Adolescent development is not only shaped by the mere passing of time and accumulating experience, but it also depends on pubertal timing and the cascade of maturational processes orchestrated by gonadal hormones. Although individual variability in puberty onset confounds adolescent studies, it has not been efficiently controlled for. Here we introduce ultrasonic bone age assessment to estimate biological maturity and disentangle the independent effects of chronological and biological age on adolescent cognitive abilities, emotional development, and brain maturation. Comparing cognitive performance of participants with different skeletal maturity we uncover the impact of biological age on both IQ and specific abilities. With respect to emotional development, we find narrow windows of highest vulnerability determined by biological age. In terms of neural development, we focus on the relevance of neural states unrelated to sensory stimulation, such as cortical activity during sleep and resting states, and we uncover a novel anterior-to-posterior pattern of human brain maturation. Based on our findings, bone age is a promising biomarker of adolescent maturity.

Puberty is a brain-driven phenomenon, which is under the control of sophisticated regulatory networks that integrate a large number of endogenous and environmental signals, including metabolic and nutritional cues. Puberty onset is tightly bound to the state of body energy reserves, and deregulation of energy/metabolic homeostasis is often associated with alterations in the timing of puberty. However, despite recent progress in the field, our knowledge of the specific molecular mechanisms and pathways whereby our brain decode metabolic information to modulate puberty onset remains fragmentary and incomplete. Compelling evidence, gathered over the last fifteen years, supports an essential role of hypothalamic neurons producing kisspeptins, encoded by Kiss1, in the neuroendocrine control of puberty. Kiss1 neurons are major components of the hypothalamic GnRH pulse generator, whose full activation is mandatory pubertal onset. Kiss1 neurons seemingly participate in transmitting the regulatory actions of metabolic cues on pubertal maturation. However, the modulatory influence of metabolic signals (e.g., leptin) on Kiss1 neurons might be predominantly indirect and likely involves also the interaction with other transmitters and neuronal populations. In my presentation, I will review herein recent work of our group, using preclinical models, addressing the molecular mechanisms whereby Kiss1 neurons are modulated by metabolic signals, and thereby contribute to the nutritional control of puberty. In this context, the putative roles of the energy/metabolic sensors, AMP-activated protein kinase (AMPK) and SIRT1, in the metabolic control of Kiss1 neurons and puberty will be discussed. In addition, I will summarize recent findings from our team pointing out a role of central de novo ceramide signaling in mediating the impact of obesity of (earlier) puberty onset, via non-canonical, kisspeptin-related pathways. These findings are posed of translational interest, as perturbations of these molecular pathways could contribute to the alterations of pubertal timing linked to conditions of metabolic stress in humans, ranging from malnutrition to obesity, and might become druggable targets for better management of pubertal disorders.