Time-restricted feeding attenuates age-related cardiac decline in Drosophila

Abstract

Circadian clocks orchestrate periods of rest or activity and feeding or fasting over the course of a 24-hour day and maintain homeostasis. To assess whether a consolidated 24-hour cycle of feeding and fasting can sustain health, we explored the effect of time-restricted feeding (TRF; food access limited to daytime 12 hours every day) on neural, peripheral, and cardiovascular physiology in Drosophila melanogaster. We detected improved sleep, prevention of body weight gain, and deceleration of cardiac aging under TRF, even when caloric intake and activity were unchanged. We used temporal gene expression profiling and validation through classical genetics to identify the TCP-1 ring complex (TRiC) chaperonin, the mitochondrial electron transport chain complexes, and the circadian clock as pathways mediating the benefits of TRF.

Conflict of interest statement

We declare no conflicting interests.

Copyright © 2015, American Association for the Advancement of Science.

Figures

Fig. 1. TRF improves sleep and prevents body weight gain without reducing caloric intake

(a) Food consumption (CAFÉ assay) over a 24h period in 5 week old wild type (WT) Oregon-R flies. (b) Body weight of 3, 5 and 7 week old flies. (c) Flight index of 5 week old flies (n>30 flies). (d) Activity counts and (e) sleep duration of 5 week old flies averaged from at least 7 days of recording. (values are average + s.e.m, *: p<0.05, n.s.: p>0.05 Student’s t-test). Error bars: s.e.m.

Fig. 2. TRF protects against age- and diet-induced decline in cardiac function

(a) M-mode (mechanical mode) traces showing the movement of the heart tube edge (y-axis) over time (x-axis) were generated from videos of the heart beneath the 3rd thoracic segment by digitally excising and aligning 1 pixel width vertical strip spanning the heart tube from a fixed location in successive frames. From the M-mode, cardiac parameters are calculated. Red arrowheads indicate the direction of age- or high-fat diet-induced changes. (b) Example 20 sec M-mode traces of ALF and TRF flies with superimposed orange (ALF) or blue (TRF) bar indicating diastolic intervals. Average (c) DI (d) HP, (e) AI and (f) FS show protection from age dependent deterioration in the TRF flies. (g) Feeding regimens employed to test the effect of TRF at an early or late age revealed improvement in (h) AI. (i) Representative M-modes of 5 week old flies subject to fat diet ALF or TRF. Average (j) DI, (k) AI, and (l) HP improved under TRF. Average values for ALF and TRF flies fed normal cornmeal diets are shown as broken lines for reference. Averages (n>30) are shown. *;p<0.05, Mann Whitney test. Error bars: s.e.m.

Fig. 3. Transcriptional correlates of improved health in TRF

Heat map representation of transcripts scored rhythmic under both ALF and TRF conditions in (a) head and (b) periphery of 5 week old flies. Normalized and color coded transcript levels at 8 different Zeitgeber times (ZT) spanning day (yellow bar) and night (dark bar) are shown. Area plots showing the peak phase of expression of rhythmic transcripts in ALF (red) or TRF (blue) fly (c) head or (d) periphery binned into 1 h intervals. For clarity, data in a–d are double plotted over two 24 h periods. (e) Heat map representation of transcripts that are up (purple) or down (blue) regulated in TRF flies. Transcript levels in fly hearts collected at 6 h interval over 24 h are shown. (f) Expression level (RPKMs) of example TRiC chaperonin subunits and (g) ETC components in ALF and TRF hearts at 5 weeks age.

Fig. 4. Genetic basis for the beneficial effects of TRF

5 week old flies carrying loss of function mutations in (a,b) clock components or heterozygous for P-element insertions in (c,d) TRiC chaperonin components fail to improve (a,c) heart period and (b,d) fractional shortening under TRF (n ≥12 circadian mutants, n≥17 TRiC mutants). Wildtype (Oregon-R) data are included for reference. (e) Representative M-modes of Tcp-1eta mutant flies exhibiting lack of TRF-driven cardioprotection. (f) Heart period and (g) arrhythmia index, and (h) representative M-modes show improved cardiac function in 5-week old ALF flies with heart specific knockdown of mitochondrial ETC genes relative to 5 week old male WT flies (n≥24). 3 and 7-week old male WT data are included for reference. *;p<0.05, Mann Whitney test. Error bars: s.e.m.