FEatured
April 30, 2026
How Superculture® Pet Immune delivers gut health benefits
Raphael Turcotte headshot
Raphäel Turcotte
Senior Scientific Director
We walk through the mechanism behind Superculture® Pet Immune's gut health benefits: a class of bioavailable, microbiome-derived compounds that activate a key receptor to support gut barrier function and immune response.
Delivering indoles to a dog's gut

Table of contents

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Key takeaway

Superculture® Pet Immune is the first pet nutrition ingredient designed around a specific class of bioavailable, microbiome-derived compounds, indoles. They act primarily through the aryl hydrocarbon receptor (AhR) to support gut barrier function and immune response. Four placebo-controlled clinical trials have now confirmed what the mechanistic design predicted: measurable improvements in stool quality in dogs and cats after 28 days, significant reduction in itching in dogs in 14-28 days, and favorable shifts in gut microbiome composition.

This post builds on the last two of this series, on clinical validation and ingredient development, and walks through the design rationale and mechanism behind Superculture® Pet Immune's gut health impacts.

Clinical validation in dogs and cats

In a double-blinded, placebo-controlled canine trial, healthy dogs presenting with noticeably loose stools received either Superculture® Pet Immune, delivered as a powder meal topper split across two meals, or a matched placebo over a four-week treatment period. At Day 28, dogs receiving the ingredient showed a statistically significant reduction in fecal score, indicating firmer, better-quality stools. The placebo group showed no comparable effect. Fifty percent of dogs improved in the treatment arm, compared with ten percent in placebo.

Stool quality improvement wasn't the only outcome. Superculture® Pet Immune drove a broader shift in gut microbiome composition than placebo: sixteen genus-level taxa changed in the treatment group versus one in placebo (α = 0.05), with no expansion of pathogen-associated taxa and no dysbiosis. Fecal biomarkers including pH, dry matter, IgA, calprotectin, and short-chain fatty acids all remained within healthy reference ranges at both baseline and Day 28. 

This research in dogs is detailed in Sordillo et al. (Pets, 2026).

A recently completed parallel clinical study in cats showed a comparable improvement in stool quality at Day 28.

Why we designed around indoles

So, how does this work? For Superculture® Pet Immune, the answer starts with indoles.

Indoles are a class of metabolites produced when gut microbes metabolize dietary tryptophan. Unlike many nutraceutical compounds, indoles are endogenously bioavailable: they are produced in and used by the body at concentrations that reach tissues of interest and elicit measurable biological effects. Several distinct indole compounds exert beneficial effects on the gut and also circulate systemically and thus exert beneficial effects to different organ systems such as the skin.

What made indoles a strong design target specifically for gut health is the epidemiology and mechanistic literature linking indole availability to gut health outcomes:

  • In both murine models and human clinical studies, reduced microbial production of AhR-activating tryptophan metabolites has been implicated in inflammatory bowel disease. Impaired indole ligand production exacerbates colitis susceptibility, and restoring AhR ligands is protective.
  • In dogs, altered tryptophan and indole metabolism has been characterized in acute enteropathies, chronic enteropathies, and colorectal epithelial disease, consistent with a role for this metabolite class in canine gut homeostasis.
  • Higher circulating levels of indole-3-propionic acid (IPA), a downstream indole metabolite, are associated with greater gut microbiome diversity and reduced intestinal permeability.

Taken together, the evidence pointed to indoles as a key class of microbiome-derived compounds worth delivering.

Superculture® Pet Immune delivers specific, well-characterized indoles directly, by design. This is critical, given not all indole compounds are beneficial: the gut microbiome produces a diverse range of tryptophan-derived metabolites, some with neutral or potentially adverse effects. An upstream approach, such as supplementing dietary tryptophan could not selectively direct which indoles actually get produced, leaving the outcome dependent in part on each animal's microbiome. Superculture® Pet Immune is targeted, specific, and controlled with respect to indoles.

The primary pathway: AhR

The aryl hydrocarbon receptor (AhR) is a master regulator of immune and inflammatory responses. It is recognized as an important receptor for microbiome-derived indole metabolites, with particular relevance in epithelial tissues like the gut. AhR is the central node connecting indoles to gut health outcomes, through two relevant effects:

Barrier integrity. AhR activation increases the expression of tight junction proteins, reinforcing the intestinal epithelial barrier and limiting translocation of harmful substances into the bloodstream. It also promotes IL-22 production, a cytokine critical for epithelial defense, and inhibits NF-κB and calpain activity, both of which otherwise degrade tight junction integrity. In vitro evidence further suggests AhR activation supports the differentiation of intestinal stem cells into goblet cells, which are responsible for the mucus layer that protects the epithelium.

Immune modulation. AhR activation attenuates the release of pro-inflammatory cytokines, including TNF-α and IFN-γ, two cytokines known to drive intestinal inflammation, alter gut motility through disrupted serotonin transporter function, and contribute to the pathogenesis of inflammatory bowel disease. Both are elevated in dogs with inflammatory bowel disease compared to healthy controls. AhR activation also supports the induction of regulatory T cells, which help maintain immune tolerance in the gut. Conversely, loss of AhR signaling increases susceptibility to colitis in preclinical models.

Confirming canine activation

AhR responses are species-specific, so activation data from human or murine systems should not be assumed to translate to dogs. We therefore tested Superculture® Pet Immune directly in a canine AhR luciferase reporter assay. The ingredient activated canine AhR to 56% of the positive control (methylcholanthrene) signal, confirming specific canine activation.

Downstream of AhR, we then tested cytokine modulation in a human PBMC stimulation assay. Superculture® Pet Immune significantly reduced IFN-γ release fully and TNF-α release by 35% relative to negative control at the highest concentration tested, consistent with AhR-mediated immune modulation.

Downstream indole metabolism: IPA

Beyond its direct AhR activity, Superculture® Pet Immune has a second mechanism worth highlighting: one of its main bioactives is readily converted into IPA by canine gut commensals. IPA is a well-characterized tryptophan-derived metabolite. It modulates the pregnane X receptor (PXR) pathway to support epithelial barrier function. PXR is a recognized drug target in inflammatory bowel disease. Higher IPA levels in the gut are also associated with reduced dysbiosis and endotoxin leakage.

To confirm that Superculture® Pet Immune supplies a substrate for IPA production, we cultured Clostridium sporogenes, an anaerobic gut commensal that produces IPA from tryptophan, with Superculture® Pet Immune-supplemented media versus tryptophan-matched control media. Fermentation supernatants analyzed by standard analytical chemistry methods (liquid chromatography coupled with mass spectroscopy) showed a 25-fold increase in IPA concentration in supplemented media relative to control.

Practically, IPA is not delivered in the finished ingredient, it is produced de novo by the dog's own microbiota downstream of the delivered bioactives.

Relating ingredient design to clinical outcome

Postbiotics are inherently complex ingredients, whose bioactivity is unlikely to be reducible to any single compound class. Our clinical studies measure outcomes, improved stool quality, favorable microbiome shifts, maintained fecal biomarkers, but do not isolate the specific contribution of AhR activation, PXR engagement, or any individual indole to those outcomes. Attribution at that level is inherently difficult for ingredients of this kind. The ISAPP expert consensus further notes that it is not necessary to isolate the mechanistic contribution of each individual component to a demonstrated health benefit. Our approach is therefore mechanism-centered in design and in vitro screening, but benefit-focused in clinical validation. 

  1. A bioavailable, microbiome-derived class of actives (indoles) with known systemic distribution and tissue-level activity at physiologic concentrations.
  2. A companion animal-specific mechanism, confirmed experimentally in canine cells, rather than assumed from human or rodent data.
  3. Downstream microbial conversion to IPA, a second receptor-engaging active, expanding the pharmacological footprint beyond direct AhR activation.
  4. Clinical validation of the predicted outcome, in both dogs and cats, with favorable safety and microbiome composition markers.

It's worth noting that no other postbiotic in the companion animal space, to our knowledge, has demonstrated clinical stool quality improvement at this level of rigor. Popular comparators have either not collected canine clinical data or have shown no significant effect on stool quality, with some showing worsening scores or trends toward increased pathogen abundance.

For the underlying data or the peer-reviewed manuscript once published, reach out to our team.

Acronyms

  • AhR: aryl hydrocarbon receptor
  • IFN-γ: interferon gamma
  • IgA: immunoglobulin A
  • IL-22: interleukin-22
  • IPA: indole-3-propionic acid
  • NF-κB: nuclear factor kappa B
  • PBMC: peripheral blood mononuclear cell
  • PXR: pregnane X receptor
  • TNF-α: tumor necrosis factor alpha
  • ISAPP: International Scientific Association for Probiotics and Prebiotics
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Raphael Turcotte headshot
Raphäel Turcotte
Senior Scientific Director

Previously at NYU Langone Health, Howard Hughes Medical Institute, Harvard Medical School and Massachusetts General Hospital

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