American Journal of Clinical Nutrition, Vol 66, 1428-1435, Copyright © 1997 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Sex differences in response to dietary manipulation in rats with hypertension and myocardial hypertrophy

C Wittnich and WJ Wallen
Department of Physiology, University of Toronto, Canada. c.wittnich@utoronto.ca

Studies of the effect of sex on the metabolic state of rats with chronic hypertension and concomitant myocardial hypertrophy were conducted. Female and male spontaneously hypertensive rats (SHRs) with early myocardial hypertrophy (5.5 mo old) were used. Serum fatty acids, liver glycogen, and myocardial glycogen were measured at baseline and after the rats were deprived of food for 24 h. The metabolic effects of progressive myocardial hypertrophy in females were assessed in additional groups of female SHRs (5.5 or 12 mo old) under the following conditions: control, food deprived, or food deprived and refed with equienergetic lipid-rich (38.9% of total energy) or carbohydrate-rich (76.5% of total energy) diets. Despite no differences in serum fatty acids, females had significantly higher baseline myocardial glycogen and liver glycogen concentrations than males. In response to food deprivation, females continued to have significantly higher myocardial glycogen and fatty acid concentrations than males, whereas there were no sex differences in liver glycogen, which was depleted in both males and females. Older hypertensive females had higher baseline fatty acid concentrations and lower liver glycogen concentrations than younger females, whereas there were no differences in myocardial glycogen. Food deprivation doubled fatty acid concentrations, depleted liver glycogen, and increased myocardial glycogen in both age groups. In both age groups, fatty acid concentrations and liver glycogen did not return to baseline values after food deprivation and refeeding. In both age groups, fatty acid concentrations increased further after the lipid- rich diet whereas liver glycogen concentrations returned to approximately 50% of baseline values after the carbohydrate-rich diet. Refeeding with either diet did not significantly increase myocardial glycogen further. Thus, the metabolic response to dietary manipulation was influenced by both sex and, in females, progressive pathology.