"Biomarking" the transition from genetic risk to kidney disease

APOL1 nephropathy - a population genetics success story

PURPOSE OF REVIEW

More than a decade ago, apolipoprotein L1 ( APOL1 ) risk alleles designated G1 and G2, were discovered to be causally associated with markedly increased risk for progressive kidney disease in individuals of recent African ancestry. Gratifying progress has been made during the intervening years, extending to the development and clinical testing of genomically precise small molecule therapy accompanied by emergence of RNA medicine platforms and clinical testing within just over a decade.

RECENT FINDINGS

Given the plethora of excellent prior review articles, we will focus on new findings regarding unresolved questions relating mechanism of cell injury with mode of inheritance, regulation and modulation of APOL1 activity, modifiers and triggers for APOL1 kidney risk penetrance, the pleiotropic spectrum of APOL1 related disease beyond the kidney - all within the context of relevance to therapeutic advances.

SUMMARY

Notwithstanding remaining controversies and uncertainties, promising genomically precise therapies targeted at APOL1 mRNA using antisense oligonucleotides (ASO), inhibitors of APOL1 expression, and small molecules that specifically bind and inhibit APOL1 cation flux are emerging, many already at the clinical trial stage. These therapies hold great promise for mitigating APOL1 kidney injury and possibly other systemic phenotypes as well. A challenge will be to develop guidelines for appropriate use in susceptible individuals who will derive the greatest benefit.

JC Viruria Is Associated With Reduced Risk of Diabetic Kidney Disease

PURPOSE

African Americans who shed JC polyomavirus (JCV) in their urine have reduced rates of nondiabetic chronic kidney disease (CKD). We assessed the associations between urinary JCV and urine BK polyomavirus (BKV) with CKD in African Americans with diabetes mellitus.

METHODS

African Americans with diabetic kidney disease (DKD) and controls lacking nephropathy from the Family Investigation of Nephropathy and Diabetes Consortium (FIND) and African American-Diabetes Heart Study (AA-DHS) had urine tested for JCV and BKV using quantitative PCR. Of the 335 individuals tested, 148 had DKD and 187 were controls.

RESULTS

JCV viruria was detected more often in the controls than in the patients with DKD (FIND: 46.6% vs 32.2%; OR, 0.52; 95% CI, 0.29 to 0.93; P = 0.03; AA-DHS: 30.4% vs 26.2%; OR, 0.63; 95% CI, 0.27 to 1.48; P = 0.29). A joint analysis adjusted for age, sex, and study revealed that JC viruria was inversely associated with DKD (OR, 0.56; 95% CI, 0.35 to 0.91; P = 0.02). Statistically significant relationships between BKV and DKD were not observed.

MAIN CONCLUSIONS

The results from the present study extend the inverse association between urine JCV and nondiabetic nephropathy in African Americans to DKD. These results imply that common pathways likely involving the innate immune system mediate coincident chronic kidney injury and restriction of JCV replication. Future studies are needed to explore causative pathways and characterize whether the absence of JC viruria can serve as a biomarker for DKD in the African American population.