Introduction:
The association "uric acid and high blood pressure" is still matter of debate. Therefore, to distinguish serum uric acid as an independent factor for high blood pressure can start new trials to prevent hypertension. A paleoantropological rationale for this association was a knockout of uricase occurred during the Miocene among hominids that induced high levels of uric acid. As consequence, during food shortage times, high uric acid had an evolutionary benefit increasing salt-sensitivity for keep blood pressure and rising insulin resistance that maintaining high blood glucose levels provided fuel for the brain. Nowadays, the average levels of uric acid are substantially higher compared to chimpanzees, a uricase-deficient primate, and among remote populations as the yanomamo.
Hypothesis:
we assessed the hypothesis that the link between uric acid and blood pressure in individuals without hypertension is independent of sex, age, race, salt and alcohol intakes, glucose homeostasis, body-mass index and renal function.
Methods:
from the 15105 participants of the Brazilian Longitudinal Study for Adult Health (ELSA-Brasil) aged 35-74 years, we selected 7954 individuals (median age = 48 years-old; women =58.1; White = 56.6%) without hypertension, diabetes, previous cardiovascular diseases. The presence or not of prehypertension (7th JNC criteria) was the dependent variable and quartiles (Q) of serum uric acid, the independent variable. We applied an unconditional logistic regression adjusted for age and sex. After this, according to our hypothesis, we added the following variables: (1) 24-hour urinary sodium; (2) log Homeostasis Model Assessment (fasting blood glucose (mg/dL) х fasting insulin (mg/dL)/450), and (3) a full model, adding race, body-mass index, alcohol intake, and glomerular filtration rate by CKD-epi).
Results:
the uric acid quartiles ranges (md/dL) were Q1 ≤ 4.1; Q2:4.2-5.0; Q3:5.1-6.0; Q4: ≥ 6.1 and the number of participants were Q1= 1909; Q2=2029; Q3=2000; Q4= 2016. Considering Q1 as reference, the age-sex adjusted odds ratios (95% Confidence Interval) through the quartiles were: Q2= 1.22 (1.05-1.41); Q3= 1.40 (1.20-1.63); Q4= 2.03 (1.71-2.39) [P for trend <0.001]. Adding 24 hour urinary sodium, the ORs (95% CI) were: Q2= 1.19 (1.01-1.40); Q3= 1.37 (1.16-1.62); and 1.94 (1.61-2.33) [P for trend <0.001]. Adding HOMA-IR, the ORs (95% CI) were: Q2= 1.14 (0.97-1.34); Q3= 1.25(1.05-1.48); and Q4=1.62(1.34-1.96) [P for trend <0.001]. Finally, for the full model the ORs were Q2= 1.04 (0.88-1.23); Q3= 1.05 (0.88-1.26) and Q4= 1.32(1.08-1.62) [P for trend <0. 01].
Conclusion:
Uric acid levels were correlated to prehypertension among a middle-aged urban population. It occurred independently of other variables classically associated to high blood pressure or the origin of higher uric acid in hominids.
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