Effects of Vitamin D Supplementation on Renal Function, Inflammation and Glycemic Control in Patients with Diabetic Nephropathy: a Systematic Review and Meta-Analysis

Abstract

Background/Aims: Vitamin D (VD) is widely recognized as renal protective. However, whether VD supplementation provides benefit to patients with diabetic nephropathy (DN) remains controversial. Here, we performed a meta-analysis to systematically evaluate the impact of VD supplementation on indexes of renal function, inflammation and glycemic control in DN patients, and to explore the potential renal protective mechanism of VD. Methods: We searched Pubmed, Embase, Cochrane Library, and three major Chinese biomedical databases (CNKI, WANGFANG and VIP) for randomized controlled trials (RCTs) examining the effects of VD or its analogs in DN patients, published between September 2007 and July 2018. Quality assessment and data extraction were performed independently by two authors, according to the Cochrane systematic review methods. Meta-analysis based on the extracted results were performed via Revman 5.2 software. Results: We included 20 RCTs representing 1,464 patients with DN in this meta-analysis. VD supplementation significantly reduced 24-hour urine protein [MD = -0.26; 95% CI (-0.34, -0.17); P < 0.00001; I² = 95%], UAER [MD = -67.36; 95% CI (-91.96, -42.76); P < 0.00001; I² = 97%], hs-CRP [MD = -0.69; 95% CI (-0.86,-0.53); P < 0.00001; I² = 0%], TNF-α [MD = -56.79; 95% CI (-77.05, -36.52); P < 0.00001; I² = 89%] and IL-6 [MD = -0.73; 95% CI(-1.03, -0.44); P < 0.00001; I² = 0%]. However, VD supplementation failed to decrease SCr [MD = -0.83; 95% CI (-3.67,2.02); P = 0.57; I² = 0%] or increase eGFR [MD = 2.13; 95% CI (-2.06, 6.32); P = 0.32; I² = 0%]. In addition, VD supplementation showed no impact on indexes of glycemic control, such as HbA1c [MD = 0.01; 95% CI (-0.09, 0.11); P = 0.84; I² = 0%] and FBG [MD = -0.05; 95% CI (-0.29, 0.20); P = 0.70; I² = 0%]. Analysis of 24-hour urine protein, SCr, eGFR, hs-CRP or HbA1c revealed no difference between subgroups based on the type of VD supplementation, including calcitriol, alfacalcidol and vitamin D3, and the dose or duration of calcitriol usage. Conclusion: In patients with DN, VD supplementation provides beneficial effects on 24-hour urine protein and inflammation indexes, but not on SCr, eGFR or glycemic control indexes. More RCTs that comprehensively evaluate the impact of VD supplementation on indexes of renal function, inflammation and glycemic control in DN atients are required in order to reach conclusive results.

Exercise therapy improves eGFR, and reduces blood pressure and BMI in non-dialysis CKD patients: evidence from a meta-analysis

“…Statistical analyses were carried out according to a previous published plan [12]. Results from 13 included RCTs were pooled and analyzed via Revman Review Manager version 5.3.…”

The Emerging Role of Vitamin D and Vitamin D Receptor in Diabetic Nephropathy

“…The results showed that VD supplements including calcitriol and alfacalcidol and 1,25(OH) 2 D 3 are beneficial for 24-hour urine protein and inflammation index and lessen high-sensitivity C-reactive protein (hs-CRP) but have no effects on hemoglobin A1c (HbA1c), serum creatinine (SCr), eGFR, and glycemic control index in DN patients. Besides, analysis based on different types of VD supplementations showed significant decreases of UAER and TNF-α in patients assigned to receive calcitriol [53]. Paricalcitol, a third-generation VD analog, is wildly used to prevent and treat DN leading to fewer episodes of hyperphosphatemia and hypercalcemia compared with calcitriol [54].…”

Effect of vitamin D on urinary angiotensinogen level in early diabetic nephropathy

“…[ 17 ] Although our study is a short follow-up, in consistent with our's, a recent metanalysis showed that eGFR was not affected by vitamin D supplementation in DN patients. [ 18 ]…”