Time-Restricted Feeding Improves Circadian Dysfunction as well as Motor Symptoms in the Q175 Mouse Model of Huntington's Disease

Abstract

Huntington's disease (HD) patients suffer from a progressive neurodegeneration that results in cognitive, psychiatric, cardiovascular, and motor dysfunction. Disturbances in sleep/wake cycles are common among HD patients with reports of delayed sleep onset, frequent bedtime awakenings, and fatigue during the day. The heterozygous Q175 mouse model of HD has been shown to phenocopy many HD core symptoms including circadian dysfunctions. Because circadian dysfunction manifests early in the disease in both patients and mouse models, we sought to determine if early intervention that improve circadian rhythmicity can benefit HD and delay disease progression. We determined the effects of time-restricted feeding (TRF) on the Q175 mouse model. At six months of age, the animals were divided into two groups: ad libitum (ad lib) and TRF. The TRF-treated Q175 mice were exposed to a 6-h feeding/18-h fasting regimen that was designed to be aligned with the middle of the time when mice are normally active. After three months of treatment (when mice reached the early disease stage), the TRF-treated Q175 mice showed improvements in their locomotor activity rhythm and sleep awakening time. Furthermore, we found improved heart rate variability (HRV), suggesting that their autonomic nervous system dysfunction was improved. Importantly, treated Q175 mice exhibited improved motor performance compared to untreated Q175 controls, and the motor improvements were correlated with improved circadian output. Finally, we found that the expression of several HD-relevant markers was restored to WT levels in the striatum of the treated mice using NanoString gene expression assays.

Keywords: Huntington’s disease; Q175; circadian rhythms; fast/feed cycle; time-restricted feeding.

Figures

Graphical abstract

Figure 1.

Locomotor activity rhythms were improved by the TRF regimen. A, Examples of cage activity rhythms recorded from Q175 mutants under control (left) and TRF (right) conditions. The activity levels in the actograms were normalized to the same scale (85% of the maximum of the most active individual). Each row represents two consecutive days, and the second day is repeated at the beginning of the next row. The orange bar on the top of actograms indicates the time when food hopper is opened. B, The strength of the activity rhythm is indicated by the power (%V) of the χ2 periodogram analysis. C, The averaged level of cage activity. D, The averaged variation in onset from the best-fit regression line. E, Average waveforms from 10 d of cage activity (1-h window) are shown and SEs across animals are indicated. F, The number of activity bouts (separated by a gap of 21 mins or more) during rest phase (ZT 0-12), active phase (ZT 12-24), and 24 h are reported as the level of fragmentation of the circadian activity cycle. Black bars represent Q175 mutants under ad lib condition, and orange bars represent Q175 mutants under timed feeding condition. G, The average length of activity bouts during their active phase. The white/black bar on the top of actograms (A) and waveforms (E) indicates the 12/12 h LD cycle. The temporal activity wave form was analyzed using a two-way RM ANOVA with time and treatment as factors. Other comparisons between Q175 cohorts were made using a t test. Asterisks represent significant differences due to TRF regimen compared to ad lib controls (p < 0.05); n = 8/group.

Figure 2.

TRF prevented disease-caused awakening time without altering the amount of sleep behavior. Video recording in combination with automated mouse tracking analysis software was used to measure immobility-defined sleep. A, Running averages (1-h window) of immobility-defined sleep in Q175 mutants with ad lib (black) and timed feeding (orange) are plotted. The white/black bar on the top of wave form indicates the 12/12 h LD cycle. B–F, Quantification of the immobility-defined sleep rhythms. The temporal sleep wave form was analyzed using a two-way RM ANOVA with time and treatment as factors. Other comparisons between Q175 cohorts were made using a t test. Asterisks represent significant differences due to TRF regimen compared to ad lib controls (p < 0.05); n = 8/group.

Figure 3.

Autonomic output rhythms were improved by the TRF regimen. The autonomic outputs from ad lib (black circles) and TRF (orange triangles) Q175 mice were recorded simultaneously using telemetry device. A–D, Hourly running averages of activity (A), CBT (B), HR (C), and HRV from both groups are plotted (D). E, The HR rhythm amplitude, determined by the ratio of max and min of the day, in control and TRF-treated Q175 mice. F, The 24-h averaged HRV in control and TRF-treated Q175 mice. The temporal waveforms of autonomic outputs were analyzed using a two-way RM ANOVA with time and treatment as factors. Other comparisons between Q175 cohorts were made using a t test. Asterisks represent significant differences due to TRF regimen compared to ad lib controls (p < 0.05); n = 7/group.

Figure 4.

TRF improved motor performance in the Q175 HD model. A, The accelerating rotarod test revealed that the TRF treatment improved motor performance by showing longer latency to fall. B, The challenging beam motor test indicated that the TRF treatment improved performance (fewer errors) by making fewer errors when the mice crossed the balanced beam. C, The circadian parameters and the performance in the two motor tests of individual mouse in ad lib group (black circles) and TRF group (orange triangles) are plotted in a 3D-XYZ grid. In this XYZ grid, there are two distinctive clusters, suggesting that the mouse with stronger circadian rhythms performed better in both motor tests. Comparisons between Q175 cohorts were made using a t test. Asterisks represent significant differences due to TRF regimen compared to ad lib controls (p < 0.05). The correlations between circadian parameters and motor performance are described in the text; n = 8/group.

Figure 5.

Altered expression level of multiple HD markers in the striatum of the Q175 HD model. A, Differentially expressed genes in the striatum observed between TRF group and ad lib group using NanoString (find all gene expression data in Table 6). The same Q175 mice that underwent activity/sleep monitoring and behavioral tests were allowed to recover for four weeks from manipulations before tissue collection. The signal intensity of individual genes was normalized by adjusting to internal positive standards within each sample (see Materials and Methods). B, Enriched functional clustering in the striatum using the IPA analysis tool (based on data in Table 6; uncorrected Fisher’s exact test p value < 0.05). The clusters of interest with statistical significance are picked and enriched biofunctions in those picked clusters are shown (in descending order of significance). The picked clusters include Behavior (p = 2.72E-17, color orange), Cell-to-cell signaling and interaction (p = 1.02E-17, color blue), inflammatory response (p = 2.87E-04, color pink), and neurologic disease (p = 8.74E-14, color green).