Oxytocin Involvement in Body Composition Unveils the True Identity of Oxytocin.

Claudia Camerino

doi:10.3390/ijms22126383

Abstract

The origin of the Oxytocin/Vasopressin system dates back about 600 million years. Oxytocin (Oxt) together with Vasopressin (VP) regulate a diversity of physiological functions that are important for osmoregulation, reproduction, metabolism, and social behavior. Oxt/VP-like peptides have been identified in several invertebrate species and they are functionally related across the entire animal kingdom. Functional conservation enables future exploitation of invertebrate models to study Oxt’s functions not related to pregnancy and the basic mechanisms of central Oxt/VP signaling. Specifically, Oxt is well known for its effects on uteri contractility and milk ejection as well as on metabolism and energy homeostasis. Moreover, the striking evidence that Oxt is linked to energy regulation is that Oxt- and Oxytocin receptor (Oxtr)-deficient mice show late onset obesity. Interestingly Oxt−/− or Oxtr−/− mice develop weight gain without increasing food intake, suggesting that a lack of Oxt reduce metabolic rate. Oxt is expressed in a diversity of skeletal muscle phenotypes and regulates thermogenesis and bone mass. Oxt may increases skeletal muscle tonicity and/or increases body temperature. In this review, the author compared the three most recent theories on the effects of Oxt on body composition.

Highlights

Peptides are employed as messenger molecules in different communication systems involved in the control of physiological processes and behavior [1]
The metabolic role of Oxt diverges in young versus older animals or, alternatively, it takes time to reach full force. This concept was named in our laboratory as “The oxytocin paradox”. This discrepancy can be explained by the fact that Oxt may only mark the identity of neurons projecting from Paraventricular nucleus of the hypothalamus (PVN) but its action is mediated by classical neurotransmitters like GABA, alternatively, Oxt may be anorexigenic in normal mice, but compensatory mechanisms may take place in Oxt−/− or Oxytocin receptor (Oxtr)−/− mice [17,18,19]
In the study of Conte et al [19], the author analyzed the involvement of Oxtr/Transient-receptor-potential-vanilloid-1 (TRPV1) genes in the adaptation of skeletal muscle to cold stress (CS) in mice and found that Oxtr increases in hypothalamus