Caloric imbalance, particularly in critical periods of growth and development, is often the underlying cause of growth abnormalities. Serum levels of leptin are elevated in obesity and are low in malnutrition and malabsorption. The aim of the present study was to determine whether leptin integrates energy levels and growth in vivo, as shown previously in our ex vivo experiments, even in the presence of caloric restriction. In the first part of the study, mice were divided into three groups. Two groups were fed ad libitum and received leptin or vehicle only, and the third group was pair-fed with the group injected with leptin to dissociate leptin's effect on growth from its effect on food consumption. Mice given leptin had a significantly greater tibial length than untreated pair-fed animals and a similar tibial length as control mice fed ad libitum despite their lower weight. In addition, leptin significantly increased the overall size of the epiphyseal growth plate by 11%. On immunohistochemistry and in situ hybridization studies, leptin stimulated both the proliferation and differentiation of tibial growth plate chondrocytes without affecting the overall organization of the plate. There was also a marked increase in the expression and level of IGF-IR. In the second part of the study, two groups of mice were fed only 60% of their normal chow; one was injected with leptin, and the other was injected with vehicle alone. Caloric deprivation by itself reduced serum levels of IGF-I by 70% and the length of the tibia by 5%. Leptin treatment corrected the fasting-induced growth deficiency, but further reduced the level of serum IGF-I. These results indicate that leptin stimulates growth even in the presence of caloric restriction independently of peripheral IGF-I.

Malnutrition is considered a leading cause of growth attenuation in children. When food is replenished, spontaneous catch-up (CU) growth usually occurs, bringing the child back to its original growth trajectory. However, in some cases, the CU growth is not complete, leading to a permanent growth deficit. This review summarizes our current knowledge regarding the mechanism regulating nutrition and growth, including systemic factors, such as insulin, growth hormone, insulin- like growth factor-1, vitamin D, fibroblast growth factor-21, etc., and local mechanisms, including autophagy, as well as regulators of transcription, protein synthesis, miRNAs and epigenetics. Studying the molecular mechanisms regulating CU growth may lead to the establishment of better nutritional and therapeutic regimens for more effective CU growth in children with malnutrition and growth abnormalities. It will be fascinating to follow this research in the coming years and to translate the knowledge gained to clinical benefit.

Leptin, first identified as the product of the ob gene in leptin-deficient obese (ob/ob) mice, was originally described as a circulating hormone involved in feeding behavior and energy homeostasis. It was later found to be a pleiotropic hormone involved in the regulation of a variety of physiological processes. This review summarizes our recent understanding of the role of leptin as a linear growth-stimulating factor. Leptin was found to have mitogenic effects on numerous cell types in vivo and in vitro, including several cancer cells, cells of the immune system, as well as chondrocytes of the epiphyseal growth plate. Leptin stimulates linear growth by regulating the energy balance of the organism and by stimulating the production and secretion of growth hormone from the hypothalamus; at the same time, it is involved with bone remodeling and has a direct effect on the chondrocytes of the growth plate.

Central precocious puberty may be familial in about a quarter of the idiopathic cases. However, little is known about the genetic causes responsible for the disorder. In this report we describe a family with central precocious puberty associated with a mutation in the makorin RING-finger protein 3 (MKRN3) gene. A novel missense mutation (p.H420Q) in the imprinted MKRN3 gene was identified in the four affected siblings, in their unaffected father and in his affected mother. An in silico mutant MKRN3 model predicts that the mutation p.H420Q leads to reduced zinc binding and, subsequently, impaired RNA binding. These findings support the fundamental role of the MKRN3 protein in determining pubertal timing.