Effects of Lactobacillus curvatus HY7602-Fermented Antlers in Dexamethasone-Induced Muscle Atrophy

Round 1

Reviewer 1 Report

Jeon et al. used both in vitro and in vivo models of muscle atrophy to examine the efficacy of fermented antler (FA) extracts to prevent muscle atrophy. The use of dexamethasone treatment for both models was appropriate and allowed for good comparison between models. According to their report, they found that FA prevented muscle atrophy in vivo and provided evidence of reduced protein degradation and increased protein synthesis under these atrophic conditions in vitro. That said, there are some concerns that must be addressed for acceptance of this manuscript:

MAJOR CONCERNS

1) One of their groups (DEX+OXY) needs to be better explained. The purpose of this group is not clear and there lacks a substantial amount of data related to the outcome variables from this group throughout the text.

2) Throughout the written RESULTS, the investigators should take this opportunity to present some of the raw data. I expect to see significance values and at least relative/fold differences related to the effects observed in the groups compared to control (e.g. DEX reduced muscle mass by 10% (p = 0.02). 

3) The authors need to ensure that their results and discussion accurately reflect their findings. First, under section 3.8 of the RESULTS (and again in DISCUSSION line 517-518), the authors state that Sialic Acid "inhibited muscle atrophy." They do not have the data to support this. The only measures made were related to muscle degradation markers, so they can only conclude that the administration of sialic acid in vitro reduced the expression of these markers. This brings me to another MAJOR weakness, in that the authors present NO DATA (in this section or any other) of actual muscle atrophy in vivo. They only provide markers of protein synthesis and degradation. Although the model is an establish model of muscle atrophy, they provide no indication that their myotubes are smaller after DEX. Therefore, they cannot claim to observe atrophy in vitro, only changes in markers of protein synthesis/degradation. Similarly, in the DISCUSSION (line 407) they reference the efficacy of FA to enhance recovery. Recovery of what? There were not recovery measures of ANY kind and statements such as these must be removed.

4) Figures. The explanation of significance markers must be outlined for each figure/table. There is no indication of what their symbols (a, b, c) represent. In addition, the axis not starting at zero should be offset to provide clarity, and demonstrate a specific range of values. In figure 2, the authors need to provide significance for the time-course data. As written, there is none provided, suggesting that indeed there were NO differences (although the authors claim there are differences without providing any concrete data in the RESULTS paragraphs). In Figure 3, the GA/PLA complex (the authors never removed the plantaris, which lies next to the SOL as part of the posterior hindlimb GA/PLA/SOL complex) and SOL are pictured separately, but the muscle mass was pooled for quantification? The masses for each muscle/muscle group should be presented separately.

MINOR

1) Lines 18-19 and methods, the authors should more clearly outline that the DEX was administered IP, and they need to describe HOW the NFA, FA, OXY were administered orally. Was it in water, chow, via gavage?!

2) Throughout the text the authors use 'inhibition' too much, and often times inappropriately. In their editing process, they should consider interchangeable use of other terms like 'prevention' or 'attenuation'

3) Line 24, the authors state that FA-induced prevention of muscle atrophy correlated with a decrease in multiple factors, but they never correlated any variables. The terminology must reflect that. A correlation would provide a direct, quantifiable comparison, with an associated correlation co-efficient. They are related, or associated, but not correlated. 

4) Line 37, muscle don't reproduce. They can proliferate and divide, but it is not common to refer to muscles as having any 'reproductive properties.

4) Line 125, new sentence should start with capitalization

5) Line 141, calf thickness? This is not a common measure of muscle atrophy since it would reflect bone, connective tissue, and other fluids in the area. It would be interesting to see the authors correlate (actual correlation analysis) muscle fiber diameter and/or CSA to this muscle thickness measure.

6) Line 277, diameters are not 'shortest', but rather 'smallest'

7) Line 300, misspelling of 'antlres'

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Very interesting and important paper. Older population muscle fibers atrophy is very serious problem. The Authors in the previous study showed that L. curvatus HY7602-fermented deer antlers improved exercise performance in young mice and recovered muscle strength in middle-aged mice. However, the effects in the dexamethasone-induced muscle atrophy model have not yet been confirmed. In reviewed paper the effects of sialic acid on muscle atrophy have been shown. 

I think that the name "herbal" should not be used, as the substrate is not from herbs. Use the name "traditional". 

386-395 I think that this fragment is trivial and can be removed. 

396-425 This fragment should be transferred to the Introduction, also some parts are a repetition from the Introduction. 

531-533 Correct the sentence

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

My comments were adequately addressed