Review for 10.1186/s12876-024-03483-6 (2024)

Title: The effect of propranolol on gastrointestinal motility and permeability in patients with
cirrhosis and significant portal hypertension
Version: 0 Date: 26 May 2024
Reviewer's report:
Thank you for asking me to review this manuscript.  The authors of the manuscript studied
the effects of propranolol on intestinal permeability, inflammation and bacterial overgrowth,
amongst other things.
1. Introduction, paragraph 2, lines 6-7: The sentence "However, clinical correlation of HVPG
and intestinal permeability...." is incorrect. Reference 27 of the manuscript was a study which
showed the effect of propranolol on HVPG and intestinal permeability.
2. Table 1, characteristics ascites: In this row, characteristic of ascites was listed as "no, mild,
medium and large". However, under Result column, there were only 3 (instead of 4) separate
data given, i.e., 4, 13 and 18 patients respectively. Please kindly clarify this.
3. Table 1, hemoglobin. I believe the unit for is incorrectly labelled as gr/dL instead of g/dL.
4. Table 2, rows 3-6: In these rows, the characteristics listed were Lactulose to D-Xylose
permeability. I suspect these refers to the individual Lactulose to D-Xylose levels detected in the
urine as described in Methods under Gastrointestinal permeability. It would be better to label
these as" _____ detected in urine" rather than "______ permeability" as the latter is confusing.
Please also provide the unit of measurement for all the substrates detected in the urine after oral
sugar drink test.
5. Continuous variables in this study were presented either as mean or median.  However, I note
that number of study participants in this study was small, n=35. When sample size is small, it is
very difficult to satisfy criteria for normality.  Could the authors kindly confirm that the variables
presented as mean were truly normally distributed which justified the use of parametric tests.
6. Table 2: Variables denoted by * were "median percentage + 95% CI", according to the
footnote. Could the authors clarify what is meant by that? If the variables were not normally
distributed, then the data should be presented as median and either the IQR or range in
parenthesis.
7. In this study, bacterial DNA was not detected in any patient before or after propranolol
treatment. I'm surprised with this finding as bacterial translocation can occur even in early
cirrhosis but is known to worsen with progressively more advanced liver disease. It also
predisposes patients to SBP. In this study, almost a third had Child Pugh C cirrhosis and more
than 50% had large ascites.  How many patients in this cohort had SBP? What was the detection
threshold or sensitivity of the test kit to detect bacterial DNA in this study? Can the authors
include these in the discussion.?
8. In this study, LPS was detectable pre- and post-NSBB while bacterial DNA was not. As
far as I know, LPS has a short half-life of 2 to 3 hours and is a less reliable test for bacterial
translocation. Can the authors explain the paradoxical finding in this study? It would be useful
to include this in the Discussion as well.
9. The authors performed subgroup analysis for OCTT, IP, inflammatory markers and BT.  How
did the authors define the increase or decrease in the tests for the above variables? Were they
based on specific threshold cut-off or % change of values comparing post- to pre-NSBB? Or
where they grouped into increase or decrease based on the absolute change as long as there
was any increase or decrease in the post-NSBB value compared to pre-NSBB? I think this is
important as any numerical change deemed increase or decrease by merely comparing to pre-
NSBB level may not be clinically significant and may be due to type I error since the sample
size is small and there was no control group which did not receive NSBB.
10. Under LPS and IL-6 subgroup analysis, the authors grouped the patients into those who
decreased vs. those who increased LPS/IL-6 levels. Given non-statistically significance of the
latter group (p=0.08 and 0.1), I think it is incorrect to label it as such. It would be more
appropriate to group them into decreased vs. no decrease.
11. In the last 2 rows of Tables 3 and 4, the variables were "Lactulose pre-NSBB" and "Lactulose
post-NSBB". This is confusing to the readers as lactulose is also an oral medication given
to patients with cirrhosis. Based on my understanding of the research protocol, it should be
"Lactulose detected in urine" pre- and post-NSBB. Please also include the unit of measurement.
12. In tables 3 and 4, many other variables listed do not have their unit of measurement.
13. In this study, there was no change in LPS and all the inflammatory markers before and after
NSBB when all patients were considered together, which contradicts results from reference 27.
Can the authors hypothesize why this was the case? Could this be just due to choice of statistical
tests, i.e. parametric vs non-parametric? Please include this in Discussion.
14. A novel finding from this study is that NSBB decreases gut bacterial translocation by
decreasing gut permeability through the paracellular pathways.  Do the authors have any
hypothesis on the molecular mechanism(s) of NSBB effect on paracellular pathways?  This
would be a useful discussion.
15.  Discussion, paragraph 5, first sentence on "window hypothesis".  It is incorrect that this
hypothesis is applies to the precompensated stage.  Firstly, there is no precompensated stage in
cirrhosis, instead it is either compensated or decompensated cirrhosis. Secondly, this hypothesis
is about the lack of benefit or potential harm of NSBB in the two extreme stages of cirrhosis -
very early cirrhosis, i.e. before development of CSPH, and in patients with very advanced liver
cirrhosis, e.g. refractory ascites.
16. Discussion, paragraph 5, second sentence:  I disagree with "...... we showed that a reduction
in portal pressure by NSBB treatment is associated with......".  There was no HVPG performed
in this study. Therefore,  the authors did not show that portal pressure was reduced by NSBB
in this study. After all, NSBB responders to propranolol is only in the range of 30-40%. All the
authors can conclude is that "....we showed that NSBB treatment is associated with.......".
17. As the authors alluded to in the last paragraph of Discussion, carvedilol is a more potent
NSBB compared to propranolol and is the preferred NSBB. Why did the authors choose
propranolol as the NSBB in this study instead of carvedilol ? This is especially so when
other authors have published similar studies with propranolol, but none have been studied on
carvedilol.