Timing of light Circadian and metabolic effects

In mammals, the circadian timing system consists of a light- sensitive central brain clock located in the hypothalamic suprachiasmatic nucleus (SCN) and various peripheral clocks. Disruption of this circadian system is associated with adverse health problems including adiposity and diabetes mellitus. This thesis aims to study the timing of light, and the circadian and metabolic effects on rats and humans.
Chapter 2 investigates the adaptation speed of behavioral and metabolic parameters in a rat model of jet lag and shift work, and the effects of time-restricted food intake as a potential strategy to mitigate the negative effects of such phase-inversions in rats.
Chapter 3 investigates possible changes in the liver and muscle insulin signaling pathway, the adaptation speed of the molecular clock in liver, muscle and white adipose tissue (WAT) and the daily body temperature rhythm in the same rat model. Moreover we investigate the effect of high fat diet, either ad libitum or restricted to the dark period, on the adaptation speed after a 12h phase shift of the light/dark cycle in rats.
Chapter 4 investigates the blood oxygenation level dependent light responsiveness of the SCN-area in three groups of obese people: 1) normal insulin sensitivity, 2) insulin resistance and 3) type 2 diabetes. Further, we investigate the resting-state functional connectivity from the SCN-area to pre-specified regions of interest in brain as a marker of resting-state SCN-area activity.
Chapter 5 investigates the effect of morning bright light exposure on the human WAT transcriptome.