Science - USA (2022-02-11)

measures of TDEE using doubly labeled water
together with changes in body composition ( 11 ).
This study established that in free-living con-
ditions, humans achieve ~14% sustained CR
for 2 years ( 10 – 12 ). This level of voluntary CR
in humans in free-living conditions is much

lower than the forced 25 to 40% restriction of

calories in laboratory animals and may engage

unique mechanisms to maintain homeostasis.

Mice on life-long 40% CR maintain thymic

lymphopoiesis into late life and have a diverse

T cell receptor (TCR) diversity ( 13 ), whereas

14% CR in humans reduces the number of

circulating lymphocytes and proinflammatory

cytokines in the blood ( 14 ). Aging of thymus

precedes aging of other organs, a process char-

acterized by increased thymic lipid accumu-

lation and loss of T cell production ( 15 ). We

672 11 FEBRUARY 2022•VOL 375 ISSUE 6581 science.orgSCIENCE

Adipose tissue

AC

G Adipose tissue

H

I Adipose tissue

D

B E

CD4 T cells

Baseline 24 months post calorie restriction

Ascending

aorta

Thymus

Sternum

Thymus

Age

Total = 32 Total = 32 Total = 32

20s

30s

40s

8 (25%)

9 (30%)

15 (46.9%)

Sex

Male

Female

6 (18.7%)

26 (81.2%)

BMI (Kg/m^2 )

18 (55.9%)14 (43.4%)

00

Healthy weight (18.5 to 24.9)

Overweight (25 to 29.9)

Underweight (Below 18.5)

Obese range (30 or greater)

sjTREC study participants

F

−10

0

10

−20 −10 0 10 20

PC1 (30.749%)

PC2 (20.214%)

Timepoint

Baseline

24 month

0.0

0.5

1.0

−0.4 −0.2log2FoldChange0.0 0.2

−log10(padj)

significance level

Baseline vs 24 month

−10

0

10

−10 PC1 (^0) (19.5%) 10
PC2 (13.1%)
Timepoint
Baseline
12 month
24 month
194 233 150
Baseline vs 24m Baseline vs 12m
Down-regulated upon CR Up-regulated upon CR
203 131 84
Baseline vs 24m Baseline vs 12m
−4
−2
0
2
−2 −1 0 1 2
log2FC(Baseline vs 24m)
log2FC(Baseline vs 12m)
Baseline
12 month
24 month
−2
−1
0
1
2
z-score
24 month vs 12 month
0.0
0.5
1.0
−2.5 0.0 2.5 5.0
log2FoldChange
−log10(padj)
significance level
J
Baseline 24 month
0
1
2
3
4
5
Thymic volume
Volume of OBJ2 (x10
5 mm³)
Baseline 24 month
0
20
40
60
80
100
TRECs (x10E5)
Per 1ug of CD8+DNA
Baseline 24 month
0
20
40
60
80 P=0.001
P=0.0002
TRECs (x10E5)
Per 1ug of CD4+DNA
Fig. 1. CR in humans improves thymic function and remodels adipose
transcriptome.(A) Participant information for the sjTREC study (n= 32).
(B) Representative MRI examination image of a female participant performed
with the subject head first and supine in a 3 T full-body scanner at the baseline
(left) and after 2 years of CR (right). The region of interest depicting the
thymus is highlighted by yellow arrows in dotted circle after the fat saturation
sequence was applied. (C) Thymic volume of female study participants analyzed
by MRI at baseline and after 24 months of CR. (DandE) sjTREC analysis
results of CD4 (D) and CD8 (E) T cells at baseline after 2 years of CR. Red line
indicates TREC in females; blue line indicates TREC in males. (F), PCA of
transcriptional profile of blood CD4 T cells at baseline and after 2 years of CR.
Volcano plot depicts the results of differential gene expression analysis of CD4
T cells between baseline and after 2 years of CR. (G) PCA of RNA sequencing of
adipose tissue at baseline and after 1 and 2 years of CR (n= 8). Volcano plot
depicts the results of differential analysis of subcutaneous adipose tissue
between 1 and 2 years of CR (right). Each dot represents a gene. (H) Heatmap of
significant differentially expressed genes between baseline and either 1 or 2 years
of CR in adipose tissue. (I) Venn diagram illustrating overlaps between genes
found to be differential [false discovery rate (FDR), 5%] between baseline and
either 1 or 2 years of CR. Overlapping area indicates the genes that are
differentially expressed after both 1 and 2 years of CR. (J) Comparison of the
log2-scaled fold change between baseline and 1 or 2 years of CR.
RESEARCH | REPORTS