European Journal of Cardiovascular Medicine

Vitamin D is an essential steroid hormone with effects extending beyond its classical role in bone-mineral disease. (1) Recently, the importance of vitamin D in the kidneys, cardiovascular disease, and cancer has been recognized. With these new roles being studied, there is growing interest in the therapeutic potential of vitamin D. (2)

Over the last three decades, chronic kidney disease (CKD) ranked among the top list of diseases responsible for the burden of mortality of the population globally. Earlier reports state that CKD stands 13th on the list of causes of death and in 2040, it is forecasted as the 5th cause of death. With 850 million individuals affected by kidney diseases, CKD is considered a major global public priority. Beyond other risk factors, CKD is one of the strongest risk factors for cardiovascular death. CKD metabolic bone disorder-related factors, and the accumulation of potentially toxic substances cleared by the kidney all contribute to atherosclerosis. (3,4)

Atherosclerosis is a process that starts at the level of endothelium, which is a dynamic, functionally complex organ involved in the regulation of several important biological mechanisms including the maintenance of vascular tone and permeability, inflammatory responses, immunity, and angiogenesis. Therefore, the preservation of the structure and functions of the endothelial cells is fundamental for vascular health. (5)

It is proposed that endothelial dysfunction is an early and critical event in atherosclerosis and is the principal pathophysiological mechanism that provides an important link between renal disease and the increased risk of CVD present in patients with CKD. (6)

Vitamin D plays a vital role in bone metabolism, cardiovascular disease, immune system, and kidneys (7) The study is designed to set up the standards for the supplementation of vitamin D at different stages of CKD patients undergoing haemodialysis.

It is a prospective – Multicentric study

A total number of 150 cases of CKD aged 50-80yras who were admitted in medicine ward of GGH Rangaraya Medical College and divided into three groups as per the stages of CKD. Group 1 with CKD stage 1 and 2 (n=50), Group 2 with CKD stage 3 and 4,(n=50) Group 3 with CKD stage 5 (n=50). 3 ml of Venous sample was collected and centrifuged at 3500 rpm to obtain the serum sample and it was processed for the analysis of Urea, Creatinine, eGFR, Vitamin D and Nitric Oxide.

Inclusion criteria the subjects are restricted to CKD patients in any stage of disease, with or without diabetes mellitus. Intervention was considered supplementation with any vitamin D compound.  Exclusion criteria were combined Vitamin D and Calcium treatment or comparison to other Vitamin D compounds or calcimimetics, without a non-treatment control group. Duration of the study 2 years and 6 months and the study was approved by Institutional ethical committee as an original research proposal. statistical analysis was performed by using SPSS.

Vitamin D and Nitric oxide analysis has been done by using ELABSCIENCE - ELISA end point assay with 450 nm. The standard graph was plotted, and the concentrations were derived as per the OD values(Figure 5 & 6). Urea and Creatinine were estimated by Beckman -coulter Fully automated biochemistry analyser. eGFR was estimated by the CKD- EPI formula.

In this study 3 groups were taken with Group 1(CKD stages 1&2); Group 2 (CKD stages 3&4 ) and Group 3 (CKD stages 5)  with 50 participants each. The percentage of male and female individuals was found to be 53% and 47% ( Figure 1) irrespective of CKD stages. The number of males and females in the respective CKD stages ( Figure 2) 

Figure 1: Male and Female population in the study

Figure 2: Distribution of participants based on gender and CKD stage

It was noted that in the overall participants included in the study, the male population is more in number than in females. This was similar to in case with CKD participants. In all the stages of CKD patients, the male participants are higher in number than the females. This indicates that CKD is more prevalent in males than in females.

The levels of vitamin D were estimated in all the groups (figure 3).

Figure 3: Mean Vitamin D (ng/ml) noted in all the stages of CKD

From the results, it was noted that, mean vitamin D was adequate in stages 1 and 2 of CKD than noted in other stages. It was observed from the results that, the vitamin D was decreased significantly in stages 3 to 5 which is shown in Figure 3.

Figure 4: Mean Nitric oxide (micromoles/L) in all the stages of CKD patients

It was noted that there was a sequential decrease in the levels of nitric oxide in all the stages of CKD.

Figure 5: STANDARD GRAPH OF NITRIC OXIDE

Figure: 6 STANDARD GRAPH OF VITAMIN D

Table 1:  Baseline Biochemical parameters in different stages of CKD.

Table 2: Correlation of vitamin D and Nitric oxide in CKD patients of all stages

Pearson correlation  was used to find out the correlation between vitamin D and Nitric oxide levels, the Pearson correlation coefficient (r) value was 0.9, which infers that there was a strong positive correlation between vitamin D and Nitric oxide in the CKD patients of the study with P<0.05. This implies that as the serum Vit D levels decreases, plasma NO levels also decreased in this study.

Vitamin D is a fat-soluble secosteroid that has a specific cytosolic receptor. This hormonal system is involved in the regulation of 3% of the human genome. It was first known to play a central role in calcium and phosphate metabolism; however, in recent times, Vitamin D deficiency has been associated with numerous events and conditions in the general population such as falls, fractures, diabetes, autoimmune diseases, cardiovascular and renal diseases, tuberculosis, neurodegenerative diseases and cancer, etc. 8,9

Nitric oxide (NO) the smallest signaling molecule, produced by nitric oxide synthase(NOS; EC 1.14.13.39).Its functions include synaptic plasticity in the central nervous system(CNS) central regulation of blood pressure, smooth muscle relaxation, and vasodilatation via peripheral nitregic nerves.

This literature supports the present study observations where low levels of vitamin D were noted in the CKD patients of stages 3,4 & 5. Humans acquire the majority (approximately 80%) of their vitamin D from sunlight-induced cutaneous synthesis and the rest comes from diet and supplements10.Hence supplementation of vitamin D might reduce the progression of CKD.

Nitric oxide levels in the present study were found to be significantly lower in all stages of CKD patients. This observation is in line with the findings of Wever et al who demonstrated that basal whole-body NO production is reduced in patients with chronic renal failure.11 Decreased NO levels observed in our study may reflect endothelial dysfunction which is reported in patients with CKD even in the early stages of the disease.

Multiple mechanisms can result in NO deficiency in patients with CKD including decreased availability of the substrate for NOS, L-arginine, and increased AMDA12. Hence in the study the correlation of vitamin D and NO in all the stages of CKD was determined by Pearson correlation coefficient.

It was found that there was a significant positive correlation between vitamin D and nitric oxide. Hence, the administration of vitamin D in CKD individuals might trigger the NO response which influences endothelial dysfunction. 

To conclude, short-term intervention with vitamin D can be associated with improvements in endothelial function in CKD patients. This indicates the positive effects of vitamin D on vascular disease in CKD. This study can suggest a relationship and not prove vitamin D deficiency as a cause of abnormal endothelial function. It does not investigate the mechanism of vitamin D-mediated injury to the cardiovascular system. Further studies are necessary to investigate if supplementation of vitamin D helps to improve endothelial function and explore the mechanism of such changes.

Author Contributions:  Conceptualization, writing-original draft preparation, all authors have read and agreed to the published version of the manuscript.

Funding:  Supported by Multidisciplinary research unit, Rangaraya Medical College, Kakinada A.P

Conflicts of interest:  The authors declare no conflict of interest.

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