Type 1 Diabetes Differentially Disrupts Right and Left Ventricular Daily Rhythms

Figures

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  Figure 1.. Ventricle-specific circadian transcriptional rhythms in the healthy right ventricle (RV) and left ventricle (LV). Cosinor curves of core clock, clock-controlled output genes, and metabolic gene expression across the 24-h light-dark cycle in the left ventricle (LV) and right ventricle (RV) of control male mice. Transcript levels of Arntl1 (A), Per2 (B), Pdk4 (C), Ucp3 (D), Nr1d1 (E), and Dbp (F) were measured by qRT-PCR at 6 zeitgeber time (ZT0, ZT4, ZT8, ZT12, ZT18, ZT22) and normalized to the reference gene Rpl26. The x-axis represents zeitgeber time (ZT; hours), where ZT0 denotes lights-on and ZT12 denotes lights-off. G and H: summary table of cosinor-derived parameters for each gene in the RV and LV. Amplitude (half the peak-to-trough range) and acrophase (clock time of peak expression, in ZT hours). I: cosinor analysis comparing LV vs. RV rhythms for each transcript. Shown are P values for between-chamber differences in amplitude, acrophase, and overall rhythm waveform (F-test). LV—red and RV—blue. n = 4 per group/ZT.

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  Figure 2.. T1D differentially impacts left and right ventricular mass across the 24-h cycle. A: right ventricular mass normalized to tibia length (RV/TL, mg/mm) pooled from all 6 zeitgeber time (ZT). T1D mice show significantly higher RV/TL compared with controls (Con). B: cosinor analysis fit for RV/TL demonstrating altered circadian oscillations in T1D compared with controls. C: left ventricular mass normalized to tibia length (LV/TL, mg/mm). T1D mice show significantly lower LV/TL compared with controls. D: cosinor analysis fit for LV/TL demonstrating altered circadian oscillations in T1D compared with controls. Data are expressed as means ± SEM. n = 4 per group/ZT. ***P < 0.001, ****P < 0.0001 by Student's t test.

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  Figure 3.. Echocardiography in Con and T1D at ZT0–4 and ZT12–16 suggests that T1D imposes an aberrant time-of-day variation in right ventricle (RV) and left ventricle (LV) systolic function. A: in control mice, heart rate (HR) was higher at ZT0–4 compared with ZT12–16, whereas T1D animals showed the opposite pattern, with HR declining from ZT0–4 to ZT12–16. B: RV fractional area change (RV FAC) was reduced by T1D with T1D animals showing lower RV FAC at both ZT compared with controls. C: RV stroke volume (SV) was lower at ZT12–16 compared with ZT0–4 in T1D animals. D: RV isovolumetric relaxation time (RV IVRT) showed a main effect of ZT, with values declining from ZT0–4 to ZT12–16. E: LV FAC was reduced in T1D animals compared with controls, with a significant diabetes × ZT interaction. F: LV ejection fraction (LV EF) was reduced in T1D at both ZT, with T1D animals losing the day-night difference in EF. G: LV IVRT was prolonged with T1D, irrespective of ZT. Data were analyzed by 2-way ANOVA (ZT × condition). Data are expressed as means ± SEM. n = 8 per group. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. ZT, zeitgeber time.

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  Figure 4.. Alterations in gene expression rhythms in the T1D right ventricle (RV). A: Arntl1 exhibited 24-h rhythmicity in both Con and T1D animals with a delay in the acrophase in T1D mice. B: Per2 was robustly rhythmic with no condition difference and a highly conserved acrophase. C and D: the metabolic clock targets Pdk4 and Ucp3 did not achieve significant rhythmicity in either condition and showed no condition difference. E: Nr1d1 exhibited significant rhythmicity in Con, and the T1D waveform was different from Con, with an advanced acrophase. F: Dbp showed rhythmicity in Con, with T1D waveform significantly different. Amplitude was lower, whereas acrophase was preserved. G: table showing P values for rhythmicity (suggesting if there is presence of a significant 24-h oscillation), amplitude, and acrophase in Con and T1D. H: P values for amplitude, acrophase, and rhythm difference between Con and T1D. Expression was normalized to Rpl26 and expressed as fold change relative to within-group ZT0. RV Con—blue solid line and RV T1D—blue dashed line. n = 4 per group/ZT. ZT, zeitgeber time.

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  Figure 5.. Alterations in gene expression rhythms in the T1D left ventricle (LV). A: Arntl1 exhibited 24-h rhythmicity in both Con and T1D animals with no significant differences in amplitude and acrophase in T1D mice. B: Per2 was robustly rhythmic in both groups with significant condition differences and reduced amplitude. C and D: the metabolic clock targets Pdk4 and Ucp3 did not achieve significant rhythmicity in either condition. E: Nr1d1 was rhythmic in Con and T1D, with T1D showing no changes in amplitude and acrophase. F: Dbp showed rhythmicity in Con and T1D, with T1D showing a near-tripling of amplitude, with acrophase preserved. G: table showing P values for rhythmicity (suggesting if there is presence of a significant 24-h oscillation), amplitude, and acrophase in Con and T1D. H: P values for amplitude, acrophase, and rhythm difference between Con and T1D. Expression was normalized to Rpl26 and expressed as fold change relative to within-group ZT0. LV Con—red solid line and LV T1D—red dashed line. n = 4 per group/ZT. ZT, zeitgeber time.