Dietary zinc is a key environmental modifier in the progression of IgA nephropathy

Subjective Symptoms and Disease Activity Related to Serum Zinc Concentration in Primary Sjögren's Syndrome

Background/Objectives: We examined the frequency of zinc deficiency in patients with Sjögren's syndrome (SS) and the relationship between zinc deficiency and each of the subjective symptoms and disease activity. Methods: We enrolled 164 patients aged ≥ 20 years with primary SS (pSS) based on the revised diagnostic criteria of the Ministry of Health, Labor and Welfare (1999) and 144 patients with RA diagnosed according to the ACR/EULAR classification criteria for RA (2010) as a comparison group. Subjective symptoms were confirmed using an original questionnaire, and disease activity was determined using the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI). The serum zinc concentrations were measured in both SS and RA patients. Results: The rate of zinc deficiency in the SS group was 26.1%, significantly higher than that in the RA group (7.6%). The rate of zinc deficiency was significantly higher in the pSS group compared with Japanese health checkup recipients reported in the literature. The mean serum zinc concentration in primary SS was 60.6 ± 7.3 µmol/L in the high disease activity group with an ESSDAI of ≥5 points, which was significantly lower than the concentration of 69.7 ± 10.2 µmol/L in patients with an ESSDAI of ≤4 points. Conclusions: The frequency of zinc deficiency was higher in patients with pSS than in patients with RA. Disease activity was also higher in patients with zinc deficiency, suggesting an association between zinc concentration and organ involvement in pSS.

Hydroxychloroquine ameliorates immune functionality and intestinal flora disorders of IgA nephropathy by inhibition of C1GALT1/Cosmc pathway

BACKGROUND

Hydroxychloroquine (HCQ) has emerged as a potential and secure antiproteinuric agent in IgA nephropathy (IgAN). This study endeavored to explore the impact of HCQ on the immune functionality and intestinal flora disorders in IgAN rats, as well as to elucidate the underlying mechanisms through in vivo and in vitro experiments.

METHODS

IgAN model was established in Sprague-Dawley rats through the administration of BSA, LPS, and CCl4, and the IgAN rats received a continuous 8-week treatment with HCQ. Moreover, the human glomerular mesangial cells (HMCs) were incubated with IgA1 to establish an in vitro cellular model of IgAN. At the end of experimental period, samples were collected for further analysis.

RESULTS

HCQ ameliorated the elevated levels of 24hUTP, SCr, BUN, the number of urinary RBC, and the activation of inflammation-related proteins within the TLR4/NF-κB signaling pathway. In the IgAN rat group, there was a pronounced escalation in IgA deposition, mesangial matrix hyperplasia, and glomerular inflammatory cell infiltration, while the administration of HCQ effectively mitigated these pathological changes. In addition, the reduced production of CD4+CD25+Foxp3+ Treg in the IgAN group was effectively reversed by HCQ. Furthermore, HCQ has the capacity to restore the compromised state of the intestinal mucosal barrier induced by IgAN and mitigate the circumstances of intestinal permeability and disruption in the intestinal flora.

CONCLUSION

HCQ diminishes IgA aberrant glycosylation levels, ameliorates renal and intestinal histopathological damage, and attenuates intestinal flora disorders and immune dysfunction in IgAN rats by means of activating the C1GALT1/Cosmc pathway.

The changes and potential effects of zinc homeostasis in periodontitis microenvironment

Zinc is a very important and ubiquitous element, which is present in oral environment, daily diet, oral health products, dental restorative materials, and so on. However, there is a lack of attention to the role of both extracellular or intracellular zinc in the progression of periodontitis and periodontal regeneration. This review summarizes the characteristics of immunological microenvironment and host cells function in several key stages of periodontitis progression, and explores the regulatory effect of zinc during this process. We find multiple evidence indicate that zinc may be involved and play a key role in the stages of immune defense, inflammatory response and bone remodeling. Zinc supplementation in an appropriate dose range or regulation of zinc transport proteins can promote periodontal regeneration by either enhancing immune defense or up-regulating local cells proliferation and differentiation functions. Therefore, zinc homeostasis is essential in periodontal remodeling and regeneration. More attention is suggested to be focused on zinc homeostasis regulation and consider it as a potential strategy in the studies on periodontitis treatment, periodontal-guided tissue regeneration, implant material transformation, and so on.

A Low-Protein, Plant-Dominant Gluten-Free Diet for Immunoglobulin A Nephropathy and Focal Segmental Glomerulosclerosis

Immunoglobulin A nephropathy is the most common glomerulonephritis syndrome in the world, yet there is currently no cure. While blood pressure control, renin-angiotensin-aldosterone system inhibition, and immunosuppression may slow disease progression, low-protein diets, defined as a daily dietary protein intake of 0.6 to 0.8 g/kg body weight, may also decrease immune complex deposition and disease severity, as evidenced in animal models. The link between secondary immunoglobulin A nephropathy and celiac disease has also led to the rise of gluten-free diets and zinc supplementation as potential lifestyle modifications to help manage common immunoglobulin A nephropathy symptoms such as proteinuria and hematuria. In addition, case reports and prospective studies suggest that patients with focal segmental glomerulosclerosis, which manifests as steroid-resistant nephrotic syndrome may also benefit from a gluten-free diet. We highlight the example of a gluten-free, plant-dominant low-protein diet (a different type of low-protein diet that addresses both protein quantity and quality) for patients with immunoglobulin A nephropathy or focal segmental glomerulosclerosis.

Zinc Deficiency, Plasma Fatty Acid Profile and Desaturase Activities in Hemodialysis Patients: Is Supplementation Necessary?

Background: Desaturation and elongation are critical processes in endogenous metabolic fatty acid pathways. Zinc (Zn) is a cofactor for desaturases and elongases enzymes. There is limited evidence regarding the relationships between biomarkers of Zn status, nutritional intake, plasma phospholipid fatty acid profile and clinical outcomes among patients undergoing hemodialysis (HD). Objective: To examine the relationships between dietary and serum levels of Zn and Cu/Zn ratio and to explore associations of these micronutrients with PUFA profile and estimated desaturase and elongase enzyme activities in serum phospholipids among HD patients. Methods: This study included 40 adult patients undergoing hemodialysis treatment. Repeated 24-h recalls were applied for dietary intake assessment. Serum concentration of Zn and Cu were determined using inductively coupled plasma mass spectrometry and fatty acid composition by gas-liquid chromatography. Desaturase and elongase activities were calculated from product-precursor fatty acid ratios. Results: Inadequate dietary Zn intake was found in 55% of HD patients. They all had serum Zn concentration below the reference value of 60 μg/dL (mean 38.8 ± 7.72 μg/dL). Adequate zinc intake was accompanied with significantly higher intake of energy, total fats, SFA, MUFA and proteins. There was no correlation between Zn serum status and Zn intake estimates. Serum Cu/Zn ratio was high, (2.76 ± 0.68), directly and significantly associated with HD period, CRP, BMI, VFA, and inversely with Kt/V, albumin, iron, and iPTH. The n-6/n-3 ratio in plasma phospholipids was elevated (12.25 ± 3.45) and patients with inadequate Zn intake had lower n-3 PUFA intake and status compared to those with adequate intake. Serum Zn concentrations were inversely correlated with linoleic/dihomo-γ-linolenic acid ratio (LA/DGLA) (p = 0.037), related to D6-desaturase activity (p = 0.033) and directly with DGLA relative abundances (p = 0.024). Cu status was inversely associated with EPA level (p = 0.03) and estimates of elongase activity (p = 0.001). Furthermore, positive relationship was found between the Cu/Zn ratio and determined elongase value (p = 0.01). Conclusion: Findings of this study underpin the high prevalence of Zn deficiency and inadequate n-3 PUFA intake and status among subjects undergoing HD. The results obtained indicate that the assessment of Zn status should be a standard parameter of nutritional status screening in HD patients while emphasizing the importance of Cu/Zn determination. Although further research is warranted, Zn and-n-3 PUFA supplementation in HD patients might be beneficial for the prevention and attenuation of adverse health outcomes.

Monozygotic Twins Discordant for Immunoglobulin A Nephropathy Display Differences in DNA Methylation and Gene Expression

Introduction

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis. It involves both genetic and environmental factors, among which DNA methylation, the most studied epigenetic modification, was shown to play a role. Here, we assessed genome-wide DNA methylation and gene expression profiles in 2 pairs of IgAN-discordant monozygotic (MZ) twins, in order to characterize methylation changes and their potential influences on gene expression in IgAN.

Methods

Genome-wide DNA methylation and gene expression profiles were evaluated in peripheral blood mononuclear cells obtained from 2 IgAN-discordant MZ twins. Differentially methylated regions (DMRs) and differentially expressed genes (DEGs) were detected, and an integrated analysis was performed. Finally, functional enrichment analysis was done for DMR-associated genes and DEGs.

Results

Totally 521 DMRs were detected for 2 IgAN-discordant MZ twins. Among them, 9 DMRs were found to be mapped to genes that differentially expressed in 2 MZ twins, indicating the potential regulatory mechanisms of expression for these 9 genes (MNDA, DYSF, IL1R2, TLR6, TREML2, TREM1, IL32, S1PR5, and ADGRE3) in IgAN. Biological process analysis of them showed that they were mostly involved in the immune system process. Functional enrichment analysis of DEGs and DMR-associated genes both identified multiple pathways relevant to inflammatory and immune responses. And DMR-associated genes were significantly enriched in terms related to T-cell function.

Conclusions

Our findings indicate that changes in DNA methylation patterns were involved in the pathogenesis of IgAN. Nine target genes detected in our study may provide new ideas for the exploration of molecular mechanisms of IgAN.

Toll-like Receptors as Potential Therapeutic Targets in Kidney Diseases

Toll-like Receptors (TLRs) are members of pattern recognition receptors and serve a pivotal role in host immunity. TLRs response to pathogen-associated molecular patterns encoded by pathogens or damage-associated molecular patterns released by dying cells, initiating an inflammatory cascade, where both beneficial and detrimental effects can be exerted. Accumulated evidence has revealed that TLRs are closely associated with various kidney diseases but their roles are still not well understood. This review updated evidence on the roles of TLRs in the pathogenesis of kidney diseases including urinary tract infection, glomerulonephritis, acute kidney injury, transplant allograft dysfunction and chronic kidney diseases.

Renal handling of zinc in chronic kidney disease patients and the role of circulating zinc levels in renal function decline

BACKGROUND

Zinc deficiency is commonly encountered in chronic kidney disease (CKD). The aims of this study were to assess whether zinc deficiency was related to increased renal excretion of zinc and to the progression of CKD.

METHODS

Plasma and 24-h urinary zinc levels, urinary electrolytes and uromodulin were measured in 108 CKD patients and 81 individuals without CKD. Serum creatinine values were collected for 3 years to calculate the yearly change in estimated glomerular filtration rate (eGFR). Multivariable regression analysis was performed to assess the association between baseline zinc levels and yearly change in eGFR.

RESULTS

CKD patients had lower circulating zinc levels and higher 24-h urinary zinc excretion than non-CKD participants (612.4 ± 425.9 versus 479.2 ± 293.0 µg/day; P = 0.02). Fractional excretion (FE) of zinc was higher and it significantly increased at more advanced CKD stages. Zinc FE was correlated negatively with 24-h urinary uromodulin excretion (r=-0.29; P < 0.01). Lower baseline plasma zinc levels were associated with a faster yearly decline of renal function in age, gender, diabetes and hypertension adjusted models, but this relationship was no longer significant when baseline eGFR or proteinuria were included.

CONCLUSIONS

Zinc levels are lower in CKD, and not compensated by reduced renal zinc excretion. The inverse association between urinary zinc excretion and uromodulin possibly points to an impaired tubular activity, which could partly account for zinc imbalance in CKD. These data suggest that zinc status is associated with renal function decline, but further studies elucidating the underlying mechanisms and the potential role of zinc supplements in CKD are needed.

A comprehensive mechanistic review insight into the effects of micronutrients on toll-like receptors functions

Toll-like receptors (TLRs) are the special proteins receptors for recognition of molecules related to the pathogens. In this way, TLRs and secreted cytokines as a result of TLRs activation are involved in the inflammation pathways. So far, in vivo and in vitro studies have demonstrated that micronutrients (vitamins & minerals) with a broad range of effects on body health, can regulate TLRs signaling pathways. Current review aimed at determining the possible mechanisms of micronutrient effects on TLRs functions. In the aspect of gene expression, micronutrients have inconsistent effects on mRNA level of TLRs which are dependent on time, dose and type of studied TLR. Also, some micronutrients affect gene expression of TLRs signaling mediators namely TLRs adaptors like Myeloid differentiation primary response 88 (MyD88). In the aspect of TLRs signaling pathways, nuclear factor-κB (NF-κB) is an important mediator which is regulated by micronutrients. Also, the regulatory effects of micronutrients on phosphorylation reactions may be effective in the activation/inactivation of TLRs signaling mediators. In addition, zinc can regulate TLRs signaling indirectly via the zinc finger proteins which have contradictory effects on TLRs cascade. In conclusion, the relationship between micronutrients and TLRs signaling is complicated and depends on some known internal, external and genetic factors like form of studied micronutrient, cell type, TLR agonist, dose and time of exposure, inflammation, apoptosis, cell cycle, and environmental factors. Some unknown factors may be effective in TLRs response and as a result additional mechanistic studies are needed to elucidate exact effect of micronutrients on TLRs signaling.

TLR9 activation induces aberrant IgA glycosylation via APRIL- and IL-6-mediated pathways in IgA nephropathy

Galactose-deficient IgA1 (Gd-IgA1) plays a crucial role in the development of IgA nephropathy (IgAN). However, the pathogenic mechanisms driving Gd-IgA1 production have not been fully elucidated. Innate-immune activation via Toll-like receptor 9 (TLR9) is known to be involved in Gd-IgA1 production. A proliferation inducing ligand (APRIL) and IL-6 are also known to enhance Gd-IgA1 synthesis in IgAN. With this as background, we investigated how TLR9 activation in IgA secreting cells results in overproduction of nephritogenic IgA in the IgAN-prone ddY mouse and in human IgA1-secreting cells. Injection of the TLR9 ligand CpG-oligonucleotides increased production of aberrantly glycosylated IgA and IgG-IgA immune complexes in ddY mice that, in turn, exacerbated kidney injury. CpG-oligonucleotide-stimulated mice had elevated serum levels of APRIL that correlated with those of aberrantly glycosylated IgA and IgG-IgA immune complexes. In vitro, TLR9 activation enhanced production of the nephritogenic IgA as well as APRIL and IL-6 in splenocytes of ddY mice and in human IgA1-secreting cells. However, siRNA knock-down of APRIL completely suppressed overproduction of Gd-IgA1 induced by IL-6. Neutralization of IL-6 decreased CpG-oligonucleotide-induced overproduction of Gd-IgA1. Furthermore, APRIL and IL-6 pathways each independently mediated TLR9-induced overproduction of Gd-IgA1. Thus, TLR9 activation enhanced synthesis of aberrantly glycosylated IgA that, in a mouse model of IgAN, further enhanced kidney injury. Hence, APRIL and IL-6 synergistically, as well as independently, enhance synthesis of Gd-IgA1.

Role of Mesangial-Podocytic-Tubular Cross-Talk in IgA Nephropathy

IgA nephropathy (IgAN), a common primary glomerulonephritis worldwide, is associated with a substantial risk of progression to end-stage renal failure. The disease runs a highly variable clinical course with frequent involvement of tubulointerstitial damage. A subgroup of IgAN with proximal tubular epithelial cells (PTECs) and tubulointerstitial damage often is associated with rapid progression to end-stage renal failure. Human mesangial cell-derived mediators lead to podocyte and tubulointerstitial injury via mesangial-podocytic-tubular cross-talk. Although mesangial-podocytic communication plays a pathogenic role in podocytic injury, the implication of a podocyte-PTEC cross-talk pathway in the progression of tubulointerstitial injury in IgAN should not be underscored. We review the role of mesangial-podocytic-tubular cross-talk in the progression of IgAN. We discuss how podocytopathy in IgAN promotes subsequent PTEC dysfunction and whether tubulointerstitial injury affects the propagation of podocytic injury in IgAN. A thorough understanding of the cross-talk mechanisms among mesangial cells, podocytes, and PTECs may lead to better design of potential therapeutic options for IgAN.

Zinc Inhibits Phosphate-Induced Vascular Calcification through TNFAIP3-Mediated Suppression of NF-κB

Background The high cardiovascular morbidity and mortality of patients with CKD may result in large part from medial vascular calcification, a process promoted by hyperphosphatemia and involving osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Reduced serum zinc levels have frequently been observed in patients with CKD, but the functional relevance of this remains unclear.Methods We performed experiments in primary human aortic VSMCs; klotho-hypomorphic (kl/kl), subtotal nephrectomy, and cholecalciferol-overload mouse calcification models; and serum samples from patients with CKD.Results In cultured VSMCs, treatment with zinc sulfate (ZnSO₄) blunted phosphate-induced calcification, osteo-/chondrogenic signaling, and NF-κB activation. ZnSO₄ increased the abundance of zinc-finger protein TNF-α-induced protein 3 (TNFAIP3, also known as A20), a suppressor of the NF-κB pathway, by zinc-sensing receptor ZnR/GPR39-dependent upregulation of TNFAIP3 gene expression. Silencing of TNFAIP3 in VSMCs blunted the anticalcific effects of ZnSO₄ under high phosphate conditions. kl/kl mice showed reduced plasma zinc levels, and ZnSO₄ supplementation strongly blunted vascular calcification and aortic osteoinduction and upregulated aortic Tnfaip3 expression. ZnSO₄ ameliorated vascular calcification in mice with chronic renal failure and mice with cholecalciferol overload. In patients with CKD, serum zinc concentrations inversely correlated with serum calcification propensity. Finally, ZnSO₄ ameliorated the osteoinductive effects of uremic serum in VSMCs.Conclusions Zinc supplementation ameliorates phosphate-induced osteo-/chondrogenic transdifferentiation of VSMCs and vascular calcification through an active cellular mechanism resulting from GPR39-dependent induction of TNFAIP3 and subsequent suppression of the NF-κB pathway. Zinc supplementation may be a simple treatment to reduce the burden of vascular calcification in CKD.

Toll-Like Receptor 9 Stimulation Induces Aberrant Expression of a Proliferation-Inducing Ligand by Tonsillar Germinal Center B Cells in IgA Nephropathy

The TNF family member a proliferation-inducing ligand (APRIL; also known as TNFSF13), produced by myeloid cells, participates in the generation and survival of antibody-producing plasma cells. We studied the potential role of APRIL in the pathogenesis of IgA nephropathy (IgAN). We found that a significant proportion of germinal centers (GCs) in tonsils of patients with IgAN contained cells aberrantly producing APRIL, contributing to an overall upregulation of tonsillar APRIL expression compared with that in tonsils of control patients with tonsillitis. In IgAN GC, antigen-experienced IgD^-CD38^+/-CD19⁺ B cells expressing a switched IgG/IgA B cell receptor produced APRIL. Notably, these GC B cells expressed mRNA encoding the common cleavable APRIL-α but also, the less frequent APRIL-δ/ζ mRNA, which encodes a protein that lacks a furin cleavage site and is, thus, the uncleavable membrane-bound form. Significant correlation between TLR9 and APRIL expression levels existed in tonsils from patients with IgAN. In vitro, repeated TLR9 stimulation induced APRIL expression in tonsillar B cells from control patients with tonsillitis. Clinically, aberrant APRIL expression in tonsillar GC correlated with greater proteinuria, and patients with IgAN and aberrant APRIL overexpression in tonsillar GC responded well to tonsillectomy, with parallel decreases in serum levels of galactose-deficient IgA1. Taken together, our data indicate that antibody disorders in IgAN associate with TLR9-induced aberrant expression of APRIL in tonsillar GC B cells.

The kinetics of glomerular deposition of nephritogenic IgA

Whether IgA nephropathy is attributable to mesangial IgA is unclear as there is no correlation between intensity of deposits and extent of glomerular injury and no clear mechanism explaining how these mesangial deposits induce hematuria and subsequent proteinuria. This hinders the development of a specific therapy. Thus, precise events during deposition still remain clinical challenge to clarify. Since no study assessed induction of IgA nephropathy by nephritogenic IgA, we analyzed sequential events involving nephritogenic IgA from IgA nephropathy-prone mice by real-time imaging systems. Immunofluorescence and electron microscopy showed that serum IgA from susceptible mice had strong affinity to mesangial, subepithelial, and subendothelial lesions, with effacement/actin aggregation in podocytes and arcade formation in endothelial cells. The deposits disappeared 24-h after single IgA injection. The data were supported by a fluorescence molecular tomography system and real-time and 3D in vivo imaging. In vivo imaging showed that IgA from the susceptible mice began depositing along the glomerular capillary from 1 min and accumulated until 2-h on the first stick in a focal and segmental manner. The findings indicate that glomerular IgA depositions in IgAN may be expressed under the balance between deposition and clearance. Since nephritogenic IgA showed mesangial as well as focal and segmental deposition along the capillary with acute cellular activation, all glomerular cellular elements are a plausible target for injury such as hematuria.