How do medications that block the renin-angiotensin system (RAS blockers) work to protect against kidney disease in people with diabetes? At least partly by improving the blood supply to the kidneys, suggests a study in the April Journal of the American Society of Nephrology.
Dr. Danilo Fliser and colleagues of Medical School Hannover, Germany, assessed the effects of the RAS-blocking drug olmesartan on blood flow patterns and kidney function in 19 patients with diabetes. Another 19 patients received an inactive placebo. Both groups were treated for 12 weeks.
Olmesartan significantly reduced blood pressure, as expected. At the same time, it also increased the rate of blood flow through the kidneys. The improvement in blood supply was accompanied by a reduction in renovascular resistance, which measures resistance to blood flow in the kidney blood vessels.
In contrast, placebo-treated patients had the opposite pattern: blood flow through the kidneys decreased while renovascular resistance increased slightly. Neither treatment altered the patients' glomerular filtration rate, a standard measure of how efficiently the kidneys are functioning.
Patients receiving olmesartan also had reduced signs of oxidative stress—buildup of unstable, potentially harmful molecules that have previously been linked to cardiovascular disease. This supports recent studies indicating that oxidative stress may contribute to diabetic kidney damage.
Kidney disease (nephropathy) is one of the main complications of type 2 diabetes. In recent years, studies have found that RAS-blocking drugs such as olmesartan can slow the rate of diabetic nephropathy. The new study is one of the first to look at how RAS blockers affect blood flow patterns within the kidneys.