Objective: To examine the association of renal function in diabetic patients with apolipoprotein (apo) E polymorphism.
Research design and methods: Apo E genotypes, lipid and lipoprotein serum levels, creatinine clearance (CCr), and excretion of marker proteins were determined in German type 1 (IDDM; n = 162) and type 2 (NIDDM; n = 124) diabetic patients. Albumin and immunoglobulin (Ig) G are considered to reflect charge-size permselectivity of the glomerular capillary basement membrane, and increased alpha 1-microglobulin (MG) excretion indicates compromised reabsorptive capacity of the renal tubules.
Results: Patients with NIDDM had higher lipid levels and lower CCrs than patients with IDDM. In patients with IDDM, age- and sex-adjusted analysis of variance showed an association between apo E genotypes and CCr, and the Jonckheere-Terpstra test demonstrated a decreasing glomerular filtration rate in the following order of genotypes: epsilon 4 epsilon 4/epsilon 4 epsilon 3 > epsilon 3 epsilon 3 > epsilon 2 epsilon 2/epsilon 2 epsilon 3. Multiple linear regression analyses revealed that in patients with IDDM, the epsilon 2 allele was a negative predictor of CCr and a positive predictor of urinary excretion of albumin, IgG and alpha 1-MG independent from HDL and LDL cholesterol, TG concentration, age, and sex.
Conclusions: Apo E polymorphism influences serum lipoprotein levels in patients with IDDM and NIDDM. Apo E polymorphism may be a renal risk factor of clinical relevance in normolipidemic patients with IDDM.