Review for 10.1186/s12876-019-1040-y (2019)

Reviewer ’s report  
 
Title: Low Vitamin D Level Was AssociatedWith Metabolic Syndro me And High Leptin Level 
In Subjects With Nonalcoholic Fatty Liver Disease: A Community -based Study  
 
Version: 0 Date: 09 May 2018  
 
Reviewer: Ronette Lategan -Potgieter  
 
Reviewer's report:  
 
Congratulations on a comprehensive study, for which I would recommend a change in focus 
(according to the aim of the study)  
 
Language editing is highly recommended, although a certificate was provided.  
 
Specific comments include  
 
Line 
1-83: The title: 'Low Vi tamin D Level Increases the Risk of Metabolic Syndrome in Subjects 
with Nonalcoholic Fatty Liver Disease: A Community -based Study does not align with the aim 
of the study "to evaluate the association between serum vitamin D levels and nonalcoholic fatty 
liver disease (NAFLD) parameters, including metabolic syndrome risk and hepatic steatosis".  
The classic question of which came first - the chicken or egg needs to be answered to prevent 
confusion between cause and symptom when not providing sufficient scien tific evidence. A 
more 'conservative' title could be considered based on the findings of this study.  
 
Revisit second sentence of methods in abstract - "All subjects participated in a demographic 
survey to exclude alcohol abuse, blood testing and abdominal u ltrasonography (US)" - does not 
make sense without necessary verbs added.  
 
 
 
The results: "Subjects with serum vitamin D deficiency or insufficiency had a higher risk for 
metabolic syndrome than those with sufficient vitamin D levels [deficiency vs. sufficien cy, 
adjusted odds ratio (OR) =1.860 (95% CI=1.234 -2.804), P=0.003; insufficiency vs. sufficiency, 
adjusted OR=1.669 (95% CI=1.237 -2.251), P=0.001]. Similarly, subjects in the lowest quartile 
of vitamin D had a higher risk for metabolic syndrome than those in the highest quartile of 
vitamin D (OR= 2.792, 95% CI=1.719 -4.538, P<0.001)" would make more sense if reported 
objectively as the difference in Vit D levels between the two groups. Cause is implicated, which 
is not explicitly indicated and explained as t he case.  
 
Only the last sentence of the results is linked to the aim - consider language editing. I observed 
that a language certificate was issued, but the manuscript is still difficult to read because of 
language errors and sentence construction.  
 
The con clusion cannot be made from the results (first part of the conclusion) - can be seen as the 
other way around if biochemical background is not provided.  
 
88-110: The explanation of a causal relationship between vitamin D and MS is not 
provided to support the  motivation for the study.  
114: add reference, method or accept normal aging?  
116: serum study - please indicate for what?  
116-125: - consider to rather list  
Please check language (single, plural, addition of words, etc)  
133: glucose? Total Vitamin D?  
137: Consider to move to after the sentence starting in 138.  
140-142 - first part of the study methods.  
169: Were DM included/ excluded in study - indicate earlier in methods  
172 - how was this applied in the study - quartiles or specific values used?  
176 - just recheck recommendations - 88/89 cm / 35 in ?  
191 - did the study include African American participants? - if the case, waist circumference 
reference value also needs to adapt.  
210 - motivate and explain why adjustments were made for the specific confou nders  
211 - Sure about SPSS version - it is quite old?  
214-218 - relate to information in inclusion/ exclusion criteria  
Please correct language….  
224 - control or non -NAFLD group?  
225-233 - not expected? Participants grouped according to symptoms will look different if 
looking at a syndrome with interrelated symptoms.  
240-245 - the study corrected for factors included in the classification of MS - important to 
explain the interactio n and role. Important to explain the production of vitamin D in the body 
with relation to adiposity to clarify results.  
282-285 - This should be explained in the introduction to set the reason for the study.  
289 - Important to discuss the link between lept in, body fat and vitamin D to prevent confusion if 
the study focus on this association.  
300-301 - Please consider the link between adiposity and dermal Vitamin D production - in other 
words result vs risk?  
329-330 - Should mention in methods section.  
334-337 - Consider again the conclusion based on risk or result.  
References - 2010 Institutes of Medicine recommendations for Vitamin D can be included.  
Tabel 1 - careful for selecting two groups based on differences and then indicate p -values.  
 
A different foc us of this study would be of more value - reporting on the original aim of the 
study. The introduction should include much more background (biochemical) if the current focus 
of the publication is followed.  
 
 
 
 
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
No 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Unable to assess  
 
Are the conclusions drawn adequatel y supported by the data shown?  
If not, please explain in your comments to the authors.  
 
No 
 
Are you able to assess any statistics in the manuscript or would you recommend an  
additional statistical review?  
If an additional statistical review is recommended, p lease specify what aspects require further  
assessment in your comments to the editors.  
 
I am able to assess the statistics  
 
Quality of written English  
Please indicate the quality of language in the manuscript:  
 
Needs some language corrections before being pub lished  
 
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 f or 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.  
 
I declare that I have no competing interests  
 
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