Review for 10.1186/1471-230X-13-169 (2013)

Reviewer's report
Title:Role of serotonin in fatty acid-induced non-alcoholic fatty liver disease in
mice
Version: 1Date:1 March 2013
Reviewer: Bernhard Watzl
Reviewer's report:
Major Compulsory Revisions
The study investigated the potential effects of different dietary fat sources on the
pathogenesis of NAFLD. In order to understand the specific role of fatty acids it is
necessary to know the quantity and the specific type of fatty acids present in the
animal diet. As an example, C16:0 and C18:0 significantly differ in regard to their
metabolic effects. Unfortunately, the manuscript does not provide any detailed
information on the composition of fatty acids, which limits severely the
interpretation of the presented data. For example, in Table 1 only information
about crude fat is given without details on the quantity of SFA, MUFA, and PUFA
in the control diet. Which type of fatty acids contributed to the increase in the
intake of SFA compared to the control diet? The same is true for the composition
of MUFA and PUFA in the diets. Further, for the second experiment the
composition of the control diet is not given (standard diet?) and absolutely no
details on SFA and MUFA composition.
Statistics: The authors have used a one-way ANOVA to analyse their treatment
effects, although the intervention resulted in two effects. First, the switch from 6
% to 15 % fat, and second, the increase in SFA/MUFA/PUFA. These different
effects cannot adequately analysed by the one-way ANOVA. As an example,
Figures 2C-F suggest that there is a strong effect of the fat quantity with minor
effects of the fat quality. Further, the group size of n=5 may have been too low in
order to see more significant effects.
Table 2: It looks like that this table has included data from the two experiments
which is not acceptable in this way. Please revise this table.
Minor Essential Revisions
Lines 57, 209, 230, 261: "dietetic" versus "dietary".
Line 65: The references is missing.
Line 82: "inter peritoneal" versus "intraperitoneal".
Line 102: The manuscript reports a carbohydrate content of the experimental
diets of 50.1 % w/w, while Table 1 indicates only 40.3 % w/w.
Line 104: Unit correct? g/kg d
Line 108: Reference 24 does not describe the charcoal test.
Line 132: Typing error (THP1); TPH1 has not been introduced (tryptophan
hydroxylase 1)
Line 139: This section should also describe the methodology for assessing the
intestinal motility.
Lines 147-201: It would be helpful for the reader to more clearly separate the
presentation of the results between the two experiments.
Line 167: Reference 25 does not support the statement of this sentence.
Line 196: There is only one Figure 4. Therefore, there is no need to write “Figure
4A”.
Line 201: Please provide the data for the effect of TRP supplement in MUFA-fed
mice on the endotoxin levels (similar to the effect of SFA shown in Figure 4).
Lines 209f: The diets are not isocaloric when compared to the control diet.
Lines 226f: The statement that the effects of SFA and MUFA on fatty liver
disease and body weight could not be related to energy intake is questionable
because the diets were not isocaloric.
Lines 228ff: The reduction in occludin expression in the small intestine is not
specific for SFA but rather the consequence of the higher fat content of the feed.
Line 258: This statement needs a reference.
Line 400: There is no superscript "b" in this Table.
Lines 404-409: An explanation for superscript "c" is missing.
Line 424: Superscript "c" has not been used in Figure 3.
Table 1. Please add the information (% w/w). Further, please provide information
on the energy content of the diets. In addition, the reported numbers for crude
protein differ from those reported by Sniff for this diet (23,0 %).
Figure 1 A: The unit for triglycerides in liver is not correct (mg/dl).
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
However, I personally know most of the authors. Therefore, I would prefer that
my name as a reviewer is not made public.