Hepatobiliary Thyroid Hormone Deficiency Impacts Bile Acid Hydrophilicity and Aquaporins in Cholestatic C57BL/6J Mice

Tuning of liver circadian transcriptome rhythms by thyroid hormone state in male mice

Thyroid hormones (THs) are important regulators of systemic energy metabolism. In the liver, they stimulate lipid and cholesterol turnover and increase systemic energy bioavailability. It is still unknown how the TH state interacts with the circadian clock, another important regulator of energy metabolism. We addressed this question using a mouse model of hypothyroidism and performed circadian analyses. Low TH levels decreased locomotor activity, food intake, and body temperature mostly in the active phase. Concurrently, liver transcriptome profiling showed only subtle effects compared to elevated TH conditions. Comparative circadian transcriptome profiling revealed alterations in mesor, amplitude, and phase of transcript levels in the livers of low-TH mice. Genes associated with cholesterol uptake, biosynthesis, and bile acid secretion showed reduced mesor. Increased and decreased cholesterol levels in the serum and liver were identified, respectively. Combining data from low- and high-TH conditions allowed the identification of 516 genes with mesor changes as molecular markers of the liver TH state. We explored these genes and created an expression panel that assesses liver TH state in a time-of-day dependent manner. Our findings suggest that the liver has a low TH action under physiological conditions. Circadian profiling reveals genes as potential markers of liver TH state.

Insights into the Function of Aquaporins in Gastrointestinal Fluid Absorption and Secretion in Health and Disease

Aquaporins (AQPs), transmembrane proteins permeable to water, are involved in gastrointestinal secretion. The secretory products of the glands are delivered either to some organ cavities for exocrine glands or to the bloodstream for endocrine glands. The main secretory glands being part of the gastrointestinal system are salivary glands, gastric glands, duodenal Brunner's gland, liver, bile ducts, gallbladder, intestinal goblet cells, exocrine and endocrine pancreas. Due to their expression in gastrointestinal exocrine and endocrine glands, AQPs fulfill important roles in the secretion of various fluids involved in food handling. This review summarizes the contribution of AQPs in physiological and pathophysiological stages related to gastrointestinal secretion.

AQP3-mediated activation of the AMPK/SIRT1 signaling pathway curtails gallstone formation in mice by inhibiting inflammatory injury of gallbladder mucosal epithelial cells

BACKGROUND

Inflammatory injury of gallbladder mucosal epithelial cells affects the development of cholelithiasis, and aquaporin 3 (AQP3) is an important regulator of inflammatory response. This study reports a mechanistic insight into AQP3 regulating gallstone formation in cholelithiasis based on high-throughput sequencing.

METHODS

A mouse model of cholelithiasis was induced using a high-fat diet, and the gallbladder tissues were harvested for high-throughput sequencing to obtain differentially expressed genes. Primary mouse gallbladder mucosal epithelial cells were isolated and induced with Lipopolysaccharides (LPS) to mimic an in vitro inflammatory injury environment. Cell biological phenotypes were detected by TdT-mediated dUTP Nick-End Labeling (TUNEL) assay, flow cytometry, Cell Counting Kit-8 (CCK-8) assay, and Trypan blue staining. In addition, enzyme linked immunosorbent assay (ELISA) determined the production of inflammatory factors in mouse gallbladder mucosa.

RESULTS

Whole-transcriptome sequencing data analysis identified 489 up-regulated and 1007 down-regulated mRNAs. Bioinformatics analysis revealed that AQP3 was significantly down-regulated in mice with cholelithiasis. AQP3 might also confer an important role in LPS-induced gallbladder mucosal injury. Overexpression of AQP3 activated the AMPK (adenosine monophosphate-activated protein kinase) / SIRT1 (sirtuin-1) signaling pathway to reduce LPS-induced inflammatory injury of the gallbladder mucosa epithelium, thereby ameliorating gallbladder damage and repressing gallstone formation in mice.

CONCLUSION

Data from our study highlight the inhibitory role of AQP3 in gallbladder damage and gallstone formation in mice by reducing inflammatory injury of gallbladder mucosal epithelial cells, which is achieved through activation of the AMPK/SIRT1 signaling pathway.