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

A new perspective on selenium's impact on renal function: European population-based analysis of plasma proteome-mediated Mendelian randomization study

Background

The relationship between selenium and renal function has always attracted widespread attention. Increased selenium level has been found to cause impaired renal function in our previous study, but the mechanism is not clear. In this study, we evaluate the potential mediating effects of plasma proteome in the association of selenium level and renal function to understand the mechanisms of selenium's effect on renal function.

Methods

Utilizing two-sample two-step mediating mendelian randomization (MR) methodology to investigate the genetically causal relationship between selenium level and renal function as well as the role of the plasma proteome in mediating them. Additionally, the mediating proteins were enriched and analyzed through bioinformatics to understand the potential mechanisms of selenium effects on renal function.

Results

In the MR analysis, an increase in selenium level was found to decrease estimated glomerular filtration rate (eGFR). Specifically, for each standard deviation (SD) increase in selenium levels, eGFR levels are reduced by 0.003 SD [Beta (95% CI): -0.003 (-0.004 ~ -0.001), P=0.001, with no observed heterogeneity and pleiotropy]. Through mediation analysis, 35 proteins have been determined mediating the genetically causal effects of selenium on the levels of eGFR, including Fibroblast growth factor receptor 4 (FGFR4), Fibulin-1, Cilia- and flagella-associated protein 45, Mothers against decapentaplegic homolog 2 (SMAD2), and E3 ubiquitin-protein ligase ZNRF3, and the mediation effect rates of these proteins ranged from 1.59% to 23.70%. In the enrichment analysis, 13 signal transduction pathways, including FGFR4 mutant receptor activation and Defective SLC5A5 causing thyroid dyshormonogenesis 1, were involved in the effect of selenium on eGFR levels.

Conclusion

Our finding has revealed the underlying mechanism by which increased selenium level lead to deterioration of renal function, effectively guiding the prevention of chronic kidney disease and paving the way for future studies.

Association between dietary intake of selenium and chronic kidney disease in US adults: a cross-sectional study of NHANES 2015-2018

Background

Chronic kidney disease (CKD) is currently a widespread chronic illness, and its development is influenced by nutrients. Selenium plays a crucial role in the intervention and therapy of various chronic illness. In this study, we aimed to investigate the connection between dietary selenium intake and CKD in adults in the United States.

Methods

We included 6,390 individuals from the datasets of the National Health and Nutrition Examination Survey (NHANES) between 2015 and 2018. We used multiple logistic regression, restricted cubic spline regression, and forest plots to investigate the connection between dietary selenium intake and CKD.

Results

After fully adjusting the data of 6,390 individuals from NHANES between 2015 and 2018, 1,523 (23.83%) of the individuals were identified as having chronic kidney disease (CKD). The rates of CKD in participants with average selenium intakes of ≤0.072, 0.072-0.103, 0.103-0.144, and > 0.144 mg/day were 27.53, 25.11, 22.42, and 19.96%, respectively. After adjusting for potential confounding factors, the fully adjusted odds ratio (OR) values for CKD according to dietary selenium intake were 1 (reference), 0.94 (95% confidence interval (CI): 0.79-1.12, p = 0.466), 0.82 (95% CI:0.68-0.98, p = 0.033), and 0.77 (95% CI:0.63-0.95, p = 0.016) for the four selenium intake levels, respectively, with P trend = 0.007. The dietary selenium intake was negatively associated with the incidence of CKD, after adjusting for other confounding factors. The risk of CKD decreased by 7.7% for every additional 0.1 mg of dietary selenium intake.

Conclusion

A higher dietary selenium intake correlates significantly and negatively with the incidence of CKD.

Effects of Selenium on Chronic Kidney Disease: A Mendelian Randomization Study

BACKGROUND

Previous observational studies have shown that there is a controversial association between selenium levels and chronic kidney disease (CKD). Our aim was to assess the causal relationship between selenium levels and CKD using Mendelian randomization (MR) analysis.

METHODS

We used the two-sample Mendelian randomization (MR) method to analyze the causal role of selenium levels on CKD risk. The variants associated with selenium levels were extracted from a large genome-wide association study (GWAS) meta-analysis of circulating selenium levels (n = 5477) and toenail selenium levels (n = 4162) in the European population. Outcome data were from the largest GWAS meta-analysis of European-ancestry participants for kidney function to date. Inverse variance weighted (IVW) method was used as the main analysis and a series of sensitivity analyses were carried out to detect potential violations of MR assumptions.

RESULTS

The MR analysis results indicate that the genetically predicted selenium levels were associated with decreased estimated glomerular filtration (eGFR) (effect = -0.0042, 95% confidence interval [CI]: -0.0053-0.0031, p = 2.186 × 10^-13) and increased blood urea nitrogen (BUN) (effect = 0.0029, 95% confidence interval [CI]: 0.0006-0.0052, p = 0.0136) with no pleiotropy detected.

CONCLUSIONS

The MR study indicated that an increased level of selenium is a causative factor for kidney function impairment.

COVID-19 and Selenium Deficiency: a Systematic Review

Several studies have indicated that selenium deficiency may be detrimental in the context of various viral disorders, and in the case of COVID-19, several studies have reported heterogeneous results concerning the association of selenium deficiency with the severity of disease. To summarize the available data surrounding the association of body selenium levels with the outcomes of COVID-19, a systematic search was performed in the Medline database (PubMed), Scopus, Cochrane Library, Embase, and Web of Science using keywords including "SARS-CoV-2," "COVID-19," and "selenium," Studies evaluating the association of COVID-19 with body selenium levels were included. Among 1,862 articles viewed in the database search, 10 articles were included after title, abstract, and full-text review. One study was further included after searching the literature again for any newly published articles. Out of 11 included studies, 10 studies measured serum selenium level, and one study investigated urinary selenium level. Three of 10 studies measured serum SELENOP level as well as selenium level. Glutathione peroxidase-3 level in serum was also assessed in one study. The reported outcomes were severity, mortality, and risk of COVID-19. Nine studies indicated that a lower serum selenium level is associated with worse outcomes. Two studies reported no significant association between serum selenium level and COVID-19. In one study, urinary selenium level was reported to be higher in severe and fatal cases compared to non-severe and recovered patients, respectively. In most cases, selenium deficiency was associated with worse outcomes, and selenium levels in COVID-19 patients were lower than in healthy individuals. Thus, it could be concluded that cautious selenium supplementation in COVID-19 patients may be helpful to prevent disease progression. However, randomized clinical trials are needed to confirm this.

Selenium Deficiency-Induced Damage and Altered Expression of Mitochondrial Biogenesis Markers in the Kidneys of Mice

Previous studies have raised concerns that kidney disease is often closely related to low serum Se levels in patients and that hyposelenemia may increase the vulnerability of patients to complications. However, few studies examining renal injury caused by Se deficiency have been conducted. To determine the effects of a selenium-deficient diet on renal function, a mouse model was fed a selenium-deficient diet (0.02 mg Se/kg) for 20 weeks. Meanwhile, mice in the control group (selenium-adequate) were fed a standard diet (0.18 mg Se/kg). The cellular models were established by lentiviral Trnau1ap-shRNA vectors transfected into mouse podocyte (MPC5) and mouse renal tubular epithelial (TCMK1) cell lines. Significant increases in serum creatinine levels and urinary protein/creatinine ratios were accompanied by increased MDA content in the Se-deficient group compared to the control group. The morphological observations of tissues showed widespread inflammation and ultrastructural changes in the Se-deficient group, such as swollen mitochondria and extensive podocyte fusion and renal tubular microvilli shedding. In addition, the expression of COXIV and cytochrome c was significantly downregulated in the Se-deficient group. Importantly, the mRNA levels of silent mating type information regulation 2 homolog 1 (SIRT1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and the protein levels of SIRT1 were increased in the Se-deficient group compared with the normal control group. Our data indicate that Se deficiency induces renal injury in mice. The elevated oxidative stress caused by Se deficiency may result in mitochondrial damage, which might affect renal function. Moreover, the SIRT1/PGC1α axis likely plays an important role in the compensatory mechanism of mitochondrial dysfunction.

microRNA-33-3p involved in selenium deficiency-induced apoptosis via targeting ADAM10 in the chicken kidney

Selenium (Se) deficiency induces typical clinical and pathological changes and causes various pathological responses at the molecular level in several different chicken organs; the kidney is one of the target organs of Se deficiency. To explore the mechanisms that underlie the effects of microRNA-33-3p (miR-33-3p) on Se deficiency-induced kidney apoptosis, 60 chickens were randomly divided into two groups (30 chickens per group). We found that Se deficiency increased the expression of miR-33-3p in the chicken kidney. A disintegrin and metalloprotease domain 10 (ADAM10) was verified to be a target of miR-33-3p in the chicken kidney. The overexpression of miR-33-3p decreased the expression levels of β-catenin, cyclinD1, T-cell factor (TCF), c-myc, survivin, and Bcl-2; it increased the expression levels of E-cadherin, Bak, Bax, and caspase-3; and it increased the number of chicken kidney cells in the G0/G1 phase. In addition, Se deficiency caused the ultrastructure of the kidney to develop apoptotic characteristics. The results of flow cytometry analysis and AO/EB staining showed that the number of apoptotic chicken kidney cells increased in the miR-33-3p mimic group. All these results suggest that Se deficiency-induced cell cycle arrest and apoptosis in vivo and in vitro in the chicken kidney via the regulation of miR-33-3p, which targets ADAM10.

Effects of selenium deficiency on principal indexes of chicken kidney function

Selenium (Se) deficiency leads to many pathological changes in animals. However, there have been very few reports regarding chicken tissue injury in the kidney caused by Se deficiency. In this study, a chicken Se-deficient disease model has been constructed, and two renal function indexes [including creatinine (CREA) and uric acid (URIC)], seven renal antioxidative function indexes [including glutathione peroxidase (GPx), anti-hydroxyl radical (AHR), catalase (CAT), hydrogen peroxide (H2O2), nitrogen monoxide (NO), glutathione (GSH), and malonyldialdehyde (MDA)], and two organ/tissue injury-related indexes [including inducible nitric oxide synthase (iNOS) and inducible heme oxygenase (HO)-1] were detected and analyzed to investigate the effects of Se deficiency on chicken kidney tissue. The results showed that Se deficiency caused a significant increase in CREA and URIC levels and a decrease in renal antioxidative capacity. Meanwhile, Se deficiency upregulated the expression of organ/tissue injury-related genes, such as the messenger RNA (mRNA) of HO-1 and iNOS as well as their protein expression levels, in the chicken kidney tissue. These data suggest that Se deficiency in birds triggers renal function regression and oxidative stress in the kidney tissue.

Selenium and selenium-dependent antioxidants in chronic kidney disease

Oxidative stress plays a key role in numerous disease processes including chronic kidney disease (CKD). In general, oxygen metabolism leads to the formation of reactive oxygen species (ROS) dangerous to cells. Although enzymes and low-molecular-weight antioxidants protect against ROS, chronic imbalances of formation and elimination can eventually overwhelm endogenous defenses leading to deleterious consequences. In CKD, glutathione peroxidases (GSH-Px) play an important role in ROS metabolism. Plasma GSH-Px is synthesized in the kidney and requires selenium (Se) as a cofactor. Interestingly, Se and plasma GSH-Px are both significantly reduced in CKD, especially for those patients on hemodialysis. Supplementation of Se in these patients results in modest increases of GSH-Px, presumably from residual renal tissue. Kidney transplantation rapidly restores plasma GSH-Px. In this chapter, the relevance of these findings to CKD is explored with emphasis on renal disease processes and impact on attendant disorders including cancer and cardiovascular disease.