures assessed annualized height velocity (AHV), height standard deviation score (SDS), and IGF-1 SDS at 26 weeks.

RESULTS

Subjects had a mean prior daily somatropin dose of 0.29 mg/kg/week. Treatment-emergent adverse events (AEs) reported were similar to the published AE profile of daily somatropin therapies. After switching to lonapegsomatropin, the least-squares mean (LSM) AHV was 8.7 cm/year (95% CI: 8.2, 9.2) at Week 26 and LSM height SDS changed from baseline to Week 26 of +0.25 (95% CI: 0.21, 0.29). Among switch subjects, the LSM for average IGF-1 SDS was sustained at Weeks 13 and 26, representing an approximate 0.7 increase from baseline (prior to switching from daily somatropin therapy). Patient-reported outcomes indicated a preference for weekly lonapegsomatropin among both children and their parents.

CONCLUSIONS

Lonapegsomatropin treatment outcomes were as expected across a range of ages and treatment experiences. Switching to lonapegsomatropin resulted in a similar AE profile to daily somatropin therapy.

Safety and Efficacy of Lonapegsomatropin in Children With Growth Hormone Deficiency: enliGHten Trial 2-Year Results

PURPOSE

The objectives of the ongoing, Phase 3, open-label extension trial enliGHten are to assess the long-term safety and efficacy of weekly administered long-acting growth hormone lonapegsomatropin in children with growth hormone deficiency.

METHODS

Eligible subjects completing a prior Phase 3 lonapegsomatropin parent trial (heiGHt or fliGHt) were invited to participate. All subjects were treated with lonapegsomatropin. Subjects in the United States switched to the TransCon hGH Auto-Injector when available. Endpoints were long-term safety, annualized height velocity, pharmacodynamics [insulin-like growth factor-1 SD score (SDS) values], and patient- and caregiver-reported assessments of convenience and tolerability.

RESULTS

Lonapegsomatropin treatment during enliGHten was associated with continued improvements in height SDS through week 104 in treatment-naïve subjects from the heiGHt trial (-2.89 to -1.37 for the lonapegsomatropin group; -3.0 to -1.52 for the daily somatropin group). Height SDS also continued to improve among switch subjects from the fliGHt trial (-1.42 at fliGHt baseline to -0.69 at week 78). After 104 weeks, the average bone age/chronological age ratio for each treatment group was 0.8 (0.1), showing only minimal advancement of bone age relative to chronological age with continued lonapegsomatropin treatment among heiGHt subjects. Fewer local tolerability reactions were reported with the TransCon hGH Auto-Injector compared with syringe/needle.

CONCLUSIONS

Treatment with lonapegsomatropin continued to be safe and well-tolerated, with no new safety signals identified. Children treated with once-weekly lonapegsomatropin showed continued improvement of height SDS through the second year of therapy without excess advancement of bone age.

Efficacy and Safety of up to 2 Years of Treatment With TransCon hGH (Lonapegsomatropin) in Treatment-Naïve and Treatment-Experienced Children With Growth Hormone Deficiency

Background: Once-weekly TransCon hGH (lonapegsomatropin) is an investigational long-acting prodrug of somatropin in development for GHD. In the pivotal 52-week phase 3 heiGHt trial, lonapegsomatropin demonstrated superior annualized height velocity (AHV) compared to the same weekly dose of daily somatropin in treatment-naïve children with GHD. In the 26-week fliGHt trial, switch from daily somatropin to lonapegsomatropin provided continued growth and maintained a good safety profile. Methods: Results are reported from heiGHt and fliGHt subjects who continued into the open-label long-term extension enliGHten trial (data cut: June 1^st 2020). Subjects received either lonapegsomatropin (Group A; vial/syringe) or daily somatropin (Group B; pen device) in heiGHt, or lonapegsomatropin in fliGHt (Group C; vial/syringe). Upon entry into enliGHten, all subjects received lonapegsomatropin via vial/syringe, with subsequent switch to TransCon hGH Auto-Injector when available. Average IGF-1 was obtained on post-dose Day 5 (±1) in enliGHten. A by-visit ANCOVA model was used for numeric efficacy endpoints. Results: A total of 298 (98%) subjects continued into enliGHten. (A: n=103; B: n=55; C: n=140). The treatment difference in LS mean ∆ height SDS (A vs B) at the end of heiGHt (Week 52, 1.10 vs 0.96, P=0.015) was sustained through Week 104 (1.61 vs 1.49, P=0.158). For Group C, height SDS improved from −1.42 at fliGHt baseline to −0.69 at Week 78. AHV was within the expected range for 2^nd year therapy. Among children who switched (B), an attenuation in the expected 2^nd year decline of AHV suggested that lonapegsomatropin had an improved treatment effect relative to the previous daily somatropin. Mean (SD) average IGF-1 SDS remained stable and generally within the expected range for all groups (Week 104, A: 0.95 [1.22], B: 1.04 [1.25]; Week 78, C:1.81 [1.08]). An improvement in injection site tolerability was observed after switching to the TransCon hGH Auto-Injector; subjects and parents also indicated overall ease-of-use of the device (assessed by the Device Usability Questionnaire). With continued lonapegsomatropin treatment, the AE profile remained consistent with what was observed in the parent trials, with no new safety signals. Throughout enliGHten and the parent trials, non-neutralizing low-titer anti-hGH binding antibodies were detected post-dose in a total of 15 subjects (5.0%). Lab parameters were stable and generally remained within the normal range throughout the trials. As of the data cut, 2 subjects have achieved near adult height (AHV <2 cm/year over the last 9 months or bone age >14 [females] or >16 [males]) and thus have completed the trial. Conclusions: Children treated with lonapegsomatropin showed continued improvement of height SDS through their 2nd year of therapy. Lonapegsomatropin continued to demonstrate a safety profile comparable to that of daily somatropin therapy.

SAT-LB16 Maintenance of Favorable Treatment Effect of Once-Weekly TransCon hGH for Children With Growth Hormone Deficiency: Interim Analysis From the Enlighten Long-Term Extension Trial

Background Once-weekly TransCon hGH is an investigational long-acting prodrug for growth hormone deficiency (GHD) that consists of 3 components: unmodified growth hormone (hGH; somatropin), an inert carrier that protects it, and a linker that temporarily binds the two. In the randomized phase 3 heiGHt Trial evaluating treatment-naïve children with GHD, TransCon hGH demonstrated superior annualized height velocity and ∆ height standard deviation score (SDS) compared to Genotropin and had a similar safety and tolerability profile. Methods Results are reported from an interim analysis of subjects from heiGHt who continued in the ongoing enliGHten long-term extension trial for 26 weeks. In the 52-week heiGHt Trial, treatment-naïve, prepubertal subjects with GHD were randomized 2:1 to receive once-weekly TransCon hGH 0.24 mg hGH/kg/week or an equivalent weekly dose of daily Genotropin. Subjects completing heiGHt could enroll in enliGHten, where all subjects received TransCon hGH. Two groups were analyzed: Group A (TransCon hGH in both heiGHt and enliGHten) and Group B (Genotropin in heiGHt, followed by TransCon hGH in enliGHten). Safety and growth outcomes were evaluated approximately every 13 weeks in heiGHt and enliGHten. IGF-1 was sampled on postdose Day 5 (±1 day) in enliGHten. A by-visit ANCOVA model was used to analyze numeric efficacy endpoints.ResultsAll but one subject who completed heiGHt continued into enliGHten (A: N=103, B: N=55). Baseline characteristics at the start of heiGHt were balanced between groups. The statistically significant treatment difference in ∆ height SDS (Group A vs B) at the end of heiGHt (Week 52, N=159; 1.10 vs 0.96, P=0.0149) was sustained through Week 78 (N=154; 1.39 vs 1.24, P=0.0436), demonstrating persistence of catch-up growth for both groups and maintenance of superior treatment effect for subjects treated with TransCon hGH in the first year of therapy. At Week 78, least-squares mean (SE) IGF-1 SDS on postdose Day 5 (N=153) was 0.52 (0.15) for Group A and 0.59 (0.19) for Group B. Adverse events (AEs) were comparable between groups during heiGHt. During enliGHten, 48.7% (76/156) and 1.9% (3/156) of subjects experienced AEs and serious AEs, respectively; the AE profile was consistent with what was previously observed in heiGHt. A low titer of anti-hGH binding antibodies were detected in 10/156 (6.4%) subjects during treatment with TransCon hGH in heiGHt and enliGHten; no neutralizing antibodies were detected. Lab parameters (HbA1c, cortisol, free thyroxine) were stable and generally remained within the normal range throughout the trials. Mean (SD) BMI SDS was 0.0 (0.8) for Group A and 0.1 (0.9) for Group B at Week 78.Conclusions Children treated with TransCon hGH showed continued improvement of height SDS beyond the first year. Treatment with TransCon hGH through 78 weeks demonstrated an AE and immunogenicity profile comparable to that of a daily hGH therapy.

OR10-05 Phase 3 FliGHt Trial: Experience of Switching from Daily Growth Hormone Therapy to Once-Weekly TransCon HGH in Children with Growth Hormone Deficiency

Background: The Phase 3 fliGHt Trial evaluated children with growth hormone deficiency (GHD) of a broad range of baseline demographics and treatment durations who switched from daily growth hormone (hGH; somatropin) therapy to once-weekly TransCon hGH. TransCon hGH is an investigational long-acting prodrug consisting of 3 components: hGH, an inert carrier that protects it, and a linker that temporarily binds the two. When injected into the body, at physiologic pH and temperature, unmodified hGH is gradually released in a predictable manner.

Methods: All subjects initiated open-label once-weekly TransCon hGH 0.24 mg hGH/kg/week irrespective of prior daily hGH dose. Subjects 3 to 17 years old must have been treated with daily hGH for 13 to 130 weeks; subjects 6 months to 3 years old may have been treatment-naïve or treated with daily hGH for ≤130 weeks. The primary objective was to assess safety and tolerability over this 26-week trial. Efficacy measures included annualized height velocity (AHV), height standard deviation score (SDS), and insulin-like growth factor 1 (IGF-1) SDS.

Results: Of the 146 enrolled subjects, 98.6% completed the trial. Mean age at baseline was 10.6 years (range: 1, 17). The majority (97.9%) were treatment-experienced with a prior daily hGH mean dose of 0.29 mg/kg/week (range: 0.13, 0.49); 3 subjects were treatment-naïve and <3 years old. Just over half the subjects (56.8%) experienced a treatment-emergent adverse event (TEAE), with only 4.1% of subjects experiencing a TEAE considered related to study drug. No TEAE led to discontinuation of study drug. The type and frequency of TEAEs reported were similar to the published adverse event profile of daily hGH therapies. Mean hemoglobin A1c remained 5.2% at baseline and Week 26. No neutralizing antibodies were detected; low-titer anti-hGH binding antibodies were detected in 2.8% of subjects. Growth outcomes were as expected for this treatment-experienced heterogenous population, with a least-squares mean (LSM) AHV of 8.7 cm/year (95% CI: 8.2, 9.2) at Week 26 and LSM height SDS change from baseline to Week 26 of +0.25 (95% CI: 0.21, 0.29). In the age-defined subgroups, mean observed AHV at Week 26 ranged from 8.2 to 16.2 cm/year and mean observed height SDS change from baseline to Week 26 ranged from +0.23 to +0.96. Of note, the linear relationship between average IGF-1 SDS and TransCon hGH doses demonstrated in previous treatment-naïve trials was preserved in this population of treatment-experienced children who had dose titrations.

Conclusions: TransCon hGH treatment outcomes, including AHV and height SDS, were as expected across a diversity of ages, disease characteristics, and treatment experiences, reflective of a real-world setting. Dose titrations of TransCon hGH demonstrated a predictable IGF-1 response. Switching to TransCon hGH resulted in a similar adverse event profile to daily hGH therapy.

A Web-Delivered Multicomponent Intervention for Adolescents with Poorly Controlled Type 1 Diabetes: A Pilot Randomized Controlled Trial

Background

Type 1 diabetes is associated with significant mortality and economic cost. Management of type 1 diabetes involves completing multiple daily adherence behaviors, and many adolescents struggle with self-management and show poor glycemic control.

Purpose

The purpose was to conduct an unblinded pilot randomized controlled parallel-group study of a web-delivered multicomponent intervention targeting self-monitoring of blood glucose, working memory, and parent supervision of diabetes care among adolescents with type 1 diabetes. Intervention components included high magnitude incentives for adolescents and parents, motivational and cognitive behavioral therapy and working memory training for adolescents, and training in contingency contracting for parents.

Methods

Adolescents (N = 114) with poorly controlled type 1 diabetes were screened, and N = 61 were randomized using minimum likelihood allocation to usual care (usual care, N = 31) or to a 25-week/15-session web-delivered intervention (WebRx, N = 30).

Results

At the end of treatment, adolescents in WebRx had higher self-monitoring of blood glucose (d = 0.58) (primary outcome), better visual spatial working memory (d = 0.48) and inhibition (d = 0.98), and lower HbA1c (d = 0.45) than those in usual care. WebRx parents reported more frequent review of the adolescent's glucometer (d = 1.30) and reduced family conflict (d = 0.56). Between-condition differences were maintained 6 months later in self-monitoring of blood glucose (d = 0.42), visual spatial working memory (d = 0.76), family conflict (d = 0.50), and HbA1c (d = 0.44).

Conclusions

Results showing sustained effects on self-monitoring of blood glucose and HbA1c support moving forward with a larger trial to test this innovative web-delivered and multicomponent intervention. ClinicalTrials.gov Number (NCT01722643).

Counseling in Pediatric Populations at Risk for Infertility and/or Sexual Function Concerns

Reproductive health is an important yet often overlooked topic in pediatric health care; when addressed, the focus is generally on prevention of sexually transmitted infections and unwanted pregnancy. Two aspects of reproductive health counseling that have received minimal attention in pediatrics are fertility and sexual function for at-risk pediatric populations, and youth across many disciplines are affected. Although professional organizations, such as the American Academy of Pediatrics and the American Society of Clinical Oncology, have published recommendations about fertility preservation discussions, none of these guidelines address how to have ongoing conversations with at-risk youth and their families about the potential for future infertility and sexual dysfunction in developmentally appropriate ways. Researchers suggest many pediatric patients at risk for reproductive problems remain uncertain and confused about their fertility or sexual function status well into young adulthood. Potential infertility may cause distress and anxiety, has been shown to affect formation of romantic relationships, and may lead to unplanned pregnancy in those who incorrectly assumed they were infertile. Sexual dysfunction is also common and may lead to problems with intimacy and self-esteem; survivors of pediatric conditions consistently report inadequate guidance from clinicians in this area. Health care providers and parents report challenges in knowing how and when to discuss these issues. In this context, the goal of this clinical report is to review evidence and considerations for providers related to information sharing about impaired fertility and sexual function in pediatric patients attributable to congenital and acquired conditions or treatments.

The Metabolic Syndrome in Children and Adolescents: Shifting the Focus to Cardiometabolic Risk Factor Clustering

Metabolic syndrome (MetS) was developed by the National Cholesterol Education Program Adult Treatment Panel III, identifying adults with at least 3 of 5 cardiometabolic risk factors (hyperglycemia, increased central adiposity, elevated triglycerides, decreased high-density lipoprotein cholesterol, and elevated blood pressure) who are at increased risk of diabetes and cardiovascular disease. The constellation of MetS component risk factors has a shared pathophysiology and many common treatment approaches grounded in lifestyle modification. Several attempts have been made to define MetS in the pediatric population. However, in children, the construct is difficult to define and has unclear implications for clinical care. In this Clinical Report, we focus on the importance of screening for and treating the individual risk factor components of MetS. Focusing attention on children with cardiometabolic risk factor clustering is emphasized over the need to define a pediatric MetS.

Pilot Study of a Web-Delivered Multicomponent Intervention for Rural Teens with Poorly Controlled Type 1 Diabetes

Objective. The purpose of this study was to examine the feasibility and effectiveness of a web-delivered multicomponent behavioral and family-based intervention targeting self-regulation and self-monitoring of blood glucose levels (SMBG) and glycemic control (HbA1c) in teens with type 1 diabetes (T1DM) living in rural US. Methods. 15 teens with poorly controlled T1DM participated in a 25-week web-delivered intervention with two phases, active treatment (weekly treatment sessions and working memory training program) and maintenance treatment (fading of treatment sessions). Results. Almost all (13 of 15) participants completed at least 14 of 15 treatment sessions and at least 20 of 25 working memory training sessions. SMBG was increased significantly at end of active and maintenance treatment, and HbA1c was decreased at end of active treatment (p's ≤ 0.05). Executive functioning improved at end of maintenance treatment: performance on working memory and inhibitory control tasks significantly improved (p's ≤ 0.02) and parents reported fewer problems with executive functioning (p = 0.05). Improvement in inhibitory control was correlated with increases in SMBG and decreases in HbA1c. Conclusions. An innovative web-delivered and multicomponent intervention was feasible for teens with poorly controlled T1DM and their families living in rural US and associated with significant improvements in SMBG and HbA1c.

Pituitary tumors in childhood

PURPOSE OF REVIEW

This review focuses on recently published literature on pituitary tumors in children with special focus on craniopharyngioma and prolactinoma. Although most pituitary masses are benign neoplasms, they are associated with high morbidity and mortality related to their proximity to vital neurologic structures including the optic chiasm, hypophysis and hypothalamus, resulting in disruption of pituitary hormone secretion.

RECENT FINDINGS

The role of Wingless/β-beta catenin signaling and aryl hydrocarbon receptor-interacting protein mutations in pituitary tumor formation has been recognized. There is general agreement on optimal treatment of prolactinomas, although duration of medical therapy in children deserves more specific attention. Advances in imaging, medical, surgical and radiotherapy techniques have greatly increased survival rates for all pituitary tumors, but high recurrence rates after attempted complete resection and high progression rates after incomplete resection of craniopharyngioma remain troublesome. Long-term morbidity and late mortality of all pituitary tumors have become better appreciated with recent focus placed on severe obesity. A trend toward a more multidisciplinary approach for craniopharyngioma, including radiotherapy and chemotherapy, particularly when tumor burden involves the hypothalamus, continues.

SUMMARY

A vast amount of literature has been recently published, focusing on the management and long-term sequelae of all pituitary tumors in children. Craniopharyngioma remains the most challenging mass arising within sellar and parasellar areas, and optimal treatment continues to be hotly debated. Recognizing the rarity of pediatric pituitary tumors, the field would greatly benefit from more prospective multicenter trials, as well as from standardization of the assessment of preoperative function and post-treatment outcomes.

The effect of cinnamon on A1C among adolescents with type 1 diabetes

OBJECTIVE

The purpose of this study was to determine the effect of cinnamon on glycemic control in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Using a prospective, double-blind, placebo-controlled design, 72 adolescent type 1 diabetic subjects were treated in an outpatient setting with cinnamon (1 g/day) or an equivalent-appearing placebo for 90 days. A1C, total daily insulin intake, and adverse events were recorded and compared between groups.

RESULTS

There were no significant differences in final A1C (8.8 vs. 8.7, P = 0.88), change in A1C (0.3 vs. 0.0, P = 0.13), total daily insulin intake, or number of hypoglycemic episodes between the cinnamon and placebo arms.

CONCLUSIONS

Cinnamon is not effective for improving glycemic control in adolescents with type 1 diabetes.

Gizmos and gadgets in diabetes care: new tools for sweet kids

Diabetes care has become more complex as we strive to help children with diabetes achieve and maintain tight glycemic control. The technologic advances described herein have provided the means for safer, more convenient, and more effective diabetes care.

Lack of mutations in CYP2D6 and CYP27 in patients with apparent deficiency of vitamin D 25-hydroxylase

Activation of vitamin D requires hepatic 25-hydroxylation and renal 1alpha-hydroxylation. Defects in renal P450c1alpha are well-described, but few patients with defective vitamin D 25-hydroxylation are reported. The cytochrome P450 enzymes CYP2D6 and CYP27 are potential 25-hydroxylases. We sequenced both genes in two reported families with hepatic 25-hydroxylase deficiency and found no mutations. 25-Hydroxylation occurs in both mitochondria and microsomes. The existence genes encoding distinct enzymes would provide genetic redundancy, explaining the rarity of apparent vitamin D 25-hydroxylase deficiency.

Ambiguous genitalia with perineoscrotal hypospadias in 46,XY individuals: long-term medical, surgical, and psychosexual outcome

OBJECTIVES

To identify and study adults (21 years or older) who have a 46,XY karyotype and presented as infants or children with genital ambiguity, including a small phallus and perineoscrotal hypospadias, reared male or female.

METHODS

Participants were classified according to the cause underlying their intersex condition based on review of medical and surgical records. Long-term medical and surgical outcome was assessed with a written questionnaire and physical examination. Long-term psychosexual development was assessed with a written questionnaire and semistructured interview.

RESULTS

Thirty-nine (72%) of 54 eligible patients participated. The cause underlying genital ambiguity of participants included partial androgen insensitivity syndrome (n = 14; 5 men and 9 women), partial gonadal dysgenesis (n = 11; 7 men and 4 women), and other intersex conditions. Men had significantly more genital surgeries (mean: 5.8) than women (mean: 2.1), and physician-rated cosmetic appearance of the genitalia was significantly worse for men than for women. The majority of participants were satisfied with their body image, and men and women did not differ on this measure. Most men (90%) and women (83%) had sexual experience with a partner. Men and women did not differ in their satisfaction with their sexual function. The majority of participants were exclusively heterosexual, and men considered themselves to be masculine and women considered themselves to be feminine. Finally, 23% of participants (5 men and 4 women) were dissatisfied with their sex of rearing determined by their parents and physicians.

CONCLUSIONS

Either male or female sex of rearing can lead to successful long-term outcome for the majority of cases of severe genital ambiguity in 46,XY individuals. We discuss factors that should be considered by parents and physicians when deciding on a sex of rearing for such infants.

Expression and function of insulin/insulin-like growth factor I hybrid receptors during differentiation of 3T3-L1 preadipocytes

During the assembly of cell surface receptors, insulin proreceptors are sometimes joined to insulin-like growth factor (IGF) receptor precursors to form covalently linked hybrid receptors. To address the biological consequences of hybrid receptor formation, we studied 3T3-L1 cells known to undergo a 50-70-fold increase in insulin binding while maintaining nearly constant levels of IGF-I binding during differentiation from preadipocytes into adipocytes. The presence of insulin/IGF receptor hybrids in 3T3-L1 adipocytes was demonstrated by the immunoprecipitation of phosphorylated receptors and a novel enzyme-linked immunoassay. Hybrid receptor levels were very low in the early stages of differentiation and increased rapidly between days 4 and 6, reaching a level about 100-fold higher in the mature adipocyte. Coincident with the hybrid assembly, the formation of archetypal (alpha2,beta2) IGF receptors decreased. In fully differentiated adipocytes, virtually all of the IGF receptors were in hybrid form. Stimulation by IGF-I of receptors isolated from mature adipocytes caused autophosphorylation of IGF receptor beta subunits in hybrid complexes, whereas autophosphorylated IGF holoreceptors were not demonstrable. Insulin and IGF-I were equipotent in stimulating glucose uptake in the differentiated adipocytes, leading to the conclusion that hybrid insulin/IGF receptors can transduce a transmembrane signal when activated by IGF-I. We conclude that hybrid formation constitutes a novel post-translational mechanism whereby increased synthesis of insulin receptors limits the cell surface expression of the homologous IGF receptor. Furthermore, biological actions in 3T3-L1 adipocytes, previously attributed to archetypal IGF receptors, are in fact mediated through hybrid receptors.

Failure of insulin-like growth factor type I to suppress HIV type 1 in adult or umbilical cord mononuclear blood cells

Insulin-like growth factor type I (IGF-I) has been used as a treatment for cachexia in adults with AIDS and has been reported to show inhibitory activity against HIV-1IIIB in cord blood mononuclear cells (CBMCs) in vitro at low-concentration (1%) fetal bovine serum (FCS). We evaluated the effect of IGF-I on MN, IIIB, and BaL strains, as well as on a patient isolate of HIV-1 in CBMCs and adult peripheral blood mononuclear cells (PBMCs). IGF-I failed to show any inhibitory effect on HIV replication in CBMCs or adult PBMCs under various culture conditions. In contrast to an earlier report of an antiviral effect, IGF-I augmented HIV-1 replication in PHA-stimulated PBMCs maintained in a low concentration of FCS.

Insulin-like growth factor I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15

Most patients with deletion of the distal long arm of chromosome 15 have intrauterine growth retardation and postnatal growth deficiency in addition to developmental abnormalities. It has been proposed that the absence of one copy of the insulin-like growth factor I (IGF-I) receptor gene may play a role in the growth deficiency seen in this syndrome. To address this question we examined IGF-I receptor expression and function in fibroblasts from two patients with deletion of the distal long arm of chromosome 15 (15q26.1-->qter). Quantitative Southern blot analysis of the IGF-I receptor gene was performed on HindIII digests of fibroblast DNA. Radioactivity in the 1.7-kilobase receptor fragment in the two patients was 55% and 51% of the values in controls, consistent with the absence of one copy of the IGF-I receptor gene. IGF-I receptor messenger ribonucleic acid levels were quantitated by a solution hybridization/nuclease protection assay. Receptor messenger ribonucleic acid levels in the two patients were 45% and 52% of the values in controls. Northern blotting demonstrated normal size IGF-I receptor transcripts and affinity crosslinking of [125I]IGF-I to Triton X-100-solubilized fibroblasts demonstrated a normal size receptor in the patients. Analysis of placental membranes prepared from one patient revealed no difference in [125I]IGF-I binding. In the patients' fibroblasts, however, binding of [125I]long [R3]-IGF-I to the IGF-I receptor was significantly reduced, as assessed by the amount of radioactivity competed by the monoclonal antibody alpha IR-3 or insulin and Scatchard analysis of binding data. To assess IGF-I receptor function, stimulation of [alpha-1-14C]-methylaminoisobutyric acid transport and stimulation of [methyl-3H]thymidine incorporation into DNA by a full range of IGF-I concentrations was examined in patient and control fibroblasts. There was a significant decrease in the maximal response to IGF-I in both assays for one of the two patients when data were expressed as fold response over the basal value. However, there was no evidence for impairment of response to IGF-I in either patient's fibroblasts when data were expressed as net stimulation (maximal response minus basal). In conclusion, although IGF-I receptor expression was decreased in fibroblasts from two patients with deletion of the distal long arm of chromosome 15, we were unable to provide conclusive evidence for impairment of the biological response to IGF-I.

A possible genetic defect in 25-hydroxylation as a cause of rickets

We examined two siblings who had severe rickets at ages 2 and 7 years, respectively, despite a history of adequate vitamin D intake. The patients' sera had calcium concentrations at the lower limits of normal, low phosphate concentrations, elevated alkaline phosphatase activity, and low levels of 25-hydroxyvitamin D. Treatment with high doses of vitamin D2 resulted in resolution of the biochemical abnormalities and radiographic deformities; pharmacologic doses of vitamin D2 were required to maintain normal concentrations of 25-hydroxyvitamin D in the serum even though vitamin D absorption was normal. These children may have a genetic defect of the 25-hydroxylation step in vitamin D activation.

The 5'-untranslated region of the IGF-I receptor gene modulates reporter gene expression by both pre- and post-transcriptional mechanisms

The insulin-like growth factor I (IGF-I) receptor gene has a large, complex 5'-untranslated region (UTR). In order to examine the role that this region plays in regulating IGF-I receptor expression, we isolated fragments of the human IGF-I receptor 5'-UTR and interposed them between the SV40 early promoter and the chloramphenicol acetyl transferase reporter gene. Fragments of the IGF-I receptor gene 5'-UTR were found to enhance reporter gene expression by increasing gene transcription. In addition, the increased transcription and mRNA levels were in excess of the increase in enzyme activity, providing indirect evidence that these fragments inhibit translation, consistent with predictions.

Accuracy and precision of low-dose insulin administration

OBJECTIVE

To determine the lowest dose of concentrated (U100) insulin that can be reproducibly delivered.

METHODS

A telephone survey was used to determine current practices in major pediatric hospitals regarding the administration of low doses of concentrated insulin. A sensitive gravitometric technique was used to determine the error in measurement of low doses of U100 insulin by pediatric nurses and parents of diabetic children.

RESULTS

A telephone survey revealed that doses as low as 0.5 or 1.0 U (5 to 10 microL) are routinely administered in pediatric hospitals. In our study of pediatric nurses, attempts to deliver 0.5, 1.0, and 2.0 U resulted in delivered doses of 0.975 +/- 0.315, 1.638 +/- 0.376, and 2.153 +/- 0.435 U (mean +/- standard deviation of the mean), respectively. The use of 0.3-mL syringes compared to 0.5-mL syringes did not improve accuracy or precision. Taken as a group, parents of children with diabetes were more accurate (mean delivered dose of 1.063 +/- 0.276 for the 1-U dose), but the individual means ranged from 0.641 to 1.300 and coefficients of variation ranged from 5% to 33%. Only three of the seven parents could deliver 1.0 U with acceptable precision and accuracy.

CONCLUSIONS

When currently available syringes are used, insulin injections of less than 20 microL (2 U of U100) have an unacceptably large error. It is recommended that, in the inpatient setting, diluted insulin be used if the prescribed dose is less than 2.0 U.

Effects of insulin-like growth factor-I on androgen production by highly purified pubertal and adult rat Leydig cells

Leydig cells were isolated and purified from adult and midpubertal rats to study the effects of insulin-like growth factor-I (IGF-I) on steroidogenesis. Androgen production, as measured in Leydig cell conditioned culture media, from four different treatment groups (1 = no hormone; 2 = 70 ng/ml IGF-I; 3 = 0.1 ng/ml LH; 4 = 70 ng/ml IGF-I + 0.1 ng/ml LH) were compared daily. After 3 days in culture, the cells were treated with a maximally stimulating dose of luteinizing hormone (LH) (100 ng/ml) for 3 hours. Androgen production was highest in the cells treated with both IGF-I and low concentrations of LH. In the presence of IGF-I, regardless of LH, cells derived from pubertal animals had a greater increase in steroidogenesis during the culture period than did cells from adult animals. Pretreatment with IGF-I prior to maximal LH stimulation induced a greater increase in androgen production in cells from pubertal rats than in cells from adult animals. It is concluded that IGF-I has a direct effect on Leydig cells and may act synergistically with LH to promote androgen synthesis. The greater response in pubertal cells raises the possibility that IGF-I is important in the maturing process of the testis.

Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II

We investigated the binding properties of the type I insulin-like growth factor (IGF) receptor expressed in NIH-3T3 fibroblasts transfected with a human type I receptor cDNA. Cell surface receptors bound IGF-I with KD = 1 nM as predicted. Although recent studies have suggested that IGF-I and IGF-II bind to type I receptors with near-equal affinity, the receptors in this system bound IGF-II with much lower affinity (KD = 15-20 nM). When type I receptors from the transfected cells were solubilized and immunopurified, however, both 125I-IGF-I and 125I-IGF-II bound to the purified receptors with extremely high and relatively similar affinities (KD = 8 and 17 pM respectively). Thus the immunopurified receptors had higher affinity but lower specificity for the two ligands. The monoclonal antibody alpha IR-3 effectively inhibited IGF-I binding to cell surface receptors (75 +/- 10%), but did not inhibit IGF-II binding. In the purified receptor assay, alpha IR-3 also inhibited IGF-I binding more effectively than IGF-II binding (38 +/- 7% versus 10 +/- 4%). We conclude that the products of this cDNA can account for the binding patterns that we previously observed in receptors immunopurified from human placenta. The differential effect of alpha IR-3 on IGF-I versus IGF-II raises the possibility that these homologous growth factors bind to immunologically distinct epitopes on the type I receptor.

Analysis of the human type I insulin-like growth factor receptor promoter region

We isolated genomic fragments containing the 5' region of the human type I insulin-like growth factor receptor gene. A unique transcription start site was identified, defining a 1038 bp 5'-untranslated region. No TATA or CCAAT elements were identified in the proximal 480 nucleotides of 5'-flanking region. The region surrounding the transcription start site was similar to a recently described "initiator" sequence. The 5'-flanking and 5'-untranslated regions were highly GC-rich, with numerous potential Sp1 binding sites. A potential AP-2 binding site was identified in the 5'-flanking region and a potential thyroid response element was identified in the 5'-untranslated region. The 5' region of the human gene was very similar to that of the rat gene, with conservation of many of the potential regulatory elements.

Isolation and characterization of cDNA encoding the alpha subunit of Cap Z(36/32), an actin-capping protein from the Z line of skeletal muscle

cDNA encoding the alpha chain of Cap Z has been isolated by screening a lambda gt11 library with affinity-purified antibodies. A single cDNA insert (designated CE2) of 2153 base pairs (bp) contains an open reading frame of 836 bp, which is incomplete at its 5' end. The technique of "rapid amplification of cDNA ends" has been used to extend the 5' end of this open reading frame to a potential transcription initiation site that is preceded by 320 bp of an apparently untranslated region. The protein predicted by the resulting nucleotide sequence has a Mr of 32,960 and contains four regions that show close homology with four alpha-chymotryptic digestion fragments of the alpha chain. The amino acid composition of the alpha chain of Cap Z and the predicted protein are also similar. Northern blot analysis of whole chicken embryos shows two mRNA species of 1.9 and 2.4 kilobases, respectively, that hybridize with CE2. Three potential polyadenylylation signals in two regions of CE2 460 bp apart are identified, suggesting that the two messages may result from the use of alternative polyadenylylation sites. Comparison of the sequence data with that of other known actin-capping and severing proteins shows no significant homologies, suggesting that Cap Z may be a member of a unique group of capping, nonsevering proteins.

cDNAs encoding the beta subunit of cap Z, the actin-capping protein of the Z line of muscle

Three cDNAs encoding the beta chain of Cap Z have been isolated from lambda gt11 chicken libraries screened with antibodies. The coding region, which is identical among the cDNAs, contains 831 basepairs encoding a protein with 277 amino acid residues and Mr = 31,352. The predicted protein sequence contains eight regions that match perfectly the NH2-terminal sequence of eight peptides isolated from muscle Cap Z beta. The amino acid compositions of the protein predicted from the cDNA sequence and Cap Z beta are similar. Comparison of the cDNA sequence and the predicted protein sequence with those of other actin-binding proteins and all sequences in the GenBank and NBRF Protein databases shows no remarkable similarities. Two of the three cDNAs contain the complete coding region. Both coding regions begin with a consensus translation start site; however, their 5'-untranslated regions are different. Northern analysis of whole chicken embryos and adult chicken tissues shows two mRNA species. The embryo and non-muscle tissues have transcripts of 1.35 and 2.00 kilobases, and the muscle tissues have transcripts of 2.15 and 1.45 kilobases. Southern analysis of chicken genomic DNA shows that there are probably two related genes, one more similar to the cDNA than the other.

Isolation of rat testis cDNAs encoding an insulin-like growth factor I precursor

We have characterized rat testis cDNAs encoding insulin-like growth factor I (IGF-I) precursor to facilitate studies of IGF-I expression in the male reproductive system. Two clones, P2 and P3, with inserts of 786 and 1200 bp, respectively, were isolated from a lambda gt11 library of rat testis cDNAs. The longest open reading frame of cDNA P2 predicts a 153-amino-acid residue IGF-I precursor that has only 11 amino acid substitutions compared with a human IGF-IA precursor encoded by a human liver mRNA. Three substitutions are within the predicted rat IGF-I sequence: a Pro for Asp in the B domain, an Ile for Ser in the C domain, and Thr for Ala in the D domain. Only two substitutions distinguish the predicted rat sequence from a mouse liver IGF-IA precursor: Thr for Ala in the signal peptide and Ala for Ser in the D domain. P2 hybridizes with poly(A)+ mRNAs of 7.5, 4.7, 1.7, and 1.2-0.9 kb in rat liver and testis. The other testis cDNA, P3, appears to represent a partially processed rat IGF-I mRNA precursor. By comparing the sequence of cDNA P2 with that of cDNA P3 and a 2.3-kb rat IGF-I genomic fragment, we predict exon splice sites within the codon for residue 26 and between residues 86-87 of the rat IGF-I precursor. Both of the predicted splice sites align with exon-intron junctions in the human IGF-I gene. We conclude, therefore, that IGF-I is synthesized as a precursor in the rat testis and that the structure of IGF-I genes, mRNAs, and precursors are highly conserved across species.

Insulin-like growth factor II binding to the type I somatomedin receptor. Evidence for two high affinity binding sites

We have previously shown that the antireceptor antibody alpha IR-3 inhibits binding of 125I-somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) to the 130-kDa alpha subunit of the type I receptor in human placental membranes, but does not block 125I-insulin-like growth factor II (IGF-II) binding to a similar 130-kDa complex in these membranes. To determine whether the 130-kDa 125I-IGF-II binding complex represents a homologous receptor or whether 125I-IGF-II binds to the type I receptor at a site that is not blocked by alpha IR-3, type I receptors were purified by affinity chromatography on Sepharose linked alpha IR-3. The purified receptors bound both 125I-Sm-C/IGF-I and 125I-IGF-II avidly (KD = 2.0 X 10(-10) M and 3.0 X 10(-10) M, respectively). The maximal inhibition of 125I-Sm-C/IGF-I binding by the antibody, however, was 62% while only 15% of 125I-IGF-II binding was inhibited by alpha IR-3. In the presence of 500 nM alpha IR-3, Sm-C/IGF-I bound with lower affinity (KD = 6.5 X 10(-10) M) than IGF-II (KD = 4.5 X 10(-10) M) and IGF-II was the more potent inhibitor of 125I-Sm-C/IGF-I binding. These findings suggest that the type I receptor contains two different binding sites. The site designated IA has highest affinity for Sm-C/IGF-I and is blocked by alpha IR-3. Site IB has higher affinity for IGF-II than for Sm-C/IGF-I and is not blocked by alpha IR-3.

Cultured fibroblast monolayers secrete a protein that alters the cellular binding of somatomedin-C/insulinlike growth factor I

We studied somatomedin-C/insulinlike growth factor (Sm-C/IGF-I) binding to human fibroblasts in both adherent monolayers and in suspension cultures. The addition of Sm-C/IGF-I in concentrations between 0.5 and 10 ng/ml to monolayers cultures resulted in a paradoxical increase in 125I-Sm-C/IGF-I binding and concentrations between 25 and 300 ng/ml were required to displace the labeled peptide. The addition of unlabeled insulin resulted in no displacement of labeled Sm-C/IGF-I from the adherent cells. When fibroblast suspensions were used Sm-C/IGF-I concentrations between 1 and 10 ng/ml caused displacement, the paradoxical increase in 125I-Sm-C/IGF-I binding was not detected, and insulin displaced 60% of the labeled peptide. Affinity cross-linking to fibroblast monolayers revealed a 43,000-mol wt 125I-Sm-C-binding-protein complex that was not detected after cross-linking to suspended cells. The 43,000-mol wt complex was not detected after cross-linking to smooth muscle cell monolayers, and binding studies showed that 125I-Sm-C/IGF-I was displaced greater than 90% by Sm-C/IGF-I using concentrations between 0.5 and 10 ng/ml. Because fibroblast-conditioned medium contains the 43,000-mol wt complex, smooth muscle cells were incubated with conditioned medium for 24 h prior to initiation of the binding studies. 125I-Sm-C/IGF-I-binding increased 1.6-fold compared to control cultures and after cross-linking the 43,000-mol wt complex could be detected on the smooth muscle cell surface. Human fibroblast monolayers secrete a protein that binds 125I-Sm-C/IGF-I which can be transferred to the smooth muscle cell surface and alters 125I-Sm-C/IGF-I binding.

Evidence from monoclonal antibody studies that insulin stimulates deoxyribonucleic acid synthesis through the type I somatomedin receptor

Somatomedin-C/insulin-like growth factor-I (Sm-C/IGF-I) and insulin stimulate DNA synthesis and cell replication in cultured human fibroblasts. It has been postulated that the growth-promoting actions of both peptides are mediated through the type I Sm-C/IGF-I receptor. This study tests this hypothesis using two recently developed monoclonal antibodies. The antibody designated sm 1.2 is directed to Sm-C, whereas the antibody designated alpha IR-3 is directed against the type I receptor for Sm-C/IGF-I. Radiolabeled monoclonal antibody alpha IR-3 was bound to human foreskin fibroblasts in a reversible time-dependent fashion, with 90% of the specific binding complete after 6 h of incubation at 15 C. Binding of [125I]alpha IR-3 was completely inhibited by excess unlabeled antibody, but not by 50 nM Sm-C or 1000 nM insulin. Specific binding of [125I]Sm-C fell to 27% of the control value in the presence of 50 nM alpha IR-3, and this concentration of antibody significantly reduced the mitogenic response to both Sm-C and insulin. Antibody sm 1.2 blocked the mitogenic response to exogenous Sm-C, but did not block the response to insulin; indeed, in some experiments, sm 1.2 enhanced the response to insulin. We postulate that this enhancement is the result of neutralizing endogenously produced Sm-like substances. This study provides further evidence that the growth-promoting effects of insulin in this cell type are the result of interaction with the Sm-C/IGF-I receptor.