# Transcriptome Analysis Reveals Circadian Rhythmic Regulation of Lipid Metabolism and Immune Function in Chicken Livers

## TL;DR

This study finds that chicken liver genes related to lipid metabolism and immunity show daily rhythms, offering insights into how chickens manage energy and disease.

## Contribution

The study identifies specific genes and pathways in chicken livers that exhibit circadian rhythmicity in lipid metabolism and immune function.

## Key findings

- 845 differentially expressed genes were detected, with lipid metabolism and immune function showing the most significant changes.
- Weighted gene co-expression network analysis linked tan and cyan modules to hepatic circadian rhythm.
- Cosinor analysis identified 9 lipid-related and 11 immune-related genes with significant rhythmic expression.

## Abstract

In this study, liver samples were collected at 7 time points during one light/dark cycle, and transcriptomic sequencing was used to explore candidate genes and pathways associated with hepatic rhythm. Trend analysis showed that genes such as FAM21C, SRSF4, TLR2A, MSMO1, ELOVL2, and HMGCR exhibited rhythmic variation trends. A total of 845 differentially expressed genes (e.g., MSMO1, FAM21C) were detected between light/dark conditions, among which the changes in the activity of lipid metabolism and immune function were the most significant. Weighted gene co-expression network analysis revealed that two modules were strongly associated with the hepatic circadian rhythm. Cosinor analysis showed that 9 lipid-related genes (e.g., MSMO1, HMGCR1, ELOVL2) and 11 immune-related genes (e.g., FAM21C, TLR4, TLR2A) exhibited significant rhythmic expression.

Liver rhythm has a significant effect on lipid metabolism and immune function in chickens. However, reports on its underlying mechanisms and key genes are relatively scarce. We collected liver samples at seven time points during one light/dark cycle and investigated the candidate genes and pathways related to hepatic rhythm through transcriptomic sequencing. Trend analysis revealed that the expression of genes in Profile 5 exhibited rhythmic fluctuations, and these genes (e.g., FAM21C, SRSF4, and TLR2A) were enriched in immune function and biological rhythm. The genes (e.g., MSMO1, ELOVL2, and HMGCR) in Profile 2 that were related to lipid metabolism also exhibited a rhythmic trend. A total of 845 differentially expressed genes (e.g., MSMO1 and FAM21C) were detected between light/dark conditions. Lipid metabolism and immune functions showed the most changes between the two conditions. Immune-related processes (e.g., autophagy) were more active in the light phase, while in the dark phase, lipid metabolism (e.g., sterol biosynthesis) was more active. Weighted gene coexpression network analysis revealed that the tan (including C1QA, TLR2A, and others) and cyan (including ELOVL2, IARS1, and others) modules were strongly associated with the hepatic circadian rhythm. Cosinor analysis revealed that 9 lipid-related genes (e.g., MSMO1, HMGCR1, and ELOVL2) and 11 immune-related genes (e.g., FAM21C, TLR4, and TLR2A) exhibited significant rhythmic expression. These findings revealed rhythmic changes in hepatic immune and lipid metabolism, providing important insights into the regulation of disease resistance and lipid deposition in chickens.