Treatment of vitamin D deficiency/insufficiency with ergocalciferol is associated with reduced vascular access dysfunction in chronic hemodialysis patients

VDR alleviates endothelial cell injury in arteriovenous fistula through inhibition of P66Shc-mediated mitochondrial ROS

To investigate the effects and mechanism of Vitamin D receptor (VDR) signaling on arteriovenous fistula (AVF) endothelial cell injury. Venous tissues of AVF stenosis patients were collected and analyzed, vascular morphology, reactive oxygen species (ROS), and the expression of VDR, P66Shc, fibronectin (FN), collagen-1 (Col-1) were detected. In addition, human umbilical vein endothelial cells (HUVECs) was used in in vitro studies. HUVECs was incubated with transforming growth factor-beta (TGF-β, 50 ng/ml). Aditionally, paricalcitol, VDR overexpression plasmid and Pin1 inhibitor Juglone were used to investigate the regulatory mechanism of VDR in mitochondrial ROS. The parameters of ROS (e.g. MitoSox) and the expression of FN, Col-1 were tested. Moreover, the mitochondrial translocation of P66Shc was analyzed. The expression of VDR was obviously decreased in the venous tissues of AVF stenosis patients. On the contrary, the expression of P66Shc, P-P66Shc, FN, Col-1 and 8-OHdG were increased significantly in the venous tissues of AVF stenosis patients (P < 0.05). In line with this, the level of mitochondrial ROS and the expression of P66Shc, P-P66Shc, FN, Col-1 increased obviously in HUVECs cells under TGF-β condition. Both VDR over-expression plasmid and Pin1 inhibitor Juglone could alleviate TGF-β induced endothelial injury. Mechanistically, VDR overexpression plasmid and Juglone could inhibit the expression of Pin1, and then restrain P66Shc mitochondrial translocation, eventually reduce the level of mitochondrial ROS. Our research indicated that activation of VDR could alleviate venous endothelial cell dysfunction through inhibiting Pin1-mediated mitochondrial translocation of P66Shc and consequently reducing mitochondrial ROS. It suggested that VDR signaling might be an effective target for AVF stenosis treatment.

Association of vitamin D receptor gene TaqI, FokI and ApaI variants with arteriovenous fistula failure in hemodialysis patients

PURPOSE

We investigated the influence of the vitamin D receptor gene TaqI (rs731236), ApaI (rs7975232), and FokI (rs2228570) polymorphisms in arteriovenous fistula failure in hemodialysis patients.

METHODS

This study was carried out with 54 patients who experienced two or more fistula failures in the late period after arteriovenous fistula operation and 58 control patients with no history of arteriovenous fistula failure in 3 years or longer. The polymerase chain reaction-restriction fragment length polymorphism method was used to determine the vitamin D receptor TaqI, FokI, and ApaI polymorphisms.

RESULTS

For vitamin D receptor gene TaqI and Fok1 polymorphisms, no significant association was found between the two groups ( p > 0.05). However, a statistically significant association was determined for ApaI polymorphism between the two groups ( p = 0.02). In patients, ApaI AA, AC, and CC genotype frequencies were found as 21 (38.9%), 32 (59.3%), and 1 (1.8%), respectively. However, genotype frequencies of AA, AC, and CC in the control group were 29 (50%), 22 (37.9%), and 7 (12.1%), respectively. In all three polymorphisms, no significant difference was found between the two groups in terms of allele frequencies ( p > 0.05).

CONCLUSION

Vitamin D receptor ApaI AC genotype may be a possible cardiovascular risk factor for the development of arteriovenous fistula failure.

Factors influencing dialysis arteriovenous graft survival

PURPOSE

Dysfunction and loss of patency of dialysis arteriovenous grafts (AVGs) are serious causes of morbidity in patients on dialysis. Various risk factors associated with shorter AVG patency have been blamed, but the results of the studies were controversial. The aim of this study was to assess if associated diseases, biochemical markers and other parameters associated with atherosclerosis influence patency of AVGs in a large vascular access centre.

METHODS

We conducted a retrospective study that included patients with AVGs patent for at least 3 weeks after creation. We included variables associated with atherosclerosis into the analysis (coronary artery disease, diabetes mellitus, chronic heart failure, arterial hypertension, smoking history and cholesterol and triglyceride levels) and characteristics of the graft (shape, feeding artery).The data was assessed using log-rank (Cox-Mantel) test. The differences were shown using Kaplan-Meier graphs. The observation period was limited to 1000 days after access creation.

RESULTS

Overall, 338 patients were included in the study. Significantly higher risk of access failure was associated with presence of coronary artery disease (p = 0.0035). Higher serum cholesterol levels were associated with longer survival of the graft in 1000 days of surveillance (p = 0.04).

CONCLUSIONS

Coronary artery disease negatively influences the cumulative patency of vascular access. Higher serum cholesterol levels are associated with lower AVG failure risk over a 1000-day period, which probably corresponds to the worse disease status of the patients with lower cholesterol values.