Prevalence and correlates of low plasma selenium concentrations in peritoneal dialysis patients

OBJECTIVE

Selenium is a key component in multiple enzyme systems, and dialysis patients with lower levels have been reported to have increased mortality. Low selenium levels were commonly reported in historic hemodialysis patients, but not in recent studies. There have been very few studies in peritoneal dialysis (PD) patients, and with the increasing age and frailty of our PD population we wished to review factors associated with lower selenium in PD patients.

DESIGN & METHODS

We retrospectively reviewed plasma selenium, normal laboratory >0.8 umol/L, measurements from a cohort of PD patients, attending for routine peritoneal membrane assessments, along with measurement of dialysis adequacy (Kt/Vurea), and normalized nitrogen appearance rate (nPNA) and bioimpedance measured extracellular water (ECW)/total body water (TBW), and skeletal muscle mass indexed for height (SMMI).

RESULTS

The median plasma selenium was 0.84 (IQR-0.72-1.01) umol/L in 406 PD patients, 61.1 % male, mean age 59.0 ± 15.5 years, 44.9 % diabetic with 15.8 % designated as clinically frail (CFS). 41.4 % had selenium deficiency (<0.8 umol/L), and was more common with increasing CFS (χ2-6.8, p < 0.009), comorbidity grade(χ2-26.74, p < 0.001).Plasma selenium correlated with serum total protein (TP) (r = 0.352), albumin (r = 0.358), nPNA (r = 0.263), and negatively with ECW/TBW (r= -0.321) all p < 0.001, and positively with SMMI (rho = 0.109, p = 0.03). On multivariable analysis selenium was independently associated with TP (β 0.799 ± 0.15,95 % confidence limits (95CL) (0.505-1.093), p=<0.001), and negatively with C reactive protein (CRP) (β -0.02 ± 0.01, (95CL -0.047 to -0.005) p = 0.01), and ECW/TBW (β -1.499 ± 0.42 (95CL -2.33 to -0.666) p=<0.001).

CONCLUSIONS

Compared to recent studies in hemodialysis patients, we report a 41 % prevalence for low selenium levels. Plasma selenium was positively associated with total serum protein, and negatively with CRP and ECW/TBW. Thus, lower selenium concentrations were linked to reduced dietary protein intake, and increasing frailty, inflammation and ECW/TBW ratios.

Comparative Study on Trace Element Excretions between Nonanuric and Anuric Patients Undergoing Continuous Ambulatory Peritoneal Dialysis

Few studies have been reported on alterations of trace elements (TE) in peritoneal dialysis patients. Our objective was to investigate and assess the characteristics of daily TE excretions in continuous ambulatory peritoneal dialysis (CAPD) patients. This cross-sectional study included 61 CAPD patients (nonanuric/anuric: 45/16) and 11 healthy subjects in Wuhan, China between 2013 and 2014. The dialysate and urine of patients and urine of healthy subjects were collected. The concentrations of copper (Cu), zinc (Zn), selenium (Se), molybdenum (Mo), and arsenic (As) in dialysate and urine were determined using inductively coupled plasma mass spectrometer (ICP-MS). Various clinical variables were obtained from automatic biochemical analyzer. Daily Cu, Zn, Se, and Mo excretions in nonanuric patients were higher than healthy subjects, while arsenic excretion in anuric patients was lower. A strong and positive correlation was observed between Se and Mo excretion in both dialysate (β = 0.869, p < 0.010) and urine (β = 0.968, p < 0.010). Furthermore, the clinical variables associated with Se excretion were found to be correlated with Mo excretion. Our findings indicated that nonanuric CAPD patients may suffer from deficiency of some essential TEs, while anuric patients are at risk of arsenic accumulation. A close association between Se and Mo excretion was also found.

[Importance of selenium homeostasis in chronic and end-stage kidney diseases]

Selenium is an essential trace element for the human body with a significant antioxidant effect. Selenium deficiency and excess are both detrimental for proper functioning of the human body. The possible association between selenium deficiency and acute or chronic renal disease, along with their complications has been less intensively investigated, however, there are firm data showing that selenium deficiency and renal failure increase the risk of both coronary artery disease and total mortality. Further studies revealed that selenium deficiency increases the risk of death due to infection in patients treated with hemodialysis through dysfunction of the immune system. However, there are no data whether the imbalance of selenium metabolism, especially selenium deficiency, could cause chronic kidney disease or renal failure. As far as results of selenium measurements, there is convincing evidence that protein loss and renal replacement treatment reduce serum selenium levels. Despite some contradictory results obtained from various studies regarding selenium deficiency in chronic kidney diseases, it seems that selenium supplementation may be beneficial in many patients with severe or end-stage kidney disease including those treated with dialysis.

Zinc supplementation alters plasma aluminum and selenium status of patients undergoing dialysis: a pilot study

End stage renal disease patients undergoing long-term dialysis are at risk for abnormal concentrations of certain essential and non-essential trace metals and high oxidative stress. We evaluated the effects of zinc (Zn) supplementation on plasma aluminum (Al) and selenium (Se) concentrations and oxidative stress in chronic dialysis patients. Zn-deficient patients receiving continuous ambulatory peritoneal dialysis or hemodialysis were divided into two groups according to plasma Al concentrations (HA group, Al > 50 μg/L; and MA group, Al > 30 to ≤ 50 μg/L). All patients received daily oral Zn supplements for two months. Age- and gender-matched healthy individuals did not receive Zn supplement. Clinical variables were assessed before, at one month, and after the supplementation period. Compared with healthy subjects, patients had significantly lower baseline plasma Se concentrations and higher oxidative stress status. After two-month Zn treatment, these patients had higher plasma Zn and Se concentrations, reduced plasma Al concentrations and oxidative stress. Furthermore, increased plasma Zn concentrations were related to the concentrations of Al, Se, oxidative product malondialdehyde (MDA), and antioxidant enzyme superoxide dismutase activities. In conclusion, Zn supplementation ameliorates abnormally high plasma Al concentrations and oxidative stress and improves Se status in long-term dialysis patients.

Trace minerals in patients with end-stage renal disease

The kidneys are famously responsible for maintaining external balance of prevalent minerals, such as sodium, chloride, and potassium. The kidney's role in handling trace minerals is more obscure to most nephrologists. Similarly, the impact of kidney failure on trace mineral metabolism is difficult to anticipate. The associated dietary modifications and dialysis create the potential for trace mineral deficiencies and intoxications. Indeed, there are numerous reports of dialysis-associated mishaps causing mineral intoxication, notable for the challenge of assigning causation. Equally challenging has been the recognition of mineral deficiency syndromes, amid what is often a cacophony of multiple comorbidities that vie for the attention of clinicians who care for patients with chronic kidney disease. In this paper, I review a variety of minerals, some of which are required for maintenance of normal human physiology (the U.S. Food and Drug Administration's list of essential minerals), and some that have attracted attention in the care of dialysis patients. For each mineral, I will discuss its role in normal physiology and will review reported deficiency and toxicity states. I will point out the interesting inter-relationships between several of the elements. Finally, I will address the special concerns of aluminum and magnesium as they pertain to the dialysis population.

Euthyroid Sick Syndrome and Nutritional Status are Correlated with Hyposelenemia in Hemodialysis Patients

Background

Maintenance hemodialysis (HD) patients have altered levels of thyroid hormone (TH) in euthyroid sick syndrome, along with low T3 levels and several nutritional metabolic disturbances. Selenium (Se) is an essential trace element for living organisms, which has been shown to play a major role in thyroid hormone levels and the nutritional metabolism. The aims of the present study were to assess the changes in serum levels of selenium and their correlation with disorders of the endocrine and nutritional metabolism in HD patients.

Methods

Fifty-three uremic patients with hemodialysis were evaluated; 30 healthy volunteers served as controls. Baseline serum concentrations of total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4), and free thyroxine (FT4) were determined by radioimmunoassay (RIA). Serum levels of thyroid-stimulating hormone (TSH) and intact parathyroid hormone (iPTH) were measured by a sensitive immunoradiometric assay (IRMA). Serum selenium was analyzed using Hitachi Z- 2000 polarized Zeeman atomic absorption spectrometry. Other metabolic variables were measured in all patients and control subjects. Multiple correlation analysis was performed among variables.

Results

Higher serum triglyceride, LDL-C, ApoB and lower albumin, HDL-C levels were found in subjects with HD. Mean serum selenium concentration was significantly lower in the HD group than in the control group (p<0.01). The levels of serum TT3 and FT3 in HD patients were significantly lower than in healthy control subjects (p<0.01; p<0.05, respectively), but TT4, FT4 and TSH were not different. However, serum iPTH levels were significantly higher in patients than in controls (p<0.01). In the group of HD patients, serum selenium levels were significantly positively correlated with albumin, HDL-C, TT3 and FT3; and negatively correlated with triglyceride (TG), LDL-C, ApoB and iPTH. Both serum TT3 and FT3 levels were significantly positively correlated with HDL-C; and negatively correlated with TG, LDL-C and ApoB.

Conclusions

These data suggest that hyposelenemia in HD patients correlated with euthyroid sick syndrome with low T3 levels, and nutritional status with hyperlipidemia and hypoalbuminemia which might be involved in dysfunction in the endocrine and nutrition metabolism in dialysis patients.

Diminished selenium levels in hemodialysis and continuous ambulatory peritoneal dialysis patients

In this cross-sectional study, selenium (Se) levels in the sera of 35 hemodialysis (HD) patients and 34 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for more than 3 months were compared with the serum Se levels of 34 healthy volunteers. The observed Se levels of 100.8 ± 51.9 µg/L in the sera of the HD patients and of 65.5 ± 32.1 µg/L in the sera of the CAPD patients were significantly lower than the 134.9 ± 81.2 µg/L of the controls, with p = 0.002 and 0.02, respectively. Furthermore, the Se levels were significantly higher in the HD rather than the CAPD patients (p = 0.01). In the spent dialysate effluent fluid of 32 of the CAPD patients Se was undetectable, in the remaining two CAPD patients the Se levels were 1.9 and 4.6μg/l, respectively. The low Se levels of HD and CAPD patients as compared to healthy persons are attributed to diminished Se retention due to chronic oxidative stress.

Low hair selenium and plasma glutathione peroxidase in children with chronic renal failure

Selenium (Se) is a trace element that incorporates into the selenoenzyme glutathione peroxidase (GSH-Px). There are conflicting results regarding the Se levels and activity of GSH-Px in adult uremic patients. The aim of this study was to determine (1) the hair Se status, (2) the possible relation between the hair Se status and the antioxidant enzyme, GSH-Px, and (3) the influence of different treatment procedures on hair Se status and GSH-Px activity in children with CRI, those treated conservatively and those on HD and on CAPD. Ninety-three patients, including 32 patients with CRI, treated conservatively, 42 PD patients, 19 HD patients and 34 healthy children were enrolled in the study. The hair Se level was measured by the atomic absorption spectrophotometer method. Plasma GSH-Px activity was determined using a Randox test combination (RANSEL). Hair Se levels were significantly lower in the CRI, CAPD, and HD groups when compared to the control group (P=0.001, P=0.001, and P=0.001, respectively). Plasma GSH-Px activity was significantly lower in the CRI, CAPD, and HD groups when compared to the control group (P=0.001, P=0.001, and P=0.001, respectively). Plasma GSH-Px activity correlated with the GFR in patients with CRI and the control group (P=0.000; r(2)=0.60). There was no correlation between plasma GSH-Px and hair Se levels in the patient and control groups. These results revealed a decreased hair Se level and impaired antioxidative capacity in children with CRI on CAPD and HD. The lack of any relation between plasma GSH-Px and hair Se suggests that plasma GSH-Px is not a good marker of Se stores.

Sequential changes in plasma selenium concentration after cadaveric renal transplantation

Background

Previous investigations have shown that plasma selenium concentrations are significantly lower in patients with established chronic graft nephropathy (CGN) than in healthy transplant controls. The aims of this study were to determine when in the transplant process low selenium concentrations become apparent and to explore the relationship between selenium levels and risk factors for CGN.

Methods

Plasma selenium concentrations were measured in 40 patients (20 receiving cyclosporin, 20 receiving tacrolimus) undergoing transplantation. Samples were obtained immediately before transplantation and at 3, 6 and 12 months after transplantation.

Results

A low plasma selenium concentration was found in 30 patients at the time of transplantation but this had normalized in the majority of patients by 3 months. Plasma selenium concentrations at 3, 6 and 12 months were significantly higher than baseline values for both treatment arms, but were significantly lower at 3 months in patients who experienced either clinical acute rejection (CAR) or cytomegalovirus (CMV) infection during the preceding months.

Conclusion

Low plasma selenium concentrations are common at the time of transplantation but appear to normalize thereafter. The identification of low selenium levels in patients who experience CAR or CMV (two important risk factors for clinically apparent CGN) suggests that the relationship between selenium and CGN warrants further investigation.