In this study, we explored the differential expression of lncRNAs and mRNAs between GSD patients and controls based on sequencing technology. Functional enrichment analysis of these differential genes showed that they were associated with cytochrome P450, and biosynthesis of steroid hormones, bile secretion, etc. which is closely related to the formation of gallstones.
For GSD, although some researchers have done transcriptome sequencing of gallbladder polyps and gallbladder stones on gallbladder epithelial tissue37, or constructed animal models of gallbladder stones in mice, using healthy mice as controls for sequencing and bioinformatics analysis. However, due to the similarity in the causes and mechanisms of the two diseases of gallbladder cholesterol polyps and gallbladder stones, and the animal model cannot completely replicate the human disease state, they are not the control group of the more ideal control group. The control group selected for this project was taken from patients undergoing surgical treatment for hepatic hemangiomas of liver Ⅳ-Ⅴ segments, which gallbladder tissue that could not be preserved during surgery. Preoperative examination shows that the size and morphology of the gallbladder are normal, the wall is thin and smooth, and the bile is well clear. Postoperative anatomical specimens observed no sediment deposition of bile, clear bile, and pathological examination confirmed as normal gallbladder tissue. Therefore, the control group sample selected for this project may be closer to the state of normal gallbladder in a healthy human body and more comparable.
In cells, cytochrome P450 is mainly distributed on the endoplasmic reticulum and intramitochondrial membrane, as a terminal oxygenase, involved in the synthesis of sterol hormones in the organism and other processes. Cytochrome P450 gene, cytochrome P450 family 7 subfamily members 1 (CYP7A1), CYP7B1, CYP27A1, etc. are involved in catalyzing various steps in cholesterol catabolism and bile acid synthesis38. As a regulator of cholesterol, steroid biosynthesis can control the contraction of gallbladder on the one hand and alter the expression of factors regulating cholesterol metabolism on the other, promoting the secretion of lithogenic stone bile and the formation of stones39. These biological processes and enrichment pathways are directly or indirectly involved in the regulation of gallbladder stone pathogenesis, including protein transport, lipid metabolism, which is in line with our expected results.
Subsequently, we used RT-qPCR to detect the top two up-regulated and down-regulated DEmRNAs and DElncRNAs, respectively, and the detection results were consistent with the sequencing results, indicating that the sequencing results were accurate and reliable. In addition, since the expression of these 8 DEmRNAs and DE-lncRNAs was most significantly different between the two groups, we speculate that they may play an important role in the occurrence and development of gallbladder stones. Of these, SFRP4 (secreted frizzled-related protein 4) is the largest member of the SFRP family and is strongly associated with many diseases, including obesity, type 2 diabetes, and malignancy40. Studies have shown an association between human SFRP4 expression and insulin sensitivity and triglyceride levels, and many studies have demonstrated that SFRP4 promotes the de novo synthesis pathway and glycolysis of liver fat in hepatocytes, resulting in decreased islet β cell function, thereby exacerbating lipid buildup and insulin resistance in the liver40–43. Lipid build-up and insulin resistance may lead to increased hepatic cholesterol secretion, decreased bile acid secretion, and dyskinesias of the gallbladder, leading to supersaturated bile formation, which may promote gallstone formation44. The results of this study showed a significant upward trend of SFRP4 in the stone group, and the difference was better, which further supported these conclusions. Therefore, we can speculate that SFRP4 has the potential as a biomarker of gallbladder stones, playing an important role in regulating human cholesterol balance.
Glutathione S-transferase(GST)are one of the most important liver detoxification enzymes in the body45 and also play an extremely important role in the metabolism of bile acids. As an important member of the cytoplasmic GSTs family, the Glutathione S-transferase alpha༈GSTA༉superfamily plays an important role in the metabolism of endogenous toxic compounds. GSTA can catalyze a wide range of substrates, bile acids themselves, as well as reactive oxygen species produced under cholestasis, non-polar compounds, etc., can be used as substrates. GSTA1-4 has been found to be significantly reduced in human obstructive cholestasis due to gallstone biliary obstruction46. In the process of gallstone formation and pathogenesis, there is a state of cholestasis, which is also confirmed by the significant downregulation of GSTA2 in the stone group in our findings. In the cholestasis caused by stones, the downregulation of liver detoxification enzymes will weaken the liver's treatment of toxic bile acids and aggravate the damage of liver cells, and the specific downregulation mechanism of GSTA2 in this process still needs to be further studied and explored.
In addition, downregulation of LINC01564 was associated with genomic instability and metabolic adaptation to liver cancer47,48, and SLC26A3 was associated with inflammatory bowel disease and infectious diarrhea49. The upward revision of COMP and HECW1-IT1 is more commonly reported in cancer. The regulatory role of these genes in the mechanism of gallstone formation may need to be further studied. The remaining genes have not been reported, and are awaiting further discoveries in the future.