A high-fructose diet induces insulin resistance but not blood pressure changes in normotensive rats

Rats fed a high-fructose diet represent an animal model for insulin resista nce and hypertension. We recently showed that a high-fructose diet containi ng vegetable oil but a normal sodium/potassium ratio induced mild insulin r esistance with decreased insulin receptor substrate- 1 tyrosine phosphoryla tion in the liver and muscle of normal rats. In the present study, we exami ned the mean blood pressure, serum lipid levels and insulin sensitivity by estimating in vivo insulin activity using the 15-min intravenous insulin to lerance test (ITT, 0.5 ml of 6 mug insulin, iv) followed by calculation of the rate constant for plasma glucose disappearance (K-itt) in male Wistar-H annover rats (110-130 g) randomly divided into four diet groups: control, 1 :3 sodium/potassium ratio (R-Na:K) diet (C 1:3 R-Na:K); control, 1:1 sodium /potassium ratio diet (CNa 1:1 R-Na:K); high-fructose, 1:3 sodium/potassium ratio diet (F 1:3 R-Na:K). and high-fructose, 1:1 sodium/potassium ratio d iet (FNa 1:1 R-Na:K) for 28 days. The change in R-Na:K for the control and high-fructose diets had no effect on insulin sensitivity measured by ITT. I n contrast, the 1:1 R-Na:K increased blood pressure in rats receiving the c ontrol and high-fructose diets from 117 +/- 3 and 118 +/- 3 mmHg to 141 +/- 4 and 132 +/- 4 mmHg (P <0.05), respectively. Triacylglycerol levels were higher in both groups treated with a high-fructose diet when compared to co ntrols (C 1:3 R-Na:K: 1.2 +/- 0.1 mmol/l vs F 1:3 R-Na:K: 2.3 +/- 0.4 mmol/ l and CNa 1: 1 R-Na:K: 1.2 +/- 0.2 mmol/l vs FNa 1:1 R-Na.K: 2.6 +/- 0.4 mm ol/l, P <0.05). These data suggest that fructose alone does not induce hype rinsulinemia or hypertension in rats fed a normal R-Na:K diet, whereas an e levation of sodium in the diet may contribute to the elevated blood pressur e in this animal model.