Differences in genome-wide gene expression response in peripheral blood mononuclear cells between young and old men upon caloric restriction

Abstract

Background: Caloric restriction (CR) is considered to increase lifespan and to prevent various age-related diseases in different nonhuman organisms. Only a limited number of CR studies have been performed on humans, and results put CR as a beneficial tool to decrease risk factors in several age-related diseases. The question remains at what age CR should be implemented to be most effective with respect to healthy aging. The aim of our study was to elucidate the role of age in the transcriptional response to a completely controlled 30 % CR diet on immune cells, as immune response is affected during aging. Ten healthy young men, aged 20-28, and nine healthy old men, aged 64-85, were subjected to a 2-week weight maintenance diet, followed by 3 weeks of 30 % CR. Before and after 30 % CR, the whole genome gene expression in peripheral blood mononuclear cells (PBMCs) was assessed.

Results: Expression of 554 genes showed a different response between young and old men upon CR. Gene set enrichment analysis revealed a downregulation of gene sets involved in the immune response in young but not in old men. At baseline, immune response-related genes were higher expressed in old compared to young men. Upstream regulator analyses revealed that most potential regulators were controlling the immune response.

Conclusions: Based on the gene expression data, we theorise that a short period of CR is not effective in old men regarding immune-related pathways while it is effective in young men.

Trial registration: ClinicalTrials.gov, NCT00561145.

Keywords: Age; Caloric restriction; Gene expression; Microarray; Peripheral blood mononuclear cells.

Fig. 1

Stepwise selection of genes in microarray analysis of old versus young men upon 3 weeks of 30 % CR: 12,783 genes were selected for signal intensity (≥5 in >5 arrays), a for a difference in expression between old and young (P < 0.05) men at baseline (left track) and upon CR (right track), and b a change in expression of genes for young (left track) and old (right track) in response to CR. The last box depicts the number of genes that has a different response to CR in old versus young men

Fig. 2

Correlation heat maps of CR-induced significant changes in gene expression of (A) genes regulated by upstream regulators in young, depicted for the response in young (A1) and old (A2), and of (B) genes regulated by upstream regulators in old, depicted for the response in young (B1) and old (B2). Scale: green = correlation score of −1, pink = correlation score of 1

Fig. 3

Stepwise selection of genes in microarray analysis to identify genes in which expression changed from an old profile to a young profile upon 3 weeks of 30 % CR. For signal intensity, 12,783 genes were selected (≥5 in >5 arrays); from these, 96 genes were selected that were differently expressed between old and young men before CR (P < 0.05); the last part depicts number of genes that show a different response to CR in old versus young men. Finally, 23 genes with a significant change in expression within young (left track) men and 55 genes within old (right track) men are shown

Fig. 4

Heat map of genes of which expression changed from an old profile to a young profile upon CR. (a) baseline expression level, (b) response to CR, and (c) expression levels after CR for young and old men. Each column represents one person; each row represents one gene. Depicted are for (a) the signal log ratio calculated as gene expression values at baseline compared to the average of the whole group, for (b) the signal log ratios calculated as gene expression values upon CR compared to gene expression values at baseline, and for (c) the signal log ratios as gene expression values after CR compared to the average of the whole group.

Fig. 5

Flow diagram of subject inclusion