Beneficial epigenetic effects of mild stress with social support during puberty

This 2016 Pennsylvania rodent study found:

“Stress in the context of social support experienced over the pubertal window can promote epigenetic reprogramming in the brain to increase resilience to age-related cognitive decline in females.

These findings are actually consistent with previous studies showing that some amount of adversity, or adversity under more favorable circumstances such as social support or a protective gene polymorphism, provides a measure of ‘grit’ in coping with later life challenges.

Our findings provide a unique perspective on this relationship, as they highlight the important link between experience during the pubertal window and cognitive health during aging.”

These researchers made efforts to further investigate causes of unexpected results, such as:

“Peripubertal stress alone did not significantly alter Barnes maze performance in aging compared to aged Controls. Mice that had experienced stress with concurrent social support (CVS + SI) actually performed better than Control aged mice, specifically in learning the reversal task faster.

Peripubertal stress had no effect on corticosterone levels in response to an acute restraint stress or in sensorimotor gating and baseline startle reactivity.”

Their investigations led to epigenetic findings:

“Consistent with our behavioral findings, stress in the context of social interaction resulted in long-term reprogramming of gene expression in the PFC [prefrontal cortex]. While there were no differentially expressed genes between Control and CVS females, there were 88 genes that were significantly different between Control and CVS + SI groups. Of genes that were downregulated, a large portion (23 genes; 35%) were microRNAs.

We found that the PFC transcriptome of CVS + SI aged females was significantly enriched for predicted targets of the 23 microRNAs that were downregulated in the PFC in these mice. This suggests that microRNAs represent a mode of regulation capable of enacting far-reaching programmatic effects, and are a critical epigenetic gene expression regulatory mechanism.”

Applicability to humans was suggested by associations such as:

“A single microRNA can target more than a hundred different mRNA targets, and more than 45,000 conserved microRNA binding sites have been annotated in the 3′ UTR of 60% of human genes.”

A few limitations were noted:

“Given that mice at this age (1 year) are commonly compared to ‘late middle aged’ humans, later aging time points may yield differences in this group. Alternatively, it is possible that there was an effect of peripubertal stress that was not long-lasting due to the mild nature of our chronic stress model.

To include early neglect as a part of the stressor experience, CVS females were weaned one week earlier (PN21) than Control and CVS + SI mice. Addition of stress of this earlier weaning likely poses a significant contribution to programming of the PFC.”

One of the study coauthors was also a coauthor of:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4870871/ “Peripubertal stress with social support promotes resilience in the face of aging”