SIBO, MCAS, POTS and Food Intolerance May Be One Self-Sustaining System

For years, SIBO, MCAS, POTS, dysautonomia, food intolerance, chronic fatigue, neurological symptoms, and mitochondrial dysfunction have been treated as separate diagnoses. My work increasingly suggests that, in a subset of people, they may be different downstream expressions of the same systems-level failure: a loss of the host’s capacity to regulate epithelial metabolism, oxygen availability, microbial ecology, vascular tone, immune activation, motility, redox balance, and tissue repair.

I have encountered several people whose illnesses began with different triggers but converged on a strikingly similar pattern. One deteriorated after a fluoroquinolone antibiotic. Another developed IBS after Augmentin and then experienced the rapid onset of POTS, brain fog, fatigue, and severe malaise during a later antibiotic course. A third had previously experienced fluoroquinolone-associated nerve and tendon symptoms, partially recovered, and then developed suspected hydrogen-sulfide SIBO following food poisoning. Stress intensified the symptoms, but stress did not appear to be the original disease.

These cases do not prove every step of my Host Capacity Model. Individual cases cannot establish causation. However, they repeatedly reproduce the sequence the model predicts: a temporary insult reduces physiological reserve, the altered host environment selects a different microbial ecosystem, and that microbial ecosystem produces metabolites and inflammatory signals that further weaken the host.

Where my work began

A major scientific starting point for my work was research from Andreas Bäumler’s group at UC Davis. Their work demonstrated that antibiotic depletion of butyrate-producing organisms can reduce colonocyte PPAR-γ signaling and β-oxidation. Colonocytes then consume less oxygen, while epithelial NOS2 expression and luminal nitrate increase. Oxygen and nitrate become respiratory resources for facultative organisms such as Enterobacteriaceae.

This changed how I understood dysbiosis. The microbiome does not change only because an antibiotic killed certain bacteria. It also changes because the host begins creating a different ecological habitat.

Healthy colonocytes use butyrate as a major mitochondrial fuel. Butyrate is transported into the cell, converted to acetyl-CoA, oxidized through the TCA cycle and electron-transport chain, and used to generate ATP. This metabolism consumes substantial oxygen and helps preserve physiological hypoxia at the mucosal surface.

I use the term butyrate resistance for a working hypothesis in which butyrate may remain available, or may even be supplemented, but injured colonocytes can no longer transport, oxidize, or respond to it normally. It is not an established diagnostic term. It is a mechanistic framework I continue to investigate.

If colonocyte oxidation declines, epithelial oxygen consumption also falls. More oxygen reaches the mucosal environment, inflammatory nitrate may increase, and organisms capable of using oxygen or nitrate gain an energetic advantage. The microbes are not simply invading the intestine. The altered physiology of the host is selecting them.

A metabolically organized microbial community

In one anonymized client, the testing did not show one isolated abnormal organism. It showed a coordinated ecological network. Reported findings included major elevations of Enterobacter, Enterococcus faecium, total Pseudomonas, Streptococcus, and other organisms, together with Pseudomonas aeruginosa, Desulfovibrio piger, and a smaller elevation of Prevotella. Some reported values were approximately 55-fold above range for Enterobacter, 480-fold for E. faecium, 116-fold for total Pseudomonas, and 82-fold for Streptococcus.

I do not interpret a stool result as proof that every detected organism is active, virulent, or responsible for symptoms. Expression depends on strain, abundance, substrates, location, oxygen tension, biofilm behavior, host immunity, and the limitations of the test itself. What interested me was the metabolic architecture of the entire community.

Enterococcus and Streptococcus can generate large amounts of lactate. Desulfovibrio can use lactate, pyruvate, hydrogen, and sulfur compounds to support sulfate reduction and hydrogen-sulfide production. Instead of lactate being cross-fed into butyrate production, part of it may be redirected toward sulfur metabolism.

At physiological concentrations, hydrogen sulfide has normal signaling functions. In excess, however, it can inhibit mitochondrial respiration, disrupt epithelial metabolism, affect mucus and barrier integrity, and potentially reduce the ability of colonocytes to oxidize butyrate. The metabolite produced by the selected community can therefore worsen the host defect that originally selected the community.

Enterobacter and related facultative organisms can exploit the oxygen and inflammation-derived nitrate created when colonocyte β-oxidation declines. Their expansion also increases the potential burden of Gram-negative lipopolysaccharide, which can activate TLR4, NF-κB and host inducible nitric-oxide synthase.

Pseudomonas aeruginosa is especially interesting because it can adapt to changing oxygen conditions. It can use oxygen when available, switch to nitrate-dependent respiration under oxygen limitation, and use other survival pathways within low-oxygen biofilms. Certain strains can also produce pyocyanin, a redox-active phenazine that accepts electrons from NADH or NADPH and transfers them to oxygen, generating reactive oxygen species. Experimental epithelial studies have shown pyocyanin-associated oxidation or depletion of glutathione, disruption of cellular reducing capacity, lower ATP availability, and cellular senescence or impaired tissue repair. Most of this evidence comes from respiratory or cellular models, so a stool finding cannot prove intestinal pyocyanin production.

Prevotella, Bacteroides, and other organisms can produce succinate. In a stable ecosystem, succinate-consuming organisms convert much of this pool into downstream products such as propionate. Antibiotics may remove or suppress these consumers while leaving succinate producers or creating conditions that favor them. Succinate can then accumulate rather than being efficiently cross-fed.

Succinate is not merely microbial waste. It is also a host signaling molecule that binds SUCNR1. SUCNR1 is expressed in several epithelial and immune compartments, including human mast cells. Research involving succinate-containing medications in NSAID-exacerbated respiratory disease has raised the possibility that high succinate exposure can stimulate SUCNR1-associated mast-cell reactions. This does not prove that microbial succinate causes MCAS, but it provides a plausible pathway through which impaired succinate clearance may amplify mast-cell reactivity in susceptible people.

This may be one reason MCAS sometimes appears downstream of intestinal injury. Succinate signaling, LPS exposure, barrier disruption, altered vagal regulation, catecholamine surges, oxidative stress, and microbial translocation may collectively lower the threshold for mast-cell activation. Mast-cell mediators then increase vasodilation and vascular permeability, worsening effective circulating volume, venous return, orthostatic intolerance, and sympathetic compensation. POTS and MCAS can begin reinforcing one another.

The DNA-damage and NAD⁺ collapse

Another major direction in my research is the connection between microbial oxidative stress, DNA damage, PARP-1, CD38, sirtuins, and mitochondrial failure.

One anonymized client with markedly elevated total Pseudomonas also had a transferrin saturation of 49 percent. Transferrin saturation is not the same as free catalytic iron, so this value does not prove that a Fenton reaction was occurring. However, combined with depleted glutathione and evidence of high oxidative stress, it made iron-dependent oxidative chemistry an important mechanism to investigate.

Pyocyanin can generate superoxide and hydrogen peroxide through redox cycling. When hydrogen peroxide encounters available ferrous iron, it can generate highly reactive hydroxyl radicals through Fenton chemistry. Hydroxyl radicals can damage lipids, proteins, mitochondrial DNA, and nuclear DNA.

DNA strand breaks strongly activate PARP-1. PARP-1 uses NAD⁺ to construct poly-ADP-ribose chains during DNA-damage signaling. Controlled PARP-1 activity is essential for repair. Persistent activation, however, can become a major NAD⁺ sink.

This is not only theoretical. Experimental colitis and human ulcerative-colitis tissue have demonstrated epithelial NAD⁺ depletion, increased PARP-1 expression and activity, reduced SIRT1-PGC-1α signaling, mitochondrial dysfunction, and impaired barrier health. Restoring NAD⁺ improved mitochondrial function in experimental models, but required an intact epithelial PGC-1α pathway.

The resulting sequence may be self-reinforcing. Microbial and immune-derived oxidative stress damages DNA. PARP-1 becomes persistently activated. NAD⁺ declines. SIRT1 loses the NAD⁺ required to activate PGC-1α. Mitochondrial biogenesis, respiratory capacity, antioxidant defense, and epithelial repair decline. Colonocytes become less able to oxidize butyrate and consume oxygen. The ecological habitat shifts further toward facultative and inflammation-adapted organisms.

CD38 may deepen the same problem. CD38 is another major NAD-consuming enzyme that can increase during inflammation and aging. Experimental research has connected CD38-driven NAD⁺ decline with mitochondrial dysfunction through reduced SIRT3 activity. More recent colonic-mucositis work links the CD38–NAD⁺ axis with oxidative injury, crypt disruption, tight-junction loss, PARP activation, and impaired epithelial architecture.

This produces a possible combined NAD⁺ drain: PARP-1 consumes NAD⁺ in response to DNA damage, while inflammatory CD38 consumes NAD⁺ through a separate pathway. Reduced NAD⁺ then suppresses sirtuins, especially SIRT1 and SIRT3, weakening mitochondrial biogenesis, antioxidant control, respiratory enzymes, mitophagy, and cellular repair.

There is a second Pseudomonas connection. P. aeruginosa does not produce human PARP-1, but some of its virulence proteins are bacterial ADP-ribosyltransferases. Exotoxin A transfers ADP-ribose from NAD⁺ onto elongation factor 2, disrupting host protein synthesis. ExoS and ExoT also possess ADP-ribosyltransferase domains that modify host proteins and disturb cytoskeletal and signaling architecture. Stool abundance does not prove expression, secretion, epithelial delivery, or clinically meaningful NAD⁺ consumption by these toxins. But if a virulent strain were actively expressing and delivering them, host PARP activation and bacterial ADP-ribosylation could place pressure on the same NAD⁺-dependent cellular system through different mechanisms.

This creates what I consider a possible bioenergetic “triple lock.” Pyocyanin and inflammatory oxidants may damage aconitase and other iron–sulfur-dependent enzymes near the beginning of mitochondrial metabolism. PARP-1 and CD38 may drain NAD⁺ in the middle of the system. Excess hydrogen sulfide may inhibit cytochrome-c oxidase at the terminal respiratory step. The cell can then become restricted at substrate processing, redox transfer, and final electron acceptance simultaneously.

Butyrate resistance, the Warburg-like shift and oxidative worsening

Healthy differentiated colonocytes rely heavily on oxidative metabolism. Cancerous colonocytes frequently shift toward glucose utilization through the Warburg effect and oxidize less butyrate. In that established cancer model, unoxidized butyrate accumulates and acts more strongly as an HDAC inhibitor, suppressing proliferation and promoting apoptosis.

I am investigating whether chronically injured but noncancerous colonocytes can enter a partial Warburg-like or glycolytic state. This is a hypothesis, not an established mechanism in SIBO, MCAS or POTS.

If an injured colonocyte increasingly relies on glycolysis because NAD⁺ is depleted, respiratory complexes are impaired, glutathione is low, and iron–sulfur enzymes are damaged, butyrate may no longer behave simply as a beneficial fuel. It may accumulate, alter gene expression, increase metabolic pressure, or intensify oxidative stress in a cell that lacks the capacity to process it.

This may explain a paradox I repeatedly observe: some clients improve with butyrate, whereas others become substantially worse.

The difference may not be the butyrate itself. It may be the metabolic state of the cell receiving it.

More oxidative stress can damage iron–sulfur clusters, further restrict TCA-cycle and respiratory function, lower butyrate oxidation again, and preserve epithelial oxygen leakage. The attempted treatment can then expose the underlying metabolic block rather than correct it.

Secretory IgA, MMPs, senescence and failed epithelial renewal

Across client testing, I have also repeatedly seen elevated secretory IgA and elevated matrix metalloproteinase markers, including findings reported on Gut Zoomer testing. I do not consider these commercial test values proof by themselves, but the repeating pattern is important.

Elevated secretory IgA does not always mean “strong immunity.” It may indicate active mucosal recognition and containment of an antigenic microbial community. Research using IgA sequencing has shown that highly IgA-coated organisms can identify inflammatory or colitogenic members of the microbiome.

Matrix metalloproteinases are required for normal remodeling, but persistent elevation can become destructive. MMP-9 has been shown experimentally to increase intestinal tight-junction permeability through NF-κB and MLCK signaling and to worsen barrier dysfunction in colitis models.

This suggests that the epithelial problem is not adequately described as “leaky gut.” It may include continuous immune recognition, matrix degradation, failed restitution, mitochondrial injury, DNA damage, and altered epithelial-cell fate.

I am investigating whether some chronically injured colonocytes or epithelial progenitor cells enter a senescence-like state. Cellular senescence initially protects the organism by arresting damaged cells that might otherwise replicate unstable DNA and become malignant. But senescent cells can remain metabolically active and release inflammatory cytokines, chemokines, growth factors, and MMPs through a senescence-associated secretory phenotype.

The initial arrest may reduce cancer risk, but failure to clear or replace these cells could leave a metabolically weak and inflammatory epithelial surface that cannot maintain barrier integrity, butyrate oxidation, physiological hypoxia, or normal microbial selection. Experimental intestinal work connects mitochondrial disruption with epithelial senescence, impaired differentiation, and barrier injury, while mitochondrial respiration is also required for normal intestinal stem-cell proliferation and lineage development.

The stem-cell niche may therefore be central to recovery. Killing organisms does not automatically regenerate a metabolically competent epithelial surface. The crypt must produce new cells capable of differentiating, building mitochondria, oxidizing butyrate, maintaining brush-border enzymes, producing mucus, and re-establishing epithelial hypoxia.

Why host genetics changes recovery

The same antibiotic, food poisoning episode, viral illness, or physiological stress does not produce the same outcome in everyone. Host genetics may influence connective-tissue integrity, vascular compliance, autonomic reserve, mitochondrial enzymes, antioxidant defense, NAD⁺ metabolism, immune thresholds, histamine handling, sulfur processing, drug metabolism, epithelial glycosylation, and microbial attachment.

Large human studies show that host genetic variation has measurable associations with microbiome composition, although environment and diet remain major determinants. Recent experimental work also suggests that host genotype can alter microbiome recovery after antibiotics. Recovery additionally depends on baseline community structure, diet, microbial reservoirs, and repeated exposures.

Genes are not destiny. They may determine how much reserve a person begins with, which pathway fails first, and how efficiently the system reconstructs itself after injury.

Why killing the microbes may not be enough

The dysbiosis is real, and targeted antimicrobial treatment may sometimes be necessary. But treatment frequently begins too far downstream.

Killing Desulfovibrio does not necessarily correct the lactate and sulfur environment that selected it. Killing Enterobacter does not necessarily remove oxygen and nitrate. Killing Pseudomonas does not automatically restore glutathione, NAD⁺, sirtuin activity, intestinal alkaline phosphatase, mitochondrial respiration, stem-cell renewal, or epithelial hypoxia. Reducing succinate-producing organisms does not necessarily restore the organisms and host pathways that normally consume succinate.

If the host continues supplying oxygen, nitrate, lactate, sulfur substrates, damaged mucus, inflammatory signals, altered bile acids, impaired motility, and poorly absorbed nutrients, another organism capable of exploiting the same ecological niche may replace the one that was eliminated.

This is the central principle of my Host Capacity Model. A temporary insult can reduce the host’s physiological capacity. That loss changes the intestinal habitat. The changed habitat selects a metabolically coordinated microbial community. That community produces hydrogen sulfide, LPS, lactate, succinate, reactive oxygen species, nitric oxide, peroxynitrite, biogenic amines, ammonia-related products, and potentially redox-active toxins. These pressures can damage DNA, activate PARP-1 and CD38, consume NAD⁺, suppress sirtuins, impair mitochondria, weaken stem-cell renewal, increase MMP activity, disrupt the barrier, and reduce butyrate oxidation even further.

The host and microbiome then begin sustaining one another in the wrong physiological state.

This may be why SIBO, MCAS, POTS, food intolerance, neurological dysfunction, exercise intolerance, and mitochondrial impairment so often appear together. They may not always represent multiple unrelated diseases. They may be different visible manifestations of one injured host–microbial ecosystem.

The deepest question is therefore not only which organism should be killed. It is what physiological capacity was lost after the initial insult, why colonocytes stopped oxidizing butyrate, why oxygen and nitrate became available, why lactate and succinate were no longer efficiently cross-fed, why NAD⁺ was depleted, why the epithelial stem-cell niche failed to restore the surface, and why host genetics allowed the process to persist in one person but not another.

The antibiotic, infection, food poisoning, or other insult may have initiated the process.

The illness continues because the host has lost the capacity to restore and defend the biological environment required for recovery.

That is the work I continue to investigate.