C-Type Natriuretic Peptide and Achondroplasia

Achondroplasia and hypochondroplasia are the most common forms of dwarfism. Recent studies have shown that a small hormone called C-type natriuretic peptide (CNP) is an important regulator of linear growth. The investigators believe that genetic abnormality that causes achondroplasia and hypochondroplasia also disrupts CNP signaling, which may contribute to the growth problem. The investigators propose to look at levels of this and other closely related hormones in children and adults with achondroplasia or hypochondroplasia to see if they are different from levels in healthy people. The investigators hypothesis is that CNP levels are elevated in children with achondroplasia or hypochondroplasia, compared the healthy population. Another hypothesis is that CNP levels are not elevated in adults with achondroplasia or hypochondroplasia, since adults have no growth-plate cartilage. By studying the potential role of the CNP system in achondroplasia and hypochondroplasia, not only will the investigators provide further insight into the pathophysiology of these common syndromes, the investigators will also provide greater insight into the regulation of normal linear growth.

Study Overview

• Status: Completed
• Conditions: Achondroplasia; Hypochondroplasia

Detailed Description

Achondroplasia is the most common form of dwarfism and is characterized by short limbs with the thighs and upper arms being the most affected. Achondroplasia is also associated with a narrowing of the foramen magnum and spinal stenosis. Hypochondroplasia is a related, but less severe form of dwarfism that does not have the neurologic problems. Achondroplasia and hypochondroplasia are caused by mutations in the fibroblast growth factor receptor-3 (FGFR-3) gene that causes constitutive activation of the receptor. FGFR-3 signals primarily through the MAP kinase pathway, which is overactivated in growth plate chondrocytes in achondroplasia. C-type natriuretic peptide (CNP) is a hormone that is produced and acts in the growth plate as a potent positive regulator of linear growth. CNP signals through natriuretic peptide receptor-B (NPR-B), generating cGMP. Studies in mice show that activation of the MAP kinase pathway inhibits signaling through NPR-B. Hence the achondroplasia phenotype may be due in part to inhibition of CNP signaling. Conversely, CNP intracellular signaling inhibits the MAP kinase pathway and CNP analogs are being studied as a potential specific therapy for achondroplasia. The objective of this project is to define the state of the CNP system in children and adults with achondroplasia or hypochondroplasia. Our hypotheses are 1) blood levels of CNP and its aminoterminal propeptide (NTproCNP) are elevated and blood levels of cGMP are reduced in children with achondroplasia or hypochondroplasia, due to inhibition of NPR-B; 2) CNP and NTproCNP levels are normal in adults with achondroplasia and hypochondroplasia, due to their lack of growth plate cartilage; and 3) as in healthy children, NTproCNP levels predict height velocity in children with achondroplasia or hypochondroplasia. These hypotheses will be addressed with two specific aims. Specific aim 1 is to determine plasma levels of CNP, NTproCNP, and cGMP in children and adults with achondroplasia or hypochondroplasia. Specific aim 2 is to determine if NTproCNP levels correlate with height velocity in children with achondroplasia or hypochondroplasia.

The study is an observational, cross-sectional/partially longitudinal study of children and adults with achondroplasia or hypochondroplasia. Children will be seen as part of routine clinic visits. Children seen more than once during the study period will provide longitudinal data. Adult subjects with achondroplasia or hypochondroplasia will be studied a single time. Data collected will include anthropometrics, information on neurologic complications of achondroplasia, and blood levels of CNP, NTproCNP, and cGMP. We anticipate 100 subjects will be recruited, with about 20 being studied as many as three times during the course of the study.

By studying the potential role of the CNP system in achondroplasia and hypochondroplasia, not only will we provide further insight into the pathophysiology of these common syndromes, we will also provide greater insight into the regulation of normal linear growth.

• Study Type: Observational
• Enrollment (Actual): 91

Contacts and Locations

Study Locations

• United States
  • Delaware
    • Wilmington, Delaware, United States, 19803
      • Alfred I. DuPont Hospital for Children

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 3 months and older (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Children and adults with achondroplasia or hypochondroplasia

Description

Inclusion Criteria:

• a diagnosis of achondroplasia or hypochondroplasia

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Only
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
achondroplasia or hypochondroplasia; Children or adults with achondroplasia or hypochondroplasia

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
NTproCNP level in plasma	Aminoterminal propeptide of CNP (NTproCNP) is measured in plasma by RIA and compared to an existing sex- and age- based reference range.	one time point

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
CNP level in plasma	C-type natriuretic peptide is measured in plasma by RIA and compared to an existing sex- and age- based reference range.	one time point
cGMP level in plasma	Cyclic GMP levels are measured in plasma by RIA and compared to existing age- and sex- matched control samples.	one time point
Correlation between NTproCNP level and height velocity in children	NTproCNP levels at baseline will be correlated with hieght velocity determined at subsequent visits. Measurements for determination of height velocity will be at least 6 months apart, but no more than 2 years apart. For subjects with multiple subsequent visits, the visit closest to 1 year after the baseline visit will be used for height velocity determination.	Every six months over a period of a minumum of six months to a maximum of 2 years

Collaborators and Investigators

• Sponsor: Nemours Children's Clinic
• Collaborators: University of Otago; Alfred I. duPont Hospital for Children
• Investigators: Principal Investigator: Robert Olney, MD, Nemours Children's Clinic; Principal Investigator: Michael Bober, MD, PhD, Alfred I. DuPont Hospital for Children

Publications and helpful links

General Publications

• Olney RC, Prickett TC, Espiner EA, Mackenzie WG, Duker AL, Ditro C, Zabel B, Hasegawa T, Kitoh H, Aylsworth AS, Bober MB. C-type natriuretic peptide plasma levels are elevated in subjects with achondroplasia, hypochondroplasia, and thanatophoric dysplasia. J Clin Endocrinol Metab. 2015 Feb;100(2):E355-9. doi: 10.1210/jc.2014-2814. Epub 2014 Nov 11.

Study record dates

Study Major Dates

• Study Start: February 1, 2012
• Primary Completion (Actual): December 1, 2013
• Study Completion (Actual): December 1, 2014

Study Registration Dates

• First Submitted: February 13, 2012
• First Submitted That Met QC Criteria: February 28, 2012
• First Posted (Estimate): February 29, 2012

Study Record Updates

• Last Update Posted (Estimate): April 14, 2015
• Last Update Submitted That Met QC Criteria: April 13, 2015
• Last Verified: April 1, 2015

More Information

Terms related to this study

• Keywords: biomarker; growth; achondroplasia; dwarfism; C-type natriuretic peptide; hypochondroplasia
• Additional Relevant MeSH Terms: Genetic Diseases, Inborn; Musculoskeletal Diseases; Bone Diseases; Dwarfism; Bone Diseases, Developmental; Osteochondrodysplasias; Achondroplasia
• Other Study ID Numbers: Nemours FL IRB 302926