Urinary protein excretion—even in the normal range—raises diabetics' heart risks

Some patients with type 2 diabetes experience kidney problems that cause them to excrete increased amounts of the protein albumin in their urine, a condition called albuminuria. These patients have a considerably higher risk of developing heart problems—such as heart attacks, strokes, and heart failure—than other diabetic patients and people in the general population, who are "normoalbuminuric," with urinary albumin excretion levels of less than 20 μg/min.

Investigators have wondered if any level of albumin excretion—for example at a level that is the upper range of what is considered normal—might increase a diabetic patient's risk of developing heart problems. "It would be important to know whether there is a level for albuminuria that differentiates individuals in need of cardioprotective intervention from those with a low risk," said Giuseppe Remuzzi, MD, FRCP, (Mario Negri Institute for Pharmacological Research and Ospedali Riuniti, in Bergamo, Italy). "This is a major health issue since patients with normoalbuminuria account for at least 90% of the diabetic population," he added.

Through an extension of a clinical trial originally designed for other purposes, Dr. Remuzzi, along with Piero Ruggenenti, MD, Esteban Porrini MD (Mario Negri Institute for Pharmacological Research), and others, evaluated the relationship between albumin excretion levels and heart problems in 1,208 normoalbuminuric patients with type 2 diabetes who were followed for an average of 9.2 years.

The researchers found that any degree of measurable albumin excretion bore significant heart risks:

• For each 1 μg/min in albumin excretion at the start of the study, there was a progressive incremental risk of experiencing heart problems during follow-up.
• Even albuminuria of 1-2 μg/min significantly associated with increased risk compared with albuminuria <1 μg/min.

When the investigators looked only at the subgroup of patients who took antihypertensive drugs called ACE inhibitors from the start of the study and throughout the follow-up period, they found no link between albumin excretion levels and heart risks. This suggests that ACE inhibitors have heart-protective properties that may benefit diabetic patients with albuminuria and normoalbuminuria alike. Future clinical trials are needed to identify levels of albumin excretion above which such cardioprotective therapy is beneficial.

More information: The article, entitled "Measurable Urinary Albumin Predicts Cardiovascular Risk Among Normoalbuminuric Type 2 Diabetics," will appear online on August 30, 2012, doi: 10.1681/ASN.2012030252

Journal reference: Journal of the American Society of Nephrology

Provided by American Society of Nephrology