24.5 Sunday, Jan. 4 14:30 A ROLE FOR LEPTIN IN MEDIATING NUTRITION-DEPENDENT REGENERATION RATE IN XENOPUS LAEVIS TITIALII, K*; PARKS, A; CUNDIFF, JA; CRESPI, EJ; Washington State University email@example.com
While much is known about the cellular and molecular mechanisms of limb regeneration, relatively little is known about how the nutritional state of the animal regulates regeneration. We tested the hypothesis that regeneration rate is positively regulated by food intake in Xenopus laevis tadpoles, and the peptide hormone leptin mediates nutrition-dependent limb regeneration rate in developing tadpoles. First, we exposed tadpoles to one of three diets after limb amputation: food restricted, control, and high food. This experiment showed that after 18 d, the food-restricted tadpoles had reduced regeneration area than that of the controls, but the high-food tadpoles did not increase regeneration despite greater body growth. In a second experiment, we injected (ip) tadpoles with recombinant Xenopus leptin or saline at the time of amputation, then exposed them to either food-restricted or control diets for 15 d. Compared to the control diet group, regeneration rates were slower in the food-restricted group, and the development of the uncut limbs was also slower. The area regenerated was enhanced by the leptin treatment in the food-restricted group, but not in the control diet group. Our findings demonstrate that regeneration rate is affected by food intake, but when food is abundant, excess resources are routed toward overall growth. Furthermore, X. laevis tadpoles simultaneously allocate resources to both regeneration and other developmental processes. Given that leptin mRNA expression is positively correlated with nutritional state at this stage of development, the ability of leptin to enhance regeneration in low food conditions suggests that this hormone is a nutritional modulator of limb regeneration.