Donor-derived hypouricemia in irrelevant recipients caused by kidney transplantation

Genotype and Phenotype of Renal Hypouricemia: A Single-Center Study from China

BACKGROUND

Renal hypouricemia (RHUC), a rare inherited disorder characterized by impaired uric acid reabsorption and subsequent profound hypouricemia, occurs mainly due to variants in SLC22A12 or SLC2A9. Only anecdotal cases and one small-scale RHUC screening study have been reported in the Chinese population.

METHODS

A total of 19 patients with RHUC from 17 unrelated families were recruited from our center. The medical history, clinical manifestations, biochemical exam, and clinical outcomes were collected. Next-generation sequencing-based targeted gene sequencing or whole exon sequencing was performed.

RESULTS

A total of 22 variants in SLC22A12 or SLC2A9 were found in 19 patients. The variant c.944G>A (p.W315X) in SLC2A9 was identified in three patients. Three variants c.165C>A (p.D55E), c.1549_1555delGAGACCC (p.E517Rfs*17), and c.1483T>C (p.W495R) in SLC22A12 and three variants c.1215+1G>A (splicing variant), c.643A>C (p.T215P), and c.227C>A (p.S76X) in SLC2A9 were novel. A proportion of 10 out of 19 patients presented with exercise-induced acute kidney injury (EIAKI). The renal outcome was favorable. Five patients had nephrolithiasis, in whom three had hypercalciuria.

CONCLUSION

The current study reported six novel variants in SLC22A12 and SLC2A9 genes of Chinese patients with RHUC. The variant c.944G>A (p.W315X) in SLC2A9 may be common in Chinese patients. EIAKI is the main clinical phenotype associated with RHUC in our cohort, with a favorable outcome. Hypercalciuria presented in some RHUC patients is a new finding.

Assessing the Global Impact on the Mouse Kidney After Traumatic Brain Injury: A Transcriptomic Study

Purpose

In this study, we use animal models combined with bioinformatics strategies to investigate the potential changes in overall renal transcriptional expression after traumatic brain injury.

Methods

Microarray analysis was performed after kidney acquisition using unilateral controlled cortical impact as the primary mouse TBI model. Multi-oriented gene set enrichment analysis was performed for differentially expressed genes.

Results

The results showed that TBI affected the gene set associated with mitochondria function in kidney cells, and a negative enrichment of gene sets associated with immune cell migration and epidermal development was also observed. Analysis of the disease phenotype gene set revealed that differential expression of mitochondria-related genes was associated with lactate metabolism. Alternatively, activation and adhesion of immune cells associated with the complement system may promote autoinflammation in kidney tissue. The simulated immune cell infiltration analysis showed an increase in the proportion of activated memory CD4 T cells and a decrease in the proportion of resting memory CD4 T cells, suggesting that activated memory CD4 T cell infiltration may be involved in the inflammation of renal tissue and cause damage to renal cells, such as principal cells, mesangial cells and loops of Henle cells.

Conclusion

This study is the first to reveal the effects of brain trauma on the kidney. TBI may affect the expression of mitochondria function-related gene sets in renal cells by increasing lactate. It may also affect renal mesangial cells by inducing increased infiltration of immune cells through mechanisms related to complement system activation or autoimmune antibodies.

Renal hypouricemia in a recipient of living-donor kidney transplantation: a case report and literature review

Hypouricemia in kidney transplant (KT) recipients is rare since they usually have subnormal kidney function which raises serum uric acid level. Recently, interests in pathogenesis of hypouricemia have been increasing due to the understanding of the role of uric acid transporter in renal hypouricemia (RHUC). We herein report the case of RHUC consequently developed in a KT recipient from a living donor with RHUC diagnosed by the detailed urinary and genetic test. A 73-year-old Japanese man underwent KT, and the donor was his wife who had hypouricemia [serum uric acid (S-UA) 0.6 mg/dL]. Nine months after KT, the recipient's S-UA was low (1.5 mg/dL) with serum creatinine (S-Cr) of 1.56 mg/dL, and fractional excretion of UA (FEUA) was high (59.7%; normal < 10%), indicating RHUC. Regarding the donor's information, S-Cr, S-UA, and FEUA were 0.95 mg/dL, 1.0 mg/dL, and 54.5%, respectively. To investigate further on the pathogenesis of RHUC in both the recipient and the donor, we performed genetic tests. The donor had a homozygous mutation of W258X in the SLC22A12 gene and the recipient had a wild type of W258X. Finally, we reviewed the previous literature on RHUC among KT recipients and discussed the strategy of follow-up for these patients.