EFFECTS OF AGING, DIET, AND SEX ON PLASMA-GLUCOSE, FRUCTOSAMINE, AND LIPID CONCENTRATIONS IN BARRIER-RAISED FISCHER 344 RATS

We studied the relationships of plasma glucose, fructosamine, triglyce rides, and cholesterol as a function of age, gender, and diet in barri er-raised Fischer 344 rats aged 5 to 26 months, fed a diet either ad l ibitum or restricted to 60% of the ad libitum caloric intake. The comp lex relationships of these plasma levels to age, gender, and diet led to the development of a model with age, diet, and sex as covariates. O verall, fasting plasma glucose concentrations were reduced by approxim ately 25% in rats on the restricted diet, compared to ad libitum-fed a nimals. There was a significant age-dependent decline in glucose level s in male animals, whereas in females there was an increase in plasma glucose with aging. Plasma fructosamine levels in calorie-restricted a nimals, overall, were reduced by 7% compared to levels in animals fed ad libitum. There was a significant positive correlation between plasm a glucose and fructosamine levels. Mean plasma triglyceride content wa s decreased by 50% in calorie-restricted rats compared to ad libitum-f ed animals. A significant decrease in triglyceride levels with increas ing age was seen in male animals, and an increase with aging in female s. There was a significant positive correlation between plasma glucose and triglyceride levels. Plasma cholesterol levels in calorie-restric ted animals were reduced by 7% compared to levels in ad libitum-fed an imals. An increase of cholesterol concentration with aging was signifi cant in both males and females. Analysis of the data showed that there were significant differences between male and female Fischer 344 rats in the response of plasma glucose and fructosamine to aging and calor ie restriction. Changes of plasma triglyceride and cholesterol with ag ing and dietary calorie restriction were also different in males and f emales. Studies of the effect of aging on glycemia and blood lipid con tent should take into account the contributions of animal sex.