Leptin modulates fertility under the influence of elevated growth hormone as modeled in oMt1a-oGH transgenic mice

Developmental programming: the role of growth hormone

Developmental programming of the fetus has consequences for physiologic responses in the offspring as an adult and, more recently, is implicated in the expression of altered phenotypes of future generations. Some phenotypes, such as fertility, bone strength, and adiposity are highly relevant to food animal production and in utero factors that impinge on those traits are vital to understand. A key systemic regulatory hormone is growth hormone (GH), which has a developmental role in virtually all tissues and organs. This review catalogs the impact of GH on tissue programming and how perturbations early in development influence GH function.

Cysteine cathepsin S processes leptin, inactivating its biological activity

Leptin is a 16  kDa hormone mainly produced by adipocytes that plays an important role in many biological events including the regulation of appetite and energy balance, atherosclerosis, osteogenesis, angiogenesis, the immune response, and inflammation. The search for proteolytic enzymes capable of processing leptin prompted us to investigate the action of cysteine cathepsins on human leptin degradation. In this study, we observed high cysteine peptidase expression and hydrolytic activity in white adipose tissue (WAT), which was capable of degrading leptin. Considering these results, we investigated whether recombinant human cysteine cathepsins B, K, L, and S were able to degrade human leptin. Mass spectrometry analysis revealed that among the tested enzymes, cathepsin S exhibited the highest catalytic activity on leptin. Furthermore, using a Matrigel assay, we observed that the leptin fragments generated by cathepsin S digestion did not exhibit angiogenic action on endothelial cells and were unable to inhibit food intake in Wistar rats after intracerebroventricular administration. Taken together, these results suggest that cysteine cathepsins may be putative leptin activity regulators in WAT.

Effects of central infusion and immunoneutralization of growth hormone on the timing of puberty and plasma leptin levels in the female rat

Growth hormone (GH) levels increase during puberty though its role in puberty onset is still unclear. An interaction is suggested between GH and leptin, as triggering factor of puberty. To evaluate the role of GH on the timing of puberty and its relation with leptin, we centrally administered recombinant human GH (rhGH; 1 microg/day) to normally fed or food-restricted (FR) prepubertal female rats, and monitored time of vaginal opening (VO). Median time of VO was equally postponed in FR animals and in normally fed rhGH-infused rats: median time of VO was respectively 35 and 34 vs. 27 d. Central infusion of rhGH in FR rats partially restored the delay in VO. Plasma leptin levels were increased in rhGH-infused animals, normally fed or FR. Centrally infused anti-rat GH (0.6 microg/day) did not affect plasma leptin levels, but advanced median time of VO (25 vs. 28 d) in pair-fed female rats but not in ad lib-fed animals. The effects of the centrally infused compounds appear to depend on the dietary regime imposed on the prepubertal animals. Furthermore, plasma leptin levels show no direct or predictive relation to the time of VO. The data indicate an involvement of GH in puberty onset, but do not explain the mechanism employed.