Rifaximin-α reduces gut-derived inflammation and mucin degradation in cirrhosis and encephalopathy: RIFSYS randomised controlled trial

BACKGROUND & AIMS

Rifaximin-α is efficacious for the prevention of recurrent hepatic encephalopathy (HE), but its mechanism of action remains unclear. We postulated that rifaximin-α reduces gut microbiota-derived endotoxemia and systemic inflammation, a known driver of HE.

METHODS

In a placebo-controlled, double-blind, mechanistic study, 38 patients with cirrhosis and HE were randomised 1:1 to receive either rifaximin-α (550 mg BID) or placebo for 90 days.

PRIMARY OUTCOME

50% reduction in neutrophil oxidative burst (OB) at 30 days.

SECONDARY OUTCOMES

changes in psychometric hepatic encephalopathy score (PHES) and neurocognitive functioning, shotgun metagenomic sequencing of saliva and faeces, plasma and faecal metabolic profiling, whole blood bacterial DNA quantification, neutrophil toll-like receptor (TLR)-2/4/9 expression and plasma/faecal cytokine analysis.

RESULTS

Patients were well-matched: median MELD (11 rifaximin-α vs. 10 placebo). Rifaximin-α did not lead to a 50% reduction in spontaneous neutrophil OB at 30 days compared to baseline (p = 0.48). However, HE grade normalised (p = 0.014) and PHES improved (p = 0.009) after 30 days on rifaximin-α. Rifaximin-α reduced circulating neutrophil TLR-4 expression on day 30 (p = 0.021) and plasma tumour necrosis factor-α (TNF-α) (p <0.001). Rifaximin-α suppressed oralisation of the gut, reducing levels of mucin-degrading sialidase-rich species, Streptococcus spp, Veillonella atypica and parvula, Akkermansia and Hungatella. Rifaximin-α promoted a TNF-α- and interleukin-17E-enriched intestinal microenvironment, augmenting antibacterial responses to invading pathobionts and promoting gut barrier repair. Those on rifaximin-α were less likely to develop infection (odds ratio 0.21; 95% CI 0.05-0.96).

CONCLUSION

Rifaximin-α led to resolution of overt and covert HE, reduced the likelihood of infection, reduced oralisation of the gut and attenuated systemic inflammation. Rifaximin-α plays a role in gut barrier repair, which could be the mechanism by which it ameliorates bacterial translocation and systemic endotoxemia in cirrhosis.

CLINICAL TRIAL NUMBER

ClinicalTrials.gov NCT02019784.

LAY SUMMARY

In this clinical trial, we examined the underlying mechanism of action of an antibiotic called rifaximin-α which has been shown to be an effective treatment for a complication of chronic liver disease which effects the brain (termed encephalopathy). We show that rifaximin-α suppresses gut bacteria that translocate from the mouth to the intestine and cause the intestinal wall to become leaky by breaking down the protective mucus barrier. This suppression resolves encephalopathy and reduces inflammation in the blood, preventing the development of infection.

The intellectual disability PAK3 R67C mutation impacts cognitive functions and adult hippocampal neurogenesis

The link between mutations associated with intellectual disability (ID) and the mechanisms underlying cognitive dysfunctions remains largely unknown. Here, we focused on PAK3, a serine/threonine kinase whose gene mutations cause X-linked ID. We generated a new mutant mouse model bearing the missense R67C mutation of the Pak3 gene (Pak3-R67C), known to cause moderate to severe ID in humans without other clinical signs and investigated hippocampal-dependent memory and adult hippocampal neurogenesis. Adult male Pak3-R67C mice exhibited selective impairments in long-term spatial memory and pattern separation function, suggestive of altered hippocampal neurogenesis. A delayed non-matching to place paradigm testing memory flexibility and proactive interference, reported here as being adult neurogenesis-dependent, revealed a hypersensitivity to high interference in Pak3-R67C mice. Analyzing adult hippocampal neurogenesis in Pak3-R67C mice reveals no alteration in the first steps of adult neurogenesis, but an accelerated death of a population of adult-born neurons during the critical period of 18-28 days after their birth. We then investigated the recruitment of hippocampal adult-born neurons after spatial memory recall. Post-recall activation of mature dentate granule cells in Pak3-R67C mice was unaffected, but a complete failure of activation of young DCX + newborn neurons was found, suggesting they were not recruited during the memory task. Decreased expression of the KCC2b chloride cotransporter and altered dendritic development indicate that young adult-born neurons are not fully functional in Pak3-R67C mice. We suggest that these defects in the dynamics and learning-associated recruitment of newborn hippocampal neurons may contribute to the selective cognitive deficits observed in this mouse model of ID.

Alterations in Gut Microbiome in Cirrhosis as Assessed by Quantitative Metagenomics: Relationship With Acute-on-Chronic Liver Failure and Prognosis

BACKGROUND AND AIMS

Cirrhosis is associated with changes in gut microbiome composition. Although acute-on-chronic liver failure (ACLF) is the most severe clinical stage of cirrhosis, there is lack of information about gut microbiome alterations in ACLF using quantitative metagenomics. We investigated the gut microbiome in patients with cirrhosis encompassing the whole spectrum of disease (compensated, acutely decompensated without ACLF, and ACLF). A group of healthy subjects was used as control subjects.

METHODS

Stool samples were collected prospectively in 182 patients with cirrhosis. DNA library construction and sequencing were performed using the Ion Proton Sequencer (ThermoFisher Scientific, Waltham, MA). Microbial genes were grouped into clusters, denoted as metagenomic species.

RESULTS

Cirrhosis was associated with a remarkable reduction in gene and metagenomic species richness compared with healthy subjects. This loss of richness correlated with disease stages and was particularly marked in patients with ACLF and persisted after adjustment for antibiotic therapy. ACLF was associated with a significant increase of Enterococcus and Peptostreptococcus sp and a reduction of some autochthonous bacteria. Gut microbiome alterations correlated with model for end-stage liver disease and Child-Pugh scores and organ failure and was associated with some complications, particularly hepatic encephalopathy and infections. Interestingly, gut microbiome predicted 3-month survival with good stable predictors. Functional analysis showed that patients with cirrhosis had enriched pathways related to ethanol production, γ-aminobutyric acid metabolism, and endotoxin biosynthesis, among others.

CONCLUSIONS

Cirrhosis is characterized by marked alterations in gut microbiome that parallel disease stages with maximal changes in ACLF. Altered gut microbiome was associated with complications of cirrhosis and survival. Gut microbiome may contribute to disease progression and poor prognosis. These results should be confirmed in future studies.

Effects of initial body mass index on development of gestational diabetes in a rural Sri Lankan population: A case-control study

AIM

High pre-pregnancy body mass index (BMI) and excessive pregnancy weight gain lead to higher incidence of gestational diabetes mellitus (GDM). Aim of the study was to assess the effects of initial BMI and pregnancy weight gain on development of GDM in a rural Sri Lankan population. It was also hypothesized that these effects could be more pronounced in shorter mothers.

METHODS

A case-control study was conducted at two rural hospitals in Sri Lanka. A case was defined as a pregnant mother admitted for the completion of pregnancy and diagnosed to have GDM (n=99). A similar group of mothers without GDM were recruited as controls (n=336). Data were collected through health records and direct interviews.

RESULTS

Mean age of GDM and non-GDM mothers were 32.8 years 28.1 years, respectively. High pre-pregnancy BMI was a significant risk for GDM, with a rising trend with increasing BMI. In contrast to underweight mothers, the risk increases from normal weight [odds ratio (OR)=6.6, 95% confidence interval (CI) 2.2-19.4, p<0.01], overweight (OR=17.1, 95% CI 5.8-49.9, p<0.01) and to obese (OR=32.4, 95% CI 10.0-104.5, p<0.01). There was no significant difference in weight gain across mother's height groups. Height or leg length did not show an association with GDM. Family history of diabetes and past GDM were associated with GDM. GDM mothers had higher likelihood for cesarian deliveries, and babies with higher birth weight.

CONCLUSION

The pre-pregnancy BMI was the most important modifiable risk factor for GDM, and it should be the main preventive measure.

Bone marrow stem cell and progenitor response to injury

Hematopoietic stem cells represent a long term reservoir of cells to populate blood with multiple formed cells. These hematopoietic stem cells proliferate and mature into lymphoid, erythroid, and myeloid precursor cells, with the balance of these cell populations modulated by major thermal injury, with or without sepsis. Recent studies indicate that thermal injury shifts this balance to favor the monocyte/macrophage lineage at the expense of neutrophil production. The mechanisms for these changes are now being elucidated with the results of clinical importance, because understanding the dynamics of the different precursor pools could be used to identify patients at greater risk for systemic inflammatory sequelae following major thermal injury.

Use of water-miscible retinyl palmitate as markers of chylomicrons gives earlier peak response of plasma retinyl esters compared with oil-soluble retinyl palmitate

Delayed peak response of plasma retinyl esters (RE) relative to plasma triacylglycerols (TAG) and apolipoprotein (Apo) B-48 responses following a fat load supplemented with vitamin A raised doubts about the use of vitamin A to label dietary-derived lipids and lipoproteins. The present study compared the use of water-miscible and oil-soluble retinyl palmitate (RP) as markers of dietary-derived lipoproteins in healthy subjects along with the measurements of postprandial plasma TAG and ApoB-48 responses to investigate whether the delayed peak response observed was due to delayed intestinal output of RE from oil-based solutions. Nine healthy female subjects were given a standard test meal containing a dose (112 mg) of RP in either water-miscible or oil-soluble form in random order, on two separate occasions after a 12 h overnight fast. The results showed that the mean plasma RE concentrations reached a peak significantly later than mean plasma TAG and ApoB-48 concentrations when oil-soluble RP was consumed, whereas plasma RE peaked earlier relative to plasma TAG and ApoB-48 responses when water-miscible RP was used. The results suggested a more rapid absorption with a significantly higher and earlier peak response of plasma RE when water-miscible RP was consumed. This was in contrast to the delayed initial appearance and later sustained higher concentrations of plasma RE during the late postprandial period when oil-soluble RP was consumed. The RE response to the water-miscible RP showed better concordance with plasma TAG response than that of oil-soluble RP.

5,5-Diaryl-2-amino-4-pentenoates as novel, potent, and selective glycine transporter type-2 reuptake inhibitors

A novel series of 5,5-diaryl-2-amino-4-pentenoates was synthesized and found to be potent and selective glycine transporter type-2 reuptake inhibitors.