Submited on: 15 Dec 2010 02:05:29 PM GMT
Published on: 16 Dec 2010 02:17:18 PM GMT
 

1 Is the subject of the article within the scope of the subject category? Yes
2 Are the interpretations / conclusions sound and justified by the data? Yes
3 Is this a new and original contribution? Yes
4 Does this paper exemplify an awareness of other research on the topic? Yes
5 Are structure and length satisfactory? Yes
6 Can you suggest brief additions or amendments or an introductory statement that will increase the value of this paper for an international audience? No
7 Can you suggest any reductions in the paper, or deletions of parts? No
8 Is the quality of the diction satisfactory? Yes
9 Are the illustrations and tables necessary and acceptable? Yes
10 Are the references adequate and are they all necessary? Yes
11 Are the keywords and abstract or summary informative? Yes
  • Other Comments:

    @font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }

    The authors have developed an NMR method to measure fat content in small tissue samples, as an alternative method to i.e. the more time consuming ether extraction. During this process they found a systematic sample-mass-dependent distortion. To solve this problem Kaerst et al developed a calibration equation to account for the weight bias. This calibration seems to be able to correct the raw data, thus allowing a reconstruction of the true fat content of the tissue samples.

     

    Kaerst and co-workers continue to prove the validity of their method by measuring fat content in muscle from two different mouse strains. Although the data presented here looks convincing it would have been interesting to see how the corrected values relate to the more traditional techniques, such as ether extraction.

     

    In the discussion, the authors speculate that the distortion could be caused by surrounding water molecules, affecting smaller samples more because of a bigger surface/volume. Is there a way of showing that this is the case? 

    The discussion continues with a section on filtering T2 relaxation times. This section would improve by adding a few sentences explaining the theory for the non-expert.

     

    In order to put this study in a wider context, a section on the clinical relevance of measuring fat content in different tissues would be of value.

     

    In conclusion, Kaerst and co-workers describe an interesting method to correct for a systemic error when measuring fat content in low-weight tissue, using NMR. I am looking forward to see whether this method will be used and validated by others.

  • Competing interests:
    No
  • Invited by the author to review this article? :
    Yes
  • Have you previously published on this or a similar topic?:
    No
  • References:
    None
  • Experience and credentials in the specific area of science:

    I have been working on mouse models for eating disorders for the past 15 years.

  • How to cite:  Johansen J E.Interesting method on how to measure fat content in small muscle biopses.[Review of the article 'A Novel Method For Measuring Of Fat Content In Low-weight Tissue: A NMR Study ' by Brockmann G].WebmedCentral 2010;2(2):WMCRW00493
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1 Is the subject of the article within the scope of the subject category? Yes
2 Are the interpretations / conclusions sound and justified by the data? Yes
3 Is this a new and original contribution? Yes
4 Does this paper exemplify an awareness of other research on the topic? Yes
5 Are structure and length satisfactory? Yes
6 Can you suggest brief additions or amendments or an introductory statement that will increase the value of this paper for an international audience? No
7 Can you suggest any reductions in the paper, or deletions of parts? No
8 Is the quality of the diction satisfactory? Yes
9 Are the illustrations and tables necessary and acceptable? Yes
10 Are the references adequate and are they all necessary? Yes
11 Are the keywords and abstract or summary informative? Yes
  • Other Comments:

    The importance of measuring fat content in low-weight tissue for breeding research is obvious as are the benefits of a method that is fast, cheap and repeatable. In principle NMR spectroscopy combines these advantages thus making it an ideal method. Unfortunately, for low-weight samples measurements suffer from distortions. Now Kaerst and colleagues have shown how these distortions, due to its systematic nature, can be corrected thus allowing for a satisfactory reconstruction of the true fat content of tiny samples weighing no more than 50 mg. Illustration 1 shows both distortion effects (left panel) and reconstruction (right panel). The visual impression of good reconstruction efficiency is corroborated by statistical analyses.

    They also show that two mouse strains can be differentiated by their respective intramuscular fat content after correction. Illustration 3 though made me wonder whether this separation was already possible before correction, albeit with erroneous values. Is this impression wrong? If not, it would be interesting to find a data set where the differentiation is only possible after applying the correction. This situation could occur since prior to correction the within-group (strain) variability might be dominated by variability of low-weight samples and be even larger than across-group (strain) variability reflecting different intramuscular fat content.

    The explanation of distortion by adsorbed water molecules and the surface/volume ratio sounds interesting. Wouldn't that suggest an inverse scaling with a linear dimension, hence, with z^alpha

    where alpha=1/3 (or larger for fractal samples)? What was the reason for fixing alpha=1 in the regression model? If there were systematic components of distortion left after using Eq.2 these might be removed using a different exponent, e.g. alpha=1/3. The authors could give it a quick try.

    Explaining the dependence of NMR measurements y on the true fat content x through decomposing any component of the material, except the lipids, by drying left me perplexed. One or two more sentences might be of help to the innocent.

    In conclusion, the correction method put forward by Kaerst et al., indeed, extends the use of NMR spectroscopy for fat content determination to low-weight samples and thus might be a valuable tool for a wide range of research questions.

  • Competing interests:
    I have no competing interest(s).
  • Invited by the author to review this article? :
    Yes
  • Have you previously published on this or a similar topic?:
    No
  • References:
    None
  • Experience and credentials in the specific area of science:

    I am a theoreticval physicist working in an interdisciplinary institute on biomathematical models with a focus on stochastic processes and statistical modeling

  • How to cite:  Freund J A.A valuable tool for a wider range of research questions - retry regression with modified model (different exponent)[Review of the article 'A Novel Method For Measuring Of Fat Content In Low-weight Tissue: A NMR Study ' by Brockmann G].WebmedCentral 2010;2(1):WMCRW00363
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1 Is the subject of the article within the scope of the subject category? Yes
2 Are the interpretations / conclusions sound and justified by the data? Yes
3 Is this a new and original contribution? Yes
4 Does this paper exemplify an awareness of other research on the topic? Yes
5 Are structure and length satisfactory? Yes
6 Can you suggest brief additions or amendments or an introductory statement that will increase the value of this paper for an international audience? Yes
7 Can you suggest any reductions in the paper, or deletions of parts? Yes
8 Is the quality of the diction satisfactory? Yes
9 Are the illustrations and tables necessary and acceptable? Yes
10 Are the references adequate and are they all necessary? Yes
11 Are the keywords and abstract or summary informative? Yes
  • Other Comments:

     

    It is a good method in measuring the fat content in small tissue by NMR. This study can be used  in other researches such as Physiology or Pathology.

  • Competing interests:
    no
  • Invited by the author to review this article? :
    No
  • Have you previously published on this or a similar topic?:
    Yes
  • References:
    Yan Y. et al. Resistance of alcat1 null mice to high fat diet induced obesity and impaired glucose tolerance. (in print)2011.
  • Experience and credentials in the specific area of science:

     

    I have worked on a project of the mechanisms of obesity and type II diabetes using mice model. It is important to measure the tissue fat content in living animals or tissues in my project.  

  • How to cite:  Yan Y .A review of A Novel Method For Measuring Of Fat Content In Low-weight Tissue: A NMR Study [Review of the article 'A Novel Method For Measuring Of Fat Content In Low-weight Tissue: A NMR Study ' by Brockmann G].WebmedCentral 2010;1(12):WMCRW00307
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1 Is the subject of the article within the scope of the subject category? Yes
2 Are the interpretations / conclusions sound and justified by the data? Partly
3 Is this a new and original contribution? Yes
4 Does this paper exemplify an awareness of other research on the topic? No
5 Are structure and length satisfactory? Yes
6 Can you suggest brief additions or amendments or an introductory statement that will increase the value of this paper for an international audience? Yes
7 Can you suggest any reductions in the paper, or deletions of parts? No
8 Is the quality of the diction satisfactory? Yes
9 Are the illustrations and tables necessary and acceptable? Yes
10 Are the references adequate and are they all necessary? Yes
11 Are the keywords and abstract or summary informative? Yes
  • Other Comments:

    Mr Kaerst and colleagues suggest an interesting approach to an age old problem, "how does one determine accurately tissue fat content?" The authors decided to optimize their system by taking chicken and pig meat, scaping off ornamental fat and determine fat content by the proton NMR approach. At lower tissue weight levels they found incongruity between repeated measurements of the same sample and fat levels. One claim they made was that surrounding water protons caused contaminated readings. They tried to correct this by a mathamatical approach. Why not use a Carbon based NMR approach which would completely eliminate the contibution of water in any of the samples.

    Secondly, in obesity, fat levels on and in the tissues all are significantly important in any arrising disease state. Furthermore, any obese individual (animal or person) of similar "Body Mass Index" (MBI) a standard measure of obesity, can have varying ammounts of "ornamental" (fat attached to tissues), "viseral" (mesocrine fat) and "subcutaneous" fat. Apparently the subcutaeous fat while most visable usually contributes least of the 3 forms to the resulting obesity-disease  state. Conseqently global measurement of fat usually is not always the best way to go if future disease status is to be determined. Hence the determination of fat levels in a particlular muscle biopsy, may yield biologically less informative information, by itself.

    Finally, a lack of an introduction to the levels of fat in different anatomic locations and their importance to the general obesity discussion would add a lot to the introduction of this article. Furthermore, the addition of how the "new" approach to measureing fat could be applied to other locations in the body in a meaningful way would round out the dissussion in this manuscript.

     

    I would also like to see more data presented as illustrations and/or tables, which I felt lacking in this paper.   

  • Competing interests:
    No
  • Invited by the author to review this article? :
    No
  • Have you previously published on this or a similar topic?:
    No
  • References:
    None
  • Experience and credentials in the specific area of science:

    I am head of a research division that wishes to apply a gene therapy approach to the human condition. One of major projects of interest is the problem of human obesity. A number of publications on this is now starting the publication process. Consequently the contribution of accurate human fat tissue measurement, while important needs to address a more global concern.

  • How to cite:  Weisinger G .Maybe carbon based NMR would be a better approach.[Review of the article 'A Novel Method For Measuring Of Fat Content In Low-weight Tissue: A NMR Study ' by Brockmann G].WebmedCentral 2010;1(12):WMCRW00261
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