Female hormones found to protect against harmful effects of fructose.

2003 FEB 13 - (NewsRx.com & NewsRx.net) -- A number of nutritionists are alarmed by the amount of the public's consumption, as previous research has demonstrated that a fructose diet can lead to insulin resistance and hypertension, particularly in male laboratory animals.

High-fructose corn syrup replaced sucrose (table sugar) as a sweetener in most grocery products some 20 years ago. Today, about 9% of the average dietary energy intake in the U.S. comes from fructose.

Other study results have been uncertain whether elevated blood pressure found in female rats was related to impairments in insulin sensitivity, or if there were any differences between sexes in terms of insulin sensitivity. These findings raised an important question regarding the effects of fructose in female rats, and whether hyperinsulinemia and insulin resistance lead to hypertension as in male rats. Therefore, based on previous research, it has not been possible to discern what role sex plays in the relationship between hyperinsulinemia/insulin resistance and hypertension (if any).

Given the differences in the incidence and cause of cardiovascular disease in men and women, a team of Canadian researchers hypothesized that gender may affect the relationship between hyperinsulinemia/insulin resistance and hypertension. To investigate this hypothesis, they designed experiments to clarify the effect of a high-carbohydrate (fructose) diet in both male and female rats on the development of hyperinsulinemia, insulin resistance, and hypertension. They also examined the role of the sex hormones in the response to a fructose diet in females and examined vascular responses to insulin.

The authors of "Female rats are protected against fructose-induced changes in metabolism and blood pressure," are Denise Galipeau and John H. McNeill, division of pharmacology and toxicology, University of British Columbia, and Subodh Verma at the division of cardiac surgery, the Toronto Hospital (American Journal of Physiology-Heart and Circulatory Physiology, 2002;283(6):H2478-84).

Several experiments were conducted within this study.

Two experimental groups of Wistar rats were used in this study: eight female controls and eight female fructose treated. Pilot groups of male control (M) and fructose-treated (MT) rats were followed at the same time to observe hyperinsulinemia and hypertension but were not included in the statistical analyses. At the age of 6 weeks, treatment groups were started on a diet of 60% fructose for 9 weeks, whereas control groups were maintained on normal laboratory rat chow. Systolic BP was measured before treatment and weekly throughout the study period via the tail-cuff method. Blood samples for determination of 5-hour fasted plasma insulin, glucose, and triglycerides were obtained at study weeks 0, 2, 5, and 7. An oral glucose tolerance test (OGTT) after an overnight fast was performed at study weeks 4 and 8. Glucose was administered orally, and blood samples were collected at the times of 0, 10, 20, 30, and 60 minutes. All blood samples were collected from the tail vein.