Lowering hyperuricemia improved endothelial function but failed as an antihypertensive



– Using allopurinol to reduce hyperuricemia in young adults with prehypertension or stage 1 hypertension failed to significantly lower blood pressure but succeeded in significantly improving endothelial function as measured by increased flow-mediated arterial dilation in a single-center crossover study with 82 participants.

The finding of improved endothelial function suggests that reducing hyperuricemia may be a new way to manage hypertension or prevent progression to stage 1 hypertension, improve cardiovascular health, and ultimately cut cardiovascular events, Angelo L. Gaffo, MD, said at the European Congress of Rheumatology. The results indicated that the BP-lowering effect of allopurinol treatment was strongest in people who entered the study with the highest serum urate levels, greater than 6.5 mg/dL, an indication that the next step in developing this approach should be targeting it to people with serum urate levels in this range, said Dr. Gaffo, a rheumatologist at the University of Alabama at Birmingham.

“It’s just a matter of finding the right population to see the blood pressure reduction effect,” Dr. Gaffo said in an interview.

He and his associates designed the SURPHER (Serum Urate Reduction to Prevent Hypertension) study to assess the impact of allopurinol treatment in people aged 18-40 years with prehypertension or stage 1 hypertension as defined by U.S. BP standards at the time they launched the study in 2016 (Contemp Clin Trials. 2016 Sep;50:238-44). Enrolled participants had to be nonsmokers; have an estimated glomerular filtration rate of greater than 60 mL/min per 1.73 m2; have a serum urate level of at least 5.0 mg/dL in men and at least 4.0 mg/dL in women; and be without diabetes, antihypertensive medications, prior urate-lowering treatment, or a history of gout. The 99 people who started the study averaged 28 years old, nearly two-thirds were men, 40% were African Americans, and 52% were white. The participants’ average body mass index was nearly 31 kg/m2, and their average BP was 127/81 mm Hg. Average serum urate levels were 6.4 mg/dL in men and 4.9 mg/dL in women. Participants received 300 mg/day allopurinol or placebo, and after 4 weeks crossed to the alternate regimen, with 82 people completing the full protocol. While on allopurinol, serum urate levels fell by an average of 1.3 mg/dL, a statistically significant drop; on placebo, the levels showed no significant change from baseline.

The primary endpoint was the change in BP on allopurinol treatment, which overall showed no statistically significant difference, compared with when participants received placebo. The results also showed no significant impact of allopurinol treatment, compared with placebo, in serum levels of high-sensitivity C-reactive protein, a measure of inflammation. However, for the secondary endpoint of change in endothelial function as measured by a change in flow-mediated dilation (FMD), the results showed a statistically significant effect of allopurinol treatment. While on allopurinol, average FMD increased from 10.3% at baseline to 14.5% on the drug, a 41% relative increase, while on placebo the average FMD rate showed a slight reduction. Allopurinol treatment was safe and well tolerated during the study.

The results also showed that among people with a baseline serum urate level of greater than 6.5 mg/dL (15 of the 82 study completers) systolic BP fell by an average of about 5 mm Hg.

The results suggested that the concept of reducing hyperuricemia in people with early-stage hypertension or prehypertension might be viable for people with higher serum urate levels than most of those enrolled in SURPHER, Dr. Gaffo said. He noted that prior study results in obese adolescents showed that treating hyperuricemia was able to produce a meaningful BP reduction (Hypertension. 2012 Nov;60[5]:1148-56).

SURPHER received no commercial funding. Dr. Gaffo has received research funding from Amgen and AstraZeneca.

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