Food entrainment in mice leads to sex- and organ-specific responses in the digestive system and nutrient metabolism

One of the main zeitgebers in the digestive system is food intake; however, little is known about organ- and sex-specific differences in food-driven circadian regulation. We placed male and female C57Bl/6 mice on time-restricted feeding (TRF), limiting food intake period to 8 hours. TRF was started either at dark (ZT12) or light (ZT0) onset and continued for 28 days, with or without an additional 4 hour forward shift on day 15. TRF from ZT12 to ZT20 led to the highest weight gain in females, but the lowest weight gain in males, while improving intestinal transepithelial resistance (TEER) in both sexes. Unexpectedly, it also led to the disappearance of diurnal rhythmicity in several hepatic genes. Shifting the TRF start to ZT16 led to an increase in weight gain and a decrease in fasting plasma glucose levels in male mice, as well as to strong rhythmicity in nutrient metabolism-related hepatic and duodenal genes in both sexes. Surprisingly, food intake during ZT0-ZT8 caused only minor changes in physiological responses. However, it did lead to an overall downregulation of gene expression in the liver, an upregulation in the stomach and duodenum, and to flattened diurnal responses. Shifting the start of food intake to ZT4 was highly detrimental, causing an increase in fasting blood glucose levels, a decrease in TEER, and disrupting diurnal gene expression pattern in the liver and stomach. Despite this, in duodenum TRF from ZT4 to ZT12 acted as a potent zeitgeber. These results demonstrate that the adjustment to food intake time in mice is highly sex- and organ-specific. Our chosen TRF regimes were not able to achieve full diurnal rhythm synchronization across the digestive system. Instead, we observed that the same food intake time might be a strong zeitgeber in one organ, and a rhythm disruptor in another. ### Competing Interest Statement The authors have declared no competing interest.