Loci that are associated with albuminuria in diabetes mellitus have been identified by GWAS meta-analysis of albuminuria traits in the general population. An association between CUBN and urinary albumin-to-creatinine ratio (UACR) was replicated, and gene-by-diabetes interactions were detected at the HS6ST1 and RAB38/CTSC loci, where a genetic effect on the UACR was found in those with diabetes. Rab38−/− rats had higher urinary albumin concentrations and reduced levels of megalin and cubilin at the proximal tubule cell surface compared to controls, and the expression of RAB38 was higher in the tubuli of patients with diabetic kidney disease than controls.