Muscle creatine content in rats given repeated large doses of nicotinamide: effects of dietary methionine, choline, carnitine, and other supplements.

Rats fed a 12% casein diet without added choline were chronically injected with pharmacologic doses of nicotinamide (NAM) for 18 to 28 d in three experiments. In addition to fatty livers and lower weight gains, the creatine content of heart and skeletal muscle was lower in NAM-treated than in control saline-injected rats. Dietary supplements of methionine prevented these alterations, and choline, depending on the level of supplementation, also had some similar effects. No consistent responses could be demonstrated by supplements of carnitine, histidine or folic acid plus vitamin B-12.