Review for 10.1186/1471-230X-8-40 (2008)

Reviewer's report
Title:Resveratrol inhibits nonalcoholic fatty liver disease in rats.
Version: 2Date:24 March 2008
Reviewer: Ralf Weiskirchen
Reviewer's report:
Bujanda and coworkers investigated the effect of resveratrol on hepatic injury
and expression of TNF-alpha production in an animal model of steatosis.
Therefore, three groups with twelve animals each were comparatively analysed.
One group (control) had free access to a regular rat chow diet for four weeks, the
second group was fed with a high carbohydrate-fat diet for four days and fasted
for the remaining three days for a period of four weeks (steatosis group), and the
last group was treated essentially as the second group but additionally received
oral doses of resveratrol (resveratrol group) every day.
The authors found that animals receiving resveratrol had lower fat deposition and
lower TNF-alpha levels. The authors conclude that resveratrol decreases fat
deposition by inhibition of TNF-alpha expression.
Major Compulsory Revisions
1. The authors conclude that the observed decrease of fat deposition in the
resveratrol group is mediated by inhibition of TNF-alpha expression. However,
this conclusion is pure speculation. Data is missing showing a direct link of
TNF-alpha expression and fat deposition. To demonstrate that the effect is
mediated via a TNF-alpha-dependent pathway, it would be necessary to
introduce a fourth group that received the high carbohydrate-fat diet, resveratrol
and repeated doses of TNF-alpha. Alternatively, it would be necessary to treat
the second group with TNF-alpha blocking agents. If the author’s conclusion is
correct, both experimental settings should give the same results as those
obtained in group three.
2. The authors state that the “hepatic index was calculated by dividing liver
weight by rat weight” (page 4). Obviously, the given indexes ranging from 3.9 to
4.5 (page 5) were factorized. Please tune the definition with the given values.
3. Measurements of MDA and TNF-alpha: (i) MDA. The authors state that the
content of lipid peroxide is expressed as nmol of MDA/g of wet weight, and the
total protein was determined by the Lowry method to correct the MDA level which
is expressed in terms of µmol/g protein (see page 4). However, in Figure 3B the
levels of MDA are given in µmol/L. (ii) TNF-alpha. Please provide the order
number of the R&D ELISA. In the legend to Figure 3A it must read “pg/mL”
instead of “pgl/mL”. Obviously, the authors measured TNF-alpha with an ELISA
system that is specific for murine TNF-alpha. According to the manufacturer’s
instructions, the murine TNF-alpha ELISAs from R&D show only “78%
cross-reactivity with rat TNF-alpha” and are not recommended for measurement
of rat TNF-alpha. This issue should be clarified.
4. page 5: “Inter-observer agreement was 0.84 and intra-observer agreement
was 0.79”. This fact is somewhat unexpected. Usually the intra-observer
agreement is higher than the inter-observer agreement. Please provide some
details how these values were obtained and shortly discuss this issue.
5. Discussion section, third paragraph: This paragraph is not coherent and must
be rephrased.
Minor Essential Revisions
1. page 3, line 16: What do the authors mean with “inhibition of Kupffer cells, and
adhesion molecules, inhibition of activated immune cells”? If the infiltration of
liver tissue with Kupffer cells or immune cells
2. page 3: The sections “Methods” and “Experimental procedures” should be
combined.
3. page 3, line 32: Please provide the exact notation of the chow rather than
stating “The diet contained no lipids (PANLAB, Barcelona, Spain).
4. page 3, citation in last sentence must read “Delzenne”
5. page 4: “Laboratory parameters such as AST, ALT, glucose and albumin were
measured using a computer-controlled chemistry analyzer.” The authors should
add some more information. What kind of analyzer was used? Were the
measurements performed at 25 degree or 37 degree? Are the AST values given
in U (as mentioned in the Result section) or IU (as mentioned in the Material
section)? In addition, ALT values are missing in the Result section.
6. page 4, line 34: “12.000 r/min or min”? Please correct.
7. Some subheadings in the Material and Method section should be added.
8. page 5: The authors refer to Table 2. It must read Table 1.
9. page 6, last paragraph: ALT values are given in IU. The correct unit of
measurement is IU/L. Please correct.
10. page numbers in Ref. 1 should be given in Journal’s style. In Ref. 5 it must
read “activity” instead of “acctivity”.
11. Figure 2: Space bars are missing. In addition an Oil Red O staining would be
more appropriate to estimate the content of lipid deposition.
12. Definitely, wording and grammar of this manuscript should be edited by a
native speaker. There are many typos that should be emended.
Discretionary Revisions
None declared
What next?: Reject because too small an advance to publish
Level of interest: An article of insufficient interest to warrant publication in a
scientific/medical journal
Quality of written English: Not suitable for publication unless extensively edited
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.