Genetic Variants Associated With Mineral Metabolism Traits in Chronic Kidney Disease

The Intricacies of Renal Phosphate Reabsorption-An Overview

To maintain an optimal body content of phosphorus throughout postnatal life, variable phosphate absorption from food must be finely matched with urinary excretion. This amazing feat is accomplished through synchronised phosphate transport by myriads of ciliated cells lining the renal proximal tubules. These respond in real time to changes in phosphate and composition of the renal filtrate and to hormonal instructions. How they do this has stimulated decades of research. New analytical techniques, coupled with incredible advances in computer technology, have opened new avenues for investigation at a sub-cellular level. There has been a surge of research into different aspects of the process. These have verified long-held beliefs and are also dramatically extending our vision of the intense, integrated, intracellular activity which mediates phosphate absorption. Already, some have indicated new approaches for pharmacological intervention to regulate phosphate in common conditions, including chronic renal failure and osteoporosis, as well as rare inherited biochemical disorders. It is a rapidly evolving field. The aim here is to provide an overview of our current knowledge, to show where it is leading, and where there are uncertainties. Hopefully, this will raise questions and stimulate new ideas for further research.

Multi-trait Analysis of GWAS for circulating FGF23 Identifies Novel Network Interactions Between HRG-HMGB1 and Cardiac Disease in CKD

Background

Genome-wide association studies (GWAS) have identified numerous genetic loci associated with mineral metabolism (MM) markers but have exclusively focused on single-trait analysis. In this study, we performed a multi-trait analysis of GWAS (MTAG) of MM, exploring overlapping genetic architecture between traits, to identify novel genetic associations for fibroblast growth factor 23 (FGF23).

Methods

We applied MTAG to genetic variants common to GWAS of 5 genetically correlated MM markers (calcium, phosphorus, FGF23, 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH)) in European-ancestry subjects. We integrated information from UKBioBank GWAS for blood levels for phosphate, 25(OH)D and calcium (n=366,484), and CHARGE GWAS for PTH (n=29,155) and FGF23 (n=16,624). We then used functional genomics to model interactive and dynamic networks to identify novel associations between genetic traits and circulating FGF23.

Results

MTAG increased the effective sample size for all MM markers to n=50,325 for FGF23. After clumping, MTAG identified independent genome-wide significant SNPs for all traits, including 62 loci for FGF23. Many of these loci have not been previously reported in single-trait analyses. Through functional genomics we identified Histidine-rich glycoprotein (HRG) and high mobility group box 1(HMGB1) genes as master regulators of downstream canonical pathways associated with FGF23. HRG-HMGB1 network interactions were also highly enriched in left ventricular heart tissue of a cohort of deceased hemodialysis patients.

Conclusion

Our findings highlight the importance of MTAG analysis of MM markers to boost the number of genome-wide significant loci for FGF23 to identify novel genetic traits. Functional genomics revealed novel networks that inform unique cellular functions and identified HRG-HMGB1 as key master regulators of FGF23 and cardiovascular disease in CKD. Future studies will provide a deeper understanding of genetic signatures associated with FGF23 and its role in health and disease.

Molecular mechanism of Shengyang Yiwei Decoction in treating chronic kidney disease based on network pharmacology

There is a serious worldwide health problem caused by chronic kidney disease (CKD), yet there are few viable therapies. Therapeutic promise in the treatment of chronic kidney disease (CKD) has been shown by the use of the traditional Chinese herbal compound Shengyang Yiwei Decoction (SYD). However, the chemical processes through which SYD exerts its effects are still unknown. The purpose of this network pharmacology research is to better understand the molecular mechanism of action of Shengyang Yiwei Decoction (SYD) in the treatment of chronic kidney disease (CKD). Traditional Chinese Medicine Systems Pharmacology (TCMSP) was first searched for information on the chemical components of Shengyang Yiwei Decoction. The molecular targets of SYD were then predicted using the Pharm Mapper service. After that, we used databases like DIG-SEE, TTD, and OMIM to zero down on the targets most closely linked to CKD. Cytoscape 3.2.1 was used to generate the component-target network representing SYD's therapy of CKD. In addition, KEGG signal pathways and GO biological processes were analyzed using the DAVID database, and the findings were displayed via OmicShare Tools. Twenty-two active components were isolated from Shengyang Yiwei Decoction, and they were linked to 36 therapeutic targets for CKD in the current investigation. According to the results of the network pharmacology study, 41 signaling pathways are involved in mediating the therapeutic effects of SYD. In addition, SYD's broad therapeutic impact in CKD therapy was shown to include 29 molecular activities, 14 cell components, and 91 biological processes. This research utilizes a multivariate analysis to provide light on the strategies and outcomes of treating CKD using Shengyang Yiwei Decoction. Clinical therapeutic methods for CKD management may benefit greatly from a thorough knowledge of the underlying processes and material foundation of this disease.

Understanding renal phosphate handling: unfinished business

PURPOSE OF REVIEW

The purpose of this review is to highlight the publications from the prior 12-18 months that have contributed significant advances in the field of renal phosphate handling.

RECENT FINDINGS

The discoveries include new mechanisms for the trafficking and expression of the sodium phosphate cotransporters; direct link between phosphate uptake and intracellular metabolic pathways; interdependence between proximal tubule transporters; and the persistent renal expression of phosphate transporters in chronic kidney disease.

SUMMARY

Discovery of new mechanisms for trafficking and regulation of expression of phosphate transporters suggest new targets for the therapy of disorders of phosphate homeostasis. Demonstration of stimulation of glycolysis by phosphate transported into a proximal tubule cell expands the scope of function for the type IIa sodium phosphate transporter from merely a mechanism to reclaim filtered phosphate to a regulator of cell metabolism. This observation opens the door to new therapies for preserving kidney function through alteration in transport. The evidence for persistence of active renal phosphate transport even with chronic kidney disease upends our assumptions of how expression of these transporters is regulated, suggests the possibility of alternative functions for the transporters, and raises the possibility of new therapies for phosphate retention.