6405: Influence of Hydroxyproline Plasma Concentration on its Metabolism to Oxalate

Status: Currently Closed to Accrual



Primary hyperoxaluria (PH) is a rare hereditary disorder that can cause elevated urinary oxalate levels, kidney stones, nephrocalcinosis (calcium deposits in the kidney tissue), and loss of kidney function that can lead to end stage kidney failure.

This study will enroll patients who are known to have primary hyperoxaluria and examine how hydroxyproline is broken down in a PH patient's body. The study will help us determine if hydroxyproline is broken down differently in patients with PH than it is in healthy persons who do not have PH.

Better understanding of how the body processes hydroxyproline and oxalate may help us identify strategies to reduce oxalate production and could be beneficial for individuals with PH. Such information may help us develop more effective treatments for hyperoxaluria.

The research questions are:

  1. How much hydroxyproline is broken down into oxalate and glycolate and eliminated by the kidneys into the urine?
  2. Are significant amounts of hydroxyproline metabolized (broken down) to oxalate in PH patients?
  3. Is hydroxyproline metabolized or reabsorbed differently in patients with different types of primary hyperoxaluria (PH types 1, 2, 3 or Non 1/Non 2/Non 3)?
  4. Could a reduction in the amount of hydroxyproline in the diet be of benefit to PH patients?

About this Study

Hydroxyproline is an amino acid, a substance that is found naturally in our bodies, especially in collagen that is needed for bones, skin, tendons, and ligaments. Hydroxyproline is a part of normal diets. As examples, meats and gelatin-containing foods have large amounts of hydroxyproline. Hydroxyproline is broken down in the body and becomes oxalate and glycolate that is eliminated in the urine.

This study is being done to determine how much the metabolism of hydroxyproline contributes to oxalate and glycolate in the urine of patients with primary hyperoxaluria. This study will also look at whether hydroxyproline is reabsorbed by the kidney and converted to glycolate and oxalate.

The study will be valuable in the search for new treatments for primary hyperoxaluria. There may be future benefit to primary hyperoxaluria patients from the data collected from this study since understanding the pathways of oxalate production in the body can help identify strategies to reduce oxalate.

There will be approximately 28 participants enrolled in this study:

6 patients in each group

  • PH type 1 = 8 patients
  • PH type 2 = 8 patients
  • PH type 3 = 6 patients
  • PH Non 1/Non 2/Non 3 = 6 patients

Subjects that agree to be in the study will be asked to participate in the following:

  • The study will be done at Mayo Clinic's Clinical Research Unit in Rochester, MN.
  • Patients will have blood and urine testing before the study starts to determine if they meet the study requirements.
  • Patients will have two phone appointments with a Mayo Clinic dietician to discuss detailed diet instructions. This diet, which uses normal foods, will be followed for severral days before coming to the Clinical Research Unit.
  • Patients will receive an IV infusion of hydroxyproline over 6 hours in the Clinical Research Unit
  • Blood and urine samples will be taken before, during and after the infusion in order to check the patient's levels of hydroxyproline, oxalate and glycolate.

Targeted Enrollment

To be eligible to participate, you must be an individual who is:

  • Between the ages of 15 and 65 years
  • Confirmed to have primary hyperoxaluria (PH), including types 1, 2, 3, and those with primary hyperoxaluria that are not PH type 1, 2, or 3
  • Good kidney function (eGFR by serum creatinine of 50mls/min/1.73m2 or greater)

You are not eligible to participate if you:

  • Are less than 15 years or greater than 65 years of age
  • Have reduced kidney function (eGFR greater than 50 ml/min/1.73m2)
  • Have had a liver or kidney transplant
  • Have responded to pyridoxine therapy with reduction of urine oxalate excretion to less than 0.45 mmol/1.73m2/day
  • Are pregnant
  • Are unwilling or unable to provide consent/assent

Estimated study completion is 9/30/2015.

How to participate

In order to participate in a study, you must personally contact the study coordinator of any of the participating institutions by phone or by e-mail. Please use the information below to inquire about participation.

United States


Mayo Clinic Hyperoxaluria Center, Rochester
Contact: Julie Olson, Barb Seide and Alicia Meek
Phone: 800-270-4637
E-mail: hyperoxaluriacenter@mayo.edu