What do frogs and humans have in common?

Image of Rana dybowski by Pierre Fidenci, via Wikimedia Commons

Leptin is a hormone that signals the brain to suppress appetite in humans. While researchers at the University of Michigan described a similar appetite regulating role for leptin in South African clawed frogs (Xenopus), they also discovered that leptin signals limb development in tadpoles. They suspect that this happens once there are sufficient energy stores to begin the process of metamorphosis. Shalitin and Kiess (2017) also described a role for leptin in skeletal development of children and researchers implicate leptin in early onset of puberty in children who are obese as these children have higher circulating leptin levels and receptors for the hormone are found in ovarian tissue. As such, leptin is thought to play a major role in integrating metabolic and reproductive status in humans.

In contrast to mammals in which the oviduct grows during breeding, the oviduct tissue of Chinese brown frogs (Rana dybowskii) grows in both weight and pipe diameter during pre-hibernation. A new study published in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology presents evidence that leptin may play a role in this growth as levels of the hormone went up in the oviduct during pre-hibernation. The researchers also suspect that leptin may be made locally within the oviduct of the frogs. This is similar to mice as leptin is also present in the oviduct and uterus during early stages of pregnancy.

Sources:

University of Michigan press release

S Shalitin, W Kiess. Putative effects of obesity on linear growth and puberty. Horm Res Paediatr. In press. doi: 10.1159/000455968.

L Xi, Y Liu, Z Tang, X Sheng, H Zhang, Q Weng, M Xu. Expression of Leptin Receptor in the Oviduct of Chinese Brown Frog (Rana dybowskii). American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. In press. DOI: 10.1152/ajpregu.00020.2017