Clinical trial NCT01541306: C-Type Natriuretic Peptide and Achondroplasia
Official title: C-Type Natriuretic Peptide and Achondroplasia
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Achondroplasia
Hypochondroplasia
Keywords: C-type natriuretic peptide
dwarfism
growth
achondroplasia
hypochondroplasia
biomarker
Lead sponsor: Nemours Children's Clinic
Sponsor class: OTHER
Collaborators: name: Alfred I. duPont Hospital for Children
name: University of Otago
First posted: 2012-02-29
Enrollment: 91
Sex: ALL
Minimum age (years): 3
Standard ages: CHILD
ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: CASE_ONLY
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: Children and adults with achondroplasia or hypochondroplasia

Brief summary: 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.

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.

Eligibility criteria: Inclusion Criteria:

* a diagnosis of achondroplasia or hypochondroplasia

Primary outcomes:
measure: NTproCNP level in plasma
timeFrame: one time point
Secondary outcomes:
measure: CNP level in plasma
timeFrame: one time point
measure: cGMP level in plasma
timeFrame: one time point
measure: Correlation between NTproCNP level and height velocity in children
timeFrame: Every six months over a period of a minumum of six months to a maximum of 2 years
Other outcomes:
Locations:
city: Wilmington
country: United States
facility: Alfred I. duPont Hospital for Children
state: Delaware
Study officials:
affiliation: Nemours Children's Clinic
name: Robert Olney, MD
role: PRINCIPAL_INVESTIGATOR
affiliation: Alfred I. duPont Hospital for Children
name: Michael Bober, MD, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: 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.