Heart and liver lipid fatty acid and behavior changes in mice after a diet change.

Abstract 270-Day old, male Ham/ICR mice were subjected to a diet change from high protein and carbohydrate and low fat to a diet higher in fat and lower in carbohydrate and protein. Age matched mice were maintained on laboratory rodent chow as controls. The diet change was not defined so the observed differences could not necessarily be ascribed to altered protein, carbohydrate, or fat intake. Comparison of the controls with the experimental mice revealed the “junk food” mice differed in lipid fatty acid profiles of the heart and liver and in percentage of lipid palmitic and oleic acids in these organs and also in plasma. Appearance was altered in the experimental mice which had dull, greasy coats. In addition, the experimental animals were less active, slept singly, and were slower in negotiating a three-choice maze than their comparably housed counterparts, indicating altered activity/curiosity behavior. It has been clearly demonstrated that dietary manipulation affects many aspects of body function in animals and humans. For example, nutrition and/or caloric intake affects kidney disease (1), myocardial fibrosis (2), the prevalence of neoplasms (3), learning behavior in rats (4,5), immunological function in mice (6), liver metabolism as exemplified by diet regulated lipogenic activity in rat liver (7–10), morphological effects on the central nervous system (11), and hepatic enzyme activity (12). An intriguing effect of diet is it possible role in aging. Increased longevity in rodents is clearly correlated with certain early diet deprivations (13,2). Rapid growth rate appears to have an adverse effect on longevity, and some typical biochemical changes associated with aging are delayed by a restricted diet. There may also be mesureable biochemical links between diet and quality of life in terms of function. Harmon (14) fed rats from 2 months to senescence (up to 35 months) diets varied in saturated fats. There was no effect on longevity, but the higher the unsaturated fat content in the diet, the worse the performance of the animal in a closed field maze. It was speculated that increased unsaturation in lipid membranes increased suseptibility to free radical damage which affected CNS function. It is not clear why the presumed stimulation of lipid peroxidation by the presence of unsaturated fats did not have an effect on longevity, as one might reasonably assume that the adverse effects on membranes caused by lipid ixidation would promote neoplasms, organs dysfunction, and disease. Body lipids appear to play a role in quality of life and, possibly, aging, particularly in their important role in membrane function. Therefore, it seemed useful to document the response of heart, liver, and plasma lipids to a sudden diet change in a fully mature animal where maturation processes were not a factor. In addition, a “supermarket” diet (15) was used with the idea it would parallel the eating habits of some middle age Americans. The unexpected results of this preliminary study were a marked change in curiosity/activity behavior and a dramatic change in appearance of the mice on the junk food diet. Also found were highly significant increases in specific lipids in the heart and liver as well as in the percent of oleic and palmitic acids in plasma and in some classes of heart and liver lipids.