Alterations of the Human Gut Microbiota in Intrahepatic Cholestasis of Pregnancy

Abstract

Background and aims: Women with severe intrahepatic cholestasis of pregnancy (ICP) are at higher risks of fetal complications and without effective treatments. Changes in gut microbiota in pregnancy were found to be related to the altered intestinal bile acid composition, so we aimed to explore the alterations of microbiota in the gut of ICP patients.

Methods: A total of 90 women were recruited, including 45 ICP patients and 45 healthy controls. The gut microbiota communities of ICP group were compared to control group through 16S ribosomal RNA gene sequencing. The results were then confirmed by real-time polymerase chain reaction (PCR) and generalized linear model (GLM). Furthermore, we analyzed the relationships between microbiota and the severity of ICP.

Results: A total of seven genera and nine taxa with differential abundances between the ICP patients and the controls were identified. All of the seven genera were verified through real-time PCR, and three key genera Parabacteroides, Flavonifractor, and Megamonas were confirmed by using the GLM model. Further analysis found that the genera Escherichia_Shigella, Olsenella, and Turicibacter were enriched in the severe ICP group, the microbial gene function related to biosynthesis of unsaturated fatty acids and propanoate metabolism were also increased in them.

Conclusions: Overall, our study was the first in Asia to demonstrate an association between gut microbiota and ICP. Our findings would contribute to a better understanding of the occurrence of ICP.

Keywords: Escherichia_Shigella; Olsenella; Turicibacter; biosynthesis of unsaturated fatty acids metabolism; propanoate metabolism pathway; severe ICP.

Figure 1

α and β-diversity of fecal microbiota in patients with ICP and healthy control (CON) subjects. (A) Shannon and Simpson indices were used for α-diversity, and (B) Adonis analysis and a principle of coordinates analysis (PCoA) indices were used for β-diversity. Each box plot represents the median, interquartile range, minimum, and maximum values. No differences were detected either in the α-diversity or in the β-diversity indices of the gut microbiota between the two groups. Red represents the ICP group, and blue represents the healthy controls (CON).

Figure 2

Comparison of gut microbiota between the ICP patients and healthy individuals. (A) Taxonomic differences in the microbial 16S rRNA gene through LEfSe analysis. (B) The Heatmap of differential OTUs between the ICP patients and healthy individuals. The transverse clustering shows that the abundance of the phylotypes is similar in each sample, and the longitudinal clustering shows the similarity of the expression of all phylotypes among different samples, the closer the distance is, the shorter the branch length is. Blue represents the ICP group, and red represents the healthy group. (C) The relative abundance of the seven genera between the ICP and healthy controls were confirmed using real-time PCR. (D) The relative abundances of the same seven genera were validated in the other two independent groups of 30 ICP patients and 30 healthy individuals by real-time PCR. Blue scatter plot with error bars represents the ICP patients, and red scatter plot with error bars represents the healthy controls. Light blue and light red ones represent the new 30 ICP patients and 30 healthy controls, respectively.

Figure 3

Relationship between severity of ICP and microbiota. (A) Taxonomic differences in the microbial 16S rRNA gene through LEfSe analysis. (B) Significantly different KOs were detected in the microbiome of the mild and severe ICP groups. (C) The microbial gene functions related to the severity of ICP were detected in the level 3 KEGG pathways. KO, KEGG (Kyoto Encyclopedia of Genes and Genomes) orthologs; Blue, red, and green squares represent the severe ICP, mild ICP, and healthy controls, respectively.

Figure 4

Correlations between the genera and ICP clinical characteristics. (A) Heatmap of correlations. (B) Schematic diagram showing the main genera of the gut microbes that had a predicted ICP association. Enriched genera and higher chemical indicators were shown in blue, depleted genus and lower chemical and clinical indicators were shown in red. WG, Weight that gained during pregnancy; BMI, body mass index; Alb, albumin; TC, total cholesterol; HDL, high-density lipoprotein; ALT, alanine aminotransferase; CG, cholyglycine; and TBA, total bile acid. ⁺ p < 0.05, *p < 0.01.