Sweet treats before sleep disrupt the clock system and increase metabolic risk markers in healthy rats

Area of Science:

• Chronobiology
• Metabolic Health
• Animal Models

Background:

• Biological rhythms, including circadian rhythms, are crucial for maintaining physiological homeostasis.
• Disruptions to these rhythms, influenced by factors like light and food intake timing, are linked to increased metabolic risk.
• Behavioral cues, such as meal timing, significantly regulate circadian rhythms alongside light exposure.

Purpose of the Study:

• To investigate the impact of chronic consumption of a sweet treat before sleep on diurnal rhythmicity and metabolism in healthy rats.
• To determine if the timing of sugar intake influences circadian rhythm disruption and metabolic parameters.
• To explore the effects on clock gene expression in the hypothalamus.

Main Methods:

• 32 Fischer rats were administered a daily low dose of sugar (160 mg/kg) for 4 weeks.
• Sugar was administered either in the morning (ZT0) or evening (ZT12), simulating different meal timings.
• Animals were sacrificed at specific time points (ZT1, ZT7, ZT13, ZT19) to analyze clock gene expression and metabolic parameters.

Main Results:

• Consumption of a sweet treat at the beginning of the resting period (evening) led to increased body weight gain and higher cardiometabolic risk.
• Diurnal expression patterns of central clock genes (Nampt, Bmal1, Rev-erbα, Cart) and food intake signaling genes in the hypothalamus were altered based on snack timing.
• These changes indicate that late-night sugar intake disrupts hypothalamic control of energy homeostasis.

Conclusions:

• The metabolic effects and central clock gene expression changes induced by sugar are strongly time-dependent.
• Consuming a sweet treat before bedtime causes greater circadian metabolic disruption compared to morning consumption.
• Timing of food intake is a critical factor in modulating circadian rhythms and metabolic health.