Hydroxyproline Influence on Oxalate Metabolism
This trial is active, not recruiting.
|Treatment||hydroxyproline and leucine|
|Phase||phase 1/phase 2|
|Collaborator||National Institutes of Health (NIH)|
|Start date||September 2013|
|End date||September 2016|
|Trial size||21 participants|
|Trial identifier||NCT02038543, 13-000150, U54DK083908|
Primary hyperoxaluria is an inborn error of metabolism that results in marked overproduction of oxalate by the liver. The excess oxalate causes kidney failure and can cause severe systemic disease due to oxalate deposition in multiple body tissues.
Metabolic pathways that lead to oxalate are poorly understood, but recent evidence suggests that hydroxyproline may play a role. Sources of hydroxyproline include the diet and bone turnover. If hydroxyproline can be confirmed as a signficant factor in primary hyperoxaluria, diet modification might be of value in reducing the severity of disease.
This protocol, in which hydroxyproline labelled with a cold isotope is infused intravenously in patients with primary hyperoxaluria, will allow us to measure the amount of oxalate produced from hydroxyproline. The contribution of hydroxyproline metabolism to the amount of oxalate excreted in urine in will be able to be determined for patients with each of the known types of primary hyperoxaluria.
|Endpoint classification||pharmacokinetics study|
|Intervention model||single group assignment|
The mean percent conversion of hydroxyproline to urinary oxalate
time frame: Participants will be followed for the duration of study infusion and observation, an average of 24 hours.
The mean percent conversion of hydroxyproline to urinary glycolate
time frame: Participants will be followed for the duration of the study infusion and observations, an average of 24 hours.
Male or female participants from 15 years up to 65 years old.
Inclusion criteria: - Confirmed diagnosis of primary hyperoxaluria - eGFR (by serum creatinine) > 50ml/min/1.73m2 Exclusion criteria: - eGFR < 50 ml/min/1.73m2 - History of liver or kidney transplant - Primary hyperoxaluria patients who have responded to pyridoxine therapy with reduction of urine oxalate excretion to < 0.45 mmol/1.73m2/day. - Pregnancy
|Official title||Influence of Hydroxyproline Plasma Concentration on Its Metabolism to Oxalate|
|Principal investigator||Dawn Milliner, MD|
|Description||The purpose of this study is to determine the contribution of hydroxyproline metabolism to urinary oxalate and glycolate excretion in patients with primary hyperoxaluria. Oxalic acid (COOH)2 is an end product of metabolism that is synthesized mainly in the liver. We have estimated that 10 - 20 mg is synthesized in the body of healthy adults each day (1). The main precursor of oxalate is glyoxylate (CHO•COOH). The bulk of the glyoxylate formed is normally transaminated to glycine (NH2•CH2•COOH) by alanine: lyoxylate aminotransferase (AGT) or reduced to glycolate (CHOH•COOH) by glyoxylate reductase (GR). Less than 10% of the glyoxylate is oxidized to oxalate by lactate dehydrogenase (LDH). In individuals with the disease, primary hyperoxaluria, AGT, GR, or HOGA enzyme is deficient and the amount of oxalate synthesized by the liver increases to 80 - 300 mg per day. The increased oxalate excreted in urine can cause damage to kidney tissue. Calcium oxalate stones may form in the kidney or calcium oxalate crystals may deposit in renal tubules and the renal parenchyma (nephrocalcinosis). An increased rate of oxalate synthesis could also contribute to idiopathic calcium oxalate stone disease. Understanding the pathways of endogenous oxalate synthesis and identifying strategies that decrease oxalate production could be beneficial for individuals with these diseases. Hydroxyproline is the primary source of glyoxylate identified in the body (2). Daily collagen turnover of bone results in the formation of 300 - 450 mg of hydroxyproline, which cannot be re-utilized by the body and is broken down. This metabolism yields 180 - 250 mg of glyoxylate. Further hydroxyproline is obtained from the diet, primarily from meat and gelatin-containing products. The bulk of the glyoxylate formed is converted to glycine by the liver enzyme AGT, some to glycolate and a small amount to oxalate. The proportion of these metabolites is not known with any certainty. In this study, a quantitative estimate of the metabolites formed will provide estimates of the contribution of hydroxyproline turnover to daily oxalate production. These experiments will provide valuable information for the future assessment of the contribution of hydroxyproline metabolism to oxalate production in individuals with primary hyperoxaluria.|
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