Leptin and tumor growth in rats

We have examined the role of leptin in tumor-induced anorexia in 2 differen t tumor models. In rats bearing the Yoshida AH-130 ascites hepatoma, the re duction in food intake becomes important from day 6 after tumor inoculation . Interestingly, at day 4, when the animals do not show any anorectic behav ior, circulating leptin levels were already reduced. Indeed, in all the tum or-bearing groups studied the levels of leptin were lower than in control a nimals. Moreover, the changes in the circulating levels paralleled changes in adipose tissue leptin mRNA expression, even at:early stages following tu mor inoculation when neither food intake nor fat stores were modified by th e presence of a tumor. Interestingly, 7-day pair-fed controls showed change s similar to those present in tumor-hearing vats. These results agree with previous observations relating fasting to decreased leptin expression, Simi lar results were observed in another tumor model, the mouse Lewis lung carc inoma; i.e., at day 8 after tumor inoculation (when the animals did not sho w anorexia) both the circulating levers and the adipose leptin mRNA express ion were also reduced. Our results suggest that experimental cancer-induced anorexia is not related to leptin changes. (C) 1999 Wiley-Liss, Inc.