Review Article

Circadian Disruption Leads to Loss of Homeostasis and Disease

Figure 1

Moments of peak activity for physiological variables in rats living undisturbed in control ad libitum conditions (a) and rats exposed for 4 weeks to 8 h forced activity during the rest phase (b). Symbols represent the moments of maximal expression of each variable along the 24 h cycle. Data were obtained from three previous reports [60, 61, 67] and peak values were statistically different from low values of the same group according to a one way ANOVA ( 𝑃 < 0 . 0 5 ) . Day and night are represented by white and black horizontal bars below the graphs and the time in the activity drums is represented by the grey striped horizontal bar. The “y” axis represents variables measured in metabolism (triangles) in the liver (squares) and in the brain (circles). Horizontal lines indicate loss of rhythmicity and therefore no significant peak value for that variable and condition. The daily scheduled activity induced shifts of several variables and led to circadian misalignment. Abbreviations: Temp: core temperature; TAG: triglycerides; Cort: corticosterone; Per1: clock gene period 1; Per2: clock gene period 2; SCN: suprachiasmatic nucleus; PVN: paraventricular nucleus in the hypothalamus; DMH: dorsomedial nucleus in the hypothalamus; ARC: arcuate nucleus.
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(a)
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(b)