TRIMETHYLLYSINE METABOLISM IN LEAN AND OBESE ZUCKER RATS DURING FASTING

The effect of starvation upon the metabolism of trimethyllysine in lean and obese female Zucker rats was studied. All rats were fed a carnitine and trimethyllysine limiting diet for one to two weeks before starvation was initiated. Fed rats and rats starved for three, six, and nine days were used. Liver free and peptide-linked trimethyllysine, and urine total trimethyllysine were measured. Lean and obese Zucker rats had similar hepatic-free and peptide-linked trimethyllysine content when expressed per g protein or per mg DNA. Obese Zucker rats excreted more total trimethyllysine during starvation relative to lean rats. Starvation did not affect trimethyllysine excretion over time, although there were significant decreases in total carnitine excretion in both lean and obese starved rats. Both phenotypes demonstrated a high efficiency of entry of trimethyllysine into the carnitine biosynthetic pathway. We conclude that lean and obese female Zucker rats, similar to male Spraque-Dawley rats, are extremely efficient in the conversion of trimethyllysine into carnitine.