Abstract: Objective  To investigate the relationship between free mitochondrial DNA (mtDNA) level in outflow dialysate and chronic peritoneum inflammation in patients undergoing peritoneal dialysis (PD).  Methods  A total of 85 patients with PD for more than 6 months were enrolled and divided into group A (using dialysate with 1.5% glucose) and group B (using dialysate with 2.5% or 4.25% glucose more than twice a day). Blood samples were collected and serum biochemical parameters were tested. The outflow dialysate was collected to measure interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-18 (IL-18) and free mtDNA in the fluid. The differences of these parameters were compared between the two groups. The correlation between mtDNA in outflow dialysate and clinical parameters was analyzed. Multivariate regression was used to define the risk factors for mtDNA in dialysate.  Results  PD duration was longer (t=-2.206, P=0.030) and serum albumin was lower (t=2.635, P=0.010) in group B than in group A. IL-6, TNF-α, IL-1β, IL-18 and free mtDNA in the dialysate were significantly higher in group B than in group A           (t=-4.835, -6.557, -2.395, -2.318 and -3.920 respectively; P<0.001, <0.001, =0.019, =0.023 and <0.001 respectively). Free mtDNA level in the dialysate was positively correlated with the levels of IL-6, TNF-α, IL-1β and IL-18 in dialysate and PD duration (r=0.721, 0.418, 0.771, 0.634 and 0.240 respectively; P＜0.001, <0.001,    <0.001 and =0.03 respectively), and was negatively correlated with serum Alb (r=-0.319, P＜0.01). Multivariate linear regression showed that higher glucose concentration in dialysate (β=0.358, P=0.005), longer PD duration (β=0.292, P=0.000) and lower serum Alb concentration (β=-0.272, P=0.027) were the risk factors for higher free mtDNA in outflow dialysate.  Conclusion  Elevated mtDNA in outflow dialysate is associated with chronic micro-inflammatory status of the peritoneum in PD patients. Higher glucose concentration in dialysate, longer PD duration and lower serum Alb concentration are the risk factors for higher free mtDNA in outflow dialysate.

Key words: Peritoneal dialysis, Outflow dialysate, Mitochondrial DNA, Micro-inflammation