Enhanced Dietary Fructose Rapidly Induces Salt‐Sensitive Hypertension in Rats

Abstract

Fructose consumption is associated with increased sodium reabsorption, increased formation of reactive oxygen species, and the development of hypertension. In normal rats, 20% dietary fructose supplementation induces hypertension within 8–12 weeks. We hypothesized a diet combining 20% fructose supplemented with high salt (4% NaCl) would induce abnormal sodium retention, increased oxidative stress, and accelerate the development of elevated blood pressure. Rats weighing 200–225 g were pre‐trained for 2 weeks for non‐invasive tail cuff blood pressure measurements and then placed in metabolic caging. Rats were pair‐fed for 2 weeks with one of 4 different diets: 1) control group (0.4% NaCl), 2) high salt chow group (4% NaCl), 3) 20% fructose group (in the drinking water), and 4) 20% fructose plus high salt group (n's = 9,5,9,18). Blood pressure, urinary sodium excretion and cumulative sodium balance were measured over 2 weeks and urinary 8‐Isoprostane excretion, as a marker for reactive oxygen species, during the final two days. High salt chow replaced normal chow at the beginning of the second week. By the end of the protocol, systolic blood pressure was unchanged in control group (121±2 to 122±2 mmHg) as well as the high salt group (122±2 to 122±1 mmHg). 20% fructose alone had no effect on blood pressure over the 2 weeks (121±1 to 125±1 mmHg). However, blood pressure significantly increased in the 20% fructose plus high salt group (125 to 140 mmHg p<0.001). The increased blood pressure was concomitant with increased positive cumulative sodium balance. During the final week mean urinary sodium excretion in the high salt and 20% fructose plus high salt groups were 5–6 fold higher than normal salt controls (p<0.001): 1.13±0.07, 7.67±0.31, 1.20±0.10, 5.33±0.21 μmol/24 hrs, respectively. Despite similar consumption, urinary sodium excretion in the 20% fructose plus high salt group was significantly lower than the high salt group (p<0.0001). Urinary 8‐Isoprostane excretion was significantly higher in the high salt, 20% fructose, and 20% fructose plus high salt groups compared to control: 16.4±1.3, 29.5±2.5, 32.2±3.9, 31.2±2.5 ng/24 hrs, (p<0.001). Our results suggests enhanced fructose and salt consumption increases sodium retention and oxidative stress. High salt can induce elevations in blood pressure in 20% fructose‐fed rats within just one week. Increased blood pressure appears to associate with increased sodium retention and positive cumulative sodium balance. Overall, fructose combined with high salt in the diet contributes to the accelerated development of salt‐sensitive hypertension.Support or Funding InformationNational Institutes of Health Grant 5P01HL090550‐05