Gut dysbiosis and mortality in hemodialysis patients

Gut dysbiosis, characterized by decreased microbial diversity, promotes
inflammation. Persistent inflammation plays a pathogenic role in
complications of chronic kidney disease (CKD). However, little is known
about the relationship between gut dysbiosis and adverse outcomes in
patients with CKD. First, we examined the association of microbial
diversity with all-cause mortality in CKD patients receiving hemodialysis
(n=109). The microbial composition of fecal samples was profiled by means
of 16S ribosomal RNA gene sequencing. Microbial diversity was calculated
using the Simpson index. Participants were stratified into higher- (above
the median) and lower-diversity (below the median) groups and were
followed up for a median of 2.1 years. Kaplan-Meier analyses revealed a
significant association between higher diversity and a lower risk of death
(log-rank P=0.015). After adjustment for patient characteristics and
comorbid conditions, the risk of death among patients with higher
diversity was 74% lower than that among patients with lower diversity
(hazard ratio, 0.26; 95% CI, 0.07 to 0.95). Next, in a matched
case-control study, we compared the microbial composition between
nonsurvivors and survivors who were matched 1:4 for age and sex. We
observed significantly lower values of microbial diversity and higher
levels of proinflammatory cytokines among nonsurvivors (n=14) than
survivors (n=56). Specifically, the relative abundance of Succinivibrio
and Anaerostipes, two short-chain fatty acid-producing bacteria, was
markedly reduced in nonsurvivors compared with survivors. In conclusion, a
unique gut microbial composition is associated with an increased risk of
mortality among hemodialysis patients and may be used to identify subjects
with a poor prognosis.