Leptin is reported to have effects on peripheral tissues that are independent of its centra! effects on food intake and body weight. In this study we examined the chronic effects of leptin injection on some lipid metabolic parameters, glucose handling by the body tissue and glycogen content in liver and skeletal muscles in lean and obese rats. Rats were divided into 2 groups (20 rats each) one group included lean rats and the other included diet induced obesity (DIO) rats. Ten rats of each group were injected intraperitoneal with leptin in a dose of (7.2 ngm/gm/day) for 2 weeks. The other rats served as control groups. In all rats, body weight non estrified fatty acids (NEFA), trigly-cerides (TG), glucose tolerance, muscle and liver glycogen were meas-
ured. Results revealed that, in lean rats, body weight was decreased, with increased serum non-estrified fatty acids (NEFA), without improvement in glucose tolerance, and without change in liver or muscle glycogen content. In obese rats, body weight decreased, serum insulin level decreased, with increased serum NEFA and triglycerides (TG). Improvement in glucose tolerance with decreased liver and muscle glycogen content was observed. These data indicate that leptin induces a complex metabolic responses with effects on glucose as well as lipid metabolism which are independent of central nervous system. It could be concluded that artificial elevation of serum leptin stimulates lipolysis and inhibits glucose storage as glycogen in the liver and skeletal muscles.