“A majority of American adults consume 10 percent or more of total calories from added sugars with a subset taking in more than 25 percent of total calories from added sugars,” said lead author Kevin Gordish, PhD. Because beverages are the most common source of added sugars in the American diet, the research team gave rats drinking water with 20 percent fructose—to simulate excessive human soft-drink consumption—and compared them with rats who received plain water in addition to their food for two weeks. During the second week, the rats receiving 20 percent fructose were also given additional salt in their diets.
“The specific combination of fructose and high salt introduced in the second week rapidly increased blood pressure, resulting in hypertension. Fructose-linked hypertension was associated with increased sodium retention, decreased sodium excretion and diminished factors that help rid the body of excess salt. This observation of fructose-linked hypertension was only seen a diet with fructose and high salt and not a normal salt diet,” Gordish said. “Fructose intake, similar to amounts consumed within the American diet, predisposed normal rats to a rapid onset of salt-sensitive hypertension. Fructose-linked hypertension was unambiguously due to fructose (and not glucose). Further, fructose had distinct deleterious effects in the kidney not seen with the same amount of glucose.”
The results have implications for the U.S. in general and certain ethnic groups such as African Americans, who have a high rate of incidence of salt-sensitive hypertension, in particular. Overall, these findings raise concern about the amount of fructose and salt found in the American diet.
Gordish, a postdoctoral fellow at the Henry Ford Hospital in Detroit, will present “Enhanced Dietary Fructose Rapidly Induces Salt-Sensitive Hypertension in Rats” as part of the poster session “Cross-Talk between Salt and Other Factors in Hypertension” on Tuesday, April 5, from 12:45 to 3 p.m. in the Sails Pavilion of the San Diego Convention Center.
NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact Stacy Brooks at [email protected] or (301) 634-7209.
Full AbstractFructose 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 noninvasive tail cuff blood pressure measurements and then placed in metabolic caging. Rats were pair-fed for 2 weeks with one of 5 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, 5) 20% glucose plus high salt group (n’s = 9,5,9,18, 9). Blood pressure, urinary sodium excretion and cumulative sodium balance were measured over 2 weeks and urinary nitric oxide and 8Isoprostane 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, and 6.12±0.77 mEq/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 8Isoprostane 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). Nitric oxide excretion was impaired in the 20% fructose and high salt group compared to the high salt group and 20% glucose and high salt (p<0.05).
Our results suggest 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.
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