Review for 10.1186/s12876-021-01790-w (2021)

Reviewer’s report
Title: 
Normalization of 
γ
-glutamyl transferase levels is associated with better metabolic control in
individuals with nonalcoholic fatty liver disease
Version: 
0 
Date: 
18 Dec 2020
Reviewer's report:
GENERAL COMMENT
The present study provides a valuable overview of the kinetics of liver enzymes in the course of treated
NAFLD. Several years ago, European researchers reported that GGT was a marker of insulin resistance (J
Hepatol. 2006 ;44:190-6). On this background, the present study is proof-of-concept evidence that the
normalization of this hepatobiliary enzyme is associated with improved metabolic phenotype including
uric acid, triglyceride and HOMA-IR (except for hypercholesterolemia) among those with NAFLD
submitted to either lifestyle changes or 
drug treatment. All in all this is a confirative study that weight loss
wil reduce those components of the Metabolic Syndrome which are associated with insulin resistance.
Although of potential interest, the study is amenable to major criticism in as far as the study deisgn is
concerned and data must be re-run in a sex-specific manner. Of concern, outdated cut-off of normality for
transaminases have been utilized and this implies further reworking of data based on updated ranges of
normality. References are used inappropriately.
SPECIFIC COMMENT
MAJOR
1. I think that, given that this study was conducted in adults, references pertaining to studies in children
should either not be cited or, at least should be commented indicating that "evidence from studies
conducted in children may possibly be translated to adults by inference". I suggest the former.
2. Ideally all statements should be adequately referenced and all unreferenced senteces should either be
deleted or supported by bibliographic citations.
3. Previous studies have clearly indicated that overreliance on liver enzymes is a mistake and this should
be highlighted also in the present paper (Hepatology. 2003;37:1286-92). Stated otherwise, the diagnosis
of NAFLD is not rule out by the presence of normal liver enzymes. Confirming this, the majority (>60%)
of patients recruited here had normal values of both trasaminases and GGT.
4. The present study is a proof-of concept research indicating that GGT is a sensitive marker of insulin
resistance in adults. This has previously been reported and these previous studies must be discussed ( J
Endocrinol Invest. 2005;28:333-9. J Hepatol. 2006;44:190-6. Diabetes Care. 2007;30:2355-61.
Diabetes. 2011 Jun;60(6):1660-7). Moreover these authors state that "Significant associations between
the normalization of GGT levels and target uric acid, triglyceride and HOMA-IR levels, but not
cholesterol levels, were observed in addition to weight loss". The reduction of total cholesterol makes
little sense: was HDL-cholesterol increased ? Was LDL-cholesterol decreased ? These are the important
thinks to say. In addition. These authors may be willing to discuss that a subset of patients may have their
GGT values reduced owing to reduced intake of alcohol, which was probably hidden at the baseline.
Along the same line, please correct the statistical model for smoking of tobacco ( J Atheroscler Thromb.
2010;17:476-85).
5. A robust line of research has identified NAFLD as a sexually dimorphic disease and it has been
suggested that data pertaining to NAFLD should be analyzed separately by sex (Hepatology.
2019;70:1457-1469). On these grounds, data must be re-run separately by men and women.
6. Also transaminases have a different range of normality based on sex and, importantly, the range of
normality used in the present study fails to accept the revised range of normality which has been identified
by a robust line of research (Ann Intern Med. 2002;137:1-10. Hepatology. 2010;51:1577-83. Aliment
Pharmacol Ther. 2012;36:560-8. Hepatology. 2012;55:447-54. 
J Clin Med. 2019;8:1445). In other
words, data must be re-run both separately by sex and with sex-specific cut-off values such as those
proposed by Prati in 2002.
7. The present statement "Nonalcoholic fatty liver disease (NAFLD) currently known as metabolic
associated fatty liver disease (MAFLD), is a clinical syndrome characterized by excess lipid storage in
hepatocytes, which has been acknowledged as the most common chronic liver disease worldwide" is
supported by a reference which was published 4 years before the name MAFLD was proposed by the
International panel. Therefore these authors may either add a second supporting reference or delete as
follows "currently known as metabolic associated fatty liver disease (MAFLD).
8. References 4. and 5. do not adequately support the following statement "NAFLD promotes
extrahepatic metabolic disturbances, including hypertension, hyperuricemia, hyperlipemia, hyperglycemia,
and eventually contributes to a poor prognosis, leading to cardiovascular disease, type 2 diabetes and other
metabolic compilations" and must be changes. In addition, reference 4. refers to children who, of course,
are less prone than adults to developing both T2D and CVD.
MINOR
1. "independent risk factors related to GGT normalization"--> associated with
2. I suggest providing the results of logistic regression analysis as graphs rather than tables
3. " metabolic control was an independent protective factor for persistent abnormal GGT levels in NAFLD
management." --> please, rephrase more clearly by highlighting the clinical (as opposed to statistical)
meaning of data.
4. I found the following sentence of interest and would like to read more about it, please add a supporting
reference "In patients with NAFLD and oxidative stress, increased bile pressure secondary to steatosis
(micro cholestasis) has been identified as an important 
pathogenic mechanism may help to explain its
higher specificity for NAFLD than ALT."
5. "Both GGT and ALT normalization were proposed as predictors of a histological
improvement in routine management of patients with NAFLD [10]." Please, note that reference 10 is a
study in children. I would suggest either deleting this sentence or supporting it with a study in adults given
that NAFLD in children has both similarities and (histological) differences with disease in adults
(Metabolism. 2016;65:1161-71) which may alter hepatobiliary enzymes .
6. "The dynamic association between liver biochemical markers and disease progression is complicated
and multifactorial [10]." Same as under point 5. above.
7. "the rectification of dyslipidemia, insulin resistance and uric acid levels may be necessary to achieve
GGT normalization, which may reduce inflammation and prevent the deterioration of fibrosis in patients
with NAFLD" Is this conclusion based on findings from the present study ? I do not think so given that no
liver biopsies were avaialble. Therefore the sentence must be either deleted or supporting by references.
Publons Reviewer Recognition
. Springer Nature can send verification of this review directly to Publons
(a subsidiary of Clarivate Analytics). If you would like to take advantage of this service, please click on
the “Yes” option below. Your name, email address, title of the reviewed manuscript, name of the journal,
and date of your review submission (the “Review Data”) will then be transmitted to Publons after the final
decision on the manuscript has been made. If you have already registered at Publons, they will notify you
of the receipt of this review and update your profile 
as per your settings and their policy. If you are not
registered with Publons, you will receive an email from them asking you to register in order for them to
be able to recognize your review on your new profile page. Publons may use the Review Data to generate
derivative metadata for the benefit of Publons and you as a reviewer, carefully considering the sensitivity
of such information. For example, Publons may verify your record as a reviewer by updating your profile
published on its webservice if you have registered for such service or help editors to identify candidate
reviewers. Please find the details of processing in Publons’ privacy policy
https://publons.com/about/terms
Yes
Declaration of competing interests
Please complete a declaration of competing interests, considering the
following questions:
1
. 
Have you in the past five years received reimbursements, fees, funding, or salary from an
organisation that may in any way gain or lose financially from the publication of this manuscript,
either now or in the future?
2
. 
Do you hold any stocks or shares in an organisation that may in any way gain or lose financially
from the publication of this manuscript, either now or in the future?
3
. 
Do you hold or are you currently applying for any patents relating to the content of the manuscript?
4
. 
Have you received reimbursements, fees, funding, or salary from an organization that holds or has
applied for patents relating to the content of the manuscript?
5
. 
Do you have any other financial competing interests?
6
. 
Do you have any non-financial competing interests in relation to this paper?
If you can answer no to all of the above, write 'I declare that I have no competing interests' below. If your
reply is yes to any, please give details below.
no competing interests to declare
Reviewer Publication Consent.
 I agree for my report to be made available under an Open Access
Creative Commons CC-BY License (
 http://creativecommons.org/licenses/by/4.0
) if this manuscript is
accepted for publication. Any comments that I do not wish to be included in the published report have
been included as confidential comments to the editor, which will not be published.
If you are not happy
for us to publish this report, please contact the editorial office before completing the review.
If you
wish, you can include your name in your published report. Please note you must decide whether to
include your name at the start of the process and confirm this decision whenever prompted. If you
change your decision later, we will not be able to publish your name.
I agree to the terms of the CC-BY 4.0 license; please 
do not
 publish my name with my report. (default)
Is the study design appropriate to answer the research question (including the use of appropriate controls),
and are the conclusions supported by the evidence presented?
No
Are the methods sufficiently described to allow the study to be repeated?
Yes
Is the use of statistics and treatment of uncertainties appropriate?
No
Is the presentation of the work clear?
No
Are the images in this manuscript (including electrophoretic gels and blots) free from apparent
manipulation?
No