Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Human Ecology

First Advisor

Michael Keenan

Second Advisor

Maren Hegsted


Carnitine supplementation has been shown to protect animals from ammonia toxicity following an ammonium acetate infusion and to alter body composition (i.e. increase lean mass and decrease body fat) in younger animals. The aims of this study were to address the questions of whether: (1) carnitine lowers blood ammonia levels of rats fed high protein; (2) carnitine decreases the weight gain and body fat of older animals fed high fat; (3) carnitine decreases glucose-induced insulin secretion; and (4) consumption of a high fat diet increases total serum carnitine content. Sprague Dawley retired female breeder rats (n = 64) were stratified by weight and randomly assigned to one of the following 8 treatment groups for an 8 week study: carnitine (0%, 0.1%), protein (14%, 35%) and fat (4%, 35%). The study was analyzed as a 2 x 2 x 2 factorial with repeated measures and ANOVA. At 2 and 8 weeks, serum levels of ammonia, urea, glucose, insulin, carnitine, and nonesterified fatty acids were obtained. An oral glucose tolerance test was performed on week 5 and insulin and glucose were measured. Body composition measurements were obtained for all rats at the end of the study. Inclusion of dietary carnitine to rats fed high protein resulted in a trend for lower serum ammonia and significantly lower glucose at 2 but not 8 weeks, with no effect on urea nitrogen levels. Insulin levels for these rats were lower at 2 week, but by 8 week had become higher. Before and after the glucose load was administered insulin levels were significantly higher for these rats. Carnitine did not enhance fatty acid oxidation or increase lean tissue, instead there was a tendency for greater abdominal fat as percent of body weight. We conclude that carnitine's effect on blood ammonia and glucose levels was short-lived and that with time carnitine may lead to weight gain and thus to a loss of insulin sensitivity. Consumption of a high fat diet does not seem to lead to an increase in total serum carnitine content. In addition the benefits of carnitine on body composition are not present in older non-growing animals.