‘Peripuberty’ is a phase in which every person’s body undergoes when childhood ends, and adolescence begins. In this phase, every individual goes through developmental changes in fat tissues and the brain.
Exposure to stress can reprogramme both changes and has long-lasting changes in the size of fat cells (adipocytes), size and composition, and social behavior.
A new study by EPFL scientists investigates the molecular mechanisms whereby the increase in adiposity induced by peripubertal stress triggers long-lasting changes in social behavior. Previous studies have shown this connection, but there has been little in identifying a biological link between the increase of adipose tissue seen in peripuberty and social impairment.
Scientists in this study found a biological connection. It explains why there is an increased predisposition to develop obesity and being less sociable in individuals that have experienced stress during early puberty.
They found that stress during the peripubertal period leads to an increase in adipose tissue in the individual’s body. In addition, they uncovered: 1. Peripubertal pressure can increase adipose tissue and reduce sociability at the same time. 2. How the two changes phenomena are biologically related.
Scientists determine if alterations in stress-induced fat composition could prompt changes in the brain that, ultimately, would cause alterations in social behavior in a protracted manner.
For this study, the mice model was used to study peripubertal stress. Scientists exposed mice to chronic, unpredictable stress. An analysis of their body composition revealed an overall increase in fat mass and larger adipocytes.
Scientists later tested mice on social tasks. They showed a life-long decrease in sociability as their adipose tissue increased. The strange fact was that female mice showed no such effect.
Is there a sex-dependent difference in other psychobiological adaptations? This remains unclear, and scientists are planning to study it in the future.
Professor Carmen Sandi at EPFL said, “What we focused here was in the reduction in sociability that you see in depression. We also know from epidemiological studies in humans that it can be linked with early life stress – peripubertal stress, which can program people to be less sociable.”
Later, scientists determined the biology behind this by pointing a series of tests to a specific enzyme called adipokine nicotinamide phosphoribosyltransferase (NAMPT). The NAMPT is involved in some pathological metabolic problems caused by obesity.
NAMPT exists in two forms:
- An intracellular form, which regulates the production of nicotinamide adenine dinucleotide (NAD+).
- In its extracellular form (eNAMPT), the enzyme is present in the blood.
Stress during peripuberty reduces NAMPT in fat cells. Consequently, this drops eNAMPT in their blood at adulthood compared to non-stressed mice.
When scientists observed the nucleus accumbens of the socially impaired and healthy, “control” mice, they found lower NAD+ levels and problems with the enzyme Sirtuin-1. Sirtuin-1 is an enzyme that depends on NAD+ to regulate the …….