Effects of Vitamin D Replacement on Hormones Regulating Iron Metabolism in Individuals With Chronic Kidney Disease
The purpose of the study is to learn more about how treatment with vitamin D can affect iron metabolism and blood levels of two hormones that control iron levels, hepcidin and hemojuvelin in people with chronic kidney disease (CKD).
Iron is an essential mineral which is a major component of proteins that carry oxygen in the blood. Problems with iron metabolism can lead to low blood levels (anemia), which can commonly happen in people with CKD.
New research over the last decade has uncovered a new hormone called `hepcidin', which is made in the liver and released into the blood. Hepcidin controls how much iron is in the blood by preventing the absorption of iron from food. Blood levels of hepcidin C are found to be high in people with CKD, and a recent small study in people with normal kidney function showed that treatment with vitamin D decreased hepcidin levels.
Another protein, known as `hemojuvelin', has been recently discovered and is also thought to control the amount of iron in the blood. The relationship between vitamin D and hemojuvelin has never been studied before.
In this study, investigators would like to examine the effects of vitamin D on iron metabolism and blood levels of hepcidin C and hemojuvelin in individuals with CKD.
Chronic Kidney Disease
Anemia of Chronic Disease
Drug: Oral Calcitriol 0.5 mcg once daily for 6 weeks
|Study Design:||Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor)
|Official Title:||Vitamin D Replacement in Chronic Kidney Disease and Its Effects on Iron Homeostasis, Serum Hepcidin, and Hemojuvelin Levels.|
- Change in serum hepcidin levels [ Time Frame: At Day 0, Day 3, 1 week, 4 weeks and 6 weeks ] [ Designated as safety issue: No ]
- Change in soluble hemojuvelin [ Time Frame: At Day 0, Day 3, 1 week, 4 weeks and 6 weeks ] [ Designated as safety issue: No ]
- Change in other indices of iron metabolism [ Time Frame: At Day 0, Day 3, 1 week, 4 weeks and 6 weeks ] [ Designated as safety issue: No ]Including, Serum Ferritin, Iron level, Percent transferrin saturation and TIBC
- Change in serum hemoglobin [ Time Frame: At Day 0, Day 3, 1 week, 4 weeks and 6 weeks ] [ Designated as safety issue: No ]
|Study Start Date:||October 2013|
|Study Completion Date:||June 2015|
|Primary Completion Date:||June 2015 (Final data collection date for primary outcome measure)|
Experimental: Oral Calcitriol
Oral Calcitriol 0.5 mcg once daily for 6 weeks
Drug: Oral Calcitriol 0.5 mcg once daily for 6 weeks
Other Name: Rocaltrol
Placebo Comparator: Placebo Arm
Placebo capsule 1 Capsule once daily for 6 weeks
Iron homeostasis is tightly regulated in humans. Iron is mostly recycled from hemoglobin, myoglobin and other enzymes. Since humans lack the capacity to excrete excess iron, it must be intricately regulated at the site of its absorption in the duodenum and proximal jejunum. In the last decade, hepcidin has emerged as a master regulator of iron homeostasis. It decreases iron absorption from the gut mucosa by limiting its transport from the enterocyte across the basolateral membrane into the circulation. It does so by down-regulating the synthesis or promoting internalization of a basolateral membrane protein `Ferroportin', the only known cellular iron exporter.
Vitamin D is hypothesized to exert a significant and independent effect on the iron metabolism. In the CKD population, low vitamin-D levels independently correlate with the severity of anemia. Hepcidin C levels are found to be elevated in the CKD population. Mechanisms underlying the effect of vitamin D on iron homeostasis potentially include vitamin D induced expression of erythropoietin receptors, increased proliferation of erythroid precursors, and reduction in hepcidin C levels due to reduction in IL-6 from the anti-inflammatory effects of vitamin D. More recently, a study revealed direct relationship between vitamin D replacement and a sustained fall in hepcidin C levels. The same group of researchers found the above relationship to be due to a direct effect of vitamin D on hepcidin expression.
Hemojuvelin (HJV) is a protein encoded by the HFE2 gene and is found in the membrane bound and the soluble form (sHJV) in the humans. Mutations in the HJV gene are responsible for Juvenile Hemochromatosis. It is an upstream regulator of hepcidin transcription and appears to be essential for hepcidin expression in the hepatocytes and has important role to play in iron homeostasis. Recently, an assay has become available to measure the sHJV levels in the serum.
Although, we know that hepcidin plays a central role in iron homeostasis and recent studies have given us insight into the role hemojuvelin and vitamin D play in iron metabolism, to date, no studies have examined the effect on vitamin D replacement on hepcidin, hemojuvelin levels and iron metabolism in individuals with CKD.
Hypothesis 1: Treatment with an activated vitamin D analog in the individuals with CKD results in a statistically significant fall in hepcidin C levels as compared to individuals provided with placebo.
Hypothesis 2: Treatment with an activated vitamin D analog results in decreased levels of soluble hemojuvelin in individuals with chronic kidney disease.
Hypothesis 3: Vitamin D replacement in the individuals with CKD results in improved iron parameters as compared to the placebo.
Please refer to this study by its ClinicalTrials.gov identifier: NCT01988116
|United States, Alabama|
|University of Alabama|
|Birmingham, Alabama, United States, 35294|
|Principal Investigator:||Bhupesh Panwar, MD||University of Alabama, Nephrology Division|
|Study Director:||Orlando M Gutierrez, MD,MMSc||University of Alabama, Nephrology Division|