The Endocrine–Metabolic Axis Regulation in Offspring Exposed to Maternal Obesity—Cause or Consequence in Metabolic Disease Programming?

Round 1

Reviewer 1 Report

The authors have satisfactorily revised their manuscript.

Author Response

We acknowledge the reviewer for the previous comments to improve the manuscript and the last review of the paper.

Reviewer 2 Report

Following the suggestions, this submission has been improved. Overall, the current version is clear and easy to read. The final version in clear form, however, was not submitted. As a result, figure legends in each useful figure were difficult to characterize. Please proofread it thoroughly before publication. Thank you kindly.

Author Response

We appreciate the reviewer comments and the proofreading and graphical editing were done in the present version.

Reviewer 3 Report

The authors have made substantial changes but some points still require further clarifications. There are multiple repetitive points within the same paragraph and sentence which can be summarised in a clearer format. The manuscript requires a language check.

Abstract:

Lines 23-26: The authors stated that “The different availability of metabolic substrates, namely glucose, can modulate cellular growth, proliferation, and differentiation resulting in different levels of tissues’ maturation and function. How is gut dysbiosis (line 26) part of this?  

 

Line 28: Please change “deregulation” to “dysregulation”

Line 31: What does “their” refers to?

Line 32: Please remove “dysregulated and/or”

Lines 35-37: Please change to “However, these hormones on other organs may potentiate metabolic dysfunction or even trigger disease in organs (liver, pancreas, heart), that are programmed in utero for early disease”.

Lines 39-40: How can a “new balance” be achieved with the dysregulation?

Lines 28-43: The points can be summarised in a clearer format

 

1. Introduction

Lines 73-75: “In the long-term, MO is related to increased odds ratios for future development of obesity, metabolic syndrome, type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD)”-Please remove either “long-term” or “future” as they refers to the same concept, and please specify if this increased odds ratio of development are for mothers or offspring.

Lines 90-94: Long sentence that does not read well. Please kindly rephrase this part “even though MO-offspring can present low gestational weight if MO is concomitant with hypertension and compromised placental vasculature”.

2. Mechanistic links between MO and the development of metabolic disease in the offspring

Line 120: Grammatical error. What do the authors mean by “clinical studies of MO offspring increased disease”?

Lines 133-134: Grammatical error. Please change to “There are multiple mechanisms associated with these outcomes and increased predisposition to metabolic disease for MO progeny are multifactorial”.

Lines 145-156: How does higher glucose in maternal blood associate/cause with insulin resistance in MO offspring?

3. The second hit of developmental programming by MO: the endocrine-metabolic axis

Lines 210-227: This section seems to contradict with the abstract lines 25-27 that stated adipocyte early differentiation and gut dysbiosis as first hit. Please kindly clarify and revise.

Figure 2: Adipose tissue dysfunction and gut dysbiosis seem to be the consequence of the second hit in the diagram but the text explanation (lines 220-226) seems to suggest that they are the second hit. How do diabetes, NAFPD and MAFLD lead to early metabolic and cardiovascular diseases? Diabetes, NAFPD, MAFLD are metabolic diseases themselves. Why do the authors repeated by including a glucometer for early metabolic and cardiovascular diseases which represent diabetes when diabetes is in the earlier section? The pictures in the last row for early metabolic and cardiovascular diseases are not informative-a glucometer of normal glucose 4.5mmol/L does not represent diabetes or insulin resistance.

Line 220: Please change “is” to “are”

Line 249: What do the authors meant by “Following MO-offspring’s life”?

Lines 372: The dysregulation of the endocrine-metabolic axis should be explained e.g. what ae the factors/mechanisms contributing to it. From the authors’ write-up, it should be adipose tissue dysfunction and gut dysbiosis. Hence, Section 3.3 should come before section 3.2.

Author Response

Thank you for the suggestions to improve the manuscript. We clarified the ideas as recommended by the reviewer and made the suggested corrections. We would like to point out that the previous version was already checked by an English native speaker as proofed to the journal editor, thus we would appreciate it if you could point out the critical language and grammatical errors.

Abstract:

Lines 23-26: The authors stated that “The different availability of metabolic substrates, namely glucose, can modulate cellular growth, proliferation, and differentiation resulting in different levels of tissues’ maturation and function. How is gut dysbiosis (line 26) part of this?  

Fetal gut development is also affected by maternal obesity. The fetal gut presents impaired gut barrier permeability and early activation of inflammation- and unfolded protein response-associated mechanisms (DOI: 10.1113/JP277353; 10.2527/jas.2013-7106). This was observed in the offspring's fetal stage, thus not dependent on gut dysbiosis. We would like to point out that the early development of the gut microbiome is intrinsically connected with gut function and inflammation. The early dysfunction in intestinal permeability is likely to exacerbate the consequences of gut dysbiosis.

 

Line 28: Please change “deregulation” to “dysregulation”

The authors thank the reviewer for this correction.

 

Line 31: What does “their” refers to?

“their” was referring to the previously mentioned adipose tissue and gut, we clarified by replacing by “these organs’.

 

Line 32: Please remove “dysregulated and/or”

As suggested by the reviewer, we removed the words from the sentence.

 

Lines 35-37: Please change to “However, these hormones on other organs may potentiate metabolic dysfunction or even trigger disease in organs (liver, pancreas, heart), that are programmed in utero for early disease”.

We thank and accepted the suggestion from the reviewer.

 

Lines 39-40: How can a “new balance” be achieved with the dysregulation?

In the origin of any disease, there is a dysregulation/dysfunction in any protein (e.g. mutation), cell (e.g. mitochondrial dysfunction), or tissue (e.g. lipid accumulation in NAFLD). In any of these cases, the organism finds a new homeostatic state even if this results in accelerated damage accumulation (e.g. oxidative damage). New balances can occur even in a disease state. In this case, the dysregulated release of endocrine factors induces responses in the tissues that adapt to find a new balance (e.g. increased leptin production in adipose tissue stimulates hepatic glucose production which will be balanced by increased glucose uptake and use/storage in other tissues or even the liver, insulin production or resistance, etc).

 

Lines 28-43: The points can be summarised in a clearer format

We performed the clarifications above mentioned by the reviewer in these two paragraphs. Some clarifications and definitions included in the abstract were previously suggested by other reviewers that already agreed with the manuscript publication. We think that considerable alterations would conflict with the alterations suggested by the other reviewers. We performed alterations that don’t result in significant modifications of the ideas in the text.

 

1. Introduction

Lines 73-75: “In the long-term, MO is related to increased odds ratios for future development of obesity, metabolic syndrome, type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD)”-Please remove either “long-term” or “future” as they refers to the same concept, and please specify if this increased odds ratio of development are for mothers or offspring.

We thank the reviewer for the suggestion. We removed the term “future” and clarified that the sentence is referring to the mothers.

 

Lines 90-94: Long sentence that does not read well. Please kindly rephrase this part “even though MO-offspring can present low gestational weight if MO is concomitant with hypertension and compromised placental vasculature”.

We clarified and divided the sentence to increase readability.

 

2. Mechanistic links between MO and the development of metabolic disease in the offspring

Line 120: Grammatical error. What do the authors mean by “clinical studies of MO offspring increased disease”?

We thank the reviewer for asking for clarification in the sentence. We changed it to “The evidence in clinical studies of MO offspring-associated increased disease incidence”.

 

Lines 133-134: Grammatical error. Please change to “There are multiple mechanisms associated with these outcomes and increased predisposition to metabolic disease for MO progeny are multifactorial”.

We changed the sentence to clarify the idea: “The mechanisms associated with these outcomes and, subsequently, increased predisposition to metabolic disease for MO progeny are multifactorial”

 

Lines 145-156: How does higher glucose in maternal blood associate/cause with insulin resistance in MO offspring?

Placenta only can partially buffer maternal circulating glucose concentrations, meaning that higher maternal glucose blood concentrations induce higher glucose concentrations in fetal circulation (lines 133-137). Maternal hyperglycemia due to diabetes and/or obesity stimulates fetal insulin secretion, favoring anabolic reactions (eg lipogenesis and protein synthesis) and increasing fetal glucose consumption in insulin-sensitive cells (hepatocytes, myocytes, adipocytes), leading to increased growth, rising glucose requirements in late gestation and eventually inducing insulin resistance. We briefly added this information to the referred paragraph.

 

3. The second hit of developmental programming by MO: the endocrine-metabolic axis

Lines 210-227: This section seems to contradict with the abstract lines 25-27 that stated adipocyte early differentiation and gut dysbiosis as first hit. Please kindly clarify and revise.

We would like to clarify that adipose tissue dysfunction and gut dysbiosis are consequences of the first hit of programming. The different release of endocrine factors from these tissues as a consequence of adipose tissue dysfunction and gut dysbiosis represent the second hit. We clarified this in the text:

“Dysfunction in adipose tissue and gut is observed in the early life stages of MO-offspring as a consequence of the first hit of disease programming in MO offspring(see sections 3.1 and 3.3). Along with these alterations, they release factors (e.g., adipokines, GLP-1, GLP-2) in different concentrations due to MO. We propose that this dysfunction (disrupted release of endocrine factors) represents a second hit (i.e., challenge) to the other organs involved in body metabolic homeostasis (e.g., liver, pancreas).” (lines 205-210).”

 

Figure 2: Adipose tissue dysfunction and gut dysbiosis seem to be the consequence of the second hit in the diagram but the text explanation (lines 220-226) seems to suggest that they are the second hit. How do diabetes, NAFPD and MAFLD lead to early metabolic and cardiovascular diseases? Diabetes, NAFPD, MAFLD are metabolic diseases themselves. Why do the authors repeated by including a glucometer for early metabolic and cardiovascular diseases which represent diabetes when diabetes is in the earlier section? The pictures in the last row for early metabolic and cardiovascular diseases are not informative-a glucometer of normal glucose 4.5mmol/L does not represent diabetes or insulin resistance.

We appreciate the reviewer’s feedback on this figure. We performed several corrections and improvements as suggested by the reviewer:

• We added a new arrow entitled “second hit” from adipose tissue dysfunction and gut dysbiosis to liver and pancreas
• Cardiovascular disease origin is both driven by the endocrine impact on cardiac cells and the “Dysfunction induced by abnormal metabolic environment”(in the figure), as discussed in section 3.4.
• In the last line, we identified metabolic diseases which are systemic (not-organ specific as MAFLD and NAFPD). We added legends to improve readability.
• The glucometer presents now 7.5 mmol/L.

 

Line 220: Please change “is” to “are”

The term “Dysfunction in adipose tissue and gut” refers to the “dysfunction” which is singular, thus the use of “is” is correct.

 

Line 249: What do the authors meant by “Following MO-offspring’s life”?

We clarified and replaced “Following” for “Later in”.

 

Lines 372: The dysregulation of the endocrine-metabolic axis should be explained e.g. what ae the factors/mechanisms contributing to it. From the authors’ write-up, it should be adipose tissue dysfunction and gut dysbiosis. Hence, Section 3.3 should come before section 3.2.

Even though we understand the reviewer’s point of view, we believe that using this order of ideas increases readability. Most of the hormones differentially released by the adipose tissue have a direct impact on the liver, thus we think it is easier for the reader to have these sections together.

Round 2

Reviewer 3 Report

The authors have made substantial revisions to the manuscript.

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

Comments to Authors: This review discussed the underlying mechanisms or dysfunction that may explain metabolic programming in offspring due to maternal obesity in early life. The format or layout of the manuscript is disorganized and confusing. The authors should consider organizing the structure of the manuscript in a clearer manner. The authors should determine the flow of the presentation of their discussion to ensure that the readers understand the points that were made/discussed. There are multiple terms that are either used inappropriately or not explained e.g. what is endocrine-metabolic axis, what is first hit and second hit, is it gut-pancreas axis instead of pancreas-gut axis. There are multiple grammatical errors throughout the manuscript and the content of the manuscript is lacking as the authors generalise findings without specific description for important points.

Title: What do the authors mean by “maternal obesity offspring”? This should be a grammatical error.

Abstract: It is unclear what the metabolic-endocrine axis mean. The authors did not provide explanation on what causes metabolic dysfunction and how endocrine function is affected. The abstract is confusing and disorganized, and does not provide an overview of the content of the manuscript.

Lines 17-18: What do the authors mean by “Obesity incidence is rising worldwide, largely contributing to the elevated prevalence of Maternal Obesity (MO)”? How can an increasing obesity incidence “contribute” to elevated prevalence? I think the authors mean “attributing” and not “contributing”.

Line 20: What modulates cellular growth and proliferation? It is unclear.

Line 23: What are the “organs”?

Introduction: The authors provide evidence that support the DOHaD hypothesis that exposure to early environment influence the health and development of offspring at later stage. In particular, the authors focus on how maternal obesity e.g. gestational weight gain may affect the offspring. The authors should also discuss about pre-pregnancy BMI. The authors did not explain what the metabolic-endocrine axis mean. The term MO-offspring that is used multiple times throughout the manuscript is grammatically incorrect. What do the authors mean by “maternal obesity-offspring”?

All the sections/subsections of the manuscript are labelled 1. This is clearly an error.

Line 55: What are the metabolic control processes?

Line 69: Please change “this” to “these”.

Lines 69-70: The authors stated that “This data highlights that, beyond genetic predisposition and postnatal environment, NCDs transmission can be intergenerationally or even transgenerationally programmed” but what ds the authors mean by intergenerationally or transgenerationally programmed? What sort of program? Genetic programming can enable intergenerational or transgenerational transmission as well. Please clarify.

Mechanistic links between MO and the development of metabolic disease in the offspring: The authors stated that metabolic programming and oxidative stress is a mechanism (line 91) but they did not provide any discussion on metabolic programming as a mechanism in this section. Metabolic programming is the alteration of metabolic state/adaptation of organ to nutritional challenge in early life and it is a scientific concept that explains the association of early nutrition (e.g. pre-pregnancy BMI, gestational weight gain and hyperglycemia in mothers) and later health outcomes in offspring. Hence, metabolic programming in this case should be the outcome and not an underlying mechanism. Metabolic programming should be included in the introduction section. The authors should consider to include some human studies other than animal studies. Most of the animal studies cited by the authors did not really show a causative effect for the proposed mechanism, they are mainly associations e.g. lines 124-130. Hence, the authors should consider to include human association studies in the discussion.

Lines 83-88: The authors only described the adverse phenotypes in offspring and did not describe the phenotype/characteristics of the mothers.

Lines 94-96: What do the authors mean by “first hit” and “second hit”? The authors need to ensure that the readers understand the use of terms within the manuscript.

Lines 96-98: What do the authors mean by “This results in multi-organ metabolic challenges consequent of the first hit specific organ’s alterations via endocrine molecules release”? This sentence is not in line with the previous sentences.

Line 99: How does MO influence fetal nutrient availability? There is no reference provided/cited. How does MO-influenced fetal nutrient availability lead to metabolic dysregulation and oxidative stress?

Adipose tissue: an endocrine organ involved in MO programming: The authors stated in the section title that adipose tissue is an endocrine organ involved in MO programming but what does this mean? The authors previously mentioned in lines 151-154 that the effect on the target tissues are a result of MO’s impact on offspring’s endocrine regulation so the effect on adipose tissue is an effect or is it involved in MO programming (please clarify).

Line 184: What do the authors mean by “metabolic-endocrine axis”?

Line 210: Figure 1 should be cited in later part of the review after the “second hit” is explained/described.

MO programming of metabolic-endocrine axis dysregulation in hepatic disease development: What do the authors mean by metabolic-endocrine axis dysregulation in hepatic disease? In this section, the authors discussed on how maternal obesity alter adipokine secretion that has an effect on hepatic diseases but there are lack of evidence to show this effect on offspring of obese mothers. The authors should remove irrelevant information not directly related to influence of maternal obesity on endocrine function that affects offspring.

Lines 278-283: Why did the authors include age-related IR?

Pancreas-gut axis in endocrine-metabolic homeostasis: Should it be gut-pancreas axis instead? Although the authors stated that the section is on pancreas-gut axis, the relationship between gut and pancreas was not clearly explained (how the gut influence the pancreas). The authors did not provide any evidence or discuss on how gut-pancreas axis influence the outcomes in offspring with obese mothers. The authors have separately discussed on gut and pancreas respectively, without associating them in the form of a connected axis. The authors should focus on maternal influence on the gut-pancreas axis and remove irrelevant information.

Relation of MO programmed metabolic dysfunction with cardiovascular disease development: This section should be part of the introduction because the section provides a general discussion on how maternal obesity will influence health (in terms of CVD risk) in offspring. This section does not provide any mechanistic insights on metabolic programming.

Conclusions: This section is confusing and did not clearly summarise the existing studies on influence of maternal obesity on metabolic programming. In particular, the “first hit” and “second hit” throughout the manuscript (even in the conclusion section) varies i.e. Figure 2 showed that the first hit is organ specific but in conclusion section (lines 451-452), the gut dysbiosis and adipose tissue dysfunction are considered second hit.

Figure 1 and Figure 2 do not align with the flow of data presentation by the authors. The authors need to re-organize the layout and structure of the manuscript. How do the mechanisms explained in lines 80-154 fit into the figures?

Author Response

Please find attached the responses to the reviewer's comments.

Author Response File: Author Response.docx

Reviewer 2 Report

This review article discusses the effects of maternal obesity (MO) on offspring. Please conduct the comments below.

1. The current report focused on the development of noncommunicable diseases (NCDs) in MO offspring. Is this a preventative measure?
2. In line 147, fetal organs and tissues adapt to an adverse intrauterine environment caused by MO, which requires a reference(s).
3. Figure 1 depicted the program well. However, it needs more legends to explain the details, such as: what is stimulatory effect or inhibitory effect?
4. The hepatokines depicted in Figure 1 will be thoroughly discussed.
5. The gut dysbiosis associated with MO offspring must be discussed in detail.
6. Cardiac dysfunction in MO offspring appears to be a mystery.
7. MO-offspring exhibit an early-aged phenotype, as shown in line 462, and how can it be identified? Please be as specific as possible.
8. Figure 2 is an excellent way to introduce the program. However, any points that are unclear (such as circulating metabolites in line 477) must be explained in the legends.

Author Response

Please find attached the responses to the reviewer's comments.

Author Response File: Author Response.docx

Reviewer 3 Report

This is a well written, interesting review that will contribute to the literature.

Author Response

Thank you for recognizing the quality of our work.

Reviewer 4 Report

This paper deals with maternal obesity and how it affects the metabolic endocrine axis in their offspring with regards to developmental metabolic disease programming.  The topic is of very high interest to the scientific community. Unfortunately, the paper is hampered by very poor English which makes it for a laborious and confusing read.

 

Furthermore the paper tends to gloss over relevant points, shows very little critical acumen regarding the material introduce and fails to address relevant points, please see below.

 

Lines 23-25 “Upon these organs’ dysregulation, the endocrine function can be dysregulated and/or programmed to release multiple hormones to overcome the metabolic disorder in an attempt to prevent or postpone organ-specific disease” The above  statement does not say anything and is redundant, please specify or give examples of the specific organs and hormones that are dysregulated

Lines 27-28 Please define what exactly is the “metabolic-endocrine axis”

Line 36 “developmental programming events of the metabolic-endocrine axis by MO,” please provide an example or two, this is the main thesis and still no definition the whole abstract suffers from being indistinct and lacking clarity!

What kind of long term morbidities are associated with MO, this should be included in the abstract?

Lines 50 -51 please provide examples of both short and long adverse term outcomes

 

Lines 54-56 “It is now accepted that maternal lifestyle before and during pregnancy influences offspring’s metabolic control processes, predisposing them to non-communicable diseases (NCDs), including obesity, type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD)6.”

 Are the above mentioned effects immediate or long term, in other words are these predispositions and there outcome manifested or present in child or adulthood or both?

Lines 80-88 please define the animal obese mother and there translational relevance.

 

Lines 408-410 “Although some of these proteins have a direct impact on cardiomyocytes’  function, others end up contributing to cardiac dysfunction by modulating the metabolic environment and nutrient quantity and quality available for the cardiac metabolism”

The above statement besides being confusing due to the English, tells us nothing! It is again an example of general non-descript information which only tires and fails to inform the reader. Please be more specific in your descriptions, i.e., what nutrients?

Are there metabolic links (if so which) and immune dysfunction tied into epigenetics?

Are they a part of the fetus´ response to MO and has it an effect on fetal weight gain?

And if so how?

These are relevant questions which this review fails to address properly, but only dances around the main issues which generalizations.

Line 423 What is an adverse metabolic profile?

Again, non-descript statements and a lack of critical assessment of the literature reviewed!

Author Response

Please find attached the responses to the reviewer's comments.

Author Response File: Author Response.docx