The effect of vitamin C on parathyroid hormone in patients on hemodialysis with secondary hyperparathyroidism: a double blind, placebo-controlled study

Antioxidants for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular disease (CVD) and death. Increased oxidative stress in people with CKD has been implicated as a potential causative factor. Antioxidant therapy decreases oxidative stress and may consequently reduce cardiovascular morbidity and death in people with CKD. This is an update of a Cochrane review first published in 2012.

OBJECTIVES

To examine the benefits and harms of antioxidant therapy on death and cardiovascular and kidney endpoints in adults with CKD stages 3 to 5, patients undergoing dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies until 15 November 2022 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials investigating the use of antioxidants, compared with placebo, usual or standard care, no treatment, or other antioxidants, for adults with CKD on cardiovascular and kidney endpoints.

DATA COLLECTION AND ANALYSIS

Titles and abstracts were screened independently by two authors who also performed data extraction using standardised forms. Results were pooled using random effects models and expressed as risk ratios (RR) or mean difference (MD) with 95% confidence intervals (CI). Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 95 studies (10,468 randomised patients) that evaluated antioxidant therapy in adults with non-dialysis-dependent CKD (31 studies, 5342 patients), dialysis-dependent CKD (41 studies, 3444 patients) and kidney transplant recipients (21 studies, 1529 patients). Two studies enrolled dialysis and non-dialysis patients (153 patients). Twenty-one studies assessed the effects of vitamin antioxidants, and 74 assessed the effects of non-vitamin antioxidants. Overall, the quality of included studies was moderate to low or very low due to unclear or high risk of bias for randomisation, allocation concealment, blinding, and loss to follow-up. Compared with placebo, usual care, or no treatment, antioxidant therapy may have little or no effect on cardiovascular death (8 studies, 3813 patients: RR 0.94, 95% CI 0.64 to 1.40; I² = 33%; low certainty of evidence) and probably has little to no effect on death (any cause) (45 studies, 7530 patients: RR 0.95, 95% CI 0.82 to 1.11; I² = 0%; moderate certainty of evidence), CVD (16 studies, 4768 patients: RR 0.79, 95% CI 0.63 to 0.99; I² = 23%; moderate certainty of evidence), or loss of kidney transplant (graft loss) (11 studies, 1053 patients: RR 0.88, 95% CI 0.67 to 1.17; I² = 0%; moderate certainty of evidence). Compared with placebo, usual care, or no treatment, antioxidants had little to no effect on the slope of urinary albumin/creatinine ratio (change in UACR) (7 studies, 1286 patients: MD -0.04 mg/mmol, 95% CI -0.55 to 0.47; I² = 37%; very low certainty of evidence) but the evidence is very uncertain. Antioxidants probably reduced the progression to kidney failure (10 studies, 3201 patients: RR 0.65, 95% CI 0.41 to 1.02; I² = 41%; moderate certainty of evidence), may improve the slope of estimated glomerular filtration rate (change in eGFR) (28 studies, 4128 patients: MD 3.65 mL/min/1.73 m², 95% CI 2.81 to 4.50; I² = 99%; low certainty of evidence), but had uncertain effects on the slope of serum creatinine (change in SCr) (16 studies, 3180 patients: MD -13.35 µmol/L, 95% CI -23.49 to -3.23; I² = 98%; very low certainty of evidence). Possible safety concerns are an observed increase in the risk of infection (14 studies, 3697 patients: RR 1.30, 95% CI 1.14 to 1.50; I² = 3%; moderate certainty of evidence) and heart failure (6 studies, 3733 patients: RR 1.40, 95% CI 1.11 to 1.75; I² = 0; moderate certainty of evidence) among antioxidant users. Results of studies with a low risk of bias or longer follow-ups generally were comparable to the main analyses.

AUTHORS' CONCLUSIONS

We found no evidence that antioxidants reduced death or improved kidney transplant outcomes or proteinuria in patients with CKD. Antioxidants likely reduce cardiovascular events and progression to kidney failure and may improve kidney function. Possible concerns are an increased risk of infections and heart failure among antioxidant users. However, most studies were of suboptimal quality and had limited follow-up, and few included people undergoing dialysis or kidney transplant recipients. Furthermore, the large heterogeneity in interventions hampers drawing conclusions on the efficacy and safety of individual agents.

Demand for Water-Soluble Vitamins in a Group of Patients with CKD versus Interventions and Supplementation-A Systematic Review

BACKGROUND

Increasingly, chronic kidney disease (CKD) is becoming an inevitable consequence of obesity, metabolic syndrome, and diabetes. As the disease progresses, and through dialysis, the need for and loss of water-soluble vitamins both increase. This review article looks at the benefits and possible risks of supplementing these vitamins with the treatment of CKD.

METHODS

Data in the PubMed and Embase databases were analyzed. The keywords "chronic kidney disease", in various combinations, are associated with thiamin, riboflavin, pyridoxine, pantothenic acid, folates, niacin, cobalamin, and vitamin C. This review focuses on the possible use of water-soluble vitamin supplementation to improve pharmacological responses and the overall clinical condition of patients.

RESULTS

The mechanism of supportive supplementation is based on reducing oxidative stress, covering the increased demand and losses resulting from the treatment method. In the initial period of failure (G2-G3a), it does not require intervention, but later, especially in the case of inadequate nutrition, the inclusion of supplementation with folate and cobalamin may bring benefits. Such supplementation seems to be a necessity in patients with stage G4 or G5 (uremia). Conversely, the inclusion of additional B6 supplementation to reduce CV risk may be considered. At stage 3b and beyond (stages 4-5), the inclusion of niacin at a dose of 400-1000 mg, depending on the patient's tolerance, is required to lower the phosphate level. The inclusion of supplementation with thiamine and other water-soluble vitamins, especially in peritoneal dialysis and hemodialysis patients, is necessary for reducing dialysis losses. Allowing hemodialysis patients to take low doses of oral vitamin C effectively reduces erythropoietin dose requirements and improves anemia in functional iron-deficient patients. However, it should be considered that doses of B vitamins that are several times higher than the recommended dietary allowance of consumption may exacerbate left ventricular diastolic dysfunction in CKD patients.

CONCLUSIONS

Taking into account the research conducted so far, it seems that the use of vitamin supplementation in CKD patients may have a positive impact on the treatment process and maintaining a disease-free condition.

Uremic leontiasis ossea due to secondary hyperparathyroidism complicated by vitamin C deficiency in a non-adherent chronic hemodialysis patient: A case report

Non-adherence to medical therapy in patients with end-stage kidney disease (ESKD) can lead to severe metabolic derangements rarely seen in the current medical era. Such complications may take the form of secondary hyperparathyroidism (HPT) leading to rare manifestations of bone mineral disease, and profound vitamin C deficiency from poor nutrition combined with removal of water-soluble vitamins during dialysis. Secondary HPT causes renal osteodystrophy which can lead to diffuse enlargement of the facial skeleton and morphological changes suggestive of leontiasis ossea. We report a 36-year-old, non-adherent woman on chronic dialysis for over 10 years who developed progressive, diffuse facial bone enlargement in the context of years of extreme HPT and newly diagnosed severe vitamin C deficiency. Imaging revealed diffuse hypertrophy of the maxillary and mandibular bones. Histopathology showed extensive fibro-osseous proliferation without evidence of Brown tumor, suggestive of uremic leontiasis ossea. In this report, we discuss the orofacial manifestations of secondary HPT and the possible potentiating role of vitamin C deficiency on the development of renal osteodystrophy through altered vitamin D metabolism. Non-adherent patients on chronic dialysis should be evaluated for vitamin C deficiency, and the development of uremic leontiasis ossea should be considered when such patients present with distortion of facial features in the context of severe secondary HPT.

A computer-aided diagnostic system for kidney disease

BACKGROUND

Disease diagnosis is complicated since patients may demonstrate similar symptoms but physician may diagnose different diseases. There are a few number of investigations aimed to create a fuzzy expert system, as a computer aided system for disease diagnosis.

METHODS

In this research, a cross-sectional descriptive study conducted in a kidney clinic in Tehran, Iran in 2012. Medical diagnosis fuzzy rules applied, and a set of symptoms related to the set of considered diseases defined. The input case to be diagnosed defined by assigning a fuzzy value to each symptom and then three physicians asked about each suspected diseases. Then comments of those three physicians summarized for each disease. The fuzzy inference applied to obtain a decision fuzzy set for each disease, and crisp decision values attained to determine the certainty of existence for each disease.

RESULTS

Results indicated that, in the diagnosis of seven cases of kidney disease by examining 21 indicators using fuzzy expert system, kidney stone disease with 63% certainty was the most probable, renal tubular was at the lowest level with 15%, and other kidney diseases were at the other levels. The most remarkable finding of this study was that results of kidney disease diagnosis (e.g., kidney stone) via fuzzy expert system were fully compatible with those of kidney physicians.

CONCLUSION

The proposed fuzzy expert system is a valid, reliable, and flexible instrument to diagnose several typical input cases. The developed system decreases the effort of initial physical checking and manual feeding of input symptoms.

Reporting Quality Assessment of Randomized Controlled Trials Published in Nephrology Urology Monthly Journal

CONTEXT

Randomized controlled trials (RCTs) are important tools for evidence-based health care decisions. It is, therefore, important that they be conducted and reported with the highest possible standards. The aim of this study was to evaluate the reporting quality of the RCTs published in nephrology urology monthly journal and to examine whether there was a change over time in the reporting quality.

EVIDENCE ACQUISITION

The quality of each report was assessed using the Consolidated Standards of Reporting Trials (CONSORT) 2010 Statement checklist and a 5-point quality assessment instrument, i.e. the Jadad scale.

RESULTS

Eighteen (14 Iranian and 4 non-Iranian) RCTs were published from 2012 to 2014 on topics including renal stone (16.6%), hemodialysis and transplantation (38.8%), and prostate conditions (11.1%). Interventions comprised surgery, drugs, and teaching method in 7 (38 %), 10 (55%), and 1 (5%) of them, respectively. According to the CONSORT checklist, the weakest reported items were registration number, identification as a randomized trial in the title, and settings and locations where the data were collected. The mean Jadad score of the reports was 2.72 ± 1.36 (54% of their maximum possible total score). According to the Jadad and CONSORT scales, there was an increase in the quality of reporting from 2012 to 2014.

CONCLUSIONS

This assessment shows low reporting quality scores in reports. Training courses for researchers, using standard reporting tools (e.g. CONSORT 2010 Statement checklist), and consultation with methodologists can improve the quality of published RCTs.

Vitamin C supplementation in patients on maintenance dialysis

As one of the most important water-soluble non-enzymatic antioxidants, vitamin C consists of ascorbic acid and its oxidized form, dehydroascorbic acid. Maintenance hemodialysis (MHD) patients have a generally lower plasma vitamin C level compared with general population. Moreover, dialysis patients also exhibit a low plasma vitamin C level, which is largely related with increased inflammation, refractory anemia and oxidative stress. In this review, we described, in great detail, the vitamin C deficiency in MHD patients and its effects on anti-oxidation, anti-inflammation, pro-oxidation and secondary hyperparathyroidism. In addition, we described the possible potential value of vitamin C in anemia, and the side effects of over-doses of vitamin C supplementation in this particular population. In summary, MHD patients may benefit from vitamin C administration. However, further research should be carried out to confirm its potential beneficial effects, optimal dosage and side effects from vitamin C supplementation.