Nutraceutical and Probiotic Approaches to Examine Molecular Interactions of the Amyloid Precursor Protein APP in Drosophila Models of Alzheimer’s Disease

Round 1

Reviewer 1 Report

It is a very interesting article, although it should be improved on a number of points:
a) A table with the nutraceuticals compounds should be added. Another table with synthetic inhibitors.
b) Comment on the manuscript the Oligomannate compound, which is derived from an extract of marine brown algae. It is thought to modulate the connection between the microbiome and the brain.
c) Add the reference in the manuscript.
  A Chronological Review of Potential Disease-Modifying Therapeutic Strategies for Alzheimer's Disease. Ettcheto M, Busquets O, Espinosa-Jiménez T, Verdaguer E, Auladell C, Camins A. Curr Pharm Des. 2020; 26 (12): 1286-1299.

Author Response

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Reviewer 2 Report

In this manuscript Vonhoff and coworkers review the current literature inherent to the potential use of natural compounds and probiotics in the regulation of APP levels and functions.

The manuscript is well organized and clearly written. Likely, it would benefit from the addition of several figures, schemes and/or tables. As an example, it could be nice to add a figure explaining the amyloidogenic cleavage pathway of APP. Moreover, people always like to see chemical formulas of the molecules described in the text.

I also suggest to add silibyins in the list of nutraceuticals with attractive anti AD properties (see eg. ACS Chem. Neurosci. 2017, 8, 8, 1767–1778).

 

Author Response

Reviewer 2:

In this manuscript Vonhoff and coworkers review the current literature inherent to the potential use of natural compounds and probiotics in the regulation of APP levels and functions.The manuscript is well organized and clearly written.

--We thank the reviewer for their kind comments and appreciation of our manuscript.

Likely, it would benefit from the addition of several figures, schemes and/or tables. As an example, it could be nice to add a figure explaining the amyloidogenic cleavage pathway of APP. Moreover, people always like to see chemical formulas of the molecules described in the text.

--We thank the reviewer for the suggestion. As such, wehave added a table describingthe main nutraceutical compounds included in our manuscript, includingtheir chemical formulas and additionalproperties(Table 1).The idea of includinga figuredescribing the amyloidogenic pathway is a fair one. However, we decided not to include such a diagram, as it is depicted in numerous other reviewarticlesand it may emphasize the backgroundsection of our manuscript, diverting the reader’s attention from the main focus of our manuscript (which was the concern of another reviewer).

I also suggest to add silibyinsin the list of nutraceuticals with attractive anti AD properties (see eg. ACS Chem. Neurosci. 2017, 8, 8, 1767–1778).

--The reviewer is absolutely correct that silybins are an interesting and promising compound. Therefore,we included silybin Bin our table,andadded it to our list of promising compoundsas suggested (line420).

Reviewer 3 Report

The manuscript reviews nutraceutical and probiotic approaches to examine molecular interactions of the amyloid precursor protein APP in Drosophila Alzheimer’s disease models. It has a number of shortcomings:

1. The word ‘Drosophila’ should be added to the title.
2. The data presented for drosophila models address the construct validity. The authors need to point out that there is zero evidence for these models having any predictive validity.
3. The chemical structures of the nutraceuticals described should be presented.
4. Some comment needs to be made about the ability of the nutraceuticals described to cross the blood brain barrier.
5. There is no mention of the concentration/dose of the nutraceuticals described to produce the effects described. This needs to be corrected.
6. The three cardinal neuropathologist changes of Alzheimer’s disease are: (i) the formation of neuritic plaques, : (ii)  the formation of neurofibrillary tangles and : (iii)  the selective loss of neurons. Although the first two are described, the third is not. This needs to be corrected.
7. Lines 51 and 52. the neuronal deposition of neuritic plaques of β-amyloid aggregates occurs outside, not within, neurons. This needs to be corrected.
8. Line 58 is incorrect in its use of the term ‘pre-dementia’. This needs to be corrected.
9. Lines 93-97: a description of what proteins target would be helpful. What about PET agents that target tau?
10. Is it correct to refer to probiotics as nutraceuticals?
11. Evidence should be presented to indicate that changes in the gut of a fly is relevant to changes in the gut of humans?

Author Response

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Reviewer 4 Report

 

The manuscript entitled “Nutraceutical and probiotic approaches to examine molecular interactions of the amyloid precursor protein APP in Alzheimer’s disease models” by Jalali et al. in the first part describes Alzheimer’s disease symptoms, pathogenesis, and genetic components regarding APP; in the second part reports the results of adopting nutraceutical approaches mainly performed in Drosophila models.

A merit of this manuscript is that the language is comprehensible, and the argumentations are easy to follow.

However, there are some issues that should addressed by the authors.

The description of the therapeutic approaches for AD tested in clinical trials is not exhaustive. This can be acceptable since the focus of the review was not centred on this topic. However, the fact that only a fraction of them is described should be more clearly mentioned.

The description of nutraceutical studies is not systematic, since it is mainly focused on Drosophila models, at least as a starting point, whereas a larger number of studies used rodent models. Again, this approach can be considered suitable, provided that the fact is made clear. In particular, the title should be changed to convey the focus on Drosophila.

Lines 405-410: in this part, used therapeutic approaches are placed on the same line as very preliminary studies on model organisms. This is confusing and should be reformulated.

A more critical discussion is requested about nutraceutical approaches since only very preliminary data are available, thus no conclusive evidence is available.

Author Response

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Reviewer 5 Report

The article reviews recent promising approaches to assessing the therapeutic potential of nutraceutical and probiotic agents in fruit fly and mouse models of Alzheimer's disease. Although the topic is being intensively investigated, and the authors present promising studies, the review lacks the necessary scientific depth to be published. The main shortcomings are: The article devotes much space to reviewing well-known concepts such as the symptoms, progression, diagnosis, and pathogenesis of Alzheimer's disease. A section is briefly dedicated to the role models Drosophila has played in the investigations of the processing of the amyloid precursor protein. Finally, we find a short section devoted to the central issue of the proposed revision.

Although the review's objective is exciting, the approach and presentation need to be significantly modified.

Author Response

We thank the review for their kind comments and specific considerations of our manuscript.We thank the reviewer for raising this fair point. We have expanded the sections that are themain focus of the review manuscript, including additional nutraceuticalcompounds(lines 420;445-452), additional Drosophila studies providing insight into autophagy(304-309), learning and memory(338-342), axonal growth(339), immune response(430-433), and gut-brain interactions(504-509). As such, the sections covering Drosophila studies as well as the nutraceutical and synbiotic approachesrepresent the majority of the manuscript. Although some of the language has been shortened and made more concise for the first sections, they provide proper background that clarifies the advantages of the use of animal models and therapeutic approaches described in the last sections, as appreciated by another reviewers.

Reviewer 6 Report

The manuscript entitled “Nutraceutical and probiotic approaches to examine molecular interactions of the amyloid precursor protein APP in Alzheimer’s disease models” is an interesting review. It is easy for readers to understand the characteristics of the Drosophila AD model and it may be linked with future treatment of AD using Drosophila.

However, I have several comments.

In the abstract, Abbreviations should be written in full terms first such as APPL and it would be better to standardize the notation e.g. “Alzheimer’s disease (AD)”, and “amyloid precursor protein APP”.

As well, in the manuscript, they were shown, such as Amyloid-β and Aβ. Therefore, the author should recheck the manuscript.

Line 203, “As shown in Figure 2 above” is not easy for readers to understand. The author should explain in more detail or make a new figure.

Author Response

Reviewer 6:The manuscript entitled “Nutraceutical and probiotic approaches to examine molecular interactions of the amyloid precursor protein APP in Alzheimer’s disease models” is an interesting review. It is easy for readers to understand the characteristics of the Drosophila AD model and it may be linked with future treatment of AD using Drosophila.We thank the reviewer for their kind comments and appreciation of our manuscript.However, I have several comments.In the abstract, Abbreviations should be written in full terms first such as APPL and it would be better to standardize the notation e.g. “Alzheimer’s disease (AD)”, and “amyloid precursor protein APP”.We thank the reviewer for raising a fair point. All abbreviations in the abstract have been clarified, as suggested.As well, in the manuscript, they were shown, such as Amyloid-β and Aβ. Therefore, the author should recheck the manuscript.We thank the reviewer for raising a fair point. We have made our writing style more consistent by exclusively using the terms Amyloid-β or Aβ, as suggested.Line 203, “As shown in Figure 2 above” is not easy for readers to understand. The author should explain in more detail or make a new figure.We thank the reviewer for raising such a fair point. We have deleted that sentence to prevent confusion and clarified the language used in that section(line 237). A new table describing the main nutraceutical compounds included in our manuscript has been added, which is addressed in a different section of the manuscript(line 420; Table 1).

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed all my concerns. The manuscript is now publishable. 

Author Response

We thank the reviewer for their kind comments and interest in our manuscript.

Reviewer 3 Report

The manuscript still has a number of shortcomings:

 

1. Lines 58-59: the argument does not sound as the invasiveness of any post-mortem procedure is not relevant as the individuals are no longer alive.
2. In response to my comments, the authors indicated that they had included a new table. However, I could not find it.
3. Line 66: a definitive diagnosis can only be made by demonstrating the existence of plaques and tangles, either a post-mortem or a biopsy or by PET imaging. Without this the diagnosis can only be described in terms of probability. This needs to be corrected.
4. Line 99; PET imaging does not usually detect brain shrinkage, so this needs to be corrected.
5. Line 105; If reduced FDG signal reflets ‘neuronal hypometabolism due to neurodegeneration’, then it is a measure of tissue loss not hypometabolism There is, in fact, evidence from biopsy tissue from AD patients to indicate increased glucose metabolism in AD – Sims NR et al (1980) Lancet 16;1(8164):333-6.
6. I am not convinced that the authors have shown that the doses of nutraceuticals given to the flies is relevant to the biological effects claimed in both Fig. 1 and the main body of text. This needs to be addressed.
7. Lines 136-7: we cannot know this as we don’t know when e neuronal and synaptic loss begins. Note that >85% of nigrostriatal neurons need to be lost before the symptoms of Parkinson’s disease emerge.

 

Author Response

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Reviewer 4 Report

The authors have addressed all concerns.

Author Response

We thank the reviewer for their kind comments and help in improving our manuscript.

Reviewer 5 Report

The manuscript has been substantially improved and it is now suistable for publication.

Author Response

We thank the reviewer for their kind comments and help in improving our manuscript.

Round 3

Reviewer 3 Report

The responses are still not satisfactory for the following reasons:

 

1. Lines 58-59: the term ‘less invasive’ is not appropriate since the person with AD is no longer alive at a post mortem – by definition. It would be helpful to specifically refer to PET tau and Ab imaging here and indicate that the presence of sufficient quantities of both permit a diagnosis of AD.
2. Lines 66-67: The statement is not true. A diagnosis of possible or probable AD is possible once evidence of memory impairment is identified.
3. Lines 91-95: The authors seem confused. By definition, in the preclinical state, of AD (not ‘AP’), there are no clinical symptoms, so (unless it is familial AD) there is no rationale for giving them a PET scan with tau or Ab The authors have overlooked the largest post-mortem study looking at the development of plaques and tangles prior to the emergence of symptoms – Ohm et al (1995), Neuroscience 64: 209-217.
4. Lines 112-118: There is no hypometabolism if tissue atrophy is taken into account, so the text is misleading and needs to be corrected. There is, in fact, evidence of hypermetabolism (Sims et al).
5. Lines 147-153: I am not convinced that there is evidence to suggest that ‘Aβ deposition and tau pathology can precede neuronal and synaptic loss by decades’ as measures of neuronal/synaptic loss were not measured in the studies cited. It would be surprising if there was no neuronal/synaptic loss accompanying Aβ deposition and tau pathology. This needs to be considered and the text modified. Note that changes in transgenic models is not the same as changes in humans with AD.
6. Lines 391-394: This is a fundamental question, which has still not been answered. Cannot answer this question, I do believe that this paper deserves to be published.
7. Table 1: Following on from point 6, the table is uninformative, and essentially useless, without some reference to the concentration/dose of the nutraceuticals used to ameliorate ‘AD phenotypes’. It would also be helpful to define what AD phenotypes’ were measured. These points need to be fully addressed.

Author Response

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