Factors associated with increased plasma homocysteine in patients using an amino acid peritoneal dialysis fluid

Glucoregulatory hormones and choice of osmotic agent in peritoneal dialysis

OBJECTIVE

The present study was performed to explore the range of effects of amino acid-based peritoneal dialysis (PD) solutions on glucoregulatory hormones in comparison with an osmotically equivalent glucose-based solution. ♢

METHODS

13 adult nondiabetic patients on PD underwent 2 peritoneal dwells of 2 hours' duration with either 1.5% dextrose solution or 1.1% amino acid solution. Serial sampling for glucoregulatory hormones was done throughout the duration of the dwell. ♢

RESULTS

Instillation of the 1.5% dextrose solution resulted in a modest change in plasma glucose, paralleled by a small increase in plasma insulin levels and plasma insulin-like growth factor (IGF-1). Plasma glucagon was not changed and plasma growth hormone level declined. Instillation of the 1.1% amino acid solution resulted in an increase in plasma glucose, plasma insulin, plasma glucagon, and plasma IGF-1. Plasma growth hormone level declined. Both solutions led to an increase in plasma norepinephrine but no changes were observed in epinephrine or dopamine. ♢

CONCLUSIONS

Our observations suggest that the mere replacement of glucose by amino acids in PD solutions does not necessarily imply "glucose sparing" from the perspective of induction of a glucoregulatory hormonal response because of the aminogenic stimulation of secretion of multiple hormones.

New insight of amino acid-based dialysis solutions

Malnutrition is a major complication of peritoneal dialysis (PD) and is associated with increased morbidity and mortality. Daily losses of proteins and amino acids (AAs) into dialysate contribute to this problem. Previous metabolic balance study demonstrated that treatment with 1.1% AA-based dialysis solution is safe and may improve protein malnutrition in continuous ambulatory peritoneal dialysis (CAPD) patients ingesting low protein intake. Other prospective studies also showed that AA solution can provide nutritional benefit for malnourished PD patients resulting in a significant improvement in some biochemical and/or anthropometric nutritional parameters. However, there are other studies showing no particular improvement in nutritional parameters after long-term use of AA solution. This may be related to the differences in the study design, sample size, methods used to assess nutritional status, and other factors such as dietary intake and comorbidities of study subjects. Published data will be reviewed to further emphasize the nutritional benefit of long-term use of AA solution in malnourished PD patients along with a brief discussion on the various reasons that may partly explain the different study results. We will also present the results of a longitudinal observational study evaluating changes in nutritional parameters following use of one exchange of 1.1% AA solution in malnourished Korean PD patients. A significant improvement of somatic protein status such as lean body mass (LBM) and hand grip strength was observed. No significant change in serum albumin level was noted. Patients with a positive estimated coefficient for LBM in the fitted regression model to the repeated observations over 1 year were classified as responders and patients with neutral or negative coefficient were considered as non-responders. Thirty-one out of 43 malnourished patients (72%) showed nutritional benefit based on the change of LBM. Hand grip strength and back lift strength were significantly higher in responders at baseline. Other baseline parameters did not differ between the two groups.

Peritoneal clearance of homocysteine with icodextrin or standard glucose solution exchange

BACKGROUND

The aim of the study was to assess plasma homocysteine concentration in peritoneal dialysis patients, and to compare the effect of different peritoneal solutions (glucose-based and icodextrin-based) on peritoneal clearance of homocysteine.

METHODS

The study group comprised 10 chronic peritoneal dialysis patients; the control group comprised 15 healthy, age-matched non-obese subjects with normal renal function. Patients with vitamin B(12) or folate deficiency were excluded. In all subjects, plasma homocysteine and dialysis adequacy parameters were assessed at baseline. The clearance study was carried out with 2.27% glucose and 7.5% icodextrin solutions (12-h dwell time).

RESULTS

Mean dialysate concentration of homocysteine was similar for both glucose and icodextrin solutions (8.3 +/- 3.2 and 8.4 +/- 1.9 micromol/L, respectively), but homocysteine clearance was significantly higher for icodextrin than glucose solution (1.82 +/- 0.57 vs 1.39 +/- 0.53 mL/min per 1.73 m(2)P = 0.01). Net ultrafiltration after icodextrin solution was also higher than after glucose solution (599 +/- 136 mL vs 134 +/- 337 mL, P < 0.01). A correlation between total plasma level of homocysteine and its peritoneal clearance was found (r = 0.69; P = 0.03).

CONCLUSION

It appears that peritoneal elimination of homocysteine depends primarily on its plasma concentration. Icodextrin-based solution for peritoneal dialysis seems to be more efficient in homocysteine elimination than a standard glucose-based solution.