Barry I. Freedman , M.D. 1 , Carl D. Langefeld , Ph.D. 2 , JoLyn Turner , Ph.D. 1 , 3 , Marina Núñez , M.D., Ph.D. 3 , Kevin P. High , M.D. 3 , Mitzie Spainhour , L.P.N. 1 , Pamela J. Hicks , B.S. 4 , Donald W. Bowden , Ph.D. 4 , Amber M. Reeves-Daniel , D.O. 1 , Mariana Murea , M.D. 1 , Michael V. Rocco , M.D., M.S.C.E. 1 , Jasmin Divers , Ph.D. 2
13 June 2012
Familial aggregation of non-diabetic end stage renal disease (ESRD) is found in African Americans and variants in the apolipoprotein L1 gene ( APOL1) contribute to this risk. To detect genetic associations with milder forms of nephropathy in high-risk families, analyses were performed using generalized estimating equations to assess relationships between kidney disease phenotypes and APOL1 variants in 786 relatives of 470 families. Adjusting for familial correlations, 23.1, 46.7, and 30.2 percent of genotyped relatives possessed two, one, or no APOL1 risk variants, respectively. Relatives with two compared to one or no risk variants had statistically indistinguishable median systolic blood pressure, urine albumin to creatinine ratio, estimated GFR (MDRD equation) and serum cystatin C levels. After adjusting for age, gender, age at ESRD in families, and African ancestry, significant associations were detected between APOL1 with overt proteinuria and estimated GFR (CKD-EPI equation), with a trend toward significance for quantitative albuminuria. Thus, relatives of African Americans with non-diabetic ESRD are enriched for APOL1 risk variants. After adjustment, two APOL1 risk variants weakly predict mild forms of kidney disease. Second hits appear necessary for the initiation of APOL1-associated nephropathy.