Rethinking Heat Stress:

THE GUT MAY BE PART OF THE EQUATION.

Heat stress is more than a fluid-balance problem. Human research has documented gastrointestinal disturbances, intestinal barrier dysfunction and systemic consequences associated with severe thermal and exertional stress.

ProBaxtra's research foundation begins with a different question: what role does gut function play in the body's response to heat stress—and can supporting the gut before heat exposure influence that response?

Explore the Science


Peer-Reviewed Research

SCIENTIFIC RESEARCH FOUNDATION

INVESTIGATING THE GUT’S ROLE IN HEAT STRESS


THE RESEARCH FOUNDATION

ProBaxtra’s scientific foundation begins with research examining the relationship between the gut, heat stress and Bacillus subtilis.

Foundational research investigated Bacillus subtilis strain BSB3 in experimental animal models of heat stress. Subsequent studies expanded this investigation into intestinal integrity, systemic responses and exercise-related physiological stress.

Together, these studies provide a preclinical foundation for investigating how BSB3 pretreatment influenced measurable physiological responses to heat and exercise-related stress. These findings were observed in animal models and do not establish human clinical efficacy.

Human Evidence

HUMAN & HEAT-STRESS EVIDENCE

HEAT STRESS CAN INVOLVE THE GUT

Severe heat stress is not simply an elevation in body temperature. Human heat-stress literature has documented gastrointestinal disturbances, intestinal barrier dysfunction and systemic consequences associated with severe thermal stress.

Research has described gastrointestinal ischemia, intestinal barrier disruption, endotoxemia and other systemic consequences associated with severe thermal and exercise stress.

Human evidence helps establish the biological problem. Experimental animal research provides a controlled way to investigate potential mechanisms and interventions. These bodies of evidence are related, but they are not interchangeable.

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Severe Heat / Exercise Stress

02

Reduced GI Blood Flow

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Gastrointestinal Stress

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Intestinal Barrier Disruption

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Microbial Translocation / Endotoxemia

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Systemic Response

Direct Human / Exertional Heat-Stress Evidence

Human research and reviews of exertional heat stress have documented gastrointestinal disturbances, intestinal barrier dysfunction and systemic consequences associated with severe thermal stress.

Human Problem → Experimental Model → Human Research Question

Animal findings cannot automatically be assumed to apply to humans. They provide a framework for designing translational research.

Experimental Research

Animal models allow researchers to investigate specific mechanisms and potential interventions under controlled conditions.

SELECTED HUMAN & HEAT-STRESS REFERENCES

DIRECT HUMAN HEAT-STRESS EVIDENCE

JAMA · 1971

Fatal Heat Stroke: Circulating Endotoxin and Gram-Negative Sepsis as Complications

Graber, C. D., Reinhold, R. B., Breman, J. G., Harley, R. A., & Hennigar, G. R. (1971). Fatal Heat Stroke: Circulating Endotoxin and Gram-Negative Sepsis as Complications. JAMA.

Historical human evidence describing circulating endotoxin and systemic complications associated with fatal heat stroke.

View PubMed · View JAMA

Nutrients · 2020

The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures

Ogden et al. (2020). The Gastrointestinal Exertional Heat Stroke Paradigm. Nutrients.

Reviews the relationship between exertional heat stroke, gastrointestinal dysfunction, intestinal barrier integrity and systemic consequences.

View PubMed · View Full Text

BROADER HUMAN EXERCISE & GI EVIDENCE

Alimentary Pharmacology & Therapeutics · 2017

Systematic Review: Exercise-Induced Gastrointestinal Syndrome

Costa, R. J. S., Snipe, R. M. J., Kitic, C. M., & Gibson, P. R. (2017). Systematic review: exercise-induced gastrointestinal syndrome—implications for health and intestinal disease. Alimentary Pharmacology & Therapeutics.

Reviews exercise-associated gastrointestinal injury, intestinal permeability and endotoxemia, providing broader context for understanding gastrointestinal responses to physiological stress.

View PubMed · View Article

GI BARRIER & HEAT-STRESS MECHANISTIC CONTEXT

Journal of Animal Science · 2009

Stress-Induced Gastrointestinal Barrier Dysfunction and Its Inflammatory Effects

Lambert, G. P. (2009). Stress-induced gastrointestinal barrier dysfunction and its inflammatory effects. Journal of Animal Science, 87(suppl_14), E101–E108.

Reviews stress-induced gastrointestinal barrier dysfunction and inflammatory consequences, including mechanisms relevant to severe exercise and heat stress. Broader mechanistic context — not a direct human heat-stroke clinical study.

View PubMed · View Article

THE HUMAN LITERATURE ESTABLISHES THE PROBLEM.
THE PRECLINICAL BSB3 RESEARCH RAISES THE QUESTION.

The next step is human translation: determining whether relevant effects observed in preclinical BSB3 research can be meaningfully evaluated under controlled human heat-stress conditions.


The Science of Strain Identity

WHY STRAIN MATTERS

BACILLUS SUBTILIS IS A SPECIES — NOT A SINGLE STRAIN

Bacillus subtilis describes a species—not a single uniform strain. Different strains can have different genetic and biological characteristics. Research conducted with one strain should therefore not automatically be generalized to another. The foundational research discussed on this site specifically investigated Bacillus subtilis strain BSB3. That is why strain identity matters when evaluating probiotic research.

PRTA300™

FROM RESEARCH STRAIN TO PROBAXTRA

PRTA300™ is the proprietary commercial designation used by ProBaxtra for the Bacillus subtilis strain associated with the foundational BSB3 research. ProBaxtra maintains documentation establishing the lineage and identity relationship between the strain identified in the foundational research as BSB3 and the strain designated PRTA300™. The PRTA300™ designation was adopted for commercial and trademark purposes.

01

BSB3 — Foundational Research Designation

02

PRTA300™ — ProBaxtra Commercial Designation

SAME STRAIN LINEAGE

THE QUESTION IS NOT SIMPLY "DOES IT CONTAIN BACILLUS SUBTILIS?"

The more important question is: Which strain? And: What research supports that specific strain? Because probiotic effects can be strain-specific, research involving one Bacillus subtilis strain should not automatically be attributed to another.

01

Foundational Research — Bacillus subtilis BSB3

02

Documented Strain Lineage — Research strain → ProBaxtra strain

03

ProBaxtra — PRTA300™

04

Current Research Question — Can the effects observed in the foundational BSB3 research be demonstrated in appropriately designed human studies?

Mechanism 1

GUT BARRIER & MICROBIAL TRANSLOCATION

WHEN HEAT STRESS CHALLENGES THE GUT — AND BSB3 SHOWED PROTECTIVE EFFECTS IN ANIMAL MODELS

Experimental research investigated whether oral administration of Bacillus subtilis BSB3 before heat stress could protect the intestine from the harmful effects of thermal stress.

In heat-stressed rats that did not receive BSB3, researchers observed intestinal structural changes, disruption of intestinal integrity, bacterial translocation and increased circulating LPS-related responses.

In contrast, rats pretreated with BSB3 showed preservation of intestinal structure and mucosal integrity, reduced bacterial translocation and reduced LPS-related responses.

A subsequent study reported that BSB3 protected the intestine from harmful effects associated with experimental heat stress, including preservation of intestinal villi and mucosal thickness.

Together, these findings provide preclinical evidence that BSB3 pretreatment was associated with protection of the intestine during experimental heat stress.

These findings were observed in animal models and do not establish human clinical efficacy. The important next question is whether comparable protective effects can be demonstrated in humans under controlled heat-stress conditions.

WHAT THE RESEARCH FOUND

BSB3-Pretreated Animals

Rats pretreated with BSB3 before experimental heat stress showed preservation of intestinal structure and mucosal integrity, along with reduced bacterial translocation and reduced LPS-related responses compared with heat-stressed animals that did not receive BSB3.

WHAT HAPPENED WITHOUT BSB3

Heat-Stressed Animals

Heat-stressed animals that did not receive BSB3 showed intestinal structural changes, impaired intestinal integrity, bacterial translocation and increased LPS-related responses.

01

Heat Stress

02

Gut Barrier Challenge

03

Without BSB3 — Intestinal Damage · Bacterial Translocation · Increased LPS-Related Response

04

With BSB3 Pretreatment — Preserved Intestinal Structure · Preserved Mucosal Integrity · Reduced Bacterial Translocation · Reduced LPS-Related Response

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Protective Effect Observed in the Animal Model

06

Human Research Needed

Mechanism 2

HEAT STRESS & IMMUNE RESPONSE

WHEN THERMAL STRESS AFFECTS IMMUNE SIGNALING — AND BSB3 MODULATED THE RESPONSE

Heat stress can alter inflammatory and immunoregulatory signaling throughout the body.

In the BSB3 heat-stress research, investigators measured several cytokines and other biological responses following experimental heat exposure.

In rats pretreated with BSB3 before heat stress, the researchers found no heat-stress-associated increase in IL-10. In contrast, IL-10 was significantly elevated in heat-stressed rats that received PBS rather than BSB3.

The researchers also found that BSB3 pretreatment prevented the heat-stress-associated increase in circulating LPS, with LPS levels in BSB3-pretreated animals remaining similar to control animals.

Importantly, the study did not report heat-stress-related changes in IL-1β, IL-6, TNF-α or IFN-γ. The observed cytokine finding was specifically related to IL-10.

Together, these findings provide experimental evidence that BSB3 pretreatment influenced measurable biological responses associated with heat stress in rats.

These findings are preclinical and do not establish that BSB3 produces the same effects in humans. Controlled human research is needed to determine whether these observations translate to people.

WHAT BSB3 PRETREATMENT SHOWED

MODULATED RESPONSE OBSERVED

BSB3 pretreatment prevented the heat-stress-associated increase in IL-10. BSB3 pretreatment also prevented the rise in circulating LPS observed after heat stress, with levels remaining similar to control animals.

WHAT REMAINS TO BE TESTED

Human Response

Whether BSB3 can produce comparable effects on measurable immune, inflammatory or systemic responses during controlled heat stress in humans remains an important research question.

01

Heat Stress

02

Immune / Systemic Response

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BSB3 Pretreatment

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IL-10 Increase Prevented

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LPS Increase Prevented

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Measured Response Remained Similar to Controls

07

Human Research Needed

Mechanism 3

HEAT STRESS & ERYTHROCYTE VESICULATION

HEAT STRESS & ERYTHROCYTE VESICULATION — BSB3 PRETREATMENT PREVENTED THE INCREASE

Research by Moore and colleagues investigated erythrocyte vesiculation as a measurable response to thermal stress and examined whether BSB3 pretreatment influenced this response.

Heat exposure produced a significant increase in free erythrocyte vesicles in rats pretreated with PBS. In the BSB3-pretreated rats, however, no increase in the number of free vesicles was observed following heat exposure.

The 2014 study similarly reported increased erythrocyte vesiculation among heat-stressed rats that were not protected with BSB3, while the measured parameters in BSB3-pretreated heat-stressed rats remained similar to control groups.

These findings provide experimental evidence that BSB3 pretreatment was associated with prevention of the heat-stress-related increase in erythrocyte vesiculation in the rat model.

These findings are preclinical and do not establish the same effect in humans. Controlled human research is needed to determine whether this response can be demonstrated in people.

01

Normal Temperature — Erythrocyte Stability

02

Heat Stress — Thermal Challenge

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Without BSB3 — Increased Erythrocyte Vesiculation

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With BSB3 Pretreatment — Increase in Vesiculation Prevented

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Research Finding — BSB3 Pretreatment Prevented the Heat-Stress-Associated Increase in the Animal Model

WHAT THE RESEARCH FOUND

BSB3-Pretreated Animals

Following heat exposure, BSB3-pretreated rats showed no increase in the number of free erythrocyte vesicles.

WHAT HAPPENED WITHOUT BSB3

PBS-Pretreated Animals

Heat exposure produced a significant increase in free erythrocyte vesicles in PBS-pretreated rats. In the 2016 study, free vesicles increased from approximately 1.4 × 10⁶ to 3.8 × 10⁶ vesicles/µL.

Normal Erythrocytes

Smooth biconcave discs with stable membrane architecture under normal temperature conditions.

Without BSB3 — Heat-Stress Response

Heat exposure produced a significant increase in free erythrocyte vesicles. In the 2016 study, free vesicles increased from approximately 1.4 × 10⁶ to 3.8 × 10⁶ vesicles/µL in PBS-pretreated rats.

With BSB3 Pretreatment

BSB3 pretreatment prevented the heat-stress-associated increase in erythrocyte vesiculation. No increase in free vesicles was observed in BSB3-pretreated rats following heat exposure.

Research Direction

FROM PRECLINICAL RESEARCH TO HUMAN INVESTIGATION

THE NEXT STEP IS TRANSLATIONAL RESEARCH

The existing research provides a foundation for an important translational question: Can the effects observed in experimental models be demonstrated in humans exposed to controlled exertional or environmental heat stress? ProBaxtra is interested in working with qualified researchers to determine the appropriate study design, study population, duration, measurable endpoints and experimental conditions needed to investigate that question.

01

Preclinical Research — Animal models

02

Human Heat-Stress Evidence — Documented physiological and gastrointestinal consequences

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Translational Research Question — Can the effects observed in the BSB3 animal research be demonstrated in humans under controlled heat-stress conditions?

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Controlled Human Investigation — Appropriate study design + measurable endpoints

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Data — Let the evidence determine the outcome

"We don't want to design a study intended to prove our product works. We want to design a study capable of telling us whether it works."

WHAT WE ARE LOOKING FOR

Study Design

Help determine the appropriate human research model and experimental conditions.

Measurable Endpoints

Identify objective physiological, gastrointestinal and biochemical endpoints that can meaningfully evaluate the research question.

Scientific Interpretation

Help determine whether findings observed in experimental models can be meaningfully evaluated and interpreted in humans.

Peer-Reviewed Science

Academic References & Original Research

FOUNDATIONAL BSB3 RESEARCH

Ph.D. Dissertation · Auburn University · 2013

Novel Approach for Assessment and Mitigation of Heat-Stress Effects

Moore, T. (2013). Novel Approach for Assessment and Mitigation of Heat-Stress Effects. Ph.D. Dissertation, Auburn University.

Doctoral research investigating heat stress, gut microflora, probiotics and physiological responses to thermal stress.

Auburn University Research Record · Full Dissertation PDF

Microscopy Research and Technique · 2013

Erythrocyte Vesiculation Under Thermal Stress

Moore, T., Sorokulova, I., Pustovyy, O., Globa, L., Pascoe, D. D., & Vodyanoy, V. (2013). Microscopic evaluation of vesicles shed by erythrocytes at elevated temperatures. Microscopy Research and Technique, 76(11), 1116–1123.

Identifies erythrocyte vesiculation as a measurable biological response to thermal stress and provides mechanistic context for subsequent BSB3 heat-stress research.

View on Pubmed

Journal of Applied Microbiology · 2014

BSB3 & Heat Stress

Moore, T., Globa, L., Pustovyy, O., Vodyanoy, V., & Sorokulova, I. (2014). Oral administration of Bacillus subtilis strain BSB3 can prevent heat stress‐related adverse effects in rats. Journal of Applied Microbiology, 117(5), 1463–1471. DOI: 10.1111/jam.12606

Experimental animal research investigating BSB3 in a heat-stress model.

View on PubMed

Journal of Visualized Experiments · 2016

BSB3 & Heat-Stress Model

Sorokulova, I., Globa, L., Pustovyy, O., & Vodyanoy, V. (2016). Prevention of Heat Stress Adverse Effects in Rats by Bacillus subtilis Strain. Journal of Visualized Experiments, Issue 113. DOI: 10.3791/54122

Provides a detailed experimental model for investigating BSB3 under heat-stress conditions.

View on PubMed · Full Text / PMC

Journal of Applied Microbiology · 2020

BSB3 & Exercise-Induced Stress

Ducray et al. (2020). Prevention of excessive exercise-induced adverse effects in rats with Bacillus subtilis BSB3. Journal of Applied Microbiology, 128(4), 1163–1178. DOI: 10.1111/jam.14544

Experimental animal research investigating BSB3 in a model of excessive exercise-induced physiological stress, extending the preclinical research beyond environmental heat exposure and toward exercise-related physiological stress.

View on PubMed · Full Text / PMC

BROADER BACILLUS & ENVIRONMENTAL-STRESS RESEARCH

This section includes peer-reviewed research that expands the scientific context surrounding Bacillus subtilis, gut function, exercise, heat stress and other environmental stressors. Some studies involve strains other than BSB3. These studies are included for scientific context and should not be interpreted as evidence specific to BSB3 or PRTA300™.

Peer-Reviewed Review

The Gastrointestinal Exertional Heat Stroke Paradigm

A peer-reviewed review discussing the relationship between exertional heat stress, gastrointestinal injury, barrier disruption and systemic consequences.

Broader scientific context for the gut's role during exertional heat stress.

01

Foundational BSB3 Research

Heat Stress · Exercise-Induced Stress

02

Human & Broader Heat-Stress Evidence

Human Heat Stress · GI Injury · Barrier Function · Systemic Responses

03

Broader Scientific Context

Other Bacillus Strains · Gut–Lung Axis · Environmental Stress

04

Next Question

Can comparable effects observed in the foundational BSB3 research be demonstrated in humans?