FGF23 and Angiotensin-(1-7) in Hypophosphatemia (GAP)

NCT ID: NCT03489993

Last Updated: 2022-08-05

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Total Enrollment

8 participants

Study Classification

OBSERVATIONAL

Study Start Date

2018-12-06

Study Completion Date

2020-12-23

Brief Summary

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Hereditary hypophosphatemia encompasses rare genetic conditions characterized by renal phosphate wasting. Increased circulating levels of fibroblast growth factor 23 (FGF23), a key regulator of phosphorus metabolism, are critical to the pathophysiology of these diseases, most notably in X-linked hypophosphatemia (XLH). Increased FGF23 induces hypertrophy and scarring in the heart in part via stimulating the traditional renin-angiotensin system (RAS) pathway, angiotensin-converting enzyme (ACE)/angiotensin (Ang ll), particularly in patients with chronic kidney disease, but the effect of FGF23 on the heart in patients with FGF23-related hypophosphatemic diseases is unknown. In addition, the relationship between FGF23 and the angiotensin-converting enzyme 2 (ACE2)/angiotensin-(1-7) (Ang-(1-7) pathway of the RAS is unknown.

The objective of this study is to describe the relationship between FGF23, which causes low phosphorus levels, and components of the RAS in the blood and urine to help the investigators understand why the disease occurs and how to better treat it.

Subjects will be identified by querying the Electronic Medical Record according to medical diagnosis. Thirty subjects, 2-24 years of age, will be recruited from the tertiary care Pediatric Endocrinology and Pediatric Nephrology clinics at Brenner Children's Hospital. Inclusion criteria include a confirmed diagnosis of hereditary FGF23-related hypophosphatemia. Clinical data will be obtained from the Electronic Medical Record. Each subject will undergo study assessments at baseline, 6 months and 1 year that include blood work, an echocardiogram, and blood pressure measurements.

The primary hypothesis is that subjects with higher Ang-(1-7) levels have lower rates of cardiac hypertrophy and thus are protected against high FGF23 levels. The secondary hypothesis is that subjects with higher Ang-(1-7) levels have lower systolic blood pressure.

Detailed Description

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Clinical data will be collected from the Electronic Medical Record, including age, sex, parent-reported race, past medical and family histories, and current medications. The investigators will calculate body mass index and define overweight/obesity as a body mass index ≥85% percentile for age and sex. The investigators will calculate the estimated glomerular filtration rate to measure renal function based on serum creatinine standardized to age, sex, and height.

Blood (less than 5 mL) and urine samples will be collected at each study visit at the same time as routine clinical labs. Ang ll and Ang-(1-7) will be measured in the plasma and urine using radioimmunoassays in a CLIA-certified laboratory within the Hypertension and Vascular Research Biomarker Analytical Core at Wake Forest School of Medicine. The investigators will calculate the ratio of the two peptides and, in the urine, standardize their values to urine creatinine. In the blood, creatinine, calcium, phosphorus, and vitamin D will be collected and in the urine, albumin, calcium, phosphorus, and creatinine will be collected all per standard of care. FGF23 and klotho will be analyzed in the Core via commercially available ELISA's.

All patients receive baseline and, if abnormal, follow-up echocardiograms to evaluate for left ventricular hypertrophy.

Blood pressure will be measured at clinic visits. Because age, sex, and height define normative pediatric values, the investigators will standardize blood pressure with z scores.

Conditions

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Hypophosphatemia X-linked Hypophosphatemia Renin-angiotensin System Left Ventricular Hypertrophy

Study Design

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Observational Model Type

COHORT

Study Time Perspective

PROSPECTIVE

Study Groups

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FGF23-Related Hypophosphatemic Diseases

The diagnostic tests Ang II, Ang-(1-7), FGF23, and klotho will be measured in the cohort. Patients in the cohort will have the diseases X-linked hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets (ADHR), autosomal recessive hypophosphatemic rickets type 1 (ARHR1), autosomal recessive hypophosphatemic rickets type 2 (ARHR2), osteoglophonic dysplasia, Jansen-type metaphyseal chondrodysplasia, Raine syndrome, McCune-Alright syndrome, and epidermal nevus syndrome (ENS).

Ang II and Ang-(1-7)

Intervention Type DIAGNOSTIC_TEST

Measured in plasma and urine using radioimmunoassays.

FGF23 and klotho

Intervention Type DIAGNOSTIC_TEST

Measured using ELISA's.

Interventions

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Ang II and Ang-(1-7)

Measured in plasma and urine using radioimmunoassays.

Intervention Type DIAGNOSTIC_TEST

FGF23 and klotho

Measured using ELISA's.

Intervention Type DIAGNOSTIC_TEST

Eligibility Criteria

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Inclusion Criteria

* Confirmed diagnosis of hereditary FGF23-related hypophosphatemia

Exclusion Criteria

* Acquired FGF23-related hypophosphatemia
* Age less than 2 years
* Age more than 24 years
* Inability to provide urine sample
Minimum Eligible Age

2 Years

Maximum Eligible Age

24 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No

Sponsors

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Wake Forest University Health Sciences

OTHER

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Principal Investigators

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Andrew M South, MD MS

Role: PRINCIPAL_INVESTIGATOR

Wake Forest University Health Sciences

Locations

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Wake Forest University Health Sciences

Winston-Salem, North Carolina, United States

Site Status

Countries

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United States

References

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Dalton GD, Xie J, An SW, Huang CL. New Insights into the Mechanism of Action of Soluble Klotho. Front Endocrinol (Lausanne). 2017 Nov 17;8:323. doi: 10.3389/fendo.2017.00323. eCollection 2017.

Reference Type BACKGROUND
PMID: 29250031 (View on PubMed)

Faul C, Amaral AP, Oskouei B, Hu MC, Sloan A, Isakova T, Gutierrez OM, Aguillon-Prada R, Lincoln J, Hare JM, Mundel P, Morales A, Scialla J, Fischer M, Soliman EZ, Chen J, Go AS, Rosas SE, Nessel L, Townsend RR, Feldman HI, St John Sutton M, Ojo A, Gadegbeku C, Di Marco GS, Reuter S, Kentrup D, Tiemann K, Brand M, Hill JA, Moe OW, Kuro-O M, Kusek JW, Keane MG, Wolf M. FGF23 induces left ventricular hypertrophy. J Clin Invest. 2011 Nov;121(11):4393-408. doi: 10.1172/JCI46122. Epub 2011 Oct 10.

Reference Type BACKGROUND
PMID: 21985788 (View on PubMed)

Gutierrez OM, Wolf M, Taylor EN. Fibroblast growth factor 23, cardiovascular disease risk factors, and phosphorus intake in the health professionals follow-up study. Clin J Am Soc Nephrol. 2011 Dec;6(12):2871-8. doi: 10.2215/CJN.02740311. Epub 2011 Oct 27.

Reference Type BACKGROUND
PMID: 22034506 (View on PubMed)

Isakova T, Xie H, Yang W, Xie D, Anderson AH, Scialla J, Wahl P, Gutierrez OM, Steigerwalt S, He J, Schwartz S, Lo J, Ojo A, Sondheimer J, Hsu CY, Lash J, Leonard M, Kusek JW, Feldman HI, Wolf M; Chronic Renal Insufficiency Cohort (CRIC) Study Group. Fibroblast growth factor 23 and risks of mortality and end-stage renal disease in patients with chronic kidney disease. JAMA. 2011 Jun 15;305(23):2432-9. doi: 10.1001/jama.2011.826.

Reference Type BACKGROUND
PMID: 21673295 (View on PubMed)

Kinoshita Y, Fukumoto S. X-Linked Hypophosphatemia and FGF23-Related Hypophosphatemic Diseases: Prospect for New Treatment. Endocr Rev. 2018 Jun 1;39(3):274-291. doi: 10.1210/er.2017-00220.

Reference Type BACKGROUND
PMID: 29381780 (View on PubMed)

Mitsnefes MM, Betoko A, Schneider MF, Salusky IB, Wolf MS, Juppner H, Warady BA, Furth SL, Portale AA. FGF23 and Left Ventricular Hypertrophy in Children with CKD. Clin J Am Soc Nephrol. 2018 Jan 6;13(1):45-52. doi: 10.2215/CJN.02110217. Epub 2017 Oct 12.

Reference Type BACKGROUND
PMID: 29025789 (View on PubMed)

Akimoto T, Yoshizawa H, Watanabe Y, Numata A, Yamazaki T, Takeshima E, Iwazu K, Komada T, Otani N, Morishita Y, Ito C, Shiizaki K, Ando Y, Muto S, Kuro-o M, Kusano E. Characteristics of urinary and serum soluble Klotho protein in patients with different degrees of chronic kidney disease. BMC Nephrol. 2012 Nov 23;13:155. doi: 10.1186/1471-2369-13-155.

Reference Type BACKGROUND
PMID: 23176706 (View on PubMed)

de Borst MH, Vervloet MG, ter Wee PM, Navis G. Cross talk between the renin-angiotensin-aldosterone system and vitamin D-FGF-23-klotho in chronic kidney disease. J Am Soc Nephrol. 2011 Sep;22(9):1603-9. doi: 10.1681/ASN.2010121251. Epub 2011 Aug 18.

Reference Type BACKGROUND
PMID: 21852584 (View on PubMed)

Drew DA, Katz R, Kritchevsky S, Ix J, Shlipak M, Gutierrez OM, Newman A, Hoofnagle A, Fried L, Semba RD, Sarnak M. Association between Soluble Klotho and Change in Kidney Function: The Health Aging and Body Composition Study. J Am Soc Nephrol. 2017 Jun;28(6):1859-1866. doi: 10.1681/ASN.2016080828. Epub 2017 Jan 19.

Reference Type BACKGROUND
PMID: 28104822 (View on PubMed)

Other Identifiers

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IRB00049606

Identifier Type: -

Identifier Source: org_study_id

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