Hepatology Snapshot: The liver by day and by night
Circadian clocks fluctuate over a period of 24 hours in light-sensitive organisms. It helps in coordinating a wide variety of physiological, behavioral, and molecular functions with geophysical time. The liver circadian system is probably the most well-characterized as compare to other peripheral organs. Rona Aviram and colleagues published a paper in the Journal of Hepatology under the title “Hepatology Snapshot: The liver by day and by night”. The summary of this paper is mentioned below:
Objective:
To highlight key rhythmic processes of the liver circadian system
To emphasize the main regulators and metabolites involved.
Method:
The information highlighted in the paper was developed from the currently available evidence and scientific and medical knowledge.
Findings:
- Glucose homeostasis:
As glucose demand and food intake differs throughout the day, the liver predicts and counteracts these variations. Liver stores excess glucose in the form of glycogen followed by meal-time. During the fasting phase, gluconeogenesis and glycogenolysis elevate through the liver to cope up with changing energetic demand. Hence, the liver plays an important role in maintaining glucose homeostasis. - Lipids and mitochondrial dynamics
Liver lipid metabolism reveals robust circadian rhythmicity that is evident in the transcript levels of relevant enzymes and the lipids themselves. Daily changes happen in both phospholipids and triglycerides, as do organelle-specific lipids and cholesterol synthesis. - Detoxification and bile acid metabolism
Another important process taken by the liver is bile production and secretion, which elevates at the beginning of the active phase (day for humans). Additionally, detoxification processes peak around simultaneously, due to multilevel regulation. The expression of many ABC transporters and enzymes also elevated during the rest-active transition for the excretion of various compounds into the bile duct. - Hepatic size
Generally, the size of the liver, and specifically the size of hepatocytes, undergoes rhythmicity daily.
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