The Prickly Solution to Metabolic Syndrome: A Multitarget View on the Opuntia ficus-indica Fruit Phytocomplex

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors, the submitted manuscript is well-structured, coherent, and  comprehensive. However, it needs a moderate revision mainly to strengthen critical appraisal and clinical relevance. 

Here are the main weaknesses that need to be addressed:

Lacks systematic methodology (no PRISMA, search strategy, or selection criteria described) and therefore risks selection bias in included studies.

Human data are scarce, based on small cohorts, short duration, and heterogeneous interventions.

Heavy dependence on in vitro and animal models.

Translational relevance to humans is repeatedly acknowledged but not critically dissected.

Studies are summarized descriptively rather than evaluated (e.g., risk of bias, study limitations).

Potential overinterpretation of mechanistic pathway.

Variability in OFIF composition (cultivar, preparation), as well as doses and formulations are mentioned but not deeply analyzed in terms of impact on conclusions.

Topic (functional foods / plant bioactives in MetS) is well covered in literature and needs a clearer unique angle or conceptual advance beyond compilation.

Strong focus on positive metabolic effects but limited discussion of potential adverse effects and interactions. 

Multiple mechanistic schematics (Figures 1–5) are visually strong but partially overlapping.

Author Response

Response to Reviewer 1 
We sincerely thank the Reviewer for the careful evaluation of our manuscript and for the constructive 
and insightful comments. We are pleased that the Reviewer found the manuscript well-structured, 
coherent, and comprehensive. We have carefully addressed all comments and revised the manuscript 
accordingly to strengthen critical appraisal, improve translational clarity, and enhance overall 
scientific rigor. All modifications have been incorporated into the revised version and are detailed 
below. 
Comment 1 
Lacks systematic methodology (no PRISMA, search strategy, or selection criteria described) and 
therefore risks selection bias in included studies. 
Response: 
We thank the Reviewer for this important observation. The present work was intentionally designed 
as a narrative, mechanistic review rather than a systematic review. However, to enhance transparency 
and reduce potential selection bias, we have now explicitly clarified the literature approach in a newly 
added subsection (Literature Approach and Scope). This section describes the databases consulted, 
search terms, and rationale for study selection. We also explicitly state that the aim of the review is 
to provide a systems-level conceptual framework rather than a quantitative synthesis. 
Comment 2 
Human data are scarce, based on small cohorts, short duration, and heterogeneous interventions. 
Response: 
We fully agree with the Reviewer. We have strengthened the manuscript by explicitly acknowledging 
these limitations in multiple sections and in the Conclusion. In particular, we now emphasize that 
current human evidence is preliminary, heterogeneous, and insufficient to support definitive clinical 
conclusions, highlighting the need for well-designed randomized controlled trials. In this context, the 
present review is intended not only to synthesize existing evidence, but also to stimulate and guide 
future research efforts toward more robust, standardized, and clinically meaningful investigations in 
metabolic syndrome. 
Comment 3 
Heavy dependence on in vitro and animal models. 
Response: 
We appreciate this comment and have revised the manuscript to more clearly distinguish between 
preclinical mechanistic evidence and human data. Throughout the text, we now explicitly indicate 
when findings derive from in vitro or animal models and caution against direct extrapolation to human 
physiology. 
Comment 4 
Translational relevance to humans is repeatedly acknowledged but not critically dissected. 
Response: 
We agree and have significantly strengthened the discussion of translational relevance. We have 
added explicit considerations regarding bioavailability, dose equivalence, whole-food matrix effects, 
and interindividual variability (including microbiota-related responses). These additions provide a 
more critical interpretation of the challenges in translating preclinical findings into clinical contexts. 
Comment 5 
Studies are summarized descriptively rather than evaluated (e.g., risk of bias, study limitations). 
Response: 
We thank the Reviewer for this suggestion. We have enhanced the critical appraisal across the 
manuscript by explicitly discussing study limitations and heterogeneity. In addition, Table 1 has been 
revised to better reflect the level of evidence and to include a structured summary of key limitations 
(e.g., small sample size, short duration, lack of standardized dosing, and reliance on surrogate 
biomarkers). 
Comment 6 
Potential overinterpretation of mechanistic pathway. 
Response: 
We agree and have carefully revised the manuscript to avoid overinterpretation. We have replaced 
assertive wording (e.g., “demonstrates”) with more cautious expressions (e.g., “suggests”, “has been 
associated with”) and explicitly clarified when mechanisms are derived from preclinical evidence. 
Comment 7 
Variability in OFIF composition … not deeply analyzed. 
Response: 
We appreciate this important point. We have expanded the discussion on compositional variability, 
emphasizing the impact of cultivar, geographic origin, ripening stage, and processing methods on 
bioactive composition and bioavailability. We also highlight how this variability represents a key 
limitation for reproducibility and translational interpretation. 
Comment 8 
Topic is well covered in literature and needs a clearer unique angle. 
Response: 
We thank the Reviewer for this observation. We have clarified the novel conceptual contribution of 
the manuscript by explicitly framing it as a systems-level integration of OFIF bioactives within 
interconnected redox-inflammatory-metabolic networks. This perspective is now more clearly stated 
in both the Introduction and the Conclusion. 
Comment 9 
Limited discussion of potential adverse effects and interactions. 
Response: 
We agree and have added a new subsection “Safety Considerations and Potential Limitations” 
addressing potential adverse effects, tolerability, and possible interactions, particularly in the context 
of high intake or metabolic conditions. 
Comment 10 
Multiple mechanistic schematics (Figures 1–5) are visually strong but partially overlapping. 
Response: 
We thank the Reviewer for this insightful comment. We have revised figures legends to reduce 
redundancy and improve conceptual clarity. In particular, we have clarified the distinct role of each 
figure and explicitly highlighted their complementary nature within the manuscript. 
• Figures 3 - 5 were clarified to represent distinct bioactive classes (flavonoids/betalains vs 
carotenoids, minerals and vitamins), while acknowledging partial overlap in downstream 
signaling.  
• Legends have been revised to explicitly state that shared pathways are simplified to emphasize 
compound-specific mechanisms.  
• A bridging sentence has been added in the text to highlight the complementary, rather than 
redundant, role of these bioactive classes.  
We believe that these revisions have significantly strengthened the manuscript by improving critical 
interpretation, enhancing translational relevance, and clarifying the conceptual framework. We 
sincerely thank the Reviewer for the valuable suggestions, which have greatly improved the quality 
of our work. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is sound in terms of both content and style – the argument is logically structured, and the individual sections guide the reader coherently through the topics discussed.

The selection of references can be considered appropriate and up-to-date, encompassing both review articles and experimental studies, which strengthens the credibility of the conclusions presented. The authors skilfully synthesise the available data, highlighting the most important modes of action of the bioactive compounds analysed.

The figures deserve special mention, as they constitute a highly valuable element of the publication – they present the mechanisms of action of individual phytochemical components in a clear, organised and schematic manner. Thanks to them, complex biochemical processes and the relationships between metabolic pathways are presented intuitively, which significantly facilitates the reading of the text and may be helpful both for readers less familiar with the subject and for specialists seeking a concise summary of the mechanisms discussed.

The article offers an interesting perspective on the potential of Opuntia ficus-indica in relation to metabolic syndrome; however, its limitation lies in its clear focus on individual bioactive compounds and their mechanisms of action. Such a reductionist approach overlooks the fact that the fruit of this plant contains a complex phytocomplex (including polyphenols, betalains, vitamins and fibre), the components of which may interact synergistically or antagonistically in vivo.

Consequently, analysing isolated molecules does not fully reflect the actual biological effect of the whole plant material, where mutual interactions may modify bioavailability, biological activity and the final effect. Omitting this aspect limits the possibility of extrapolating the results to practical dietary or clinical applications.

It is also important to address any limitations regarding the use of Opuntia ficus-indica in animal and human studies (with particular attention paid to potential interactions). This aspect should also be highlighted in the manuscript (perhaps in the conclusion).

Author Response

We sincerely thank the Reviewer for the thorough and highly positive evaluation of our manuscript. We greatly appreciate the recognition of the logical structure, clarity of presentation, and the value of the figures in facilitating the understanding of complex biochemical mechanisms. We are particularly grateful for the insightful comments, which helped us further strengthen the conceptual and translational aspects of the manuscript.

Comment – Reductionist approach vs phytocomplex

The article offers an interesting perspective… limitation lies in focus on individual bioactive compounds… overlooks phytocomplex interactions.

Response:
We thank the Reviewer for this insightful and highly relevant observation. We fully agree that focusing on individual bioactive compounds may not fully capture the biological complexity of the OFIF phytocomplex, where multiple constituents (including polyphenols, betalains, vitamins, fiber, and lipophilic compounds) may interact synergistically or antagonistically in vivo.

In response, we have strengthened the manuscript to better emphasize the concept of whole-food matrix and phytocomplex interactions. In particular:

• We have expanded the discussion in Section 3 to explicitly state that the biological effects of OFIF cannot be fully attributed to individual compounds, highlighting the role of compositional complementarity between pulp and seeds.
• We have incorporated statements across the manuscript emphasizing that evidence derived from isolated compounds may not fully reflect in vivo biological responses, due to interactions affecting bioavailability, metabolism, and overall activity.
• We have reinforced in the Conclusion that future research should move beyond reductionist approaches and prioritize the investigation of whole-food matrices, where interactions among bioactive components may determine the net biological effect.

These additions aim to provide a more balanced and translationally relevant interpretation of OFIF within a real-world dietary context.

 Comment – Limitations and interactions in animal and human studies

It is important to address limitations… including potential interactions.

Response:
We fully agree with the Reviewer and have further strengthened the discussion of limitations. Specifically:

- We have expanded the discussion of translational limitations, including heterogeneity in OFIF composition, variability in dosing, and differences in bioavailability across studies.

- We have added a dedicated subsection on safety considerations and potential interactions, addressing possible gastrointestinal effects and the potential for interactions with glucose-lowering therapies.

- We have emphasized that current evidence from animal and human studies remains limited, heterogeneous, and not fully generalizable, particularly in the context of metabolic syndrome.

These aspects are now clearly highlighted in both the main text and the Conclusion.

Final Statement

We believe that these revisions have significantly strengthened the manuscript by integrating mechanistic insights with the complexity of the OFIF phytocomplex and by improving its translational relevance. We sincerely thank the Reviewer for these valuable suggestions, which have contributed to enhancing the overall quality of our work.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you. All my comments have been adequately addressed. 

Author Response

Response to Reviewer 2

Reviewer 2

We sincerely thank the Reviewer for the thorough and highly positive evaluation of our manuscript. We greatly appreciate the recognition of the logical structure, clarity of presentation, and the value of the figures in facilitating the understanding of complex biochemical mechanisms. We are particularly grateful for the insightful comments, which helped us further strengthen the conceptual and translational aspects of the manuscript.

Comment – Reductionist approach vs phytocomplex

The article offers an interesting perspective… limitation lies in focus on individual bioactive compounds… overlooks phytocomplex interactions.

Response:
We thank the Reviewer for this insightful and highly relevant observation. We fully agree that focusing on individual bioactive compounds may not fully capture the biological complexity of the OFIF phytocomplex, where multiple constituents (including polyphenols, betalains, vitamins, fiber, and lipophilic compounds) may interact synergistically or antagonistically in vivo.

In response, we have strengthened the manuscript to better emphasize the concept of whole-food matrix and phytocomplex interactions. In particular:

• We have expanded the discussion in Section 3 to explicitly state that the biological effects of OFIF cannot be fully attributed to individual compounds, highlighting the role of compositional complementarity between pulp and seeds.
• We have incorporated statements across the manuscript emphasizing that evidence derived from isolated compounds may not fully reflect in vivo biological responses, due to interactions affecting bioavailability, metabolism, and overall activity.
• We have reinforced in the Conclusion that future research should move beyond reductionist approaches and prioritize the investigation of whole-food matrices, where interactions among bioactive components may determine the net biological effect.

These additions aim to provide a more balanced and translationally relevant interpretation of OFIF within a real-world dietary context.

 Comment – Limitations and interactions in animal and human studies

It is important to address limitations… including potential interactions.

Response:
We fully agree with the Reviewer and have further strengthened the discussion of limitations. Specifically:

- We have expanded the discussion of translational limitations, including heterogeneity in OFIF composition, variability in dosing, and differences in bioavailability across studies.

- We have added a dedicated subsection on safety considerations and potential interactions, addressing possible gastrointestinal effects and the potential for interactions with glucose-lowering therapies.

- We have emphasized that current evidence from animal and human studies remains limited, heterogeneous, and not fully generalizable, particularly in the context of metabolic syndrome.

These aspects are now clearly highlighted in both the main text and the Conclusion.

Final Statement

We believe that these revisions have significantly strengthened the manuscript by integrating mechanistic insights with the complexity of the OFIF phytocomplex and by improving its translational relevance. We sincerely thank the Reviewer for these valuable suggestions, which have contributed to enhancing the overall quality of our work.