Editor's note
Most patients with acute-on-chronic liver failure (ACLF) exhibit varying degrees of cholestasis. Previous studies have shown that the artificial liver support system (ALSS) can improve the prognosis and prolong the survival of patients with ACLF compared with standard medical therapy alone. Similarly, studies have confirmed that the intestinal microbiota of ACLF patients is unbalanced. However, the specific effects of ALSS on the composition of the gut microbiota in these patients are still not fully understood. In addition, considering the complex interactions between gut microbiota, bile acids (BAs), and liver, the investigators conducted a study to elucidate the unique effects of ALSS on gut microbiota and serum BAs in ACLF patients. In addition, the study used relevant heat maps to visualize the relationship between gut microbiota, serum BAs, and clinical outcomes in ACLF patients, which is helpful for gaining insight into potential therapeutic targets for ACLF. The study was recently published in Hepatology International.
Background
Patients with ACLF often exhibit an imbalance in the gut microbiota, and BAs affect the composition of the gut microbiota. Previous studies have shown that ALSS can improve the prognosis and prolong the survival time of ACLF patients, but the effect of ALSS on the intestinal microbiota and serum BAs of ACLF patients is still unclear.
Methodology
The investigators conducted a prospective study that included a total of 51 participants with a diagnosis of ACLF. Based on the use of ALSS during the treatment period, the investigators divided these subjects into two groups: standard medical treatment group (SMT group, n=19) and ALSS plus SMT group (ALSS group, n=32). Blood and stool samples were collected from subjects on the day of admission and 14 days after treatment. Healthy control subjects (HC group, n=8) were also recruited and stool samples were collected. The researchers used 16S rRNA sequencing technology to sequence the intestinal microbiota and ultra-performance liquid chromatography/mass spectrometry to determine serum BAs.
Results
Compared with the SMT group, the ALSS group had higher liver inflammation indicators, especially alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels (P<0.05). There were no significant differences in other indicators, such as age, total bilirubin, and MELD scores (Table 1).
Table 1. Subjects baseline clinical characteristics (from the literature)
01
Effect of ALSS on intestinal microbiota
α-diversity analysis showed that the indicators of Chao 1, Shannon and Pielou_e in the ACLF group were significantly lower than those in the HC group. Compared with the SMT group, the ALSS group had a slight increase in the above indicators, but the difference was not statistically significant. In addition, the β diversity analysis based on the Bray-curtis distance algorithm showed that both the ACLF group and the HC group were significantly separated on the PCo1 and PCo2 axes (Fig. 1). There was no significant separation between the SMT group and the ALSS group on the PCo1 axis, but there was a certain separation on the PCo2 axis.
Based on the analysis of α-diversity and β-diversity, the abundance and diversity of intestinal microbiota in ACLF subjects decreased, and ALSS could improve the imbalance of intestinal microbiota in ACLF subjects to a certain extent (Fig. 1).
Figure 1. Effect of ALSS on the Abundance and Diversity of Gut Microbiota in ACLF Subjects (from the literature)
In order to further compare the differences in gut microbiota composition between the groups, the researchers used the average abundance correlation data of the top 20 genera to construct a heat map. The heat map showed that the ALSS group had relatively high abundances of beneficial bacterial genera, such as Parabacteroides_B, Ligilactobacillus, Lactobacillus, and Phocaeicola_A (Figure 2).
Figure 2. Microbial Abundance Correlation Cluster Heatmap (from literature)
Subsequently, the researchers further analyzed the differences in the relative abundance of species in the gut microbiota of the subjects at the genus level. The results showed that the relative abundance of Escherichia and Streptococcus was increased and the relative abundance of Collinsella decreased in the ACLF group compared to the HC group. This indicates that the composition of the intestinal microbiota in ACLF patients has changed, which is manifested by an overall increase in the harmful microbiota and an overall decrease in the beneficial microbiota. Comparing the ALSS group with the SMT group, the investigators observed higher relative abundances of Phocaeicola_A and Ligilactobacillus in the ALSS group, while lower relative abundance in Escherichia. This suggests that ALSS has a regulatory effect on gut microbiota composition (Figure 3).
Figure 3. Effect of ALSS on the composition of intestinal microbiota in subjects with ACLF (from literature)
02
Effect of ALSS on serum BAs
The investigators quantitatively analyzed the concentrations of 18 BAs in the serum samples of ACLF subjects before treatment (n=51) and in the serum samples (n=26) after 14 days of treatment. The results showed that the top five BAs with the highest BAs content were glycocholic acid (GCA), glycochenodeoxycholic acid (GCDCA), taurochenodeoxycholic acid (TCDCA), taurocholic acid (TCA), and glycoursodeoxycholic acid (GUDCA), accounting for more than 90% of the total BAs concentration (Fig. 4a). Principal component analysis showed that the post-treatment group had a higher degree of sample separation compared to the pre-treatment group. In addition, samples within the ALSS group were more clustered compared to the SMT group (Figure 5a).
Compared with the pre-treatment group, the concentrations of bile acid (CA), chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) in the post-treatment group were significantly increased (P<0.05) (Fig. 4b, c, f), and the concentrations of TCDCA and GCDCA decreased (P<0.05) (Fig. 5b, c). There was no significant difference between the concentrations of the remaining unconjugated and conjugated BAs, and the concentrations of total unconjugated and total conjugated BAs. Compared with the SMT group, the concentrations of UDCA, GUDCA and total unconjugated BAs in the ALSS group were significantly higher than those in the SMT group (P<0.05) (Fig. 4f, 5d, f).
There was no significant difference in the concentrations of total primary and total secondary BAs between the post-treatment group and the pre-treatment group. Similarly, there was no significant difference in the concentration of total primary and secondary BAs between the ALSS and SMT groups. This suggests that ALSS has no significant effect on the overall composition of primary and secondary BAs.
Compared with the pre-treatment group, the concentrations of total hydrophilic BAs and total hydrophobic BAs in the post-treatment group decreased significantly (P<0.05) (Fig. 5i, j), but the ratio of total hydrophilic BAs to total hydrophobic BAs increased (P<0.05) (Fig. 5k). Comparing the ALSS group with the SMT group, no difference in the concentration of total hydrophobic BAs and total hydrophilic BAs was observed.
In conclusion, ALSS can effectively increase the concentration of UDCA and GUDCA compared with SMT.
Figure 4. Effect of ALSS on serum unconjugated BAs in subjects with ACLF (from literature)
Figure 5. Effect of ALSS on Serologically Conjugated BAs and Various BAs Combinations in ACLF Subjects (from the literature)
Conclusions
Patients with ACLF exhibit an imbalance in the gut microbiota and abnormal BAs. The combination of ALSS and SMT is more effective in regulating intestinal microbiota imbalance and increasing UDCA and GUDCA concentrations compared to SMT alone. Correlation analysis showed that there was a significant correlation between gut microbiota and BAs.
The study identified the compositional characteristics of intestinal microbiota and serum BAs in ACLF patients, highlighting the effect of ALSS on intestinal microbiota and serum BAs.
参考文献：Zeng, Y., Gan, D., Zhang, K. et al. The impact of artificial liver support system on intestinal microbiota and serum bile acid profiles in patients with acute-on-chronic liver failure: a prospective cohort study. Hepatol Int (2024). https://doi.org/10.1007/s12072-024-10712-3