Longitudinal Plasma Metabolome Patterns and Relation to Kidney Function and Proteinuria in Pediatric CKD

Key Points

Longitudinal untargeted metabolomics. Children with CKD have a circulating metabolome that changes over time.

Background

Understanding plasma metabolome patterns in relation to changing kidney function in pediatric CKD is important for continued research for identifying novel biomarkers, characterizing biochemical pathophysiology, and developing targeted interventions. There are a limited number of studies of longitudinal metabolomics and virtually none in pediatric CKD.

Methods

The CKD in Children study is a multi-institutional, prospective cohort that enrolled children aged 6 months to 16 years with eGFR 30–90 ml/min per 1.73 m2. Untargeted metabolomics profiling was performed on plasma samples from the baseline, 2-, and 4-year study visits. There were technologic updates in the metabolomic profiling platform used between the baseline and follow-up assays. Statistical approaches were adopted to avoid direct comparison of baseline and follow-up measurements. To identify metabolite associations with eGFR or urine protein-creatinine ratio (UPCR) among all three time points, we applied linear mixed-effects (LME) models. To identify metabolites associated with time, we applied LME models to the 2- and 4-year follow-up data. We applied linear regression analysis to examine associations between change in metabolite level over time (∆level) and change in eGFR (∆eGFR) and UPCR (∆UPCR). We reported significance on the basis of both the false discovery rate (FDR) <0.05 and P < 0.05.

Results

There were 1156 person-visits (N : baseline=626, 2-year=254, 4-year=276) included. There were 622 metabolites with standardized measurements at all three time points. In LME modeling, 406 and 343 metabolites associated with eGFR and UPCR at FDR <0.05, respectively. Among 530 follow-up person-visits, 158 metabolites showed differences over time at FDR <0.05. For participants with complete data at both follow-up visits (n =123), we report 35 metabolites with ∆level–∆eGFR associations significant at FDR <0.05. There were no metabolites with significant ∆level–∆UPCR associations at FDR <0.05. We report 16 metabolites with ∆level–∆UPCR associations at P < 0.05 and associations with UPCR in LME modeling at FDR <0.05.

Conclusions

We characterized longitudinal plasma metabolomic patterns associated with eGFR and UPCR in a large pediatric CKD population. Many of these metabolite signals have been associated with CKD progression, etiology, and proteinuria in previous CKD Biomarkers Consortium studies. There were also novel metabolite associations with eGFR and proteinuria detected.

Does Vitamin Supplementation Play a Role in Chronic Kidney Disease?

Although the role of vitamins in the human body is proven, guidelines for patients with chronic kidney disease (CKD) remain unclear. This narrative review summarizes the findings of 98 studies of CKD and the effects of vitamin D, B, C, A, E, and K supplementation on patients on dialysis for CKD, with the aim of summarizing the existing guidelines. The findings are promising, showing the potential effectiveness of vitamin supplementation with, for example, vitamins B, D, or C. However, recommendations are still ambiguous, especially in the case of vitamins A and K, due to the potential toxicity associated with higher doses for patients. Continued research is needed to rigorously evaluate the effectiveness and carefully consider the potential risks of some vitamin supplementation for patients with CKD.

Dietary Factors and All-Cause Mortality in Individuals With Type 2 Diabetes: A Systematic Review and Meta-analysis of Prospective Observational Studies

BACKGROUND

Type 2 diabetes is a major health concern associated with mortality. Diet may influence the progression of diabetes; however, systematic reviews are lacking.

PURPOSE

This study systematically summarized the evidence on diet and all-cause mortality in individuals with type 2 diabetes.

DATA SOURCES

PubMed and Web of Science were searched until June 2022.

STUDY SELECTION

Prospective observational studies investigating dietary factors in association with all-cause mortality in individuals with type 2 diabetes were selected.

DATA SYNTHESIS

We identified 107 studies. Moderate certainty of evidence was found for inverse associations of higher intakes of fish (summary risk ratios per serving/week: 0.95; 95% CI 0.92, 0.99; n = 6 studies), whole grain (per 20 g/day: 0.84; 95% CI 0.71, 0.99; n = 2), fiber (per 5 g/day: 0.86; 95% CI 0.81, 0.91; n = 3), and n-3 polyunsaturated fatty acids (per 0.1 g/day: 0.87; 95% CI 0.82, 0.92; n = 2) and mortality. There was low certainty of evidence for inverse associations of vegetable consumption (per 100 g/day: 0.88; 95% CI 0.82, 0.94; n = 2), plant protein (per 10 g/day: 0.91; 95% CI 0.87, 0.96; n = 3), and for positive associations of egg consumption (per 10 g/day: 1.05; 95% CI 1.03, 1.08; n = 7) and cholesterol intake (per 300 mg/day: 1.19; 95% CI 1.13, 1.26; n = 2). For other dietary factors, evidence was uncertain or no association was observed.

CONCLUSIONS

Higher intake of fish, whole grain, fiber, and n-3 polyunsaturated fatty acids were inversely associated with all-cause mortality in individuals with type 2 diabetes. There is limited evidence for other dietary factors, and, thus, more research is needed.

Increased Blood Retinol Levels Are Associated With a Reduced Risk of TIA or Stroke in an Adult Population: Lifestyle Factors- and CVDs-Stratified Analysis

Background: Data on the existing evidence for the association between blood retinol and transient ischemic attack (TIA)/stroke risk are limited, and the results are inconclusive. This study aimed to further assess the associations between the blood retinol levels and the risk of TIA/stroke after controlling the lifestyle factors and age-related confounders. Methods: The cross-sectional data from 1,113 individuals (aged 34-84 years old) were obtained from the Midlife in the United States (MIDUS) study. The multivariable analyses were performed to investigate the association of blood retinol levels with ever and currently TIA/stroke. Results: There was an inverse association between the blood retinol levels and the risk of ever TIA or stroke (for per 1 μmol/L adjusted odds ration [OR]: 0.93; 95% CI: 0.89-0.97; for per 1-SD adjusted OR: 0.89; 95% CI: 0.83-0.96) and currently diagnosed TIA or stroke (for per 1 μmol/L adjusted OR: 0.91; 95% CI: 0.87-0.96; for per 1-SD adjusted OR: 0.84; 95% CI: 0.80-0.91) after controlling the lifestyle factors and age-related confounders. The significance of these associations was maintained after a sensitivity analysis and involving "ever chronic respiratory diseases" as a covariate. Moreover, the stratified analyses suggested that the inverse associations could be affected by overweight [body mass index (BMI) ≥ 28, kg/m²], hypertension, and diabetes. Conclusions: A significant inverse association between blood retinol and the risk of TIA or stroke was found. This inverse association did not change even after adjustment for many potential confounders. Moreover, the potential protective effect of retinol on TIA/stroke could be blunted by overweight [BMI ≥ 28, kg/m²], hypertension, and diabetes.

Association between dietary antioxidant vitamins intake and homocysteine levels in middle-aged and older adults with hypertension: a cross-sectional study

OBJECTIVES

Plasma total homocysteine (tHcy) has been implicated in the development of cardiovascular disease. This study aimed to assess the relationship of dietary antioxidant vitamins intake with tHcy levels in middle-aged and older adults with hypertension.

DESIGN

A cross-sectional study.

SETTING

The survey was conducted in the Nanshan district of Shenzhen.

PARTICIPANTS

A total of 1465 middle-aged and older adults with hypertension were included between July and September of 2013.

MEASUREMENTS

Hyperhomocysteinaemia (HHcy) was defined as tHcy ≥15 µmol/L. Some dietary antioxidant vitamins (vitamin C (VC) and vitamin E (VE), carotenes, retinol, lutein) intake was estimated using the Food Frequency Questionnaire. Sociodemographic and potential covariates were evaluated through questionnaires, anthropometric measurements and blood tests. The association between dietary intakes of antioxidant vitamins and tHcy concentration were evaluated by multiple linear regression analyses after napierian logarithm transformed. Multiple logistic regression models were further used to determine ORs and 95% CIs.

RESULTS

The β (95% CIs) of VC intake and tHcy was -0.050 (-0.084 to -0.016). Compared with the lowest quartile in the fully adjusted model, the ORs (95% CIs) for HHcy levels across quartiles of dietary VC intake were 0.82 (0.57 to 1.16), 0.49 (0.33 to 0.74) and 0.40 (0.22 to 0.74) (p for trend=0.001). The β (95% CIs) of retinol intake and tHcy was -0.021 (-0.041 to -0.002) and the ORs (95% CIs) in the third quartile of retinol intake was 0.61 (0.42 to 0.86), while the effect for the highest quartile was not significant (p for trend=0.951). No significant association was observed between dietary VE, carotenes and lutein intake and HHcy.

CONCLUSIONS

A linear inverse association between dietary VC intake and HHcy prevalence, and an L-shaped association between dietary retinol intake and HHcy prevalence were found in Chinese middle-aged and older adults with hypertension.

Association of Retinol-Binding Protein 4 with Arteriovenous Fistula Dysfunction in Hemodialysis Patients

BACKGROUND

Arteriovenous fistula (AVF) is the most common vascular access for patients undergoing hemodialysis (HD). Neointimal hyperplasia (NIH) might be a potential mechanism of AVF dysfunction. Retinol-binding protein 4 (RBP4) may play an important role in the pathogenesis of NIH. The aim of this study was to investigate whether AVF dysfunction is associated with serum concentrations of RBP4 in HD subjects.

METHODS

A cohort of 65 Chinese patients undergoing maintenance HD was recruited between November 2017 and June 2019. The serum concentrations of RBP4 of each patient were measured with the ELISA method. Multivariate logistic regression was used to analyze data on demographics, biochemical parameters, and serum RBP4 level to predict AVF dysfunction events. The cutoff for serum RBP4 level was derived from the highest score obtained on the Youden index. Survival data were analyzed with the Cox proportional hazards regression analysis and Kaplan-Meier method.

RESULTS

Higher serum RBP4 level was observed in patients with AVF dysfunction compared to those without AVF dysfunction events (174.3 vs. 168.4 mg/L, p = 0.001). The prevalence of AVF dysfunction events was greatly higher among the high RBP4 group (37.5 vs. 4.88%, p = 0.001). In univariate analysis, serum RBP4 level was statistically significantly associated with the risk of AVF dysfunction (OR = 1.015, 95% CI 1.002-1.030, p = 0.030). In multivariate analysis, each 1.0 mg/L increase in RBP4 level was associated with a 1.023-fold-increased risk of AVF dysfunction (95% CI for OR: 1.002-1.045; p = 0.032). The Kaplan-Meier survival analysis indicated that the incidence of AVF dysfunction events in the high RBP4 group was significantly higher than that in the low-RBP4 group (p = 0.0007). Multivariate Cox regressions demonstrated that RBP4 was an independent risk factor for AVF dysfunction events in HD patients (HR = 1.015, 95% CI 1.001-1.028, p = 0.033).

CONCLUSIONS

HD patients with higher serum RBP4 concentrations had a relevant higher incidence of arteriovenous dysfunction events. Serum RBP4 level was an independent risk factor for AVF dysfunction events in HD patients.

Vitamin A regulates fibroblast growth factor 23 (FGF23)

OBJECTIVES

Renal phosphate and vitamin D metabolism are regulated by proteohormone fibroblast growth factor 23 (FGF23), which is secreted by bone cells. FGF23 inhibits phosphate reabsorption and the production of calcitriol, active vitamin D (1,25(OH)₂D₃). FGF23 generated by other cells exerts further paracrine effects in the liver, heart, and immune system. The FGF23 plasma concentration is positively associated with the onset and progression of kidney and cardiovascular diseases, disclosing FGF23 as a potential disease biomarker. The effects of vitamin A on the expression of FGF23 are controversial. Vitamin A components, retinoids, are mainly effective through nuclear retinoic acid receptors (RAR) and exert different effects on bone. The aim of this study was to clarify whether vitamin A modulates the production of FGF23.

METHODS

We studied the relevance of vitamin A for FGF23 production. Fgf23 transcripts were determined by real-time quantitative polymerase chain reaction in UMR106 osteoblast-like cells and IDG-SW3 osteocytes. FGF23 protein in the cell culture supernatant was measured by enzyme-linked immunosorbent assay.

RESULTS

All-trans-retinoic acid, retinyl acetate, RAR agonist TTNPB (4-[(E)-2-(5,6,7,8-Tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid), and 13-cis-retinoic acid downregulated the expression of the Fgf23 gene in a dose-dependent manner. This effect was significantly attenuated by RAR antagonist AGN193109 (4-[2-[5,6-Dihydro-5,5-dimethyl-8-(4-methylphenyl)-2-naphthalenyl]ethynyl]benzoic acid).

CONCLUSION

The present study demonstrated that vitamin A is a potent suppressor of FGF23 production through RAR.

Association between plasma retinol levels and the risk of all-cause mortality in general hypertensive patients: A nested case-control study

To evaluate the association between plasma retinol levels with all-cause mortality and investigate the possible effect modifiers in general hypertensive patients with no previous cardiovascular disease (CVD). This case-control study was nested in the China Stroke Primary Prevention Trial (CSPPT), a randomized, double-blind, controlled trial conducted in 32 communities in Anhui and Jiangsu provinces in China. The current study included 617 cases of all-cause mortality and 617 controls matched on age (≤1 year), sex, treatment group, and study site. All-cause mortality was the main outcome in this analysis, which included death due to any reason. The median follow-up duration was 4.5 years. Overall, there was a U-shaped relation of plasma retinol with all-cause mortality. In the threshold effect analysis, the risk of all-cause mortality significantly decreased with the increase in plasma retinol (per 10 μg/dL increments: OR, 0.73; 95% CI: 0.61-0.87) in participants with plasma retinol <58.3 μg/dL and increased with the increase in plasma retinol (per 10 μg/dL increments: OR, 1.08; 95% CI: 1.01-1.16) in those with plasma retinol ≥58.3 μg/L. In participants with plasma retinol <58.3 μg/dL, a stronger inverse association was observed in those with higher time-averaged SBP (≥140 vs <140 mm Hg; P-interaction = .034), or higher vitamin E levels (≥11.5 [quartile 4]; vs <11.5 μg/mL; P-interaction = .013). The present study demonstrated that there was a U-shaped relationship of plasma retinol levels with the risk of all-cause mortality in general hypertensive patients, with a turning point around 58.3 μg/dL.

Plasma retinol and the risk of first stroke in hypertensive adults: a nested case-control study

Background

Identification of novel risk factors is needed to further lower stroke risk. Data concerning the association between plasma retinol concentrations and the risk of stroke are limited.

Objectives

We aimed to evaluate the effect of plasma retinol on the risk of first stroke and to examine any possible effect modifiers in hypertensive patients.

Methods

The study sample population was drawn from the China Stroke Primary Prevention Trial (CSPPT), using a nested case-control design, including 620 cases with first stroke and 620 matched controls. In the CSPPT, a total of 20,702 hypertensive patients were randomly assigned to a double-blind, daily treatment with either 10 mg enalapril and 0.8 mg folic acid or 10 mg enalapril alone. The median treatment duration was 4.5 y.

Results

There was a significant inverse association between plasma retinol and the risk of first stroke (per 10-μg/dL increment; OR: 0.92; 95% CI: 0.86, 0.97) and first ischemic stroke (OR: 0.92; 95% CI: 0.86, 0.98). When retinol was assessed as quartiles, significantly lower risks of first stroke (OR: 0.64; 95% CI: 0.46, 0.88) and first ischemic stroke (OR: 0.67; 95% CI: 0.46, 0.96) were found in participants in quartiles 2-4 compared with those in quartile 1. Furthermore, a stronger inverse association between plasma retinol and first stroke was observed in participants with baseline total homocysteine (<10 compared with ≥10 μmol/L; P-interaction = 0.049). However, plasma retinol had no significant effect on first hemorrhagic stroke (per 10-μg/dL increment; OR: 0.98; 95% CI: 0.79, 1.18).

Conclusions

Our data showed a significant inverse association between plasma retinol and the risk of first stroke among Chinese hypertensive adults. This study was registered at clinicaltrials.gov as NCT00794885.

Nutritional and Micronutrient Care of Bariatric Surgery Patients: Current Evidence Update

PURPOSE OF REVIEW

The continued success of bariatric surgery to treat obesity and obesity-associated metabolic conditions creates a need for a strong understanding of clinical nutrition both before and after these procedures.

RECENT FINDINGS

Surgically induced alteration of gastrointestinal physiology can affect the nutrition of individuals, especially among those who have undergone malabsorptive procedures. While uncommon, a subset of patients may develop protein-calorie malnutrition. In these cases, nutrition support should be tailored to the severity of malnutrition. Among all patients who undergo bariatric surgery, high rates of micronutrient deficiencies have been observed. To mitigate these deficiencies, empiric supplementation with multivitamins, calcium citrate, and vitamin D is generally recommended. Periodic surveillance should be performed for commonly deficient micronutrients, including thiamin (B1), folate (B9), cobalamin (B12), iron, and vitamin D. Following Roux-en-Y gastric bypass, serum levels of copper and zinc should also be monitored. In addition, lipid-soluble vitamins should be monitored following biliopancreatic diversion with/without duodenal switch.

Plasma Retinol Concentration Is Mainly Driven by Transthyretin in Hemodialysis Patients

OBJECTIVE

Micronutrients deficiencies in hemodialysis patients are due to low dietary intakes and intradialytic losses for hydrophilic micronutrients. Conversely, lipophilic nondialyzable compounds might accumulate because of a lack of elimination through renal metabolism or dialysis. Other compounds have complex metabolism: their concentration is not explained by these phenomenons. The aim of this study was to report plasma concentrations of lipophilic micronutrients in hemodialysis patients and to analyze if these concentrations were predictive of mortality.

DESIGN

The design was monocentric observational longitudinal study.

SUBJECTS

A total of 123 hemodialysis patients included in this observational study.

MAIN OUTCOME MEASURE

Plasma concentration of lipophilic micronutrients retinol and its two co-transporters transthyretin and retinol-binding protein 4, tocopherol, and carotenoids (α-carotene and β-carotene, β-cryptoxanthin, lycopene, lutein, and zeaxanthin), and all factors associated with 1-year mortality.

RESULTS

Within the 123 patients of the study, median age (interquartile range) was 77.5 (69.5-84.5) years and 58.5% were male. Median retinol plasma concentration was 4.07 (2.65-5.51) μmol/L, and 91.9% of patient had high plasma retinol concentrations. In monovariate analysis, retinol levels were inversely correlated with mortality (hazard ratio = 0.57 [0.45-0.72]; P < .001). This effect remained significant after adjustment with several parameters. Nevertheless, the correlation between retinol and mortality disappeared as soon as transthyretin was added in the statistical model, suggesting an effect of transthyretin as confusing bias. Median tocopherol plasma concentration was 34.8 (28.3-42.9) μmol/L and 72.4% of patients had high plasma tocopherol concentration. Neither tocopherol plasma levels nor carotenoids concentrations were correlated with death in multivariate analysis.

CONCLUSIONS

In hemodialysis patients, the correlation between retinol plasma concentration and mortality represents the nutritional status but not a direct biological effect of retinol. Retinol is only a surrogate predictor of mortality. It might not represent vitamin A levels, but likely the transthyretin level. Plasma retinol levels should be interpreted cautiously in hemodialysis patients.

Effects of Acetylsalicylic Acid Usage on Inflammatory and Oxidative Stress Markers in Hemodialysis Patients

The aims of this study were to determine the effects of acetylsalicylic acid (ASA) on inflammation and oxidative stress markers in hemodialysis (HD) patients and to examine the associations between these markers and the sociodemographic and clinical characteristics of participants. The study included 36 subjects who used 300 mg of ASA for 60 days. Inflammation and oxidative stress were assessed based on levels of biochemical markers. ASA usage promoted a decrease in high-sensitivity C-reactive protein (p = 0.01). The level of hydrogen peroxide increased after 30 days of use of ASA and subsequently decreased (p = 0.01). Reduced glutathione reduced at the end of the study (p < 0.01); the malondialdehyde level did not change and the levels of vitamins A and E were inverse to drug use (p = 0.01). ASA usage promoted reduced levels of inflammation, increased production of markers of oxidative stress, and reduced antioxidant defense.

Vitamins (A, C and E) and oxidative status of hemodialysis patients treated with HFR and HFR-Supra

BACKGROUND

Hemodiafiltration with on-line endogenous reinfusion (HFR) is an extracorporeal dialytic method that combines diffusion, convection and adsorption. HFR-Supra (HFR-S) is a second-generation system with increased convective permeability and adsorption capability. Previous studies suggested that HFR reduces oxidative stress compared to standard haemodialysis. The principal aim of the present study was to compare antioxidant vitamins behavior and oxidative status of hemodialysis patients treated with HFR and HFR-S.

METHODS

The study was designed as a multicenter, randomized, crossover trial. Forty-one patients were recruited from 19 dialysis centers and after a 4-month washout stabilization period in on-line hemodiafiltration (ol-HDF), each patient was randomized to a sequence of treatments (HFR-S followed by HFR or viceversa) with each treatment applied over 6 months. Plasma levels of Advanced Oxidation Protein Products, Total Antioxidant Status, vitamins C, A and E and their ligands (Retinol Binding Protein and total lipids) were measured at baseline and at the end of each treatment period.

RESULTS

Results show that the higher convective permeability of HFR-S with respect to HFR did not produce additional beneficial effects on the patients' oxidative status, a slight decrease of both Vitamin A and Retinol Binding Protein being the only difference registered in the long-term. However, as compared to ol-HDF, both the re-infusive techniques allowed to reduce the intradialytic loss of Vitamin C and, in the long-term, improve the patients' oxidative status and increase Retinol Binding Protein plasma values. No significant differences were found between the Vitamin C concentration of pre- and post cartridge UF neither in HFR-S nor in HFR showing that the sorbent resin does not adsorb Vitamin C.

CONCLUSION

HFR-S and HFR are almost equivalent in term of impact on antioxidant vitamins and oxidative status of hemodialysis patients. Nonetheless, as compared to ol-HDF, both treatments produced a sensible sparing of Vitamin C and may represent a new approach for reducing oxidative stress and related complications in dialysis patients. Long-term effects of re-infusive treatments on patients' cardiovascular morbidity and mortality need to be evaluated.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT01492491 , retrospectively registered in 10 December 2011.

Vitamin A: potential misclassification of vitamin A status among patients with type 2 diabetes and hypertension in urban Ghana

BACKGROUND

Sub-Saharan Africa is facing a double burden of malnutrition: vitamin A deficiency (VAD) prevails, whereas the nutrition-related chronic conditions type 2 diabetes (T2D) and hypertension are emerging. Serum retinol—a VAD marker—increases in kidney disease and decreases in inflammation, which can partly be attributed to alterations in the vitamin A-transport proteins retinol-binding protein 4 (RBP4) and prealbumin. Kidney dysfunction and inflammation commonly accompany T2D and hypertension.

OBJECTIVE

Among urban Ghanaians, we investigated the associations of T2D and hypertension with serum retinol as well as the importance of kidney function and inflammation in this regard.

DESIGN

A hospital-based, case-control study in individuals for risk factors of T2D, hypertension, or both was conducted in Kumasi, Ghana (328 controls, 197 with T2D, 354 with hypertension, and 340 with T2D plus hypertension). In 1219 blood samples, serum retinol, RBP4, and prealbumin were measured. Urinary albumin and estimated glomerular filtration rate (eGFR) defined kidney function. C-reactive protein (CRP) >5 mg/L indicated inflammation. We identified associations of T2D and hypertension with retinol by linear regression and calculated the contribution of RBP4, prealbumin, urinary albumin, eGFR, and CRP to these associations as the percentages of the explained variance of retinol.

RESULTS

VAD (retinol <1.05 μmol/L) was present in 10% of this predominantly female, middle-aged, overweight, and deprived population. Hypertension, but not T2D, was positively associated with retinol (β: 0.12; 95% CI: 0.08, 0.17), adjusted for age, sex, socioeconomic factors, anthropometric measurements, and lifestyle. In addition to RBP4 (72%) and prealbumin (22%), the effect of increased retinol on individuals with hypertension was mainly attributed to impaired kidney function (eGFR: 30%; urinary albumin: 5%) but not to inflammation.

CONCLUSIONS

In patients with hypertension, VAD might be underestimated because of increased serum retinol in the context of kidney dysfunction. Thus, the interpretation of serum retinol in sub-Saharan Africa should account for hypertension status.

Hypervitaminosis A is prevalent in children with CKD and contributes to hypercalcemia

BACKGROUND

Vitamin A accumulates in renal failure, but the prevalence of hypervitaminosis A in children with predialysis chronic kidney disease (CKD) is not known. Hypervitaminosis A has been associated with hypercalcemia. In this study we compared dietary vitamin A intake with serum retinoid levels and their associations with hypercalcemia.

METHODS

We studied the relationship between vitamin A intake, serum retinoid levels, and serum calcium in 105 children with CKD stages 2-5 on dialysis and posttransplant. Serum retinoid measures included retinol (ROH), its active retinoic acid (RA) metabolites [all-trans RA (at-RA) and 13-cis RA] and carrier proteins [retinol-binding protein-4 (RBP4) and transthyretin (TTR)]. Dietary vitamin A intake was assessed using a food diary.

RESULTS

Twenty-five children were in CKD 2-3, 35 in CKD 4-5, 23 on dialysis and 22 posttransplant; 53 % had vitamin A intake above the Reference Nutrient Intake (RNI) value. Children receiving supplemental feeds compared with diet alone had higher vitamin A intake (p = 0.02) and higher serum ROH (p < 0.001). Notably, increased ROH was seen as early as CKD stage 2. For every 10 ml/min/1.73 m(2) fall in estimated glomerular filtration rate (eGFR), there was a 13 % increase in ROH. RBP4 levels were increased in CKD 3-5 and dialysis patients. The lowest ratios of ROH:RBP4 were seen in dialysis compared with CKD 2-3 (p = 0.03), suggesting a relative increase in circulating RBP4. Serum ROH, RBP4 and at-RA were associated with serum calcium. On multivariable analysis RBP4 levels and alfacalcidol dose were significant predictors of serum calcium (model R (2) 32 %) in dialysis patients.

CONCLUSIONS

Hypervitaminosis A is seen in early CKD, with highest levels in children on supplemental feeds compared with diet alone. Serum retinoid levels significantly predict hypercalcemia.

Is routine multivitamin supplementation necessary in US chronic adult hemodialysis patients? A systematic review

Because of concern that United States (US) chronic hemodialysis patients are at high risk for the development of vitamin deficiencies, the great majority of such patients are routinely supplemented with a multivitamin. This policy is supported by major US dialysis providers and nonprofit organizations. Yet routine multivitamin supplementation expands hemodialysis patients' already large pill burden, probably accounts for many millions of dollars in annual costs, and in light of previous reports may even carry with it the possibility of increased risk of adverse outcomes. An analysis of the benefits of routine multivitamin supplementation in US patients is therefore in order. We performed a systematic review of the medical literature between 1970 and 2014 using the Ovid MEDLINE database to address this question. We conclude that there is insufficient evidence to support routine multivitamin use and recommend that the decision to supplement be made on an individual basis.