Overview of Neuroglia Activation, Chronic Neuroinflammation, Remodeling, and Impaired Cognition Due to Perivascular Adipose Tissue-Derived Extracellular Vesicle Exosomes in Obesity and Diabetes

Round 1

Reviewer 1 Report (Previous Reviewer 3)

The authors responded all the concerns. I have no more questions.

Author Response

The author wishes to thank reviewer number 1 for taking the precious time, effort, to review this submitted manuscript.

Your comments and suggestions were important and very helpful during this review process.

Sincerely, with gratitude

Melvin R. Hayden

Submitting author 

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

This well-organized review introduces the role of PVAT-dEVexos released from perivascular AT in neuroglial activation and its potential contribution to cognitive impairment. Some questions should be further illustrated to make the audience better understand the pathological relevance of this peripheral-CNS cross-organ interaction.

First, in the title, the author introduces two related health conditions involved in the PVAT-dEVexos. However, diabetes is not even mentioned in the abstract. Even in the main part of the manuscript, we fail to see a detailed introduction of how diabetes contributes to the formation of PVAT-dEVexos at the molecular or cellular level. Also, diabetes alone has a great impact on the cognitive function of the patients. Is that cognitive impairment associated with PVAT-dEVexos or in an independent manner?

Second, the author mentioned that there are approximately 60% of the population in the U.S. has been classified as being overweight. However, we wonder whether the author could list epidemiological data suggesting the association between weight and PVAT level. This is because the overweight population is huge while the number of people with chronic neuroinflammation is relatively low. Therefore, we wonder if the PVAT accumulation would take a long time before rupture or if there must be other comorbid diseases such as diabetes or aging-associated neurodegeneration along with BBB breakdown.

Third, aging is the principal reason for cognitive decline. We wonder if there is evidence suggesting that BAT-WAT transformation increased along with the aging process.

Fourth, how the PVAT-dEVexos target the brain for infiltration. Is there any target receptor detected on the surface of these small exosomes?

Fifth, except for the miRNA, is there any other more potent factor in these brain-infiltrated exosomes to induce the microglial M1 type? We have worked with macrophages and microglia for years, but we don't think one or two miRNAs alone could activate the microglial to adopt the M1 phenotype. However, miRNAs could promote the activation in the pre-existing proinflammatory condition, such as a secondary response to neurodegeneration. 

Sixth, is there any human-level evidence to support PVAT-dEVexos (CSF?) in the brain? Or is there any epidemiological study focusing on the association between the level of  PVAT-dEVexos and cognitive function in a particular group of patients (young vs. aged)?

 

 

Author Response

Author wishes to thank reviewer number 2 for the precious time, effort and knowledge provided in order to review this submitted manuscript.  Your questions, comments, and suggestions were extremely helpful throughout this reviewing process. 

Sincerely, with gratitude

Melvin R Hayden

Submitting author  

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (New Reviewer)

I am thankful for the insightful answer from the authors. It is a pity that the author has a length limit, so he can't put all his thoughtful thinking into the review paper. This exciting topic bridges the most prevalent overweight issue with aging-induced cognitive decline. Enhanced chronic inflammation is a common underlying mechanism among Diabetes, Overweight, and Aging. The author introduced exosome cross-organ transportation as a promising molecular pathway to link all of them together. That is why we are eager to know more about how diabetes influences the maturation and release of the exosome and whether aging promotes the transition into inflammatory WAT. In a healthy young brain, there is a solid system to limit and resolve the inflammation, which would become weaker after aging, from the leaky BBB to the phenotype change of microglia and astrocyte due to pathological changes such as accumulation of aggregated protein or neuronal death-induced DAMP signal release. In such a proinflammatory storm, the PVAT is more likely a potentiation factor but not an inducer. As for the human studies, it would be solid evidence if we had the data that overweight aged cognitive decline patients have more PVAT in the CSF than aged-control groups, and T2DM would even be a potentiation factor to that increase. On the other hand, if there is evidence that exists to prove isolated and concentrated PVAT found new CNS target receptor ligands in a mass spectrometry analysis would be fantastic. Like a drug delivery system, the liposome without a target ligand will primarily be shown in the liver and kidney but not the brain.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This review describes how Perivascular Adipose Tissue-Derived Extracellular 2 Vesicle Exosomes in Obesity and T2DM communicate with CNS cells. There is a lot of information in the review and the subject is broadly covered. It is very clear that the author is a long-term expert in his field and has a lot of knowledge on this subject, as well as a clear view on possible mechanisms. However, the review is chaotic, way too long, there a too many figures, and the quality and clarity of the figures is low.

Major points:

- The review is way too long with too many figures (18 in total). Also the titles of the different parts are long and not really clear (for instance: 2. Perivascular Adipose Tissue (PVAT) Adipokines, Peripheral Cytokines/Chemo- 189 kines (pCC), PVAT-derived Extracellular Vesicle Exosomes (PVAT-dEVexos) From 190 Adipocytes and (PVATΦ-dEVexos) From Macrophages)

- the amount, but also the content of some figures make it look like a research paper like, while it is a review. 

- some of the figures are experimental while there is no set-up or method described, or no reference to the original paper

- figure 1, 10, 11, 13, 17, 18 is direct reference to the author himself. I do understand that this author is an expert in this field but this is a lot of use of his own papers and it is questionable whether its necessary to repeat all these figures for a review or rather keep it at an overview figure that summarizes the earlier findings. What is CC 4.0?

- Figure 1 is not really necessary for the review in my opinion. A short description before diving into the WAT vesicles is accurate but this specific figure does not add to the content of the review.

- figures are in general very chaotic and contain a lot of text (for instance figure 15). Additionally they seem to be not made by a professional program for scientific figures. They are not of enough quality to be considered for publication (the circles in fig 2, outlines in fig 3, figure 12, etc).  A figure should be clear, structured and easy to understand, otherwise it doesn't help the review. Perhaps, a peer can be included in the process that focusses on the professionality and the clearness of the figures.

Reviewer 2 Report

This article is an interesting subject about the effect of extracellular vesicles small exosome(s) and its relationship with the neuroglia in Obesity and T2DM, which is nowadays a hot topic. However, besides the interesting topic, it was not easy to read. Heavy and long, it was not fluid and did not hold my attention.

So, it needs several adjustments to be suitable for publication.

Another main issue is the figures. All figures are poorly formatted, with low quality. Dark and polluted. It did not help at all with the reading.

For example, figure 10 has visible distortion, in addition to simple errors, such as font size and even different line thickness.

Moreover, finally, in figure 12, I do not know where to look first. A figure must be self-explanatory; it loses its value if it needs the legend.

Several repeated expressions, such as on line 687.

Furthermore, astrocytes and microglia were not emphasized as the title says `Neuroglia Activation` needs to be more detailed for the article's main topic.

Reviewer 3 Report

The manuscript by Hayden et al. is an exciting overview for recent summary investigations in Exosomes. There is a very nice rationale for writing the review of EVs functions released by adipose tissues on multiple organs especially the CNS system based on human patient family data and multiple mouse models.

 Of course, it’s a very broad topic and for now not sufficient to describe a causal effect but a very compelling reason to carry out the study and test the EVs hypothesis regarding an interaction. Further, an interaction between metabolic dysfunction and neuroinflammation has been described. The authors summarized recent studies based on human and multiple models describe interesting intersections between adipose tissue, immune system, and brain.

 The authors clearly show that adipose origin EVs has complex functions in the regulation of microglia and astrocyte reactions and may contribute to a feed forward loop which finally leading to a vicious cycle.

 I believe this review article will bring broad interest to several research field researchers.

 Mostly, the aim of the review articles is to introduce a non-expert, or new researcher to the topic, in this case, the review articles are multidisciplinary in several different diseases. As a result, this review articles are written for a wider audience. If the author can simplify the introduction part, will be easier for the general readers.

 It will be better to put the terms in a table and part of background information into a box as a single unit that can make the whole paragraph more readable. For example, from row 47-80, the introduction of AT( adipose tissue), it is better to put it in a box or describe it as a simple chart. From row 192-198, the introduction of inflammatory factors better put into a well-organized table.

 This review delivers an overarching message which is adipose released EV can affect glia reaction, throughout the various sections of the article. It should clearly explain the key concepts, questions, and debates in the literature, but also provide a new perspective. Based on this main purpose, the first part is containing too much information and the message should be made clearer by reorganizing the information. If the author can subdivide the first section to several sub-sections, the structure will be better. The author described to us a whole picture of the amazing journey of adipose origin EVs. It is too much information for one review. I think the author should focus on part 3 and 4 and make part 1 and 2 more concise.

 

The content of EVs is the major effectors of the trafficking EVs. If the author can summarize the data to compare the EVs in more details or give future directions to understand more of the EVs will be better. For example, compare the EV between healthy and disease; compare the EV from different adipose tissues (Brown and white), immune cells etc.

Minor points: row 113, Figure 3 should be Figure 2