Calorie Restriction Suppresses Age-Dependent Hippocampal Transcriptional Signatures.

Marissa J. Schafer,Adriana Heguy,Melissa J. Alldred,Igor Dolgalev,Stephen D. Ginsberg,Rozalyn M Anderson

doi:10.1371/journal.pone.0133923

Abstract

Calorie restriction (CR) enhances longevity and mitigates aging phenotypes in numerous species. Physiological responses to CR are cell-type specific and variable throughout the lifespan. However, the mosaic of molecular changes responsible for CR benefits remains unclear, particularly in brain regions susceptible to deterioration during aging. We examined the influence of long-term CR on the CA1 hippocampal region, a key learning and memory brain area that is vulnerable to age-related pathologies, such as Alzheimer’s disease (AD). Through mRNA sequencing and NanoString nCounter analysis, we demonstrate that one year of CR feeding suppresses age-dependent signatures of 882 genes functionally associated with synaptic transmission-related pathways, including calcium signaling, long-term potentiation (LTP), and Creb signaling in wild-type mice. By comparing the influence of CR on hippocampal CA1 region transcriptional profiles at younger-adult (5 months, 2.5 months of feeding) and older-adult (15 months, 12.5 months of feeding) timepoints, we identify conserved upregulation of proteome quality control and calcium buffering genes, including heat shock 70 kDa protein 1b (Hspa1b) and heat shock 70 kDa protein 5 (Hspa5), protein disulfide isomerase family A member 4 (Pdia4) and protein disulfide isomerase family A member 6 (Pdia6), and calreticulin (Calr). Expression levels of putative neuroprotective factors, klotho (Kl) and transthyretin (Ttr), are also elevated by CR in adulthood, although the global CR-specific expression profiles at younger and older timepoints are highly divergent. At a previously unachieved resolution, our results demonstrate conserved activation of neuroprotective gene signatures and broad CR-suppression of age-dependent hippocampal CA1 region expression changes, indicating that CR functionally maintains a more youthful transcriptional state within the hippocampal CA1 sector.

Highlights

Dysfunctional synaptic connections and neurodegeneration are posited to be the cellular origins of age-dependent memory and cognitive impairment [1]
Using RNA isolated from hippocampal CA1 microdissections from younger-adult (5 months, 2.5 months of feeding) and older-adult (15 months, 12.5 months of feeding) wild-type mice maintained on 30% Calorie restriction (CR) or ad libitum (AL) diets, we performed 50 nucleotide paired-end total mRNA sequencing, yielding an average of 73.6 million paired reads per sample
Through unbiased mRNA sequence analysis and targeted NanoString nCounter validation of the CA1 hippocampal region at two distinct timepoints during the adult mouse lifespan, we demonstrate that CR dramatically suppresses age-dependent transcriptional changes

Summary

Introduction

Dysfunctional synaptic connections and neurodegeneration are posited to be the cellular origins of age-dependent memory and cognitive impairment [1]. Intrinsic electrical and structural characteristics of CA1 pyramidal neurons may contribute to neurodegenerative vulnerability, where susceptibility to excitotoxicity may originate from diminished calcium buffering capacity in older age, relative to less excitable cell types [7,8]. CA1 pyramidal neurons are dependent on pro-survival trophic factor signaling, including brain-derived neurotrophic factor (Bdnf), and reduction in trophic factor signaling throughout aging, which occurs coincident with neuron loss and memory impairment, may contribute to the selective vulnerability phenotype [9,10]

Methods

Results

Conclusion