Mild Hyperuricemia Attenuates Salt-Sensitive Hypertension and Kidney Damage

Area of Science:

• Nephrology
• Cardiovascular Research
• Metabolic Diseases

Background:

• Asymptomatic hyperuricemia is linked to adverse kidney and cardiovascular outcomes, but its direct role is debated.
• Dietary sodium intake correlates with uric acid excretion, hinting at hyperuricemia's influence on salt-sensitive hypertension and kidney injury.
• Understanding hyperuricemia's impact is crucial for managing related chronic diseases.

Purpose of the Study:

• To investigate the effects of mild hyperuricemia on salt-sensitive hypertension and kidney damage in a rat model.
• To determine if sex influences the relationship between hyperuricemia, hypertension, and kidney outcomes.
• To explore the underlying mechanisms, including oxidative stress and vasodilatory pathways.

Main Methods:

• Male and female Dahl SS rats were administered a uricase inhibitor (oxonic acid) with a high-salt diet or a high-salt diet alone for three weeks.
• Radiotelemetry, immunohistochemistry, and RNA-Seq were employed to assess hypertension, kidney damage, and gene expression.
• Plasma uric acid levels, uric acid excretion, blood pressure, kidney hypertrophy, oxidative stress markers (8-oxodG), and gene expression profiles were analyzed.

Main Results:

• Oxonic acid significantly increased plasma uric acid in both sexes, but only males showed increased uric acid excretion.
• Mild hyperuricemia attenuated hypertension progression and reduced kidney hypertrophy and protein cast formation in males, but not females.
• Oxonic acid reduced tubular oxidative damage and upregulated vasodilatory pathway genes in male kidneys.

Conclusions:

• Mild hyperuricemia, particularly with hyperuricosuria, mitigated salt-sensitive hypertension and kidney damage in male Dahl SS rats.
• The protective effects were sex-specific, with female rats not exhibiting similar benefits.
• These findings suggest a potential role for managing uric acid levels in specific hypertensive conditions, with consideration for sex differences.