Proteinuria Indicates Heart Disease Risk in Whites, But Not in Blacks

The cardiovascular risk of atherosclerosis associated with proteinuria--high levels of albumin in the urine--has race-dependent effects, according to a new study.

Researchers at Wake Forest University (WFU; Winston-Salem, NC, USA) evaluated whether excess protein excretion in the urine, a major heart disease risk factor in whites, was also a risk factor for heart and vascular disease in blacks. To do so, the level of urine protein was examined in 835 white participants (mean age 61.7 years) and 393 black (mean age 56.7 years) participants, all with diabetes for approximately 10 years. Participants were also tested for atherosclerosis, based on the buildup of calcium in their major arteries.

The researchers found that in African American and European American participants, respectively, median calcified plaque mass scores were 53.5 and 291 for the coronary artery, 3 and 35.5 for the carotid artery, and 761 and 3,237 for the aorta. With adjustment for age, sex, glomerular filtration rate (GFR), and body mass index (BMI), proteinuria was significantly associated with calcified plaque in European Americans but not in African Americans, with significant ethnic interaction. Ethnic differences in this relationship persisted after adjustment for blood pressure, smoking, lipids, and use of acetylcholine-esterase (ACE) inhibitors or angiotensin receptor blockers. The study was published in the January 2010 issue of Diabetes Care.

"Excess protein in the urine, a common finding with progressive kidney disease in individuals with diabetes, is strongly associated with calcium deposition in the major arteries in white patients, but not in black patients,” said lead author Barry Freedman, M.D., chief of the section on nephrology at the WFU School of Medicine. "In the medical community, it is believed that the more protein in a patient's urine, the greater the risk for heart disease and stroke, and this is true - in white populations. There may be biologic factors predisposing whites to heart disease or protecting blacks from developing it.”

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