Adipose tissue is highly plastic, as illustrated mainly by the transdifferentiation of white adipocytes into beige adipocytes, depending on environmental conditions. However, during gestation and lactation in rodent, there is an amazing phenomenon of transformation of subcutaneous adipose tissue into mammary glandular tissue, known as pink adipose tissue, capable of synthesizing and secreting milk. Recent work using transgenic lineage-tracing experiments, mainly carried out in Saverio Cinti\'s team, has demonstrated very convincingly that this process does indeed correspond to a transdifferentiation of white adipocytes into mammary alveolar cells (pink adipocytes) during gestation and lactation. This phenomenon is reversible, since during the post-lactation phase, pink adipocytes revert to the white adipocyte phenotype. The molecular mechanisms underlying this reversible transdifferentiation remain poorly understood.

Excess adipose tissue is considered one of the main causes of metabolic and cardiovascular diseases. Initially, the adipose tissue was considered the main lipid and energy storage of the organism. Subsequently it was discovered that adipose tissue had other functions such as endocrine, controlling different metabolic and immune processes. Currently, different types of adipose tissue are recognized. The white adipocyte represents the main energy reserve, on the contrary the brown adipocyte is responsible for the oxidation of lipids for thermogenesis. The beige adipocyte originates from the white adipocyte, by a process known as \"browning\", which leads to lipolysis and thermogenesis. The 3 previous types have recently joined the blue adipocyte, which has a role in liver retinoid homeostasis and the pink adipocyte that participates in lactogenesis and is present in the mammary gland of animals; its role is still unknown in humans. The newly identified hormone Irisin is secreted by the skeletal muscle and promotes browning of white to beige adipose tissue, thus favoring thermogenesis. Another interesting aspect of this hormone is that it represents a connection between muscle activity and lipolysis. The above suggests that Irisin may be the key in the prevention and treatment of obesity.
El exceso de tejido adiposo representa una de las principales causas de las enfermedades metabólicas y cardiovasculares. Inicialmente al tejido adiposo se le consideró el almacén de lípidos y energía del organismo. Posteriormente se descubrió que presentaba otras funciones, como la endocrina, controlando diferentes procesos metabólicos e inmunitarios. Por sus características funcionales y estructurales, se reconocen varios tipos de tejido adiposo. El adipocito blanco representa la reserva energética y el adipocito marrón se encarga de la oxidación de los lípidos para la termogénesis. El adipocito beige se origina del adipocito blanco, mediante un proceso que conduce a la lipólisis y la termogénesis. A los anteriores se han sumado el adipocito azul, en el hígado, que interviene en la homeostasis de retinoides, y el adipocito rosa, que participa en la lactogénesis y se ha identificado en la glándula mamaria de animales. La irisina es una hormona secretada principalmente por el músculo esquelético, que promueve el pardeamiento del tejido adiposo blanco a beige, favoreciendo así la termogénesis. Otro aspecto interesante de esta hormona es que representa una conexión entre la actividad muscular y la lipólisis. Por lo anterior, la irisina puede ser una clave en la prevención y el tratamiento de la obesidad.