Abstract
BackgroundExperimental studies showed that 25-hydroxy-vitamin D [25(OH)D] deficiency (defined as 25-hydroxy-vitamin D < 15 ng/ml) has been associated with CKD progression. Patients with IgA nephropathy have an exceptionally high rate of severe 25(OH)D deficiency; however, it is not known whether this deficiency is a risk factor for progression of IgA nephropathy. We conducted this study to investigate the relationship between the plasma level of 25(OH)D and certain clinical parameters and renal histologic lesions in the patients with IgA nephropathy, and to evaluate whether the 25(OH)D level could be a good prognostic marker for IgA nephropathy progression.MethodsA total of 105 patients with biopsy-proven IgA nephropathy were enrolled between 2012 and 2015. The circulating concentration of 25(OH)D was determined using serum samples collected at the time of biopsy. The primary clinical endpoint was the decline of estimated glomerular filtration rate (eGFR; a 30 % or more decline compared to the baseline).ResultsMean eGFR decreased and proteinuria worsened proportionally as circulating 25(OH)D decreased (P < 0.05). The 25(OH)D deficiency was correlated with a higher tubulointerstitial score by the Oxford classification (P = 0.008). The risk for reaching the primary endpoint was significantly higher in the patients with a 25(OH)D deficiency compared to those with a higher level of 25(OH)D (P = 0.001). As evaluated using the Cox proportional hazards model, 25(OH)D deficiency was found to be an independent risk factor for renal progression [HR 5.99, 95 % confidence intervals (CIs) 1.59–22.54, P = 0.008].ConclusionA 25(OH)D deficiency at baseline is significantly correlated with poorer clinical outcomes and more sever renal pathological features, and low levels of 25(OH)D at baseline were strongly associated with increased risk of renal progression in IgAN.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0378-4) contains supplementary material, which is available to authorized users.
Highlights
Experimental studies showed that 25-hydroxy-vitamin D [25(OH)D] deficiency has been associated with chronic kidney diseases (CKD) progression
Recent observations suggest that low vitamin D levels, measured as 25-hydroxyvitamin D [25(OH)D] is significantly associated with a more severe decrease in estimated glomerular filtration rate (GFR) in patients with chronic kidney diseases (CKD) [7, 8]
Basic data and study endpoint Patient demographics as well as conventional clinical parameters including age, gender, body mass index (BMI), blood pressure (BP), blood chemistry and daily proteinuria were collected at the time of kidney biopsy
Summary
Experimental studies showed that 25-hydroxy-vitamin D [25(OH)D] deficiency (defined as 25-hydroxyvitamin D < 15 ng/ml) has been associated with CKD progression. Recent observations suggest that low vitamin D levels, measured as 25-hydroxyvitamin D [25(OH)D] is significantly associated with a more severe decrease in estimated glomerular filtration rate (GFR) in patients with chronic kidney diseases (CKD) [7, 8]. Experimental studies have revealed that VD insufficiency upregulates the reninangiotensin system [20, 21] and the NF-κB pathway [22], decreases the nitric oxide synthase transcription in vascular endothelial cells [23,24,25], increases inflammation and oxidative stress [26, 27], and may be a risk factor for progression of kidney diseases. To date there have been few studies exploring the relationship between the 25(OH)D level and the progression of IgAN, we studied this aspect
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